Effect of waxy rice kernel structure on hydration behavior during the production of Zongzi

Abstract

The hydration behavior of waxy rice, specifically water absorption and diffusion during soaking and cooking, plays an important role in determining the quality of Zongzi. However, the relationship between this hydration behavior and the kernel structure has not been fully clarified. In this study, high-resolution X-ray microtomography (XMT) and confocal laser scanning microscopy (CLSM) were used to analyze the kernel structure and density of three representative types of waxy rice, with particular attention to how structural features influence the hydration process. Results showed that Type III waxy rice, known for producing Zongzi of superior quality, exhibited uniformly small starch granules and a moderately distributed protein layer. This structural characteristic contributed to lower density and more homogeneous porosity, which was associated with improved moisture distribution and hydration efficiency. Mechanistic analysis suggested that the morphology and distribution of starch and protein may influence kernel density and internal porosity, thereby affecting water absorption and diffusion behaviors. These findings reveal the structural causes of quality differences in Zongzi among different types of waxy rice, providing a theoretical basis for the selection of waxy rice as a raw material for Zongzi and the setting of production parameters.