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Multiple Measurements of Physical Properties of Individual Cooked Rice Grains with a Single Apparatus

¹National Food Research Institute, Ministry of Agriculture, Forestry and Fisheries of Japan. 2-1-2, Kannondai, Tsukuba Science City, Ibaraki, 305-8642 Japan. ²Corresponding author. E-mail: okadome@nfri.affrc.go.jp Phone: 81-298-38-8045. Fax: 81-298-38-7996.

Multiple measurements of physical properties of cooked rice grains were applied to 55 rice samples with waxy to high amylose contents using a single apparatus (Tensipresser). The multiple measurements consisted of low, high, and continuous progressive compression tests (LC, HC, CPC). The overall hardness (H₂) determined by the HC test, and the surface hardness (H₁) determined by the LC test, were used as indices to classify the samples into the several groups corresponding to amylose content. The surface hardness was more suitable than the overall hardness for differentiating the effect of protein contents. The difference of stickiness among the cooked rice samples could be detected by the surface adhesion distance (L₃) using the LC test. The ratio of elastic limit length (RELL), estimated by the back pressure curve on the CPC test, increased with amylose content. These three tests were meaningful in characterizing the physical properties of cooked rice samples with waxy to high amylose contents.