The combined effect of gluten addition and semolina cell wall integrity reduces the oral sugar release and the insulinemic response to bread in healthy volunteers

Purpose: A strategy to reduce starch digestibility is to limit its accessibility to α-amylase by preserving the integrity of cells where starch is encapsulated. Coarse flour is rich in intact cells and can be used for this purpose. However, making bread with coarse flour negatively affects crumb cohesiveness, which may increase the gastric disintegration rate, and enhance starch accessibility. Therefore, this study aimed to assess the combined effect of coarse semolina and its 20% gluten substitution in bread in healthy volunteers on glycemic and insulinemic responses, oral processing and bolus characteristics. Methods: Apparently, healthy volunteers (n = 16) randomly consumed bread made with coarse semolina and 20% gluten substitution (80CS_20G), its counterpart with fine semolina (80FS_20G), and bread with fine semolina and 5% gluten (95FS_5G). The glycemic and insulinemic responses were measured over 2 h after bread consumption. Mastication behaviour, bolus properties and reducing sugar were also evaluated. Results: No differences in glycemic responses and mastication were observed among the samples. 80CS_20G and 80FS_20G exhibited similar textural properties but 80CS_20G released less reducing sugars and elicited a lower insulin response at 30 min than 80FS_20G, probably due to intact cells that limit starch accessibility. Also, 95FS_5G released lower reducing sugars and had lower insulin peak than 80FS_20G. The compact structure of 95FS_5G may have delayed starch hydrolysis by restricting α-amylase accessibility. Conclusion: Combining gluten and coarse semolina resulted in bread with a lower release of reducing sugars, a reduced insulinemic peak and textural properties similar to the counterpart with fine semolina. Clinical trial Registration Number: The trial is registered at ClinicalTrials.gov: NCT06152874.