The effects of field pre-harvest sprouting on the morphological structure and physicochemical properties of rice (Oryza sativa L.) starch

•Grain processing and appearance quality of polished rice had a degradation under field PHS condition.•Field PHS can lead to a slightly improvement in starch gelatinization properties.•Protein content of polished rice significantly decreased under field PHS. This study investigates the effects of field pre-harvest sprouting (PHS) on the morphological structure and physicochemical properties of starches from four rice varieties during the rice harvesting period. The results of the study showed that PHS significantly affected the grain characteristics, starch structure, and physicochemical properties of the four rice varieties. Moreover, PHS led to a significant decrease in the grain processing quality and protein content of the four varieties, pitting and unevenness on the surface of the starch granules, and smaller starch granules. In addition, PHS led to starches with lower amylose content, which resulted in a higher swelling power, solubility, and relative crystallinity. Higher gelatinization enthalpy and lower gelatinization temperature were also observed under PHS conditions. The results indicated that PHS can lead to degradation in grain processing and appearance quality, but it can also lead to some improvements in the gelatinization properties of starch.