Effects of 1-MCP on oxidative parameters and quality in 'Pearl' guava (Psidium guajava']java L.) fruit

Guava (Psidium guajava L. 'Pearl') fruit were harvested at approx. the 80% mature stage. Fruit were exposed to 1.0 mu l l(-1) 1-methylcyclopropene (1-MCP) gaseous vapour for 12 h in a closed chamber maintained at 25 degrees C, stored at 28 degrees C and 60 - 65% relative humidity (RH) for 15 d, then assessed for their physiological and quality characteristics. The results showed that 1-MCP treatment delayed any increase in the incidence of decay, weight loss, and malondialdehyde (MDA) content. 1-MCP treatment had a positive effect on the retention of skin colour and on the firmness of guava fruit. Meanwhile, 1-MCP treatment maintained a higher vitamin C content and a lower soluble solids content, but titratable acidity was not affected by 1-MCP treatment. Moreover, 1-MCP treatment increased the activities of superoxide dismutase, catalase, and peroxidase, while reducing the activity of polyphenol oxidase. These results suggest that 1-MCP could delay the ripening process, maintain quality, and increase the anti-oxidant capacity of guava fruit stored at 28 degrees C.