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BACKGROUND RESULTS CONCLUSION The fermentation of Qu (FQ) is a novel method to modify the properties of starch to expand its application and especially to increase the resistant starch (RS) content. Using waxy maize starch (WMS) as a fermentation substrate can increase the RS content significantly but it may be time consuming and not cost effective due to the almost negligible RS content of WMS. To solve this problem, we hypothesized that sub‐high amylose starch (s‐HAMS), with an amylose content close to 50% could be an ideal substrate for FQ.The results showed that FQ did not change the shape and the particle size of starch granules, the gelatinization peak (Tp), or the conclusion temperature (Tc), but the slowly digested starch content declined. Rapidly digested starch content fluctuated during FQ and the amylose content decreased within 36 h and then increased. Within 24h, FQ significanlty increased these values: the RS content, relative crystallinity (RC), the ratio of FTIR absorbances at 1047/1022cm‐1, the diffraction peak at 19.8° in X‐ray diffraction (XRD), and the gelatinization onset temperature (To) increased significantly, within 24 h of FQ. However, after 24 h of fermentation, the RS content, RC, the ratio of FTIR absorbances at 1047/1022 cm−1, and gelatinization enthalpy (ΔH) decreased significantly.Sub‐high amylose starch is more suitable for FQ to produce low digestibility starch, and the increase in RS may be due to the formation of ‘amylose‐lipid’ complexes (RS5). © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Drought stress (DS) is the main abiotic stress that maize suffers during its whole growth period, and maize is also sensitive to DS. It had been demonstrated that DS could improve the quality of normal maize starch. However, waxy maize, which has special properties, has not been explored in depth, which limits the breeding and cultivation of waxy maize varieties and the application of waxy maize starch. Therefore, in this study, we investigated the effects of DS on the biosynthesis, structure, and functionality of waxy maize starch. RESULTS: The results showed that DS decreased the expression level of SSIIb, SSIIIa, GBSSIIa, SBEI, SBEIIb, ISAII, and PUL, but increased the expression level of SSI and SBEIIa. DS did not change the average chain length of amylopectin, while increased the relative content of fa chains (RCfa) and decreased the RCfb1 and RCfb3. Furthermore, DS decreased the amylose content, amorphous lamellar distance da, semi‐crystalline repeat distance, and average particle size, whereas it increased the relative crystallinity, crystalline distance dc, the content of rapidly digested starch in the uncooked system and resistant starch content in both the uncooked and cooked system. Conclusions: For waxy maize, DS could raise the relative expression level of SSI and SBEIIa, thus increasing RCfa. The larger number of RCfa could create steric hindrance, which can lead to producing more resistant starch in waxy maize starch. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]