Electrolyte Leakage as an Indicator of High-temperature Injury to Harvested Mature Green Tomatoes

Abstract

Newly harvested tomatoes are often exposed to short periods of high temperatures. To simulate harvest conditions, mature green (MG) tomatoes ( Lycopersicon esculentum Mill., cv. 908) were exposed to direct solar radiation until their mean temperatures became 45°, 50°, or 55°C. When fruit temperatures were > 50°, heat injury was obvious. Once exposed, tomatoes remained at these high temperatures for ≈ 1 hr, even after being transferred to shade. The interaction between high temperature and exposure time on tomato thermostability was studied in the laboratory. MG ‘908’ tomatoes were exposed to temperatures ranging from 25° to 65° for 30 to 180 min; the damage was then measured by determining the amount of electrolyte leakage. A mathematical model describing the interaction of temperature and time was used to predict the critical high temperature and exposure time. Critical exposure times calculated for ‘908’ tomatoes were 34, 105, and 166 min for exposure to 55°, 50°, and 45°, respectively. For practical field applications, this high-temperature stress may decrease the quality by causing the destruction of fruit cellular tissue and physiological disorders.