Optimization of torrefaction conditions on antioxidant activity of prickly pear seeds extract using response surface methodology and chemometric analysis

The prickly pear (Opuntia ficus-indica L., Cactaceae) seeds can be used as an alternative food product by the torrefaction process. Torrefaction is a pre-treatment process of biomass into solid fuel within a temperature range of 60–200 °C. This study aimed to investigate the effect of torrefaction parameters on the antioxidant potential of prickly pear seeds, which is considered a food by-product, by using the Central Composite Design approach (CCD).The best torrefaction parameters found to have the optimal phytochemical contents were: 200 °C and 50 min with 104.86 ± 1.94 GAE/g extract for Total Phenolic Content (TPC), 200 °C and 50 min with 81.23 ± 0.90 mg QE/g extract for Total Flavonoid Content (TFC), 200 °C and 50 min with IC50 = 90.66 ± 2.09 μg/ml for free radical scavenging activity (DPPH assay), 200 °C and 50 min with IC50 = 124.9 ± 4 μg/ml for radical cation total antioxidant capacity (ABTS assay). Our results demonstrated an increase of antioxidant activities with the increase of torrefaction parameters. Therefore, torrefaction has proven to be a value-added process to exploit prickly pear seed biomass and use it as a source of antioxidant food additives.