Sukhija P S, Palmquist D L
Department of Dairy Science, Ohio Agricultural Research and Development Center, Ohio State University, Wooster 44691.
J Dairy Sci. 1990 Jul;73(7):1784-7. doi: 10.3168/jds.S0022-0302(90)78858-3.
Dissociation of 5% solutions of calcium soaps of soya, tallow, stearic acid, and palm fatty acid distillate was studied by titration with 1 N HCl. Release of calcium ions was directly correlated with decrease in pH value. Estimated pKa values were 5.6, 4.6, 4.5, and 4.5 for calcium soaps of soya, palm fatty acid distillate, tallow, and stearic acid, respectively. Dissociation of 5% solutions in acetate buffer at pH values of 5.0, 5.5, 6.0, and 6.5 was measured in terms of release of soluble calcium. Dissociation was maximum at pH 5.0, minimum at pH 6.5, and dependent on unsaturation of fatty acids in the soaps. Soluble calcium in the acetate-buffered rumen fluid was higher than predicted from pKa of calcium soaps, due to formation of soluble calcium acetate; however, the relative patterns were similar to their pKa values. Unsaturated soaps are less satisfactory for maintaining normal rumen function, because dissociation is relatively higher. Calcium soaps of palm fatty acid distillate were satisfactorily stable to pH 5.5.
采用1N盐酸滴定法研究了大豆、牛脂、硬脂酸和棕榈脂肪酸馏出物的5%钙皂溶液的离解情况。钙离子的释放与pH值的降低直接相关。大豆钙皂、棕榈脂肪酸馏出物钙皂、牛脂钙皂和硬脂酸钙皂的估计pKa值分别为5.6、4.6、4.5和4.5。通过测定可溶性钙的释放量来衡量5%溶液在pH值为5.0、5.5、6.0和6.5的醋酸盐缓冲液中的离解情况。离解在pH 5.0时最大，在pH 6.5时最小，并且取决于皂中脂肪酸的不饱和度。由于形成了可溶性醋酸钙，醋酸盐缓冲瘤胃液中的可溶性钙高于根据钙皂的pKa预测的值；然而，相对模式与它们的pKa值相似。不饱和皂在维持正常瘤胃功能方面不太令人满意，因为离解相对较高。棕榈脂肪酸馏出物的钙皂在pH 5.5时具有令人满意的稳定性。
