Determination of Growth during Mushroom Production and Distribution.

In the EU, food is considered safe with regard to if its numbers do not exceed 100 CFU/g throughout the shelf-life of the food. Therefore, it is important to determine if a food supports growth of . Challenge studies to determine the ability of a food to support growth of are essential as predictive modelling often overestimates the growth ability of . The aim of this study was to determine if growth of was supported during the production and distribution of mushrooms. A three-strain mixture of was inoculated onto three independent batches of whole mushrooms, sliced mushrooms, mushroom casing and mushroom substrate at a concentration of about 100-1000 CFU/g. The batches were incubated at potential abuse temperatures, as a worst case scenario, and at intervals during storage numbers, % moisture and pH were determined. The results showed that the sliced and whole mushrooms had the ability to support growth, while mushroom casing allowed survival but did not support growth. Mushroom substrate showed a rich background microflora that grew on selective media and this hindered enumeration of . In the case of this study, Combase predictions were not always accurate, indicating that challenge studies may be a necessary part of growth determination of .