Physicochemical Changes and Antioxidant Metabolism of Actinidia arguta Fruit (Kiwiberry) Under Various Cold-Storage Conditions

<i>Actinidia arguta</i> (kiwiberry) is a fruit with significant health benefits, and research continues to identify factors that enhance its storability while maintaining quality. Special attention is given to antioxidant metabolism and total antioxidant activity. In this study, four cold-storage conditions were tested: normal air, normal air with ozone, modified atmosphere, and controlled atmosphere. In each case, the fruit was either pre-cooled before storage or not. The aim was to identify conditions most favorable to preserving internal and external fruit quality over time. Taking into account most of the basic fruit physicochemical traits tested, it can be assumed that for up to 30 days of storage, each storage method can be useful to store <i>A. arguta</i> fruit. After this period, the fruit stored in a controlled and then modified atmosphere retained the highest and acceptable firmness. Changes in antioxidant content are more complex and depend on the type of compound, storage time, and fruit post-harvest treatment. During the 50-day storage period, marked fluctuations in ascorbate, glutathione, and L-cysteine levels were observed at 10-day intervals. Phenolic content increased initially (after 10 days) and then stabilized. Among the methods used, ozonation led to a relative stabilization or increase in antioxidant content. This method, like the cooling procedure, requires further detailed research to determine its suitability for the species/variety being tested. Changes in antiradical activity were reaction-mechanism-dependent. The activity based on single electron transfer consistently decreased, while that based on hydrogen atom transfer was more stable overall. Contrary to this, the pro-oxidative Fe(II) chelating agent appeared during storage. The health-promoting properties of stored fruit may fluctuate due to antioxidant involvement in adaptation to storage conditions and uneven ripening, which remains a challenge both at harvest and during storage. Any of the three alternatives to cold storage in CA (NA, NA+O, MA) proved beneficial in short-term storage. However, MA has proven to be a similarly effective long-term storage method to CA in terms of the physicochemical quality of <i>A. arguta</i> fruit.