Essential Oils and Food Science Technology

#### **Chapter 4**

## Essential Oils as Antimicrobial and Food Preservatives

*Mamdouh S. Serag, Reham A. Elfayoumy and Marwa T. Mohesien*

#### **Abstract**

Essential oils (EOs) are secondary metabolites produced by aromatic and medicinal plants. These oils have a wide range of applications in the culinary, perfume, antimicrobial and food industries. Because of several reported side effects of synthetic oils, the use of essential oils as antimicrobials and food preservatives is a source of concern. For cereals, grains, pulses, fruits, and vegetables, essential oils have the potential to be employed as a food preservative. When compared to synthetic compounds, EOs derived from safe natural sources and are effective for human health. This chapter will shed light on some medicinal plants that are rich in essential oils, as well as their antimicrobial properties. Because essential oils are rich in a number of active ingredients [e.g., terpenes, terpenoids, carotenoids, coumarins, curcumins] that are important in food industry, they have strong antimicrobial and food preservation. As a result of the diverse properties of essential oils, they can be used in a natural, safe, eco-friendly, cost-effective and renewable manner. Examples of some foodborne diseases will also be highlighted.

**Keywords:** essential oils, antibacterial, antifungal, bioactivity, foodborne diseases, food preservatives

#### **1. Introduction**

Essential oils [EOs] are a volatile mixture of chemical molecules with a strong odour that is extracted from aromatic and medicinal plants. Steam or hydro-distillation or Soxhlet extraction [solvent extraction or continuous extraction] procedures are used to extract EOs from aromatic and medicinal plants [1]. Essential oil is a liquid that is extracted from flowers, leaves, bark, stems and roots by steam or water distillation. Essential oils are not at all oily-feeling, despite the word 'oil'being used. The majority of essential oils are clear, but some, like patchouli, orange and lemongrass, are amber or yellow. They are rich in chemicals like phenols, monoterpenes and ketones. These plant chemicals are called plant 'essences 'referring to the fact that they carry some of the plant's natural ability to resist bacteria and fungi. These are the same chemical molecules that have been isolated or synthesised by the pharmaceutical industry to make drugs.

Commercial antimicrobial treatments had been used to prevent food deterioration or contamination since ancient times. As a result of consumer concerns about synthetic preservatives, natural antimicrobials such as essential oils are receiving more attention. Essential oils and their components from aromatic and medicinal plants had been shown to have antibacterial, antifungal and food preservation properties against a variety of pathogenic microorganisms [2].

Essential oils are hydrophobic liquids of aromatic compounds that are volatile and oily in nature and present in various plant parts such as flowers, leaves bark, stem, root and seed. Many plant essential oils are useful as a flavour or aroma enhancer as food additives. Applications of essential oil that can act as antimicrobial agents are growing due to the broad range of activities, natural origins and are safe. Currently, essential oils are frequently studied for their antibacterial and antifungal [3] as well as for their use as food preservatives [4].

Essential oils are considered to be secondary metabolites and important for plant defence as they often possess antimicrobial properties [5]. The antibacterial properties of secondary metabolites were first evaluated using essential oil vapours [6]. Since then, essential oils or their components had been shown to not only possess broad-range antibacterial and antifungal properties [7, 8].

Wherever you buy essential oils, the quality might vary dramatically from one dealer to the next. Despite the fact that they are all essential oils, they all do not have the same medicinal potential. Furthermore, the price charged does not always reflect the quality of the vendor's oils. There are a few:


The information of this chapter was extracted from the accessible international electronic databases [PubMed, Springer, Science Direct, Wiley and Google] and books by keywords were namely: antibacterial, antifungal, bioactivity, essential oils, foodborne disease, food preservative properties.

The major aim of this chapter highlights the use of essential oils and their antibacterial, antifungal and food preservative properties in controlling fungi associated with food commodities. Some food-borne diseases also will be discussed.

#### **2. Essential oils of some medicinal plants**

#### **2.1 Lemon essential oil**

Lemons are one of the most popular citrus fruits in the world, and they are often used in cooking since they are high in vitamins. It also gives food a pleasing flavour and scent. Lemon oil's stimulating, soothing, carminative, anti-infection, astringent, detoxifying, antiseptic, disinfecting, sleep-inducing and antifungal characteristics contribute to its health advantages. The antibacterial chemical

limonene, which belongs to the terpenes [monoterepenes] group, is found in Lemon essential oil.

Lemon oil [citrus lemon] includes d-lemonene chemicals, which have been researched for their impact on immunological function, lymphatic, circulatory, and digestive systems. It has antibacterial properties and can help white blood cells, phagocytes, and lymphocytes combat infection [9].

#### **2.2 Ginger essential oil**

As a member of the Zingiberaceae family*, Zingiber officinale Rosc. [ginger]* is widely used as a spice or medicinal plant in folk and traditional medicine. Rhizomes, the therapeutic portion of ginger, are utilised in traditional medicine to cure a variety of diseases [10]. It is a volatile substance extracted by distillation of unpeeled rhizome of *Z. officinale* Roscoe plant. The essential oil of ginger has a strong, warm and spicy aroma. Its colour is clear to light amber, and its consistency becomes thicker with age and exposure to air. *Z. officinale* is well known for its medicinal and culinary properties. As turmeric and cardamom, ginger also belongs to the family of Zingiberaceae.

