Abstract
Wine production generates large amounts of vine-canes, a devalued by-product that could be used for the recovery of bioactive compounds. In this work, two vine-canes varieties, namely Touriga Nacional (TN) and Tinta Roriz (TR), were submitted to different ultrasound-assisted extraction (UAE) conditions. The highest phenolic and flavonoid content was observed for TR extract obtained at lab-scale without an ice bath and pilot-scale after 60 min of extraction (32.6 ± 2.1 and 26.0 ± 1.5 mg gallic acid equivalent/g dry weight (dw) and 9.5 ± 0.6 and 8.3 ± 0.8 mg epicatechin equivalents/g dw, respectively). Further, all extracts demonstrated a high antioxidant activity to scavenge DPPH free radicals with the best value reached by TR at the lab-scale without an ice bath after 30 min and pilot-scale extraction after 60 min (34.2 ± 2.4 and 33.4 ± 2.1 mg trolox equivalents/g dw, respectively). Extracts phenolic composition were also evaluated by HPLC, demonstrating that resveratrol, myricetin and catechin were the main compounds. According to our knowledge, this is the first time that a pilot scale of UAE of phenolic compounds from vine-canes was performed. This paper represents an important step to the use of UAE as an industrial process to recover bioactive compounds.
Highlights
Grapes are one of the major fruit crops produced throughout the world [1], and in 2018 approximately 57% of the harvested grapes were used to make wine [2]
The highest amount of phenolic and flavonoid compounds was quantified for Tinta Roriz (TR) extracts from ultrasound-assisted extraction (UAE) performed at lab scale without an ice bath after 60 min of extraction (32.6 ± 2.1 mg GAE/g dry weight (DW) and 9.5 ± 0.6 mg EE/g DW, respectively), which was 1.6 and 1.8 fold higher than the value obtained for Touriga Nacional (TN) variety
The results obtained for the UAE are in accordance with the conclusions reported by Sen et al [29], demonstrating that the two Portuguese vine-canes varieties grown under the same conditions presented considerable differences in the total phenolic content (TPC) and total flavonoid content (TFC) values, indicating that these differences may be due to the vine-cane variety
Summary
Grapes are one of the major fruit crops produced throughout the world [1], and in 2018 approximately 57% of the harvested grapes were used to make wine [2]. Organization of Vine and Wine (OIV), Portugal is the country with the 11th highest wine production, being viticulture one of Portuguese’s major economic sectors [2]. It is estimated that one hectare of vineyard leads to the production of approximately 1.75 tons of vine-cane pruning, depending on the vine varieties [3]. In 2016, the amount of vine-canes produced corresponded to approximately. There has been a search for more profitable applications for vine-canes, and several alternatives were already investigated, such as the production of biochars, biofuels, pulp for paper sheets, particle board and lignin [7,8,9,10,11]. Several studies have demonstrated that vine-canes are rich in polyphenols [12,13,14,15,16,17] and could be used as a source of these bioactive compounds
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