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Cured meat, ham, bacon, salami manufacturing
Cured meat refers to any meat that's been preserved through the removal of moisture. By eliminating moisture from meat, it takes on new textural properties that are not conducive to the growth of bacteria. The most common way of achieving this is by using salt to draw the moisture out and create a new, more shelf-stable substance known as “cured meat.”
People have been curing meat for centuries, mainly as a way to preserve their food. Especially before the days of refrigeration, most cultures found ways of curing meats through processes that remove moisture from the food through the use of salt. And you’ll still find specialty meat shops in Italy or other parts of the world that cure their meats in cellars or other cool environments that aren’t necessarily refrigerated.
While there are certain types of meats that will only cure properly if stored at room temperature, most meats should always be stored in cold environments, like walk-in refrigerators.
How to Cure Meat (ham, salami, bacon, prosciutto) with Salt
Salt was once more valuable than gold. Since it has the power to prolong the shelf life of otherwise perishable foods, it’s no wonder why. The centuries-old practice of curing foods with curing salt is simple to do and has been perfected over the years to create some of our favorite and well-known delicacies, from prosciutto to pepperoni.
Dry Curing Ham, Salami, Bacon, Prosciutto:
To dry cure meat with salt, cover it entirely in salt for a full day. In order to make sure the meat is completely covered, fill a container with salt, place the meat on top, and pour more salt over until it’s buried. You can also add some flavorings (like celery seed and black pepper) at this point, if you want.
If you’re worried about wasting so much salt, there is another (more modern) method you can try. First, weigh the meat. Apply 3% of that weight’s worth of salt onto the meat, covering evenly and thoroughly, then use a vacuum sealer to seal everything up and let it sit in the refrigerator for about 5 days. This technique is called “equilibrium curing.”
No matter which method you choose, the basic result should be pretty much the same. Once the meat has had ample time to sit, you’ll notice that the texture will change dramatically. It should become tougher and dryer.
If you notice a foul odor at any point in the process, that means that the salt was not properly applied and bacteria has begun to grow. There’s no real way to salvage meat after rot has begun, so if you find any indications of bacteria, it should be discarded right away.
After the meat is somewhat dehydrated, the fun part begins: adding flavors! There are endless combinations of herbs and spices you can use to create your very own signature cured meats, such as prosciutto. Simply shake off the majority of the salt (it’s okay if some stays on the outside) and coat the meat in your spice mixture.
Hang It to Dry Ham, Salami, Bacon, Prosciutto:
Once the spices have been applied, you can either wrap the meat in cheesecloth to keep the spices together or simply tie it with a series of butcher’s knots, using regular kitchen twine. The basic idea is to keep the meat in a tidy shape that’ll be easy to cut, while ensuring that air can circulate around the entire piece.
So, as soon as you have everything neatly tied, hang it in the fridge until it’s done. Between 40 and 33 degrees Fahrenheit is the proper temperature range for storing meat (without freezing it). Use a label maker to identify all your different meats—including the start weight and goal weight.
How Long Does It Take to Ham, Salami, Bacon, Prosciutto?
The meat should lose 35-40% of its weight by the end of the process, and the only way to tell when the meat is finished curing is to weigh it. Follow this formula to find what the final weight should be: beginning weight X 0.65= final weight goal. The amount of time it takes for the meat to cure depends entirely on the size of the meat. A small duck breast should take about 4-5 weeks. Large cuts of pork could take several months.
After you’ve left ample time for curing and the process is complete, it’s time to enjoy your creation! Use a meat slicer to slice the meat into the thinnest pieces possible (they should be translucent). You can put the pieces on a sandwich or simply serve them on a board with fruits, cheeses, and specialty mustard or jam. The end result should have a chewy texture and a perfect amount of salt and spice.
Cured Sausage Ham, Salami, Bacon, Prosciutto
Salami is one of the most popular kinds of cured sausage, and it’s been around for centuries. The main difference between cured sausage and other cured meats is that you actually combine the salt and seasonings with the meat in a meat grinder that best fits your needs, rather than simply coating the outside of a complete cut.
Making your own sausage isn’t difficult, but it can be time consuming. So why not get the most out of your efforts by curing it? One thing to keep in mind, though, is that many kinds of cured sausage must be stored at room temperature in order for the process to be effective, and that can require extra permits or special storage spaces in a commercial setting. But if you can manage the legal aspects, house-cured salami is a wonderful addition to a cheese and fruit board.
Commercial Meat Curing Ham, Salami, Bacon, Prosciutto Laws and Regulations
If you plan on curing your own meats, make sure you understand the laws and regulations of your municipality, as well as the Department of Health guidelines for your state. While meat and poultry regulations vary by country, state, and even city, some basic principles that apply throughout the nation include:
- Licenses - Most facilities that process meat, whether they're a slaughterhouse or delicatessen, need to obtain proper licenses through an application process.
