**3. Composition of goat milk**

The intake of some active compounds present in food, the so-called nutraceuticals and functional foods, can be regarded as having beneficial effects (physical and mental) on certain

As technology and science advances, the fields of health and nutrition have focused on several emerging fields, namely nutrigenomics, or "personalized nutrition." The study of the human genome in order to comprehend cellular response to nutrients and bioactive compounds is a promising field of work, which should lead specific dietary recommendations to prevent or aid in the treatment of certain diseases. In fact, stroke, cancer, and atherosclerosis and the general risk of diseases may be somehow minimized by introducing proper preventive nutrition and functional foods/foods as part of a healthier lifestyle that includes a balanced diet and physical activity [1]. Ingesting a wide variety of foods, namely fruits, vegetables, whole grains, milk, meat, and eggs is one way to ensure the intake of certain bioactive compounds that are present in its constitution such as carotenoids, dietary fiber, fatty acids, flavonoids, isothiocyanates, minerals, phenolic acids, plant stanols/sterols, polyols, prebiotics and probi-

Functional foods are growing in reputation across the globe and are becoming a part of daily diet of consumers who are concerned with their health. The global market potential for functional foods and beverages has been estimated to be worth \$192 billion by 2020 [3]. However, the effectiveness of nutraceutical products in preventing diseases depends on preserving the stability, bioactivity, and bioavailability of the active ingredients [4]. Functional foods are found virtually in all food categories; however, some products are not widely available

Sheep and goat products (mainly meat and dairy) have interesting characteristics in their levels of flavor, taste, aromas, and leanness as well as the specific composition of fats, proteins, amino, and fatty acids and have been traditionally consumed in certain regions of the globe [6]. Additionally, the nutritional properties of goat milk and its lower allergenicity when compared to cow milk [7, 8] has sparked an interest in goat milk as a functional food, and it is now one of the current trends in healthy eating in developed countries [9]. Moreover, the use of milk with particular nutritional properties, alone or in combination with bacterial strains with probiotic properties and capable of producing physiologically active metabolites, might

The present chapter intends to give a comprehensive approach of the unique characteristics of goat-derived products, which have attracted the interest of researchers worldwide. This chapter aims to explore the nutritional value and bioactivity of the constituents of these products, with an emphasis in the reduction of the risk of chronic disorders by anti-inflammatory and anti-oxidative effects. The ability of goat's milk and its derivatives to selectively encourage bacterial growth in intestinal microbiota and the beneficial effects in the metabolic, endo-

become one of the options for manufacturing new dairy functional beverages [10].

crine, and immune systems will also be a subject of this chapter.

functions in the human body, that go beyond their nutritional effects.

otics, phytoestrogens, soy protein, sulphides/thiols, and vitamins [2].

in the market [5].

190 Goat Science

**2. Materials and methods**

Milk and derived dairy products are considered an important constituent of a balanced diet. Milk, as the first food for mammals, supplies all the energy and nutrients needed forthe proper growth and development of the neonate. For all mammalians, the consumption of milk ends at the weaning period except in humans, which continue consuming milk throughout their life.

The physical characteristics and composition of milk vary between species. Chemically, milk is a complex oil-in-water emulsion containing proteins, fats, carbohydrates (mainly lactose), and lower amounts of minerals, enzymes, cells, hormones, immunoglobulins, and vitamins.

The information currently available on the composition of goat milk has been published in the form of reviews [11–13]. Authors are unanimous in recognizing that fresh milk composition has a dynamic nature that varies with several factors such as (a) genetics (e.g., species, breed, and individual); (b) stage of lactation; (c) health status of the individual animal; and (d) environmental factors (e.g., feed, climate, season, or method of milking) [14–16].

Approximate compositions of the milks of different animals are compared in **Table 1**.

