Table grapes suffer water loss, stem browning during cooling delays.
Crisosto, C. H., Smilanick, J. L. and Dokoozlian, N. K.
California Agriculture, 2001. Vol.55, No.1. p. 39-42.
2001
บทคัดย่อ
The relationship between cluster water loss and stem browning was studied in 5 table grape cultivars (Perlette, Thompson Seedless, Flame Seedless, Fantasy Seedless and Redglobe). The magnitude of cluster water loss occurring during commercial table grape harvesting operations in California, USA [date not given] was also evaluated. Clusters of all table grape cultivars, harvested at commercial maturity, were forced to lose 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0% water by weight, and were then placed in cold storage at 32 deg F, 95% relative humidity, and 12 fpm air velocity. Visual stem browning symptoms were significantly related to cluster water loss. Clusters showing severe stem browning symptoms lost more water than clusters with moderate and slight stem browning symptoms. In general, Perlette, Flame Seedless and Thompson Seedless showed more advanced stem browning symptoms than the other cultivars at the same percentage cluster water loss. Cultivar genotype also influenced the length of time it took for stem browning to develop during storage. Thompson Seedless and Flame Seedless clusters that lost 2.0% water during cooling delay took 2 and 4 days of cold storage, respectively, to exhibit cap stem browning. Development of visual stem browning symptoms was also significantly related to stem water loss. Stems with slight browning symptoms had lost less of their harvest fresh weight than stems with moderate and severe symptoms. Perlette, Flame Seedless and Thompson Seedless stems had to lose 16.5, 14.4 and 15.1%, respectively, of their water content before showing cap stem dehydration symptoms, while Fantasy Seedless and Redglobe stems had to lose more than 20% of their water content. Redglobe had moderate to severe stem browning symptoms after losing 36% of their water content, while Perlette, Flame Seedless, Thompson Seedless and Fantasy Seedless had moderate to severe browning when they lost more than 25% of their water content. Postharvest water loss from Flame Seedless was influenced by temperature and length of the cooling delay. After an 8-h field delay, Flame Seedless grape water loss reached 1.38%, while a minimum of 0.19% and a maximum of 0.92% water loss were measured after a 4-h field delay. Box materials and cluster bags influenced the amount of water lost during the cooling delay period, where water loss was greatest in corrugated box, followed by TKV (for technical Kraft Veneer) and foam boxes.