- Inspections - Trained professionals will inspect meat processing facilities before production begins and will most likely check in periodically to ensure that everything meets their standards. There are different levels of inspectors: federal, state, and municipal.
- Facility - The layout of your facility is extremely important to plan out before you take on a meat curing endeavor because there are restrictions on the footpath permitted through the building, in order to reduce the risk of contamination. Access to potable water and proper drainage to sanitary sewage systems are essential.
- Separation of Products - Raw products must be kept separate from ready-to-eat items. Similarly, it is recommended that edible items be kept separate from inedible supplies, in order to better control the growth of bacteria in areas where food is kept.
Clearly, there are a lot of different methods for curing meat, but the same basic ingredients are important to all of them: salt, temperature, and time. Depending on your location, you may be able to cure meat in your existing space, or you could consider meat curing chambers to keep meat contained during the curing process. No matter if you’re looking to create a signature charcuterie to set your business apart from other eateries or if you’re simply hoping to extend the shelf life of the sausage that you painstakingly prepared, curing is a useful process to know.
Fidel Toldrá, in Reference Module in Food Science, 2016
Dry-cured meats constitute interesting meat products with relevant and particular flavor, color, and texture. This product is mainly produced in the Mediterranean area, China, and Eastern US States. The most important and well-known representative is dry-cured ham that has been produced for centuries, and up to this day, manufacturing relies on the basic stages of salting, drying, and ripening. The endogenous muscle enzymes are quite active during the process and are very relevant for the intense flavor development (Toldrá, 2006a, 2012). Drying is the basic characteristic of these products traditionally produced in areas with good climatic conditions, dry and sunny, such as the Mediterranean area, where they have been typically produced. These dry-curing processes were deeply studied since the last decades of the twentieth century, and more knowledge is now available on the chemical and biochemical changes happening during the process and the enzymatic mechanisms involved (Toldrá and Aristoy, 2010). The control of these reactions is necessary for the correct flavor formation but also for quality standardization (Toldrá, 1992).
This article describes the main types of dry-cured meats, focusing on dry-cured ham as the main representative. Its traditional manufacturing and the modern industrial processing and its sensory and nutritional qualities are described.
Curing & Smoking Meats Ham, Salami, Bacon, Prosciutto
2. Curing Foods
Curing is the addition to meats of some combination of salt, sugar, nitrite and/or nitrate for the purposes of preservation, flavor and color. Some publications distinguish the use of salt alone as salting, corning or salt curingand reserve the word curing for the use of salt with nitrates/nitrites. The cure ingredients can be rubbed on to the food surface, mixed into foods dry (dry curing), or dissolved in water (brine, wet, or pickle curing). In the latter processes, the food is submerged in the brine until completely covered. With large cuts of meat, brine may also be injected into the muscle. The term pickle in curing has been used to mean any brine solution or a brine cure solution that has sugar added.
2.1. Salting / Corning
Salt inhibits microbial growth by plasmolysis. In other words, water is drawn out of the microbial cell by osmosis due to the higher concentration of salt outside the cell. A cell loses water until it reaches a state first where it cannot grow and cannot survive any longer. The concentration of salt outside of a microorganism needed to inhibit growth by plasmolysis depends on the genus and species of the microorganism. The growth of some bacteria is inhibited by salt concentrations as low as 3%, e.g., Salmonella, whereas other types are able to survive in much higher salt concentrations, e.g., up to 20% salt for Staphylococcus or up to 12% salt for Listeria monocytogenes (Table 5.3.). Fortunately the growth of many undesirable organisms normally found in cured meat and poultry products is inhibited at relatively low concentrations of salt (USDA FSIS 1997a).
Salting can be accomplished by adding salt dry or in brine to meats. Dry salting, also called corning originated in Anglo-Saxon cultures. Meat was dry-cured with coarse "corns" or pellets of salt. Corned beef of Irish fame is made from a beef brisket, although any cut of meat can be corned. Salt brine curing involves the creation of brine containing salt, water and other ingredients such as sugar, erythorbate, or nitrites. Age-old tradition was to add salt to the brine until it floated an egg. Today, however, it is preferred to use a hydrometer or to carefully mix measured ingredients from a reliable recipe. Once mixed and placed into a suitable container, the food is submerged in the salt brine. Brine curing usually produces an end product that is less salty compared to dry curing. Injection of brine into the meat can also speed the curing process.
2.2. Nitrate/ Nitrite Curing
Most salt cures do not contain sufficient levels of salt to preserve meats at room temperature and Clostridium botulinum spores can survive. In the early 1800's it was realized that saltpeter (NaNO3 or KNO3) present in some impure curing salt mixtures would result in pink colored meat rather than the typical gray color attained with a plain salt cure. This nitrate/nitrite in the curing process was found to inhibit growth of Clostridium. Recent evidence indicates that they may also inhibit E. coli, Salmonella, and Campylobacter if in sufficient quantities (Condon 1999, Doyle 1999).
