Sourdough bread: An alternative for the valorization of carob flour

• Sourdough improves technological performance of carob-flour breads. • Mixed starters yielded stable and functional sourdough cultures. • Sourdough reduces soluble sugars without loss of antioxidant traits. • Volatile profile showed more esters, fewer aldehydes, terpenes, furfural. • All breads scored high sensory acceptance (≥7/9). Carob flour is a promising food ingredient rich in high-value nutritional bio-compounds, but its high sugar content limits its application in traditional bread making, especially given the growing concern over obesity and diet-related health issues among consumers and manufacturers. In this study, we evaluated the use of sourdough (SD) initiated with two microbial combinations, Saccharomyces cerevisiae / Lactiplantibacillus plantarum (Sc/Lp) and Kazachstania humilis / L. plantarum (Kh/Lp), as a strategy to improve the technological and nutritional properties of breads containing 10 % carob flour. Both starters established a stable community with adequate acidification capacity (pH 4.20–4.48) and efficient L-lactic acid production. Importantly, fermentation reduced soluble sugars by up to 42 % without compromising polyphenol content or antioxidant capacity. Sc/Lp promoted higher CO 2 release, resulting in larger loaf volumes, while both starters enhanced ester formation in the volatile profile. Despite these changes, breads made with SD showed comparable texture, moisture, and weight to the control. Sensory evaluation confirmed high overall acceptance (scores > 7/9) across all formulations, with no significant differences. Beyond its technological value, this approach contributes to a circular economy by valorizing by-products with high functional potential and reducing reliance on commercial yeast. To our knowledge, this is the first study to demonstrate simultaneous sugar reduction and aroma enhancement in carob–wheat breads through the use of defined microbial sourdough starters.