Neroli, clove, black pepper, rose [Rosa alba], turmeric, angelica, spikenard, cardamom, clary sage, sweet marjoram, fennel, jasmine, grapefruit, coriander seed, lemongrass Analgesic, antibacterial, anti-emetic, anti-inflammatory, antioxidant, antispasmodic, antitussive, aperitif, aphrodisiac, deputative, stimulant, laxative, febrifuge, digestive, expectorant, immune-modulatory, rubefacient, stomachic and sudorific qualities are all found in ginger oil [11].

#### **2.3 Peppermint essential oil**

When dispersed in the air, peppermint is one of the most effective essential oils for destroying respiratory tract pathogens. It works well as a topical application as well. Peppermint menthol is increasingly commonly found in sports creams and chest rubs, such as Halls Mentholyptus cough drops. Although the oil is effective at opening sinus passages, it should be used with caution in this regard.

Peppermint oil should be a part of every traveller's first aid kit. It can work wonders for motion sickness and general nausea for some people. An excellent digestive tonic, peppermint essential oil can soothe many stomach complaints. For the traveller, its effectiveness in calming motion sickness can be of great help.

In addition, Peppermint oil had been demonstrated to be useful in lowering the symptoms of irritable bowel syndrome, a painful disorder of the intestines, in at least eight controlled investigations. Peppermint is deliciously stimulating to the mind, brightening and sharpening mental attention in addition to supporting the digestive system.

With all of these additional advantages, peppermint is an effective antimicrobial [12].

#### **2.4 Rosemary**

Rosemary (*Rosmarinus officinal* is L.) is a valuable essential oil plant from the Lamiaceae family. According to the evidence found by anthropologists and archaeologists, rosemary, was used in medicine and food industry [13].

Rosemary is a popular spice and medicinal herb all over the world. Rosemary is usually regarded as one of the spices with the highest antioxidant capacity among

natural antioxidants. Rosemary essential oils have antibacterial and antifungal properties. It is often used as a food preservative and condiment [14].

#### **2.5 Thyme**

Thymol is a natural volatile monoterpenoid phenol that is the main active ingredient of oil extracted from species *Thymus vulgaris* L., commonly known as thyme, and other plants such as *Ocimum gratissimum* L. and *Origanum spp.* L. Thyme Oil is one of the most antiseptic essential oils and is high in antioxidant rating. Thymol, a potent antibacterial, is the primary component of thyme oil. Aromatherapists are well aware that thyme essential oil is one of the most powerful antibacterial essential oils available. Thymol's antibacterial and antifungal properties had been well reported [15].

Thyme essential oils showed some of the strongest killing power against antibiotic-resistant bacteria, according to studies at the Western Infirmary, Glasgow, UK. Thyme oil kills the anthrax bacillus, the typhoid bacillus, meningococcus and the agent responsible for tuberculosis and is active against *Salmonella* and *Staphylococcus* bacteria.

#### **2.6 Clove essential oil**

*Syzygium aromaticum L.* is a member of the Myrtaceae family*,* which includes the myrtle, *Eucalyptus* and *guava* families, and has around 3000 species and 130–150 genera. Clove is a fragrant flower that is grown in Madagascar, Sri Lanka, Indonesia and China [16].

Clove may also be referred to as Clove Tree, Clove Bud, Clove Stem, Tropical Myrtle, Zanzibar Redhead, Cengkih, Chengkeh, Chingkeh. It is typically processed using steam- or hydro-distillation as a method for extracting oil from the flower buds, leaves and stems.

Clove oil comes from the flower buds and leaves of *S. aromaticum* also known as *Eugenia caryophyllata* tree. It has a strong spicy scent. It has an analgesic and stimulating effect. Clove stem and leaves essential oils are also available, however, due to its composition and aroma, essential oil produced from the buds is often preferred.

Clove bud essential oil contains up to 85% eugenol, a phenol that contributes significantly to the scent, medicinal effects and safety precautions. Clove buds essential oil also contains a variety of additional compounds, including the sesquiterpene B-caryophyllene, the esters Eugenyl acetate and B-caryophyllene [2].

#### **2.7 Mustard essential oil**

Mustard essential oil, which is frequently confused with mustard oil, is distilled from mustard seeds. Mustard essential oil is also known as mustard volatile oil. The essential oil includes 92 percent allyl isothiocyanate, the chemical that gives mustard its strong flavour. This allyl isothiocyanate, as well as key fatty acids including oleic acid, linoleic acid and erucic acid, contribute to mustard essential oil's lengthy list of medical properties [17].

Over the years, mustard oil had a mixed reputation in many regions of the world. It is utilised as an edible oil there and is believed to be highly healthful, although it is frequently considered poisonous, irritating and unfit for eating in the rest of the globe [18].

Mustard essential oil is one of the most potent essential oils available, and it can be used to cure a variety of diseases. This oil, which is extracted from the black seeds of mustard using the steam distillation method, had a variety of therapeutic characteristics that can help with a variety of health problems [19].

#### **3. Anti-bacterial activity of essential oils**

Pathogenic bacteria reduce the quality and quantity by 20–40% of the total harvest every year in grains, seeds, fruits and vegetables during cultivation, transportation and storage. *Clavibacter michiganensis*, *Pseudomonas syringae*pv, tomato, *Pseudomonas solanacearum, Pseudomonas cichorii*. Such bacteria cause substantial losses. There are many essential oils that had been evaluated for their potential for antibacterial activity against these pathogenic bacteria [20].

Gram-negative bacteria are generally more resistant to essential oils than Grampositive bacteria. Gram-negative bacteria have hydrophilic lipopolysaccharides [LPS] in their outer membranes work as a barrier to macromolecules and hydrophobic chemicals, allowing them to tolerate hydrophobic antimicrobial substances such as those present in essential oils [21].

