Food Supplementation with Vitamins and Minerals: An Overview

*Myriam El Ati-Hellal and Fayçal Hellal*

## **Abstract**

Vitamins are organic substances that are essential for normal metabolism, growth, development, and regulation of cell function. Mineral elements are non-organic substances. They constitute 4% of the body mass. Multivitamins and minerals are commonly used as dietary supplements to maintain good health and prevent chronic diseases. In this chapter, we described selected vitamins and minerals used as nutritional supplements. We presented their dietary sources as well as their absorption, metabolism, storage and functions in human body. We also discussed their benefits and potential harmful effects associated with deficiency or excess intake. The prevalence, recommended intakes, regulatory status and health effects of supplementation with these micronutrients were also detailed. Finally, the use of vitamins and minerals as food additives was described in this chapter.

**Keywords:** vitamins, minerals, dietary sources, bioavailability, recommended intakes

### **1. Introduction**

According to the US Food and Drug Administration (FDA), a dietary supplement is a product taken by mouth that contains a "dietary ingredient" intended to supplement the diet [1]. The use of dietary supplements is widespread in the United States, Canada as well as in several European countries [2–5]. Up to 50% of adults and one-third of children in economically advanced economies consume these supplements [6]. Dietary supplements may be used to correct deficiencies or maintain adequate intake of some nutrients. However, they may be harmful with excess intake. Hence, it is necessary to control their levels for a safe intake [7–9]. Vitamins and minerals are the most frequently used dietary supplements among adults in United States [10]. Thirteen vitamins (A, B1, B2, B3, B5, B6, B8, B9, B12, C, D, E, K) and fifteen minerals (calcium, phosphorus, potassium, sodium, chloride, magnesium, iron, zinc, iodine, chromium, copper, fluoride, molybdenum, manganese, and selenium) have been recognized as essential for the maintenance of human health [11]. The first multivitamin/mineral (MVM) formulas was introduced in the 1930s and the most common definition of this term is a dietary supplement containing 3 or more vitamins and minerals [12]. MVM supplements are recommended to prevent or treat nutrition-related infectious diseases such as the Acquired Immune Deficiency Syndrome (AIDS) disease that arises from human immunodeficiency virus (HIV) infection and which is responsible for more than half of total deaths in

some developing countries [13]. Tuberculosis is another chronic infectious disease that is correlated to the presence of vitamin A levels in human bodies. Indeed several epidemiological studies found that healthy population has significantly higher vitamin A serum levels than tuberculosis patients [14, 15]. MVM supplements are also widely used to promote health and prevent chronic diseases and cancer. However, controversial findings were reported on the beneficial effect of these supplements on cardiovascular diseases prevention [16–18]. The aim of this chapter was to give a global idea on the main vitamins and minerals that are essential in our life and to present the most important users of MVM supplements as well as their frequency of use and the related deficiency diseases.

## **2. Vitamins**

Vitamins are organic molecules that are necessary for the organism and which humans cannot synthesize in a sufficient quantity. Unlike habitual nutrients that are introduced in large quantities in the body and that contribute to the production of energy, only small amounts of vitamins are required for a healthy metabolism (micrograms or milligrams per day). Vitamins are obtained naturally from a balanced and diversified diet or can be added to foods. Their deficiency can cause health disorders such as cardiovascular diseases or cancers while an overconsumption can lead to toxic effects in the medium or long term (**Table 1**) [1–5].



*Food Supplementation with Vitamins and Minerals: An Overview DOI: http://dx.doi.org/10.5772/intechopen.98287*

#### **Table 1.**

*Deficiency and toxic effects of selected vitamins.*

Thirteen vitamins were discovered during the first half of the twentieth century and the last discovery was that of vitamin B12 in 1948. These compounds have diverse biochemical functions such as antioxidants, coenzymes, hormones or mediators of cell signaling. They are classified in two categories: fat-soluble (e.g. vitamins A and D) and water-soluble (e.g. vitamins B and C). While water-soluble vitamins should be consumed daily, fat-soluble vitamins can be consumed at less regular intervals due to their ability to be stored in the liver and in adipose tissue [1, 2, 6]. Among the thirteen known vitamins, six water-soluble and three fat-soluble ones were described, due to their high nutritive value and their frequent use as food supplements and nutritional additives.

#### **2.1 Vitamin A**

Vitamin A is a fat-soluble vitamin discovered in the early 1900s by McCollum and independently by Osborne and Mendel as an essential dietary factor for growth [2, 7]. Forms of vitamin A include provitamin A carotenoids (principally β-carotene, α-carotene, and β-cryptoxanthin), retinol (preformed vitamin A), retinal, retinoic acid and retinyl esters. The requirements for vitamin A are expressed in retinol activity equivalents (RAEs), such that 1 μg RAE = 1 μg performed retinol = 12 μg β-carotene = 24 μg α-carotene or β-cryptoxanthin [8, 9].

#### *2.1.1 Dietary sources*

Preformed vitamin A is found naturally only in animal-based products such as liver and fish liver oil, dairy products, eggs and fish. It is also used in food

fortification of sugar, cereals, fats or condiments. The main dietary sources of provitamin A carotenoids are pigmented vegetables and fruits including spinach, parsley, amaranth, lettuce, carrot, papaya, mango, etc. [1, 9, 10].

#### *2.1.2 Absorption, metabolism and storage*

About 70-90% of preformed vitamin A is absorbed from the small intestine dissolved in lipid micelles. Carotenoids are absorbed into the small intestine by passive diffusion. Their biological availability varies between 5 and 60% [8].

After absorption, retinal esters and nonhydrolyzed carotenoids are transported to the liver in chylomicrons and chylomicron remnants. About 90% of retinol is stored in the liver as retinol palmitate. The remaining fraction is transported to other adipose tissues by Retinol Binding Protein (RBP). The total body vitamin A is excreted in the urine or the feces and to a lesser extent in the bile [1, 9, 11].

## *2.1.3 Function*

Vitamin A is required for normal vision, embryonic development, reproduction, gene expression, growth and immune function [7, 9]. In the visual system, the dim-light vision is related to the presence of rhodopsin, a photosensitive pigment formed in rod cells, after the binding of the 11-*cis*-retinaldehyde to the optin protein. Following an equivalent mechanism, the vision of shapes and colors is carried out in the presence of iodopsin pigments formed in the cones after the binding of the 11-*cis*-retinaldehyde to the photopsin protein [4, 10, 11]. As regards embryonic development, retinoic acid as well as endogenous retinoids play an important role in the anterior–posterior development of the central body axis and in limb development. Their concentrations are highly regulated, both spatially and temporally [3]. Vitamin A is essential for reproduction too, through the biosynthesis of glycoproteins specific to spermatogenesis [4, 11]. It is also required to regulate the expression of a number of genes through interactions of retinoic acid with various cytosolic and nuclear receptors [11, 12]. These genes include the growth hormone gene, and therefore the normal growth and development of children are affected by vitamin A deficiency. Finally, vitamin A enhances cellular and humoral immunity through all-trans-retinoic acid. It stimulates the synthesis of immunoglobulins and the proliferation of lymphocytes and thymocytes [4, 11].

## **2.2 Vitamin B1 (thiamin)**

Historically, vitamin B1 has been known as the preventive and curative agent of the human disease "beriberi" [2, 7]. Its structure determination and synthesis were carried out in 1936. This water-soluble vitamin includes substituted pyrimidine and thiazole moieties linked by a methylene bridge. Three phosphorylated forms of thiamin occur in nature: thiamin monophosphate, thiamin diphosphate (the active coenzyme also known as thiamin pyrophosphate) and thiamin triphosphate. Thiamin is particularly sensitive to sulfites and polyphenols, which destroy its biological activity [8].

#### *2.2.1 Dietary sources*

The most abundant *sources* of vitamin B1 include yeast and yeast extract, whole cereal grains, nuts, lean pork, wheat bran, heart, kidney, liver and fortified food such as bread and breakfast cereals. Fresh food, such as fruits, vegetables and dairy products except butter, could protect against vitamin B1 deficiency if it is consumed regularly and in sufficient amount [1, 3, 7].

## *2.2.2 Absorption, metabolism and storage*

Dietary thiamin phosphates are hydrolyzed to free thiamin by intestinal phosphatases. Then, absorption of free thiamin takes place in the duodenum and proximal jejunum [3, 4]. Two parallel mechanisms are involved in thiamin absorption: a saturable active transport at low physiological concentrations of the vitamin and a passive diffusion at higher concentrations [3, 7, 9]. Transport of thiamin is modulated by various biological factors such as age, diabetic state and alcohol exposure [7]. Some thiamin is phosphorylated to thiamin monophosphate in the intestinal mucosa and both free thiamin and thiamin monophosphate circulate in the bloodstream, the former bound to plasma proteins. Approximately 30 mg of total thiamin is found in human body, of which about 80% is thiamin diphosphate, 10% is thiamin triphosphate, and the remainder is free thiamin and thiamin monophosphate. Due to the low storage capacity and the relatively high turnover rate of thiamin, a regular intake of this vitamin is then necessary [1, 3].

## *2.2.3 Function*

Thiamin diphosphate is a coenzyme for three multienzyme complexes involved in the oxidative decarboxylation of oxoacids: pyruvate dehydrogenase, α-ketoglutarate dehydrogenase and branched-chain ketoacid dehydrogenase. Thiamin triphosphate plays a role in nerve transmission for sodium and potassium transport [1, 3].

## **2.3 Vitamin B2 (riboflavin)**

The water-soluble vitamin riboflavin was synthesized independently by Kuhn's and Karrer's groups in 1935 [3]. This fluorescent, yellow crystalline compound was discovered during the 1920s as a preventive factor from human "pellagra" as well as "beriberi" disease. Riboflavin is a flavin with the flavin ring attached to an alcohol related to ribose [2]. It is a relatively heat–stable molecule but it is rapidly inactivated in ultraviolet (UV) light [7].

## *2.3.1 Dietary sources*

Major food sources of vitamin B2 include milk and dairy products as well as meat and meat products. Green vegetables such as collard greens, turnip greens and broccoli are good sources of riboflavin. Natural grain products contain low amounts of riboflavin but enrichment of these food items with the vitamin has improved its intake. Vitamin B2 is also widely used as food color due to its intense yellow color [2, 3, 7].

