Effects of elevated nitrogen fertilizer on the multi-level structure and thermal properties of rice starch granules and their relationship with chalkiness traits

Changchun Guo, Riqu Wuza, Ziling Tao, Xiaojuan Yuan, Yinghan Luo, Feijie Li, Guotao Yang, Zongkui Chen, Zhiyuan Yang, Yongjian Sun, Jun Ma

Journal of the Science of Food and Agriculture 2023 July 28（IF=4.1）

https://doi.org/10.1002/jsfa.12886

Abstract

BACKGROUND: Chalkiness of rice reduces the market value of rice and affects consumers' acceptance. Research on the mechanism of chalkiness formation primarily focuses on the activities of key enzymes of carbon metabolism and starch accumulation. However, the relationship between the formation of chalkiness induced by N fertilizer and rice starch's multi-level structure and thermal properties still needs to be fully elucidated.

RESULTS: In this study, the rates of chalky grains and degree of chalkiness decreased with the increase of N fertilizer dosage. This was attributed to an enlarged proportion of short chains, ordered structure carbon chain, degree of crystallinity and ΔHg in protein, small starch granules and branched starches, and a decreased proportion of amylose, large starch granules and weighted average diameter of starch granule surface area and volume. Application of N fertilizer promoted higher short-branched chain amylopectin to develop a more ordered carbohydrate structure and crystalline lamella. These effects enhanced the normal development and compactness of starch granules in grains, and improved their arrangement morphology, thereby reducing the chalkiness in rice.

CONCLUSION: Thereby, these changes in starch multi-level structure and protein support the improvement of starch physicochemical characteristics and enhance the fullness, crystallinity and compactness of starch granules, while synergistically increasing the regularity and homogeneity of starch granules and thus optimizing the stacking pattern of starch granules, leading to a reduction in rice chalkiness under nitrogen fertilization and thus improving the appearance of rice. This article is protected by copyright. All rights reserved.