#### **4. Anti-fungal activity of essential oils**

Fungi can degrade food commodities such as grains, seeds, fruits and vegetables by producing mycotoxins, and they can make food unsafe for human consumption by lowering nutritional value [4]. Foodborne fungal infections and their toxic metabolites, according to the FAO, can cause qualitative and quantitative problems. Quantitative losses of up to 25% of total agricultural food commodities throughout the world [21].

Food quality, colour and texture are all reduced as a result of fungal infection in food commodities, as are the nutrients contained and the physiological aspects of food commodities. Fungi can create mycotoxins during infection, which can cause famines in underdeveloped nations [22].

Food contamination by *Alternaria, Aspergillus, Penicillium, Fusarium,* and *Rhizopus spp.* is an important issue in terms of moulds because of the associated health risks and foodborne diseases [4].

Essential oils have antifungal properties which are linked to the breakdown of fungal hyphae caused by mono- and sesquiterpene-molecules in the essential oils. Essential oils also increase membrane permeability, which means they can dissolve in cell membranes and produce swelling, limiting membrane function. Furthermore, essential oils' antifungal effect is due to their lipophilic feature, which allows them to enter cell walls and impact enzymes involved in cell-wall production, causing fungus to change their morphological traits [23].

#### **5. Value of essential oils in food preservation**

Essential oils have been successfully used in the preservation of food commodities in order to extend shelf life in recent years. Various researchers have employed essential oils, either in pure or formulation form, to extend the shelf-life of food

commodities in a variety of storage containers, including those made of cardboard, tin, glass, polyethylene, or natural textiles, with positive results [4]. Essential oil constituents like citral, citronella, citronellol, eugenol, farnesol, and nerol among others, have been shown to protect chilli seeds and fruits from fungal infection for up to 6 months [24]. *Ageratum conyzoides* essential oil successfully stopped blue mould from destroying mandarins and extended their shelf life by up to 30 days [4].

Essential oils from *Cymbopogon nardus, C. flexuosus* and *Ocimum basilicum* were observed that could significantly control anthracnose in bananas and increased banana shelf-life by up to 21 days. For up to 3 weeks, *Cymbopogon flexuosus* essential oil [20 L/mL] can preserve *Malus pumilo* fruits from decaying. The use of *Cymbopogon pendulous* essential oil as a fumigant increased groundnut shelf-life by 6–12 months [25, 26], thus proving to be more effective than *Parkia roxburghii* essential oil. These differences in efficacy of essential oils may be related to the use of oils from different plant species, as well as to their chemical composition, dose level, and storage container type [25, 26].

Thyme (*Thymus capitate*) [0.1%] and Mexican lime (*Citrus aurantifolia*) [0.5%] oil reduced disease incidence in papaya fruit whereas, cinnamon [0.3%] oil increased banana storage life by up to 28 days and reduced fungal disease incidence in banana [27].

#### **6. Foodborne diseases**

The definition of food spoilage can be interpreted as the process in which food deteriorates to the point in which it is not edible to humans, this occurred by many spoilage microorganisms [bacteria and fungi], which by many reactions change the composition of food and deteriorates its texture, odour, colour and taste which make it unfit for human consumption [28].

Food diseases or food spoilage are widespread health problems and a major cause of the reduction in economic productivity and human lives around the world [28]. Food poisoning and spoilage are two different things, which affect the final quality and safety of foods. Food poisoning can be also referred to as food-borne illness. Many different forms of food-borne pathogens, such as bacteria and fungi, cause it when people eat contaminated food. Foodborne infections have become a major problem in the modern world since packaged food consumption has risen dramatically. Pathogens that penetrate packaged foods have a higher chance of surviving, which must be monitored. For this reason, antimicrobial chemicals are applied to food or packaging materials, either alone or in combination [28].

Foodborne infections are caused by pathogenic bacteria, fungus, and parasites infected [29]. Food safety is a well-known problem worldwide. This problem affects hundreds of millions of people who are injured by contaminated or spoiled food. 'One of the most widespread health concerns and a major cause of productivity loss and bad impact on human health, 'according to the World Health Organisation [28].

Intoxication, infection and toxic infection are three types of food contamination. Intoxication refers to the production of toxins after ingestion of harmful microorganisms in food; the microbe that produced and excreted the toxic waste products into the food may be killed, but the toxin they produced causes illness or digestive upset; toxic infection refers to the production of toxins after ingestion of harmful microorganisms in food; food infection is the other type of foodborne illness; It is caused by eating food that contains certain types of live microbe which are present in the food,

#### *Essential Oils as Antimicrobial and Food Preservatives DOI: http://dx.doi.org/10.5772/intechopen.103000*

once the food is consumed, the bacterial cells themselves continue to grow and illness can result. Symptoms of food poisoning are headaches, vomiting, nausea, diarrhoea and dehydration, and these symptoms can be out of control which can be fatal many times.

Consumers are increasingly concerned about the rising number of illnesses linked to harmful and spoilage microbes found in food. Food-borne infections affect millions of people every year all over the world, and they can vary from minor irritations to life-threatening conditions. Clinical microbiology laboratories play a critical role in the detection of these illnesses by identifying and reporting infections to public health officials, who then utilise the information to track down food-borne outbreaks [30]. According to the Center for Disease Control and Prevention [CDC], 76 million cases of food-borne disease occur in the United States each year [31]. The case figures are based on reportable disorders that each laboratory is obligated to report to their local or state public health officials, as well as active surveillance undertaken by the Center for Disease Control and Prevention (CDC). Pathogenic *E. coli*, *Campylobacter spp*. and *Salmonella* were the leading causes. Species., although the causes of approximately 80% of illnesses were unknown. Approximately 25% of the 15.9 million gastroenteritis episodes that occur in Australia are thought to be spread by contaminated food. This translates to an average of one foodborne gastroenteritis episode per five years per person [31].

