Curing (food preservation)

Sea salt being added to raw ham to make Prosciutto.

Bag of Prague powder #1, also known as "curing salt" or "pink salt." It's typically a combination of salt and sodium nitrite, with the pink color added to distinguish it from ordinary salt.

Curing refers to various food preservation and flavoring processes, especially of meat or fish, by the addition of a combination of salt, nitrates, nitrite or sugar. Many curing processes also involve smoking, the process of flavoring, or cooking. The use of food dehydration was the earliest form of food curing.

History

Food curing dates back to ancient times, both in the form of smoked meat and as salt-cured meat. The Plains Indians used to hang their meat at the top of their teepees to increase the amount of smoke coming into contact with the food. It was discovered in the 1800s that salt mixed with nitrates (saltpeter) would color meats red, rather than grey, and consumers at that time then strongly preferred the red-colored meat.

Chemical actions

Salt

Table salt (sodium chloride) is the primary ingredient used in meat curing. Removal of water and addition of salt to meat creates a solute-rich environment where osmotic pressure draws water out of microorganisms, retarding their growth. Doing this requires a concentration of salt of nearly 20%. In addition, salt causes the soluble meat proteins to come to the surface of the meat particles within sausages. These proteins coagulate when the sausage is heated, helping to hold the sausage together. Finally, salt slows the oxidation process, effectively preventing the meat from going rancid.

Sugar

The sugar added to meat for the purpose of curing it comes in many forms, including honey, corn syrup solids, and maple syrup. However, with the exception of bacon, it does not contribute much to the flavor, but it does alleviate the harsh flavor of the salt. Sugar also contributes to the growth of beneficial bacteria like Lactobacillus by feeding them.

Nitrates and nitrites

Nitrosyl-heme

Nitrates and nitrites not only help kill bacteria, but also produce a characteristic flavor and give meat a pink or red color. Nitrate (NO₃⁻), generally supplied by sodium nitrate or potassium nitrate, is used as a source for nitrite (NO₂⁻). The nitrite further breaks down in the meat into nitric oxide (NO), which then binds to the iron atom in the center of myoglobin's heme group, reducing oxidation and causing a reddish-brown color (nitrosomyoglobin) when raw, and the characteristic cooked-ham pink color (nitrosohemochrome or nitrosyl-heme) when cooked. The addition of ascorbate to cured meat reduces formation of nitrosamines, but increases the nitrosylation of iron.

The use of nitrates in food preservation is controversial. This is due to the potential for the formation of nitrosamines when the preserved food is cooked at high temperature. The usage of either compound is therefore carefully regulated; for example, in the United States, the concentration of nitrates and nitrites is generally limited to 200 ppm or lower. However, they are considered irreplaceable in the prevention of botulinum poisoning from consumption of cured dry sausages by preventing spore germination.

A 2007 study by Columbia University suggests a link between eating cured meats and chronic obstructive pulmonary disease. Nitrites were posited as a possible cause.

Smoke

Main article: Smoking (cooking)

Meat can also be preserved by "smoking", which is to dry the meat in the presence of wood fire that produces large amounts of smoke. Drying meat while smoking it will also keep it tender. One method of smoking calls for a smokehouse with damp wood chips or sawdust. In North America, hardwoods such as hickory, mesquite and maple are commonly used for smoking, as are fruit woods such as apple, cherry and plum, and even corncobs.

Smoking originally kept flies from coming into contact with the meat, preventing the possibility of the laying of fly eggs and maggots until the meat was properly dried. The smoking can be done in combination with other curing methods such as salting, and helps seal the outer layer of the food being cured, making it more difficult for bacteria to enter. Slower and warmer smoking methods can be used to dehydrate the meat, further decreasing its susceptibility to bacteria, similar to jerky.

There are several types of smoking styles, but hot smoking, smoke roasting (pit barbecuing) and cold smoking are the most common. Smoke roasting and hot smoking actually cooks the food while cold smoking does not and is the oldest form of smoking meat for preservation, as the food is only exposed to the cooler smoke of the wood before it exits the smoking device.

See also

• Brining
• Charcuterie
• Curing salt
• Pickling
• Salting (food)
• Sausage making

References

• McGee, Harold. On Food and Cooking (revised). New York, NY: Scribner, 2004. ISBN 0-684-80001-2
• Bertolli, Paul. Cooking by Hand. New York, NY: Clarkson Potter/Publishers, 2003. ISBN 0-609-60893-2
• National Research Council Academy of Life Sciences. "The Health Effects of Nitrate, Nitrite and N-Nitroso Compounds". Washington DC: National Academy Press, 1981.
• Article in The Scientist, Volume 13, No. 6:1, Mar. 15, 1999 (registration required).
• Post on April 29, 2012 "Making Cured Meats"

External links

• National Center for Home Food Preservation - Curing and Smoking