Unravelling During Cold Storage and Shelf Life the Pathological and Physicochemical Characteristics of Postharvest Apples and Oranges Treated with Sodium Metabisulfite

Fruits are susceptible to a diverse range of postharvest rots that can reduce quality if preventive measures are not taken in time. In this study, samples of orange cv. 'Maltaise' and apple cvs. ‘Golden Delicious' and 'Richared' were sorted without infection or injury, treated or not with sodium metabisulfite (SMB), then placed in cold storage for 20, 42 or 59-61 days, followed by a shelf life of 6 or 15 days. The degree of fruit infection, weight loss and physicochemical characteristics were analyzed at each storage period. Our results indicate that adequate postharvest storage depends on the type of fruit, the duration of cold storage and shelf life. The heat map grouped 'Richared' apples close to its fresh state, without developing rot or perceptible weight loss for 60 days at low temperature (6°C) and 15 days of shelf life. These red apples performed better during storage than the “Golden”, especially in terms of storability and total flavonoids. Apples of 'Golden' showed better storage stability than 'Maltaise', which could be stored properly for up to 20 days at 6°C, followed by a 15-day shelf life, regardless of treatment with sodium metabisulfite. The longer the oranges were stored, the greater the risk of infection and the physicochemical properties, in this case flavonoids, decreased. The chemical criteria (TSS, pH) of apples and oranges were not affected by soaking in SMB, being similar to that of untreated fruit. However, treating fruit with SMB is regarded as unlikely due to its low effectiveness in preventing fruit decay during long-term storage. Cluster analysis showed that total polyphenols were linked to poor storability, while flavonoids, hardness and TSS were clustered with better storability. This suggests that flavonoids may be a more reliable indicator of storage suitability than total polyphenols.