Antioxidants from aqueous decoction of carob pods biomass (Ceretonia siliqua L.): Optimisation using response surface methodology and phenolic profile by capillary electrophoresis

► RSM was used for optimisation of aqueous decoction aiming antioxidants from carob biomass. ► Aqueous decoction provides added-value products from carob biomass within biorefining. ► Experimental design optimised antioxidants extraction from carob kibbles. ► Aqueous decoction of carob kibbles could be used as a dietary source of antioxidants. ► Aqueous decoction functions as biomass pretreatment prior to further processing. Carob (Ceratonia siliqua L.) kibbles, a by-product of the carob bean gum production, were extracted by decoction and evaluated for its phenolic profile and potential use as an added-value antioxidant-rich product. The effect of decoction time (8–20min) and temperature (80–100°C) on the polyphenols content and overall antioxidant capacity expressed as percentage inhibition of the DPPH and ABTS free radicals, was performed using a Doehlert experimental design to assess the antioxidants extraction efficiency. It was observed that temperature had the most significant effect. The best conditions for total polyphenols and tannins extraction were 98.5°C and 17min, where ca. 39.5mg GAE/g kibbles and 25.8mg GAE/g kibbles on a dry basis were obtained, respectively. Under these conditions, inhibition of DPPH and ABTS radicals were 85% and 90%, respectively, showing the promising use of this biomass as an antioxidant source, which could be used, for example, in functional beverages.