The basic nutrient composition of goat milk resembles that of cow milk (**Table 1**). Both milks contain substantially higher amounts of proteins and minerals, but lower lactose content than human milk [17]. Nonetheless, goat milk has high concentrations of fat globules, which are smaller than those present in cow milk; these globule diameters average are approximately 3.6 and 3.0 μm against 4.0 μm, respectively [18, 19]. The smaller size of fat globules provides a smoother texture in goat's derived products. Furthermore, goat milk contains lower amounts of α1-casein conferring it a higher water-holding capacity and a lower viscosity [20, 21]. Despite all these properties, the flavor of goat's milk is peculiar and more intense in comparison to cow's milk, which can restrict the acceptance of its derivatives by consumers [21]. However, goat milk is more easily digested than cow milk due to the absence of agglutinins in the former [11].

Goat and cow milk differ essentially in their casein micelles (structure, composition, and size), the proportion of individual protein fractions and higher content of nonprotein nitrogen and mineral compounds found in goat milk.


**Table 1.** Basic composition of different milks (mean values per 100g) (adapted from Yadav et al. [24]).

#### **3.1. Proteins**

The variability in milk composition, among individual animals of the same breed, is attributed to an extensive and complex genetic polymorphism of the goat milk caseins. The protein portion has a fundamental role on the nutritional and technological value of milk. Milk proteins are made of heterogeneous groups in terms of composition and properties and are divided into casein—the main group of proteins—and whey protein fractions to a lesser extent.

The total protein content in goat milk varies from 2.6 to 4.1 g/l. Casein is composed of four fractions: αS1-casein, αS2-casein, β-casein, and κ-casein [22]. The proportions of the milk casein fractions differ between ruminant species and the micelle characteristics also differ in regard to size, hydration, and mineralization. As reported by Grosclaude and Martin [23], in studies conducted using French Alpine and Saanen goats, milk from animals with low alleles FF had total casein and total protein contents of 22 and 27 g/l, respectively. These values increase to 27 and 32 g/l in milk from animals possessing strong alleles AA. Generally, goat milk contains less αS1-casein than other ruminants' milk. However, as allele frequency forthis specific casein varies between breeds, its concentration in goat milk depends indirectly on the breed [23].

Other characteristics of goat milk proteins are their structural conformations and the amounts and subtypes of micelles, which are smaller (180 nm) than those of cow milk (260 nm) and similar to those of sheep milk (193 nm) [11].

It has been reported that beta casein comprises the largest fraction of total goat milk casein. Although αS2-casein is relatively higher in goat milk, the αS1 fraction of cow milk alone is higher than both the αS1 and αS2-casein fractions present in goat milk. These differences might help explain the soft curd-forming properties of goat milk, as well as its better digestibility and the lower frequency of allergic reactions in children [24].

The nutritional value of proteins present in milk depends on its essential amino acid content. Only small differences exist in milk amino acid levels per 100 g of protein between different species, which are most likely due to differences in total protein content [15, 25]. A comparison of amino acid content between different species can be seen in **Table 2**.

When compared to cow milk, goat milk has higher levels of essential amino acids: threonine, leucine, lysine, cystine, tyrosine, phenylalanine, valine, and nonessential proline and glutamic acid (**Table 2**) [26].

to lipid supplementation increased the fat content of goat milk without decrease in its protein content. Bovine, sheep, goat, and human milk fat consist of 97–98% of triglycerides, but have

**Table 2.** Amino acid composition of goat milk and cow milk (mg/100g milk) (adapted from Ceballos et al. [26]).

**Goat milk Cow milk**

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The main characteristic of goat milk fat is the high content in short- and medium-chain fatty acids (MCFA). Average goat milk fat profile of fatty acids presented levels of butyric (C4:0), caproic (C6:0), caprylic (C8:0), capric (C10:0), lauric (C12:0), myristic (C14:0), palmitic (C16:0), and linoleic acids (C18:2) higher than those exhibited by cow milk. In contrast, goat's milk fat presented lower concentrations of stearic (C18:0) and oleic acid (C18:1) when compared to cow's milk fat. Average fatty acid composition (g/100g milk) of goat and cow milks are presented in **Table 3** [12]. Considering that these fatty acids have a different metabolism from that of long-chain fatty acids they present different functional proprieties [30]. Recent works of Núñez-Sánchez et al. [31] demonstrated that goat's milk exceeds cow's milk in its content of monounsaturated and polyunsaturated fatty acids and medium chain triglycer-

only low levels of phospholipids (0.5–1.5%) and free fatty acids (0.7–1.5%) [11].

