Study of Unpicked Grapes Valorization: A Natural Source of Polyphenolic Compounds and Evaluation of Their Antioxidant Capacity

Edurne Elejalde, María Carmen Villarán, Iratxe Lopez- de-Armentia, Daniel Ramón, Raquel Murillo and Rosa María Alonso
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Edurne Elejalde: TECNALIA, Basque Research and Technology Alliance (BRTA), Parque Tecnológico de Álava, c/Leonardo Da Vinci 11, 01510 Miñano, Álava, Spain
María Carmen Villarán: TECNALIA, Basque Research and Technology Alliance (BRTA), Parque Tecnológico de Álava, c/Leonardo Da Vinci 11, 01510 Miñano, Álava, Spain
Iratxe Lopez- de-Armentia: TECNALIA, Basque Research and Technology Alliance (BRTA), Parque Tecnológico de Álava, c/Leonardo Da Vinci 11, 01510 Miñano, Álava, Spain
Daniel Ramón: TECNALIA, Basque Research and Technology Alliance (BRTA), Parque Tecnológico de Álava, c/Leonardo Da Vinci 11, 01510 Miñano, Álava, Spain
Raquel Murillo: TECNALIA, Basque Research and Technology Alliance (BRTA), Parque Tecnológico de Álava, c/Leonardo Da Vinci 11, 01510 Miñano, Álava, Spain
Rosa María Alonso: Analytical Chemistry Department, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Vizcaya, Spain

Resources, 2022, vol. 11, issue 3, 1-14

Abstract: Every year great amounts of high-quality wine grapes are left on the vine unpicked, and consequently lost, to control the overproduction in wine areas with limited appellation production yield. In the context of circular bioeconomy, the valorization of these grapes as a potential source of natural antioxidants is of great interest. The study carried out is focused on the polyphenolic profile characterization of different unpicked grape varieties using the ultrasound-assisted extraction technique to extract the polyphenolic fractions. Moreover, the evaluation of the antioxidant capacity by several assays was carried out: oxygen radical absorbance capacity (ORAC), stability of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), ferric reducing antioxidant capacity (FRAP), cupric reducing antioxidant capacity (CUPRAC) and stability of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS) assays. The results showed a strong relationship between total phenolic content and hydroxycinnamic acids (R 2 = 0.9088) followed by flavan-3-ols (R 2 = 0.8792) and tannins (R 2 = 0.7705). The antioxidant capacity of the grapes was dependent on the total phenolic content. These results supply new information for a better understanding of the importance of giving an added value to the unpicked grapes due to their high content of polyphenols. These findings help the wine sector to consider the valorization of the unpicked grapes, classified as wastes, as an interesting source of natural antioxidants to be used as food supplements and with potential applications in the pharmaceutical industry.

Keywords: unpicked grape; polyphenols; antioxidant capacity; ultrasound-assisted extraction; grape valorization (search for similar items in EconPapers)
JEL-codes: Q1 Q2 Q3 Q4 Q5 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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