Effect of different hydrocolloids on tribological and rheological behaviors of soymilk gels

Abstract

Different types of hydrocolloids (gelatin [0.25, 0.5 and 1%], polysaccharides [ionic and neutral, 0.01, 0.05 and 0.1%] [w/w]) were applied in acid soymilk gels to investigate their effectiveness in improving the physical properties of gels. The function was found to vary considerably with the hydrocolloid types. Gelatin was found to have the best compatibility with soy proteins. The dynamic oscillatory rheology measurement indicated that no severe interruption to the soymilk gelation was caused and the microstructure of the final gels was not changed much even at 1% concentration. In the meantime, gelatin effectively enhanced the water holding capacity of the gels; gelatin (≥0.5%) dramatically decreased the particle size (D4, 3), increased the uniformity of the gel particles, and effectively improved the lubrication property of the gel. Neutral gums (locust bean gum and guar gum) caused severe interruption of soy protein gelation, showing negligible gelation during acidification and large amount of water separation at 0.1% concentration. Better compatibility with soy proteins was observed with ionic gums (ι-carrageenan and xanthan) than neutral ones, especially ι-carrageenan, showing enhanced yield stress, viscosity, storage modulus, gel firmness and water holding capacity at 0.05% concentration. Low concentration of any type of polysaccharide (0.01%) caused reduction of D4, 3 and decrease of friction coefficient in the mixed regime. The results suggested that gel particle characteristics, instead of viscosity, dominated the gel lubrication in this system. Three types of hydrocolloids showed dramatically different effect on the microstructure of the gels, which accorded well with the physical properties.