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Optimization and kinetics modeling of phenolics extraction from coffee silverskin in deep eutectic solvent using ultrasound-assisted extraction
Author(s)
Date Issued
July 1, 2023
Type
Article
Abstract
This research investigates the effect of extraction parameters on total phenolic content (TPC) and the antioxidant capacity of coffee silverskin (CS) extract using ultrasound-assisted extraction (UAE) in deep eutectic solvent (DES). The optimization was carried out in two stages: (i) the optimization of the UAE condition with the highest TPC; and (ii) a four-factor Box-Behnken design (BBD) to optimize the UAE condition with the optimal TPC; 2,2 diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity; and ferric reducing antioxidant power (FRAP). The results showed that the optimal UAE condition with the highest TPC was 150–250 μm CS particle size; 1,6-hexanediol as hydrogen bond donor (HBD); 1:7 HBA:HBD molar ratio; and 30% (w/w) water content, given choline chloride (ChCl) as hydrogen bond acceptor (HBA), 30 min extraction time and 30 ° C extraction temperature. The BBD-based optimal UAE condition was 30% w/w water content, 45 mL/g liquid/solid ratio, 90 min extraction time and 85 ° C extraction temperature, given the CS particle size of 150–250 μm and the HBA:HBD molar ratio of 1 (ChCl): 7 (1,6 hexanediol), achieving 19.19 ± 0.20 mg GAE/g CS for TPC, 24.06 ± 1.77 mg TE/g CS for DPPH radical scavenging capacity, and 59.13 ± 4.55 mg Fe (II)/g CS for FRAP. The experimental results were in good agreement with the BBD-based predicted results (22.40 mg GAE/g CS for TPC, 24.09 mg TE/g CS for DPPH, and 59.43 mg Fe(II)/g CS for FRAP). The two-site kinetics model best fitted the experimental data, with R2 of 0.991–0.999.
Citation
Heliyon, 9(7), 2023