## *2.3.2 Absorption, metabolism and storage*

Flavin coenzymes are hydrolyzed by alkaline phosphatase in the upper small intestine to free riboflavin, which is then absorbed. Absorption is enhanced when riboflavin is ingested along with other foods and in the presence of bile salts. Much of the absorbed riboflavin is phosphorylated in the intestinal mucosa and enters the bloodstream as riboflavin phosphate. About 50% of plasma riboflavin in plasma is free riboflavin, with somewhat less flavin adenine dinucleotide (FAD) and less

than 10% flavin mononucleotide (FMN). The average concentration of riboflavin in plasma is about 0.03 μM [3, 4, 7]. The liver is the main storage organ of vitamin B2. Other storage sites are the spleen, kidney and cardiac muscle. Urinary excretion of vitamin B2 occurs predominantly in the form of free riboflavin with a small amount as a variety of its glycosides and metabolites [4].

#### *2.3.3 Function*

Riboflavin functions as the precursor of the flavin coenzymes, FMN and FAD, and of covalently bound flavins. These coenzymes catalyze numerous oxidation– reduction reactions in several metabolic pathways including the mitochondrial electron transport chain. The majority of flavoproteins require FAD as the prosthetic group rather than FMN. Other major functions of riboflavin include drug, lipid and steroid metabolisms [3, 7, 8].

## **2.4 Vitamin B3 (niacin)**

Niacin is a generic term referring to two vitamers nicotinic acid and nicotinamide. Nicotinic acid was discovered by Huber in 1867 as a product of nicotine oxidation, but its curative and preventive role against "pellagra" disease was not recognized until much later, in 1938. Niacin is a whitish water-soluble crystalline compound. It can be synthesized in the body from the essential amino acid tryptophan, which constitutes an important route for meeting the body's niacin requirement [1, 2, 7].

#### *2.4.1 Dietary sources*

Niacin requirements are generally expressed as mg niacin equivalents; 1 mg niacin equivalent = 1 mg preformed niacin + 1/60 × mg tryptophan. Due to the contribution of tryptophan, foods rich in proteins are important sources of the vitamin. Lean red meat, fish, liver and poultry contain high amounts of both niacin and tryptophan. Other contributors to niacin intake include ready-to-eat cereals supplemented with nicotinic acid. Vegetables and fruits provide useful amounts of the vitamin, depending upon the dietary intake [1, 3, 7].

#### *2.4.2 Absorption, metabolism and storage*

Niacin is present in food largely in the form of the nicotinamide nucleotides, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These nucleotides are hydrolyzed to free nicotinamide in the intestinal lumen. At low concentrations, absorption from the small intestine is mediated by a sodium-dependent facilitated diffusion. At higher amounts, absorption is by passive diffusion [7, 9]. Niacin compounds entering the portal circulation are either transported to the liver or internalized by erythrocytes. In the liver, nicotinic acid and nicotinamide, together with tryptophan, are converted to (NAD). On reaching the tissues, the niacin vitamers are used for the intracellular synthesis of NAD and NADP. The liver plays an important role in the preparation of niacin for urinary excretion, converting excess niacin to methylated derivatives [3, 7].

#### *2.4.3 Function*

The nicotinamide nucleotides NAD and NADP play a major role in a wide variety of oxidation–reduction reactions. The NAD coenzyme is involved in catabolic

reactions while NADP is more often required in synthetic mechanisms such as the synthesis of steroids and fatty acids [1]. The coenzyme NAD is easily convertible to NADP and vice versa, while both molecules can also exchange their oxidation state. This conversion maintains a balance between the energy-consuming synthetic reactions and the catabolic reactions that produce energy [1].

## **2.5 Vitamin B6**

The pure crystalline water-soluble vitamin B6 was first isolated in 1938 by Lepkovsky, than synthesized by Harris and Folkers in 1939. There are six nutritionally active B6 vitamers, namely pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM), and the corresponding 5′-phosphate esters pyridoxine phosphate (PNP), pyridoxal phosphate (PLP) and pyridoxamine phosphate (PMP) [2, 3]. Aqueous vitamin B6 solutions are colorless, except for PLP solutions, which are yellow and not very stable in neutral or alkaline medium [11].

## *2.5.1 Dietary sources*

High quantities of vitamin B6 are found in yeast, liver, fortified cereals and grain germs. Other important sources include nuts, pulses, meat, fish, avocado, banana and potatoes. Eggs, fruit and milk, contain relatively low concentrations of the vitamin [1, 3, 9].

## *2.5.2 Absorption, metabolism and storage*

The absorption of vitamin B6 occurs following the hydrolysis of the phosphorylated forms in the lumen of intestine through a sodium-dependent carrier-mediated system [7]. Once absorbed, the different forms of the vitamin B6 vitamers are interconverted and conveyed to the liver in the form of free non-phosphorylated vitamers. In the liver, the vitamers are accumulated by diffusion and converted to phosphorylated forms, under the action of pyridoxal kinase enzyme. The PNP and PMP are oxidized to PLP by pyridoxine oxidase. A proportion of PLP is released into the bloodstream bound to plasma albumin. The remaining portion of PLP is dephosphorylated and oxidized to pyridoxic acid, which is released into the plasma and excreted in the urine [3].

## *2.5.3 Function*

The metabolically active vitamer is PLP, which is involved in a wide variety of amino acids reactions, including transamination, transulphuration, desulphuration and decarboxylation. PLP is also required in the regulation of steroid hormone actions. In addition, PLP vitamer acts as the cofactor of glycogen phosphorylase in muscle and liver and has an essential role in lipid metabolism and immune function [3, 4, 8].

## **2.6 Vitamin B9 (folates)**

The water-soluble vitamin B9 is represented by the group of folates (from *folium* the Latin word for leaf). The isolation, chemical structure determination and synthesis of vitamin B9 was carried out in 1946 by Angier's group [3]. Since the early 1990s, the associations between folate intake and birth outcome or chronic disease risk were investigated. Research studies established a reduction in the risk of neutral tube defects after a daily periconceptional supplementation with folic acid. These

important results led to the implementation of public health policies that include mandatory folic acid fortification in North America [7].

#### *2.6.1 Dietary sources*

Good sources of folate include fortified grain products, orange juice, fresh dark green leafy vegetables, lentils, kidney beans, lima beans, avocado, peas and peanut products. Meat in *general* is not a good source of folate, except liver [1, 3, 7].

#### *2.6.2 Absorption, metabolism and storage*

About 80% of dietary folate occurs in a polyglutamate form, which is hydrolyzed to the monoglutamate form before absorption by enterocytes primarily in the jejunum. Monoglutamyl folate is then transported across the intestinal mucosa via a saturable, pH dependent active transport process. Nevertheless, at high concentrations, the intestinal uptake takes place by a nonsaturable passive diffusion. Plasma folate, primarily 5-methyl THF, is distributed in two major forms: free folate and folate bound to albumin. A small proportion of plasma folate (less than 5%) is bound to high-affinity binders [3, 4, 8]. The majority of reduced monoglutamates arriving at the liver from the intestine is metabolized and retained or released into the blood or bile [3]. Folate is excreted in the urine as folate derivatives and only 1%-2% of the vitamin is emitted as intact urinary folate [7].

#### *2.6.3 Function*

Due to their chemical structure, folates play a major role in the mobilization of one-carbon units in intermediary metabolism. Such reactions are required in the synthesis of the purines guanine and adenine and the pyrimidine thymine, which are used in the formation of nucleoproteins deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) [2, 3]. Folates are also essential in the metabolism of amino acids, by means of THF derivatives that serve as donors of one-carbon units in a variety of synthetic reactions [3].

## **2.7 Vitamin B12**

Vitamin B12 was discovered after a series of important contributions from different fields including medicine, chemistry and microbiology, which led to the awarding of Nobel Prizes. The chemical structure of vitamin B12 was elucidated by the x-ray crystallographer Dorothy Hodgkin, that was awarded the Nobel Prize for chemistry in 1964. The total chemical synthesis of vitamin B12 took 11 years and was led by Robert Woodward, who received the Nobel Prize in Chemistry in 1965 [7]. The term vitamin B12 is used as a generic descriptor of cobalamins, which have a structure similar to heme but the central iron atom is replaced by a cobalt atom. Cyanocobalamin, a water-soluble purplish red powder, is the most stable of the vitamin B12-active cobalamins. It is widely used in food supplementation and pharmaceutical preparations. However, it is a light sensitive molecule [3, 11].

#### *2.7.1 Dietary sources*

Vitamin B12 is found almost exclusively in foods of animal origin and liver is the most abundant dietary source of the vitamin followed by kidney and heart [2, 3]. Other important sources include milk, fish, eggs, shellfish and muscle meat. Different forms of vitamin B12 exist in foods such as adenosyl- and hydroxocobalamins in

meat and fish, Sulphitocobalamin in canned meats and fish and small quantities of Cyancobalamin in egg white and cheeses [3].

## *2.7.2 Absorption, metabolism and storage*

Vitamin B12 is absorbed by two different mechanisms: one active and the other passive. The major route of vitamin B12 active absorption is by attachment in the intestinal lumen to a small glycoprotein secreted by the parietal cells of the gastric mucosa named intrinsic factor. In the stomach, vitamin B12 binds to cobalophilin protein, which is hydrolyzed in the duodenum, releasing vitamin B12 to bind to intrinsic factor. In plasma, vitamin B12 circulates bound to transcobalamin I and II proteins, which prevent the vitamin from urine excretion as it passes through the kidney [3, 8]. With over 60% of the total vitamin content present in the body, the liver is the richest organ in vitamin B12.

## *2.7.3 Function*

Viamin B12 is involved in the metabolism of proteins, fats and carbohydrates. It is essential in the regeneration of the 5-methyl-folic acid into folic acid, which prevents from its direct urine excretion. In addition, vitamin B12 contributes to the transport and storage of folic acid in cells and plays a crucial role in the synthesis of myelin lipoprotein [1]. Vitamin B12 is also an important cofactor in the maintenance of normal DNA synthesis, the regeneration of methionine for adequate protein synthesis and methylation capacity, and the avoidance of homocysteine accumulation leading to various degenerative diseases [7].

### **2.8 Vitamin C (ascorbic acid)**

The scurvy disease, due to vitamin C deficiency, was described in the Ebers papyrus of 1500 B.C. and by Hippocrates [4]. It was endemic in many areas, especially in the earliest explorations of the New World where over 2 million sailors died of scurvy during the era, often called the "Age of Sail" [7]. The structure of vitamin C, was elucidated in 1933 by Walter Haworth and his associates, at the University of Birmingham in England. It was synthesized in the same year by the same research team [3]. Vitamin C is the generic descriptor for all compounds with the biological activity of L-ascorbic acid. It is a water-soluble white crystalline powder, that is stable at solid state and that serves as a good reducing agent [2, 11].

