The composition of milk. Part II: Variation in the percentage of mineral constituents in cow’s milk, and their relationship with the solids not fat and protein content

Abstract

1. 670 samples of the mixed milk from 15 herds were analysed, and the average percentages of total ash, soluble ash, insoluble ash, lime and phosphoric acid are given. 2. Tables showing frequency distributions are also given, with the standard deviation, mean and probable error of mean for each constituent determined. 3. Various correlations of these constituents with solids not fat and protein have been prepared, and these correlations are illustrated by graphs. It is observed that the total ash falls with the solids not fat until low values of solids not fat are reached, when the ash content appears to rise. This variation is confirmed by a curve illustrating the variation in ash content of samples of individual cow’s milk. Soluble ash rises as the solids not fat falls, but the insoluble ash shows a reverse variation. Lime and phosphoric acid both fall with the solids not fat.