Fermentation improves the bioactivity of fruit by-products; therefore, this study aimed to increase the bioactive compound content in granadilla (Passiflora ligularis) seed flour (with 50% and 70% initial moisture) through solid-state fermentation using the fungus Aspergillus niger. The extracts were obtained with distilled water, 40% acetone, 80% acetone, 40% ethanol, or 80% ethanol. The highest total phenolic (4713.3 of gallic acid equivalent/100 g of granadilla seed flour in dry basis) and total flavonoid (1910.4 mg of quercetin/100 g of granadilla seed flour in dry basis) contents were obtained with granadilla flour at 50% initial moisture fermented for 48 h with 80% acetone extractor solvent. The highest antioxidant activity was obtained with 80% acetone from flour fermented for 168 h. The chromatographic analysis showed 10 compounds identified in the 80% acetone extracts of fermented flour; gallic acid and epigallocatechin were the major compounds. Gallic acid, catechin, 6,2'-di-hydroxyflavone, ethyl gallate and coumarin had higher concentrations in extracts of fermented flours when compared with unfermented ones. Only fermented flours showed the presence of protocatechuic acid compound. The solid-state fermentation was efficient to obtain extracts of granadilla seed flour enrichment of antioxidant bioactive compounds with potential of application in food, cosmetic and pharmaceutical industries.
Keywords: Natural antioxidant; biotechnology; exotic fruit; flavonoid; phenolic.