Outside in: assessment of microbial composition of the crust of dry-aged beef and its relevance in relation to food business operator practices

Dry aging of beef has recently been defined in Delegated Regulation 1141/2023, amending Regulation 853/2005. The delegated regulation lists specific measures to be applied when processing such a product. Specifically, a point is dedicated to the crust trimming that should be carried out in a hygienic manner, since the interventions performed at the end of the process might determine contamination of the edible parts. Nevertheless, despite the punctual application of good hygiene practices (GHP) and good manufacturing practices (GMP), a certain degree of contamination with pathogenic and spoilage microorganisms of the cut portions cannot be avoided, as demonstrated by some authors reporting contamination of the inner parts of dry-aged meat. In order to investigate the level of contamination occurring in field conditions during trimming and portioning, we performed two different trials: the sterility trial with the aim of evaluating the sterility of the inner parts of beef during aging and the contamination trial to assess the transfer of microbial populations from the outer to the inner part of the dry-aged beef. All tests were performed by means of cultural and non-cultural methods. Results of the sterility trial show that a very limited percentage of non-host DNA is present in the inner parts of the meat starting from the beginning of the test and that the detectable DNA increases slightly during the time of aging. Besides, the contamination trial results showed that the contamination of the trimmed meat is qualitatively and quantitatively related to the contamination of the crust. As a consequence, adherence to GHP and GMP during trimming and handling of dry-aged meat according to scientific literature is crucial to avoid/minimize cross-contamination since our data clearly demonstrate that processing practices are fully reflected in the final product quality.