Factors influencing the retrogradation of two rice starches in low-molecular-weight saccharide solutions

The complicated effects of added sugars and maltodextrins (5-20%) on the retrogradation of starch gels were investigated using differential scanning calorimetry and dynamic rheometry. One indica (Kaoshiung Sen 7, KSS7) and one japonica (Tainung 67, TNu67) rice starch with well-defined physico-chemical properties were used to clarify changes in re-crystallisation behaviour of starch components due to the addition of saccharides at different concentrations. The sugars showed marked suppression effects on the short-term retrogradation of KSS7, and both short- and long-term retrogradation of TNu67 gels. The suppressing effect of the sugars depended not only on sugar concentration, but also on the starch variety and the aging period. Maltodextrins with high average-degree of polymerisation exhibited a high retrogradation-promoting capability, especially in TNu67 gels on the first day. The addition of sugars and maltodextrins at 5-20% generally had little effect on the correlation between the storage modulus and the retrogradation enthalpy of starch gels. (C) 1998 Academic Press.