Effects of heat treatment of cream on the physical-chemical properties of model oil-in-buttermilk emulsions

摘要

The effects of heat treatment of cream on the physical-chemical properties of model oil-in-buttermilk emulsions were studied. Raw cream (35% milk fat, no heat treatment) and pre-heated cream (60, 75 or 90 ℃ for 15 s) were churned into butter or buttermilk (BM-R, BM-60, BM-75, and BM-90). Emulsions were prepared with the resulting buttermilks and 10% sunflower oil. The physical-chemical analyses performed on the different buttermilks showed a significant difference for BM-90, which had a lower content of native whey proteins. There were no significant differences in the fat, protein or phospholipid content, particle size distribution or interfacial tension against sunflower oil. Surprisingly, the emulsion with BM-90 was significantly more stable, and its particle size distribution showed smaller droplets compared with emulsions with BM-R, BM-60, and BM-75. Our observation suggests that the denatur-ation of the whey proteins before homogenization strongly influences the stability of the resulting oil-in-buttermilk emulsions.