Production and Use of Fish By-Product Protein Hydrolysates in Breadmaking: Effects on Bread’s Nutritional, Sensory and Physicochemical Characteristics

Abstract Although there is a precedent for enriching bread with plant-based ingredients or muscle tissue, the use of fish protein hydrolysates (FPH) in baking remains underexplored, especially if the FPH comes from fish by-products. The impact of adding FPH from sea bass and salmon heads in bread-making, analysing its sensory, proximate and physicochemical effects was assessed. The influence of different antioxidants during hydrolysis was also evaluated. Four bread formulations were produced with varying levels of wheat flour replacement by FPH (2.5% and 5%) and a control bread. A comprehensive evaluation of the breads included analyses of proximate composition, texture, colour, sensory attributes and crumb structure at both macro- and microscopic levels. The incorporation of FPH led to increased protein content and moisture, particularly noticeable at the 5% replacement level. Sensory differences emerged between the control and FPH-enriched breads; the 2.5% formulation retained desirable sensory properties, whereas the 5% substitution introduced less favourable traits such as bitterness, a fishy odour and rancid notes. Textural changes included greater bread hardness, which correlated with modifications in crumb microstructure, notably larger alveoli and subtle shifts in crust and crumb colour. Among the tested antioxidants, those based on carnosic acid proved most effective in preserving quality. In conclusion, FPH could serve as a viable option for nutritionally enriching bread, although it is advisable to keep substitution levels low (2.5%). These findings underscore the potential of FPH as an ingredient in baked products and contribute to circular economy in the fishing industry.