Successful combination of lactic acid bacteria and yeast fermentation and enzymatic treatment to re-cycle industrial bread by-products for bread making

Bread industry generates significant amounts of by-products which are discarded every day with relevant economic and environmental repercussions, despite they still contain high concentrations of potentially exploitable nutrients. Aiming to develop new sustainable solutions, this study explored the synergistic application of enzymatic treatment and sourdough fermentation to re-cycle industrial bread by-products for new sourdough bread making. Lactiplantibacillus plantarum SD69. B2 and Saccharomyces cerevisiae SD69. E3 were used as starters, while α-amylase, amyloglucosidase and protease were assessed for their ability to hydrolyze starch and proteins, providing more available carbon and nitrogen sources for the microorganisms. The bread waste-based sourdoughs made by combining protease and L. plantarum SD69. B2 alone or in combination with S. cerevisiae SD69. E3 were selected based on acidification and growth kinetics, and their biochemical, amino acid, and peptide profiles were also characterized demonstrating promising properties. Therefore, they were used, at different percentages, for bread making. Although a slightly acidic pH and a low leavening power, due to the denatured proteins and gelatinized starch in the bread by-products, the texture and sensory analyses of new breads revealed better textural attributes, smell, acidic taste, and overall acceptability compared to the control. The possible reasons behind such features were discussed. The overall results demonstrated that the approach proposed in this study was effective to valorize bread by-products, and it represents a starting point to develop strategies responding to the current perspective of circular economy in food industry.