## *2.8.1 Dietary sources*

Vitamin C is synthesized by almost all living organisms, except humans and other primates, guinea pigs, fish, fruit-eating bats and some exotic birds [3, 8]. It occurs in significant amounts in green vegetables, fresh fruits, especially citrus fruits and blackcurrants and in animal organs such as liver, kidney and brain. Other good sources of vitamin C include potatoes, tomatoes, strawberries and cabbage. Muscle meat and cereal grains are poor dietary sources of the vitamin. Cooking causes significant losses of vitamin C through leaching into the cooking water and also atmospheric oxidation [3, 7].

## *2.8.2 Absorption, metabolism and storage*

The biologically active forms of vitamin C are ascorbic acid and dehydroascorbic acid. Both vitamers are absorbed across the buccal mucosa by carrier-mediated

passive processes. At physiological intakes, the intestinal absorption of vitamin C is by active transport mechanism, while at high doses, there is a less efficient passive diffusion, which proceeds at a very low rate [11]. In plasma, vitamin C occurs mainly as free ascorbate, and dehydroascorbic acid is present at undetectable concentrations. Liver has the greatest store of vitamin C in the body by virtue of its size. Other organs containing ascorbate include kidney, pancreas and brain. Excretion of vitamin C is mainly in urines with negligible amounts of ascorbic acid or its catabolites excreted in feces [3].

### *2.8.3 Function*

Vitamin C acts as a cofactor in various hydroxylation reactions catalyzed by oxygenases. For example, vitamin C plays an important role in collagen and catecholamines biosynthesis. It is also involved in carnitine synthesis, which takes place in liver from the amino acid lysine. Both vitamin C and copper act as cofactors in the catabolism of phenylanaline and thyrosine enzymes, which is impaired with vitamin C deficiency. In addition, some peptide hormones like peptidylglycine are activated in the presence of copper, oxygen and ascorbate. By promoting the incorporation of iron into ferritin, vitamin C influences the distribution of this mineral in the body. It is also required in the metabolism of histamine and nitrosamine. Moreover, vitamin C increases the mobility of leukocytes and protects their membranes from oxidative attacks. Due to its high reducing power, vitamin C has also an important biochemical function of antioxidant. The powerful antioxidant action of vitamin C allows it to protect the sperm from AND oxidative attacks or the eye from radical attacks [11].

#### **2.9 Vitamin D**

Rickets, a disease due to vitamin D deficiency, occurred in ancient times about 50,000 B.C. [7]. Due to air pollution and little sunlight, Rickets has spread in northern Europe, England, and the United States during the Industrial Revolution. There are two common forms of vitamin D: cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2). The structures of vitamin D2 and vitamin D3 were determined by Windaus and his associates respectively in 1932 and in 1936, in Germany. Dorothy Hodgkin, the Nobel laureate x-ray crystallographer, was the first to develop a threedimensional model of vitamin D3. While vitamin D2 is synthesized in plants, fungi and yeasts by the solar irradiation of ergosterol, vitamin D3 is produced *in vivo* by the action of sunlight on skin [3, 7].

#### *2.9.1 Dietary sources*

There are relatively few sources of vitamin D. The richest dietary sources are fish-liver oils, especially halibut-liver oil. Other major sources of the vitamin are fatty fish such as tuna, sardines, pilchards or herring. Eggs, mammalian liver and dairy products are good sources of vitamin D. However, vegetables, fruit and cereals are exempt of the vitamin. Fortified products include margarine, breakfast cereals and milk. Vitamin D can also be synthesized by the skin after exposure to sunlight. This endogenous synthesis constitutes a much more important source of vitamin D than foodstuff [2, 3, 8].

#### *2.9.2 Absorption, metabolism and storage*

Vitamin D is absorbed in lipid micelles and incorporated into chylomicrons through the lymphatic system. Following intestinal absorption, vitamin D is rapidly *Food Supplementation with Vitamins and Minerals: An Overview DOI: http://dx.doi.org/10.5772/intechopen.98287*

taken up by the liver, where it is hydroxylated to form the 25-hydroxy derivative calcidiol before entering the circulation bound to a vitamin D binding globulin. On arrival at the kidney, the calcidiol undergoes 1-hydroxylation to yield the active metabolite 1,25-dihydroxyvitamin D (calcitriol) or 24-hydroxylation to yield an apparently inactive metabolite, 24,25-dihydroxyvitamin D (24-hydroxycalcidiol) [3, 8]. These conversions are regulated in response to the concentrations of calcium and phosphorous minerals in plasma. Vitamin D is mainly excreted in bile after catabolism into highly polar inactivation products by the liver [3].

## *2.9.3 Function*

The primary physiologic role of vitamin D is to maintain the plasma concentrations of calcium and phosphorous in the body. Calcitriol acts to rise intestinal absorption of calcium, to decrease its excretion and to mobilize the mineral from bone [4]. It plays an important role in immune muscle functions, nervous system and cell differentiation. In addition, it regulates more than 50 genes by activating nuclear receptors that modulate gene expression. 24-hydroxycalcidiol has also a biological activity in cartilage or in bone formation during the development of knockout mice [4].

## **3. Minerals**

Minerals are inorganic substances that are required for normal metabolism, development, growth, body structure, cell function regulation, and electrolyte


**Table 2.**

*Deficiency and toxic effects of selected minerals.*

balance [13]. Minerals are divided in two groups, the major (macro) minerals, which are present in the human body in concentrations greater than 100 milligrams per kilogram and trace (micro) minerals occurring at much lower amounts (micrograms or milligrams per kilogram) [8]. Minerals are considered as essential when deficiency symptoms are noted with depletion or removal. Typically, calcium constitutes about 46% and phosphorous about 29% of total body minerals. Chloride, potassium, sulfur, sodium and magnesium together account for about 25%, while essential trace elements represent less than 0.3% of the total. Bone is the primary storage site for many essential elements (99% of the total calcium, 80 to 85% of phosphorous and some 70% of magnesium), while the thyroid gland contains more than 80% of the total body iodine. Generally, mineral distribution within the body's tissue is not uniform and each organ has a specific mineral composition [14]. **Table 2** shows the benefits and potential harmful effects associated with deficiency or excess intake of four frequently used minerals as food additives and/or supplements [1, 2, 9, 10, 15].

### **3.1 Calcium**

Calcium is a soft, silvery white metal ranked fifth in order of abundance among the elements in the earth crust. It has an atomic weight of 40.08, and an atomic number of 20. Calcium is found in nature only in compounds, mainly as carbonate, fluoride, sulfate and phosphate [8, 14]. Metallic calcium or calcium compounds are used in steel industry, plastics, cement manufacture, paper industry, alloys production, etc. Calcium is the most abundant mineral in the organism and 99% of this macro mineral is found in bone and teeth [14].

#### *3.1.1 Dietary sources*

Dairy products are the most important dietary sources of calcium including milk, yoghurt and cheese. Tinned fish such as sardine, oilseeds like almonds and dried fruit are also good sources of calcium. Generally, foods of plant origin are poor sources of calcium. However, due to their high level of consumption they make a significant contribution to the total calcium intake. Contributions from calciumenriched foods such as breakfast cereals and dietary supplements containing calcium salts may be also significant [8].

#### *3.1.2 Absorption, metabolism and storage*

The absorption of calcium takes place by two mechanisms. The first is active and regulated by vitamin D and the second is by passive diffusion. At low levels of dietary calcium, most of the absorption is by active transport and is done principally in the duodenum. Passive diffusion is more important at high calcium intakes and ileum is the most active absorptive site. The large intestine contributes also to calcium absorption. Generally, only 30 to 50% of dietary calcium is normally absorbed [14]. Calcium absorption is largely dependent on other nutrients in the diet, hormonal status and physiological conditions such as pregnancy and breastfeeding [1]. Lactose and vitamin C supplementation increase calcium absorption. Dietary sources rich in oxalic acid or phytic acid could inhibit calcium absorption from foodstuff [9]. Calcium homeostasis is regulated by calcitonin and parathyroid hormones that are associated to the active form of vitamin D, 1,25-dihydroxyvitamin D. Bone is the primary storage site of calcium and the decrease of calcium levels in blood leads to a quick metal mobilization from the bone to bring the blood levels back to normal. Plasma contains from 9 to 12 mg of calcium per 100 mL, which

is distributed in ionized, protein bound and complexed fractions. Excretion of calcium is done principally in feces.

## *3.1.3 Function*

The primary role of calcium in the body is to form the structures of bone and teeth. During skeletal growth and maturation, calcium accumulates in the skeleton at an average rate of 150 mg/day. During maturity, the skeleton is in calcium equilibrium until the age of fifty, from which the bone is lost from all skeletal sites. This bone loss increases the risk of hip fracture with aging. Extraskeletal calcium, which represent around 1% of the total body calcium, play important roles in various essential functions in body metabolism such as enzymatic activation, cell division, muscular contraction, nerve transmission and vesicular secretion [1, 8].

## **3.2 Magnesium**

Magnesium is a silvery white metal ranked seventh in order of abundance in the crust. It has an atomic number of 12 and an atomic weight of 24.31. Magnesium occurs in nature in compounds such as dolomite, magnetite, epsomite and carnallite. Due to its relatively low density (1.74 g/cm3 ), magnesium is widely used as a construction material. Other applications include production of alloys, steel industry, automotive construction, aviation and space technology, glass and cement manufacture, etc. [16]. In green plants, magnesium plays a central role, as photosynthesis does not proceed, when the metal has been removed from the chlorophyll molecule.

## *3.2.1 Dietary sources*

Dietary sources rich in magnesium include whole grains, green leafy vegetables, tofu and nuts. Milk, legumes and potatoes are good sources of the metal. Plants are generally well endowed with magnesium due to its central role in photosynthesis [8, 9].

## *3.2.2 Absorption, metabolism and storage*

The main site of magnesium absorption is the small intestine. Active transport, solvent drag and passive diffusion are the three mechanisms of magnesium absorption. Generally, 20–70% of ingested magnesium is absorbed in normal healthy humans [8]. Magnesium absorption could be affected by many dietary and physiological factors. While protein intake seems to increase magnesium absorption, fat supplementation has been shown to generate the opposite effect. In addition, high levels of phosphorous and calcium inhibit magnesium absorption. Magnesium is primarily stored in the bones (60–70%) and the remainder is evenly distributed between muscle and other soft tissue. Magnesium is excreted mainly in the urine or in feces [14].

## *3.2.3 Function*

Magnesium has various physiological functions. Its is involved in more than 300 enzymatic processes in the body and plays an important role in skeletal mineralization and development, fatty acids synthesis, phosphorylation and dephosphorylation mechanisms, DNA and protein synthesis, insulin action in the liver, metabolic pathways for energy production, sodium and phosphorous metabolism and maintenance of transmembrane electrical potentials in nerves and muscle [1, 14].

