The process of adding some combination of salt (sodium chloride), nitrite or nitrate, and sugar to meat to prevent spoiling and enhance the flavor and color is called curing. Fully cured meat is defined as meat that can be left at room temperature for several months or more without spoiling or harboring disease-causing microbes. There are 2 basic ways to cure meat. In dry curing, the powdered or crystalline chemicals are rubbed directly onto the surface of the meat, or mixed into the meat. The second method is brine, wet, or pickle curing, the meat is treated with a solution of the curing chemicals dissolved in water. If the meat is immersed completely in the solution, it is called immersion brining, or more commonly just brining. If the solution is injected into the meat, it is called injection brining. The term brine is a very general one that means simply a solution of salt dissolved in water, regardless of the concentration; one or more other ingredients may or may not be added. Pickling refers specifically to a brine that has sugar added to it. More recently, the concept of flavor brining has gained popularity. This is not a true method of curing meat; rather, the main purpose is to add flavor and moisture to the meat. The fact that salt dissolved in water is used to help the process makes it a brine, but the salt concentration is not high enough to fully cure the meat. Flavor brining does help slow down bacterial action somewhat, however, so there is a partial curing benefit from this method.

Meat spoilage is caused by bacteria, some of which are harmful to humans. Disease-causing organisms are capable of growing at temperatures of 40-140F (5-60C), the “danger zone”, and can spoil meat within a few hours. In the millennia before refrigeration became widely available, the process of curing was used to preserve meat. It involves adding one or more of the following to the meat: common salt (sodium chloride), sodium nitrite, sugars, ascorbates (such as Vitamin C), and seasonings. While all of these substances have been found to play a role in curing meat, the key agents are salt and sodium nitrite. The curing process shuts down the growth of harmful bacteria, and has an additional helpful feature, too. Depending on the concentration of salt used, it can help to moisten and tenderize the meat.

Salt by itself is capable of fully curing meat only at very high concentrations, concentrations that most people would find too salty on most meats. About 200 years ago, saltpeter (potassium or sodium nitrate) was found to enhance the color of cured meat while preventing the growth of harmful bacteria at much lower concentrations than salt. Subsequently, it was shown that nitrates are converted to nitrites by harmless bacteria commonly present in the mouth and digestive tract, and that nitrite was the active ingredient in the curing process. This has led to numerous cure recipes that combine both salt and nitrites/nitrates. It also led to safety questions about the use of nitrates that we will cover later in this section. The bottom line, however, is that commercial cure preparations that use nitrites and nitrates are safe and effective to use, provided that the directions for use are carefully followed.

Interestingly, smoking food with wood also contributes several significant antibacterial compounds as well as chemicals that help prevent fat oxidation and the consequent development of rancid flavors. We smokers get a double benefit: wonderful flavors, and increased shelf-life of the finished product.

As mentioned above, it’s possible to dry or wet cure meat. They key is the concentration of salt and/or sodium nitrite. Although a few relatively uncommon harmful bacteria require a salt concentration of 20% to kill, most disease-causing microbes are inhibited at lower concentrations. For example, Listeria growth is blocked at 12% salt, Clostridium botulinum (the bacterium that causes the deadly food-borne-illness botulism) is inhibited at 10%, and Salmonella growth stops at 3% salt. For this reason, the most commonly found brine cures call for a salt concentration of about 15% (for an explanation of salt concentrations, see Technical Points, below). The most common and basic brining cure calls for 2 cups table salt + 2 cups sugar per gallon of water. As explained later, this is a 15% salt solution, and the sugar helps counteract the salty flavor and contributes to the antibacterial action of the brine.

The mechanisms of action used by salt and nitrite to prevent bacterial growth are well understood. In contrast, the physical and chemical mechanisms involved in moisturizing and tenderizing meat are not fully understood–in fact, there is considerable disagreement about it in the scientific community. However, everyone agrees that when the salt concentration inside the cells of muscle tissue is high enough, it causes some of the muscle tissue proteins to denature (cook) and this tenderizes the meat. Simultaneously, the amount of overall water content in the tissue is increased. A brined turkey or pork shoulder, for example, will generally increase in weight by 20% after brining; when the meat is cooked, about 10% of this moisture is lost, but the net water gain is still about 10%. Dry cured meats don’t increase in weight, but the real benefit of increasing salt concentration in the muscle tissue is that water is retained more tightly and thus requires a higher temperature to release it. Cooking “low and slow” allows dry cured meats to retain more of their moisture during cooking. compared to an uncured meat cooked exactly the same way. Finally, adding spices and herbs allows the flavor-enhancing molecules from these ingredients.

Seasoning/herbs:provide flavoring; certain compounds in herbs/spices are anti-bacterial, but probably not important at concentrations usually used.

One final note:

If you intend to cure your meat, as opposed to simply flavoring it, you must keep the salt concentration very close to 15%. Reducing the salt concentration, even by half, drastically reduces the antibacterial action. It is better to reduce the time of salt exposure, or rinse the meat well before cooking, rather than reduce the salt concentration, if your purpose is to preserve the meat and not just flavor it. If nitrites/nitrates are used, it is strongly recommended that you used a commercially available preparation and that you follow the usage directions carefully.

Not all meats benefit from brining or dry curing. Poultry, fish, and pork generally do benefit from brining or dry curing, but beef, lamb, duck and other meats high in fat content generally do not. That’s because they’re already moist and tender with strong flavor. Brining or dry curing won’t necessarily harm these meats, but you should brine them to change the flavor or to preserve them, not to moisturize or tenderize them. As with all rules, there are always exceptions, of course, as any Irishman fond of corned (salt cured) beef will attest, and who can forget chipped beef and pastrami!

