Sheep & Goat Milk: An Upcoming Functional Food
Sheep Milk;Functional Dairy Food
The chief objective of sheep rearing in developing countries is for livelihood security, not commercial benets. In these countries, sheep means only mutton and to some extent wool. In many developing countries, the demand, as well as the visible supply of sheep milk, is negligible. India accounts for 65 million sheep and ranks 3rd in world sheep population, but most sheep here are raised for meat and wool purposes. Thus, contribution to world milk production is insignicant. The concept of milking sheep in developing countries is relatively new but in the new era of functional foods, sheep milk formulations will play pivotal roles in providing human health benets (Mohapatra et al., 2019). Sheep milk produced in the world is about 10.4 Mt (Anonymous, 2018). Its demand has grown worldwide over the years and is expected to increase by approximately 2.7 Mt (+26%) by 2030 (Anonymous, 2018). Because of the increased request for cheese as well as other traditional dairy products, and the most recent use of sheep milk as component of infant formulas, drinking milk and nutraceutical products.
Functional milk is milk that provides health benefits beyond what regular milk provides. It has its origin in functional foods. British Nutrition Foundation defines functional foods as “foods with health-promoting benefits and/or disease – preventing properties over and above their usual nutritional values”. Functional foods are foods or food ingredients that provide a health benefit beyond basic nutrition. These foods have a potentially beneficial effect on an individual’s health when it is consumed as part of a varied diet and on a regular basis at effective levels.” Many scientists working on the functional properties of goat and sheep have concluded that these milks are natural functional milks mainly because of its high nutritional value, digestibility and therapeutic and dietary characteristics. Among these compounds are bioactive peptides and lipids, such as conjugated linoleic acids and other bioactive components like hormones, cytokines, oligosaccharides, nucleotides and minor components, which may have an important role on the development and maintenance of metabolic, immunological and physiological processes and thus contribute to the development of functional dairy products (Haenlein, 2004; Raynal-Ljutovac et al., 2008, Salva et al., 2010, Salva et al., 2011). Milk and colostrum contain a great number of bioactive components influencing the human health such as weight management and hypertension. Furthermore, milk components, such as calcium and proteins and new structures created by reaction of these with other components have a great influence on the technological properties of the milk, and might also influence digestion and health properties. Since Goat and sheep milk is richer in such milk components compared to bovine milk, it is justifiable to consider goat and sheep milk to be natural functional milks (Assis et al., 2016).
Production of sheep milk : Milk plays a tremendous role in building a healthy society and can be used as a vehicle for rural development, employment, and slowing down the migration of the rural population. Of the total sheep milk production, about 61% of the world’s sheep milk is produced in the Mediterranean region and the Middle East and is mainly used as a raw material for producing cheese and other dairy products. In 1989, 87, 78,000 tons of sheep milk was produced worldwide (Kalyankar et al., 2016.) Sheep milk dairy products are considered a delicacy because of their quality and nutritional value; therefore they have gained market size worldwide in the last decade (Milani and Wendor, 2011 and Pulina et al., 2018). Sheep and goat milk accounts for 36.5% and 63.5%, respectively of the world’s total small ruminant milk production (FAO, 2017). Conventionally any breed of sheep can be milked, but some breeds are excellent milk producers .
Composition of sheep milk :
On average, the gross composition of sheep milk expressed in g per100g milk is as follows (Alichanidis, et al., 2016): total solids 17.8%, fat 7.4%, protein 5.7%, lactose 4.8% and ash 0.9%. Sheep milk (SM) is increasingly used for the production of different milk products like cheese, yogurt, ice-cream, etc. and has economic value for countries bordering the Mediterranean Sea, sub-Saharan Africa, Middle East, and East and Southeast Asia (Balthazar et al., 2017). Milk proteins include casein complexes (80%) and whey proteins (20%). The whey protein fraction contains several extremely important ingredients, including lysozyme, lactoperoxidase or lactoferrin (Jilo, 2016). An important endogenous amino acid of sheep’s milk protein is proline, which plays a key role in the synthesis of arginine and polyamines (Wu et al., 2011). Both proline and hydroxyproline are found in the highest amounts in sheep’s milk proteins (Table 2) and collagen.
