The effect of heat treatment on the physical and chemical properties of dairy emulsions
Dairy emulsions were processed using high temperature short time (HTST), high temperature long time (HTLT) and ultra high temperature (UHT) regimes, and the effect of heating on their properties was explored. Although heating is an important unit operation in dairy processing, very little work has been carried out on emulsion characterization using heating regimes comparable to those used in industrial manufacturing. Studies were performed on two different systems: whey protein emulsions and homogenized milk. As whey protein stabilized emulsions were subjected to more extensive heat processing (HTLT and UHT), there was an increase in protein-protein interactions in both the unadsorbed phase and at the oil droplet interface. Differences were also observed in whey protein emulsions depending if the heating stage was placed before or after homogenization. In the case of homogenized milk, more adverse effects were also found when milk was heated at longer and higher temperature treatments. In addition, the milk proteins were more easily displaced from the interface if milk was heated before homogenization. The results from this research will help in better understanding the stability and processing behaviour of heated dairy emulsions.