Study On Nutritional Quality For Different Raw Milk

In this paper, we choose milk of Holstein, yaks, buffalo (Murrah, Nil-Rovo, first and highcrossbreed generation) and Jersey as study objects, and contents of protein, amino acids, fatty acids aswell as the flavor were tested. In addition, principal component analysis and discriminatoryanalysis were used for analysis the fatty acids of different raw milks, in order to establish the fatty acidfingerprint of milk, and then provide data base for the adulteration of milk. The main results are asfollows:(1) Study of conventional nutrients indicated that: breed significantly influenced the nutrientcontents. milk fat contents ranged from3.70%to8.69%, ptotein contents ranged3.15%to5.78%,lactose contents were in the range of4.59%～5.17%, and the total solid ranged from12.24%to19.88%.(2) Seasons had no significant effects on conventional nutrients of Holstein milk: fat, protein, totalsolid get the highest value in the autumn (October or November) and lowest in thesummer (June or July), respectively; somatic cell counts were significantly lower in winter than insummer. Parities had no significant effect on fat contents of Holstein milk in Beijing. Protein,lactose and total solid had opposite trend with the parities, the third and fourth parities got thelowest value, respectively; and rose again in the fifth parities.The contents of protein and total solid ofmilk in Beijing area were slightly higher than Heilongjiang area, no significant difference was foundin fat content between the two regions.(3) SDS-PAGE electrophoresis showed: the main proteins of the7kinds of milkare BSA, α-CN, β-CN, κ-CN, α-La and β-Lg, buffalo milk protein was more abundant, there wereunknown protein bands in63~79kDa and61kDa of crossbreed buffalo milk, we concluded that theseproteins may be based on hybridization. Grayscale scan showed: Holstein milk had a higher β-CN(27.81%) and β-Lg (19.97%), the contents of α-CN (34.81%) and κ-CN (13.21%) were relative higherin Jersey milk than other milk’s; yak had a higher contents of β-Lg (20.35%) and BSA (3.75%) thanothers, the ratio of β-Lg/α-La (1.39～1.58) was low in buffalo milk.(4) Native-PAGE showed that: there is a protein with migration rate of0.580(named protein A) inmilk of yak, buffalo, and Jersey, and buffalo milk contains proteins whose migration rate is0.555(named protein B) and0.387(protein C). According to the reference, protein A and B may be bubalineβ-Lg and α-La, respectively. Native-PAGE electrophoresis of Holstein shows three different results:2/3of the Holstein milk contains BSA, α-La, β-LgA and β-LgB;11.29%Holstein milk contains BSA, α-Laand β-LgA, but without β-LgA, while the other20.96%contains BSA, α-La and β-LgB, but lack ofβ-LgA.80%of the yaks milk contain protein A and without β-LgA,13.3%of the yaks milk containprotein A and without β-LgB,6.7%of the yaks milk contain four kinds of proteins as well as protein A.(5) According to the results of GC analysis: C14:0, C16:0, C18:0, and C18:1c9are the majorfatty acids of the seven kinds of milk. The contents of C4:0, C14:0and C16:0of buffalo weresignificantly higher than the other three kinds of milk, while C18:0and C18:1c9significantly lowerthan the other several milk; the contents of C14:0and C16:0of yak milk was significantly lower than other milk, and the contents of C18:1t11(9.28g/100g)and CLA (1.83g/100g) were higher than others.Jersey milk has a high content of C18:0. Parities have no significant effects on the contents of fattyacids of Holstein milk.(6)Discriminat analysis was used to analysis19kinds of fatty acids in milk, and milk can beclassified into7categories(Holstein, yak, Jersey, Nili-Rafi, Murrah, first crossbreed generation buffaloand high crossbreed generation buffalo),6categories (Holstein, yak, Jersey, Nili-Rafi, Murrah,crossbreed buffalo) and4categories (Holstein, yak, Jersey, buffalo), respectively, and the discriminaterates were83.6%,89%and97.3%, the cross-validation rates were:79.5%76.7%and91%, whichsuggested that milk fatty acids can be used as one of the indicators of milk classification.(7) Electronic nose can distinguish yak milk from other milk, and milk treated with differenttemperature can also be distinguished well by electronic nose.