Effect of glass transition on the formation of drying cracks in the component parts of maize kernels.

Glass transition can cause the formation of drying cracks in different component of maize (Zea mays) at different drying stages, but the influence of the mechanism is unknown. This work aimed to study the effect of glass transition on crack formation in different components. It was found that the differences in moisture content, temperature distribution, and glass transition temperature of the components can cause different glass transition processes in the components at different drying stages with 55 °C hot air. The temperatures of the pericarp and germ were found to be higher and lower, respectively, than corresponding the glass transition temperature, so remained in a single state, resulting in the absence of cracks. Cracks generated in the hard endosperm and then extended to soft endosperm, which was consistent with the glass transition of the endosperm. At the preheating stage, the endosperm had no cracks. After the main drying stage, the stress crack index (SCI) of hard and soft endosperm were 160.0 and 65.3, respectively. After the cooling stage, the SCI of the hard and soft endosperm increased to 402.3 and 163.3, respectively. Cracks were mainly formed during the main drying and cooling stages, and more cracks formed in the cooling stage. The cracking in the components at different drying stages could be well explained by glass transition. • Crack formation in the components depended on the form and process of glass transition. • Pericarp and germ were in a single state resulted in the absence of cracks. • Occurrence and propagation of cracks in the endosperm consistent with its glass transition. • Glass transition could explain the crack degree in the components at different drying stages. [ABSTRACT FROM AUTHOR]