In general, meats that are brine or dry cured should be rinsed well with fresh cold water before cooking. Flavor brined meats may or not need to be rinsed—follow the recipe directions. If you don’t rinse, the surface of the meat should be patted dry with paper towels or newspaper before cooking.

Often, “low and slow” cooking of brined poultry results in a rubbery skin. Patting a brined turkey or chicken dry with newspaper or paper towels and placing in the refrigerator uncovered for several hours or overnight (or until the skin feels tacky to the touch) will allow some moisture to evaporate and will allow the skin to brown better. Alternatively, finish cooking the bird after smoking it in the oven at 325-350F to crisp up the skin.

Brined meats usually cook faster than unbrined meats. While the scientific explanations for this vary, the take-home message is that you should start checking the internal temperature about 2/3 of the way through the normal cooking time.

One often-asked question is: How long should I brine? The answer depends on the weight and size of the meat, and to some extent upon one’s taste, but the following guidelines are offered to provide a good starting point:

Whole chicken: 4-8 hr.
Chicken parts: 1-3 hr
Whole turkey: 1 hour per pound.
Cornish game hens: 1-3 hr.
Capon: 4-8 hr.
Pork chops: 2-6 hr.
Pork loin (4-8 lb.): 4-8 hr.
Pork shoulder/ham: 1-3 days.
Fish: 6-12 hr/inch of thickness.

Cure mixtures (dry or brine) do not penetrate into frozen meat. Meat must be thawed for the chemicals to penetrate. Curing, whether dry or wet, should be carried out at 35-40F (2-5C). The lower temp ensures that the cure chemicals can penetrate the meat, and the higher temp limit is set to limit bacterial growth.

Do not make the mistake of substituting sodium or potassium nitrite/nitrate for salt (sodium chloride) when curing meat! The concentration of nitrite/nitrate needed for curing is much less than the concentration of salt required. Substituting nitrite/nitrate for salt in a cure mix can cause a fatal overdose of nitrite!Because of the danger of accidental overdose, it is strongly recommended that pure saltpeter not be used for curing unless the consumer has access to an analytical scale and knows how to use it. Instead, it is much safer to use one of the several commercial cure mixtures that are available, and to follow the manufacturer’s directions closely. Among the most popular are:

These cure mixtures combine sodium nitrite with salt. Use 1 oz. for every 25 lbs. of meat (that’s 1 teaspoon for every 5 lbs, of meat). These products are recommended for meats that require relatively short cures (several days or less) and will be cooked.

This is a combination of sodium nitrite and sodium nitrate. 1.6 ounces of this cure mix should be combined with 1 lb. of salt to produce the final cure mixture. The nitrate acts like a slow-release form of nitrite, so this mixture is recommended for meats that require very long cure times (weeks to months) and that do not require cooking, smoking, or refrigeration.

These products include TenderQuick, Sugar Cure, and Smoke Flavored Cure. All of them contain salt and nitrites as well as other ingredients. Follow the manufacturer’s instructions carefully.

A big flap arose about 25 years ago concerning smoking and BBQing. The concern was that nitrites or nitrates used to preserve meat might be converted to cancer-causing nitrosamines during the smoking and grilling process. Many scientific studies were conducted, and these were carefully analyzed by the National Academy of Science in the early 1980’s. They concluded that there was little if any cancer risk from nitrosamines arising from low temperature (less than 300F) smoking of food. Only at temps in excess of 600F is the formation of nitrosamines worrisome, and even then unusually large quantities of such meat would need to be ingested to increase the risk of cancer. However, the report left open the question of whether high levels of nitrate in meat could be converted to nitrosamines by naturally-occurring bacteria in the gut. Because of this potential health issue and the tendency of the meat industry to use relatively large quantities of nitrates to enhance meat color rather than for curing, the FDA banned the commercial use of nitrates in cooked meats in 1999, and limited the amount of nitrite that can be present in commercial meat like bacon or ham. However, the use of nitrates is still permitted commercially in small amounts in dry cured meats that are not cooked prior to sale. Individual purchase and use of nitrates is still allowed (see preceding paragraph).

Brining solutions often provide concentrations of salt in terms of either percentage (for example, 15% salt) or volume (for example, _ cup per quart). When salt concentration is given as a percentage, it is the weight/volume percentage. Thus, a 15% salt solution means 150 grams salt for every liter (1000 ml) of water. In non-metric terms, since a quart is 95% of a liter, and since 1 oz. equals 28.5 grams, we can see that 5 oz. of salt in 1 quart of water is very close to a 15% solution. Not all salt preparations weigh the same per unit volume. For example, table salt (regardless of producer) weighs very close to 10 oz. (285 grams) per cup of volume. Because of its somewhat coarser grain, Morton Kosher salt weighs about 8 (225 grams) oz. per cup. Diamond Crystal Salt only weighs 5.5 oz. (155 grams) per cup. Since there is almost a two-fold difference in the weight of the same volume of salt depending on how it is made, It is really problematic to determine the amount to use in a recipe unless the weight of salt is given (for example, “use 150 grams of salt per quart”) or the preparation and volume are given (“use _ cup Morton Kosher Salt per quart”). The 15% salt concentration (1/2 cup table salt, 5/8 cup Morton Kosher Salt, 1 cup Diamond Crystal Salt, or 150 grams salt per quart) is important since this is the salt concentration needed to cure meat).

The FDA and USDA have published the following data which may be useful when determining how to preserve, cure, and smoke cook meat:

Salt concentrations needed to kill:

Cooked meats should be cooled as rapidly as possible to below 40F and kept refrigerated. Food should cool down to 70F within 2 hrs after removing from heat, and should be cooled from 70F to 40F or below within another 4 hr.