2nd International Meeting on Deep Eutectic Systems. Online (FCT-Universidade Nova de Lisboa), 15-17 June 2021.
Bruno D. A. Pinheiro, Maria Hijosa-Valsero, André M. da Costa Lopes, Armando J. D. Silvestre. Valorization of vine shoots biomass assisted by acidic deep eutectic solvents.
Wine production is an essential economic engine in most regions across the Iberian Peninsula. However, this activity generates a high amount of by-products, such as vine shoots, which need to be handled and valorized within a circular economy perspective. Therefore, sustainable and cheap processes capable of extracting value from these raw materials are required. In this work, acidic deep eutectic solvents (DES) were tentatively used as green solvents in the extraction of value-added compounds from vine shoots prior to its fractionation. DES combining cholinium chloride ([Ch]Cl) as hydrogen bond acceptor (HBA) with different hydrogen bond donors (HBD), such as p-toluenesulfonic acid (pTSA), malic acid (MA), glycolic acid (GLY), tartaric acid (TART), citric acid (CIT), were studied. These acidic DES showed capacity to extract phenolic compounds, including anthocyanins, where [Ch]Cl:pTSA demonstrated the best performance among them. The extraction of these compounds with [Ch]Cl:pTSA was further examined by studying HBA:HBD molar ratio, time, temperature and water content in DES (25 wt% and 50 wt%). A higher molar ratio of [Ch]Cl enabled a better selectivity towards the extraction of anthocyanins, possibly due to the stabilization of the anthocyanin flavylium cation by the Cl- as counterion. In addition, the presence of water (25 wt%) improved anthocyanin extraction, although decreasing its selectivity. Moreover, prolonged extraction (> 1 h) negatively affected the extraction performance due to anthocyanins degrading. The optimal conditions towards selective extraction of anthocyanins was obtained with [Ch]Cl:pTSA (3:1) at 80 °C for 1 h reaching a maximum yield of 6.46 (± 0.02) mg.gbiomass-1. These anthocyanin-rich extracts not only may provide antioxidant activity, but also disclose potential to be used in natural dyeing applications, due to its deep red color.
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