Factors affecting the safety of aged meat have been assessed in a European Food Safety Authority (EFSA) opinion.

The impact of dry-aging of beef and wet-aging of beef, pork, and lamb on microbiological hazards and spoilage bacteria was examined.

Wet aging is used for meat stored and refrigerated in a vacuum package, while dry-aged beef is refrigerated without packaging for weeks or months which results in a dry surface that is cut off before preparation.

“Aged meat has risen in popularity in recent years among the food industry and restaurants yet until now there has been a lack of knowledge about its safety. EFSA’s advice contributes to filling that gap and provides a solid scientific basis for the food business operators to produce aged meat that is safe,” said Kostas Koutsoumanis, chair of EFSA’s Scientific Panel on Biological Hazards (BIOHAZ).

Time and temperature
EFSA’s experts looked at current practices and identified pathogens and spoilage bacteria that might develop and survive during the aging process. These include Shiga toxin-producing E.coli (STEC), Salmonella, Staphylococcus aureus, Listeria monocytogenes, enterotoxigenic Yersinia, Campylobacter, and Clostridium.

They described the conditions, using combinations of time and temperature in the aging process, under which the production of dry-aged and wet-aged meat would result in the same level of safety as fresh meat.

For dry-aged meat, experts said the surface temperature should not exceed 3 degrees C (37.4 degrees F) during the aging process. This is because at higher temperatures mold might grow on the meat surface and some of these molds produce mycotoxins. Dry aged beef can be considered as safe as fresh beef if aging is done for up to 35 days at 3 degrees C (37.4 degrees F) or lower.

Fresh meat has not undergone any preserving process other than chilling, freezing, or quick-freezing, and most fresh beef, pork, and lamb are matured in vacuum packaging under chilled conditions. Wet-aged meat has been vacuum packed and stored chilled for more than 14 days for beef and longer than four days for pork and lamb. Standard fresh beef was matured in vacuum packs for 14 days or less, while pork and lamb it was typically matured for up to four days.

There is a demand from certain EU countries to allow the use of dry and wet-aged meat for the production of minced (ground) meat and mechanically separated meat (MSM). Currently, the use of meat aged for more than 15 days is not allowed to make ground meat or MSM. Experts could not conclude on the safety of ground meat and MSM prepared from dry or wet-aged meat, compared to fresh meat because of several issues including a lack of data.

Use of defined and controlled conditions
Data on key parameters such as the surface pH, water activity, and temperature of the meat, that could influence the survival or growth of pathogenic and spoilage bacteria as well as molds and mycotoxin production was provided. Predicted growth was simulated by using microbiology models, with different aging scenarios covering factors associated with the aging processes.

Based on predicted growth, the main microbiological hazard is Listeria monocytogenes for all meat types and Yersinia enterocolitica for pork.

Information on temperature, relative humidity, airflow, and time was collected about the processes and practices used by meat plants, butchers, and restaurants. Replies to questionnaires were received from two industry associations and eight food companies.

Under current practices, the aging of meat impacts a load of microbiological hazards and spoilage bacteria compared to the standard fresh meat preparation. The extent depends on the conditions of aging, the properties of the meat, and the presence of competing microorganisms said scientists.

They found aging under defined and controlled conditions can achieve the same or lower levels of microbial hazards and spoilage bacteria than increases predicted during fresh meat production.

The safety of meat is assured through hazard analysis and critical control points (HACCP) and prerequisite programs (PRP), including good hygiene practices and good manufacturing practices. As standard fresh meat preparation and wet-aged meat differ only in the time applied, controls are similar.

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