Short‐term anoxia treatment maintains tissue energy levels and membrane integrity and inhibits browning of harvested litchi fruit

Pericarp browning is the main limitation to the postharvest storage, handling and marketing life of litchi fruit. Pre‐storage treatment with pure N₂ gas is potentially effective in reducing skin browning and maintaining eating quality of litchis. To better understand inhibition of pericarp browning by a short period of anoxia, adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) levels, adenylate energy charge and membrane permeability were investigated. Litchi fruit were exposed to pure N₂ gas for 6 h and then kept in closed but vented containers for 6 days in the dark at 25 °C and 95–100% relative humidity. Changes in the mentioned fruit physiology and biochemistry parameters and in browning index were measured. ATP concentration and adenylate energy charge decreased rapidly and membrane permeability (relative leakage) increased gradually during storage. Fruit exposed to N₂ gas exhibited higher concentrations of ATP, ADP and AMP and adenylate energy charge levels, and lower levels of browning index and membrane permeability, compared to control (non‐N₂‐treated) fruit. Greater differences in ATP and ADP concentrations and adenylate energy charge levels of pericarp tissues between N₂‐treated and control fruit were more manifest after 4 and 6 days of storage, in association with significant differences at the 5% level in the pericarp browning index. It is suggested that pre‐storage anoxia treatment maintains membrane integrity of pericarp tissues, with high ATP and ADP concentrations and high adenylate energy charge levels. Thus, the loss of cellular compartmentalization (mixing of enzymes and substrates) that leads to enzymatic browning of litchi fruit pericarp is delayed. Copyright © 2007 Society of Chemical Industry