Curing (food preservation)
Curing is any of various food preservation and flavoring processes of foods such as meat, fish and vegetables, by the addition of salt, with the aim of drawing moisture out of the food by the process of osmosis. Because curing increases the solute concentration in the food and hence decreases its water potential, the food becomes inhospitable for the microbe growth that causes food spoilage. Curing can be traced back to antiquity, and was the primary method of preserving meat and fish until the late 19th century. Dehydration was the earliest form of food curing.[1] Many curing processes also involve smoking, spicing, cooking, or the addition of combinations of sugar, nitrate, and nitrite.[1]
For post-harvest treatment of plant material, see Curing (vegetable preservation).
Meat preservation in general (of meat from livestock, game, and poultry) comprises the set of all treatment processes for preserving the properties, taste, texture, and color of raw, partially cooked, or cooked meats while keeping them edible and safe to consume. Curing has been the dominant method of meat preservation for thousands of years, although modern developments like refrigeration and synthetic preservatives have begun to complement and supplant it.
While meat-preservation processes like curing were mainly developed in order to prevent disease and to increase food security, the advent of modern preservation methods mean that in most developed countries today, curing is instead mainly practised for its cultural value and desirable impact on the texture and taste of food. For less-developed countries, curing remains a key process in the production, transport and availability of meat.
Some traditional cured meat (such as authentic Parma ham[2] and some authentic Spanish chorizo and Italian salami) is cured with salt alone.[3] Today, potassium nitrate (KNO3) and sodium nitrite (NaNO2) (in conjunction with salt) are the most common agents in curing meat, because they bond to the myoglobin and act as a substitute for oxygen,[4] thus turning myoglobin red.[4][5] More recent evidence shows that these chemicals also inhibit the growth of the bacteria that cause the disease botulism.[4] Yet, a 2018 study by the British Meat Producers Association determined that legally permitted levels of nitrite have no effect on the growth of the Clostridium botulinum bacteria which causes botulism, which in line with the UK’s Advisory Committee on the Microbiological Safety of Food opinion that nitrites are not required to prevent C. botulinum growth and extend shelf life.[6]
The combination of table salt with nitrates or nitrites, called curing salt, is often dyed pink to distinguish it from table salt.[7] Neither table salt, nor any of the nitrites or nitrates commonly used in curing (e.g., sodium nitrate [NaNO3],[8] sodium nitrite,[8] and potassium nitrate[9]) is naturally pink.
Necessity of curing[edit]
Meat decomposes rapidly if it is not preserved. The speed of decomposition depends on several factors, including ambient humidity, temperature, and the presence of pathogens. Most types of untreated meat cannot be kept at room temperature for lengthy periods before spoiling.
Spoiled meat changes color and exudes a foul odor. Ingestion can cause serious food poisoning. Salt-curing processes were developed in antiquity[10] in order to ensure food safety without relying on then unknown anti-bacterial agents.
The short shelf life of fresh meat does not pose significant problems when access to it is easy and supply is abundant. But in times of scarcity and famine, or when the meat must be transported over long distances, food preservation is powerful.
Curing significantly increases the length of time meat remains edible, by making it inhospitable to the growth of microbes.
Effect of meat preservation[edit]
On health[edit]
Since the 20th century, with respect to the relationship between diet and human disease (e.g. cardiovascular, etc.), scientists have conducted studies on the effects of lipolysis on vacuum-packed or frozen meat. In particular, by analyzing entrecôtes of frozen beef during 270 days at −20 °C (−4 °F), scientists found an important phospholipase that accompanies the loss of some unsaturated fat n-3 and n-6, which are already low in the flesh of ruminants.[50]
In 2015, the International Agency for Research on Cancer of the World Health Organization classified processed meat, that is, meat that has undergone salting, curing, fermenting, or smoking, as "carcinogenic to humans".[51][52][36]
On trade[edit]
The improvement of methods of meat preservation, and of the means of transport of preserved products, has notably permitted the separation of areas of production and areas of consumption, which can now be distant without it posing a problem, permitting the exportation of meats.
For example, the appearance in the 1980s of preservation techniques under controlled atmosphere sparked a small revolution in the world's market for sheep meat: the lamb of New Zealand, one of the world's largest exporters of lamb, could henceforth be sold as fresh meat, since it could be preserved from 12 to 16 weeks, which was a sufficient duration for it to reach Europe by boat. Before, meat from New Zealand was frozen, thus had a much lower value on European shelves. With the arrival of the new "chilled" meats, New Zealand could compete even more strongly with local producers of fresh meat.[53] The use of controlled atmosphere to avoid the depreciation which affects frozen meat is equally useful in other meat markets, such as that for pork, which now also enjoys an international trade.[54]