Improvement of tribo-rheological properties of acid soymilk gels by reinforcement of 7S or 11S proteins

Abstract The effect of soy protein components on acid soymilk gels was investigated by replacing 10%, 20% or 40% protein from soymilk powder with equivalent amount of protein from 7S or 11S, according to three stages (acidification, cooling and annealing) by dynamic oscillatory rheology. The final gels after cold storage were evaluated in terms of rheology, particle size, texture, water holding capacity (WHC), microstructure and tribology. Both 7S and 11S could effectively and almost equivalently improve the gel strength at incorporation ratio ≥20%, seen from the rheological and texture results, and enhance the WHC. Particle size (D[4,3]) of the gel was also increased by incorporation of high ratio of 7S or 11S. On the other hand, 20% and 40% 11S reduced the gelation time significantly during acidification and 40% 11S induced coarser microstructure than control; while 7S showed no significant effect on gelation time and 40% 7S incorporated gel showed well organized gel structure. Introducing 7S or 11S as low as 10% could effectively improve the gel lubrication; while high concentration (40%) could induce the opposite effect. Also, 40% 7S postponed the transition from mixed regime to hydrodynamic regime; while 40% 11S brought it forward. Overall, 20% could be a reasonable ratio of 7S or 11S incorporation to improve the gel properties.