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Bullets, Bows and Butchery: Post-Mortem Handling (Part 2)

In this post, I will expand on some of the topics mentioned at the end of Part 1:

  1. Cold Shortening

  2. PSE (Pale Soft Exudative) meat vs DFD (Dark Firm Dry)

  3. pH control and manipulation

Cold Shortening

This is one of the areas that most commonly goes wrong in handling venison. Cold shortening involves the contraction of muscle fibres during the chilling process without subsequent relaxation of those fibres, meaning the meat becomes tough and cannot be tenderized by aging it.

How does this happen?

The conditions required in order for cold shortening to occur are:

  • pH of the carcass is above 6.2

  • Residual ATP is still in the msucles

  • Carcass temperature drops below 10 celsius pre-Rigor Mortis

All 3 conditions must occur simultaneously, and routinely occur with venison.

Let's look at an example:

A hunter shoots a Kudu, guts it in the field, and transports the carcass directly to their on-site cold room running at 2-4 celsius. pH at time of death of the Kudu is 7 celsius, and will drop to around 5.7 over the next few hours. Until such time as pH has dropped, the muscles remain with surplus ATP (energy for contratcion of muscle fibres, basically), so as the carcass is rapidly cooled down to the cold room temperature, the muscles start to shorten and move closer together (the meat becomes tough).

This is why in the beef industry, carcass are subjected to electro-stimulation:

carcasses which have been slaughtered and are undergoing Primary Chilling given electro-stimulation ( the carcasses are "shocked" with electrical pulses) in order to stimulate the muscles to burn up ATP quicker, thereby removing 1 of the 3 necessary conditions for cold shortening to occur.

So a Kudu that was well handled and butchered still ends up on a plate as piece of meat as tough as leather.

The 2 easiest solutions are:

  • Slow down the cooling curve/gradient- which is actually easily achievable by simply hanging the carcass at ambient temperature in winter for a night (rustic method)- OR until the pH level has dropped to under 6.2, this would be easily monitored with a Pocket pH meter from Hanna Instruments, and sold on our website: https://www.gameandgrass.com/online-store/Pocket-pH-meter-HI981036-p168657233

  • Alternatively one could electro-stimulate vension carcasses the same as standard abattoir procedure dictates. Interestingly, this is the very same thing that is happening when one shoots an antelope and the carcass continues kicking despite being completely dead. its actually desirable for thhis to occur in a sense, because the muscles require ATP to keep twitching post mortem. So as the animal carcass continues to kick,the msucles are consuming excess ATP and ensuring that rapid cooling does not suffer cold shortening if it is rapidly cooled to under 10 celsius before going into Rigor Mortis.

This topic is covered in greater detail at http://ecoursesonline.iasri.res.in/mod/page/view.php?id=68828

OR

http://www.fao.org/3/t0098e/T0098E02.htm


DFD vs PSE Meat:

PSE

When an animal is subject to stress ante-mortem, glycogen reserves are released by the body into the bloodstream, such that, post-mortem there is surplus fermentable sugar int he body to convert into lactic acid. This is more common in pork that in red meat, and manifest visibly as meat which is Pale, Soft to the touch, and Exudative, meaning it appears to be oozing moisture. you would be fooled into thinking this meat would be tender if cooked, but in fact it has low pH levels and therefore release moisture rapidly and will be very dry to the taste. This meat however, is excellent for charcuterie as it will dry faster due to its low pH.


DFD

In contrast to PSE meat, Dark Firm Dry fresh meat indicates that the meat has high pH, which means the meat will retain moisture for longer, will be more tender and juicy if cooked, BUT will also spoil faster as spoilage bacteria grow more rapidly due to the higher pH. This condition tends to be more common in red meat and is also referred to as Dark Cutting meat. DFD meat is not well suited for charcuterie due to it water holding capacity as a result of high pH.

The bottom line is, pH variations dont render a product automatically useless. Rather, it means one should consider the suitable end-use for each pH of meat, with pH considerations in mind. For more on this, the reader can go to: http://www.fao.org/3/x6909e/x6909e04.htm


pH Control and Manipulation:


Raising pH

It does happen, that even under well controlled conditions, carcasses do not achieve ideal pH levels. Typically, we look for 5.7/5.8 in our carcasses, if it comes in at over 5.9, its likely that we send the carcass back, although if the meat is in good condition and is very fresh, we can brine it immediately for pastrami and typically it produces an excellent end product.

Brining meats to be hot smoked often involves artifically raisingmeat pH levels.

How?

Many commercially sold brines include Sodium Carbonate, which is significantly more potent at raising pH that a regular househould ingredientvwe all bake with: Sodium Bicarbonate!

Other ingredients that raise meat pH are cream, full cream milk powder, whey powder. Full Cream Milk has a pH of around 6.7, signifacntly higher that meat, and so milk powder in fact can be used as part of a marinade or rub to increase Water Holding Capacity of meat, which makes it juicier when cooked.


Lowering pH

Typically with charcuterie, we want to LOWER pH, because lower pH meat loses water at a faster rate and spoils slower as lower pH levels create an environment which is less favorable for spoilage and/or pathogenic bacteria. (spoilage bacteria is not necessarily pathogenic always, it just smells and tastes bad.) Consider how many have eaten meat that smelt "off", yet the person didn't get ill. However Staphylococcus Aureus, which is responsible for the overhwleming majority of cases of food poisoning worldwide, has no smell and no taste, but is pathogenic.

Now, one of the most common ways in which pH is lowered in meat can be through adding vinegar, which we do when making biltong,as vingar has a pH of around 3.0. Thus, bacteria are severly or entirely inhibited from grow on meat which is soaking in biltong brine which is high in vinegar.

With cheaper, factory made dried meat products like salami, Glucono-Delta-Lactone, which is a natural acidifying agent, is added to produce a reliable pH drop in the meat and thereby rendering it less likely to spoil.

In better quality products, we use beneficial bacteria known as Starter Culture which replicates the same mechanics as a natural pH drop that occurs in carcasses post mortem:

Sugars which are fermentable by beneficial bacteria are added with the bacteria to the the meat products, which are the held under conditions which favour the bacteria in consuming up all the sugars and converting them into Lactic acid, which lowers the pH of the meat, thereby making it safer and also causing it to release water at a faster rate.

More on this topic later, but for now, the reader can go to:

http://www.fao.org/3/x6932e/X6932E05.htm


If you like this post, or if there is a particular topic or matter you would like to know more about, please do send us a message at info@gameandgrass.com !







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