Valorizing Bread Residue Through Sourdough Fermentation: From Bread Waste to Bread Taste.

Surplus bread accounts for a significant proportion of food waste in many countries. The focus of this study was twofold: firstly, to investigate the use of carasau bread residue as a sourdough substrate, and secondly, to reuse this sourdough into a new carasau baking process. Selected lactic acid bacteria () and yeast strains ( and ) were used to inoculate three substrates: bread residue (S1), bread residue supplemented with durum wheat middlings (S2), and semolina (S3). Sourdoughs were refreshed for five days by backslopping, and microbiological and physicochemical analyses were performed. Results indicated that incorporating wheat middlings into bread residue enhanced microbial performance, as evidence by a decrease in pH from 6.0 to around 4.5 compared to using bread residue alone as a substrate. Carasau bread produced with the sourdough derived from bread residue and wheat middlings exhibited comparable physicochemical properties to commercial baker's yeast carasau bread, but had better sensory properties, scoring a mean acceptability of 7.0 versus 6.0 for baker's yeast bread. These results show that bread residue supplemented with wheat middlings can serve as a sourdough substrate, allowing its reuse in the baking process to produce high-quality carasau bread and promote the circular economy.