#### **3.3 Iron**

Iron is a silvery-white metal classified second in the order of abundance of the elements in the earth crust after aluminum. It has an atomic number of 26 and an atomic weight of 55.8. It is mainly combined with oxygen in the crust forming iron oxide ores such as hematite, magnetite or limonite. Due to its interesting physicochemical properties, iron is used in various domains such as steel industry, alloys, food fortification, environmental protection, bio-medical applications, etc. Iron is an essential element for almost all living organisms. It exists in the body in complex forms bound to protein as heme compounds (hemoglobin and myoglobin), heme enzymes, or nonheme compounds (transferrin, ferritin, and hemosiderin [14]. Iron deficiency anemia is the most common deficiency disorder in the world [8, 14].

#### *3.3.1 Dietary sources*

Organ meats such as liver and kidney, egg yolk, dried legumes, cocoa, cane molasses, and parsley are among the richest dietary sources of iron. Meat meals and fish meals contain lower iron amounts than blood meals. Generally, the bioavailability of heme iron found in animal products is better than that of nonheme iron found in vegetables or chlorophyll plants. Poor sources of iron include dairy products, fresh fruits and vegetables, white floor, white sugar and unenriched bread [1, 14].

#### *3.3.2 Absorption, metabolism and storage*

Generally, iron absorption increases with higher dietary intake of the metal. Only 5 to 15% of ingested iron is absorbed by human adults. However, this level may increase to twice or more in children and in deficient adults. The primary sites of iron absorption are the duodenum and the jejunum in the small intestine. Iron absorption is enhanced by ascorbic acid and cysteine dietary intake. However, tannins, phytates, egg yolk, tea, coffee, milk and soy proteins have an inhibitory effect on iron absorption [1]. Upon entering plasma, ferrous iron is oxidized to ferric form, then most of it binds to transferrin, and the rest to ferritin. Transferrin regulates iron body distribution by transporting more than 70% of plasma iron to the bone marrow for hemoglobin synthesis. The synthesized hemoglobin is then destroyed by phagocytes and the released iron is either returned to the circulation via plasma transferrin or stored as ferritin or hemosiderin. The liver, spleen, and bone marrow are the main sites of iron storage in the body [9]. Excretion of iron is done primary in feces and urine in addition to losses through sweat, hair, and nails [14].

#### *3.3.3 Function*

Almost *two*-thirds of body's iron is found in hemoglobin, a quarter is stored and most of the remaining 15% is in the muscle protein myoglobin. The primary function of iron is the transport of oxygen and carbon dioxide in the organism through red cells [1]. Iron is also a component of various enzymes required for energy production, immune system functioning or adenosine triphosphate (ATP) production.

#### **3.4 Iodine**

Iodine is a bluish black solid that belongs to halogen family including fluorine, chlorine and bromine. It has an atomic number of 53 and an atomic weight of 126.9. It is a relatively rare element in the earth's crust, which occurs in the dispersed state

#### *Food Supplementation with Vitamins and Minerals: An Overview DOI: http://dx.doi.org/10.5772/intechopen.98287*

in soil, water, air, and living organisms. There are many regions in the world low in iodine. This could be due to distance from the sea, low annual rainfall or recent glaciation [14]. Iodine is used in many industrial fields such as pharmaceutics, medicine, metallurgy, lasers, herbicides, animal feeds, colorants, photographic equipment, etc. [8]. Iodine deficiency is one of the main cause of impaired cognitive development in children.

## *3.4.1 Dietary sources*

The iodine content of food is highly dependent on the type of soil, climatic conditions and fertilizers. Hence, it is useless to give the concentration of dietary iodine in food composition tables since it is highly variable. Nevertheless, seafood, fish, seaweed and plants of the seaside are very rich in iodine. Fortified foods are also good iodine sources such as breakfast cereals or milk and milk products. The salt iodized with potassium iodate remains the most reliable source of iodine worldwide [1, 9].

## *3.4.2 Absorption, metabolism and storage*

Iodine in water and food occurs usually as iodide or iodate compound. In these forms, it is rapidly absorbed in the gastrointestinal tract and circulates in the blood to all body tissues. Over 90% of ingested iodine is concentrated in the thyroid gland for adequate thyroid hormone synthesis or excreted in urine. If iodine supply is abundant, only 10% of iodine absorbed by the gut appears in the thyroid. However, this fraction may reach 80% or more, with long-standing iodine deficiency [14]. Iodine is stored in thyroid in the form of thyroglobulin, an iodinated glycoprotein that represent 90% of the total thyroid iodine. It is excreted either as organic iodine in the feces or as free iodine in the urine. Important goitrogen-containing foods include cassava, broccoli, cabbage, sprouts, kohlrabi, turnips, swedes, rapeseed, and mustard [8].

## *3.4.3 Function*

Iodine is an essential constituent of the thyroid hormones thyroxine, and triiodothyronine. These hormones have multiple biological roles in thermoregulation, reproduction, growth and development, intermediary metabolism, cell activity, and muscle function. Thyroid hormones also affect heart rate, respiratory rate, metabolism of carbohydrates and lipogenesis. In addition, they regulate proteins associated with cartilage metabolism, skin epidermis and hair production [8, 14].

## **4. Multivitamins and minerals as food supplements**

#### **4.1 Prevalence of use and associated factors**

Vitamins and minerals are found in diets rich in fruits and vegetables. In the early 20th century, these micronutrients have been isolated, purified and manufactured as dietary supplements. Multivitamin/mineral (MVM) supplements, defined by the National Institutes of Health (NIH) as dietary supplements containing 3 or more vitamins and minerals, are the most commonly used type of dietary supplements among adults in the United States (US) [17]. According to the National Health and Nutrition Examination Survey (NHANES) 2011–2014 data

(n = 11,024), 52% of US adults took at least one dietary supplement in a 30-day period and MVM supplements account for the vast majority of total dietary supplements use [18]. MVM use was higher among women (34.0%) than men (28.3%) and the use raised linearly with age. Supplementation with MVM was particularly higher among older women (44.0%), non-Hispanic whites (35.7%), higher educated adults (36.3%), overweight adults (34.0%), former smokers (37.8%), moderate alcohol consumers (1 drink/day) (39.0%), adults with excellent or very good self-reported health status (36.7%) and those with private health coverage (35.1%) compared to their counterparts [18]. Perlitz et al. reported data on the use of vitamins and mineral supplements by adolescent living in Germany from the second wave of the German Health Interview and Examination Survey for Children and Adolescents (EsKiMoII), conducted from June 2015 to September 2017 [19]. They found that 16.4% of the adolescents (girls: 18.8%, boys: 14.0%) aged 12 to 17 years had consumed vitamin or mineral supplements in the previous four week. The use of micronutrients was higher among girls (18.8%) than boys (14.0%), normal weight adolescent (17.0%) than overweight ones (9.3%) and among adolescents with a high level of physical exercise (19.9%) than those with a low level of physical exercise (11.5%). Only one supplement, with both vitamins and minerals nutrients, was consumed by the majority of users. The most frequently used vitamin supplements were vitamin C (43.9%), followed by vitamin D (41.1%) and vitamin B12 (30.4%). As regards mineral supplements, those containing magnesium (45.9%), zinc (28.1%), and iron (24.1%) were the most commonly consumed [19]. In Iran, the prevalence of dietary supplements use among children and adolescents was 34.1% [20]. Iron supplements were the most frequently used dietary supplements, with a prevalence of use of 12.9%, followed by multivitamins (8.1%) and vitamin D supplement (2.9%). Results showed that boys, children with excess weight and those with high-educated parents used less supplements compared to their counterparts [20].

Pregnant women are particularly vulnerable population groups and the MVM supplementation especially with iron and folic acid in pregnancy is highly recommended to improve birth outcome and to reduce low birth weight [21]. Data on MVM supplementation of pregnant women living in European countries revealed the presence of iron, iodine, vitamin A and zinc deficiencies, not only in lowincome countries but also to an extent in Europe [22]. The inadequate intake among pregnant women may be due to poor knowledge about adequate nutrition, healthy vegetarian or vegan diets, special diets that avoid excessive weight gain, etc. [22]. Data on the dietary intake and mineral status of Polish pregnant women showed that 53.7% of pregnant women used supplements during pregnancy. Of supplement users, 93% took folic acid and only 16% consumed iron. Composite vitamin and mineral supplements were used by only 17.6% of Polish pregnant women [23]. Results of the NHANES 2007-2014 cross-sectional study revealed that 61.6% of American pregnant women used MVM supplements during pregnancy. However, the majority of this group do not consume the recommended amount of fruits and vegetables (five servings per day) [24].

#### **4.2 Recommended intakes**

**Table 3** displays the recommended intakes of selected vitamins and minerals for men and women according to AFSSA (French Food Safety Agency), EFSA (European Food Safety Authority), IOM (Institute of Medicine) and WHO (World Health Organization) [25]. **Table 3** shows that several terms, referring to the population's nutritional references, are used by the different organisms. Hence, it is necessary to harmonize these terms.


#### *Food Supplementation with Vitamins and Minerals: An Overview DOI: http://dx.doi.org/10.5772/intechopen.98287*

**Table 3.**

*6Recommended Dietary Allowance.*

*Population's nutritional references of selected vitamins and minerals (mg/d).1*

### **4.3 Availability and regulatory status**

MVM supplements can be obtained directly by the health care providers or purchased from retail stores such as pharmacies, grocery stores or health food stores. Many forms of vitamins and minerals and many routes of administration are available [13]. For example, vitamin D is manufactured as cholecalciferol or ergocalciferol and iodine is available as iodide or iodate [26]. Vitamin and mineral dietary supplements can be compounded in various ways and sold in capsules, pills, tablets, sachets of powder, ampoules of liquids and other similar forms of powder and liquids [13].

According to the Codex Alimentarius Guidelines for Vitamin and Mineral Food Supplements, the sources of vitamin and mineral supplements may be natural or synthetic and their selection should be based on considerations such as safety and bioavailability [27]. The minimum level of each vitamin and/or mineral contained in a vitamin and mineral supplement per daily portion of consumption should be 15% of the WHO recommended dietary intake. Moreover, the vitamin and mineral supplements must be packed in containers that are safe and suitable for their intended use.

