Meat Ageing Hanging Cabinets
Meat Ageing is the process during which microbes and enzymes act upon
the meat to help breakdown the connective tissue to tenderise the meat.
There are two ways ageing can be accomplished:
- Wet ageing by placing beef in a plastic bag under vacuum; or
- Dry ageing by storing beef in a temperature and humidity controlled
The main difference is that wet ageing results in little or no moisture
loss, whereas dry ageing can result in up to 50% moisture loss.
Dry ageing storage conditions:
Temperature: between - 0.5°C to 1°C (2°C to 3°C may be used when only
ageing for up to 3 weeks);
Relative Humidity: between 75% to 85%;
Air velocity: between 0.2 to 0.5 m/s.
Dry ageing involves the degradation of connective tissue and muscle
protein structure of the meat of carcasses or cuts of meat and must be
managed to ensure growth of beneficial and non-harmful moulds. Best
practice is to reduce carcasses to smaller primals and sub-primals in
preparation for the ageing process. The most popular cuts used for
ageing are strip loin, rib eye and sirloin that can be aged in dedicated
refrigeration units or rooms. For dry aged meat, the fat cap is often
left on the meat to help with flavour development, retention of moisture
and reduction of trim loss when the crust is eventually trimmed off.
Dry aged beef has an intense flavour when compared to wet aged meat that
can have a sour blood/serum flavour. The reason for this is that the
predominant bacteria on dry aged meat are the Pseudomonas that grow in
the presence of oxygen. This is different to wet aged packaged meat
where Lactobacilli bacteria grow in the absence of oxygen. The
Lactobacilli bacteria convert lactose to lactic acid therefore wet aged
product may have a slightly sour taste or odour when compared to the
Pseudomonas that do not produce any sour flavours on dry aged meat.
Dry aged beef is considered a gastronomical treat and is commonly found
in some of the finest restaurants and butcher shops. Premium dry aged
beef products usually come from grain fed cattle due to the greater
marbling within the meat. Extremely lean meat will spoil if aged. The
flavour of dry aged beef can range from buttery to nutty and almost
gamey depending on the age and storage conditions. The flavour is also
dependent on other factors such as the quality of the meat cut, whether
it is grass fed or grain fed, storage temperature and relative humidity
during ageing. Premium products can be dry aged for up to 6 weeks
provided the process meets the requirements of these guidelines. It may
be difficult to maintain the wholesome of meat after 8 weeks of dry
1. Enzymatic action
Endogenous proteolytic enzymes from the meat itself as well as from the
specific beneficial moulds weaken the structural myofibrillar proteins
in the meat. This takes 10 to 14 days and results in a more tender meat.
At this stage the meat flavour can usually be described as buttery and
Loss of water from the meat by evaporation causes concentration of the
remaining proteins and increases flavour intensity to a nutty almost
gamey taste. Final water loss can be up to 50 per cent and depends on
the relative humidity used during drying.
A storage temperature between -0.5°C to 1°C should be used. A
temperature of between 2°C to 3°C may be used when the meat is only aged
for 2 to 3 weeks. Frozen or thawed meat must not be aged because the
desired enzymatic action will not occur and mould growth will not be
initiated on the surface of the meat. The temperature must be recorded
daily throughout the ageing process to ensure the wholesomeness of the
meat is maintained in compliance with the requirements of Australian
Standard for the Hygienic Production and Transportation of Meat and Meat
Products for Human Consumption (AS 4696:2007).
4. Relative Humidity (RH)
Control of RH is important because it restricts growth of pathogenic
bacteria by drying the meat surface resulting in the formation of a
crust. This also reduces bacterial growth on the surface in preparation
for growth of the desirable Thamnidium mould. A RH of between 75% to 85%
is recommended and actual RH should be recorded daily for the duration
of the ageing process. Lower RH may be used but tends to dry out the
meat and contribute to higher trim losses in the final product. Higher
RH should not be used because it will result in spoilage of the meat
before ageing is complete.
5. Air Flow
To prevent spoilage, portions of meat must be adequately separated from
each other to allow efficient and controlled air flow between each
portion. The desirable air velocity is 0.2 to 0.5 m/s and can be
controlled with a properly designed refrigeration unit and fans. The air
velocity and flow should be kept uniform for the duration of the drying
process and is most critical at the start of the dry ageing process.
6. Cross contamination
Dry aged meat must be segregated from all other meat products. Dry
ageing must not be conducted in chillers where other fresh meat is
stored. Purpose built rooms and cabinets must be used for the dry ageing
of meat. Trimming and preparation of product for packaging and sale must
be segregated from areas used for fresh meat. Dry aged meat products
must not be displayed in retail display cabinets with other fresh meat.
Designated cabinets and/or chillers must be used.
7. Antibacterial Strategies
The use of ultraviolet (UV) light for destruction of bacterial cells is
well known for fresh meat. A more sophisticated approach to manage the
dry ageing process is to install UV lighting entirely and leaving no
other light source. Air can also be circulated through UV lit chambers
however the costs may be prohibitive. The use of antibacterial rinses
for the preparation of meat for dry ageing has some inherent risks and
must be validated and approved.
Dry ageing involves restricting bacterial growth and encouraging the
growth of beneficial mould. During the dry ageing process, mould from
the Thamnidium, Penicillium, Rhizopus and Mucor genera can be found on
the surface of the meat. The most desirable is the Thamnidium mould as
it has been shown to releases proteases that tenderise ageing meat.
Other mould species have been associated with infections in humans and
production of harmful natural toxicants. They also do not provide any
favourable characteristics for ageing of meat.