Morphological, Physical, and Chemical Properties of Grain and Flour from Chalky Rice Mutants

Abstract

Morphological, physical, and chemical properties of grain and flour of 20 chalky rice mutants were compared with those of a translucent parental cultivar, Koshihikari. Compound starch granules were loosely packed and single starch granules were observed in chalky parts of mutant endosperm. Chalky mutant lines were classified into milky‐white and white‐core lines based on the degree of endosperm chalkiness. Physical and chemical characteristics also suggest a division of chalky mutant lines into two groups, consistent with the classification made based on morphological characteristics. Milky‐white mutant lines showed significantly lower grain weight, decreased starch content, and lower grain hardness than white‐core mutants and Koshihikari. Rice flour prepared from milky‐white mutants by dry milling showed less starch damage and finer mean particle size than white‐core mutants and the parent. These results indicated that a loosely packed structure in chalky endosperm was responsible for fragile grain and that it yielded fine flour with lower damaged starch contents. Decreased starch contents of chalky mutant lines correlated to lower RVA viscosities. Milky‐white mutant lines were expected to be useful to produce fine flour, which undergoes less starch damage during dry milling processing.

Effects of Nitrogen Rate and Harvest Moisture Content on Physicochemical Properties and Milling Yields of Rice

“…Chalkiness is linked to the process of starch accumulation in the rice endosperm (Kim et al 2000;Lisle et al 2000;Patindol and Wang 2003;Ashida et al 2009;Patindol et al 2014). In addition to the previously mentioned marketing issues, chalkiness leads to increased breakage during milling, thus reducing HRY (Counce et al 2005;Lanning et al 2011).…”

Effects of Preharvest Nighttime Air Temperatures on Whiteness of Head Rice

“…However, the colorimetric analysis of head rice measured with and without chalky kernels revealed that L* values did not change significantly with the exclusion of chalky kernels. Rather, the authors hypothesize that the effect of NTAT on kernel formation, that is, loose packing of starch granules (Ashida et al 2009), may be manifested not only in the obvious visibly chalky portions of kernels but also in the remaining nonchalky portions of kernels, thus influencing the translucency and whiteness of the kernels. Whiteness values trended slightly lower with the exclusion of chalky kernels, but the differences were not statistically significant.…”

PaddyCheck—An Instrument for Rice Quality Determination

“…The operator pours the kernels manually into the instrument and there are a range of discs with different cavity sizes for different sorts of rice. The quality parameter chalkiness, which is also called white belly, is a measurement of the opacity of the endosperm, which can reduce the hardness of the kernels [15,16]. Chalkiness can occupy >50% of the kernel area and can be caused by both varietal and environmental factors, such as the packing degree and morphology of the starch granules, high temperature, insufficient nutrition supply and the durability of the ripening [17][18][19][20].…”