Microbiological safety of dry-aged meat: a critical review of data gaps and research needs to define process hygiene and safety criteria

Abstract

Dry-aged meat is gaining popularity among food business operators and private consumers. The process is carried out in aerobic conditions by hanging beef carcasses or placing subprimal or primal cuts in a dedicated cabinet for several weeks or even months while controlling the environment through the management of process parameters such as temperature, relative humidity, and airflow. In this review, we present a critical evaluation of the literature to evaluate tools to manage the process to guarantee food safety and identify critical control points, as well as good hygiene and manufacturing practices. In controlled aging conditions, only Listeria monocytogenes and Yersinia enterocolitica can multiply, while a reduction in the number of Salmonella spp. and Escherichia coli O157:H7 is generally reported. Enterobacteriaceae usually decrease on the surface of the meat during maturation; thus, for the purpose of the hygiene evaluation of the production process, a count no higher than that of unmatured meat is expected. Besides, various studies report that the total bacterial count and the spoilage microorganisms significantly increase on the surface of the meat, up to 5-6 Log₁₀ CFU/g in the absence of visible spoilage. Bacteria of the Pseudomonas genus tend to progressively replace other microorganisms during maturation; thus, the total mesophilic or psychrophilic bacterial load is not a good indicator of process hygiene for matured meat. Critical parameters for the control of the process are temperature, relative humidity, and ventilation, which should be monitored during the process. For this reason, equipment designed and certified for dry-aging must be used, and the manufacturer must validate the process. Food business operators must apply general good manufacturing practices (GMP) and good hygiene practices (GHP) for meat processing and some GMP and GHP specific for dry-aging. Several research needs were identified, among them the evolution of the populations of L. monocytogenes and Y. enterocolitica and the microbiology of the inner parts of the dry-aged meat.

Keywords: dry-aged meat; microbiological criteria; molds; pathogenic microorganism; spoilage microorganism.

Figure 1.

A) Air speed influencing the drying of meat; B) different meat and fan positioning within cabinets can affect dry-aging.

Figure 2.

A,B) Beef hanging from the bones when is not directly positioned on the shelves; C) correct positioning of ribs: a distance of usually 3 cm is considered the minimum among ribs; D) ribs are too close to one another and do not allow correct circulation of airflow.

Figure 3.

A) Meat with deep spoilage; before trimming the meat showed a fessuration with a humid appearance; after cutting meat showed areas of discoloration (green) with off odor that increased after cooking; B) meat with regular surface: a uniform crust can be observed; C) meat with regular surface, but with fessurations on the surface; D) meat with irregular surface: the crust is irregular and several fessuration can be observed; E) meat with regular surface and with regular and homogeneous crust; F) dry-aged meat with beef tallow applied on fissurations.