Effect of nixtamalization with Ca(OH)2, CaCl2, and CaCO3 on the protein secondary structure, rheological, and textural properties of soft wheat flour doughs

Unravelling the anthocyanin-binding capacity of native starches from different botanical origins

In this study, the cyanidin-3-O-glucoside (C3G)-binding capacities of three native starches were investigated. While potato starch had the largest binding capacity of 0.34 mg/100 mg, corn and pea starch had binding capacities of 0.17 and 0.06 mg/100 mg. Confocal microscopy confirmed the binding results and revealed close associations between the surface properties and binding capacities. These findings were further substantiated with wettability and gelatinization results. The morphological observations showed that corn starch had advantageous particle sizes and more surface gullies, providing more opportunities to bind C3G. The zeta potential results, however, indicated that potato starch had the highest negative surface charges (-24 mV). These favorable electronic characteristics were believed to be responsible for the strongest electrostatic interactions. Hydrogen bonds, however, had a negligible effect on the formation of complexes. Overall, the negative surface charges and specific surface areas of the native starches were the most important factors determining C3G-binding capacities.

Effect of Sitophilus zeamais (Coleoptera: Curculionidae) Infestation on the Protein Physicochemical and Structural Properties of Wheat Grain

Boring pests such as Sitophilus zeamais (S. zeamais) are major threats in grain storage. However, how these pests affect the proteins of stored grains remains largely unknown. Here we aimed to investigate the effect of S. zeamais infestation on wheat protein during postharvest storage. In this study, wheat grain infested by S. zeamais was sampled at egg (4 d), larval (20 d), pupal (35 d), and adult stages (45 d), respectively. The protein's physicochemical and structural properties and the edible quality of whole wheat noodle were analyzed. The results showed that S. zeamais infestation significantly decreased the quality of wheat protein by altering its constitution and structure properties. Especially, compared with the control, the content of wet and dry gluten, gluten index, sodium dodecyl sulfate sedimentation volume, sulfhydryl groups, and disulfide bonds in insect-infested wheat decreased by 19.40, 5.42, 18.40, 8.12, 29.13, and 14.30%, respectively, during the storage period of one life cycle of S. zeamais. Additionally, the proportions of wheat protein fractions (albumin [1.16-fold], globulin [0.96-fold], gliadin [1.16-fold], and glutenin [0.95-fold]) and secondary structures (α-helix [0.91-fold], β-fold [0.96-fold], β-turn [1.06-fold], and random coil [1.05-fold]) of protein changed significantly, and the gluten network structure was broken in S. zeamais-infested wheat. Furthermore, the color of whole wheat noodle became darker, cooking loss rate increased, and textural properties (hardness, adhesiveness, springiness, cohesiveness, chewiness, and resilience) decreased as well. The results in the present study provided new insights for analyzing the quality deterioration mechanism and further quality improvement of boring pests-infested wheat grain.