Effect of temperature and relative humidity on fresh commodity quality

Postharvest physiology of peaches and nectarines

Texture changes in ripening fruits influence consumer preference, fruit storability, transportability, shelf-life, and response to pathogen attack. Genetic regulatory factors as well as environmental conditions simultaneously affect texture changes in ripening fruit. Recent physiological and molecular studies provide insights into our knowledge and understanding of events and/or factors that contribute to changes in fruit texture, including softening and lignification. The roles of enzymes involved in modification and/or regulation of cell wall components as well as ethylene signaling components that play key roles in fruit textural changes during fruit ripening and storage will be presented and discussed. In addition, physical as well as chemical regulation of textural changes in ripening fruit will be explored.

Regulatory Mechanisms of Textural Changes in Ripening Fruits

Several sweet cherry (Prunus avium L.) cultivars were stored in air or modified- atmosphere packages (MAP) at 1 °C for 2 or 4 weeks, respectively. The new cultivars included 'Santina', 'Sumpaca Celeste', 'Sumnue Cristalina', 'Sumste Samba', 'Sandra Rose', 'Sumleta Sonata', and 'Skeena', and the standards were 'Lapins', 'Sweetheart', and 'Bing'. Fruit were rated for defects (stem browning, stem shrivel and fruit surface pitting), and fruit quality at harvest and after storage. Weight loss during storage was influenced by year, storage treatment, and cultivar. Stem shrivel, stem browning, and fruit surface pitting varied among cultivars and years. Generally, fruit stored in MAP had higher fruit firmness than at harvest or when stored in air. The respiration rate of fruit was lower in later than in earlier maturing cultivars, but respiration rate at harvest was not related to any of the quality measurements taken after storage. The sweet cherry breeding program at Agriculture and Agri-Food Canada at Summerland has introduced many cultivars that have been adopted by sweet cherry grow- ers around the world. New cultivars recently introduced from the program include 'Santina', 'Sumpaca Celeste', 'Sumnue Cristalina', 'Sumste Samba', 'Sandra Rose', 'Sumleta Sonata', and 'Skeena' (Kappel et al., 1998, 2000a, 2000b). They cover a range of maturities from 8 d before 'Van' to ≈15 d after 'Van', and all have large fruit size and good firmness. However, the postharvest quality and behavior of these new cultivars have not been determined. The flavor of sweet cherries is largely determined by sugar content and acidity. Dur- ing storage acidity changes more rapidly than does soluble solids (i.e., sugar) control (Drake and Fellman, 1987). Loss in flavor during modified-atmosphere (MA) storage is prima- rily associated with reduced acidity (Meheriuk et al., 1995). Cultivars may differ in either acidity at harvest or rate of change in acidity during storage. Fruit firmness is also a very important postharvest quality factor. Cultivars differ in susceptibility to postharvest softening (Brown and Bourne, 1988). Other quality traits that can be affected by storage are fruit surface pitting and stem quality (browning and shrivel); Looney et al. (1996) noted cultivar differences in both of these characteristics. Cherries have no starch reserves, there- fore maintenance of respiration relies prima-

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P.J. Sharkey

Papers

Effects of high-humidity storage on quality, decay and storage life of cherry, lemon and peach fruits