Thr 138.67 115.81 Ileu 160.54 128.04 Leu 341.01 266.23 Lys 342.86 252.59 Met 77.95 71.15 Cys 30.62 23.20 Phe 175.45 133.51 Tyr 162.51 159.99 Val 210.23 147.34 **Total 1639**.**84 1298**.**36**

Arg 135.65 114.44 Hist 122.73 93.06 Asp 117.95 96.0.859 Ala 250.15 214.22 Glu 694.58 554.30 Gly 55.83 49.24 Pro 310.61 253.38 Ser 152.65 147 **Total 1840**.**15 1522**.**58**

ides. We will return to this subject later in this chapter.

Essential amino acids

Nonessential amino acids

The importance of amino acid composition and polypeptides will be examined later in this chapter.

#### **3.2. Fat**

Fat content is the more quantitatively and qualitatively variable component of milk, depending on season, lactation stage, breed, genotype, and feeding. This last factor has been extensively studied, and Sanz Sampelayo et al. [27] examined the influence of feeding, roughage, and lipid supplementation on the fat content of both ewe and goat milk, and the presence of fatty acids of nutritional interest, such as rumenic acid or omega-3, as well as other fatty acids with potentially detrimental effects, such as trans fats. Chilliard et al. [28, 29] showed that goat's response


**3.1. Proteins**

192 Goat Science

ilar to those of sheep milk (193 nm) [11].

tamic acid (**Table 2**) [26].

chapter.

**3.2. Fat**

The variability in milk composition, among individual animals of the same breed, is attributed to an extensive and complex genetic polymorphism of the goat milk caseins. The protein portion has a fundamental role on the nutritional and technological value of milk. Milk proteins are made of heterogeneous groups in terms of composition and properties and are divided into casein—the main group of proteins—and whey protein fractions to a lesser extent.

The total protein content in goat milk varies from 2.6 to 4.1 g/l. Casein is composed of four fractions: αS1-casein, αS2-casein, β-casein, and κ-casein [22]. The proportions of the milk casein fractions differ between ruminant species and the micelle characteristics also differ in regard to size, hydration, and mineralization. As reported by Grosclaude and Martin [23], in studies conducted using French Alpine and Saanen goats, milk from animals with low alleles FF had total casein and total protein contents of 22 and 27 g/l, respectively. These values increase to 27 and 32 g/l in milk from animals possessing strong alleles AA. Generally, goat milk contains less αS1-casein than other ruminants' milk. However, as allele frequency forthis specific casein varies between breeds, its concentration in goat milk depends indirectly on the breed [23].

Other characteristics of goat milk proteins are their structural conformations and the amounts and subtypes of micelles, which are smaller (180 nm) than those of cow milk (260 nm) and sim-

It has been reported that beta casein comprises the largest fraction of total goat milk casein. Although αS2-casein is relatively higher in goat milk, the αS1 fraction of cow milk alone is higher than both the αS1 and αS2-casein fractions present in goat milk. These differences might help explain the soft curd-forming properties of goat milk, as well as its better digest-

The nutritional value of proteins present in milk depends on its essential amino acid content. Only small differences exist in milk amino acid levels per 100 g of protein between different species, which are most likely due to differences in total protein content [15, 25]. A compari-

When compared to cow milk, goat milk has higher levels of essential amino acids: threonine, leucine, lysine, cystine, tyrosine, phenylalanine, valine, and nonessential proline and glu-

