Nitrogen fertilization levels influence the physicochemical properties of floury rice varieties

Background and objectives This study was conducted to determine the effect of nitrogen fertilization level during cultivation on physicochemical properties of two floury rice varieties (Shingil and Garumi 2) with different endosperm types under dry‐milling process. Findings In both varieties, the protein content was increased in proportion to the level of nitrogen fertilization, while the amylose content exhibited a slight decrease in the highest nitrogen fertilization level. Damaged starch and digestible starch fractions were decreased with increasing nitrogen fertilization for both varieties, maybe due to the reduction in total starch relative to the protein content. Nevertheless, the level of damaged starch increased in Shingil under the highest nitrogen fertilization of 270 kg/ha, suggesting that nitrogen fertilization level can affect the physicochemical characteristics of starch particles during dry milling. The proportion of short amylopectin chains (DP6‐12) decreased with increasing nitrogen fertilization. The difference was more prominent in Shingil than the other variety Garumi 2, indicating that Shingil could experience a greater increase in hardening and a faster retrogradation by increased nitrogen fertilization level than Garumi 2. Conclusions Nitrogen fertilization levels during rice growth affected the starch and protein contents in the endosperm, the chain length of amylopectin, which should, in turn, contribute to the processing properties of floury rice varieties. Significance and novelty This study will help develop fertilization strategies for the novel floury rice varieties and consequently provide helpful information to the rice‐processing food industry.