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Grape juice is known as a relevant source of compounds with antioxidant potential, which are accumulated during grape growth and development. As these compounds come from specialized metabolism, postharvest stressors may increase the synthesis and accumulation of these metabolites. Thus, UV-C radiation (65.6 J m−2) was applied to ‘Concord’ grapes (from vineyards grown in conventional and organic systems), after harvest. The following dependent variables were analyzed: pH, total titratable acidity, total soluble solids, ratio, angle hue, L, a, b, ΔE, total phenolic compounds, total anthocyanins, malvidin, delphinidin, peonidin, cyanidin, epicatechin, quercetin, kaempferol, trans-resveratrol, and cis-resveratrol. The UV-C treatment did not interfere with the basic physicochemical composition but resulted in juices with a more intense color. Juice from grapes grown in an organic system and subjected to postharvest UV-C treatment had also an increase in the levels of phenolic compounds, which was not observed in juice from grapes grown in a conventional system and subjected to the same treatment. Thus, responses to postharvest UV-C radiation depend on cultivation conditions.

Strawberry is one of the most popular fruits because of its shape, color and taste, and the presence of antioxidant compounds. Because severe abiotic stresses result in detrimental consequences to plant growth, the effect of cultivating under mild stress conditions has rarely been investigated. Therefore, we evaluated the effect of mild salt stress on yield and quality of strawberry fruit. Mild salt stress did not affect yield. The lower level of mild salt stress evaluated showed increased vegetative growth (24%), higher photosynthetic effectiveness, and increased activity of phenoloxidase (22%) and polyphenoloxidase (33%), as well as the accumulation of sucrose (5%) and anthocyanins (60%) in the fruit, compared to non-stressed plants. The higher level of mild salt stress increased root growth (30%), the activity of phenylalanine ammonia lyase (68%), and the accumulation of total phenolic compounds (14%), and total antioxidant activity (13%) in the fruit, compared to non-stressed plants. The only phenolic compound improved in these treatments was (+)- catechins. Both levels of salt stress affected the expression of genes involved in the phenylpropanoid and flavonoid pathways, cell wall disassembly and abscisic acid-related genes. Therefore, mild salt stress improves strawberry fruit quality.