The importance of amino acid composition and polypeptides will be examined later in this

Fat content is the more quantitatively and qualitatively variable component of milk, depending on season, lactation stage, breed, genotype, and feeding. This last factor has been extensively studied, and Sanz Sampelayo et al. [27] examined the influence of feeding, roughage, and lipid supplementation on the fat content of both ewe and goat milk, and the presence of fatty acids of nutritional interest, such as rumenic acid or omega-3, as well as other fatty acids with potentially detrimental effects, such as trans fats. Chilliard et al. [28, 29] showed that goat's response

ibility and the lower frequency of allergic reactions in children [24].

son of amino acid content between different species can be seen in **Table 2**.

**Table 2.** Amino acid composition of goat milk and cow milk (mg/100g milk) (adapted from Ceballos et al. [26]).

to lipid supplementation increased the fat content of goat milk without decrease in its protein content. Bovine, sheep, goat, and human milk fat consist of 97–98% of triglycerides, but have only low levels of phospholipids (0.5–1.5%) and free fatty acids (0.7–1.5%) [11].

The main characteristic of goat milk fat is the high content in short- and medium-chain fatty acids (MCFA). Average goat milk fat profile of fatty acids presented levels of butyric (C4:0), caproic (C6:0), caprylic (C8:0), capric (C10:0), lauric (C12:0), myristic (C14:0), palmitic (C16:0), and linoleic acids (C18:2) higher than those exhibited by cow milk. In contrast, goat's milk fat presented lower concentrations of stearic (C18:0) and oleic acid (C18:1) when compared to cow's milk fat. Average fatty acid composition (g/100g milk) of goat and cow milks are presented in **Table 3** [12]. Considering that these fatty acids have a different metabolism from that of long-chain fatty acids they present different functional proprieties [30]. Recent works of Núñez-Sánchez et al. [31] demonstrated that goat's milk exceeds cow's milk in its content of monounsaturated and polyunsaturated fatty acids and medium chain triglycerides. We will return to this subject later in this chapter.

#### 194 Goat Science


**3.3. Carbohydrates**

**3.4. Minerals**

Lactose is the main carbohydrate in milk: about 44% in goat milk and 49% in sheep milk. Its concentration does not vary excessively [32, 33]. However, goat milk lactose content is often

Raynal-Ljutovac et al. [13] presented an update of the composition of goat and sheep milk products. In this document, authors complicated data available concerning the main mineral composition of goat and sheep milks (**Table 4**). Goat milk is distinguished by its high chloride and potassium content. A more recent study by Trancoso et al. [35], focusing on goat milk fromthemain Portuguese indigenous breeds (Serrana, Serpentina, Charnequeira, andAlgarvia), also obtained similar results regarding mineral composition in the milk produced by these animals. Raynal-Ljutovac et al. [13] indicated that caprine milk provided a great amount

**Goat (per L) Sheep (per kg)**

largely increased by dietary plant oil supplementation in contrast to cow milk [34].

**Table 3.** Fatty acid composition (mg/100g milk) of goat and cow milk fat (adapted from Ceballos et al. [26]).

**Lipid profile Goat milk Cow milk** MUFA 1342.67 874.27 PUFA 213.25 109.32 PUFA n-6 146.97 86.41 PUFA n-3 26.81 8.55 PUFA n-6/n-3 5.49 10.49 SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids.

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of magnesium, calcium, and phosphorus with a normal Ca/P ratio in milk as 1.20.