Importance of sheep milk:
Fermented beverages made from sheep’s milk are characterized by good antibacterial properties, due to the presence of bioactive compounds such as catechol, vanillin, ferulic acid and salicylic acid. Additionally, ker is rich in vitamins such as B1, B2, B5 and C; minerals; and amino acids that are essential for the healing process and homeostasis (Farag et al., 2020). Currently, sheep milk is considered a delicacy in many countries, including the United States. Therefore, sheep dairy products have gained market size due to the product’s quality, high yield and nutritional value; the high nutritional value is due to the higher concentrations of proteins, fats, vitamins and minerals when compared to the milk from other domesticated mammals (Park et al., 2007 and Milani and Wendorff, 2011). Thomas, 2011 said that, in a dairy sheep operation, milk is one of three major products – the other two being meat and wool. Lamb and wool will be a major source of income from a dairy sheep operation and their production must receive adequate attention in order to maximize returns. Milk can be sold to a processor for conversion to cheese (yogurt and ice cream also are made from sheep milk) or the milk can be processed by the producer and marketed as a value added product. Before venturing into the processing of sheep milk, producers must make sure they have the necessary processing and marketing skills and a ready market for the final product. It probably is a good idea to first concentrate on the production of milk from sheep for sale to a processor. The concentrations of Ca, P, Fe and Mg in sheep milk are 193, 158, 0.08 and 18 mg 100g-1 milk, respectively (Park, 2007b). Moreover, in this expanding food sector, prebiotics and probiotics are key ingredients and successful examples of functional food classes that promote health and wellness. Prebiotics are “substrates that are particularly used by host microorganisms, which confer a health aid” (Gibson et al., 2017). A review by Paccard and Lagrioul (2006a) and (2006b) for sheep milk, demonstrated the high content in B vitamins especially niacin. Milk is a valuable source of vitamins, both water-soluble and fat-soluble ones. Goat and sheep milk is characterized by higher vitamin A concentrations in comparison with cow milk (Park et al., 2007a). The quality of sheep milk has paramount importance in controlling the quality of dairy products (cheese, butter, Ghee) made from it. In the world, most the sheep’s milk is transformed into cheese and yogurt. In Asian and African countries, sheep milk is transformed into butter and ghee. Fresh sheep milk is rarely consumed because of its high fat and total solid contents. Total cheese production from sheep milk in the world is 680.30 million kg and butter and Ghee is 63.25 million kg (FAO 2016). Mohapatra et al. (2019) review reveals that, sheep milk has a positive effect on bone growth, skin moisturizing, blood vascular system and cardiac health. The signicant impact of sheep milk on human health importance is a neglected area of research. An ample of opportunities is there for sheep milk to process and to consider sheep milk not only a source for delicious cheese and creamy yogurt, but to appraise it as a vehicle for good health. Balthazar et al. (2017) said that, sheep milk is an excellent source of nutrients and is mainly used for cheese production due to its high total solids content, contributing to a high cheese yield. However, the functional benets of this food matrix remain unexplored by the dairy industry. The development of products on an industrial scale requires technical knowledge and adaptations of the existing protocols due to the intrinsic characteristics of this matrix. Muldasheva et al. (2019) study says that, sheep’s milk is characterized by a high fat content, more than sufficient protein content, for the production of yogurt and fermented milk products such as Kurt. Sheep’s milk is biologically valuable raw milk and its development as a reserve capacity for the production of dairy products is of scientific and practical interest and economic benefit.
