Effect of konjac glucomannan and soy soluble polysaccharides on the rheological, microstructural and syneretic properties of rennet gels

Abstract

This study investigated the rheological, microstructural and syneretic properties of rennet gels as influenced by the addition of soy soluble polysaccharides (2.5 g/kg, 5 g/kg) or konjac glucomannan (0.2 g/kg, 0.4 g/kg) to skim milk. The addition of all polysaccharides enhanced rennet coagulation properties, by reducing rennet coagulation time (RCT) and increasing development of gel firmness. There were also interactive effects between polysaccharide concentration and coagulation pH on parameters such as RCT, showing that the dynamics of gelation of such systems can be modulated by changing polysaccharide concentration and pH. Rennet gels containing 0.4 g/kg konjac glucomannan had significantly higher levels of syneresis (p < 0.05) than the other gels, which was linked to low yield stress and strain and a more open and porous microstructure. Quantitative analysis of 3-D confocal laser scanning microscopy image stacks showed that rennet gels containing konjac glucomannan had a significantly larger (p < 0.05) pore size than the other rennet gels. The ability of these polysaccharides to change the structure of rennet gels and their ensuing syneretic processes may provide a platform for development of novel cheese textures appealing to international consumers who may not be traditional cheese consumers.