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 30 min. ► Multi-response optimisation of the parameters confirmed validity of the model. ► Experimental and predicted values of the responses did not differ significantly.