Effect of Gamma Irradiation on Microbial Quality of Minimally Processed Product in Tunisia: A Case of Ready to Eat Salad

Abstract

The use of gamma irradiation in food safety management as a tool to improve the microbiological quality of food products. Minimally processed product may contain a large number of spoilage microorganisms that constitute a potential health risk. In this study, raw carrot samples and fresh-cut products after each processing steps: water chlorination, peeling process and citric acid treatment were analyzed for the total aerobic plate count, Staphylococcus spp., yeasts and molds. Ready to eat products were also analyzed for these selective pathogens. The freshly packaged carrot salads were irradiated at various doses (0.5, 1.0, 2.0 kGy) and analyzed during 15 days storage period. The obtained results showed that raw carrots were highly contaminated by total aerobic plate count (7.23 Log10/25g), Staphylococcus spp. (3.77 Log10/25g), yeasts (5.62 Log10/25g) and molds (5.54 Log10/25g). Washing treatment and peeling process, were able to reduce the concentration of total aerobic plate count by 2.23 Log10 and to remove Staphylococcus spp. and molds. The mean concentrations of total aerobic plate count, Staphylococcus spp. yeasts and molds were 4.87, 2.08, 7.47 and 2 Log10/25g respectively for packaged salads. These results suggest that the contamination of carrot salads might occur through chain transformation. Regarding gamma irradiation effect, an optimal dose of 2kGy offered a pathogen-free, hygienic product in comparison with controls. Furthermore it increased shelf-life by 4 to 9 days at refrigeration temperature. The validity of the processing treatment at 2kGy was challenged by artificially inoculating Staphylococcus aureus in the product.