The global goat milk market is estimated to reach revenues of around $15 billion by 2024, growing at a compound annual growth rate (CAGR) of more than 7% during 2018-2024. Some studies have been carried out to explore many designed fermented dairy products with increased participation of bioactive ingredients in goat milk which leads to excellent biological effects and have shown higher therapeutic & nutritional value. Medicinal properties of goat milk increased the interest of society to use it as therapeutic health food neutraceutical and a therapy against different problems including gastrointestinal disturbances, vomiting, colic, diarrhoea, constipation and respiratory problems.
Thus, future studies on recent advancements in the functionality of the components from goat milk & its products
Keywords: Goat; Milk, Goat products, prebiotic, functional, bioactive components, and fermented food.
Goats are known as “Wet nurse of infants” in the United Kingdom and “Poor man`s cow” in India due to its contribution to rural economy. One of the best feature in goats is they are easily adapted into harsh climates, which make the m suitable for landless and marginal farmers.
The contribution of goats in supplying milk and milk products is high and it has significant role in rural economy and health (Zenebe T. et al., 2014). Goat’s milk also possess health-promoting compounds, such as bioactive peptides; conjugated linoleic acids; and oligosaccharides (Abeijón Mukdsi, Haro, González, & Medina, 2013; Assis et al., 2016; Kullisaar et al., 2003; Salva et al., 2011; Songisepp et al., 2005). Dairy goat farming plays a vital role in the diet and economy of many developing countries.
Goats’ milk is one of the principal sources of animal protein, calcium, and phosphorus in many regions, such as the Middle East, Southern Asia, and some tropical countries. It is consumed as an appropriate substitute for cows’ milk allergy consumers. Such specialities of goat milk create knowledge of nutrition-health relation and result in the development of the functional food concept. Functional foods market is organized by carotenoids, dietary fibers, fatty acids, minerals, prebiotics/probiotics/symbiotics, vitamins and minerals. The foods including phytochemicals, enzymes, and antioxidants are also increasing their market share continually (Ortiz, García-Amézquita, Acosta, & Sepúlveda, 2017).
Functional dairy products are the 40% of functional foods created prominent sector in the market. Yogurt and yogurt-type functional products including low-lactose or lactose free products and those supplemented with functional ingredients such as minerals, vitamins, conjugated linoleic acid (CLA), sterols/stanols as well as probiotics/prebiotics are experiencing the market success for a long time (Ortiz, García-Amézquita, Acosta, & Sepúlveda, 2017). Nowadays, functional food products can be obtained by using functional ingredients to food, through processing and production methods which enables the preservation of native active compounds in a specific product (Komes et al., 2017). In this sense, goat’s milk products with these properties could boost the sector through the development of innovative products and increase consumer demand (Aguilar-Toalá et al., 2018).
Goat milk as a potential functional food, taking into consideration the use of prebiotics and probiotics is an emerging area to the development of goat’s milk products. Prebiotics are defined as the indigestible food ingredients that promote the growth or activity of beneficial bacteria, thereby benefiting the host. Prebiotics are being added to the food products to stimulate the colonic microflora to get health benefits to the consumers, besides providing textural attributes to the foods (Saad et al. 2013). However, The word probiotic is coined by Kollath (1953) and is derived from the Greek language, which means “for life”. Goat milk acts as a main probiotic carrier into humans. These products can be considered as suitable vehicles for delivering probiotics to humans due to their ability in maintaining sufficient probiotic viability during shelf life. However, dairy products produced with bovine milk represent the major share of the probiotic market, with only a relatively small number of studies examining functional probiotic goat milk products (Turkmen, Akal, & O¨ zer, 2019).
According to Lilly and Stillwell (1965), probiotics are substances produced by microorganisms that promote the growth of other microorganisms. According to FAO/WHO (2001), probiotics are defined as “live microorganisms that, when administered inadequate amounts, confer a health benefit to the host.” The current review aims to show a complete picture of the current knowledge regarding the recent advancements in the functionality of the components from goat milk & its products. The necessary speculative contextual and some details about the use of prebiotics and probiotics/bioactive components in goat milk products has also been discussed. It also summarizes the most recent studies on goat milk and human health and critically, discusses the putative actions of principal goat milk components & goat milk products.
