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]

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^[update], curing is instead mainly practiced 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.