Report on the establishment of the safe shelf life of certain ready-to-eat foods, sliced and prepacked in retail, in relation to the risk of Listeria monocytogenes

Abstract

The Barcelona Public Health Agency (ASPB) asked the Scientific Advisory Committee on Food Safety for an opinion on the safe shelf life of Listeria monocytogenes in certain products (cheeses, cooked meats, including pâtés, and cured meats) sliced and prepackaged prior to retail sale.

In order to assess in which cases or under which conditions ready-to-eat foods under study may promote the growth of pathogenic microorganisms during their shelf life, the methodology proposed by EFSA (2020) was used. In addition, the predictive model of growth / non-growth boundaries, based on the gamma concept approach, was applied.

To carry out this assessment, the ASPB provided a total of 90 samples (32 in 2020 and 58 in 2021) divided into 4 categories of ready-to-eat foods: cheese, cooked ham, pâté / foie and cured ham. In all cases, the food was sliced or cut into portions in retail establishments of the city of Barcelona, and packaged in different formats: vacuum-packed, in a heat-sealed or shrink-wrapped tray, or wrapped in film.

The results of the evaluation indicated that the ready-to-eat pre-packaged foods evaluated for the group of cheeses, cooked ham, pâtés and foie required the indication of a “use by” date, as the handling conditions expose the product to a potential L. monocytogenes contamination and the pH and aw (water activity) characteristics associated with these products support its growth.

Considering a reasonably foreseeable scenario in relation to storage temperature conditions in retail (2 days at 5°C) and in a domestic refrigerator (5 days at 9.5°C), the safe shelf life of the products that would more favour the growth of L. monocytogenes would be between 4.5 and 4.9 days (corresponding to the 5th and 10th percentile, respectively). This estimate is the result of a conservative approach that provides a margin of safety to the outcome of the evaluation.