According to the United Nations’ Food and Agriculture Organization (FAO) statistics goat milk is the world’s third most produced variety of milk, after cattle and buffalo milk (Belewu and Adewole, 2009). In 2016, approximately 1 billion goats worldwide with a milk production of 15.262.116 tons (FAO stat, 2018). India is leading country in goat’s milk production after that, Bangladesh and Pakistan in Asia; whereas Sudan, South Sudan and Somalia in Africa; with France, followed by Spain, and Greece are the major producers in Europe. Although America is significantly rising as goat’s milk production. (Verrruck S. et al., 2019). The global goat milk market is estimated to reach revenues of around $15 billion by 2024, growing at a compound annual growth rate (CAGR) of more than 7% during 2018-2024. Also, goat’s milk production increased more than two-fold in the last decades, with market trends suggesting that by 2030 will increase by another 53% (Pulina et al., 2018). Majority of goats used for meat production and limited for milk production. Goat rearing is the second most important activity of livestock sector. There are total 102 breeds in the world and 28 breeds in India (NBAGR, 2018; http://www.nbagr.res.in/reggot. html). 19th livestock census (2012)-135.17 million goat population, India Worldwide Annual mean milk production per goat is 84.3 kg. Annual Growth rate is 2.6%. (Annual Report CIRG, 2018).
The country stands first in goat milk production and its sharing 26.31% goat milk production in the world. The total milk production in the country 155.5 million tonnes. The total Goat milk production 5377.59 thousand tonnes (3%). (Annual Report CIRG, 2018). The global functional dairy beverages market is a very powerful sector of the dairy industry and global dairy-based beverages market is forecasted to reach a market value of 13.9 billion USD by 2021, excluding traditional dairy beverages such as kefir, buttermilk, koumiss, etc (Anonymous, 2018). Key players: Emmi Group (Switzerland), Ausnutria Dairy Ingredients (The Netherlands), The Good Goat Milk Co. (New Zealand), Hogwegt Group (The Netherlands), Delamere Dairy, Ltd. (UK), AVH Dairy (The Netherlands), Orient EuroPharma Co. Ltd. (China), Saputo, Inc. (Canada), Hay Dairies Pte, Ltd. (Singapore), and Quidditas Farms Pvt., Ltd. (India) are some of the key players in the global goat milk products market. (https://www.marketresearchfuture.com/reports/goat-milk-products-market-6480)
(Goswami M. et al., 2017) The specific composition of Goat dairy products showed remarkable characteristics in fats, proteins, amino and fatty acids as well as their levels of flavour, taste, aromas and leanness. (Boyazoglu et al., 2001) Although goat milk proteins have similarity with major cow milk proteins like á-, â-, ê-caseins, â-lactoglobulin, á-lactalbumin, but differ in genetic polymorphisms. Moreover, medium chain fatty acids like caproic, caprylic, capric have been used for the treatment of malabsorption syndromes, intestinal disorders, coronary diseases, premature infant nutrition, cystic fibrosis and gallstone problems because of their unique metabolic ability to provide energy while at the same time lowering, inhibiting and dissolving cholesterol deposits (Ariane et al., 2014). However, the most innovative feature reported regarding the composition of goat milk fats concerns their content of conjugated linoleic acids (CLA), a group of naturally occurring 18-carbon fatty acids (Amigo & Fontecha, 2011). Some CLA isomers have been shown to offer health benefits and help disease prevention (Bauman, Tyburczy, O’Donnell, & Lock, 2011). by reduces the risks of cardiovascular disease, particularly noteworthy is the recognized activity of CLA in inhibition of cancer, atherosclerosis and an improvement of immune functions as a whole (Elwood, Pickering, Givens, & Gallacher, 2010). In addition, goats’ milk attributed to individuals suffering from malabsorption syndrome due to therapeutic properties in human nutrition, such as a better utilization of fat and mineral salts. Recently, several oligosaccharides have been suggested as potentially bioactive ingredients (172).
