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Polyphenol Extraction from Humulus lupulus (Hop) Using a Neoteric Glycerol/L-Alanine Deep Eutectic Solvent: Optimisation, Kinetics and the Effect of Ultrasound-Assisted Pretreatment

School of Agricultural Sciences, University of Thessaly, 43100 Karditsa, Greece
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Received: 20 July 2019 / Revised: 2 August 2019 / Accepted: 6 August 2019 / Published: 8 August 2019
The investigation presented herein had as its scope the development of an integrated process for the efficient extraction of polyphenols from hop. For this purpose, a novel, natural deep eutectic solvent (DES) was synthesised, composed of glycerol and L-alanine, and the process was optimised by deploying a response surface methodology based on a Box–Behnken design. The variables considered were the DES/water proportion, the liquid-to-solid ratio and the stirring speed. Under the optimised conditions, the yield in total polyphenols achieved was 118.97 ± 8.27 mg gallic acid equivalents per g of dry mass. Ultrasonication, incorporated into the process as a pretreatment step, was shown to significantly change the kinetic pattern of polyphenol extraction and contributed to attaining higher yields only at 80 °C, whereas at lower temperatures a supressing effect was observed. Furthermore, increasing temperature was negatively correlated with the second-order extraction rates, evidencing a slow-down of the extraction rate at elevated temperatures. View Full-Text
Keywords: antioxidants; deep eutectic solvents; Humulus lupulus; kinetics; polyphenols; ultrasound-assisted extraction antioxidants; deep eutectic solvents; Humulus lupulus; kinetics; polyphenols; ultrasound-assisted extraction
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MDPI and ACS Style

Lakka, A.; Karageorgou, I.; Kaltsa, O.; Batra, G.; Bozinou, E.; Lalas, S.; Makris, D. Polyphenol Extraction from Humulus lupulus (Hop) Using a Neoteric Glycerol/L-Alanine Deep Eutectic Solvent: Optimisation, Kinetics and the Effect of Ultrasound-Assisted Pretreatment. AgriEngineering 2019, 1, 403-417. https://0-doi-org.brum.beds.ac.uk/10.3390/agriengineering1030030

AMA Style

Lakka A, Karageorgou I, Kaltsa O, Batra G, Bozinou E, Lalas S, Makris D. Polyphenol Extraction from Humulus lupulus (Hop) Using a Neoteric Glycerol/L-Alanine Deep Eutectic Solvent: Optimisation, Kinetics and the Effect of Ultrasound-Assisted Pretreatment. AgriEngineering. 2019; 1(3):403-417. https://0-doi-org.brum.beds.ac.uk/10.3390/agriengineering1030030

Chicago/Turabian Style

Lakka, Achillia, Ioanna Karageorgou, Olga Kaltsa, Georgia Batra, Eleni Bozinou, Stavros Lalas, and Dimitris Makris. 2019. "Polyphenol Extraction from Humulus lupulus (Hop) Using a Neoteric Glycerol/L-Alanine Deep Eutectic Solvent: Optimisation, Kinetics and the Effect of Ultrasound-Assisted Pretreatment" AgriEngineering 1, no. 3: 403-417. https://0-doi-org.brum.beds.ac.uk/10.3390/agriengineering1030030

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