h altitudes is richer in PUFA, namely CLA. As such, the resulting cheese and dairy products will have value-added nutraceutical functions.
Yak milk casein has been hydrolyzed to generate antihypertensive peptides, such as YQKFPQY (αs2-CN; f89-95), LPQNIPPL (β-CN; f70-77), SKVLPVPQK (β- CN; f168-176), LPYPYY (κ-CN; f56-61) and FLPYPYY (κ-CN; f55-61), and two novel ACE-inhibiting peptides [33,34]. These peptides are multifunctional bioactives with potential use for producing value-added functional foods and proteins . Compared to cow milk fat, n-3 PUFA in yak milk fat is extremely higher (e.g., 3.2 times) . The n-3 PUFA to n-6 PUFA ratio in yak cheese was 0.87, but only 0.20 in cow cheese. Based on the minimum healthy set ratio of >0.25 , yak cheese is considered a highly healthy food for humans. Greater CLA cis-9, trans-11 relative to cow cheese suggests more anticarcinogenic effects of yak cheese and dairy products. The amounts of CLA cis-9, trans-11 and CLA trans-11- C18:1 in yak cheese have been found to be respectively 4.2 and 4.6 times greater than that in cow cheese . Research data indicate that considerable amount of CLA cis-9, trans-11 originates directly from the rumen. To supply adequate amount of CLA cis-9, trans-11, inclusion of 100 g yak cheese in daily human diets should suffice .
The milk yield of yak and its hybrid, “khainag”, is 300 and 470 kg, respectively. The larger diameter of fat globule (5 to 6 μm) eases butter separation in yak milk, thus being suitable for milk cream making. Due to high carotene content, its butter is yellowish and quite delicious. Along with high proteins, yak milk has high acidity. Saturated and unsaturated FA comprise respectively 22% and 55.2% of total fat, with greater content of low molecular weight volatile acids, compared to cow milk . Mongolians produce from yak milk butter as well as fermented and protein products. Butter products include milk membrane (orom), and yellow and white butter. The fermented products include yoghurt and koumiss (airag). Wet and dried curds (aaruul) are among protein products. Yak milk has greater contents of total proteins (4.6% - 5.8%), total casein (4.0%) and individual caseins than cow milk. The higher β-casein (45%) and the lower α-s-casein (40%) along with somewhat higher κ-casein (15%) make yak milk a favorable food for infants as traditionally consumed by Tibetan nomads . Yak milk’s whey proteins, β-lactoglobulin and serum albumin compositions are rather similar to homologous cow whey proteins. Nonetheless, more research is needed to figure out how to optimize yak milk utilization in humans of extreme climatic environ-ments.
China may be the largest producer of naturally fermented yak milk called “kurut”. Kurut is an important food for people of Qinghai . Kurut includes products produced by natural fermentation of yak milk in a specially treated big jar for at least 7 - 8 days at 10˚C - 15˚C. These conditions generate enough acid, alcohol and flavor. A common property of kurut is the presence of alcohol and lactic acid. Kurut is almost known in all regions of Qinghai as an indigenous fermented milk product with economic and nutritional importance to the people of Qinghai . Kurut is rich in casein, immunoglobulins, serum albumin, β-lactoglobulin, α-lactalbumin, and two unknown fractions [40,41]. Kurut contains greater numbers of lactic acid bacteria and yeast than other traditional fermented milks (lactic acid bacteria counts of 9.18 ± 0.851 log cfu/ml; yeast counts of 8.33 ± 0.624 log cfu/ml) .