#### **6.1 Pathogens that cause foodborne disease**

There were almost 250 distinct food-borne illnesses identified. The majority of these illnesses are infections caused by bacteria, fungus and parasites that can be spread by food. Poisonings, for example, are diseases caused by hazardous poisons or compounds contaminating food, such as toxic mushrooms or fungus. These different diseases have many different symptoms, so there is no one 'syndrome 'that is a foodborne illness. However, the microbe or toxin enters the body through the gastrointestinal tract, and often causes the first symptoms there, so nausea, vomiting, abdominal cramps and diarrhoea are common symptoms in many foodborne diseases, and if the symptoms are not controlled lead to be fatal [29].

#### *6.1.1 Listeria monocytogenes*

*L. monocytogenes* is a bacterium that causes food contamination which is responsible for listeriosis. It usually produces just a mild sickness in healthy people. *L. monocytogenes* can be found all over habitats. It had been isolated from domestic and wild animals, birds, soil, plants, feed, water and food processing factory floors, drains and damp places. This bacterium is a Gram-positive rod-shaped bacterium that do not generate spores. A lot of factors influence the growth and survival of *L. monocytogenes* [32, 37].

#### *6.1.2 Bacillus subtilis*

*B. subtilis* cells are rod-shaped, Gram-positive bacteria that are naturally found in soil and plants. *B. subtilis* grow in the mesophilic temperature range. The optimal temperature for growth ranging is 25–35°C. The creation of stress-resistant endospores is one such technique. Another strategy is the uptake of external DNA, which allows the bacteria to adapt by recombination. These solutions, however, take time to implement it can sometimes contaminate food, however, they seldom result in food poisoning, but it main responsible for many types of food spoilage. Several such species have been described which are mostly the variants of *B. subtilis*, they are probably present in most bread. *B. subtilis* had been reported spoiling canned seafoods, meats etc. [32].

#### *6.1.3 Micrococcus luteus*

*M. luteus* is a Gram-positive, coccoid bacterium [0.5 to 3.5 microns in diameter]. It is capable of dividing into more than one plane. *M. luteus* can be found on human skin as well as in soil, dust, water, and air. It is a typical part of the human body's flora. The bacterium colonises the human mouth, mucosae, oropharynx and upper respiratory tract. It is not usually considered a pathogen, or disease-causing organism of healthy people [33].

#### *6.1.4 Shiga toxin-producing Escherichia coli [STEC]*

*E. coli* are bacteria that form part of the normal gut flora of humans and other warm-blooded animals. Although most E. coli are considered harmless, certain strains can cause severe illness in humans, particularly Shiga toxin-producing *E. coli* [STEC], which is also known as verocytotoxin-producing *E. coli* [VTEC]. Infection with STEC is the main cause of haemolytic uraemic syndrome, a condition that can be fatal in humans. *E. coli* are Gram-negative, rod-shaped bacteria and are members of the family Enterobacteriaceae [34].

#### *6.1.5 Aspergillus flavus*

*Aspergillus* is a common mould found on bread and other types of food such as meat and fish, as the mould grows on food it produces enzymes that break down the food resulting in spoilage. In addition to enzymes, *Aspergillus flavus* also produce mycotoxins onto the food. Ingestion of mycotoxin-contaminated food is fatal. Hundreds of people in developing countries die every year after consuming grains contaminated with mycotoxins [35].

#### *6.1.6 Rhizopus stolonifera*

*Rhizopus sp.* is a genus of common saprophytic fungi on plants and specialised parasites on animals. The bread mould, *Ranunculus stolonifer*, may grow on a broad variety of foods and plants, causing food spoilage and plant diseases in the field. It thrives in somewhat acidic environments, thus it like both fruit and bread. Offflavors, mycotoxins contamination, discoloration, and rotting are all symptoms of food spoilage caused by mould. Spoilage can occur either in the field or in storage. The water activity of the food determines the types of mould spoiling the food [36].

#### **7. Value of essential oils in food preservation**

In recent years, there has been successful research into the use of essential oils in the preservation of food commodities in order to extend shelf life. Various investigators had used essential oils, either in pure or formulation forms, to enhance the shelf-life

*Essential Oils as Antimicrobial and Food Preservatives DOI: http://dx.doi.org/10.5772/intechopen.103000*

of food commodities in different storage containers such as those made of cardboard, tin, glass, polyethylene, or natural fabrics and have observed significant enhancement of shelf-life [4]. An earlier study reported that some essential oil constituents such as citral, citronella, citronellol, eugenol, farnesol and nerol could protect chilli seeds and fruits from fungal infection for up to 6 months [24]. Essential oil from *A. conyzoides* successfully controlled the rotting of mandarins by blue mould and increased mandarin shelf-life by up to 30 days [37]. Essential oils from *C. nardus, C. flexuosus* and *O. basilicum* and observed that they could significantly control anthracnose in banana and increased banana shelf-life by up to 21 days. For up to 3 weeks, *C. flexuosus* essential oil [20 L/mL] can prevent *Malus pumilo* fruits from decaying [26, 38]. A fumigant application of essential oils from *Putranjiva roxburghii* was effective against *A. flavus* and *A. niger* infecting groundnuts during storage and enhanced the shelf-life of groundnut from fungal biodeterioration for up to 6 months [24]. The use of *Cymbopogon pendulous* essential oil as a fumigant increased groundnut shelf-life by 6–12 months, thus proving to be more effective than *P. roxburghii*. Food preservation involves preventing the growth of foodborne microorganisms that lead to food spoilage or food contamination just like bacteria, fungi [39]. Unpreserved food can lead to its spoilage by microorganisms which make denaturation to the food and make it unfit to be consumed so the economy of the countries will be affected, or the food can be contaminated by dangerous pathogenic foodborne microorganisms [25, 40].

