Use of sourdough lactobacilli and oat fibre to decrease the glycaemic index of white wheat bread

Area of Science:

• Food Science
• Nutritional Science
• Microbiology

Background:

• White wheat bread typically has a high glycaemic index (GI).
• Resistant starch (RS) formation in bread is influenced by fermentation methods.
• Dietary fibers and acidification can impact bread's starch digestibility.

Purpose of the Study:

• To decrease the glycaemic index (GI) of white wheat bread.
• To investigate the role of sourdough fermentation and dietary fibers in enhancing resistant starch (RS) and reducing the hydrolysis index (HI).

Main Methods:

• Comparing RS formation in breads fermented with baker's yeast versus sourdough (Lactobacillus plantarum P1 and Lactobacillus brevis P2).
• Evaluating the effect of oat fiber and lactic acid (sourdough acidification) on the hydrolysis index (HI) of a white wholemeal flour mixture.
• Assessing the in vivo glucose response and GI in healthy volunteers using white wheat bread versus sourdough white wholemeal bread enriched with oat fiber.

Main Results:

• Sourdough fermentation with L. plantarum P1 and L. brevis P2 significantly increased RS content compared to baker's yeast.
• Oat fiber (5%) and sourdough acidification (using lactic acid) effectively decreased the hydrolysis index (HI) of the bread.
• Sourdough white wholemeal bread enriched with oat fiber demonstrated a significantly lower GI (53.7%) compared to standard white wheat bread (72%).

Conclusions:

• Sourdough fermentation combined with oat fiber addition is an effective strategy to reduce the GI of white wheat bread.
• The observed decrease in GI is attributed to increased resistant starch formation and reduced pH due to sourdough acidification.
• The modified bread also exhibited improved physical characteristics and sensory attributes.