Response of Listeria monocytogenes-inoculated leafy salad vegetables following irradiation and refrigerated storage under modified atmosphere. Section 1. Radiation sensitivity and quality of fresh cut vegetables exposed to gamma irradiation

This section summarizes research on quality of irradiated vegetables. Thirteen fresh-cut (minimally processed) vegetables (broccoli (Brassica oleracea italica), cilantro (Coriandrum sativum), red cabbage (Brassica oleracea capitata), endive (Cichorium endivia), parsley (Petroselinum crispum), green and red leaf lettuce (L. sativa), Iceberg (Lactuca sativa var. capitata) and Romaine lettuce (Lactuca sativa), spinach (Spinacia oleracea), carrots (Daucus carota), green onions, (Allium cepa) and celery (Apium graveolens dulce) plus alfalfa sprouts (Medicago sativa) were gamma irradiated at doses up to 3 kGy at 0.5 kGy intervals. The samples were then stored in air at 4 deg. C for 14 days. At the beginning and end of 14 days, electrolyte leakage, visual quality, and sogginess were assessed. Results showed that electrolyte leakage of vegetables increased linearly with increasing radiation doses when measured immediately after irradiation. Radiation dose threshold, defined as the dose at which electrolyte leakage was significantly (P<0.05) increased, varied among vegetables, ranging from 2.44 kGy for broccoli to 0.60 kGy for carrots. Irradiation had no effect on visual quality on the day of irradiation. After 14 days of storage, the responses of individual vegetables to ionizing radiation varied greatly. Irradiation, especially at lower doses, improved visual quality, and reduced sogginess and electrolyte leakage of many vegetables. It appears that most tested vegetables can tolerate 0.6 kGy radiation based on appearance and electrolyte leakage measurements. The implication and limitation of the results are discussed. (author)