#### **8. Conclusion**

Researchers from all over the world had been drawn to the study of plant antimicrobials as a result of their work on essential oils. Essential oils and their compounds have clearly been extensively characterised, and essential oils had been employed to combat a wide range of diseases. As a result, this chapter included a brief summary of essential oils and how they can be used as antibacterial, antifungal, and food preservatives. Essential oils have a wide spectrum of antibacterial characteristics, according to the relevant literature review and their natural sustainability when they are utilised as possible biocontrol agents against pathogenic bacteria and fungi. In this regard, we suggest that essential oils are safe and cheap as biocontrol products that should be investigated further because of their ability to preserve food.

### **Author details**

Mamdouh S. Serag\*, Reham A. Elfayoumy and Marwa T. Mohesien Faculty of Science, Department of Botany and Microbiology, Damietta University, Egypt

\*Address all correspondence to: mamdouhserag054@gmail.com; mserag@du.edu.eg

© 2022 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.

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#### **Chapter 5**

## Encapsulation of Essential Oils and Their Use in Food Applications

*Hamdy A. Shaaban and Amr Farouk*

#### **Abstract**

Due to the modern lifestyle and consumers' interests, demands toward healthy foods and nutraceuticals were increased, among them essential oils (EOs) characterized by different biological activities. However, the use of EOs in foods and pharmaceuticals may be limited due to the hydrophobicity nature in addition to the instability and cause of degradation upon exposure to environmental conditions, e.g., oxygen, temperature, and light. Therefore, encapsulation in various colloidal systems such as microcapsules, nanospheres, nanoemulsions, liposomes, and molecular inclusion complexes, seem to be the solution for such issues. New trends in food packaging have also been focused on exploiting capsulated bioactive EOs constituents for extending foods' shelf life due to their potent antimicrobial agents and the great activity against pathological bacteria. Micro and nanoencapsulation of EOs may affect their biological activities based on the technique used. In the current chapter, different subjects have been discussed, like techniques used for the encapsulation of EOs, potential applications in food, and their behaviors/trends after encapsulation.

Moreover, the benefits of encapsulation, namely bioavailability, controlled release, and protection of EOs against environmental stresses, are discussed. The applications of encapsulated EOs are also summarized in this chapter. Also, the relevance of the encapsulation of EOs as antimicrobial agents and their incorporation into food packaging are discussed.

**Keywords:** essential oils, encapsulation, biological activities, food preservation

#### **1. Introduction**

Essential oils (EOs) can be extracted from any part of plants and are considered secondary metabolites. They usually comprise a complex mixture of alkaloids, flavonoids, isoflavones, monoterpenes, phenolic acids, carotenoids, and aldehydes [1]. EOs consist of a broad spectrum of components in which the efficacy as antimicrobial, antioxidants, etc., comes from the synergistic effect of many components. These components are responsible for the ability of EOs to be introduced and incorporated in many applications, such as in cosmetics, nutraceuticals, and food products. The application of EOs industrially is often limited. They are susceptible to environmental conditions such as light, oxygen, and temperature; they easily evaporate, are nearly

insoluble in water, and have strong lipophilicity and volatility [2]. As a result, exploring the potential to extend their applications has become a key research issue.

Encapsulation has been introduced to improve EOs applications. It allows for the preservation of bio-functional properties of EOs, enhancing their stability against harsh conditions, giving benevolent masking effect, and providing controlled release of EOs. In a study by Shetta et al. [3], it was found that encapsulation significantly enhances the thermal stability of encapsulated peppermint and green tea EOs around 2.18 and 1.74 folds, respectively, pure EOs. Encapsulation can be achieved by many techniques and divided into 1) chemical method, 2) physicomechanical method, and 3) physicochemical method. The encapsulation process might involve more than one technique [4]. The selection of the most feasible technique would depend on the type of coated material, the operational cost, and the application of the encapsulation products. Encapsulation parameters such as encapsulation efficiency, encapsulation yield, payload/loading capacity, and surface loading are commonly used as primary indicators to reflect the performance of the encapsulation process and quality of encapsulation products (encapsulates).

Packaging protects foods from environmental factors and microbial contamination to maintain food quality and safety [5]. Using bioactive packaging avoids food spoilage and poisoning, which seriously affects public health and extends the shelf life of food products, especially those susceptible to microbial spoilage [6]. Unlike routine packaging, which only avoids the exchanges of air gases, moisture, and aromatic compounds between the food and the environment around [7], bioactive packaging provides antimicrobial activity to extend shelf life and food safety [8].

The safety and quality of packaged food by incorporating natural antimicrobial compounds and natural antioxidant compounds [9] is now an active research area [10–14]. Unfortunately, their use in raw form in food packaging materials is restricted by the hydrophobicity nature and the low stability against the environmental conditions during the processing, distribution, and storage of foods [15]. Also, the uncontrolled release of volatile active constituents of EOs can significantly negatively affect their biological benefits [15]. To overcome such limitations, appropriate carriers and encapsulation techniques were designed.