Oligosaccharides are composed of a lactose core bound to lactose-amine units via b1–3 or b1–6 links and carrying fucose or sialic acid in their terminal position (172,174,175) which have been proposed as important for child development. Neutral oligosaccharides—namely the monomer N-acetylglucosamine and fucose—are essential for the development of the neonates because of their immunomodulating actions (176). Conversely, acidic oligosaccharides (where the monomer is sialic acid) help to prevent the adhesion of pathogens to the intestinal mucosa (177). Because of prebiotics and help to create a healthy microbiota (180–182). However, goat milk is much richer in lactose-derived oligosaccharides (lactulose, lactitol, lactobionic acid, and galactooligosaccharides), which are beneficial to humans due to their prebiotic and anti-infective features (Turkmen, 2017). Pruksasri and Supee (2013) evaluated the feasibility of producing goat milk containing galacto-oligosaccharides (GOS) by treating milk with the enzyme β-galactosidase. The results indicated that the maximum GOS obtained were approximately 13.9% of total sugars at pH 4.5 and temperature 40°C. There were significant improvement in taste and overall acceptability of goat milk containing higher GOS concentration when compared to regular goat milk (control).
Also, goat milk containing GOS presented a good stability over the acidic conditions. GOS in goat milk were also stable after the high heat treatment and shelf life conditions. (Silveira et al., 2015) formulated a probiotic goat dairy chocolate beverage with improved viscosity and sensory characteristics in which inulin with oligo-fructose in combination with goat cheese whey was used as functional ingredients. Inulin and fructo-oligosaccharides have a bifidogenic effect, that is, they stimulate the intestinal growth of bifidobacteria, which, by antagonistic effect, suppress the activity of other undesirable bacteria (Gibson et al., 2017). Goat milk has better digestibility, due to more zinc, iron, magnesium, alkalinity and buffering capacity [10, 11].
Bergillos-Meca et al. (2015) reported that the probiotic fermented milk prepared with goat’s milk concentrated by ultrafiltration improved Ca, Mg, Zn and P bioavailability also verified that the improvement of Ca retention and uptake could be attributed to a positive effect exerted by the probiotic strain (Lactobacillus plantarum C4). (Ranadheera C.S. et al., 2019) Goats transform all dietary carotene to vitamin A, and thus goat milk contains a greater level of vitamin A and is characteristically whiter in color than bovine milk (Verruck et al., 2017). Goat milk is also rich in niacin, thiamine, riboflavin, and pantothenate (Turkmen, 2017, but is a relatively poor source of vitamin B12 and folic acid, containing only 20% of the folic acid content of bovine milk and in a less bioavailable form than that found in bovine and human milk. Both goat and bovine milk are scarce in vitamins B6, D, and C (Clark & Garcia, 2017).
Goat milk is white in color and has a stronger flavor than sheep milk; it is also alkaline in nature due to higher protein content and a different arrangement of phosphates (Agnihotri and Prasad, 1993). Goats’ milk has smaller size fat globules compared to cow milk which provides a smoother texture. The lower amounts of alphas1-casein present in goat milk results in softer gel products, a higher water holding capacity and a lower viscosity. (Gomes et al., 2013). Tseng and co-investigators (2012) evaluated three types of goat milks viz. full-fat goat milk, low-fat goat milk and skim goat milk. They reported that the colour, ‘L’ value, ‘a’ value and ‘b’ value of the goat milk decreased with increased milk fat. No significant differences were found in short-chain and middle-chain fatty acid (C4-C12), saturated fatty acid (SFA), unsaturated fatty acid (UFA) or the ratio of SFA/UFA among all the three types of milks. Low fat goat milk had the highest appearance score among all the types of milks, whereas the full fat goat milk had higher aroma, flavour, tasty and overall acceptability score than the other groups. Slacanac et al., 2010) informed significant role of fermented goat milk products in securing food for rural communities by incorporation of live probiotic cells in fermented goat milk represents nutritive and therapeutic properties.