4. Conclusions and Implications
Milk is the most functional natural liquid because it 1) is produced from the most abundant, least digestible nutrients and 2) generously hosts numerous bioactives that function beyond calculated nutritional values. Camel milk contains less short-chain FA than cow, sheep and buffalo milks, and has about 3 times greater vitamin-C than cow milk. One kg camel milk meets 100% of daily human requirements for calcium and phosphorus, 57.6% for potassium, 40% for iron, copper, zinc and magnesium, and 24% for sodium. Camel milk has long been used to treat liver problems, lower bilirubin output, reduce vitamin inadequacy and nutrient deficiency, and boost immunity. Camel milk reduces food allergies caused by cow milk and milk products. Camel milk has low milk fat content with increased PUFA proportions. Camel milk lacks β-lactoglobulin and is rich in immunoglobulins, thus being compatible with human milk. Yak milk has greater solids, protein and fat, and is richer in PUFA and casein than cow milk. Yak cheese has about 4 times more CLA than Canadian cheddar. Yak milk casein has been hydrolyzed to produce antihypertensive peptides with multiple bioactive functions and capacities for producing value-added functional foods and proteins. More research is needed to further characterize biophysical and biochemical properties of camel and yak milks as functional substitutes for cow milk and other animal products. Persistent education and data dissemination will be a commitment for such milk natural health implications to be optimally perceived by science and public communities worldwide.
The Ministry of Science, Research and Technology (Tehran, Iran) and University of Zanjan (Iran) are thankfully acknowledged for supporting the author’s programs of optimizing science education in the new millennium.
- FAO, “Food and Agriculture Organization of the United Nations,” 2005, FAOSTAT Data. http://faostat.fao.org
- A. Nikkhah, “Ruminant Milk and Human Wellbeing: A Multi-species Review,” In: Milk Production, Nova Science Publishers, Inc., New York, 2011.
- A. Nikkhah, “Science and Pseudo Science of Milk Intake and Human Health,” In: Milk Production, Nova Science Publishers, Inc., New York, 2011.
- Y. Fukushima, Y. Kawata, T. Onda and M. Kitagawa, “Consumption of Cow Milk and Egg by Lactating Women and the Presence of Beta-Lactoglobulin and Ovalbumin in Breast Milk,” American Journal of Clinical Nutrition, Vol. 65, No. 1, 1997, pp. 30-35.
- A. Golay, “Cholesterol-Lowering Effect of Skim Milk from Immunized Cows in Hypercholesterolemic Patients,” American Journal of Clinical Nutrition, Vol. 52, No. 6, 1990, pp. 1014-1019.
- K. C. Hayes, A. Pronczuk and D. Perlman, “Vitamin E in Fortified Cow Milk Uniquely Enriches Human Plasma Lipoproteins,” American Journal of Clinical Nutrition, Vol. 74, No. 2, 2001, pp. 211-218.
- A. L. Lock and D. E. Bauman, “Modifying Milk Fat Composition of Dairy Cows to Enhance Fatty Acids Beneficial to Human Health,” Lipids, Vol. 39, No. 12, 2004, pp. 1197-1206. doi.org/10.1007/s11745-004-1348-6
- M. A. McGuire and M. K. McGuire, “Conjugated Linoleic Acid (CLA): A Ruminant Fatty Acid with Beneficial Effects on Human Health,” Journal of Animal Science, Vol. 77, No. 1, 2000, pp. 1-8.
- C. O. Tacket, G. Losonsky, H. Link, Y. Hoang, P. Guesry, H. Hilpert and M. M. Levine, “Protection by Milk Immunoglobulin Concentrate against Oral Challenge with Enterotoxigenic Escherichia coli,” New England Journal of Medicine, Vol. 318, No. 19, 1988, pp. 1240-1243. doi.org/10.1056/NEJM198805123181904
- M. Pfeuffer and J. Schrezenmeir, “Milk and the Metabolic Syndrome,” Obesity Reviews, Vol. 8, No. 2, 2006, pp. 109-118. doi.org/10.1111/j.1467-789X.2006.00265.x
- Z. Gao, J. Yin and J. Zhang, “Butyrate Improves Insulin Sensitivity and Increases Energy Expenditure in Mice,” Diabetes, Vol. 58, No, 7, 2009, pp. 1509-1517. doi.org/10.2337/db08-1637
- P. Tantibhedhyangkul and S. A. Hashim, “Medium-Chain Triglyceride Feeding in Premature Infants: Effects on Fat and Nitrogen Absorption,” Pediatrics, Vol. 55, No. 3, 1975, pp. 359-370.
