Sub-standard peas valorization through Lactiplantibacillus plantarum fermentation to produce a biologically active ingredient for bread fortification

Sub-standard peas (sP), are an abundant waste generated after the processing of peas still containing valuable components including proteins, fibers, and bioactive compounds. This study proposes a fermentation approach to convert sub-standard Peas (sP) into a novel functional bioingredient for bread enrichment. To this aim, sP were grinded, mixed with water (40:60 wt ratio) and fermented by Lactiplantibacillus plantarum ITM21B (5.00 log10 CFU/g, 14 h, 37 ◦C), obtaining the bioingredient Bio21B-P which was investigated for its nutritional composition and biological activity. Bio21B contained, in comparison to unfermented peas, lactic and acetic acids (29.09 and 4.41 mmol/kg, respectively), increased content of globulins and glutelins (from 0.37 to 2.97 g/kg and from 0.98 to 2.96 g/kg, respectively) and total phenol content (from 13.92 to 19.08 mg GAE/L) leading to higher antioxidant activity. The biological effects of fermented sP extract were tested on HepG2 liver cells at 0.01, 0.1 and 1 mg/mL, following treatment with oleate/palmitate (OP) to mimic hepatic steatosis. A relevant but not significant reduction of OP-induced lipid droplet accumulation at 1 mg/mL was observed. The freeze-dried Bio21B-P was then used to partially replace wheat flour (0%, 2.5%, 7.4%, 16.6% and 25.4%, w/w flour) in bread. The increased polyphenol content in Bio21B-P led to a significant lowering in predicted glycaemic index and starch hydrolysis, directly correlated to flour replacement (from 62.02 in the CTR to 50.24 in bread with the highest bioingredient integration). Protein content significantly increased, mainly albumins and globulins, as the content of the pea bioingredient increased. A concomitant increase of the total free amino acids from 184.20 (0% replacement) to 1886.30 mg/kg (25.4% replacement) was registered. The presence of Bio21B-P at 7.4% substitution level significantly reduced the hardness while increasing cohesiveness respect to control bread. Higher bioingredient incorporation led to a deterioration of the bread structure. Overall, fermentation improved the biological and functional properties of legume waste allowing the production of a bread-fortifying ingredient, while also reducing waste.