The development of forage-grain ratoon rice (RR) pattern could ensure food security and promote silage production. Herein three indica rice varieties were used to investigate the influence of different forage clipping stages (heading, milk-ripe, wax-ripe, and full-ripe) on starch molecular structures and RR properties. The apparent amylose contents (AAC) of starches increased, but pasting viscosities, gelatinization temperatures and starch sizes decreased with the postponement of clipping stages due to the retardation of endosperm development. The starches showed A-type crystalline structure with increased in vitro digestibility; however relative crystallinity decreased by 13.45 % to 23.89 %. The short fa (DP 6-12) chains of amylopectin increased while long fb3 (DP ≥ 37) chains decreased (p < 0.05). The proportions of amylose chains with DP 100-2000 increased but those with DP 2000-20,000 decreased. Rice grain strength was positively correlated with fb3 chains while negatively correlated with fa chain. The hardness of cooked RR was positively correlated with AAC while negatively correlated with fb2 (DP 25-36). RR clipping at milk-ripe stage had the highest grain strength and moderate texture properties. The elucidation of structure-property relationships is helpful for RR utilization and development of suitable cultivation conditions for RR production.
Keywords: Clipping stage; Physicochemical property; Ratoon rice; Starch structure; Texture.
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