The effect of starch gelatinization and solute concentrations onTg? of starch model system

Abstract

The effect of starch gelatinization on glass transitions in a starch/water model system and how the concentrations of added solutes (sucrose and sodium chloride) affect the glass transition temperatures of the gelatinized starch solution was investigated. The starch suspension samples were heat treated in a Differential Scanning Calorimeter (DSC) under different time and temperature regimes to achieve different degrees of gelatinization. The gelatinization characteristics (onset, peak and end temperatures and enthalpy) and the glass transition values of a potato starch were determined using the DSC. The results showed that the starch concentrations had no effect on gelatinization characteristics and the Tg′ of the gelatinized potato starch but had clearly increased their ΔCp in the Tg′ region. Annealing at a temperature slightly below the Tg′ of −5 °C, led to maximal freeze-concentration in the total/partial gelatinized starch and a higher Tg′ value at about −3 °C was obtained. The Tg′ values of the totally gelatinized starch samples were slightly lower than those of partially gelatinized samples. The Tg′ of the gelatinized starch decreased with increasing concentrations of sucrose or sodium chloride. Sodium chloride had a stronger depressing effect on Tg′ than sucrose. © 2000 Society of Chemical Industry