Research on mesophilic aerobic microorganisms and Enterobacteriaceae in cultivated and commercialized Agaricus bisporus.

Background: Production and consumption of fresh mushrooms reached high levels in recent years but only a few data regarding microbiological quality of these products are available, although their potential microbial load is expected to be high. EU and Italian legislation have not set a limit on microbial counts in these products and label information is often unclear. This study investigates the microbial quality of samples of fresh cultivated mushrooms sold in Tuscany so that both food business operators and legislators can obtain data about potential microbial risk for consumers and debate about the opportunity of realizing an update on fresh mushrooms labels that should include information to protect consumers' health.

Study Design: This study reports the microbial load in samples of cultivated and commercialized Agaricus bisporus. Samples were obtained from different shops in Florence, chosen among those products whose labels did not indicate how the product should be consumed.

Methods: From March through May 2014, 20 couples of samples of A. bisporus were acquired in Florence. Microbiological analysis included the quantification of the microbial counts for mesophilic aerobic microorganisms and Enterobacteriaceae, as indicators of hygienic practices during cultivation and manufacturing. The analyses were carried out at two subsequent stages: one immediately (T0) and one at the end of the shelf life (T1), i.e. close to the expiry date stated on the label.

Results: The high microbial load observed exceeds the reference values set as acceptable for raw foods in Tuscany and is worse than the ones reported in other studies on this subject. The results are particularly alarming in light of the fact that A. bisporus is usually consumed raw and there is no mandatory specification on the label that informs consumers that the product must be cooked before being consumed.

Conclusion: This research highlights the importance of adequate and complete information on fresh mushrooms labels, that should include information about the need for sanitization before the consumption, the appropriate storage temperature, and the maximum duration of shelf life. Data obtained could also be useful for food business operators to gather information about the microbial quality of fresh cultivated commercialized mushrooms in order to implement quality controls of the production process and storage conditions.