The effects of ethanol treatment on the metabolism, shelf-life and quality of stored tomatoes at different maturities and temperatures

Abstract

The objective of this research was to investigate the effects of ethanol treatment on the metabolism, shelf-life and quality of stored tomatoes at different maturities and at two temperatures. The tomatoes harvested at 2 maturity stages (mature green stage 3 and 4 and breaker) were exposed to ethanol vapour (2 ml of absolute ethanol per kg of fruit) for six hours. The tomatoes were then stored at two temperatures (20°C for 21 days and 5°C for 14 days followed by 7 days at 20°C). During storage, colour, ethylene and CO₂ were measured every 2 or 3 days. Firmness, pH, titratable acidity, soluble solids, ethanol concentration in juice and ethanol released into the atmosphere were measured every 7 days.

Pre-treatment of tomatoes for 6 hours exposure to ethanol vapour at room temperature inhibited the ripening of tomato fruit during storage as indicated by the reduced ethylene and CO₂ production, the rate of red colour development and green colour reduction, and softening of the tissue. The largest inhibition occurred at 5°C compared to 20°C and was greater in mature green tomatoes relative to breaker fruit. No symptoms of chilling injury (CI) were observed in 'Tauto' cultivar tomato which were stored at 5°C for 14 days even after having been returned to 20°C for 1 week.

The results suggest that ethanol can be used as a cheap, environmentally acceptable method to increase the shelf-life of tomato.