The design of the encapsulation method on the form of essential-oil-loaded particles is a complex process with interrelated steps [5] based on many factors like choosing the wall material, technique used, and the intended matrix in which essential oils are to be incorporated [8]. Basically, the nanoencapsulation process is the coating or trapping EOs as a core material by biopolymers to avoid the limitations of using EOs as a natural food preservative. Accordingly, different techniques could be used for the nanoencapsulation of EOs, such as nanoemulsion and liposomes. In the specific case of essential oil nanoemulsion, the preparation consists of a biphasic liquid system of one liquid solution dispersed in a continuous medium, and no polymer shells are used [12]. The presence of EOs in stable nanoemulsions helps enhance their dispersibility in aqueous solutions, avoid the interaction with other food ingredients or environment, keep their organoleptic properties, and improve their absorption and bioavailability. Therefore, nanoemulsions ofEos as a natural powerful food conservator became a potential target with respect to the encapsulation technique, leading to the instability or the inefficiency of the produced emulsion. A better understanding of the EOs encapsulation phenomenon would widen the knowledge of possible alternatives to consider while designing green food preservatives for future research. Accordingly, this chapter covers a general description of the EOs and encapsulation

techniques along with evaluation for these methods and a comparison between nanoand microencapsulation. Finally, the effect of the nanoemulsion technique used on the EOs constituents was discussed based on recently published studies [16].

#### **2. Essential oils**

EOs are natural substances consisting of mixtures of different volatile and aromatic constituents. They are widely found in herbs and spices such as garlic, black cumin, cloves, cinnamon, thyme, basil, bay leaves, coriander, mustard, rosemary, sage, and others [17, 18]. The EOs constituents produced as secondary metabolites have many functions, such as insecticidal, antimicrobial agents, or attracting insects to help in flower pollination [18]. Flowers, leaves, stems, roots, fruits, and even seeds could be sources for EOs. Different techniques are used to extract, such as steam and hydrodistillation. Organic solvents extraction such as ethanol, acetone, and methanol are also used based on the polar solubility of the different constituents of EOs [19–21]. Distillation of EOs depends on their density, which is mostly less than 1, despite a few exceptions, e.g., cinnamon, sassafras, clove, and vetiver [22]. Based on the structure of their different constituents, the bioactivity of EOs showed various potential uses and applications as antimicrobial, antioxidant, and antifungal agents against yeasts and filamentous fungi, which represented a potential natural and potential healthy use as food preservatives [23–25]. Due to their antioxidant activity, the application of different EOs in food industries, especially fats and oils, to avoid lipid peroxidation caused by free radicals represented a potential target [26]. Lipid peroxidation results in many negative impacts for food products, including unpleasant aroma and flavors, deterioration of the food quality, decreasing the nutritional value of food, and severe health issues [27]. Based on the modern lifestyle and consumer demands, using EOs as natural antioxidants is favored over synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tert-butylhydroquinone whose applicability has been discouraged due to safety, health, and environmental concerns [28].

Among others, phenols, esters, terpenes, sesquiterpenes, aldehydes, ethers, alcohols, and phenylpropanoids, constitute the main classes in EOs responsible for bioactivity and sensory properties [22, 25]. For example, thymol, carvacrol, α-terpinene, eugenol have antioxidant effects [29], while other constituents such as limonene, eugenol, pinene, carvone, and linalool carvacrol have been suggested as agents responsible for the antimicrobial efficiency against foodborne pathogens [30]. In the same context, eugenol exhibited an efficient bactericidal activity against *Salmonella enterica* serovar *Typhimurium* as well as carveol, citronellol, and geraniol which presented anti bactericidal activity against E. coli, while terpineol had good activity versus S. aureus strains [31]. The presence of hydroxyl groups is responsible for the previously described compounds' higher antimicrobial activity [31]. Meanwhile, other compounds belonging to different classes such as benzoic acids, benzaldehydes, and cinnamic acid have shown up to 50% inhibition of *Listeria monocytogenes* under anaerobic conditions [32]. The EOs of similar plants have been reported to have differences in composition depending on the geographical location that the plant is found [33]. Notably, the composition and yield of EOs can vary with environmental conditions, climate, harvesting stages, planting, preparation methods, and genetics [34]. For example, weather parameters like rains and temperature have influenced the oil content and its constituents [35].

#### **3. Encapsulation**

Encapsulation of active ingredients or a core in solid walls or carriers represents a potential solution to control their release during storage or application and protect them from environmental conditions or interactions with the matrix around. As EOs are hydrophobic, emulsifying or dispersing in an aqueous solution represents the important primary step in the whole process. Following the emulsifying process, encapsulation can be performed by different techniques; chemical techniques like molecular inclusion or interfacial polymerization; physicochemical techniques like conservation and liposome encapsulation; and physical techniques like spray drying, spray chilling/cooling, co crystallization, extrusion, or fluidized bed coating [36]. Based on the technique and energy used, capsules can be found in micro and nanoscales, where microcapsules range between a few micrometers and a few millimeters while nanocapsules are found in the range of 53.8–415.2 nM. Other factors affect the size and physical properties of the capsules, like the natural or synthetic polymers used as wall materials and the core used. This system can increase the passive cellular absorption mechanisms, reduce mass transfer resistances, and increase antimicrobial activity due to its subcellular size [37].

