Storing hot-boned cuts in the shade is fine if temp is below 10 degrees celsius.
The hunting instinct still runs as strongly in some of the folk of the 21st century as it has for millennia. Although homo sapiens today bear the technological trappings of centuries of thinking in the sciences and engineering, the instinct to provide meat for the tribe is programmed into our genes. Ancient men took trophies of the hunt as symbols of the beauty and fierceness of their quarry, and harvested the flesh to feed their families.
Many hunters of today remain primarily motivated to use the bounty of their harvest. The humble bunny kept thousands alive during the depression, and the prospects of a few ducks or quail when the season permits still entices thousands of Aussie hunters into the field. Deer are more plentiful than ever, hence the prospects of bringing home some venison for the table is more easily achieved than in years past.
When I first started deer hunting, I had in my mind that butchery entailed gutting the beast, hanging it up, then skinning and boning-out the meat after the carcass had cooled-down and had set hard. Most hunting books and magazines seemed to regard this methodology as the standard approach. Later I started hunting with guys who typically cut the meat off the fallen deer immediately after death, then loaded it into garbage bags, before it went into the backpack and carried back to camp.
As someone with a university degree in microbiology, the idea of putting hot meat into plastic containers at first seemed horrific. Wouldn’t growth of bad bugs be accelerated by the warmth contained within the bag and backpack? Seemingly the carriage and holding time in plastic must be bad practice from a food hygiene perspective?
1. Temperature, Hygeine and Transport. Well, all other things being equal that would be the case. But when we have a deer on the deck there are a few basic considerations that go into the formula for cold or hot butchery. The key issues are the ambient temperature, use of hygienic techniques and logistical constraints. The latter includes the size of the animal, the terrain, accessibility to a vehicle, and ready ability to hang a whole carcass. What this all means is that either hot or cold boning methods can be quite appropriate – it just depends on the circumstances.
The keeping quality of meat depends on just two factors – temperature and the extent of bacterial contamination. Before injury and external exposure, all muscle and tissue (other than in the gut passage) is sterile. It won’t “go-off” just by itself. The contamination is determined by your field hygiene. Your knife is covered in bacteria, as is your skin and every other exposed surface. Soil and debris in the mix when you are cutting up a carcass is a recipe for disaster. I habitually use surgical gloves when I am recovering meat from a warm carcass, but you can get away without them if you do everything else right. If the temperature is cool, you use a clean knife, avoid any bloodied or bruised tissue, and put the meat straight into new plastic bags, you are in business – with little risk of food poisoning. Plastic bags are extruded in molten form and are sterile when taken out of the packet.
2. Plastic bags are not all bad. My initial aversion to the concept of hot meat going into insulating plastic was eliminated when I realised that under the prevailing conditions those concerns were unwarranted. I was hunting fallow deer in Tasmania, and the temperature in the shade under the veranda of our hut was usually below 15 degrees Celsius. Combined with the cooling effect of the usual chilly breeze stripping away residual heat through the hanging thin-walled bags, heat retention was just not an issue.
3. Cooling too quickly is bad. It might be of interest to meat hunters to know that cooling too quickly can actually have a detrimental impact upon tenderness. In the abattoir situation, animals are chilled at a controlled rate to take this into account. Over-fast chilling results in toughness called cold-shortening. This terminology arises from the shortening of the muscle fibres which is induced when the temperature of the muscle falls below 10 degrees Celsius while the pH is above six (pH being a measure of acidity when less than 7). Slow, gradual cooling allows the muscles’ stored energy (in the form of glycogen) to break down into lactic acid, which ultimately will drop the pH from about seven to 5.4–5.8. This is ideal for a tender result. In the abattoir they give this process a hurry-on by using electrical stimulation of the carcass. Under those conditions the target is to attain under 10 degrees Celsius in about 10 hours. In the field this may take 24 hours or more, depending upon the temperature.
I managed to create some boot leather-tough goat meat because of chilling too fast. I had shot a couple of nice, half-grown goats one very warm Queensland summer morning. I recovered the back-straps and some hind legs which were stuffed into my backpack before hurriedly returning to camp. I was paranoid that my meat would spoil in the prevailing heat, and promptly dumped it into the three-way fridge and wound up the gas full-bore. Those of you familiar with these camp fridges will be aware that they can cool very rapidly, and will freeze the contents close to the heat exchanger plates. I have no doubt that my wonderfully hygienically-recovered meat was chilled below 10 degrees Celsius within a few hours, and the result left me dismayed. I learned later that cold shortening affects young animals even more because their connective tissues are softer and offer less resistance to the shortening process.
