Hiroshi Okadome

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

ABSTRACT 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.

Rheological Properties and Lipid Oxidation of Rice Decontaminated with Low-Energy Electrons

Microbial load and quality of rice grains which were exposed to electrons at different acceleration voltages of 170 to 200 kV were examined to evaluate the efficacy of decontaminating rice with low-energy electrons. Electrons at any acceleration voltage between 170 and 200 kV reduced microbial loads of brown rice grains to levels lower than 10 colony-forming units (CFU)/g. Higher acceleration voltages resulted in a lower viscosity and a higher thiobarbituric acid value (TBA). Milling at a yield of 90 or 88% after electron treatment made the viscosity and TBA of rice treated with electrons at 170 kV almost the same as untreated rice. Low and high compression analyses of rice grains which were exposed to electrons at 170 to 180 kV and milled at a yield of 90% followed by cooking showed almost the same hardness and stickiness as untreated grains which were milled at 90%. The results indicate that milling at a yield of 90% or lower removes the portion of rice exposed to electrons at 170 kV and that treatment of brown rice with low-energy electrons enables the preparation of milled rice with extremely low levels of microbial load and little quality deterioration.

Conditions of viscosity measurement for detecting irradiated peppers

Abstract Viscosity of gelatinized suspensions of black and white peppers decreased depending upon dose. The viscosity was influenced by gelatinization and viscosity measurement conditions. The difference between unirradiated pepper and an irradiated one was larger at a higher pH and temperature for gelatinization. A viscosity parameter normalized with the starch content of pepper sample and the viscosity of a 5% suspension of corn starch could get rid of the influence of the conditions for viscosity measurement such as a type of viscometer, shear rate and temperature.