Opportunities for sheep milk in food industry:
Sheep milk is considered to be a healthy alternative to cow and goat milk. The extensive sheep farming, the high nutritional value of sheep milk, increasing health consciousness, exploitation of cow milk production, enhancement in palatability and flavor in the products, an alternative to cow and goat milk, resistance to certain diseases, immunity booster, government policies and initiatives, the surge in disposable income, advanced technology, investment in R and D and launch of innovative products are the key drivers which lead the growth of sheep milk market. However, alternative dairy products at a low price, availability of plant-based milk, traditional manufacturing practices, restrictions and regulations on certain ingredients to be used in products and increasing competition hinder the market growth (https:// www.alliedmarketresearch.com/sheep-milk-marketA07503). Balthazara et al. (2019) said that, ultrasound treated sheep milk, could be advantageous Compared to HTST pasteurization, since the ultrasound processing could preserve some lactic acid bacteria while inactivate a satisfactory amount of contaminant bacteria in the frozen stored milk. In addition, no relevant change was noted on protein or free amino acid prole of pasteurized or US-treated semi-skimmed sheep milk, proving that this technology could be used in milk to produce sheep milk products such as cheeses, maintaining the product quality. Overall, ultrasound processing should be considered by the sheep milk industry. The highest concentration of this, and other mineral elements, is specic to sheep milk. Kalyankar et al. (2016) said that, the milking of sheep dates back to the domestication of animals. In many countries, the cow has replaced the sheep as the major milk producer, but the sheep and goats remain important sources of milk in countries where land is too poor to support cows. To generate alternative farm income, there has been a huge interest in sheep dairying in northern Europe, Australia, India New Zealand and the United States. Attractions are low capital investment, Limited land requirment, high profit margins per liter, and lack of quota limits on production. Sheep’s milk is used in the production of prebiotics and probiotics and as an ingredient in infant formulas, thus being a suitable alternative to mother’s milk and for the production of nutraceuticals (Pulina et al., 2018). Owing to the content of bioactive substances, sheep’s milk can be used for the production of medical food. The great amount of fat and protein in sheep milk along with minerals makes the cheese the most important dairy product from sheep milk, due to its high yield and some technological advantages, such as high casein micelles mineralization degree and calcium rennet coagulation being not necessary addition of calcium chloride. Because of its abundant nutritional composition and benefits is used to produce many dairy products. In India, sheep rearing is mainly doing for the production of wool and meat. Now, it’s the time to explore the utilization of sheep milk for getting a newer profit way and commercialization of different products from the sheep milk boosts up the total sheep milk production in India. There are plentiful opportunities in processing of sheep milk to support poor people to generate an extra income with the scaling up of sheep milk production and development of novel food products from sheep milk.
Goat Milk as a Functional Food
Goat milk is nutritionally vital and plays a considerable role in providing essential nutrients [1-8]. It is rich in proteins, vitamins, and fatty acids that possess significant biochemical functions. Goat milk provides higher levels of calcium, potassium, and phosphorus. It is hypoallergic and its small fat globules make it easily digestible. Thus, due to its composition, it can be widely used as a functional food to upgrade health status as well as improving quality of life. Furthermore, goat milk includes quite a few bioactive peptides with effective antioxidant capacity [10-13]. There have been very few studies which have explored the role of goat milk in various degenerative diseases, memory and learning, and particularly, during aging [14]. Goat milk has better digestibility, alkalinity, buffering capacity, and certain therapeutic values in medical nutrition therapy, goat milk and its products may be an important inclusion in diet of sick and needy populations. Goat milk is a valuable source of taurine for the human neonate and the adult. Polyamines are essential for ideal growth, gastrointestinal tract (GIT) cell function, and maturation of GIT enzymes and have been implicated in minimizing the rate of food allergy in infants. Goats’ milk has some special attributes that such as alpha1-casein, resulting in softer gel products, a higher water holding capacity, and a lower viscosity.
NUTRIENTS IN GOAT MILK
Carbohydrate
Carbohydrates found in goat milk are oligosaccharides, glycopeptides, and glycoproteins which are considered to be beneficial components of human nutrition due to their prebiotic and anti-infective properties. Lactose is the major carbohydrate in goat milk. Lactose helps in intestinal absorption of calcium magnesium and phosphorous, and the utilization of Vitamin D.
Protein Content
The quantity of small-sized casein micelles is comparatively higher in goat’s milk than cow’s milk that explains the better digestibility of goat’s milk (Haenlein, 2004).
Minerals
Goat milk provides a more absorbable form of Ca and P that are needed for maintaining bone mineral density. Goat milk contains significantly greater iodine contents than human milk, which would be important for human nutrition since iodine and thyroid hormones are involved in the metabolic rate of physiological body functions (Underwood, 1977). Goat milk is rich in selenium (Se) which is a necessary nutrient for body and known for its immune strengthening and antioxidant properties.
Fat
Goat milk also has higher size of polyunsaturated fat acid as well as conjugated linoleic acid. Goat milk has lipids including gangliosides, glycolipids, glycosphingolipids, and cerebrosides that are significant bioactive components.
Vitamins
Goat milk stores enough amounts of Vitamin A and niacin. One limitation with goat milk is the almost nil content of folic acid and this problem could be solved using folate-producing bacteria during fermentation while using fermented food products with goat milk [14]. The peculiar flavor and aroma of goat milk different from cow milk constrain its acceptability among some consumers. Low daily volume is another factor for its less availability and popularity.