4. Vehicle recovery. Ready access to a vehicle opens the option of recovery of the whole carcass, even if conditions are conducive to hot-boning of the fallen deer. A couple of good keen men can sling a gutted deer into the back of the ute, and a simple gambrel and pulley system using a low branch can hoist the deer off the ground, safe from attention by Devils or dingoes (these hazards depending upon your geography). This method has the advantage that the team can retire to the camp for a few sherbets and worry about the meat on the morrow! If in Tassie, you might leave the dismembering till the day after, or (in winter) even the day after that without adverse result.
Whether you cut up the fallen beast in the field, or back in camp after hanging for a period, it is beneficial to leave the hide on the animal until it is processed for storage. The hide protects the tissue from contamination and hence extends its keeping time. Regardless if you are humping out a leg of sambar in the Wonnangatta, or chucking a whole fallow into the ute in Tassie, the primary recovery will be more hygienic if you leave the skin on.
5. Natural Line Boning for hygeine. When hot-boning a deer on the ground in the field, the contamination risk is reduced if you separate the muscles along their natural silver skin membranes. This film protects the muscle tissue from any contamination. In comparison, bugs contaminating the surface of freshly cut and bloody meat can start proliferating immediately. The silver skin can be trimmed off later under the more controlled conditions of the home kitchen. If your vehicle or camp are a fair tramp away, the benefits of hot boning are readily evident. Carrying heavy bones is an unnecessary burden. The usable meat from a deer is about 55-60% of its live weight (called the “dressing percentage”). With practice it takes only a few minutes to whip off most of the recoverable meat. One of my Tassie mates, who would on average dress-out over 100 deer per annum, can have the main cuts off in less than 10 minutes (back legs, back-straps and shoulders).
Once your hygienically-harvested meat is stored safe and sound under refrigeration at around 4-degrees Celsius, it is beneficial for eating quality to leave it for some days to tenderise. During this period the natural protein-degrading enzymes in the meat will gradually work away to soften up the muscle fibres. The older your animal, the more the benefit that will accrue. The meat from an old stag will need aging more than a yearling for a palatable outcome. I usually leave venison up to a week before separating out the cuts for longer term frozen storage.
If you are like me and have no formal training in butchery, the whole exercise can seem rather challenging. However, you gradually get a feel for all the major muscle groups by the time you cut up a few dozen legs and along the way absorb the learning of the experienced folk around you. The internet is a rich source of information, with a couple of handy links at http://www.meatupdate.csiro.au/data/Operations_and_control_03-85.pdf and http://www.brahman.com.au/technical_information/meatScience/veryFastChilling.html
Back at home, I divide the muscles up into portions that can feed a couple of people at a sitting, or I leave larger cuts that can be roasted for a group. Investment in a small cryovac machine is invaluable for frozen storage. These days they are readily available in department stores. The machine is very simple in principle. All it does is suck out the air from the bag then seal it with a heating bar. This vacuum packaging has a hugely beneficial effect upon the quality and longevity of frozen meat. In the absence of air, the growth of bacteria and the oxidation of fats in the meat is diminished, which means the meat stays tasting fresher for longer. The other benefit is reduction of “freezer burn”. In the past, before small cryovac machines became commonplace, the surface of frozen meat was prone to unsightly “scalding” on exposed surfaces of the meat. This type of deterioration is due to moisture loss from the meat, as even under frozen conditions water will evaporate from the solid ice into the air (a process called sublimation). Drying and oxidation of the meat will result. Freezer burn won’t hurt you, but it looks a bit ordinary.
Sticking to the basic rules of avoiding contamination in the field, then appropriately chilling, handling and packaging the recovered venison will mean you can look forward to a freezer full of lean, healthy meat to supplement the family larder and reduce the family budget. I also find that the network of family and friends soon learn how tasty venison really is. This acknowledgement in turn facilitates a useful discussion about responsible hunting and the environmental benefits associated with controlling numbers of feral animals in the Australian bush.