EFFECT OF POLYHYDROXY COMPOUNDS ON STRUCTURE FORMATION IN WAXY MAIZE STARCH GELS - A CALORIMETRIC STUDY

The effects of polyhydroxy compounds (PHCs) on structure formation in ageing waxy maize starch gels were investigated by measuring the retrogradation endotherm (Delta H) using calorimetry. Changes in retrogradation kinetics observed by addition of PHCs at a weight ratio of starch:PHC:water of 1:0 5:1.5 were solute specific. In the homologous series of glucose oligomers, maltotriose exhibited the largest inhibitory effect, while maltooctaose promoted retrogradation. Among various pentose and hexose sugars, ribose and talose, respectively, were the most effective in retarding retrogradation. Fructose led to increased rates of chain ordering, particularly at high concentrations. The results were correlated with literature data of several physicochemical properties of PHCs in solution. Strong linear relationships were shown between the effect of sugars on retrogradation endotherm and the hydration characteristics of these solutes. It was further suggested that compatibility of sugar with the water structure, as governed by the stereochemistry of the main sugar conformers in solution, is an important determinant of amylopectin stability in the composite gel matrix; i.e. PHCs which disturb very little the hydrogen-bonded network of water are also effective in inhibiting retrogradation.