Tribo-rheology and kinetics of soymilk gelation with different types of milk proteins

Abstract

The effect of different types of milk proteins (Whey protein isolate [WPI], milk protein concentrate [MPC] and sodium caseinate [NaCas]) on gelation behavior of soymilk was investigated. WPI caused the most positive effect on the gelation of soymilk by reducing gelation time, increasing gel strength, and enhancing water-holding capacity. The gelation rate at different stages suggested that WPI enhanced soymilk gelation mainly during the acidification, while MPC and NaCas enhanced the gelation during cooling. Introducing low proportion of milk proteins effectively reduced the average particle size of the gels, consequently reducing the friction at mixed regime, while high proportions of milk proteins resulted in boundary regime and high friction during mixed regime, due to the high gel firmness. No dramatic change on the "secondary structure" of the gel was caused by introducing MPC or NaCas; while more strands and network were formed in the "primary structure," especially with NaCas.

Keywords: Microstructure; Milk proteins; Rheology; Soymilk gelation; Tribology.