User:AshleyOng716/Beef aging

Beef aging or ageing is a process of preparing beef for consumption by aging it, in order to break down the connective tissue within the meat. Common techniques for aging beef include dry aging and wet aging.

Dry-aged beef
Dry-aged beef is beef that has been hung or placed on a rack to dry for several weeks. After the animal is slaughtered and cleaned, it is hung as a full or half carcass. Primal (large distinct sections) or sub primal cuts, such as strip loins, rib eyes, and sirloin, are placed in a refrigerator unit, also known as a "hot box," which is an enclosure to age meat using high temperatures. This process involves considerable expense, as the beef must be stored near freezing temperatures. Sub primal cuts can be dry aged on racks either in specially climate-controlled coolers or within a moisture-permeable drybag. Moreover, only the higher grades of meat can be dry aged, as the process requires meat with necessary marbling, such as a large and evenly distributed fat content. Marbled meat serves as a primary indicator of meat quality. When marbled beef is cooked, the fat melts, increasing the meat's tenderness and juiciness and adding a buttery flavor. Because of this, dry-aged beef is seldom available outside of steak restaurants and upscale butcher shops or groceries. The key effect of dry aging is the concentration and saturation of the natural flavor, as well as the tenderization of the meat texture.

Dry-aged beef is typically not sold by most supermarkets in the U.S. today, because it takes time, the meat loses weight, and there is a risk of spoilage. Dry aging can take from 15 to 28 days, and typically up to a third or more of the weight is lost as moisture. This type of beef is served in higher-priced steakhouses and by select restaurants.

The process changes beef by two means. Firstly, moisture is evaporated from the muscle. The resulting process of desiccation creates a greater concentration of beef flavor and taste. Secondly, the beef's natural enzymes break down the connective tissue in the muscle, which leads to more tender beef.

Wet-aged beef
Wet-aged beef is beef that has typically been aged in a vacuum-sealed bag to retain its moisture. Since the 1970s, with the development of vacuum packing machines and related technology, this has become the dominant mode of aging beef in the US and UK. The beef is usually kept for a period of 4 to 10 days in wet aging. Modified-atmosphere packaging (MAP) is usually employed for the vacuum packaging of meat; typically between 60 and 80 percent oxygen to retain its appetizing color, with red meat such as beef needing a higher oxygen level than less vividly colored meat such as pork. The vacuum-packed beef is stored at a temperature of 32 °F to 45 °F (0 °C to 7.2 °C).

Physical
The process of dry aging usually also promotes the growth of certain fungal (mold) species on the external surface of the meat. This does not cause spoilage but rather forms an external "crust" on the meat's surface, which is trimmed off when the meat is prepared for cooking. These fungal species complement the natural enzymes in the beef by helping to tenderize and increase the flavor of the meat. During the entire process of dry aging beef, molds from the genus Thamnidium are found on the surface of the meat. Appearing as pale gray patches called ‘whiskers’ on the fatty parts of aged beef, Thamnidium is the most desirable mold due to its ability to release proteases and create collagenolytic enzymes. These enzymes penetrate the meat, breaking down the muscle and connective tissues, thus enhancing tenderness and taste. The growth of Thamnidium mold can start three weeks after the aging process has started.

Wet-aged beef produces yeast during its aging process. While the traditional types of yeast may not grow due to the anaerobic conditions, yeasts such as Candida, Pichia, and Zygosaccharomyces can grow in the absence of oxygen. While they don't cause rapid spoilage, yeasts can still impact the quality of the meat by altering its flavor, producing off-flavors like sourness, and affecting its texture and appearance.

Chemical composition
As beef ages, significant alterations in the levels of flavor precursors occur. In dry-aged beef, flavor enhancement comes from the accumulation of reducing sugars and the release of free amino acids and peptides. The degradation of ribonucleotides into compounds such as inosine monophosphate (IMP), guanosine monophosphate (GMP), inosine, and hypoxanthine also occurs during postmortem aging. Hydrolytic enzymes facilitate this transformation, including calpain proteinases, which break down muscle structures and generate peptides that contribute to flavor.

The resulting amino acids are known for imparting a sweet taste, whereas sulfur-containing amino acids like cysteine and methionine, along with glutamate and aspartate, produce umami flavors akin to those of monosodium glutamate (MSG). Carbohydrates break down into sugars, enhancing sweetness, while fats and phospholipids decompose into aromatic fatty acids. These chemical breakdowns create rich, nutty, and complex flavors characteristic of cooked dry-aged steaks.

