Whey proteins solubility as temperature and Ph function

Abstract

There is a straight analogy between fouling and protein unfolding when milk derived fluids are processed in equipments of heat exchangers, where whey proteins are unfolded in an irreversible way, exposing hidrophobic groups, and they become insoluble and form aggregates. An integrated study was conducted on the effects of temperature and pH on the solubility of whey proteins. The solubility was determined experimentally in the temperature range of 50-80°C, for pH values of 4.0 and 6.8. These temperature values are used in several processes employed in milk processing, such as pasteurization, sterilization e evaporation. This work showed the temperature and pH conditions that result in high values of protein solubility and allowed the solubility curves of whey proteins in cow milk. The product constituted of a whey protein isolate obtained from cow milk (ALACEN™ 895), adquired by New Zeland Milk Products Brazil Ltd. The results showed that, both the temperature and pH influenced in the protein solubility, and these properties have great interaction. Besides, for whey proteins, the solubility values were minimum at the pH value of 4.0, which is near the isoeletric point of whey proteins, for all temperature values. It was also observed that at pH 4.0, the solubility decreased as the temperature increased, which indicated that the protein denaturation occurred, and this behavior was also moticed in the neutrality (pH=6.8).