## **4.4 Health effects**

The use of MVM supplements is recommended in disease states, to correct deficiencies, or to promote health and protect from future chronic diseases in healthy subjects [28–31]. The main nutrient deficiency diseases prevalent in developing countries include *Xerophthalmia,* which is responsible of the blindness of over five million children suffering from visual impairment in the world [32]. According to Beaton et al. (1993), vitamin A supplementation reduces the mortality of children aged from six months to five years by 23% [33]. In addition, data showed a decrease in the prevalence of *Xerophthalmia* in children who regularly received vitamin A supplements, reaching 70% [32, 33]. In 1999, over 700 million people living in developing countries suffered from goiter and cretinism with severe brain damage and mental retardation [8]. An important progress was made with universal salt iodization including an approximate 13-point increase in intelligence quotient [32]. Iron deficiency anemia have adverse effects on the development of children as well as on the mortality and morbidity of infant and mother during pregnancy [8]. Research studies established that the use of iron supplements allowed a 20% reduction in mothers mortality [32]. In Nepal, the results of a demographic and health survey carried out in 2006 showed that in five years, the coverage of iron supplementation increased from 23–59%. These improvements, associated to additional measures, led to a reduction in iron deficiency anemia in pregnant women from 75–42% [34]. Zinc deficiency is associated to the incidence of serious childhood infectious diseases such as pneumonia and diarrhea, which causes 18% of deaths in children under five [35–37]. Zinc supplementation of children during acute diarrhea allowed the decrease of the illness duration by 9-23% [36]. In a community-based, double-blind, randomized trial conducted in India, zinc supplementation resulted in a 33% lower diarrheal incidence in children with low plasma concentrations [38]. During pregnancy, there is a high risk of fetal neural tube defects with folate deficiency. Research studies proved that folate intake by pregnant women reduced the risk of neural tube defects by 50% [32, 39].

## **5. Addition of vitamins and minerals to food**

Vitamins and minerals are added to foods mainly to improve or maintain their nutritional quality. However, these nutrients are also used for other additive *Food Supplementation with Vitamins and Minerals: An Overview DOI: http://dx.doi.org/10.5772/intechopen.98287*


#### **Table 4.**

*Examples of use of vitamins and minerals as food additives.*

functions (**Table 4**) [40]. Various forms of vitamin and mineral additives are commercially available such as powders, oily suspensions or emulsions [2, 40]. The most important factors affecting their stability include heat, oxygen, pH, moisture and light. For example, the stability of β-carotene and other provitamin A carotenoids is enhanced by ascorbic acid antioxidant, both in liquid or powder forms [41]. In addition, vitamin D is more stable when prepared in edible oils than in powder form. Preparations of vitamin D are usually provided in lightproof containers with inert gas flushing. The detrimental interactions between vitamins and minerals are also taken in consideration in the manufacture of these micronutrients, especially in liquid preparations. Some interactions between vitamins are advantageous such as niacinamide that act as solubilizer for riboflavin and folic acid [41].

## **6. Conclusion**

Despite the essential role of vitamins and minerals in human's health, these micronutrients are not consumed in sufficient amounts in developing countries where millions of children die each year from micronutrients deficiency due to malnutrition. Therefore, additional efforts should be made worldwide to minimize disparities between developing and developed countries in the quality of nutrition.

### **Acknowledgements**

The authors want to acknowledge professor Jalila El Ati, responsible of the laboratory SURVEN of the National Institute of Nutrition and Food Technology for her precious advices.

*Natural Food Additives*

## **Author details**

Myriam El Ati-Hellal1 \* and Fayçal Hellal2,3

1 University of Carthage, IPEST (Preparatory Institute for Scientific and Technical Studies), Laboratory Materials Molecules and Applications, Tunis, Tunisia

2 INNTA (National Institute of Nutrition and Food Technology), SURVEN (Nutrition Surveillance and Epidemiology in Tunisia) Research Laboratory, Bab Saadoun, Tunis, Tunisia

3 University of Carthage, Tunisia

\*Address all correspondence to: mfh22002@yahoo.fr

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Food Supplementation with Vitamins and Minerals: An Overview DOI: http://dx.doi.org/10.5772/intechopen.98287*

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## **Chapter 6**

## New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry

*Arantzazu Santamaria-Echart, Isabel P. Fernandes, Samara C. Silva, Stephany C. Rezende, Giovana Colucci, Madalena M. Dias and Maria Filomena Barreiro*

## **Abstract**

The food industry depends on using different additives, which increases the search for effective natural or natural-derived solutions, to the detriment of the synthetic counterparts, a priority in a biobased and circular economy scenario. In this context, different natural emulsifiers are being studied to create a new generation of emulsion-based products. Among them, phospholipids, saponins, proteins, polysaccharides, biosurfactants (e.g., compounds derived from microbial fermentation), and organic-based solid particles (Pickering stabilizers) are being used or start to gather interest from the food industry. This chapter includes the basic theoretical fundamentals of emulsions technology, stabilization mechanisms, and stability. The preparation of oil-in-water (O/W) and water-in-oil (W/O) emulsions, the potential of double emulsions, and the re-emerging Pickering emulsions are discussed. Moreover, the most relevant natural-derived emulsifier families (e.g., origin, stabilization mechanism, and applications) focusing food applications are presented. The document is grounded in a bibliographic review mainly centered on the last 10-years, and bibliometric data was rationalized and used to better establish the hot topics in the proposed thematic.

**Keywords:** natural emulsifiers, biosurfactants, emulsion technology, Pickering emulsions, food applications, market and product trends

#### **1. Introduction**

Food emulsions are produced from two immiscible liquids (usually oil and water), which in the presence of an emulsifier and by applying an emulsification method, can be dispersed one into another. Some typical examples include mayonnaise, salad dressings, sauces, milk, ice cream, and sausages. These systems can be used to encapsulate, protect, and deliver biocompounds, including vitamins, flavors, colorants, and nutraceuticals [1]. Emulsifiers are food additives acting by forming a physical barrier between the oil and water, enabling their compatibilization. Effective emulsifiers must be quickly adsorbed at the oil–water interfaces

leading to a rapid decrease in the interfacial tension, preventing droplets aggregation. Moreover, they must generate strong repulsive interactions promoting emulsion stability [2, 3].

Synthetic emulsifiers (e.g., Tweens and Spans) are well-known for their ability to form highly stable emulsions. However, consumers' preferences for healthy, sustainable and natural lifestyle habits have increased worldwide. Moreover, some studies have reported intestinal dysfunctions caused by synthetic emulsifiers [4, 5]. In this context, natural emulsifiers have emerged as great alternatives to replace their conventional counterparts, namely proteins [6], polysaccharides [7], phospholipids [8] and saponins [9]. Concerning protein-based natural emulsifiers, the most use ones come from animal sources (e.g., whey proteins, caseins, egg protein, gelatin) [10]. However, plant-based proteins have demonstrated to be good alternatives for their replacement in products with dietary restrictions (e.g., lactose-free) and in vegetarian and vegan foods. Moreover, plant-based proteins are more sustainable as they have a lower carbon footprint [11, 12]. Examples include pea [13, 14] and soy proteins [15], which have been reported for emulsions production.

Aligned with natural emulsifiers, Pickering stabilizers (in particular organicbased colloidal particles) are emerging as promising solutions. Pickering emulsions or particle-stabilized emulsions present high resistance to coalescence and Oswald ripening due to the tight fixation of the particles to the droplets surface [16]. Several food-grade particles have been studied, namely particles based on proteins [17], polysaccharides [18], and protein/polysaccharide complexes [19]. Furthermore, natural emulsifiers from microbial origin such as biosurfactants and bioemulsifiers are also potential alternatives to be explored in food emulsions [20, 21].

This chapter covers a bibliographic review focused on the last 10-years on natural emulsifiers and emulsion technology field. Research and market trends are also highlighted, showing the most relevant natural emulsifier families. Basic concepts concerning emulsion production, classification, and stabilization methods are introduced. A special emphasis is given to Pickering emulsions regarding novel trends in food emulsion systems.

#### **1.1 Bibliometric and market trend analysis**

According to the Research and Markets report, amidst the Covid-19 crisis, the global emulsifiers' market is projected to reach US\$ 6.1 Billion by 2027, growing at a Compound Annual Growth Rate (CAGR) of 4.8% over the forecast period (2020–2027). Particularly, natural emulsifiers' area is estimated to get US\$ 3.3 Billion, recording a 5.4% CAGR [22]. In agreement, the "Global Food Emulsifiers Market 2020-2027 report" from MarketResearch, foresees a high potential for the plant-based emulsifiers in the global food emulsifiers market [23].

Concurrently, scientific literature corroborates the global food emulsifiers report's projections. More than 8,000 documents were found using the terms "natural emulsifier\*" OR "bioemulsifier\*" OR "bio-emulsifier\*" OR "biosurfactant\*" OR "bio-surfactant\*" OR "Pickering emulsion\*" searched in title, abstract, keywords and Keywords plus sections using the Web of Science Core Collection (SCI-EXPANDED), in the 2010–2020 period. Excluding documents with early publication and applying the "Food Science and Technology" filter from WOS, 792 documents were found. By removing 4 documents from 2021 in a final manual screening, 788 documents were analyzed using Biblioshiny app from the Bibliometrix-R package (RStudio) [24] and VosViewer software [25]. The survey was performed on April 25th, 2021.

**Table 1** presents some of the retrieved 788 documents concerning the application of natural emulsifiers or Pickering stabilizers in emulsion formation/stability, *New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*


#### **Table 1.**

*Studies reporting the use of natural molecules and Pickering stabilizers selected from the retrieved 788 documents of the bibliometric search.*

including their use in biocompound delivery systems. Some works regarding the production of bioemulsifiers or biosurfactants by microorganisms were also found [31, 32]. Several studies addressing Pickering emulsions and the use of high-pressure homogenization were identified.

**Figure 1a** shows the wordcloud from Author's Keyword. The higher font size indicates an increased frequency of the keyword. **Figure 1b** also illustrates keyword co-occurrence network analysis; the terms distributed in the same cluster present the higher similarity, in comparison with the terms distributed in different clusters.

"Pickering emulsions" is the most frequent keyword, followed by biosurfactant (**Figure 1**). Other keywords (e.g., whey protein, sodium caseinate, glycolipid, sophorolipids, rhamnolipids, *Quillaja* saponin) appeared in the wordcloud.

These findings substantiate the keyword co-occurrence analysis (**Figure 1**). 93 keywords (Author's keywords) were organized in 9 clusters. The number of occurrences indicates the number of documents where the keyword appears. Each circle represents a keyword with at least 5 occurrences, being their areas proportional to the number of occurrences. The clusters are characterized by different colors and their words can be related.

