Effects of Foliar Application of Iron Chlorine e6 on the Starch Physicochemical Properties and In Vitro Digestibility...

Foliar application of iron chlorine e6 (ICE6) acts as an important agronomic practice to regulate grain quality of waxy maize. This study examined the effects of foliar application of ICe6 at six rates, 0 (T1), 22.5 (T2), 45 (T3), 67.5 (T4), 90 (T5) and 180 (T6) g ha^-1 on the starch physicochemical properties and in vitro digestibility of waxy maize. Relative to T1, T5 and T6 significantly elevated total starch and amylopectin contents by 8.29%-8.85% and 8.39%-8.91%, respectively. Meanwhile, T4 possessed the highest starch volume-weighted mean granule diameter. For starch granule size distribution, the proportions of medium granules increased and large granules decreased. Beyond regulating starch accumulation, ICE6 also improved starch granule morphology and surface structure, reduced relative crystallinity and gelatinization enthalpy, and enhanced pasting viscosity. Meanwhile, ICE6 decreased the content of rapidly digestible starch (RDS), increased slowly digestible starch (SDS) and resistant starch (RS). Compared with T1, T4-T6 significantly decreased RDS by 13.13%-19.13% and increased RS by 23.34%-28.65%. Mantel test, principal component analysis and random forest modeling confirmed starch granule size distribution, pasting and thermal properties as core regulators of digestibility. Overall, the optimal rate of foliar application of ICE6 was 90 g ha^-1, which provides an important reference for improving waxy maize starch quality and developing cultivation practices for high-quality starch production.