87. Factors Affecting the Solubility of Milk Powders. III. Some Physico-chemical Properties of Concentrated Solutions of Milk Solids

Abstract

1. The effect of increasing concentrations of milk solids on the degree of ionisation of electrolytes cannot be measured by determinations of electrical conductivity, owing to the influence of viscosity on ionic mobility.2. An approximately linear relationship exists between concentration of milk solids and the freezing-point depression. Above a certain concentration (equivalent to 34 g. milk solids per 100 g. of water), however, the solutions are saturated with respect to lactose, and any increase in freezing-point depression beyond this point is limited to that due to the other osmotically active constituents of milk.3. There is no evidence of the existence of “bound” water in solution of milk solids up to concentrations equivalent to 65 g. milk solids per 100 g. water.4. An approximately linear relationship exists between concentration of milk solids and hydrogen-ion concentration, increase in the concentration of milk solids resulting in a markedly increased acidity.5. The applications of these results to the heat coagulation of evaporated and dried milks are briefly discussed.