Alteration of phenolics and antioxidant capacity of gluten-free bread by yellow pea flour addition and sourdough fermentation

Abstract

Gluten-free bread is often characterised by poor nutritional value and bioactive profile. Legume flours have potential for its enrichment, but the effect of sourdough fermentation of legume matrices on the phenolics and antioxidant capacity of bread is scarcely investigated. Thus, this study aimed to determine the effect of partial replacement (25%) of wholemeal rice flour with yellow pea flour on phenolics and antioxidant capacity of gluten-free sourdough and bread. Sourdough was fermented with Lactobacillus reuteri DSM 20016, Lactobacillus fermentum DSM 20052 or Lactobacillus brevis DSM 20054. Free phenolic acids (protocatechuic, 4-hydroxybenzoic, vanillic and ferulic), lactic and acetic acid content was determined by HPLC, and free total phenolic content (TPC), DPPH and FRAP antioxidant capacity by spectrophotometric methods.After 16 h of fermentation, total titrable acidity of the sourdough ranged from 11.85 to 18.97 mL of 0.1 M sodium hydroxide, with lactic/acetic acid content of 2.65–9.41. Yellow pea flour addition substantially increased protocatechuic acid and 4-hydroxybenzoic acid content, but decreased the antioxidant capacity of unfermented dough and bread. Depending on the starter, the sourdough fermentation of pea-rice flour blend and its addition to bread increased the phenolic acid content, TPC and antioxidant capacity. Bread with yellow pea flour and L. brevis sourdough showed the highest improvement in phenolic acid content (40%), TPC (44%) and antioxidant capacity (30% DPPH, 50% FRAP) compared to bread without added sourdough. The study demonstrates the importance of using sourdough fermentation with a carefully selected starter when adding pea flour to gluten-free bread to ensure high antioxidant potential.