Buffer Capacity of Cow's Milk

Abstract

Buffer capacity (β) of cow's milk was measured in the range of pH 3 to 11 with a βtitrator.β-pH curve of the milk showed strong buffer capacity in the range of pH 3 to 6 and 9 to 11, and also showed two peaks at about pH4 and 6.From the data of pK values of the weakelectrolytes in the milk, it was presumed thatorganic acids conhribute to the buffer capacityat about pH 4, and high buffer capacity at aboutpH 6 would be due to His, Cys residues, phosphoric, carbonic and citric acids.In the range of pH 9 to 11, the high buffercapacity would arise from Lys, Cys, Tyresidues and carbonate.Buffer capacity of whey was much smaller thanthat of milk, in the range of pH 3 to 6By inoculation of L. bulgaricus, the peak atpH 4 was increased.Buffer capacity of the dialyzed milk was founddecreased by about half of the original one inthe whole pH range and, therefore, it wasmilk respectively contribute to about one half of the buffer capacity of the milk.The colostrum showed twice larger buffer capacity than the normal milk and gradually decreased and reached to the normal value fo milk after about 10 days.