Changes of Calcium Phosphate Partition and Heat Stability During Manufacture of Sterilized Concentrated Milk

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Abstract
Changes of partition of Ca and Pi during the manufacture of concentrated milk were examined. Because of the difficulty in separating concentrated milk into colloidal and dispersal phases, preliminary separation of some fat and protein was effected by ultracentrifugation. The resulting serum was separated into a colloidal-free phase by ultrafiltration, and volume correction factors were obtained by measurement of the completely soluble Cl- in the initial milk and in its ultrafiltrate. During processing of milk, both Ca and Pi are transferred progressively from the soluble to the colloidal phase, and during heat sterilization the process continues up to the clotting point. The effect that mineral equilibria in evaporated milk have on its heat stability is considered together with other factors such as the ratio of fat:protein and conditions under which the interface of fat:protein is formed. When other factors are constant, changes of mineral equilibria will have a pronounced effect on heat stability.