Abstract
The sub- T g thermal properties of aged amorphous waxy starch, β-limit dextrin, and amylopectin triacetate at low moisture contents were studied by differential scanning calorimetry (DSC). When T g was above 50°C (∼5–14% moisture), a 50°C endothermic peak was observed in waxy starch and β-limit dextrin samples. The ΔH of the 50°C peak was proportional to the moisture content. At a similar moisture content the ΔH of β-limit dextrin was greater than that of waxy starch. No 50°C peak was observed in the amylopectin triacetate samples at the moisture contents studied (∼0·5-5% moisture). All amylopectin triacetate samples showed an endothermic overshoot associated with the glass transition. It is suggested that water-hydroxyl group interactions may be required for the formation of the sub- T g peak. The 50°C endotherm is a separate event different from the aging peak associated with the glass transition seen in many polymers.
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