Calcium (mg) 1260 1950–2000 Phosphorus (mg) 970 1240–1580 Potassium (mg) 1900 1360–1400 Sodium (mg) 380 440–580 Chloride (mg) 1600 1100–1120 Magnesium (mg) 130 180–210 Ca/P (mg) 1.3 1.4 Zinc (μg) 3400 5200–7470 Iron(μg) 550 720–1222 Copper (μg) 300 400–680 Iodine (μg) 80 53–90 Selenium (μg) 20 31

**Table 4.** Mineral composition of goat and sheep milk (adapted from Balthazar et al. [19]).


**Table 3.** Fatty acid composition (mg/100g milk) of goat and cow milk fat (adapted from Ceballos et al. [26]).

#### **3.3. Carbohydrates**

**Lipid profile Goat milk Cow milk** C4:0 66.55 116.44 C6:0 171.68 77.86 C8:0 192.20 57.80 C10:0 579.10 114.91 C11:0 7.46 7.29 C12:0 232.61 130.87 C14:0 518.56 384.41 C14:1 7.19 16.87 C15:0 28.11 35.23 C15:1 3.01 2.74 C16:0 1340.97 1102.72 C16:1 51.58 52.32 C16:2 n-4 1.57 0.57 C17:0 18.44 6.27 C17:1 4.32 2.85 C18:0 493.56 378.25 C18:1 n-9, trans 19.22 55.75 C18:1n-9, cis 1245.92 742.71 C18:2 n-6 142.39 82.31 CLA n-7, cis-9, trans-11 18.70 13.79 CLA n-6, trans-10, cis-12 3.53 1.82 CLA n-7, cis-9, cis-11 1.05 – CLA n-5, cis-11, trans-13 12.42 – CLA total 35.75 15.62 C18:3 n-3 27.72 8.55 C20:0 2.49 3.76 C20:1 n-9 1.57 1.03 C20:2 n-6 5.49 1.48 C20:3 n-6 - 0.80 C21:0 1.44 0.23 C22:0 4.05 3.99 C23:0 0.26 0.91 C24:0 0.66 0.68 C24:1 n-9 0.92 – C6-14 1695.70 790.02 SFA 3683.10 2436.41

194 Goat Science

Lactose is the main carbohydrate in milk: about 44% in goat milk and 49% in sheep milk. Its concentration does not vary excessively [32, 33]. However, goat milk lactose content is often largely increased by dietary plant oil supplementation in contrast to cow milk [34].

#### **3.4. Minerals**

Raynal-Ljutovac et al. [13] presented an update of the composition of goat and sheep milk products. In this document, authors complicated data available concerning the main mineral composition of goat and sheep milks (**Table 4**). Goat milk is distinguished by its high chloride and potassium content. A more recent study by Trancoso et al. [35], focusing on goat milk fromthemain Portuguese indigenous breeds (Serrana, Serpentina, Charnequeira, andAlgarvia), also obtained similar results regarding mineral composition in the milk produced by these animals. Raynal-Ljutovac et al. [13] indicated that caprine milk provided a great amount of magnesium, calcium, and phosphorus with a normal Ca/P ratio in milk as 1.20.


**Table 4.** Mineral composition of goat and sheep milk (adapted from Balthazar et al. [19]).

As shown in**Table 4**, goat milk is characterized by its lower concentration ofiron, zinc, and copper. López-Aliaga et al. [36] reviewed the mineral bioavailability, apparent digestibility coefficients, and the balance of calcium, phosphorus, magnesium, iron, copper, and zinc after the consumption of a goat milk diet compared with bovine milk diet in resected rats. In their work [36], they concluded that based on the particular biological, nutritional, and metabolic characteristics, goat milk can be an excellent natural food in cases of malabsorption syndrome and present a dietary alternative to bovine milk. Although goat milk has a low iron concentration, it has a higher bioavailability than in cow milk due to the presence of higher amounts of nucleotides that in turn increase absorption in the intestine [13].