Goat milk contains much taurine, the substance added to health drink and revitalizers, a final metabolic products of sulphur containing amino acids, which may have several biological functions: modulator of growth and of neuronal activity; conjugation of bile salts; regulation of osteoblast metabolism; protection of cells against various types of injury and prevention of cardiovascular damage; treatment of fatty liver of children. and there are reports that goat milk contributed to the treatment of diabetics. (Anaeto et al., 2010) studies for the first time a drug called Aimspro made from goat blood offers hope to multiple sclerosis patients by improving their vision and to reduce an aspect of disability in the chronic phase of any treatment. Further, goats’ milk assured therapeutic properties, such as a better utilization of fat and mineral salts in individuals suffering from malabsorption syndrome. In addition, these benefits may be further enhanced by using goat’s milk as a vehicle for delivering probiotics and prebiotics.
Zhang et al. (2015) reported higher antioxidant activity and cholesterol-lowering effects in cultured goat’s milk when compared with cow’s milk fermented with bifidobacteria and lactobacilli. This is due to structural differences and the presence of higher proteolytic activity in the primary structure of goat’s milk when compared to cows. (Prasanna and Charalampopoulos 2018) showed better performances when Bifidobacterium longum subsp. infantis CCUG 52486 microencapsulated in a variety of matrices: sodium alginate (SA), sodium alginate-cow’s milk (SACM), sodium alginate-goat’s milk (SAGM) and sodium alginate-casein hydrolysate (SACH) in simulated gastrointestinal conditions. The goat milk is nutritionally and therapeutically healthy and can be used to manufacture a wide variety of products due to its chemical characteristics, including fluid beverage products (low fat, fortified, or flavored) and UHT (ultra high temperature) milk, fermented products such as cheese, buttermilk or yogurt, frozen products such as ice cream or frozen yogurt, butter, condensed/dried products, sweets and candies (Riberio and Riberio, 2010). Furthermore, goat milk recently gaining attention in forte products like cosmetic, hair and skincare products. Yet, high quality products can be achieved from fine quality goat milk which has the potential to tolerate technological treatment and be transformed into a product that satisfies the expectations of consumers, in terms of nutritional, hygienic and sensory attributes (Yalinger, 2013).
Kullisaar et al., (2003) informed antioxidative and anti-atherogenic effects from fermented goat milk (Lactobacillus fermentus ME-3) in 16 healthy subjects. Widodo et al., (2010) investigated the quality of fermented goat milk and cow milk, as well as the viability of LAB added with skim milk (18% of solids) using three separately different starters; yoghurt starter (a combination of Streptococcus thermophilus FNCC-0040 and Lactobacillus bulgaricus FNCC-0041), single starter of Lactobacillus acidophilus FNCC-0029 and Lactobacillus casei FNCC-0051. It was, found that 10.83% decrease in LAB viability in fermented cow milk and 11.40% in fermented goat milk after 28 days of storage. In conclusion, quality of fermented milk is affected by the starters applied, raw milk source and storage period. (Salva et al., 2011) demonstrated that Fermented goat milk (Lactobacillus rhamnosus CRL1505) stimulate the mucosal immune system and improve the defence against intestinal and respiratory infections in a mouse immunosuppressant model. Goat milk yogurt was manufactured with the fortification of 2% (wt/vol) each of skim goat milk powder (SGMP), sodium caseinate (NaCn), whey protein concentrate (WPC), whey protein isolate (WPI), or yogurt texture improver (YTI). “Kishk” is a traditional fermented milk of Lebanon. It is a dried mixture of yogurt and bulghur, prepared from goat milk. (Salameh and Hosri, 2016).
