MANAGING CHILLING INJURY IN VEGETABLES

Abstract

Common vegetables that are susceptible to chilling injury include asparagus, beans, cucumbers, eggplants, ginger, jicama, okra, peppers, potatoes, pumpkins, sweet potatoes, tamarillos, tomatoes, and zucchini squashes. Most of the susceptible crops are either fruit vegetables or root vegetables. Chilling injury symptoms vary depending on the commodity, but generally manifest as pitting, discoloration, internal breakdown, and decay. Images from nuclear magnetic resonance revealed that signals on the peripheral of cells in chilled zucchini tissues were much more intense than those in non-chilled tissues, indicating that cell membranes were damaged by chilling which leads to the increased permeability and solute leakage. Several postharvest techniques have been demonstrated to be effective in managing chilling injury in vegetables, including temperature preconditioning, intermittent warming, high oxygen atmosphere, heat treatment, modified atmosphere packaging, and treatment with growth regulators or natural products as well as harvesting at proper maturity. Treatment with certain naturally occurring compounds such as methyl jasmonate (MJ) or methyl salicylate (MS) increased activities of alternative oxidase (AOX) in the respiratory pathway of sweet pepper and enhanced amounts of high and low molecular weight heat shock proteins (HSP) and pathogenesis-related proteins (PRP) in tomatoes. Temperature preconditioning treatment elevated antioxidant content and antioxidant enzyme activities, and augmented s-adenosylmethionine (SAM) decarboxylase activities and increased the levels of spermidine and spermine in zucchini squash. These defense responses induced by these treatments might be part of the mechanisms that protected and prevented tissues from chilling injury. Promising techniques and new methods such as genetic engineering and transgenic skill need to be exploited for better management of chilling injury.