Listeria monocytogenes: frequency and behavior in \mortadella\ during commercial processing and storage

Author(s)

Luciano dos Santos Bersot

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2000-05-30

Examining board members

Maria Teresa Destro; Mariza Landgraf; José Paes de Almeida Nogueira Pinto

• Advisor: Maria Teresa Destro

Abstract

L. monocytogenes is an important foodborne pathogen that can cause life threating infections. The importance of L. monocytogenes as a foodborne pathogen is well known. Its capacity to resist to adverse environmental conditions makes this microorganism a cause of concern for the food industry. The objectives of this study were to evaluate: the incidence of L. monocytogenes in mortadella samples commercialised in São Paulo, SP, BR; the behaviour of 2 leveis of L. monocytogenes during the processing of 2 formulations of the product stored at difterent conditions and the behaviour of indigenous L. monocytogenes present in vaccum-packed sliced mortadella during the shelf life of the product. Samples were analised by the Presence/Absence technique or By MPN. 26.7% of the mortadella samples were positive for L. monocytogenes. The conventional cooking process (74°C in the coldest point) was sufficient to reduce the population of the microorganism in up to 3 log and the formulation of the product did not interfere with this reduction. L. monocytogenes was not detected during storage of the product for up to 30 days under cold storage (5-8°C) or room temperature (25°C). The vaccum-packed sliced product showed a mean increase of 2.5 log of MPN/g during its shelf life with the bacterium reaching populations around 2 log MPN/g by the end of the período It could be concluded that L. monocytogenes is very frequent in mortadellas; for this product the cooking process is sufticient to reduce up to 3 log of L. monocytogenes. This microorganism could not be recovered during storage for up to 30 days, indicating no sub-Iethal damage. The vaccum-packed sliced product stored under refrigeration is susceptible to L. monocytogenes growth and can be considered risky to susceptible population. (AU)