Ganguli N C
J Dairy Res. 1979 Apr;46(2):401-5. doi: 10.1017/s0022029900017404.
Buffalo skim-milk is less heat stable than cow skim-milk. Interchanging ultracentrifugal whey (UCW) and milk diffusate with micellar casein caused significant changes in the heat stability of buffalo casein micelles (BCM) and cow casein micelles (CCM). Buffalo UCW dramatically destabilized CCM, whereas buffalo diffusate with CCM exhibited the highest heat stability. Cow kappa-casein stabilizes alphas-casein against precipitation by Ca better than buffalo kappa-casein. About 90% of alphas-casein could be stabilized by kappa:alphas ratios of 0.20 and 0.231 for cow and buffalo, respectively. Sialic acid release from micellar kappa-casein by rennet was higher than from acid kappa-casein in both buffalo and cow caseins, the release being slower in buffalo. The released macropeptide from buffalo kappa-casein was smaller than that from cow kappa-casein as revealed by Sephadex gel filtration. Sub-units of BCM have less sialic acid (1.57 mg/g) than whole micelles (2.70 mg/g). On rennet action, 47% of bound sialic acid was released from sub-units as against 85% from whole micelles. The sub-micelles are less heat stable than whole micelles. Among ions tested, added Ca reduced heat stability more dramatically in whole micelles, whereas added phosphate improved the stability of micelles and, more strikingly, of sub-micelles. Citrate also improved the heat stability of sub-micelles but not of whole micelles.
水牛脱脂乳的热稳定性低于牛乳脱脂乳。用胶束酪蛋白互换超离心乳清（UCW）和乳扩散液会导致水牛酪蛋白胶束（BCM）和牛乳酪蛋白胶束（CCM）的热稳定性发生显著变化。水牛UCW会使CCM显著不稳定，而水牛扩散液与CCM混合时表现出最高的热稳定性。牛κ-酪蛋白比水牛κ-酪蛋白更能稳定α-酪蛋白，使其不易被钙沉淀。对于牛和水牛，κ:α比值分别为0.20和0.231时，约90%的α-酪蛋白可被稳定。在水牛和牛乳酪蛋白中，凝乳酶从胶束κ-酪蛋白中释放的唾液酸均高于从酸性κ-酪蛋白中释放的唾液酸，且在水牛中释放速度较慢。通过葡聚糖凝胶过滤显示，水牛κ-酪蛋白释放的大肽比牛κ-酪蛋白释放的小。BCM的亚基含有的唾液酸（1.57毫克/克）比完整胶束（2.70毫克/克）少。在凝乳酶作用下，亚基中47%的结合唾液酸被释放，而完整胶束中这一比例为85%。亚胶束的热稳定性低于完整胶束。在所测试的离子中，添加钙会使完整胶束的热稳定性下降得更显著，而添加磷酸盐可提高胶束的稳定性，更显著的是提高亚胶束的稳定性。柠檬酸盐也能提高亚胶束的热稳定性，但不能提高完整胶束的热稳定性。
