Venison backstrap

Wet and dry ageing: the best ways to process your wild game meat


To get the best from your wild game meat, the ageing process is critical but getting it right can be simple if you know how. This article will set you right.

It provides an introduction to the key principles underpinning successful wet and dry ageing of meat.

Ageing meat
In the shade under Tassie winter conditions, hygienically butchered game meat can be stored in brand-new plastic bags for several days before seeing refrigeration

Wet ageing in sealed vacuum packs significantly extends shelf life and improves tenderness. 

Dry ageing is a more demanding technique that likewise improves tenderness but also enhances flavour. 

We’ll cover both approaches to ageing in some detail, including their pros and cons, and how they can be applied to game meat.

1. CHILL IT: THE COOLING PROCESS

In older times, all fresh meat was eaten within a few days, before it spoiled. Extending shelf life relied primarily on salting, drying and fermenting techniques, but these treatments fundamentally changed the meat’s texture and flavour. 

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Supermarkets routinely extend shelf life using vacuum packaging. This photo was taken on 5 July, a full 19 days before the use-by date

The advent of refrigeration was the key advance in extending the shelf life of raw meat.

Both wet and dry ageing of fresh meat are options under refrigerated conditions.

Technically, ‘refrigerated conditions’ means 0°C to 4°C, but in practice, different zones in a domestic fridge might range from 8°C in the top compartment to close to 0°C at the floor. The Australian Standard for fridges specifies a fresh food compartment average temperature of 3°C.

Modern abattoir practices aim to reduce the temperature of the warmest part of a carcass (the centre of the hind leg) to less than 7°C within 16-24 hours post-slaughter for sheep and within 48 hours for beef. 

More pertinently for hunters, the Australian Standard for wild game processing (AS4464 2007) requires carcasses to be under refrigeration within two hours of slaughter, or within two hours of sunrise for animals harvested during night time. Refrigeration conditions in this Standard also target chilling to 7°C within 24 hours.

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Vacuum packaging machines are cheap and readily available. They are all you need for wet ageing your game meat

Some microbial growth will inevitably occur on the exposed surfaces of meat during the time between slaughter and chilling. However, it is important not to chill meat too quickly if toughness due to cold-shortening is to be avoided. This happens if the meat temperature is reduced to less than 10°C in under 10 hours. 

Hence there is a bit of a trade-off between temperatures that are optimal for tenderness as opposed to shelf life.

Keeping in mind the logistics of moving meat around, it clearly takes a while between slaughter and the appearance of chops in the butcher’s display case. For example, in the EU, the maximum storage time between slaughter and processing of meat into mince and other products ready for consumption is no more than six days.

These industry standards provide some broad guidance for hunters when handling game meat. 

If meat is harvested hygienically and chilled appropriately, then up to a week in the fridge is not a concern.

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Venison from the field can be refrigerated for up to seven days, then trimmed and vacuum packed for some weeks of wet ageing

2. WET AGEING: VACUUM-PACKED SUCCESS

While the fridge life of raw meat ready for consumption is just a few days, a big advance came with vacuum packaging of meat cuts. During a casual perusal of the shelves in the supermarket, I found vacuum packaged steaks with use-by dates up to 19 days ahead of the time of my visit. 

Such a long shelf life is possible because removal of the air using a cryovac machine inhibits the growth of many common spoilage micro-organisms.

Some bugs need oxygen (aerobic) for generating their energy for growth, while others can proliferate happily in its absence (anaerobic). Some bugs can even swap from aerobic to anaerobic metabolism, but in the presence of oxygen, 19 times the energy can be generated from the same mass of glucose when used as cellular fuel. Basically, things slow down a lot when an applied vacuum removes all the air and the meat is stored nice and cold.

During prolonged anaerobic refrigeration, lactic acid bacteria are the preferred bugs that will grow slowly over time. These are the same bacteria that ferment salamis, sourdough bread and yoghurt. Because these bugs generate lactic acid, wet-aged meat may taste slightly ‘acid sour’. However, they are not harmful, and over 10 million per gram may be present without spoilage signs being evident.

If the wrong bugs get a leg-up due to field contamination or elevated temperatures during ageing, they will out-compete the desirable ones and deliver a slimy, discoloured and potentially putrid outcome.

The key benefit of wet ageing in vacuum packs is improvement in tenderness. With time, the natural enzymes in the meat tissue start to break down the proteins in the muscle fibres.

I became a convert after a mate served me some venison rump steaks that I reckoned were the juiciest and most tender I had ever had the pleasure of eating. What was his secret? Three to four weeks in the fridge! 

