EFFECTS OF COMPOSITION AND CONCENTRATION OF DAIRY LIQUIDS ON FOULING STRUCTURE

The occurrence of a maximum in the amount of deposit formed on hot sur faces during heat treatment as the concentration of dairy products inc reases is due to a competition between the two main mechanisms of depo sit formation, namely protein aggregation and salt crystallization. Th e formation of the deposit is dominated by protein aggregation up to t he stage at which the maximum occurs. As the whey concentration is inc reased higher than 25% in total solids there comes a stage at which th e solubility of the milk salts is massively exceeded and from then on salt crystallization plays an increasing part in the formation of the deposit, which up to then has consisted of proteins. A number of exper iments with protein solutions and solutions of salts and lactose, desi gned to examine the influence oi the composition of the product on dep osit formation, showed that there was a linear relationship between th e concentration of the product and the mass of deposit formed without any reverse. At higher concentrations, protein/lactose solutions with a reduced salt content formed a high porous, spongy deposit, wherein l actose containing fluid was increasingly included. Increasing the salt content of salt depleted protein solutions selectively by the additio n of calcium phosphate, decreased the mass of the deposits and, at the same time, made them stronger and more compact.