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Bound Water and its Relation to Some Dairy Products III. The Relation of Bound Water to Some Dairy Phenomena¹

Department of Dairy Husbandry, The Pennsylvania State College

ABSTRACT

The bound water content of the milk colloids does not appear to contribute to the creaming ability of milk. High temperature treatment of the whole milk or skimmilk is detrimental to the creaming ability and bound water content of the milk while high temperature treatment of the cream portion does not affect creaming to any great extent.

The increase of the specific gravity of fresh milk and skimmilk on aging (Rechnagel's phenomenon) is thought to be partially due to the increase in the bound water content of the proteins and other hydrophilic substances present in milk.

Vacuum roller dry skimmilk loses some of its bound water with age. The greatest amount is lost during the first few weeks of storage. The dry skimmilk stored in open containers was affected more than the dry skimmilk stored in air-tight containers.

Superheating of condensed skimmilk had no appreciable effect upon the bound water content.

Short aging periods of concentrated milk plasma at relatively high temperatures resulted in only slightly more bound water than longer aging periods at low temperatures.

Invariably aging caused an increase in bound water content, regardless of the treatment given the sample.

The Dahlberg and Hening method of increasing the viscosity of cream by temperature treatment resulted in an increase in the bound water content of the cream.

Pasteurization of milk or cream lowered viscosity and bound water content.

Homogenization of mixes with one pressure increased viscosity and decreased the bound water content, while dual homogenization of the same product showed an increase in bound water content and viscosity.

The protein stability as measured by the alcohol number usually showed little change with changes in bound water content unless large changes were noted in the amount of bound water present. However, heating of milk to high temperatures decreased the bound water content but increased the stability toward alcohol, while superheating of condensed skimmilk resulted in increased stability with practically no change in bound water content.

¹ Authorized for publication on March 11, 1938, as paper No. 827 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

² The data presented in this paper are from a thesis submitted to the Graduate School of The Pennsylvania State College in partial fulfillment of the requirements for the degree of Doctor of Philosophy, 1937.