| The stable whey protein isolate (WPI)-butter emulsion system has a good application prospect in dairy product processing and dairy product nutrition delivery system. WPI with different mass concentrations (2%, 4%, 6%, 8%) were subjected to different heat treatments (unheated, 80 ℃, 90 ℃), then butter was added and ultrasonic treatment was performed to prepare emulsions. The particle size, flocculation index（FI）, emulsifying activity (EA), emulsion stability (ES), physical stability, particle size changes and fat floating of the emulsion during storage were analyzed. The results showed that as the heat treatment temperature increasing, the average particle size of the emulsion increased. The average particle size of the unheated emulsion was less than 1 μm, After heat treatment, the particle size of the emulsion with different protein mass concentration increased at different degrees. After heat treatment, the EA and ES of the WPI emulsion improved. As the protein mass concentration increased, the physical stability of emulsion increased, in which the stability indexes of the samples with protein mass concentration 6% and 8% heated at 90 ℃ were all less than 0.6, and the stability was the best. Under the same protein mass concentration, the higher the heat treatment temperature, the stronger the proteins stabilizing effect on the emulsion. The fat floating of the emulsion during storage was significantly related to the heat treatment temperature and protein mass concentration. Higher protein mass concentration and heat treatment temperature could improve the fat floating in the emulsion system. The study showed that controlling the protein mass concentration and WPI heat treatment temperature could effectively improve the emulsification characteristics and stability of the WPI-butter emulsion system. |