Some clusters present words associated to recent trends in the area of natural emulsifiers. Clusters 1, 6, 8 and 9 refer to "Pickering emulsions" and other interrelated words, including nanoparticles, Pickering stabilization, and some commonly used Pickering stabilizers such as starch granules, cellulose nanocrystals and kafirin. Clusters 1 and 2 comprise terms related to the rheological properties of emulsions, an important parameter in food applications. The words included in clusters 4 and 5 are associated with microorganisms (e.g., *Pseudomonas aeruginosa; Starmerella bombicola; Bacillus subtilis)* and the biosurfactants they produce (e.g., rhamnolipids; sufactin; sophorolipids). *P. aeruginosa* is a food-borne pathogen and a source of rhamnolipids [33]. *Starmerella bombicola* is a non-pathogenic yeast

#### **Figure 1.**

*(a) Wordcloud from Author's keywords (100 keywords; minimum frequency of 5); (b) keyword co-occurrence network (9 clusters; Author's keywords; number of occurrences 5).*

producing sophorolipids, whereas *B. subtilis* is a non-pathogenic bacteria yielding surfactin [31, 34]. Some of these biosurfactants have been applied in food emulsion systems (e.g., surfactin in O/W food emulsions [20]) due to their high ability to stabilize emulsions, and present antioxidant and antimicrobial properties. However, some aspects, especially safety, require attention as biosurfactants may be produced by pathogenic bacteria [35].

Cluster 7 and 9 are centered in words related to the biocompounds delivery systems, namely bioavailability/bioaccessibility, controlled release, encapsulation and examples of used biocompounds, such as beta-carotene, curcumin, and vitamin E. Clusters 8 and 9 refer to proteins, phospholipids, saponins and polysaccharides, such as whey protein isolate, soy lecithin, *Quillaja* saponin,

*New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

and pectin, respectively. Some of these natural emulsifiers also appeared in the wordcloud analysis, being the most used ones in the food science and technological fields.

In a general overview, the analysis showed the progressive interest in natural emulsifiers due to their relevance for the scientific and industrial communities, as well as for the global market. Moreover, Pickering emulsions are emerging as advanced emulsion technologies within future trends in the food industry.

### **2. Principal natural-based emulsifier groups**

Natural emulsifiers belong to a broad range of chemical families and some main examples are shown in **Figure 2**. Within each family, aspects such as the used natural source or extraction method can lead to different properties. Therefore, the next sections summarize the most relevant families in the area of natural emulsifiers and their contextualization in the field of food applications.

#### **2.1 Phospholipids**

Phospholipids are amphiphilic molecules, and a main constituent of natural membranes. Their structure comprises a hydrophilic head holding a phosphoric acid (H3PO4), combined with a hydrophobic tail composed by one or two non-polar fatty acids. They comprise groups as glycerophospholipids or sphingolipids, with lecithins (glycerophospholipid) assuming an important role. Phospholipids can be obtained from diverse natural sources, including milk, vegetable oils (soybean, rapeseed or sunflower), egg yolk, meat and fish [36, 37]. Specifically, lecithins are known to be good stabilizers for food emulsions, for example the ones derived from soy or egg yolk are applied in mayonnaise, creams, or sauces [38]. Other phospholipid examples include phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidic acid, sphingomyelin. The amphiphilic character of these compounds supports their capacity to stabilize emulsions. Concurrently to their ability to stabilize emulsions

**Figure 2.** *Representative chemical structures for each emulsifier family.* they can act as texturizing agents, thus influencing the organoleptic attributes of the final product [39].

#### **2.2 Saponins**

Saponins are a complex family derived from plants, constituted by triterpenes or steroid aglycones linked to glycosyl derived sugar structures [40]. Usually the aglycones involve pentacyclic triterpenoids with oleanolic acid and the sugars moieties comprise rhamnose, xylose, glucose or galactose [41]. Factors conditioning the composition of saponins are their botanical origin and extraction method. *Quillaja saponaria* Molina is the principal source of saponins, named *Quillaja* saponins, characterized by high contents of quillaic acid groups (hydrophobic) and rhamnose, galactose or glucuronic acids (hydrophylic) [42]. Saponins produce highly stable emulsions, including at the nanoscale, and at relatively low surfactant contents, with promising stability in terms of pH, ionic strength or temperature conditions [40]. Their promising properties avail their use in diverse applications, with examples of food-grade saponins applied in beverages added with flavors or bioactives such as vitamins [43]. More recently, the utilization of saponins was extended to the use of saponin-rich extracts obtained from plant sources [44], by-products and food wastes [40]. Besides the increased costs of using highly pure saponins, they provide weaker functional properties comparatively with extracts, due to the lack of additional bioactive compounds, e.g. polyphenols [45].

#### **2.3 Proteins**

Proteins are molecules resulting from the combination of 21 different amino acids, having diverse properties, including water solubility, which varies depending on their composition [46]. Structurally, the presence of both hydrophobic and hydrophilic amino acids confer an amphiphilic character, allowing them to be absorbed at oil/water interfaces, leading to emulsion stabilization [47]. However, proteins have low surface activity in comparison with conventional emulsifiers. This is attributed to the random distribution of the hydrophilic and hydrophobic groups within the peptide chains, limiting their adsorption. This effect is balanced by the protein film formation around the droplets, leading to stabilization through molecular interactions [48]. Diverse proteins (e.g., whey, casein, soy or faba bean proteins) have been tested in food applications, e.g., emulsions for the controlled release of lutein [49], w-3 oil [50], bioactive hydrophobic compounds [51], fish oil [52, 53] or β-carotene [54]. Their application in final products is still hindered by environmental conditions such as pH, temperature and ionic strength [48]. However, these drawbacks can be surpassed by using more complex formulations, namely by combining proteins with polysaccharides [48] or by chemically modifying the proteins trough grafting with other compounds such as polyphenols [54].

#### **2.4 Polysaccharides**

Polysaccharides are biopolymers composed of monosaccharide units such as glucose, fructose, mannose or galactose, bonded by glycosidic bonds. Their structural rearrangement, i.e., type and number of monosaccharides, type of glycosidic bonds, molecular weight, electrical charge, branching degree, hydrophobicity and the presence of other groups (carboxylate, sulfate or phosphate), rule the polysaccharides functional properties such as solubility, rheology, and amphiphilic character, among others [10]. Their amphiphilicity depends on the presence of hydrophobic (glycolipids) and hydrophilic (hydroxyls) groups, being adsorbed

*New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

at the interface, forming a thick stabilizing layer (e.g., pectins, gum Arabic) [55]. Moreover, non-amphiphilic polysaccharides can contribute to emulsion stabilization due to their thickener role, increasing the viscosity and decreasing oil droplets' motion (e.g., alginates, carrageenan) [56]. Despite the high number of polysaccharides available in nature, only few are authorized as food emulsifiers in EU, namely alginic acid (E400), gum Arabic (E414), pectin (E440), cellulose and chemically modified celluloses (E460 to E469) [57]. Polysaccharides can be obtained from animal, vegetal, microbial fermentation or marine sources (algae), being their properties mostly dependent on the source and extraction process [10].

#### **2.5 Natural based emulsifiers from microbial sources**

Microbial synthetic routes are emerging as valuable sustainable and green alternatives to produce emulsifiers. They generate compounds with low ecotoxicity, biodegradability, stability (pH and salinity) and low critical micellar concentration (CMC), in addition to biological activity, biocompatibility and digestibility [58]. Emulsifiers produced by microorganisms are classified according to their molecular weight. Low molecular weight family includes glycolipids (e.g., rhamnolipids, sophorolipids, trehalose lipids) and lipopeptides (e.g., surfactin, iturin, fengycin) and are referred as biosurfactants. Polysaccharides, proteins, lipoproteins, and lipopolysaccharides belong to the high molecular weight family and are referred as bioemulsifiers [59, 60]. Glycolipids like rhamnolipids and trehalose lipids are mostly produced by bacterial strains like *Pseudomonas aeruginosa*, *Pseudomonas fluorescens*, *Rhodococcus erythropolis*, *Nocardia erythropolis*, *Arthrobacter sp*. or *Mycobacterium sp.* while sophorolipids are generally produced by yeasts (e.g. *Candida bombicola* or *Candida antartica*) or by filamentous fungi like *Aspergillus flavus* or *Rhizopus oryzae* [58, 61]. Lipopeptides can be produced by *Bacillus sp*. *Serratia marcescens* and *P. fluorescens* [58]. Bioemulsifiers such as Emulsan/Biodispersan are commercially available products, being produced by *Acinetobacter spp*., while mannoproteins are commonly obtained from the yeasts *Saccharomyces cerevisiae* or *Kluyveromyces marxianus* [61]. The excellent properties of both microbial derived biosurfactants and bioemulsifiers make them appealing as natural based emulsifiers for foods. Several studies reported the use of glycolipids for fat emulsions stabilization [62, 63], and glycolipids and lipopeptides as rheology modifiers in cookies and muffins dough [64–66]. Other works refer bioemulsifiers (e.g., exopolysaccharides, mannoproteins) as having high potential in aromas emulsification [67]. Nevertheless, the practical application in foods is still limited due to two main factors, their high production costs narrowing the commercial profit, together with the legal regulations that limit the use of compounds produced by microbial strains classified as pathogenic in food applications. Examples include the bacteria genera like *Pseudomonas* and *Bacillus*. In opposition, yeasts like *S. cerevisiae* and *Kluyveromyces lactis*, which are classified as GRAS organisms, are authorized for food applications [68].

## **3. Emulsion technology**

Emulsions are colloidal systems constituted by two immiscible liquids (oil and water), formed in the presence of an emulsifier, and, usually, by applying an energy input. The emulsifier selection is therefore an important step to reach stability. They can be classified based on the hydrophilic region that correspond to ionic structures (anionic or cationic surfactants), change charge with pH (amphoteric surfactants) or present no charged centers (nonionic surfactants) [69]. Among them, nonionic surfactants are often used in food applications because

they are less toxic and less affected by pH and ionic strength changes [70, 71]. The choice of a nonionic surfactant can be based on the hydrophilic–lipophilic balance (HLB) index [72]. This scale (0–20), reflects the changing from hydrophobic to hydrophilic character, that is, a lower HLB value corresponds to a lipophilic surfactant being appropriate to stabilize water-in-oil (W/O) emulsions, whereas a high HLB indicates the ability to stabilize oil-in-water (O/W) emulsions, due to the strong hydrophilic balance [72].

## **3.1 Emulsion classification**

Emulsions can be classified according to their typology and structure. The first refers to the relative distribution of the immiscible phases (oil and water), and the latter refers to the arrangement of the emulsified entities [73]. Considering the typology, they can be classified as simple (O/W and W/O) or double (oil-in-waterin-oil (O/W/O), and water-in-oil-in-water (W/O/W)) emulsions (**Figure 3**). Examples of O/W emulsions in food systems include products such as milk, sauces, beverages, yogurts, ice-creams, and mayonnaise [74]. W/O emulsions are not so frequent but can be found in butter and margarine [73, 75]. For double emulsions, W/O/W are the most used systems due to their ability to generate reduced-fat products, when compared to O/W emulsions. Moreover, they can serve as base systems to encapsulate and control the release of sensitive water-soluble compounds, such as flavors or bioactive ingredients [16, 75, 76].

