Dry-Aging: Quality through Control
The transformation of muscle to meat is a battle between the muscle fibers and the enzymes and bacteria that they contain. The enzymes — called protense,— are only concerned with disintegrating the fatty and amino acids that make up muscle fibers. In order to stop them from ruining a beautiful steak, we have to control them.
After the animals are processed, blood stops transporting oxygen through the body, sending bodily systems that depend on oxygen for function to a screeching halt. This sudden jolt to the system causes widespread damage to cells throughout the body, causing chemical transformations that allow enzymes and bacteria to have free rein. While it sounds aggressive, it is a natural part of transforming muscle into meat and will occur with or without human intervention.
Muscle to MeatThere are a few different types of muscles. Smooth muscles make up most of the organs while cardiac muscles are found only in the heart. Because we are concerned with the creation of meat, we will focus on the bigger, heavier type of muscles, skeletal muscles. Skeletal muscles are robust and anchored by tendons to bone and are what creates motion. They will be referred to throughout this article as “muscles.”
Muscles are groups of elastic protein fibers called actin and myosin. When these fibers are stimulated by electrical impulses from the nervous system, they slide past one another causing groups of fibers to contract or relax in unison. This contraction is constantly happening in various degrees.
The energy for contraction come from the digestion of carbohydrates which are broken down into glucose. Some glucose is used immediately for energy, with excess glucose being stored in the muscles as glycogen. The muscles hold onto the glycogen until it is rapidly converted back into glucose to fuel large, powerful movements.
The use of glycogen for energy causes the production of lactic acid. Lactic acid is what causes the burning sensation in your muscles during exercise. Lactic acid build-up in the muscles is regulated by the movement of oxygen (via blood) through the muscles. After death, muscles continue to create lactic acid from small spasmodic movements, but due to the circulatory systems no longer pumping blood through the body, the lactic acid is left to build up in the muscles. This lowers the pH level in the muscles from a neutral 7.0 to a more acid 5.5-5.7. The acidic environment starts to denature the proteins, breaking cellular structure and releasing moisture and is the first occurrence of the tenderization of meat. This acidic environment is also beneficial because it slows the enzymatic and microbial activity until the muscles can be removed from the carcass and put into a controlled environment.
As the muscles continue to contract and relax, the pH level continues to drop and eventually results in an environment where the chemicals that allow the muscles to relax cannot operate, making it impossible for the muscle fibers to relax. This is called Rigor Mortis. At this point, the muscles are no longer living, functioning muscles and are on their way to becoming meat. If you were to eat the transitioning meat at this stage, it would be so dense you would not be able to chew it.
Note: There are several factors that contribute to quality meat besides controlling enzymatic activity during aging, such as humane living and processing conditions. We will address the latter two in a separate article and discuss why they are arguably the most important factors. Until then, let’s focus on enzymes.Rigor Mortis is identified by the awkward and unnatural poses of body parts that occurs when opposing muscles contract at the same time (ex: biceps/triceps). The actin and myosin fibers that we discussed earlier have now fused together. Once rigor mortis sets in, enzymes and bacteria left in the body are unregulated and can start to destroy proteins at will, a process that is called proteolysis. The two main enzymes that perform proteolysis are calpains and cathepsins. They work together to attack the muscles fibers, breaking them down to the point where they can no longer hold their contracted state.
Eventually, the enzymes and bacteria will dismantle enough proteins to offset rigor mortis and the muscle fibers to being to release, leaving the now meat in a much more tender state. Cathespin enzymes go on to break down the connective tissue and subsequent collagen to a state where it is easily hydrolyzed (broken down with water) allowing it to produce more gelatin when cooked. Breaking down the collagen structures also reduces the meat’s tendency to seize up during cooking, allowing it to retain more moisture. Breaking down the muscle fibers and connective tissues through proteolysis over various lengths of time is the difference between an edible steak and a great steak.
Aging with Intention for QualityAll beef must be aged to be palatable. The accepted minimum length of aging ranges from 3-12 days, but flavor development and overall quality starts to develop past the minimum range. Because aging take time, special equipment and storage space, as well as the loss of salable weight that comes from moisture loss, it is up to the producer to decide between methods and the right balance between time and taste that fits their operation. There are two types of aging that offer different results.
