A differential scanning calorimetric (DSC) study on the effects of annealing and sugars-emulsifiers on gelatinization of sago starch (Metroxylon sagu)

This study investigated the effects of annealing, at different temperatures (45-70C), times (0-24 h) and water:starch ratios (0.6/1-4/1), on the DSC t hermal properties profiles associated with gelatinization temperatures of s age starch-water mixtures. The effects of sugars-emulsifiers and of starch mixtures and their interactions were also investigated. DSC data showed an increased gelatinization temperature and enthalpy and a narrower gelatiniza tion temperature range (T-m-T-o) after annealing of sago starch; the extent of these changes was inversely proportional to the degree of crystallinity of the native starch. For sage starch, the G transition occurring at about 66-69C and the M-1 transition occurring at about 75C in excess water becam e broader and shifted to higher temperatures as the water content was decre ased. The effects on the gelatinization temperature and Delta H, of the add ition of sugars-emulsifiers to the starch-water mixture, were observed by c omparison with the starch-water results. Sucrose raised the gelatinization temperature by about 6-7C more than did glucose, for sage starch. Emulsifie rs (sucrose ester and polysorbate-60), in the presence of sucrose or glucos e, did not affect the gelatinization temperature.