Compared to cow milk, goat milk has lower amounts of vitamin E, folic acid, and vitamin B12, which can result in "goat milk anemia" if additional sources for these vitamins are not

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In conclusion, nutritionally, goat milk is comparable to cow milk as it contains similar levels of calcium, potassium, phosphorus, and many other nutrients that confer health benefits (see **Tables 1,2,3** and **5**). However, goat milk contains higher levels of 6 out of the 10 essential amino acids than cow milk [39]. It is also richer in monounsaturated and polyunsaturated fatty acids and medium-chain triglycerides [31], while containing less lactose than cow's milk. The most appealing property of goat milk is its superior digestibility, which can make it par-

The use of goat products was first closely related to a number of medical problems namely food allergies involving cow milk proteins. Cow milk allergy is relatively common during the first 3 years of life. Several studies report that the use of goat milk resolves 30 and 40%

There are a number of unique physiological and anatomical differences between goats and cows which translate into differences in composition of goat milk and its products [40]. Goat milk products are considered dairy products with greatest marketing potential. Therefore, several characteristics of goat milk are currently the focus of increased research interest

Two glasses (0.5 l) of goat milk or the equivalent amount of cheese or yoghurt can provide up to 94% of the recommended adult daily dietary allowance (RDA) of essential amino acids, 83% of calcium, and 78% of riboflavin needs, while also being a dietary source of other miner-

Literature is exiguous concerning the impact of technology (cheese-making) on every nutrient of cheese, other than fat and proteins. Most studies focus on the gross composition (fat, protein, and lactose contents) of Spanish, Italian, and Greek hard or semi-hard cheeses obtained from small ruminants. Gross composition is mostly dependent on the type of cheese and can be classified according to its dry weight. Although both caprine and ovine milk have been widely used in cheese-making, production of fermented caprine milk using probiotics has not yet been developed, despite the existence of studies showing the requirements for its production. Fermentation increases the nutritional value of caprine milk and improves its flavor,

A review by Haenlein [41] focused on several aspects of yoghurt and cheese goat composition. The benefits for human digestion included proteins with different polymorphisms, forming a softer curd on digestion and cheese-making, and the high content in short chain,

making it more tolerable to the average consumer than raw goat milk.

medium chain, and mono and polyunsaturated fatty acids.

ticularly helpful in attenuating irritable bowel type symptoms [36].

**4. Goat-derived products and nutritional value**

als and vitamins, albeit to a lesser extent [40].

present in the diets [13].

of the cases [12].

**4.1. Goat cheese**

[24].

As far as contaminant metals are concerned, concentrations differ between different studies and sampling (feeding, geographic areas, pollution…), and it is therefore difficult to compare species and breeds. According to Trancoso et al. [35], in goat milk from the main Portuguese indigenous breeds, the values for the potentially toxic elements such as Cd, Pb, Co, and Ni are well below the value stipulated by the Commission of the European Communities Directive EC n° 333 [37] for Pb in milk (0.02 mg/kg). Therefore, consumption of caprine milk does not constitute a risk for human exposure to toxic elements at present in Portugal.

#### **3.5. Vitamins**

Goat milk is an adequate source of vitamin A, thiamine, riboflavin, and niacin [11, 36, 38]. However, it presents low levels of folates, as well as vitamin B12, vitamin E, vitamin C, and vitamin D [11, 13] (**Table 5**).


**Table 5.** Vitamin content of goat and cow raw whole milk (per 100g) (adapted from Raynal-Ljutovac et al. [13]).

Compared to cow milk, goat milk has lower amounts of vitamin E, folic acid, and vitamin B12, which can result in "goat milk anemia" if additional sources for these vitamins are not present in the diets [13].

In conclusion, nutritionally, goat milk is comparable to cow milk as it contains similar levels of calcium, potassium, phosphorus, and many other nutrients that confer health benefits (see **Tables 1,2,3** and **5**). However, goat milk contains higher levels of 6 out of the 10 essential amino acids than cow milk [39]. It is also richer in monounsaturated and polyunsaturated fatty acids and medium-chain triglycerides [31], while containing less lactose than cow's milk.

The most appealing property of goat milk is its superior digestibility, which can make it particularly helpful in attenuating irritable bowel type symptoms [36].