- DRI, “Dietary Reference Intakes,” Recommended Intakes for Individuals, Food and Nutrition Board, Institute of Medicine, National Academies. National Academy of Sciences, Washington DC, 2007.
- Z. Farah, R. Rettenmaier and D. Atkins, “Vitamin Content of Camel Milk,” International Journal for Vitamin And Nutrition Research, Vol. 62, No. 1, 1992, pp. 30-33.
- B. B. Khan and A. Iqbal, “Production and Composition of Camel Milk: Review,” Pakistan Journal of Agricultural Science, Vol. 38, No. 3-4, 2011, pp. 3-4.
- M. M. Khan and S. Al-Bukhari, “Translation of the Meanings of the Koran,” Al-Medina Islamic University, Saudi Arabia, 1974.
- Y. Shabo, R. Barzel, M. Margoulis and R. Yagil, “Camel Milk for Food Allergies in Children,” Immunolology & Allergy, Vol. 7, No. 12, 2005, pp. 796-798.
- R. Yagil, “Camels and Camel Milk,” FAO (Food and Agricultural Organization of the UN), Rome, 1982.
- F. Al-Hashem, M. Dallak, N. Bashir, M. Abbas, R. Elessa, M. Khalil and M. Al-Khateeb, “Camel’s Milk Protects against Cadmium Chloride Induced Toxicity in White Albino Rats,” American Journal of Pharmacology and Toxicology, Vol. 4, No. 3, 2005, pp. 107-117.
- Ch. Tsetsegmaa, D. Altaibayar, P. Dolgorsuren, G. Munh-Erdene and U. Erdenebileg, “Camel Milk Value Chain Assessment Report,” Swiss Agency for Development and Cooperation (SDC), 2008.
- Sh. Jadambaa, Ts. Batsuh and P. Baigalmaa, “Research on Use of Camel Milk to Treat Liver Diseases,” Product of Technical University, No. 8, 2000, pp. 17-21.
- R. Indra, A. Magash and N. Biichee, “Camel Research,” Paper 303, Ulaanbaatar, Mongolia, 1998.
- R. Indra and Osorhaan, “Industrial Processing of Camel Milk,” Agricultural Magazine, No. 1, Ulaanbaatar, 1987, pp. 303-304.
- U. Merin, S. D. Bernstein, N. Bloch-Damti, R. Yagil, C. van Creveld and P. A. Lindner, “Comparative Study of Milk Proteins in Camel (Camelus dromedarius) and Bovine Colostrums,” Livestock Production Science, Vol. 67, No. 3, 2001, pp. 297-301. doi.org/10.1016/S0301-6226(00)00198-6
- A. A. Akhundov, B. Dyrdyev and E. R. Serebryakov, “Effect of Combined Treatment on Water Electrolyte Exchange in Pulmonary TBC Patients,” Zdravookhr Turkm, Vol. 16, 1972, pp. 40-44.
- S. A. Yasin and A. Wahid, “Pakistan Camels. A Preliminary Survey,” Pakistan Agriculture, Vol. 8, No. 3, 1957, pp. 289-297.
- R. Pant and P. Chandra, “Composition of Cow and Camel Milk Proteins and Industrial Casein,” Milchwissenschaft, Vol. 35, No. 2, 1980, pp. 91-93.
- F. N. Talpur, N. N. Memon and M. L. Bhanger, “Comparison of Fatty Acid and Cholesterol Content of Pakistani Water Buffalo Breeds,” Pakistan Journal of Analytical and Environmental Chemistry, Vol. 8, No. 1-2, 2007, pp. 15-20.
