Effect of preharvest chitosan-g-salicylic acid treatment on postharvest table grape quality, shelf life, and resistance to Botrytis cinerea-induced spoilage

Sulfur dioxide fumigation used for many years to preserve quality and extend shelf life of table grapes is now under scrutiny for their adverse effects on food safety and the environment. Here, three new preharvest treatments, chitosan, chitosan plus salicylic acid, and chitosan-g-salicylic acid (CTS-g-SA), were evaluated for their effects on decay incidence, grape quality, and shelf life during cold storage. Of the three preharvest treatments tested, CTS-g-SA treatment exhibited enhanced activities of phenylalanine ammonia lyase, chitinase, and beta-1, 3-glucanase, while also promoting accumulation of phenolic compounds and greater resistance to Botrytis cinerea decay. Moreover, CTS-g-SA application significantly decreased respiration rate, weight loss, and decay incidence, while improving levels of total soluble solids, titratable acidity, and sensory attributes of table grapes during storage. Coating fruits with CTS-g-SA has potential as a preharvest tool to enhance the quality and extend the postharvest shelf life of table grapes. This treatment is a highly effective and safer alternative to treatments currently in use.