Pala, Carlo (2017) Development of a post-lethality treatment to reduce the risk of Listeria monocytogenes contamination in Ricotta salata cheese. Doctoral Thesis.
Listeria monocytogenes contamination in Ricotta salata cheese rind is a common finding. In the last year numerous cases of food alert and even of human listeriosis associated with the consume of Ricotta salata have been reported in different Member States of the European Union and other countries. The presence of L. monocytogenes in the cheese making plant environment represent an important risk factor in the contamination of ricotta salata (i.e. post-proces contamination). L. monocytogenes is mainly localized on the rind of the product. The reduction of the risk associated with environmental contamination can be obtained through the application of post-lethality treatment. The feasibility to inactivate L. monocytogenes using water bath heat-treatment under experimental conditions has already been demonstrated by Spanu et al., (2013). The aim of this work was to optimize a water bath heat treatment, which can be used at industrial level, allowing the control of L. monocytogenes post-process contamination in Ricotta salata wheels and wedges. For each type of product was tested the efficacy of 9 time-temperature combinations on samples artificially inoculated with L. monocytogenes. On the test units were conducted microbiological, physic-chemical and sensorial analysis. The best time-temperature combination would selected taking into account the inactivation level of L. monocytogenes (the target was set at 5-log reduction), the economic sustainability of the treatment and the influence on sensory properties of the product.
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