Effect of the addition of different sodium alginates on viscoelastic, structural features and hydrolysis kinetics of corn starch gels

Corn starch gels (1:4 w:w) were made with the addition (up to 2% w/w starch basis) of sodium alginates of different average molecular sizes and nature. Rheology of the starchy gels were characterized to evaluate their viscoelasticity. Gels were subjected to in vitro digestion to estimate the effect of alginates addition on glycemic response. Tested alginates significantly decreased the value of the elastic modulus of gels. The coordination number obtained from complex modulus indicated that in general, less compact structures were obtained in the presence of alginates. These results were confirmed by scanning electron micrographs, where significant differences in the structure of alginate-corn starch gels were observed, but molecular size of alginates was not critical. Hydrolysis rate decreased with the presence of alginates in corn starch gels by interactions of alginates with leached amylose. At high alginate content, slower hydrolysis rates were determined when the most hygroscopic alginates were added.