#### **4. Encapsulation of EOs**

Natural EOs and extracts have limited applicability [38] because of drawback reactions during processing, transporting, or storage like oxidation, hydrolysis, crystallization, or enzymatic deterioration in the presence of oxygen and light [39, 40]. The lower thermal stability during food processing causes loss of EOs active components' biological functionalities [41] and significantly deteriorate their flavor and solubility. For example, the pomegranate peel extract associated with easy oxidation causes color deterioration and other instability issues [42], while Satureja hortensis EO drastically changes composition upon heating over 160°C [43]. The intense flavor of EOs, which is used as preservatives, may be transferred to the packed foods and negatively affect the final product's sensory properties [44, 45], so encapsulation is required to avoid the volatility of EOs bioactive components [46]. Consequently, many researchers have encapsulated them into other protection materials in order to make full use of their antioxidant and antimicrobial properties [47]. Nanoencapsulation of bioactive components to apply in food packaging materials are a potential target, growing steadily [48], since it can protect the components and therefore their biological efficiency against oxidative degradation upon exposure to air or high temperatures and during food processing [49, 50], in addition, to control their releasing [51]. For example, encapsulating thyme EO into cyclodextrin/ε-polylysine can reduce undesirable deficiencies such as volatility and hydrophobicity of its bioactive components [52]. While carvacrol, characterized by its antimicrobial activity, can be protected/ encapsulated in a starch fiber matrix to avoid direct contact with food and reduce the effects on sensory features [53]. Encapsulation in zein microparticles improved the thermal stability of polyphenols from maqui fruit extract when exposed to high temperatures related to processed foods [54]. Orange and thyme oil adsorbed in halloysite or montmorillonite clay and then encapsulated in a polyethylene/polyamide/polyethylene multilayer film prolongated aroma release [55]. Encapsulation of black pepper (*Piper nigrum* L.) EO into sodium alginate and gelatin by complex coacervation avoids the loss of the main volatile from EOs preserved (80% of their original content) [56].


#### *Encapsulation of Essential Oils and Their Use in Food Applications DOI: http://dx.doi.org/10.5772/intechopen.103147*

#### **Table 1.**

*Summary of recent studies on micro- and nanoencapsulation of food bioactive compounds.*

#### **5. Encapsulation process evaluation method**

Generally in encapsulation, the idea of quantifying EO upon encapsulation process is 1) to calculate encapsulation efficiency and other encapsulation parameters; 2) to perform a controlled release study and understand the kinetics of release [57]; as well as 3) to evaluate the stability of encapsulates based on how much oil is left in the encapsulates [58], or how much oil is released to the releasing media [59], and still adhered to the surface [60]. Besides that, it is crucial to determine the components that are successfully encapsulated and responsible for the bio-function of EOs exactly. These components or types of EOs would have effects on encapsulation evaluation parameters. In a study by ref. [61], different encapsulation efficiency values were obtained when encapsulating kaffir lime oil from peels (KLO-P) and twigs oil fraction (KLO-TF) using chitosan as wall material. It was found that the encapsulation efficiency of KLO-TF is greater than KLO-P. The encapsulation efficiency difference was attributed to the components presented in each kaffir lime oil in which KLO-TF contains more oxygenated monoterpene components while the hydrocarbon monoterpenes components dominate KLO-P. Oxygenated monoterpenes components are more likely to interact with the functional group (active site) in the encapsulate, and as a result, more KLO-TF was successfully encapsulated.

Determination of EO in encapsulates can be done gravimetrically through direct measuring [62] or the distillation process. However, drawbacks associated with such techniques are that a large amount of formulation is required, improper extraction, and chances of loss of EO due to volatilization. To overcome these issues, reliable techniques using analytical methods such as chromatographic or spectrophotometric methods are introduced and expected to exhibit higher values than when the thermogravimetric analysis is used [63]. When employing these analytical methods, sometimes, digestion of the wall material is required to be achieved physically, chemically, or enzymatically [64]. **Table 1** below shows different types of EOs and commonly used solvents and methods to digest encapsulated walls. Subsequently, EO is extracted using an organic solvent such as hexane [65], petroleum ether, ethanol [66], or non-ionic surfactant; tween-80 before quantification using appropriate analytical methods. These analytical methods also have some disadvantages, such as possible experimental error, chances of loss of EO due to volatilization, and the possibility that the method selected is not convenient. For example, in cases where digestion of encapsulated walls is needed, the digested wall materials might somehow interfere with the spectrometric reading of EO. However, this could be resolved by using appropriate solvent and technique. Tolun et al. [66] used hexane to extract Moxa oil from encapsulates since gelatine and Gum Arabic used as encapsulating material did not interfere with the measurement process as they were insoluble in hexane. Meanwhile, Fraj et al. [67] used derivative spectrophotometry for quantitative analysis of core material since wall materials used (vitamin C and genipin) were also soluble in ethanol.

#### **6. Nanoencapsulation versus microencapsulation**

A comparison of micro- and nanoencapsulation functionality has been reported by [68], as shown in **Figure 1**. The main functionalities of microencapsulation taken into consideration are protecting active ingredients, including the extension of shelf

**Figure 1.** *Advantagesofnano-andmicroencapsulation [69].*

life and controlling the release of bioactive components. While for nanocapsules, more attention is given to the functionals related to the size reduced like higher surface area and improving intracellular uptake. According to the authors, the formulation in nanoscales may improve bioavailability; however, this may depend on the technique used, as discussed later in section 7 of this chapter.

