Optimization of simultaneous microwave/ultrasonic-assisted extraction of phenolic compounds from walnut flour using response surface methodology

• Published in: Pharmaceutical biology Vol. 55; no. 1; pp. 1999 - 2004
• Main Authors: Luo, Yan, Wu, Wanxing, Chen, Dan, Lin, Yuping, Ma, Yage, Chen, Chaoyin, Zhao, Shenglan
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 2017; Taylor & Francis Ltd; Taylor & Francis Group
• Subjects: Antioxidants; central composite design (CCD); Chinese medicine; Chromatography, Liquid - methods; constituent identification; Cosmetics; Ellagic acid; Flour; Food; Gallic acid; Juglans; LC-MS; Mass Spectrometry - methods; Methods; Microwaves; Oil and gas industry; Petroleum production; Phenolic compounds; Phenols - analysis; Phenols - isolation & purification; Plant Extracts - analysis; Plant Extracts - isolation & purification; Polyphenols; Surface Properties; total polyphenol yield (TPY); Ultrasonic imaging; Ultrasonic Waves; Ultrasound; Walnut polyphenol; total polyphenol yield (TPY); Walnut polyphenol; constituent identification; central composite design (CCD); LC–MS
• ISSN: 1388-0209; 1744-5116
• DOI: 10.1080/13880209.2017.1347189

Context: Walnut is a traditional food as well as a traditional medicine recorded in the Chinese Pharmacopoeia; however, the large amounts of walnut flour (WF) generated in walnut oil production have not been well utilized. Objective: This study maximized the total polyphenolic yield (TPY) from the walnut flour (WF) by optimizing simultaneous ultrasound/microwave-assisted hydroalcoholic extraction (SUMAE). Materials and methods: Response surface methodology was used to optimize the processing parameters for the TPY, including microwave power (20-140 W), ultrasonic power (75-525 W), extraction temperature (25-55 °C), and time (0.5-9.5 min). The polyphenol components were analysed by LC-MS. Results: A second-order polynomial model satisfactorily fit the experimental TPY data (R 2  = 0.9932, P < 0.0001 and R adj 2     = 0.9868). The optimized quick extraction conditions were microwave power 294.38 W, ultrasonic power 93.5 W, temperature 43.38 °C and time 4.33 min, with a maximum TPY of 34.91 mg GAE/g, which was a rapid extraction. The major phenolic components in the WF extracts were glansreginin A, ellagic acid, and gallic acid with peak areas of 22.15%, 14.99% and 10.96%, respectively, which might be used as functional components for health food, cosmetics and medicines. Discussion and conclusion: The results indicated that walnut flour, a waste product from the oil industry, was a rich source of polyphenolic compounds and thus could be used as a high-value functional food ingredient.