He said he’d experimented out to six weeks but there was no incremental benefit apparent in eating quality.

For years I had been routinely vacuum packing my game meats, but the reason was to extend storage life in the freezer. In the absence of air, freezer burn, development of fat rancidity and drying of the meat is eliminated. However, I would typically freeze the meat immediately after the vacuum packaging step. My eyes had not been opened to the possibilities of further ageing after performing the cryovac step.

I set to work researching the literature to improve my understanding of the wet-ageing process. I discovered that under ideal conditions, the storage life of wet-aged beef can be extended to at least 70-84 days. Even as a qualified microbiologist I find it pretty amazing that raw meat, untreated with preservatives, can remain wholesome after such an extended interval!

Yet, believe it or not, even further enhancement to the wet-ageing process may be possible with other innovations such as use of modified atmosphere flushing and chemically active packaging films.

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Dedicated dry-ageing fridges are increasingly appearing in shopping centres and speciality butchers

3. DRY AGEING: FOR FULL FLAVOUR 

Then there is dry ageing to consider. One might wonder about the motivation for dry ageing meat when wet ageing can attain similar storage life, along with improved tenderness. However, the main driver for dry ageing is flavour enhancement on top of the gains in tenderness.

In pursuit of these attributes, beef is typically dry aged for 28-42 days, with some specialist suppliers pushing the envelope well beyond this, out to 100 days and beyond. Dry ageing works best with large pieces of fatty beef; especially if marbled and with the surface-fat layer intact. During ageing, the bugs break down these fats to create more complex flavours.

Dry Ager, one of the main suppliers of the specialist refrigerators for dry ageing of beef, has also achieved good results in trials with pork belly, duck and even fish. Further, there are reports on the web of great tasting dry-aged venison, a much more lean meat.

Key control parameters for the dry-ageing process include temperature, air flow and relative humidity. Temperatures should be below 2°C to encourage the growth of desirable bugs that aid the development of tenderness and flavour (a particular fungus called Thamnidium does the work). 

Basically, the colder the better. Keep in mind that because of its salt content, meat does not freeze until about -2°C.

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A large dry-ageing meat room. Large cuts are typically aged for four to six weeks under precisely controlled conditions before cutting and trimming pieces for consumption (photo courtesy Dry Ager)

To illustrate the importance of just a few degrees during ageing, spoilage happens 50 percent faster at 5°C than at 0°C. Humidity needs to be low enough to form a crust, which inhibits slime development, yet high enough to minimise weight loss due to unnecessary drying.

Air flow is important because the meat must form a protective rind that slows moisture loss. Dry-ageing fridges not only precisely control air flow, but also decontaminate the incoming air to reduce contamination risk.

The trade-off for the high flows of circulating air is moisture loss. Typically, dry ageing will cause a reduction of 15-20 percent of the product weight and a similar amount lost to trimming off the dry crust at time of sale. This makes dry ageing a very expensive process — only the connoisseur carnivore can justify such a price!

These days, dry-ageing bag technology is available, which combines the benefits of dry ageing with those of vacuum sealing. These bags are made from a special film polymer that is highly permeable for water. Primal cuts of venison, such as a whole hindquarter, can be aged for at least 30 days with resulting enhanced flavour and tenderness, yet without the same extent of drying and trim losses seen in a ventilated fridge. The bags can be sourced in Australia from specialist suppliers.

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A range of game meats can be dry aged, resulting in enhanced and more concentrated, complex flavours (photo courtesy Dry Ager)

4 WET OR DRY? WHAT ARE THE OPTIONS?

For those hunters wanting to add that special touch to their hard-won wild game meat, wet and dry ageing are options that are readily available. Both processes essentially create environmental conditions that favour ‘good’ micro-organisms to perform special, desirable chemical modifications to the meat.

Wet ageing needs only a small cryovac machine (readily obtainable from any whitegoods retailer) and a refrigerator capable of consistently holding below 4°C. 

Dry ageing needs a fridge with an open wire grille on which to position the primal cut of meat and which allows free circulation of air around it. For the home hobbyist, a regular domestic fridge with dry ageing bag may suffice, or perhaps (budget permitting) try the entry-level Dry Ager machine, which runs to around $6200 and can age about 20kg of meat.

Above all else, remember that successful ageing requires minimal contamination of the starting material, which in turn requires excellent hygienic field-butchery skills.   

David Hughes has a Bachelor of Science degree with undergraduate majors in microbiology and biochemistry and first class honours in biotechnology. He also has a Master of Science degree in biotechnology. He has worked as a food microbiologist and as a senior manager in biopharmaceutical manufacturing roles.

 

 

 


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