Glass transitions of barley starch and protein in the endosperm and isolated from

Abstract

When studying the glass-to-rubber transition inside natural materials, it is important to take into account not only the moisture content but also the moisture distribution over the components in the material. We measured the Tg of protein and starch isolated from barley at different moisture contents using differential scanning calorimetry (DSC) (heating rate 10°C/min) and by thermo mechanical compression tests (TMCT) (heating rate 2°C/min). The measurement of the Tg of partially crystalline materials, such as barley starch, is more difficult using TMCT because the mechanical effect of expansion of these materials is smaller. For both measurement sets the glass transition lines were modeled using the Gordon–Taylor equation. The lines were adapted for the differences in moisture content over the endosperm by using the sorption isotherms of isolated barley starch and protein and whole barley endosperm. The glass transition lines measured by TMCT were closer together than the ones measured by DSC.