Aging of meat is defined as holding carcasses at low temperatures

In simple terms "aging of meat" is defined as the practice of holding carcasses or cuts at low temperatures - 34º F to 37º F (2º - 8º C).

When the animal dies, blood stops circulating, and there is no supply of oxygen or nutrients to the muscles. Muscles rum out of energy, and they contract and become stiff. Eventually, muscles become soft again, which means that they are tender when cooked.

Very often people wonder what the best meat for making meat products is. The absolutely best meat is that of a freshly killed animal. It has unbelievable binding qualities – it naturally holds water and juices inside. Additionally, live animals have very few bacterias, but these will start to multiply quickly after death. In many tropical countries, fresh sausages are often produced from warm slaughtered or "prerigor" meat.

During this “post mortem” period, the meat is of the highest possible quality. Unfortunately, it only lasts for a brief period:

Pork	1-2 hrs ( time too short to make any products)
Beef	4-6 hrs (sufficient time to process meat)
Turkey	1/2-2 hrs
Chicken	1/2-1 hr

The color of fresh sausages, made from refrigerated meats, changed rapidly from a red color to a brownish-grey color when exposed to light, salt and oxygen. Fresh sausages produced with prerigor meat will maintain a red color in the presence of salt, light and oxygen for up to 6 days when refrigerated or a few weeks when kept frozen.

The next phase the meat enters is the aging “rigor mortis” (softening) phase. Due to some chemical reactions, the muscles will begin to contract and relax. The meat should not be processed in this phase because the meat will be tough.

The meat must be cooled slowly where it will remain in its aging phase to improve its tenderness, juiciness, taste, and flavor. The body of the animal should be cooled to an internal temperature of 40 ºF (4 ºC) or less within 36 hours after slaughter - but must not be allowed to freeze.

Pork	not needed
Veal	2- 3 days
Beef	4- 5 days
Lamb	7-10 days
Venison	7-10 days
Turkey	6-24 hrs
Chicken	4-6 hrs

There is no advantage to aging pork as it does not have the strong connective tissue. In other terms pork is not tough to begin with. The slaughtered animals are usually young and the meat is naturally tender. In fact aging of a pork will decrease the shelf life of the final product.

Warm beef can be deep frozen before it enters the “rigor mortis” phase, but to prevent it from losing its super binding qualities it has to be processed in this frozen state. That requires special heavy duty cutters and grinders that only commercial plants employ.

Normally we don’t think about these meat aging times, but they are essential to producing tender meats. Any hunter will tell you that to have tender meat you have to age deer for quite some time. You wouldn’t do it at 90º F, but deer season opens in the fall and most hunting is done up north anyway, so temperatures are favorable.

More on Poultry Aging - quoted from Factors Affecting Poultry Meat Quality-The University of Georgia:

Muscles that are deboned during early postmortem still have energy available for contraction. When these muscles are removed from the carcass, they contract and become tough. To avoid this toughening, meat is usually "aged" for 6 to 24 hours before deboning; however, this is costly for the processor. When poultry is deboned early (0 - 2 hours post-mortem), 50 to 80 percent of the meat will be tough (see figure below). On the other hand, if the processor waits 6 hours before deboning, 70 to 80 percent of the poultry meat will be tender.


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