Improvement of hygienic quality of fresh, pre-cut, ready-to-eat vegetables using gamma irradiation

In the last years, the consumer trends in Argentina have increased for fresh-like products and with reduced or no chemical preservatives. Minimally processed foods like fresh pre-cut vegetables and fruits have limited shelf life and mainly rely on Good Manufacturing Practices for preservation and safety. The incidence of outbreaks declared for fresh vegetables in the last 10 years in Argentina is 3% (54 affected). In this project, minimally processed conventional and organic vegetables of the local market were studied: conventional and organic chicory (Chicorium endive), organic rugola (Eruca sativa Mill), soy sprouts (Glycine max), alfalfa sprouts (Medicago sativa) and a mixed salad composed of cherry tomatoes (Solanum lycopersicum), carrots (Daucus carota L.), lettuce (Lactuca sativa) and cabbage (Brassica oleracea). The analyses were carried out in order to determine the irradiation process needed to ensure the hygienic quality of these kinds of products, with minimum organoleptic modification. The investigated microorganisms were Listeria monocytogenes ATCC 15313, Salmonella Enteritidis ATCC 13076 and Staphylococcus aureus ATCC 6538P. From the radiation resistance studies of the pathogenic bacteria, Listeria monocytogenes was the most radiation resistant microorganism in conventional and organic chicory, organic rugola, soy sprouts, alfalfa sprouts and Staphylococcus aureus for the mixed salad. The minimum disinfection doses proposed for these products are 1.2 kGy for conventional chicory and mixed salad, 1.3 kGy for organic chicory, 1.4 kGy for organic rucula, and about 2.0 kGy for soy and alfalfa sprouts. The disinfection doses were effective in the conventional products even during storage time and they did not affect the sensorial properties. The main objective of this work, to find the adequate dose to assure the hygienic quality of fresh pre-cut vegetables, was achieved with acceptable organoleptic characteristics. This work contributes with information about these kinds of products, which have quite recently appeared in the market. It was noted that there was a lack of information about their production and specific controls. Minimally processed vegetables require legislation stricter than the existing one for fresh vegetables. Although producers apply good manufacturing practices, sometimes this was not enough to ensure the absence of pathogens in these products. (author)