Regarding structure, emulsions can be classified as macroemulsions (usually called emulsions), nanoemulsions, or microemulsions. These systems present specific physicochemical properties that influence their range of applications [71]. Emulsions and nanoemulsions are thermodynamically unstable systems because their free energy is higher than the one of the individual phases [74, 77]. Thus, considering that all systems tend to their lowest energy state, phase separation will occur. However, due to their kinetic stability, they may remain in a metastable state for a considerable period of time, delaying the phase separation phenomenon. The kinetic stability is governed by two mechanisms, namely the energy barriers between the two states (emulsified and separated phases) and mass transfer between the phases. Therefore, high energy barriers and slow mass transfer processes delay phase separation [78]. By contrast, microemulsions are

**Figure 3.** *Typology of simple and double emulsions.*

#### *New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

thermodynamically stable systems because their free energy is lower than the one of separate phases. Thus, they can be formed spontaneously under particular compositions and temperature conditions. In practice, some energy input is needed due to the existence of kinetic energy barriers [71]. Regarding the droplet size, nanoemulsions and microemulsions present droplet sizes <200 nm, whereas emulsions hold sizes between 200 nm and 100 μm [16, 71].

Nanoemulsions and microemulsions are optically transparent or slightly turbid due to their small droplet size, being valuable for applications requiring transparency, such as soft drinks [79]. Comparatively with nanoemulsions, microemulsions require a higher emulsifier content, have a lower particle size, and droplets can assume a non-spherical shape, feature that can be used to differentiate the two systems. Emulsions are typically turbid to opaque and are used in creamy systems such as dairy products [80]. **Table 2** provides some application examples for each system addressing natural emulsifiers.


**Table 2.**

*Food applications of emulsions, nanoemulsions and microemulsions using natural emulsifiers.*

### **3.2 Stabilization mechanisms**

Emulsions are thermodynamically unstable mixtures, characterized by the presence of at least two immiscible phases and an emulsifier that, when provided with enough mixing energy, are able to maintain stability over time [98]. The role of the emulsifier is essential to assure stable long-term properties. In general, emulsifiers are active surface substances, enabling their positioning at the oil– water interface, reducing the interfacial tension, hindering (or delaying) aggregation phenomena [99]. Typically, the hydrophilic part of the emulsifier is located in the aqueous phase, while the hydrophobic tail remains enclosed in the oil phase [82, 100]. During emulsion formation, the surfactant molecules require time to move to the interface, forming a layer to reach the interfacial tension equilibrium, a phenomenon related with their adsorption kinetics [82]. This pattern is dependent on emulsifiers' nature, taking from minutes (e.g., some saponins) to hours (e.g., some proteins), besides being dependent on environmental conditions (e.g., pH, temperature) [82]. To note that, even emulsions are commonly stabilized by a monolayer structure around the droplets, multilayer structures can also be formed. The multilayer pattern favors the electrostatic and steric repulsion of the droplets, improving stability while providing additional protection to the internal phase [16].

The emulsion stabilization mechanism can differ depending on the nature of the used surfactant. In this context four principal stabilization mechanisms are known, namely electrostatic repulsion, steric repulsion, Marangoni-Gibbs effect, and thin film stabilization mechanisms [101]. The electrostatic repulsion is related to ionic emulsifiers and consists on the formation of an electrical double layer at the droplet's interface, hindering their approximation. Steric repulsion is characteristic of nonionic and/or polymeric emulsifiers, and droplet's distance is kept due to the adsorption of the hydrophobic segment by the oil phase [101]. The Marangoni-Gibbs effect preserve emulsions' structure through the deformation of adjacent droplet's surface, avoiding their outflow, whereas the thin film stabilization mechanism avail the stability of the emulsion by generating a rigid and viscoelastic film, preventing droplets from destabilization effects [101].

Other factors can condition emulsion's stabilization mechanism, including the emulsifier content, the oil to water ratio or the preparation conditions (pH or temperature). For example, some phospholipids can have no charge at neutral pH, turning into anionic at acidic media, promoting molecule's swelling at the interface [100]. Moreover, the surfactant concentration can have also impact, e.g., sunflower lecithin in O/W emulsions, at low contents, create a layer surrounding the oil droplets, while at higher concentrations, the stabilization mechanism changes, producing, concurrently, liposomes that might destabilize the emulsion [10]. Considering amphiphilic polymers, when they are used as emulsifiers, they become positioned at the interface, just like the small molecules, but their ability to create intermolecular interactions can provide additional stabilization effects. Their effect on viscosity can also provide a positive stabilization effect [102]. The high hydrophilicity of most polysaccharides can difficult their emulsifier role, if considering the importance of the emulsifiers' hydrophilic/lipophilic character to interact with both phases. This constraint can be overcome by either chemical or physical strategies [103]. Namely, the suitability of anchoring hydrophobic groups into the polysaccharide structure can equilibrate the hydrophilic/lipophilic balance, that is the hydrophobisation of emulsifier's surface. Otherwise, alternative approaches imply the mixture of the polysaccharides with other polymers (co-surfactants) to favor the hydrophilic/ lipophilic equilibrium and stabilization role.

*New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

## **3.3 Production methods**

Food emulsions can be produced using several methods, classified as low-energy and high-energy processes, as represented schematically in **Figure 4**. The selection of the most appropriate method and respective equipment is based on the volume to process, characteristics of the initial mixture, emulsion's physicochemical properties, droplet size, and process costs [104]. In **Table 3** a survey of recent works dealing with emulsion production trough different methods and using natural emulsifiers in their pure form or compounded with synthetic emulsifiers is presented. Moreover, their potential to encapsulate bioactives for food industry applications is also described.

Low-energy methods comprise, spontaneous emulsion, and emulsion phase inversion (e.g., phase inversion composition and phase inversion temperature), which occur due to environmental or composition changes namely temperature, pH, and ionic strength of the formulation [104]. Low-energy approaches are more cost effective than high-energy methods. However, they are limited to certain oils

**Figure 4.**

*Schematic representation of the emulsification process through high- and low-energy methodologies.*


**Table 3.**

*Studies applying different productive methods using natural emulsifiers or natural/synthetic blends to form emulsions and/or to encapsulate biocompounds for food industry applications.*

#### *Natural Food Additives*

#### *New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

and emulsifiers, requiring also large amounts of surfactants, which is not desirable for many food applications [71]. In the work reported by Komaiko et al. [36], spontaneous emulsification lead to emulsions with large droplet size (>10 μm), comparatively with those produced by high-energy methods (<10 μm). The authors concluded that natural emulsifiers can be used in SE emulsions for applications where fine droplets are not essential (**Table 3**). By contrast, Mayer et al. [105] concluded that it was not possible to produce nanoemulsions using natural emulsifiers by the emulsion phase inversion method. These limitations imply that even natural-based emulsions can be prepared through low-energy methods, highenergy approaches are needed when natural emulsifiers are used.

High-energy methods generate intensive forces promoting the water and oil phases disruption and their subsequent mixture. High-shear homogenizers are the most used equipment's for producing emulsions in the food industry. They consist on a rotor-stator or stirrer device able to mix the components at high speeds. Usually, large droplets are produced using this approach (1–10 μm) in comparison to alternative high-energy methods. High-pressure homogenization is also widely used in the food industry, being more effective to reduce the droplet size of a preemulsion. Generally, this coarse pre-emulsion is produced by high-shear homogenizers, then subjected to the high-pressure homogenization process. The equipment consists of a high-pressure pump (3–500 MPa) to pass the coarse emulsion through a narrow homogenizing valve, generating intensive disruptive forces (shear and cavitation), breaking down the droplets into smaller ones [80, 81].

Many studies have been conducted using two high-energy sequential methods (high-shear and -pressure homogenizers) to produce emulsions/nanoemulsions with natural emulsifiers [111–113]. Flores-Andrade and co-workers performed a study with soy lecithin, whey protein concentrate (WPC) and gum Arabic as natural emulsifiers, and paprika oleoresin as the oil phase. The coarse emulsion was produced by a high-speed homogenizer, then treated in a high-pressure homogenizer. O/W nanoemulsions were produced, being WPC more effective to form small droplets (d < 150 nm) than the other tested emulsifiers [92].

Microfluidization is the most effective method for producing emulsions with fine droplets (d < 100 nm). This approach is based on feeding the fluid into the homogenizer, which consists of a mixture chamber with two channels. Intensive disruptive forces are generated when these two fluid streams collide at high speed, breaking larger droplets and intermingling the fluids [3]. As the high-pressure homogenizers, microfluidizers were used after preparing a pre-emulsion by highshear mixers [42, 114]. Ultrasound technique uses high-intense ultrasonic waves, generating intense shear and pressure gradients. The droplets are disrupted mainly by cavitation and turbulent effects [99, 115].

Currently, high-energy approaches are commonly used in the food industry due to their large-scale production capacity and the possibility to process a wide range of raw ingredients [71]. Although several high-energy emulsification devices are available, high-shear and pressure homogenizers, microfluidizers and ultrasound equipment's are the most used in the production of natural emulsifiers-based emulsions.

#### **3.4 Emulsion stability**

Emulsion stability is an important parameter indicating its ability to resist physicochemical changes over time [116]. For food emulsions, the required stability varies according to the intended final application. For example, short-term stability of minutes to hours, is enough for intermediate food emulsions such as cake batter and ice cream mixtures, while long-term stability is required for long shelf-life

#### **Figure 5.**

*Common types of instability phenomena in emulsions.*

products, including mayonnaise and salad dressings [117]. For the latter ones, the development of effective strategies to retard emulsion destabilization implies the identification of the main mechanisms leading to this effect [73].

Emulsion instability can occur due to physical and/or chemical processes. The physical instability is responsible for modifying the emulsion droplets spatial distribution and structure, including gravitational separation (creaming/sedimentation), flocculation, coalescence, and Ostwald ripening phenomena (**Figure 5**). These effects depend on the emulsion composition and structure, besides the storage conditions, namely temperature variation and mechanical stirring [74, 116]. Moreover, the physical phenomena are interrelated and can influence each other during emulsion storage [77].

