350. The effect of sodium chloride on thepH values of milk and of butter serum

Abstract

The addition of 10% of sodium chloride to milk caused an average drop inpH of 0·42 unit. Different workers have found very variable relations between thepH of cream and thepH of salted butter churned from it. When 10% of sodium chloride is added to 0·2% solutions of sodium citrate or sodium phosphate there is a drop inpH of the order of 1 unit. When an alkaline solid phase is present as in the serum of neutralized cream and butter, and in milk, this change inpH may be diminished or reversed, possibly by increased solubility of the alkaline precipitate in sodium chloride solution. Factors are listed which will cause thepH of salted butter to differ from that of the cream from which it was made. In the churning of alkaline creams there occurs in the butter an increase in the proportion to the serum water of calcium phosphate and of other solids-not-fat.