Abstract
Winemaking is a process that generates a large volume of solid waste biomass, which is currently under extensive investigation as a bioresource of precious polyphenolic compounds. These substances are retrieved from vinification side streams principally by deploying solid–liquid extraction methods. In this frame, the present investigation had as objective the development of an alternative, green extraction process for polyphenols, through integration of ultrasonication as a pretreatment stage, and subsequent extraction with aqueous β-cyclodextrin. Polyphenol recovery from red grape pomace (RGP) was shown to be significantly enhanced by ultrasonication pretreatment, and the use of β-cyclodextrin effectively boosted the aqueous extraction. Under optimized conditions, established by response surface methodology, the maximum yield in total polyphenols was 57.47 mg GAE g−1 dm, at 80 °C, requiring a barrier of 10.95 kJ mol−1. The extract produced was significantly enriched in catechin and quercetin, compared to the aqueous extract, exhibiting also increased antiradical activity. These findings highlighted the value of the process developed for targeted recovery of certain polyphenols and the preparation of task-specific extracts.
Highlights
The agricultural activity related to food production has as a result the generation of wastes, which, according to FAO, in U.S.A. and in China only may exceed 47 million tons [1]
The ferric-reducing power was determined with a modified FRAP assay, and results were expressed as μmol ascorbic acid equivalents (AAE) per g dry mass
The desirability function permitted the determination of the optimal values for all three independent variables, which were concentration of CD (CCD) = 1.50% (w/v), RL/S = 90 mL g−1, and time of ultrasonication pretreatment (tUS) = 30 min
Summary
The agricultural activity related to food production has as a result the generation of wastes, which, according to FAO, in U.S.A. and in China only may exceed 47 million tons [1]. The wine industry has a crucial position in the agro-industrial sector, as grapes are one of the most important fruit crops worldwide [4]. The grape production was estimated around 77.8 metric tons in 2018 [5] and during vinification, approximately 25% of the grape mass results in grape marc. It has been estimated that the production of 6 L of wine is accompanied by approximately 1 kg of grape marc, which accounts for worldwide production of 10.5–13.1 million tons, on an annual basis. Grape marc consists principally of stems, skins, and seeds, which are the residues of grape crushing and juicing (pressing) steps. This bio-waste is rich in multifunctional polyphenols, which belong
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