Fungal Population Dynamics in Ready-to-eat Salads During a Shelf-life in Italy

The aim of this work was to investigate the fungal population dynamics in ready-to-eat bagged samples of rocket (Diplotaxis spp.), lettuce baby leaf (Lactuca sativa L.) and “songino” (Valerianella olitoria L.) during a shelf-life, in order to evaluate the effects of the storage length and season of production on the spoilage processes. The incidence of toxigenic moulds was particularity studied in order to evaluate a potential production of mycotoxins and allergenic conidia. A total of 900 samples collected from 10 Italian trademarks were analyzed at the 2nd, 5th and 8th day after the packaging in the spring and summer. A very high number of fungi was found and a great variability of moulds and yeasts at the 1st day of sampling was observed. Regarding to season of production, any seasonal effect on the moulds and yeasts has been observed, but the moulds detected belonged to different species in relation to season. Regarding to storage length, the yeasts and moulds did not showed significant variations during a shelf-life. In relation to vegetable species, the lettuce resulted always less contaminated with respect to other salads, and the rocket presented 1-2 Log cfu/g of increasing in the level of moulds. Regarding to fungi species, the yeasts were significantly predominant respect to moulds. Finally, the toxigenic moulds Aspergillus flavus and Penicillium italicum were found in all the types of salad in the summer, and their growth during the storage at low temperature represented a potential hazard for the mycotoxins and allergenic conidia production in these commodities.