High insoluble fibre content increases in vitro starch digestibility in partially baked breads.

摘要

Wheat breads prepared from frozen partially baked breads were characterised by their content of rapidly digestible starch (RDS) and slowly digestible starch (SDS), using the in vitro starch digestibility method developed by Englyst. Breads with different contents and types of fibre and breads prepared with different fermentation processes were studied. Bread with inulin and a double fermentation had the lowest RDS content (58.8 +or- 1.7 and 60.0 +or- 1.9% DM, respectively). Wheat bran bread, seeded bread, triple fermentation white bread and baguette-type bread showed RDS values of 63.1 +or- 1.7-65.7 +or- 1.7 with no significant differences between them (p < 0.05). The fraction of SDS was higher in wheat breads than in breads with added fibre. The highest starch digestive rate index (SDRI) values were obtained for the 3 types of breads with added fibre, which ranged from 91.8 +or- 3.5 to 95.8 +or- 3.5 vs 80.2 +or- 3.5 to 87.5 +or- 3.5 for white wheat breads. A significant (p < 0.01) positive linear correlation between insoluble fibre content and SDRI was obtained (R2 = 0.96). Insoluble fibre dilutes and disrupts the gluten network and probably weakens the interaction between gluten and starch, which protects starch from digestive enzymes action. SEM microstructure of bread crumbs corroborated this statement.