Phase transitions of maize starches with different amylose contents in glycerol-water systems

The phase transitions of maize starches with different amylose contents (3.4-82.9%) were systematically studied by DSC with stainless steel high-pressure pan under temperature scanning from 30 up to 200 °C. The results show that the distinct pattern of multiphase transitions of maize starch was not only determined by the amylose content, but also by glycerol-water mixture content (50 and 70%) and glycerol/water ratio (0/100, 10/90, 50/50, 90/10, and 100/0). Moreover, a big exothermic transition could be observed within the range of about 95-135 °C for all four maize starches mixed with pure glycerol, which was mainly due to the glycerol-starch -OH binding reaction and was greatly affected by the granular structure and molecular characteristics of maize starch (starch type). It has been shown that high temperature, adequacy of glycerol, and long storage time all favour the reaction of glycerol with starch molecules.