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When brown rice is preserved for a long period of time, a stale flavor (komai-shu) develops as a result of lipid oxidation by enzymes. In order to inactivate the enzymes, brown rice was treated with superheated steam. Superheated steam treatment for about 1 min, at all temperatures, caused a decrease in the enzymatic activity related lipid oxidation. On the other hand, the degree of starch damage did not increase during superheated steam treatment below 150℃. These results show that superheated steam treatment at a low temperature and for a short time is enough to inactivate the enzyme in brown rice, and does not influence starch quality. It was expected that enzyme inactivation by superheated steam treatment would be effective in suppressing the generation of stale flavor during long preservation periods.

A new super-hard rice cultivar, ‘Chikushi-kona 85’, which was derived from a cross between ‘Fukei 2032’ and ‘EM129’, was developed via bulk method breeding. ‘Chikushi-kona 85’ showed a higher content of resistant starch than the normal non-glutinous rice cultivar, ‘Nishihomare’, and a higher grain yield than the first super-hard rice cultivar, ‘EM10’. The amylopectin chain length of ‘Chikushi-kona 85’ and its progenitor line ‘EM129’ was longer than that of ‘Nishihomare’, and was similar to that of ‘EM10’. This suggests that the starch property of ‘Chikushi-kona 85’ was inherited from ‘EM129’, which is a mutant line deficient in a starch branching enzyme similar to ‘EM10’. Genetic analysis of ‘Chikushi-kona 85’ crossed with ‘Nishihomare’ also showed that the starch property of ‘Chikushi-kona 85’ was regulated by a single recessive gene. Consumption of processed cookies made from ‘Chikushi-kona 85’ flour showed a distinctive effect in controlling blood sugar levels in comparison to the normal non-glutinous rice cultivar ‘Hinohikari’. These results show that ‘Chikushi-kona 85’ is a novel genetic source to develop new products made of rice, which could reduce calorie intake and contribute to additional health benefits.

Thus, ADM seems to also be suitable for making comparisons among processed rice products which undergo cooking processes and also reflects the actual digestibility in the human body. Based on the results of comparison testing among various rice cultivars, RS content was shown to decrease after cooking processes, although it did not di#er among milled rice samples of di#erent cultivars as measured by the RS-kit method and ADM. The RS of processed rice products prepared from high amylose rice remained higher compared with that from low amylose rice. These findings indicate that RS content can be adjusted through conditions of heating and cooking, because RS di#ers with di#erent processing methods.

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