Title Biorefining of walnut shells into polyphenol-rich extracts using ultrasound-assisted, enzyme-assisted, and pressurized liquid extraction coupled with chemometrics
Authors Acoglu Celik, Busra ; Celik, Muhammed Alpgiray ; Jūrienė, Laura ; Jovaišaitė, Jovita ; Kazernavičiūtė, Rita ; Bekar, Erturk ; Yolci Omeroglu, Perihan ; Venskutonis, Petras Rimantas ; Kamiloglu, Senem
DOI 10.3390/foods14132245
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Is Part of Foods.. Basel : MDPI. 2025, vol. 14, iss. 13, art. no. 2245, p. 1-28.. ISSN 2304-8158
Keywords [eng] Juglans regia L. shell ; green extraction ; combined extraction ; phenolic compounds ; antioxidant capacity ; principal component analysis
Abstract [eng] Walnut (Juglans regia L.) shells are valuable agro-industrial by-products rich in polyphenols. This study investigated traditional (maceration) and advanced extraction techniques—ultrasound-assisted extraction (UAE), enzyme-assisted extraction (EAE), pressurized liquid extraction (PLE), and combined ultrasound–enzyme extraction (US-EAE)—to recover bioactive compounds from walnut shells. Extraction efficiency, total phenolic content (TPC), antioxidant capacity (ABTS•+, DPPH•), and polyphenol composition were evaluated. UPLC-ESI-MS/MS identified key polyphenols including ellagic acid, 4-hydroxybenzoic acid, vanillin, taxifolin, and quercitrin. The highest TPC (5625 mg GAE/100 g dw) was found in extracts subjected to US-EAE, in which ultrasound pretreatment (200 W, 10 min) was followed by enzymatic extraction using 0.06 mL/g Viscozyme® L at pH 3.5 and 45 °C. Under the same extraction conditions, UAE alone yielded the second highest TPC (4129 mg GAE/100 g dw). The highest ABTS•+ scavenging activity (14,478 mg TE/100 g dw) and enhanced DPPH• activity (45.38 mg TE/100 g dw) were also observed in US-EAE extracts. Chemometric techniques (PCA and HCA) revealed meaningful clustering and variation patterns among methods. These findings highlight the potential of walnut shells as a sustainable source of polyphenols and demonstrate the effectiveness of innovative extraction technologies in maximizing bioactive compound recovery for potential functional applications.
Published Basel : MDPI
Type Journal article
Language English
Publication date 2025
CC license CC license description