Several published studies indicated that N-nitrosoamines were considered carcinogenic in animals. For this reason, nitrate is prohibited in bacon and the nitrite concentration is limited in other cured meats. In other cured foods, there is insufficient scientific evidence for N-nitrosamine formation and a link to cancer (Pariza 1997).
- For more information, please refer to the following resources:
- Examination of Dietary Recommendations for Salt-Cured, Smoked, and Nitrite-Preserved Foods (Pariza 1997).
- Nitrite in Meat (Epley et al.1992).
- Safety of Cured Pork Products (Cassens 2001).
2.3. Cure Mixtures
For the home food preserver, measuring small batches of cure for nitrites or nitrates would require an analytical scale that few consumers have access to. Therefore, some manufacturers sell premixed salt and nitrate/nitrite curing mixes for easy home use. Caution is needed when using pure saltpeter instead of commercially prepared mixes, since accidental substitution of saltpeter for table salt in recipes can result in lethal toxic levels (Borchert and Cassens 1998).
Some examples of commercially prepared cures include:
2.3.1. Prague Powder #1, Insta Cure, or Modern Cure.
This cure contains sodium nitrite (6.25%) mixed with salt (93.75%). Consumers are recommended to use 1 oz. for every 25 lb. of meat or one level teaspoon of cure for 5 lb. of meat.
2.3.2. Prague Powder #2
This mix is used for dry cured meats that require long (weeks to months) cures. It contains 1 oz. of sodium nitrite and 0.64 oz. of sodium nitrate. It is recommended that this cure be combined with each 1 lb. of salt and for products that do not require cooking, smoking, or refrigeration. This cure, which contains sodium nitrate, acts like a time-release cure, slowly breaking down into sodium nitrite, then into nitric oxide. The manufacturer recommends using 1 oz. of cure for 25 lbs. of meat or one level teaspoon of cure for 5 lbs. of meat.
Many individual manufacturers and commercial sausage makers produce curing mixtures, often combining sugar and spices with the salt and nitrite/nitrates. It is important that consumers follow manufacturer directions carefully.
For more information, please refer to the following products, companies, and available resources:
- Morton Salt Meat Curing Products (Morton Salt Co. 2001). Their products include Tender Quick, Sugar Cure, and Smoke Flavored Sugar Cure.
- Curing Products (Mandeville Co. 2001). Their products include Poultry Cure, Quick Cure, Golden Cure, Complete Cure, Maple Flavor Cure, and Myco Pickle.
2.3.4. Saltpeter, Sodium or Potassium Nitrate
Commercially, nitrate is no longer allowed for use in curing of smoked and cooked meats, non-smoked and cooked meats, or sausages (US FDA 1999). However, nitrate is still allowed in small amounts in the making of dry cured uncooked products. Home food preservers should avoid the direct use of this chemical and opt for the mixtures described above.
2.4. Combination Curing
Some current recipes for curing have vinegar, citrus juice, or alcohol as ingredients for flavor. Addition of these chemicals in sufficient quantities can contribute to the preservation of the food being cured.
2.5. Flavor of Cured Meats
Besides preservation, the process of curing introduces both a desired flavor and color. Cured meat flavor is thought to be a composite result of the flavors of the curing agents and those developed by bacterial and enzymatic action.
Because of the amount of salt used in most curing processes, the salt flavor is the most predominant.
Sugar is a minor part of the composite flavor, with bacon being an exception. Because of the tremendous amount of salt used, sugar serves to reduce the harshness of the salt in cured meat and enhance the sweetness of the product (ie. Sweet Lebanon Bologna). Sugar also serves as a nutrient source for the flavor-producing bacteria of meat during long curing processes.
2.5.3. Spices and Flavor Enhancers
Spices add characteristic flavors to the meats. Recent studies have suggested that some spices can have added preservative effects (Doyle 1999). However, the quantities of spice needed to achieve these effects may be well beyond the reasonable quantities of use.
Nitrites and nitrate conversion to nitrite provide the characteristic cured flavor and color (see below).
The tangy flavor observed in dry fermented sausages, such as pepperoni, is the result of bacterial fermentation or the addition of chemicals such as glucono-δ(delta)-lactone.
The process of smoking gives the product the characteristic smoky flavor that can be varied slightly with cure recipes and types of smoke used.
2.6. Color of Cured Meats
A high concentration of salt promotes the formation of an unattractive gray color within some meat. Nitrate when used for some dry-cured, non-cooked meats is reduced to nitrite then to nitric oxide, which reacts with myoglobin (muscle pigment) to produce the red or pink cured color. If nitrite is used as the curing agent, there is no need for the nitrate reduction step, and the development of the cure color is much more rapid.