HYPOALLERGIC EFFECTS
Goat milk has been recommended as a substitute for patients allergic to cow milk. Between 40 and 100% of patients allergic to cow milk, proteins tolerate goat milk. Infants suffering from gastrointestinal allergy and chronic enteropathy against cow milk were reportedly cured by goat milk therapy. The higher protein, non-protein N, and phosphate in caprine milk give it greater buffering capacity compared to cow milk. Some physicochemical properties of caprine milk such as smaller fat globules, higher percent of short and medium chain fatty acids, and softer curd formation of its proteins are advantageous for higher digestibility and healthier lipid metabolism relative to cow milk.
Immunomodulation
he immunomodulatory properties of goat milk can be attributed to the compounds such as peptides and oligosaccharides that were reported to modulate host inflammatory cytokines (Daddaoua et al., 2006 and Santosh et al., 2016). The milk can trigger innate and adaptive immune responses in the human body that can help fight against inflammation (Jirillo and Magrone, 2014). Lara-Villoslada et al. (2006) reported that goat’s milk oligosaccharides decrease intestinal inflammation in rats and contribute to the recovery of damaged colonic mucosa. Furthermore, goat whey increased the expression of proteins such as mucins and occludin proteins that increase the gut barrier property.
Antiatherogenic Property
Sonu and Basavaprabhu 019 reviewed that goat milk is rich in mediumchain triglycerides (MCT) (MCT including fatty acid esters of caproic, caprylic, and capric fatty acids). These MCT have shown a lowering effect on plasma cholesterol in rat models (Alferez et al., 2001) and also to inhibit cholesterol deposition in the tissues (Babayan, 2009). Consumption of goat milk triggers the release of nitric oxide blood cells that, in turn, reach the bloodstream through the lymphatic route, thus provoking vasodilatation and exerts a cardio-protective and antiatherogenic effect (Tilahunzenebe et al., 2014). Cholesterol-lowering ability of goat milk-derived peptides and fats (Ibrahim et al., 2017; Moreno-Montoro et al., 2017; and Kalyan et al., 2017) and therefore indicating their possible role in controlling coronary artery diseases.
Lactose Intolerance
Lactose intolerance is a digestive disorder caused by the inability to digest lactose (vital milk sugar). Goat milk is an alternative source or people with lactose intolerance. Goat milk is more completely and easily absorbed than cow milk, leaving less undigested residue in the colon to ferment and cause the uncomfortable symptoms of lactose intolerance (Haenlein, 2004 and Aliaga, 2010).
Overcomes Dengue Viral Fever
Dengue, the most common major health problem (viral fever) in India, is transmitted to humans by Aedes Egypti (Neuberger et al., 2016). Treatment of dengue fever typically involves the use of goat milk and milk products since they are rich in Se (13.7 ng/mL). Nevertheless, the Se concentration in the milk depends on several factors such as feed, climatic conditions, and breed (Dael et al., 1992; Singh et al., 2016; and Zhang et al., 2018). The deficiency of Se has been positively correlated with the decrease in platelet count, which is a key marker to recognize the onset of dengue fever. Se has an anticlotting effect whereas, thrombotic or pro-clotting effects are mainly observed due to the Se deficiency.
Anticancer Properties
Several lactic acid bacteria that are isolated from goat milk have also reported demonstrating anticancer effect (Mittu and Girdhar, 2015) and therefore suggesting the use of goat milk-derived LAB for groundwork of fermented milk product yield similar therapeutic properties that the bacterial strain.
Antimicrobial Property
The total inhibitory effect of milk is generally greater than the sum of the individual antimicrobial effect of immunoglobulin and other defense proteins, namely, lactoferrin, lactoperoxidase, lysozyme, and other peptides. Therefore, the synergistic effect of naturally occurring proteins and peptides provides the antimicrobial effect. In this regard, the lacto peroxidase was found that it has inhibitory action against plethora of pathogens, namely, Vibrio cholera, Salmonella typhi, Klebsiella pneumonia [9], Shigella dysenteriae, and Staphylococcus aureus .
Ample nutritional and health benefits of goat milk are the paramount factors that need attention for nutritional therapy to use goat milk and milk products as functional foods. The better digestibility of goat milk is the key factor with the positive health effects, namely, anticancer, anti-inflammatory, antiatherogenic, and anti-allergenic diseases that make it a substantial functional food. The low allergy attributes of goat milk, its easy digestibility, the mineral contents, its composition of fatty acids, and bioactive compounds make it a vital functional food of future to be extensively used for medical nutrition therapy. Goat milk may be extensively used for beneficial effects on gastrointestinal disorders through its fermented products and its role in various degenerative diseases.
Functionality of Goat and Sheep Milk
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
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