Determination of thermal transitions in foods by stepwise differential calorimetry

摘要

A DSC was operated in a discontinuous fashion to enhance thermogram resolution for transitions in foods. Following a 1 deg C stepwise increase in temperature, the heat flow was measured over 3 to 4 minutes. Additional 1 deg C steps were subsequently applied until the temperature range of interest was accomplished. Thermal transitions such as melting occurred within a narrower temperature range than observed with conventional scanning. For example, melting of both ice and indium occurred within a 1 deg C step. Melting of frozen solutions was also measured, and from which a phase diagram was derived. In addition, gelatinization of starch and glass transitions in carbohydrate systems were determined. Stepwise calorimetry allowed finer resolution of systems with multiple transitions. In addition, transitions were detected that were not easily seen with continuous scanning calorimetry. For example, glass transitions in frozen foods were difficult to detect by continuous scanning but were seen as separate events using stepwise calorimetry.