Biorefining of Walnut Shells into Polyphenol-Rich Extracts Using Ultrasound-Assisted, Enzyme-Assisted, and...

Area of Science:

• Agricultural Chemistry
• Food Science
• Biotechnology

Background:

• Walnut (Juglans regia L.) shells are agro-industrial by-products abundant in polyphenols.
• Polyphenols possess significant antioxidant properties, making them valuable for various applications.

Purpose of the Study:

• To investigate and compare traditional and advanced extraction techniques for recovering bioactive compounds from walnut shells.
• To evaluate the efficiency of ultrasound-assisted extraction (UAE), enzyme-assisted extraction (EAE), pressurized liquid extraction (PLE), and combined ultrasound-enzyme extraction (US-EAE).

Main Methods:

• Extraction techniques: maceration, UAE, EAE, PLE, and US-EAE.
• Analysis: Total phenolic content (TPC), antioxidant capacity (ABTS•+, DPPH•), and polyphenol profiling using UPLC-ESI-MS/MS.
• Chemometric analysis: Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA).

Main Results:

• US-EAE achieved the highest TPC (5625 mg GAE/100 g dw) and antioxidant activity.
• UAE yielded the second-highest TPC (4129 mg GAE/100 g dw).
• Key polyphenols identified include ellagic acid, vanillin, and quercitrin.

Conclusions:

• Innovative extraction technologies, especially US-EAE, significantly enhance polyphenol recovery from walnut shells.
• Walnut shells represent a sustainable source of bioactive compounds for functional applications.
• Optimized extraction conditions are crucial for maximizing yield and bioactivity.