Study On The Nutritional Components And Special Functional Components Of Qinghai Xueduo Yak Milk

Yak milk is a rare milk source with high nutritional value,which is rich in a variety of functional components and plays an important role in promoting human health.Cow milk is the most common milk source in life.Compared with ordinary cow milk,yak milk has certain differences in the composition and content of nutrients,and its function in human body is also different.In this experiment,Qinghai Xueduo yak milk was used as the research object,and compared with cow milk,the conventional nutrients,mineral elements,amino acids,fatty acids and volatile flavor substances of the two milk sources were determined.The differences in conjugated linoleic acid(CLA),A1,A2 β-casein,osteopontin(OPN)and protein digestibility were also determined.Further using buttermilk,a by-product of dairy processing,the fat globule membranes of two milk-derived buttermilk were determined(MFGM)in proteins and lipids.And carried out the preliminary development of yak milk products rich in functional ingredients.The protein content(4.04%),fat content(7.4%)and lactose content(5.51%)of yak milk were significantly higher than those of cow milk.Among the mineral elements,there are high contents of Ca and Fe in Xueduo yak milk,and a good ratio of calcium to phosphorus.The essential amino acids in yak milk accounted for 44.64% of the total amino acids,and the ratio of essential amino acids to non-essential amino acids was 80.63%,indicating that the ratio of amino acids was better than that of cow milk.The proportion of medium and long-chain fatty acids in yak milk was high,the relative contents of polyunsaturated fatty acids and monounsaturated fatty acids were higher than those of cow milk,but the relative contents of oleic acid,linolenic acid and linoleic acid were lower.The content of CLA in yak milk was 1.53 mg/m L,while that in cow milk was only 0.79 mg/m L.There were differences in the composition and content of flavor substances in yak milk and cow milk,and the flavor substances in yak milk were more abundant.Among yak milk proteins,the content of β-casein is the highest,but the content ofαs2-CN and α-La is lower than that of cow milk.Under the same digestion conditions,the digestibility of yak milk whole protein was lower than that of cow milk,but the digestibility of whey protein was higher than that of cow milk.The proportion of yak milk A2 β-casein in the total β-casein is smaller than that of ordinary milk,indicating that yak milk may not be the source of A2 milk.Compared with cow milk,yak milk has a higher concentration of OPN,up to 82.6 mg/L,which is second only to breast milk.445 proteins were identified in yak buttermilk MFGM by label-free quantitative proteomics,of which 232 were specifically expressed.The main biological processes and cellular components involved in the differentially expressed proteins are different,and the main molecular functions mainly focus on the structural constituent of ribosome,RNA binding and catalytic activity.The differentially expressed proteins also participated in a variety of metabolic pathways,and the interactions between proteins were strong.The contents of phosphatidylcholine(PC)and phosphatidylethanolamine(PE)in yak buttermilk MFGM lipids were higher,and the contents of various lipids and total lipids measured were higher than those of ordinary milk.