Effect of the fine structure of starch on the gelatinization and retrogradation characteristics of Sorghum varieties

Gelatinization and retrogradation of sorghum are important factors influencing liquor quality. In this study, japonica and waxy sorghum were used as the research objects to elucidate the effects of fine structural changes in different sorghum varieties on their gelatinization and retrogradation characteristics, as well as their physicochemical properties. Changes in the fine structure of starch change its crystallinity and ordering, subsequently changing its gelatinization, retrogradation, and thermal properties. Compared with japonica sorghum (SD,DB), waxy sorghum (XK32,XK35) has a longer average amylopectin chain length (21.51–21.70 DP vs. 21.06–21.22 DP) and a more stable crystal structure (relative crystallinity: 33.18 %–33.20 % vs. 23.14 %–23.45 %). Furthermore, waxy sorghum exhibits higher gelatinization enthalpy (ΔH: 12.64–13.64 J/g vs. 11.02–11.66 J/g) and peak temperature (Tp: 74.90–75.10 °C vs. 72.60–74.00 °C), while showing lower setback (SB: 540.33–712.67 cP vs. 1738.33–1872.67 cP), indicating it is easier to disintegrate and difficult to regenerate after gelatinization. The findings of this study can enhance our understanding of the molecular changes in different starch varieties and provide basic data support for studying the effects of starch structure on grain cooking quality. • Waxy sorghum had higher Fb2 (14.02 %–14.22 %) and average amylopectin chain length (21.51–21.70 DP) than japonica sorghum. • Waxy sorghum showed higher RC (33.18 %–33.20 %) andΔH (12.64–13.64 J/g) vs japonica sorghum's 23.14 %–23.45 % and 11.02–11.66 J/g. • Waxy sorghum's SB (540.33–712.67 cP) was only 31 %–41 % of japonica sorghum's (1738.33–1872.67 cP). • Models: Fa, OD, SB affected BD (R 2 = 0.993); amylopectin ratio and swelling power determined SB (R 2 = 0.997).