Optimization Of Solid-State Fermentation To Increase Total Phenolic Compound Release In Passion Fruit Peel Extract And Evaluation Of Antioxidant Activity

Abstract

Solid-state fermentation (SSF) has been considered as one of the most cost effective techniques for solid waste valorization. Therefore, this study aimed to identify the optimal conditions for SSF and post-SSF extraction to obtain the highest total phenolic content (TPC) in passion fruit peel extract (PFPE). Specifically, the optimal SSF conditions were determined to be 1.4 cm2 , 74%, and 29oC for material size, moisture, and fermentation temperature, respectively. With respect to post-SSF ultrasound-assisted extraction, the conditions for the highest TPC yield were 60%, 7:1 mL/g and 40oC, corresponding to solvent concentration, solvent-to-solid ratio and sonication temperature, respectively. The differences in the phytochemical composition of fermented passion fruit peel concentrated extract (FE) were then compared with unfermented passion fruit peel concentrated extract (UE). In addition, the presence of mycotoxins in FE was undetectable at the minimum detectable level of 0.1µg/kg. Under optimal SSF and post-SSF extraction conditions, the fermented passion fruit peel (FPFP) has significantly higher TPC recovery than unfermented passion fruit peel (UPFP), in agreement with the higher antioxidant activity for FE as evaluated by three antioxidant assays (DPPH, ABTS, and FRAP assays). All of these results indicated the potency of FE for cosmetic, food and pharmaceutical applications.