Meat comes from animal muscles, but what we buy and eat is very different from the muscles! The meat we buy was muscle in the beginning and then it was transformed by precise chemical reactions.
Indeed, after the death of any animal (including fish!), the muscles naturally go through a series of biochemical reactions that gradually transform them into what we know as meat. In the culinary field, the entirety of these processes takes the name hanging.
From tough muscle to tender and edible meat
“Muscle” as such is not edible: it is extremely tough and unappetizing.
While living, animal cells derive energy primarily through a process called cellular respiration at the cost of consuming glucose and oxygen. After death, this process stops because the oxygen supply to the tissues is lost. Consequently, the cells, at least in the first minutes after the death of the animal, activate an alternative method to produce energy: glycolysis.
The advantage of the latter is to obtain ATP (which is the energy “currency” of the cell) from glucose even in the absence of oxygen. The problem is that lactic acid is also produced, which is the same substance that accumulates in our muscles following intense and prolonged effort, precisely because we fail to supply the cells with a sufficient amount of oxygen to continue the effort they are up against. As the name itself says, lactic acid is an organic acid and by accumulating in the tissues it acidifies them, giving an unpleasant taste to the meat.
In addition to this, muscle is inedible because it is extremely tough. Normally after contracting, the muscles relax because ATP moderates the distance between contractile fibers. However, glycolysis is a much less efficient process than cellular respiration and consumes the glucose reserves without producing a sufficient amount of energy. Therefore, in the absence of ATP, the muscles remain contracted.
The beginning of the hanging process
After a few hours the hanging process finally begins, mediated by the activation of proteolytic enzymes that cut myofibrils, thus causing the tenderisation of the tissues and an increase in the juiciness and flavor. At the same time, the pH rises.
Connective protein is an exception to the rule because it is not denatured by these enzymes. That is why the front cuts, rich in connective tissue, are the ones best suited for prolonged cooking (such as boiled): it is the prolonged action of the heat that breaks down those proteins that are still intact in the tissue. On the other hand, the rear cuts which lack collagen are already very tender after hanging and are therefore suitable for quicker and less intense cooking methods (grilling).
Two types of hanging
In the meat supply chain, hanging is an inevitable process and in slaughterhouses it is done basically according to two different methods.
Preferably, hanging is done dry. The meat is stored for days in refrigerator cells with temperatures between 0°C and 4°C and controlled humidity (80-95%). It is the most expensive process because it takes a long time and the meat loses weight as it releases its juices. But the result is a more prized product: the meat is very tender and the flavors are concentrated. This will also have implications for subsequent preparations, for example, the cooking method may be lighter than the one used for meat that is otherwise aged.
The second method of hanging is wet-ageing. The meat is placed in plastic and then vacuum sealed. The peculiarity is that the process in this case does not take place in a refrigerated environment but at temperatures between 18-20°C. Such high temperatures accelerate the proteolytic action of enzymes and thus allow a significant shortening of production times, ranging from 24-48 hours depending on the type of meat. However, environments must be sterilized to prevent parasitic growth. Moreover, packing in vacuum bags limits the loss of juice and therefore the weight reduction. The results is a quicker and cheaper process and for that reason it is increasingly preferred by the producers.
Hanging times and types of meat
Hanging times are very variable: they are influenced not only by the method used, as we have just seen, but also by the type of meat (breed, cut, age, type of feed, …).
For example, with dry-ageing, chicken, fish and young meat (like lamb) in general require a hanging time of about 24-hour. For beef, the process lasts at least 10-14 days. Even longer times are needed to age game meats.
In general, meats with long hanging times are considered more prized because, as the days pass, their tenderness and taste increase. When you get to hanging that exceeds 4 weeks, it results in both prized as well as very expensive meat.
Clearly it is not a process that you can perpetuate indefinitely because side effects such as drying and rotting fight against us.
Ultimately, hanging is a process that happens naturally and necessarily in the muscles of animal and transforms them into a tender, tasty, juicy product that can be consumed by us carnivores. Meat producers know hanging very well and know how much respecting the times and environmental conditions for a particular type of meat is essential to obtain a quality product.
Federica De Napoli