Oxidations in grape berries are gaining major interest as they affect grape characteristics and quality. Considering berries, Reactive Oxygen Species are involved in the responses to both ripening process and stresses, including photooxidative sunburn. Redox metabolism involves a multitude of chemical and enzymatic reactions. In this study, four white grape cultivars were examined for natural ripening and photooxidative sunburn effects (obtained in artificial conditions) on berry pigmentation, chemical composition and enzymatic activity. The measured parameters included reflectance spectra, pigmentation (including berry browning), content of photosynthetic pigments, organic acid profiles, antioxidant activity, concentrations of antioxidants (total phenolics, ascorbic acid and reduced glutathione), enzymatic activities (guaiacol peroxidases, ascorbate peroxidase and catalase). The effects of the treatment (natural ripening and artificial photooxidative sunburn) on each considered parameter are described in the paper. Photooxidative sunburn strongly affected the contents of antioxidants and chlorophylls, increased the browning index and modulated the enzymatic activities investigated. Samples clearly clustered depending on the oxidation status. Furthermore, the PCA highlighted the similarities and differences in the responses to oxidative stress during ripening and photooxidative sunburn. PCA produced five functions with eigenvalues higher than 1, representing 87.03% of the total variability. In particular, the scores of the function 1 discriminated the samples based on the oxidation status, while the function 2 separated the samples based on the sampling date, representing the physiological responses characteristic of ripening. Our work sheds light on this topic, and will allow a more conscious vineyard management, thus supporting the agricultural adaptation to climate changes.

葡萄浆果中的氧化会影响葡萄的特性和品质，因此引起人们的极大关注。考虑到浆果，活性氧物种参与了对成熟过程和压力（包括光氧化性晒伤）的响应。氧化还原代谢涉及多种化学和酶促反应。在这项研究中，研究了四个白葡萄品种对浆果色素沉着，化学组成和酶活性的自然成熟和光氧化性晒伤（在人工条件下获得）的影响。测得的参数包括反射光谱，色素沉着（包括浆果褐变），光合色素含量，有机酸谱，抗氧化剂活性，抗氧化剂浓度（总酚，抗坏血酸和还原型谷胱甘肽），酶促活性（愈创木酚过氧化物酶，抗坏血酸过氧化物酶和过氧化氢酶）。本文介绍了处理（自然成熟和人工光氧化晒伤）对每个考虑参数的影响。光氧化性晒伤强烈影响抗氧化剂和叶绿素的含量，增加了褐变指数并调节了所研究的酶活性。样品根据氧化状态明显聚集。此外，PCA强调了成熟和光氧化性晒伤过程中对氧化应激反应的异同。PCA产生了五个特征值高于1的函数，占总变异性的87.03％。特别是，功能1的得分基于氧化状态来区分样品，而功能2的得分则基于采样日期来区分样品，代表成熟的生理反应。我们的工作阐明了这一主题，并将使葡萄园管理更加自觉，从而支持农业适应气候变化。