Dry-AgingDry Aging is the process of aging meat in an open environment while managing the amount of enzymatic and microbial activity through controlling the temperature, humidity and airflow around the meat. Dry-aging allows the surface of the meat to dry out and loss as much as 20% of the moisture content of the meat, concentrating the flavorful proteins into the moisture that is left. Though it reduces the volume of the meat, each bite packs more flavor.
During extended dry-aging, the meat develops a hard crust that houses fungi and other orgaisms such as Penicillium Nalgiovense, the white coating that is found on some salamis, Penicillium Roqueforti, the fungi that produces blue cheese, and Saccharomyces Cerevisiae, a yeast that is often used for bread and beer making. These fungi and molds are removed with the hard exterior as it’s trimmed off before selling and cooking but its presence during dry-aging leads to flavor development that has been described as nutty, buttery, spicy, earthy or sometimes slightly funky (in a good way).
Ideal conditions are necessary for meat to age without spoiling. Ideal temperature is between 34℉ and 38 ℉. This keeps the meat above freezing but lower than the food safety “Danger Zone.” At this temperature, the enzymes remain active but at a pace that doesn't let them completely deteriorate the meat. Humidity levels are kept between 70-80% to allow the surface meat to dry out to avoid microbial growth. Air is constantly circulated through dry aging rooms to promote even moisture loss on all surfaces through evaporation.
Optimum dry-aging length is somewhat subjective. Most quality meat providers who dry-age do so for at least 15 days. Others go for 28-35 days and sometimes only on their premium cuts. Fine steakhouse often list their dry-age steaks at 45 days up to 420 days as selling points. All sources that I have found, including personal experience, suggest that most dry-aged steaks that are older than 45 days take on flavor and texture notes that are increasingly different to what most consumers expect when eating a steak, sometimes to a fault.
Wet-AgingWet-aging is the method of aging meat in a protected, hermetically sealed environment, e.g., a vacuum-sealed plastic bag. Just like dry-aging, the enzymes continue to do their job of breaking down the muscle fibers to develop tenderness, but wet-aging does not concentrate the flavor through moisture loss.
Much like using artificial nitrates over naturally occurring nitrates during meat curing, large scale industrial meat processors have gravitated to wet-aging because it takes less time and is much cheaper. Wet-aging does not require controlled humidity and airflow as the plastic barrier protects the surface from microbial growth and since you are not expecting moisture loss or flavor development, meat can be sold sooner and at a higher weight because it has retained it's moisture. The cost of aging also drops with wet-aging because less equipment is needed being that humidity and air flow control are not necessary.
Aging at HomeAll over the internet there are videos and guides on dry-aging beef at home. Most say something along the lines of elevate the steak and wrap in cheese cloth for “airflow” and shove it in the back of your fridge then forget about it for 45 days. Don’t do this. It is not a good idea. Dry-aging at home is a good way to have a quality eating experience without having to pay the markup at a steakhouse, but the everyday refrigerator found in almost every kitchen in the world is not a conducive environment to protect against spoilage.
Every time the door opens, the temperature rises and the humidity drops (or rises depending on where you are). The occurrences of these fluctuations multiplies for every human you live with. When the door is closed, there is virtually no air flow. You would need to remove the steak regularly — hourly, not daily — to dry it off and rotate it to ensure that it dries evenly. The result will very often be an expensive, well-marbled steak that is soggy and spoiled, or dry on a few surfaces and spoiled on the rest.
Can dry-aging be done at home? Yes. Moderately successfully results can be found from dry-aging in a fridge secondary to your daily driver. Even in the secondary fridge, you are handcuffed by the humidity level and air circulation of that particular space, which can be assumed to be not ideal. Many people have built custom dry aging chambers with fans and humidity and temperature controls to great success, but often they fall short of the producers who have entire rooms specially built, designed and dedicated to the dry-aging process. In these large rooms, small fluctuations in temperature and humidity are not as consequential as in the small chambers. These facilities also have generations of fungi and molds that give specific flavors and qualities to each cut that is aged there.
Wet-aging can be done at home, but because it is optimized for speed and efficiency rather than flavor development, that refrigerator space would be better utilized for anything else.
At Buy Ranch Direct, we dry age all of our beef for 28 days because we feel that that is the amount of time that gives us the optimal flavor and texture with consistency. The entire carcasses are hung for that amount of time so that every cut, from our premium ribeyes to our ground beef have a deep beef flavor.