- G. H. Wiener, H. Jianlin and L. Ruijun, “Origins, Domestication and Distribution of Yak,” The Yak, 2nd Edition, RAP Publication; FAO (Food and Agricultural Organization of the United Nations) Regional Office for Asia and the Pacific, Bangkok, 2003, pp. 1-16.
- S. Dong, R. Long and M. Kang, “Milking Performance of China Yak (Bos grunniens): A Preliminary Report,” African Journal of Agricultural Research, Vol. 2, No. 3, 2007, pp. 52-57.
- D. B. Mondal and R. N. Pal, “Yak Milkschemical Constituents,” Indian Journal of Dairy Science, Vol. 46, No. 4, 1996, pp. 413-414.
- D. Neupaney, J. Kim, M. Ishioroshi and K. Samejima, “Study on Composition of Nepalese Cheeses, Yak Milk, and Yak Cheese Whey,” Milk Science, Vol. 46, No. 2, 1997, pp. 95-102.
- J. Jiang, S. Chen, F. Ren, Z. Luo and S. S. Zeng, “Yak Milk Casein as a Functional Ingredient: Preparation and Identification of Angiotensin-I-Converting Enzyme Inhibitory Peptides,” Journal of Dairy Research, Vol. 74, No. 1, 2007, pp. 18-25. doi.org/10.1017/S0022029906002056
- X.-Y. Mao, J.-R. Nib, W.-L. Sunb, P.-P. Haob and L. Fan, “Value-Added Utilization of Yak Milk Casein for the Production of Angiotensin-I-Converting Enzyme Inhibitory Peptides,” Food Chemistry, Vol. 103, No. 4, 2007, pp. 1282-1287. doi.org/10.1016/j.foodchem.2006.10.041
- M. M. Or-Rashid, N. E. Odongo, B. Subedi, P. Karki and B. W. McBride, “Fatty Acid Composition of Yak (Bos grunniens) Cheese Including Conjugated Linoleic Acid and Trans-18:1 Fatty Acids,” Journal of Agricultural and Food Chemistry, Vol. 56, No. 5, 2008, pp. 1654-1660. doi.org/10.1021/jf0725225
- A. P. Simopoulos, “The Importance of the Ratio of Omega-6/Omega-3 Essential Fatty Acids,” Biomedical Pharmacotherapy, Vol. 56, No. 8, 2002, pp. 365-579. doi.org/10.1016/S0753-3322(02)00253-6
- H. Li, Y. Ma, A. Dong, J. Wang, Q. Li, S. He and J.-L. Maubois, “Protein Composition of Yak Milk,” Dairy Science and Technology, Vol. 90, No. 1, 2010, pp. 111-117. doi.org/10.1051/dst/2009048
- P. Cheng, “Livestock Breeds of China: Animal Production and Health” Paper 46 (E, F, S), FAO, Rome, 1984.
- Y. Cao, W. Gan, Z. Ye, H. Yu, B. Huang, Y. Jiang, et al., “Investigation on Yak Milk Products and Their Traditional Process Craft of Daocheng Country,” Proceedings of 4th International Congress on Yak, Research Institute of Animal Science and Veterinary Medicine of Ganzi Prefecture, 2004, pp. 4-67.
- H. Zhang, J. Xu, M. Wang, T. Sun, H. Li and M. Guo, “A Survey on Chemical and Microbiological Composition of Kurut, Naturally Fermented Yak Milk from Qinghai in China,” Food Control, Vol. 19, No. 6, 2008, pp. 578-586. doi.org/10.1016/j.foodcont.2007.06.010
- X. X. Zhao, “Milk Production of Chinese Bactrian camel (Camelus bactrianus). Milk production of Chinese Bactrian Camel (Camelus bactrianus),” Proceedings of the Workshop on Dromedaries and Camels, Milking Animals, Nouakchott, 24-26 October 1994, pp. 101-105.