Regulation of baking quality and starch digestibility in whole wheat bread based on ll-glucans and protein addition strategy: Significance of protein-starch-water interaction in dough

Whole wheat bread has high nutritional value but is characterized by inferior quality and a high glycemic index. Studies have shown that adding ll-glucans and protein can improve bread quality. This study investigated the effects of added oat ll-glucan, barley ll-glucan, or yeast ll-glucan on protein synergy and whole wheat dough and bread quality. The mixing properties, rheological properties, and scanning electron microscopy observations showed that the addition of ll-glucan promoted the formation of gluten networks, while the synergy between the wheat proteins and ll-glucan resulted in a more robust and stable gluten network and a stronger physical starch envelope. Rapid visco-analysis and thermal property evaluations showed that ll-glucan addition inhibited the thermal degradation, gelatinization, and retrogradation of starch. Based on the bread quality results, it was found the ll-glucan could cause some damage to the bread baking quality. For example, the hardness of samples with oats, barley, and yeast increased to 881.69 g, 952.97 g, and 631.75 g, respectively, compared to samples without ll-glucan (317.49 g), whereas the inclusion of yeast ll-glucan proved to be less detrimental. Protein and ll-glucan both reduced starch digestion to some degree, and showed better synergistic effects, with the lowest estimated glycemic index of 70.08 observed in bread containing added yeast ll-glucan and protein. Therefore, yeast ll-glucan and protein mixtures could be selected as viable formulations for enhancing the quality of whole wheat bread.