Physiological, physico-chemical, and microbiological responses of ready-to-eat salad vegetable mix to 1-methylcyclopropene (1-MCP) post-cutting treatment

The effect of 1-MCP post-cutting treatment on the physiological, physico-chemical, and microbiological responses of ready-to-eat salad vegetable mix (RTE-SVM) was determined. In Study I, headspace gas analyses (oxygen, carbon dioxide, and ethylene) and visual evaluation (visual quality rating, lettuce wilting and yellowing, carrots discoloration, and cucumber water-soaking) were performed. Minimally-processed lettuce (Corelle, Romaine, and Iceberg varieties), Japanese cucumber, and carrots were prepared and packed in PET trays which were then sealed with PVC cling wrap film. 1-MCP gas injected in the packs to have a final concentration of 1ppm and 3ppm inside the RTE-SVM packs. The packs were stored in a cold room (5-8 deg C) until they became unacceptable as a whole, but the shelf life and limit marketability of the packs were set when the packs reach an average of VQR of 6 (Fair, moderate defects). It was found that the RTE-SVM prepared with Corelle lettuce and treated with 3ppm 1-MCP had the best response to the treatment, having the highest average VQR, lowest incidence of Corelle lettuce wilting and yellowing and carrots discoloration when treated with 3ppm 1-MCP. Furthermore, the RTE-SVM prepared with Corelle lettuce can be stored at 5-8 deg C for eight days before reaching a VQR of 6. With this information, the packs were prepared with Corelle lettuce, treated with 3ppm 1-MCP, and stored at 5-8 deg C for eight days to determine the physico-chemical and microbiological responses of the packs to the treatment (Study II). It was found out that 1-MCP treatment had no significant effect on pH, %TA, and vitamin C of the cucumber, as well as on the vitamin C content of the lettuce. On the other hand, 1-MCP treatment was found to be effective in reducing the growth of coliform bacteria towards the end of storage. Overall, 1-MCP post-cutting treatment had positive effects on the visual quality, but did not exhibit dramatic effects on the other storage quality (physiological responses, pH, %TA, vitamin C. and general aerobic bacteria and yeast and mold growth) of the RTE-SVM packs.