Effect of polymer ratio and calcium concentration on gelation properties of gellan/gelatin mixed gels

Gelation properties of gellan/gelatin mixed solutions were studied using dy namic viscoelastic testing at eight different ratios of gellan (1.6-0.2% w/ v) to gelatin (0-1.4% w/v) and seven different calcium levels (0-30 mM). Th e gelation temperature and gelation rate of the mixed gels were significant ly affected by the ratio of gellan to gelatin as well as concentration of c alcium. Addition of calcium at low levels resulted in an increase in gelati on temperature and gelation rate compared to gels with no added calcium. Fu rther increases in calcium increased the gelation temperature, but caused a decrease in gelation rate of the mixed gels. In addition, the presence of gelatin generally had a negative influence on gelation rate, especially at high proportions and when the solution had a high gelling temperature, prob ably by physically hindering the growth and development of gellan crosslink s. It appeared that in the presence of calcium, gellan formed the continuou s gel matrix, with gelatin present as a discontinuous phase. Gellan/gelatin mixtures can form gels over a wide temperature range by varying the ratio of the two polymers as well as the calcium concentration. (C) 2001 Elsevier Science Ltd. All rights reserved.