Gravitational separation is driven by density differences between the droplets and the continuous phase. The droplets are subjected to gravitational forces tending to accumulate in the top (creaming) or in the bottom (sedimentation) of the system. Most edible oils present densities lower than water, favoring creaming in O/W emulsions, whereas sedimentation is usually observed in W/O emulsions [116]. Considering the impact of gravitational forces in the large droplets, the separation usually occurs for emulsions with droplet sizes higher than 100 nm or in a final stage of a sequence of instability phenomena [116]. By contrast, for lower droplet sizes, e.g., nanoemulsions, Brownian motion dominates over gravitational forces. Thus, reducing the droplet size is a suitable strategy to retard gravitational separation, with the emulsifier playing an important role to effectively reduce droplets' size [2, 74]. Furthermore, the emulsifier' layers tend to minimize the density difference between the emulsion phases, thus reducing the velocity of gravitational separation. Other strategies include modifying the rheology of the continuous phase or increasing the concentration of the droplets [74, 116].

Ostwald Ripening consists of the increase of the droplets size due to the diffusion of small droplets into larger ones, effect driven by their solubility in the continuous phase. This effect is promoted when the droplet's size decreases [73], being also influenced by the emulsifiers' properties. Namely, Ostwald Ripening can be retarded by decreasing the interfacial tension of the phases, favored when small-molecule surfactants are used or when using emulsifiers able to form rigid shell around the droplets. By contrast, emulsifiers prone to solubilize the oil and water phases through the formation of colloidal structures (e.g., micelles) accelerate the Ostwald Ripening [2].

Flocculation and coalescence mechanisms are related to droplets aggregation, effect leading to droplet size increase [74]. In flocculation the association of at least two droplets in an aggregate occurs, whereas in the coalescence, the droplets merge into a larger one [77]. Both phenomena are highly dependent on the selected emulsifier [77, 116], namely their nature and colloidal interactions' capacity [2].

*New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

## **4. Pickering emulsions**

Pickering emulsions are defined as systems stabilized by solid colloidal particles adsorbed at the oil–water interface in a practically irreversible process, creating a coating around the droplets, either in the form of a single or multiple layer, generating a strong steric barrier providing high stability [118]. In the context of Pickering emulsions, the search for natural-based particles is currently a hot topic to face market demands for novel clean label products (absent of emulsifiers) [119]. Pickering emulsions (**Figure 6**) are raising high interest in the recent years. They are characterized by a long-term stability and have green connotations due to the absence of conventional emulsifiers. These attributes comply with the recent trends of food industry towards the use of sustainable and healthy technologies [16]. The stability of Pickering emulsions is related with the intrinsic properties of the oil and water phases (e.g., type, oil/water ratio, pH, ionic strength) and of the particle stabilizers (e.g., wettability, particle morphology, size and concentration). Particles presenting a contact angle (θ) below 90° are generally suitable for preparing O/W emulsions, whereas θ values greater than 90° indicate good stabilizers for W/O emulsions. At 90°, the particle is immersed equally in both phases [120].

Regarding natural-based particles, three main typologies of stabilizers can be used, namely nanoparticles, microgels and fibrils. Examples include protein derived stabilizers, namely nanoparticles based on corn zein, and colloidal particles of kafirin and gliadin [118, 121–123]. Although many polysaccharides have high hydrophilic character, some can include hydrophobic side groups (e.g., beet pectin and modified starch) or even active proteins attached to the surface (e.g., gum Arabic) [120], offering potential to act as Pickering stabilizers. Other polysaccharides widely used to produce Pickering bionanoparticles include chitin, chitosan and cellulose. To overcome particle's limitations as Pickering stabilizers, the formation of complexes has been also proposed, namely complexes such as polysaccharidepolysaccharide, protein–protein, and polysaccharide-protein [124]. Examples include zein-xanthan [125], and tea water insoluble proteins/κ-carrageenan complexes [126].

In the context of the recent trends in Pickering emulsions, research aiming at finding new biological particles, the use of high internal phase emulsions (HIPPE),

#### **Figure 6.**

*Schematic representation of a Pickering emulsion putting in evidence the particle stabilizers where* θ *represent the contact angle.*

and the development of bio-based films from Pickering emulsions are becoming topics of high interest for the development of novel food applications. **Table 4** presents an overview of recent works dealing with the preparation of Pickering emulsions based on novel biological particles together with the description of the main results envisaging potential food applications.

HIPPEs are characterized by having a high volume fraction of internal phase (generally higher than 74%), together with relatively low particles concentration resulting in an extremely compacted droplet's structure [140]. HIPPEs are becoming a novel approach of increasing interest in the food industry, since it combines


#### **Table 4.**

*Examples of bionanoparticles as Pickering stabilizers. All the systems are of O/W type.*

#### *New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

diverse advantages, namely a semi-solid texture with the ability to encapsulate high amounts of bioactive compounds [141]. HIPPEs allow to control the droplet size distribution, manipulate the morphology and rheological properties, generally presenting enhanced stability against physical, chemical and microbiological stresses [142]. They are positioned as extremely promising substitutes for foods such as margarine, mayonnaise or ice creams [143, 144]. For example, Liu et al. studied wheat gluten as stabilizer in a HIPPE to develop a novel mayonnaise substitute [145]. They obtained excellent results concerning texture and sensory attributes when compared with commercial products.

Bio-based films made from hydrophilic particles added with hydrophobic compounds is another emerging approach in the scope of new applications developed from Pickering emulsions [146]. These strategies provide the ability to improve the stability of the base materials (hydrophilic), in addition to facilitate the combination with hydrophobic materials (e.g., waxes, fatty oils and oils) leading to systems with enhanced moisture barrier properties [147].

## **5. New trends in food emulsion systems**

The wide variety of emulsion-based systems using natural emulsifiers makes their applicability attractive for various products, particularly in the food industry. The nature and function of emulsifiers, and the formed emulsion type (e.g., nano/ micro-scale, simple or double character) can tailor appearance, sensorial characteristics, and attractiveness of foods. Among their diverse functions, the increasing use of emulsions as functionality carriers should be highlighted. In fact, recent works have demonstrated their potential and versatility for the encapsulation of flavors, and to protect and deliver specific bioactives in foods or beverages, helping to strengthen nutritional balances, and enabling the production of reduced-fat products. A summary of examples addressing new trends of emulsion-based products with potential in the food industry are included in **Table 5**, with some highlighs provided next.

Lopes Francisco et al. [149] reported an emulsifying system with encapsulation potential based on commercial pea and soy proteins. The work involved the encapsulation of an orange essential oil rich in d-limonene using a O/W emulsion followed by spray drying to obtain powder microparticles. It was demonstrated the ability of pea and soy proteins to act as emulsifiers in the encapsulation of orange essential oil, getting a slightly higher efficiency if using soy protein as the natural emulsifier. These promising results can help consolidate a platform aiming at developing new protective systems to encapsulate flavors for foods, complying with the increasing demand from this industrial sector for naturalbased systems.

At the nanoscale, Flores-Andrade et al. [92] reported the preparation of O/W nanoemulsions by high-pressure homogenization, using amphiphilic biopolymers to stabilize paprika oleoresin, namely whey protein, gum Arabic, phospholipids, and soy lecithin. The results demonstrated the effective oil encapsulation, preserving carotenoids (e.g., lipophilic colorants) from chemical degradation, besides positioning this strategy as an attractive route to design new protective and delivery carriers for bioactive compounds aimed at food and/or beverage products.

The potential of double emulsions was also demonstrated by Cetinkaya et al. [152] that evidenced the reduction of the saturated fat content in O1/W/O2 emulsions prepared by fat crystallization according to a two-stage process. Firstly, the


#### **Table 5.**

*Applications of natural-based emulsifiers in food industry.*

primary O1/W emulsion was prepared using sunflower oil and xanthan gum and gelatin as emulsifiers, which was then stabilized in a second oil phase (palm oil), resulting in a structured O1/W/O2 system. Microstructure examination revealed that the accumulation of fat crystals at the interface contributed to stabilize the internal water phase containing the encapsulated sunflower phase. These complex structures showed potential to directly encapsulate hydrophobic oils and act as texturizing reduced-fat agents, which might be of particular interest for the edible oils industry.

## **6. Conclusions**

This chapter presents an up-to-date overview of current trends in natural emulsifiers and their application in emulsion technology directed to food applications. For this purpose, first, the evolution of food emulsifiers' scenario over the last 10 years was analyzed through the Bibliometrix-R package (RStudio) and VosViewer software. This analysis indicated a clear driving force towards using natural emulsifiers and the re-emerging importance of the Pickering emulsions. These facts are expected to impact the market growth following the prospectus of available market analysis. The six main identified families of natural emulsifiers

*New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

were phospholipids, saponins, proteins, polysaccharides, emulsifiers from microbial sources and Pickering stabilizers. Some of them already find extensive use in practical food applications. However, others, mainly natural-based emulsifiers from microbial sources and Pickering stabilizers, despite their high potential, are still needing research investment and regulation clarification (e.g., related to the use of nanoparticles and the use of microbial strains classified as pathogenic in foods). From a technological perspective, the main concepts related to the typology, production methods, stabilization mechanisms, and instability phenomena were presented. Highlighting the increasing interest in Pickering emulsions, a summary of the most recent applications of these systems, including the so-called HIPPEs and their advantages in reduced-fat products development, was provided. To conclude, an analysis of current trends in food emulsion-based products was discussed, putting in evidence the emulsions increasing role as delivery systems of bioactives to support innovative fortified foods advances and the increasing interest in systems based on double emulsions, which provide the opportunity to combine bioactives of different nature. Overall, the field of natural-based emulsifiers combined with the new trends in emulsion technology can, hopefully, be the basis of a new generation of healthy and nutritious food products.

## **Acknowledgements**

CIMO (UIDB/00690/2020) and AL LSRE-LCM (UIDB/50020/2020) funded by FCT/MCTES (PIDDAC). National funding by FCT, P.I., through the institutional scientific employment program-contract for Arantzazu Santamaria-Echart and Isabel P. Fernandes. FCT for the Research grants (SFRH/BD/148281/2019 of Samara C. da Silva, and SFRH/BD/147326/2019 of Stephany C. de Rezende). GreenHealth project (Norte-01-0145-FEDER-000042).

## **Conflict of interest**

The authors declare no conflict of interest.

*Natural Food Additives*

## **Author details**

Arantzazu Santamaria-Echart1 , Isabel P. Fernandes1 , Samara C. Silva1,2, Stephany C. Rezende1,2, Giovana Colucci1 , Madalena M. Dias2 and Maria Filomena Barreiro1 \*

1 Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, Bragança, Portugal

2 Laboratory of Separation and Reaction Engineering – Laboratory of Catalysis and Materials (LSRE-LCM), Faculdade de Engenharia, Universidade do Porto, Porto, Portugal

\*Address all correspondence to: barreiro@ipb.pt

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*New Trends in Natural Emulsifiers and Emulsion Technology for the Food Industry DOI: http://dx.doi.org/10.5772/intechopen.99892*

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## Section 3
