Optimization of Phenolic Compounds Recovery from Pistachio Hull Using Accelerated Solvent Extraction

Area of Science:

• Agricultural Science
• Food Chemistry
• Green Chemistry

Background:

• Pistachio hulls (PH) are abundant agro-industrial by-products.
• PH contain valuable phenolic compounds with antioxidant and health-promoting properties.
• Accumulation of PH poses environmental challenges.

Purpose of the Study:

• To optimize phenolic compound extraction from PH using conventional solvent extraction (CSE) and accelerated solvent extraction (ASE).
• To compare the efficacy of CSE and ASE for phenolic compound recovery and antioxidant activity.
• To identify key phenolic compounds in PH extracts.

Main Methods:

• Response surface methodology (RSM) was employed to optimize extraction conditions.
• CSE and ASE techniques were utilized for phenolic compound extraction.
• Phenolic content was quantified using gallic acid equivalents (GAE).
• Radical-scavenging activity was assessed using DPPH assay.
• Individual phenolic compounds were identified and quantified.

Main Results:

• ASE, using 23% ethanol in water at 180 °C for 15 min, yielded the highest phenolic recovery (9.92 ± 0.09 g GAE/100 g DM) and DPPH radical-scavenging activity (IC50 = 0.16 ± 0.00 mg/mL).
• Gallic acid was the predominant phenolic compound (35.7-48.1% of total phenolics), followed by 3,4-dihydroxybenzoic acid, 4-hydroxybenzoic acid, and 2,5-dihydroxybenzoic acid.
• ASE demonstrated superior performance compared to CSE for extracting phenolic compounds from PH.

Conclusions:

• ASE is an effective and eco-friendly method for valorizing pistachio hulls.
• Optimized ASE conditions yield high-purity phenolic extracts with significant antioxidant potential.
• This approach contributes to waste reduction and supports the development of the bioeconomy.