Sulfur affects multi-scale starch structures and its contribution to the cookie-baking quality of wheat subjected to shade stress

The components and structure of starch macromolecules critically determine its food-use properties. However, elemental sulfur supplementation affects the relationship between starch structure and the cookie-making quality of wheat under shaded environments remains unclear. Here, we investigated the effect of sulfur on the starch multi-scale structures and its contribution to the cookie-baking quality of wheat after pre- or post-anthesis shading. Compared with the unshaded control, shade stress decreased the amylose and total starch contents, formed smaller B-type starch granules, narrowed the molecular weight distribution, and decreased the amylopectin long-chain proportion, crystallinity, viscosity, and spread ratio of cookies. Weak-gluten cultivars are more sensitive to shade stress than strong-gluten cultivars. Under shaded environments, sulfur increased the amylopectin content, proportion of amylopectin short chains, and total starch content, increasing the mean diameter of starch granules and viscosity, ultimately decreasing the cookie hardness. The random forest model revealed that the surface area of the starch granules (18.7 %) and amylopectin B3 chain (6.7 %) contributed the most to the variation in the cookie spread ratio. Cookie hardness was determined mainly by the total starch (7.8 %), amylopectin (6.3 %), and trough viscosity (5.0 %). Our results help to design strategies for achieving superior-quality wheat in the context of global dimming.