Casein number of Holstein milk and relation to whey proteins
1991
Suzuki, I. (National Inst. of Animal Industry, Kukizaki, Ibaraki (Japan)) | Furukawa, S. | Someya, Y. | Yoshino, M.
Determination was made of casein and whey proteins (alpha-lactalbumin, beta-lactoglobulin, proteose peptone,and gamma-globulin) in individual Holstein cow milk. Milk samples were obtained from herd in 3 prefectures (Hokkaido, Ibaraki and Chiba) and from an experimental herd at the National Institute of Animal Industry (Chikushi). Morning milk from each of 5 cows from each herds was collected bimonthly 6 times between Jan. to Nov. l989 (total 120 samples). Casein number (casein % of total milk protein, casein No.) and its relation to whey protein was discussed. Average casein No. of all samples was 76.7+-2.1%. However a very low casein No. was observed in Chikushi herd milk (March; 67.5+-1,9%), Ibaraki (Jan.; 71.6+-2.2%) and Chiba (July; 72.2+-2.5%). Total milk protein content in low casein No. milk was not low compared to that in high casein No. milks, thus showing low casein No. milks to contain many whey proteins. Beta-Lactoglobulin is the main whey protein that compensates for lower casein contents. Increased proteose was found in milk of low casein No. alpha-Lactalbumin content was nearly constant in all milk samples. When milk was centrifuged at 1,500 x g for 30 min at 5 degrees C. for skimming, 9 out of 24 herd milk samples showed more than 4% (average of 5 individual cow milks) precipitation of casein
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