Table grapes suffer water loss, stem browning during cooling delays

The water loss in table grapes that occurs during postharvest handling can lead to stem browning, berry shatter, and wilting and shriveling of the fruit. Critical grape cluster water-loss threshold values for stem browning were determined for Perlette, Thompson Seedless, Flame Seedless, Fantasy Seedless and Redglobe table grape cultivars. Fantasy Seedless and Redglobe withstood higher levels of stem water loss than Perlette, Flame Seedless and Thompson Seedless before expressing moderate to severe stem browning. Our survey of potential cluster water loss during harvesting operations indicated that a short cooling delay at high air temperatures contributed to stem browning. These low critical cluster water-loss threshold values combined with the high level of water loss measured during harvesting operations illustrate the need to minimize cooling delays and the importance of developing a technique to reduce cluster water loss during harvest and/or postharvest handling. The use of cluster bags and foam boxes reduced grape cluster water loss during harvest operations.