Microstructure, Water Migration and Texture of Thai Chalky Rice Varieties

Chalk is an inferior characteristic of rice because it leads to the poor milling quality. In addition, chalky rice is generally considered to have poor cooking and eating qualities. However, the data on the poor cooking and eating qualities of chalky rice is limited, especially in high amylose Thai chalky rice varieties. Therefore, this work aimed to compare the microstructure, water migration during cooking, texture and sensorial qualities of four Thai chalky rice varieties, Prachin Buri2 (PB2), Khao Bahn Nah432 (KBN432), Ayutthaya1 (AY1), and Plai Ngahm Prachin Buri (PNPB), with the translucent Thai rice variety, Phitsanuplok2 (PSL2). The loosely packed cell structure in all chalky rice varieties was observed under scanning electron microscope. KBN 432 had the highest degree of chalkiness. Water migrated in the KBN432 with the fastest speed. All cooked chalky rice had lower hardness than the translucent rice, except AY1. Softness scores of chalky rice samples were higher than translucent rice. However, there was no difference in overall acceptability between chalky rice and translucent rice. Therefore, chalky rice varieties studied in this work may be used for consumption with the same quality to the translucent rice variety.