Study radiation sensitivities of fresh and fresh-cut vegetables under air and modified atmosphere packaging, and explore means to minimize radiation-induced injury.
Recent research indicated that fresh-cut Iceberg lettuce is relatively resistant to irradiation. Even though there have been studies regarding quality of irradiated whole and cut lettuce, there is no study that directly compares radiation sensitivity of whole lettuce with that of fresh-cut produce. Iceberg lettuce is the number one vegetable in terms of total productions among leafy greens, sold either as whole or as fresh-cut in mixed salads. While the whole head lettuce is either wrapped with films or not wrapped, fresh-cut lettuce is normally packed in modified atmosphere packaging that allows the accumulation of low oxygen and high carbon dioxide to inhibit tissue browning. Research will be conducted to study the radiation sensitivity of whole lettuce. The lettuce will be gamma irradiated with low and middle range irradiation and stored for 2 weeks at 4C. Both external and external appearance and injury (discoloration, spotting, etc) caused by irradiation will be evaluated. The firmness of the head lettuce will also be evaluated. The same whole lettuce will also be cut into pieces, (washed using 100 ppm chlorine), and then packaged in either air or modified atmosphere film bags. Modified atmosphere will be established from respiration metabolism of cut lettuce (passive MAP). Cut lettuce quality (appearance, color, texture) will be measured every week during 14-days storage at 4°C. Details of the experimental plan can be found in Appendix A