The Evolution of Total Phenolic Compounds and Antioxidant Activities during Ripening of Grapes (Vitis vinifera L., cv. Tempranillo) Grown in Semiarid Region: Effects of Cluster Thinning and Water Deficit

Abstract

A study was made of how water status (rainfed vs. irrigated) and crop load (no cluster thinning vs. cluster thinning) can together affect the grapes of Vitis vinifera cv. Tempranillo vines growing in a semiarid zone of Extremadura (Spain). The grapes were monitored at different stages of ripening, measuring the peroxidase (POX) and superoxide dismutase (SOD) antioxidant activities and the phenolic content (flavonoids and phenylpropanoids), together with other parameters. The irrigation regime was adjusted to provide 100% of crop evapotranspiration (ETc). The findings confirmed previous results that both thinning and water deficit advance ripening, while irrigation and high crop load (no thinning) lengthen the growth cycle. The SOD activity remained practically constant throughout ripening in the thinned treatments and was always lower than in the unthinned treatments, an aspect which could have been the cause of the observed greater level of lipid peroxidation in the water deficit, thinned treatment. The nonspecific peroxidase activity was very low, especially in the thinned treatments. The effect of thinning was enhanced when combined with water deficit, inducing increases in phenylpropanoids and, above all, flavonoids at the harvest stage of ripening, while leaving the polyphenol oxidase activity (PPO) unaffected.

Effects of Production Region, Production Systems and Grape Type/Variety on Nutritional Quality Parameters of Table Grapes; Results from a UK Retail Survey

“…The use of gibberellic acid (GA 3 ) to increase fruit yield was reported to decrease total phenolic, flavonoid and antioxidant activity in ‘Muscat’ grape berry skin and flesh, although levels in leaf, stem and tendril tissue increased [ 31 ]. Iincreasing high yield levels by contrasting levels of winter pruning or cluster thinning were also reported to result in lower total phenolic, anthocyanin and/or antioxidant activity in table grapes, and wine [ 30 , 32 , 33 ]. Garrido et al [ 33 ] also reported that the increase in phenylpropanoids and flavonoids concentrations effect resulting from cluster thinning/lower yields was greater in non-irrigated than irrigated grapes [ 11 ].…”

“…Iincreasing high yield levels by contrasting levels of winter pruning or cluster thinning were also reported to result in lower total phenolic, anthocyanin and/or antioxidant activity in table grapes, and wine [ 30 , 32 , 33 ]. Garrido et al [ 33 ] also reported that the increase in phenylpropanoids and flavonoids concentrations effect resulting from cluster thinning/lower yields was greater in non-irrigated than irrigated grapes [ 11 ].…”

Potential of Grape Wastes as a Natural Source of Bioactive Compounds

“…Many factors can influence the composition and contents of bioactive compounds in fruits, like genotype, growth environment (soil, water, sunlight, etc.) and maturity, among which genotype usually has the greatest impact [ 24 , 25 , 26 ]. Thus, we could hypothesize that grapes with diverse genotypes should have different composition and contents of bioactive compounds, so it is worthwhile to assess the antioxidant capacities while determining the phenolic and flavonoid contents of peels and seeds from different grape varieties.…”

Study of the Cluster Thinning Grape as a Source of Phenolic Compounds and Evaluation of Its Antioxidant Potential

“…Cluster thinning influences the yield reduction, advances grape maturity, improves the phenolic content of the grape, and influences the volatile profile of wine. In addition, this technique tends to diminish acidity and increase soluble solids [ 27 , 28 , 29 , 30 , 31 ]. Therefore, despite the economic impact of thinning, this process is a very common activity in some warm-climate producer areas.…”