Concentrated yogurt (Labneh) was made of goats’ milk, cows’ milk and their mixture. Labneh produced from goat’s milk was characterized by its higher moisture, ash and fat content, but lower pH, total solids, protein and lactose content in comparison to that of the Labneh developed using cow’s milk. Labneh with goat’s milk had a higher short and medium-chain fatty acid groups (Serhan et al., 2016). Moreno- Montoro et al. (2017) explored different whey fractions by ultrafiltration process on fermented skimmed ultrafiltered goat’s milk. (Moreno-Montoro et al., 2018) manufactured a novel fermented goat milk which is a good source of nutrients, having a low lactose and fat content, high protein proportion, and good mineral concentration with putative probiotic strain Lactobacillus plantarum C4 together with L. bulgaricus and Streptococcus thermophilus. For best viscosity and syneresis and a high casein content Ultrafiltration was chosen as the skimmed milk concentration method. The viability rate of all bacterial strains was >107 cfu/mL, even after 5 weeks of storage or after in vitro gastrointestinal digestion.
Cheese is a fermented and renowned value added dairy product, which has hundreds of varieties (Pal, 2014). Sheep and goat cheeses are the first choice for connoisseurs as gastronomic and festive products. Cheeses and Yogurt from Goats’ milk product are very popular in the Mediterranean peninsula, the Middle East, southern Russia and the Indian subcontinent. Goat cheese was originated in Mesopotamia. The milk was probably made into soft cheese, and then hard, ripened goat cheeses were later developed in the Mediterranean basin countries (Jenness, 1980). (Filiz Yangilar, 2013) stated U.S. Department of Agriculture describes over 400 varieties of goat cheese and lists over 800 names of cheeses, many of which are made from goat milk or combinations of goat with cow, ewe, or buffalo milk (Pal et al., 2011). The short-chain fatty acids C6–C10 cause a sharp flavor in goats’ milk cheese.
A similar flavor may form in ewes’ milk cheese but only if growth of molds, etc., occurs (as in Roquefort cheese) or if some goats’ milk has been added, because ewes’ milk has very little lipase activity. The low level of alpha S1-casein in goats’ milk (varying from 0 to 20% of the total casein) is responsible for the short texture of goats’ milk cheese. (Walstra et al., 2006). A higher concentration of P, Fe, and Mg were reported in White Slice goat cheese than in White Slice cow cheese. “White Slice” goat cheese is traditional product characteristic for Eastern part of Croatia, as well as for Istria region. “White Slice” goat cheese has been produced on farms and some small cheese factories in East Croatia (Slaèanac et al., 2011). Oggtt is basically a hard cheese like product that is considered stable and safe dried fermented milk. It is mainly produced by Bedouins during the spring season when milk is produced in excess amount (Badriah et al., 2013).
Yogurt, fermented milks (both drinkable and spoonable) and, to a much lesser extent, cheese have long been used as probiotic carrier dairy foods (Granato et al., 2010; Özer & Kirmaci, 2011). Yogurt has long been associated with longevity and wellbeing of the people (Aryana & Olson, 2017). Up until now, many efforts have been made to give conventional yogurt additional beneficial properties by adding value added ingredients such as probiotics, prebiotics and various plant extracts (Champagne, da Cruz, & Daga, 2018; Fazilah, Ariff, Khayat, Rios-Solis, & Halim, 2018). Among such value-added fermented products, probiotic yogurt has reached a great market success during the last two decades or more. Although solid texture, high fat content and pH values of cheese offer better protection of probiotic cells against undesirable environmental conditions, probiotic cheese market is far below its market potential (Özer & Kirmaci, 2011). Probiotic dairy beverages have also long been available in the global beverages markets.
Currently, yoghurt is growing in popularity throughout the world, as people are now become aware of health benefits of probiotics in yoghurt. It is a fermented milk product that can be prepared with milk, cream, and skim milk (Pal, 2014). Goat milk yogurt is an excellent source of fatty acids, protein, and minerals; however, it is not well accepted by many consumers, due to its typical flavor derived from caprylic, capric, and caproic acids present in this milk and dairy products (Costa et al., 2014). The proximate composition of yoghurt samples with goat milk (100%, 75%, 50%, and 25%) substitution blend with cow milk revealed that goat milk yoghurt samples (100%) had the highest protein content (4.2%), Fat content (4.27%) and caproic (C6), caprylic (C8), capric (C10) and total solids (16.22%). Yoghurt containing 100% goat milk samples was rated highest for taste and 25% goat milk samples was rated least (P