Prestorage Heat Treatment to Inhibit Chilling Injury and Delay Ripening in Tomato Fruits

Abstract

The research had two specific goals; (1) to develop and optimize a postharvest heat treatment and characterize the response of tomato to the heat and subsequent cold storage, and (2) to investigate the involvement of heat shock proteins (HSP) in resistance to chilling injury. For the first goal we have investigated many time-temperature treatments using dry heat and found that 48 h at 38oC is optimum for Israeli cultivars, while 48 h at 42oC worked better for American cultivars in preventing chilling injury. We have also compared hot water to hot air and found hot water to be effective, but less so than hot air. Membrane lipid composition in relation to chilling injury was investigated after hot water and hot air treatments. Investigation of fruit ripening found that mRNAs of ripening-related genes were inhibited by high temperature, but recovered during the subsequent storage period and allowed normal ripening to proceed. Sensory studies showed no difference in the taste of heated or nonheated fruit. Following the production of HSP in heated and stored fruit allowed us to determine that during low temperature storage the HSP remained present in the fruit tissue, and their presence was correlated with resistance to chilling injury. HSP clones have been isolated by both differential screening of a cDNA library of heated and chilled tomatoes (Israel) and by mRNA differential display (United States). These clones are being characterized.