Polyphenol oxidase activity, color changes, and dehydration in table graperachis during development and storage as affected by N-(2-chloro-4-pyridyl)-N-phenylurea

Flame Seedless grapes were sprayed with N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU) at 0, 2.5, and 5.0 ppm to develop rachis resistant to browning and dehydration. Rachis polyphenol oxidase (PPO) activity was determined during cluster development. Cluster components were weighed at commercial (CM), a nd physiological maturity (PM). PPO activity, rachis color changes (L* and a*), and cluster weight loss were evaluated at 0 degreesC for 8, 16, 32, an d 56 days. CPPU-treated rachis had a decrease of 36% in PPO activity and a week delay in peak activity. At PM, dry weight of CPPU-treated rachis incre ased by 3 g. Postharvest rachis PPO activity declined with CPPU application , and color changes followed the same pattern for CM and PM. After 32 days of storage, L* and a* in lateral branches were significantly superior in CP PU treatments. Weight losses below 2.1% were significantly lowest in CPPU-t reated clusters for 16 days of storage regardless of cluster maturity.