The effect of extraction temperature, time and number of steps on the antioxidant capacity of methanolic banana peel extracts

A solvent extraction method was developed to obtain methanolic extracts rich in antioxidants from banana peel. Central composite design “23 + star” and response surface methodology were used in order to optimise the number of extraction steps, extraction temperature and extraction time. The number of extractions was statistically the most significant factor in scavenging activity against both DPPH and ABTS+ radicals and in the inhibition of TBARS formation, while the extraction temperature had an important impact on the capacity to prevent β-carotene bleaching. However, the effect of the extraction time on antioxidant activity was less important. The optimum values of the factors that influence the capacity to scavenge DPPH and ABTS+ radicals or to inhibit β-carotene bleaching were 3 extractions at 25 °C for 0 min in the water bath (the rest of the extraction process included 1 min of high-speed homogenisation and 20 min of centrifugation). Nevertheless, the optimum conditions to obtain extracts that inhibit TBARS formation were 55 °C for 120 min in the water bath with 3 repetitions of the extraction procedure.