Enhancing carob flour (Ceratonia siliqua L.) for by-product utilization in food industries: Carob syrup production, functional profiling and application

The focus on by-product valorization in the food industry, particularly from the carob pod, underscores a commitment to sustainability and resource efficiency. This fruit, sourced from the leguminous evergreen carob tree (Ceratonia siliqua L.), is renowned for its adaptable flavour and nutritional value, in Mediterranean regions such as Portugal. Its production yields significant by-products, presenting environmental challenges when not managed efficiently. Innovative approaches, including integral carob flour production, aim to optimize utilization while minimizing waste and energy consumption. This study repurposed carob waste to produce novel, value-added ingredients like carob syrup, by thermal hydrolysis of integral carob flour using water at 1:3 solid-to-liquid ratio - obtaining up to 50 % solubility yield. The resulting syrup exhibited 72 % °Brix, a melting temperature (Tm) of approximately 130 °C and predominantly viscous behavior with minimal elastic (solid-like) response. Lastly, the syrup was incorporated into a carob-based brigadeiro, replacing conventional glucose-fructose syrup. Simulated gastrointestinal digestion revealed enhanced bioaccessibility of sugars and phenolics, and increased antioxidant activity during the intestinal phase. Despite sugar availability, the prebiotic activity of the syrup decreased when embedded in the brigadeiro matrix, potentially due to interactions with polyphenols or organic acids. Cytotoxicity and permeability assays confirmed safety at ≤0.5 % (w/v) and supported intestinal barrier integrity. These findings support the use of integral carob flour for producing multifunctional ingredients, contributing to circular economy models while meeting consumer demands for healthier, sustainable food products. • Carob syrup was obtained from integral carob flour via thermal-enzymatic hydrolysis. • Syrup showed high antioxidant capacity (DPPH and ABTS) and sucrose-rich profile. • Promoted growth of probiotic strains, highlighting prebiotic potential. • Upcycling carob flour into syrup supports circular economy strategies. • In vitro digestion revealed high bioaccessibility of antioxidants and sugars.