Postharvest Treatment Effects on ‘Somerset Seedless’ Cold-Hardy Table Grapes

Abstract

Limited amount of information is available for cold-hardy table grape postharvest storage and strategies to extend the storage time. ‘Somerset Seedless’ is a cold-hardy table grape with a potential market for the Upper Midwest and Northern Great Plains. Postharvest treatments were assessed as a possible route to increase cold-hardy table grape shelf-life. In this study, a 1.4% chitosan postharvest treatment was tested on ‘Somerset Seedless’ grapes through 7 weeks of storage with temperature 1–4°C, humidity ≥90%. The effects were compared to two controls: one was diH2O, and the other one was acetic acid. The assessment included grape appearance traits (rachis, decay, mold, scattering, and splitting), physiochemical properties (TSS, pH and total acidity), antioxidant activity, as well as total phenolics and flavonoid content. In general, 1.4% chitosan, 1% acetic acid, and diH2O had a large impact on grape appearance during storage with limited impact on chemistry. Throughout 7 weeks of storage, no significant differences were observed in grape physiochemical and phytochemical changes. Chitosan performed the best for ‘Somerset Seedless’ postharvest storage in regard to the low rate of visible damage. Although acetic acid had similarly positive effects on mold control as chitosan treatment, it caused the highest split rate after 1 week and the highest shatter rate after 5 weeks of storage. Chitosan treated ‘Somerset Seedless’ still met the USDA standard of table grapes after 5 weeks. This study suggests chitosan postharvest treatments may have applications for enhancing the shelf-life of cold-hardy table grapes.

Keywords

• ‘Somerset seedless’
• chitosan
• acetic acid
• postharvest storage
• cold-hardy grape