Seasonal Variations in the Heat Stability of Concentrated Milk: Effect of Added Phosphates and pH Adjustment

Abstract

Natural variations in heat stability of 31% total solids concentrated milk have been surveyed over a 1-yr period. Very small variations occurred, and no distinctive instability period was observed. The stabilizing effect of pH adjustment with NaH2PO4·Na2HPO4 or NaOH·HC1 before sterilization was studied. The phosphates produced better stabilization than the acid-base combination at any pH between 6.0 and 7.0. The effectiveness of Na2HPO4 showed seasonal variations: the effects were marked on summer milks and smaller in winter milks. Conversely, seasonal variations were observed in the buffer capacity of the concentrates. The results emphasize the possibility of a specific stabilization mechanism by phosphate salts on concentrated milks. © 1991, American Dairy Science Association. All rights reserved.