Proximate composition, polyphenols, and antioxidant activity of solid state fermented peanut press cake

Area of Science:

• Agricultural Science
• Food Science
• Microbiology

Background:

• Peanut press cake is a byproduct rich in nutrients but often underutilized.
• Polyphenols and antioxidant activities in food matrices can be enhanced through microbial fermentation.
• Solid-state fermentation (SSF) offers a sustainable method for biotransformation of agricultural byproducts.

Purpose of the Study:

• To evaluate the impact of Aspergillus oryzae SSF on peanut press cake (HNG-10 variety).
• To assess changes in polyphenol content, antioxidant capacity, and proximate composition.
• To determine the optimal fermentation time for maximizing beneficial compounds.

Main Methods:

• Solid-state fermentation (SSF) of peanut press cake using Aspergillus oryzae (MTCC 3107).
• Quantification of total phenolics, flavonoids, and tannins.
• Assays for antioxidant activity: DPPH, ABTS, FRAP, and metal chelating.
• Proximate analysis for fat and protein content.
• High-Performance Liquid Chromatography (HPLC) for polyphenol confirmation.

Main Results:

• Maximum polyphenol content reached 25.55 µM/g GAE (phenolic), 101.17 µM/g QE (flavonoid), and 245.33 µg/g TAE (tannin).
• Peak antioxidant activity (free radical scavenging) observed on day 5 of fermentation.
• Significant increases in fat (7.05% to 12.80%) and protein (44.05% to 49.60%) content.
• HPLC confirmed the quantification of polyphenols.

Conclusions:

• Aspergillus oryzae SSF significantly improves the polyphenol content and antioxidant activity of peanut press cake.
• Fermentation leads to a notable increase in the fat and protein content of the substrate.
• SSF is an effective bioprocess for enhancing the nutritional and functional properties of peanut press cake, transforming its physico-chemical profile.