Particle size is an important factor affecting the functional characteristics of capsules [70]. Nanoencapsulation is the formulation of capsules with less than 1 micron (1000 nm), possessing different properties than ordinary encapsulation. According to the literature, capsules should be less than 100 nm to be considered nanocapsules [71]. The nanometric size of delivery systems can increase the surface area and, consequently, the food matrices' dispersion to form uniform and stable colloidal suspensions and may have better sustained-release effects than microcapsules. Based on their smaller size, nanocapsules can increase the passive cellular absorption mechanisms, promoting the effective release of active substances inside the target cells and consequently increasing the efficiency of active substances and their bioavailability.

Meanwhile, nanoparticles may penetrate the tissues (such as the liver) through the capillaries and are absorbed by the cells in the tissues; thus, the active substance can be efficiently delivered to the target cells in the body [72]. In the case of emulsionsbased delivery systems, some interesting physical properties can distinguish nano and microemulsions. Microemulsions generally exhibit multiple scattering of visible light, which means they have an opaque white appearance. Conversely, nanoemulsions are much smaller than visible wavelengths, and therefore, they appear almost optically transparent, making them easily applied in the beverage industry [73].

Despite the numerous technologies for encapsulating biologically active compounds studied, only a few techniques, namely spray-drying and freeze-drying, are widely applied in the food industry [74]. Emulsification represents the first step of encapsulation. There are two types of approaches used to produce emulsions: a top-down approach and a bottom-up approach. The top-down approach involves

reducing coarse particles' size through intensive mechanical destructive forces like high-pressure and high-shear homogenization, microfluidization, and microchannel homogenizers [75]. On the other hand, the bottom-up approach generally includes self-assembly, phase inversion, and spontaneous emulsification, which are affected by pH, temperature, concentration, and ionic strength [69].

Low-energy methods are used to prepare emulsions before other nanoencapsulation methods, e.g., spray-drying, complex coacervation, extrusion, electro-spinning, and electro-spraying [76]. However, low-energy methods require more stabilizers and surfactants to reduce the size and easily disperse the active ingredients [69]. Choosing the primary encapsulation technique is interrelated with many factors like the core and wall material properties, solubility, emulsification, particle size distribution, and food matrix composition [76]. **Table 1** summarizes the commonly used encapsulation techniques to formulate nano- and microcapsules.

#### **7. Effect of Encapsulation by the Intensive-energy techniques on the structure and bioactivity of EOs components**

Literature dealing with the encapsulation of EOs focused on the physical stability and biological activity of the micro or nanoparticles but not on the changes in the volatile constituents of the capsules. Few studies have reported that the formulation based on energy-intensive techniques like high-pressure and high-shear homogenization may lead to Ostwald ripening, flocculation, or coalescence of the emulsion with changes in its physical stability and biological activity [77]. Ali et al. [78] studied the effect of nanoencapsulation on volatile components and the bioactivity of Algerian *Origanum glandulosum* Desf. essential oil, a significant quantitative difference was observed in the level of monoterpenes between hydrodistilled oil and its nanocapsules. Additionally, the majority of sesquiterpenes were not detected in the nanocapsules extract. They owed that to the intensive-energy homogenization at 18000 rpm. Also, they reported that essential oil exhibited a higher antioxidant activity than nanocapsules and nanoemulsions, while nanocapsules showed the most potent cytotoxic effect on liver cancer cell line Hep-G2 in comparison to HD oil and nanoemulsions. In the same context, thymol and carvacrol were detected as predominates in the nanoemulsion of Algerian

*Saccocalyx satureioides* Coss. et Durieu oil was prepared by high-pressure homogenization, while borneol and α-terpineol were the major compounds detected in the same hydrodistilled oil, which affected the bioactivity of the oil and nanoemulsion [79]. Also, *Citrus sinensis* L.peel essential oil exhibited antifungal activity against *A. niger*, *A. ochraceus*, *Fusarium* spp., and *Penicillium* spp. Its nanoemulsion displayed lower antifungal activity, based on the changes in the chemical constituents due to homogenization by high-intensity ultrasound [80]. Further studies are necessary in order to explain the behavior of bioactive components during different encapsulation processes, especially the intensive-energy ones, and thereby evaluate the compatibility of the different encapsulation techniques for EOs.

#### **8. Conclusions**

Encapsulation represented an efficient approach to protect the EOs against environmental conditions that lead to oxidation or volatilization and reduced biological *Encapsulation of Essential Oils and Their Use in Food Applications DOI: http://dx.doi.org/10.5772/intechopen.103147*

activities. Moreover, encapsulation solves the problem of EOs hydrophobicity and controls their release. Spray drying and emulsification are the most versatile and commercially available techniques used widely for EOs encapsulation. The encapsulated EOs showed enhanced antimicrobial, antifungal, antioxidant, antiviral, and insecticidal activities. The use of encapsulated EOs in food, cosmetics, and pharmaceutics could be an economic benefit and fulfill consumer concerns regarding safety. Energy-intensive techniques may negatively affect the structure-activity relationship of EOs bioactive components; therefore, further studies are necessary to find out the compatibility of encapsulation techniques for EOs.

#### **Funding sources**

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

#### **Conflict of interest**

The authors declare that there is no conflict of interest.

#### **Author details**

Hamdy A. Shaaban\* and Amr Farouk Department of Chemistry of Flavour and Aroma, National Research Center, Dokki, Giza, Egypt

\*Address all correspondence to: hamdy.shaaban64@gmail.com

© 2022 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.

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### Section 3
