Effects of Defoliation on Phenolic Concentrations, Antioxidant and Antibacterial Activity of Grape Skin Extracts of the Varieties Blaufränkisch and Merlot (Vitis vinifera L.)

Abstract

Vitis vinifera L. has been highlighted by its many positive effects on human health, including antibacterial, anti-inflammatory and antioxidant activity due to its rich phytochemical content. Removing six basal leaves has great potential to influence the production of phytochemicals. The purpose of this study was to determine the impact of different terms of defoliation on the antioxidant and antibacterial activity of grape skin extracts of the Blaufränkisch and Merlot varieties. The total phenolic concentration, total and individual anthocyanin concentration, antioxidant activity and antibacterial activity on gram-positive and gram-negative human pathogens have been determined. The study was conducted on three treatments (control treatment without defoliation, defoliation immediately after bloom and defoliation before the start of the véraison phase). The results showed statistically significant enhancement of the total phenolic concentration as well as the antioxidant and antibacterial activity in both studied cultivars. Defoliation just after blooming was the preferable defoliation term in the Merlot variety for achieving the highest total anthocyanin concentration, antioxidant activity and significant increase of antibacterial activity against all four investigated bacteria. Defoliation before the start of the véraison phase was the preferable defoliation term for achieving the highest total anthocyanin concentration in the Blaufränkisch variety. In general, treatment of defoliation immediately after bloom was more beneficial compared with the defoliation before the start of the véraison phase.

Valorization of Winemaking By-Products as a Novel Source of Antibacterial Properties: New Strategies to Fight Antibiotic Resistance

“…Little thought is, however, given to its potential as a source of commercially valuable products [ 45 , 58 ]. The chemical composition of marc can be affected by environmental (climate, soil type) [ 25 , 29 , 59 ] and viticultural factors (fertilization, defoliation, grape variety, maturity, and harvest time) [ 59 , 60 ], as well as by grape processing techniques employed during winemaking [ 59 ]. Whereas red wine undergoes a fermentation process, the musts are removed before alcoholic fermentation in the other wine varieties.…”

Impact of Leaf Removal on Phenolics and Antioxidant Activity of Trebbiano Berries (Vitis vinifera L.)

“…Our results agree with the study by Radovanovic et al [ 29 ] in which early defoliation of vines resulted in a significant increase in total phenol concentration as well as in antioxidant activity compared to the control. Pavic et al [ 30 ] observed a similar trend in the grape skins of the Merlot variety following leaf removal just after blooming. It has been observed that the antioxidant capacity differs among phenols being expressed at different levels, making it difficult to differentiate the relative contribution of the various phenolics to the total antioxidant capacity of berries.…”

The Effect of Pre-Harvest Application of Pectic Oligosaccharides and Abscisic Acid on Technological Ripening and Anthocyanin Profile of ‘Syrah’ Must and Grapes Grown in a Warm Climate

“…The mean at-harvest total phenolics content in Syrah grapes was similar to those found in the dark blue-colored wine grapes cvs. Blaufränkisch and Merlot grown in temperate climate (Pavić et al, 2019), suggesting the adaptability of V. vinifera to maintain adequate levels of these relevant compounds even under suboptimal climate conditions. The preharvest application of elicitors to increase the content of phenolic compounds in grapes has shown contrasting results related to the species, cultivar, type of elicitor, and vintage (Sandhu et al, 2011;Ruiz-García et al, 2013;Gómez-Plaza et al, 2017).…”