Response surface optimisation of antioxidant extraction from kinema, a Bacillus-fermented soybean food

► Deploying RSM, three parameters were optimised for antioxidant extraction. ► Total phenol content and DPPH-scavenging activity were checked using kinema extract. ► The optimum conditions for antioxidant extraction were 100% MeOH, 50°C and 30min. ► Multi-response optimisation of the parameters confirmed validity of the model. ► Experimental and predicted values of the responses did not differ significantly. The objective of this work was to optimise different parameters (solvent concentration, time and temperature) for antioxidant extraction from kinema, demonstrated by total phenol content (TPC) and DPPH-scavenging activity (DSA), using response surface methodology. A central composite design was performed to determine the effect of solvent concentration (methanol, 30–100%), temperature (30–60°C) and time (30–150min) on the TPC and DSA of the extract. The solvent concentration and temperature had the most significant (p