Use of Irradiation to Ensure Microbial Safety of Fresh-Cut Green Beans Sold In Egyptian Supermarkets

Thirty samples of fresh-cut green beans were collected from different local supermarkets. They were tested for their microbiological quality. Total aerobic plate count (TAPC) of these samples ranged from >105 to 108 cfu/g; and total yeasts and moulds ranged from 102 to 105 cfu/g. All tested fresh-cut green beans samples were contaminated with E. coli. Only 6 samples were free from Enterococcus faecalis, the other 24 (80%) samples contained Ent. faecalis in the range of 102 to 104 cfu/g. Staphylococcus aureus was found in 20 samples (66.6 %) at level of 102 to 104 cfu/g. Aeromonas hydrophila was found in 22 (73.3 %) samples in the range of 102 to 103 cfu/g. All tested fresh cut green beans samples were free from Listeria monocytogenes and Salmonella spp. The D10-values of the isolated pathogenic bacteria (Ent. faecalis, Staph. aureus, E. coli and A. hydrophila) in fresh-cut green beans were found to be 0.58, 0.42, 0.23 and 0.11, respectively. Fresh-cut green beans samples were irradiated at 1.5 and 3.0 kGy, and then stored at refrigeration temperature (4 degree C ± 1). Generally, these radiation doses greatly reduced all microbial counts of fresh-cut green beans. The percentage of reduction reached 97.07 and 99.88 in TAPC. Irradiation dose of 1.5 kGy was enough for complete elimination of E. coli and A. hydrophila but was not sufficient for elimination of Ent. faecalis, and Staph. aureus. Irradiation dose of 3.0 kGy completely eliminated Ent. faecalis, and Staph. aureus present. This irradiation dose had no effect on sensorial quality attributes of fresh-cut green beans samples and extended the shelf-life to 15 days against only 5 days for unirradiated samples