The primary mechanism through which wet aging improves tenderness is enzymatic action. Within the muscle tissue of beef, there are natural enzymes called proteases. As the meat ages, the enzymes break down the protein structures in the muscle fibers, primarily targeting the myofibrillar proteins and the connective tissue components like collagen. The sealed environment keeps the meat in contact with its own juices, retaining active enzymes. These enzymes remain concentrated and effective due to minimal evaporation, breaking down tough proteins more efficiently. Additionally, the enzymatic activity can subtly alter the meat's pH, optimizing conditions for further protein breakdown, thus enhancing meat tenderness and chewability.

Environment
Dry aging can be done at home under refrigeration by three means: open air, with the presence of salt blocks, and with the use of a moisture-permeable drybag to protect the meat while it is aging. Since the mid-2010s, some chefs have experimented with a "quick" or "cheat" dry age by coating a cut of beef with ground koji (rice inoculated with Aspergillus oryzae) to simulate the effect of traditional dry aging; the results are not quite the same but can be achieved within 48 to 72 hours. The koji technique can also be applied to chicken and shrimp.

Wet aging beef at home can be done by sealing the beef in vacuum-sealed bags using a home vacuum sealer. Typically, beef should be wet aged in the refrigerator for a period of 7 to 21 days. Additionally, using a marinade injector to introduce flavors directly can further enrich the wet aging process.

Temperature
When dry aging using a moisture-permeable material, surface mold growth is not present, flavor and scent exchange within the refrigerated environment is not a concern, and trim loss of the outer hardened surface is measurably reduced. The growth of mold and the production of mycotoxins during the dry aging of beef is generally unlikely at temperatures below 5°C but can be produced at very low concentrations and very slowly. This is further reduced by the low water activity on the surface of dry-aged meat, which inhibits mycotoxin production by molds. Maintaining dry aging conditions between −0.5 to 3.0°C with a relative humidity (RH) of 75 to 85% for 14 to 35 days effectively minimizes the risk of mycotoxin development. Guidelines provided by regulatory bodies suggest that an air temperature in the dry aging chamber should be kept between −0.5 to 1.0°C, though temperatures up to 3°C may be permissible for aging periods ranging from 7–14 days. The recommended relative humidity is set at 75 to 85%, and an air velocity of 0.2–0.5 m/s should be maintained for optimal conditions throughout 14 to 35 days. The flavor and texture profile of the beef is similar in all dimensions to the traditional open-air-dry-aged results.

Wet-aged beef is most optimally stored at a temperature of 32 °F to 45 °F (0 °C to 7.2 °C). In a study conducted to determine the differences between dry aging and wet aging by lead researcher, Ana Paula da Silva Bernardo, it was found that higher storage temperatures did not affect the proportion of usable wet-aged meat, but there was an increase in Enterobacteriaceae counts at the higher temperature (7°C) compared to the lower one (2°C). This implies that while the lower temperature (2°C) is effective in controlling bacterial growth, the higher temperature (7°C) could pose risks of increased microbial activity, which could potentially affect the meat's quality and safety

Historically, it was common to store mutton or beef joints at room temperature for extended periods; even after the invention of refrigeration hanging sides of beef in large coolers for a few weeks as part of the processing was standard.

Safety
In a study led by Bernard Chege Mugo to trace the transmission of anthrax in the Kisumu East Sub County in Kenya, after assessing responses to the sudden death of an animal, it was discovered that various dry aging practices are employed. One of which included a technique, known locally as "Aliya," was described. This process involves cutting the meat into thin slices, which are then dried on an iron sheet roof for two weeks. This practice is believed to render the meat safe for human consumption, where butchers would then sell the tainted meat to consumers.

According to the Food and Drug Administration's (FDA), Bad Bug Book (2012), certain pathogens produce toxins that can remain active even after being subjected to heat. These are categorized as heat-stable toxins. For instance, enterotoxigenic Escherichia coli (ETEC) produces two types of toxins: heat-labile toxins (LT) and heat-stable toxins (ST). Heat-labile toxins, such as those from E. coli and cholera, can be inactivated by heat (e.g., boiling at 100°C for several minutes), whereas heat-stable toxins, like those produced by some strains of Staphylococcus aureus and Bacillus cereus, can resist these temperatures and remain active despite cooking, meaning that they cannot be destroyed by normal temperatures. Therefore, food contaminated with these toxins can still cause illness even if thoroughly dried.

Consumerism
Wet-aged beef is popular with producers, wholesalers, and retailers because it takes less time: typically only a few days and there is no moisture loss, so any given piece of meat sold by weight will have a higher value than a dry-aged piece where moisture loss is desired for taste at the expense of final weight.