Tribo-rheological properties of acid milk gels with different types of gelatin: Effect of concentration

摘要

We investigated the effect of low concentrations(0.1 to 1%, wt/wt) of gelatin (types A and B) on theproperties of acid milk gels in terms of rheology, tribology,texture, and water-holding capacity to betterunderstand the role of gelatin in yogurt. The 2 types ofgelatin showed similar effects on the properties of milkgels, with some minor differences, such as lubricationbehavior at low concentrations. During acidification,gelatin at ≤0.4% caused an increase in the gel strength,and at higher concentrations it showed a negative effect.However, during cooling and annealing, we observed apositive effect on gel strength with 0.8 and 1% gelatin.Gelling and melting occurred at 0.8 and 1% concentrationsof both types of gelatin. The addition of gelatintended to decrease the storage modulus of milk gelsand increase the apparent viscosity, pseudoplasticity,consistency, and yield stress. The firmness of the gelswas decreased by gelatin at medium concentrations,but increased at high concentrations. Gelatin significantlyenhanced the water-holding capacity of the gels;we observed no serum at concentrations ≥0.4%. Withthe addition of gelatin at concentrations ≥0.4%, theparticle size of gels was greatly reduced, and their lubricationproperties were significantly improved. Thisstudy showed that 0.4% was an effective concentrationin acid milk gel; above this concentration, the propertiesof the milk gels were greatly changed. Tribologyprovided important information for understanding therole of gelatin in milk gels.