Generation of Nitric Oxide (NO):
- Sodium nitrate is reduced to sodium nitrite by microorganisms such as Micrococcus spp. present on meats.
- Sodium nitrite is reduced to nitrous acid in the presence of an acidic environment (e.g., by fermentation or by addition of glucono-δ(delta)-lactone).
- Nitrous acid forms nitric oxide. Nitric oxide reacts with myoglobin (meat pigments) to form a red color.
The time required for a cured color to develop may be shortened with the use of cure accelerators, e.g., ascorbic acid, erythorbic acid, or their derivatives. Cure accelerators tend to speed up chemical conversion of nitric acid to nitric oxide. They also serve as oxygen scavengers, which slow the fading of the cured meat color in the presence of sunlight and oxygen. Some studies have indicated that cure accelerators have antimicrobial properties, especially for the newly emerging pathogens like E. coli O157:H7 and Listeria monocytogenes (Doyle 1999). Since cure accelerators are rarely used in home curing, this information needs further review or research to determine what benefits home curing would have by using certain cure accelerators.
K. Prabhakar, in Encyclopedia of Food Microbiology, 1999
Role of Packaging
Cured and smoked meats are packaged for the sake of retail sale convenience and attractive presentation to consumers. Keeping quality is improved as post-processing contamination is avoided. For better consumer appeal, cured meats require to be packaged in transparent films but exposure to light and the presence of salt, initiate oxidation of fat and destabilization of cured pigment. Hence the usual practice is to ensure that one side (exposed in the display cabinet) of the package is of opaque material and the non-exposed transparent side is shown to the buyer at the time of sale only. Vacuum packaging is a subsequent development. It protects the bright red colour from oxidation due to absence of oxygen and enhances keeping quality by at least two weeks at refrigeration temperatures. Cooked cured hams which are exposed to pasteurization temperatures only are canned in brine for enhanced stability.
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. Many curing processes also involve smoking, spicing, cooking, or the addition of combinations of sugar, nitrate, and nitrite.
Slices of beef in a can.
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 lesser-developed countries, curing remains a key process in the production, transport and availability of meat.
Some traditional cured meat (such as authentic Parma ham and some authentic Spanish chorizo and Italian salami) are cured with salt alone. Today, potassium nitrate and sodium nitrite (in conjunction with salt) are the most common agents in curing meat, because they bond to the myoglobin and act as a substitute for the oxygen, thus turning myoglobin red. More recent evidence shows that these chemicals also inhibit the growth of the bacteria that cause the disease botulism. 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.
The combination of table salt with nitrates or nitrites, called curing salt, is often dyed pink to distinguish it from table salt. Neither table salt, nor any of the nitrites or nitrates commonly used in curing (e.g., sodium nitrate, sodium nitrite, and potassium nitrate) is naturally pink.
Necessity of curing
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 in order to ensure food safety without relying on artificial 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 carried over long voyages, the usefulness of food preservation is obvious.
Curing significantly increases the length of time meat remains edible, by making it inhospitable to the growth of microbes.
A survival technique since prehistory, the preservation of meat has become, over the centuries, a topic of political, economic, and social importance worldwide.
Several sources describe the salting of meat in the ancient Mediterranean world. Diodore of Sicily in his Bibliotheca historica wrote that the Cosséens in the mountains of Persia salted the flesh of carnivorous animals. Strabo indicates that people at Borsippa were catching bats and salting them to eat. The ancient Greeks prepared tarichos (τάριχος), which was meat and fish conserved by salt or other means.[a] The Romans called this dish salsamentum – which term later included salted fat, the sauces and spices used for its preparation. Also evidence of ancient sausage production exists. The Roman gourmet Apicius speaks of a sausage-making technique involving œnogaros (a mixture of the fermented fish sauce garum with oil or wine). Preserved meats were furthermore a part of religious traditions: resulting meat for offerings to the gods was salted before being given to priests, after which it could be picked up again by the offerer, or even sold in the butcher's.
A trade in salt meat occurred across ancient Europe. In Polybius's time, the Gauls exported salt pork each year to Rome in large quantities, where it was sold in different cuts: rear cuts, middle cuts, hams, and sausages. This meat, after having been salted with the greatest care, was sometimes smoked. These goods had to have been considerably important, since they fed part of the Roman people and the armies. The Belgae were celebrated above all for the care which they gave to the fattening of their pigs. Their herds of sheep and pigs were so many, they could provide skins and salt meat not only for Rome, but also for most of Italy. The Ceretani of Spain drew a large export income from their hams, which were so succulent, they were in no way inferior to those of Cantabria. These tarichos of pig became especially sought, to the point that the ancients considered this meat the most nourishing of all and the easiest to digest.
In Ethiopia, according to Pliny, and in Libya according to Saint Jerome, the Acridophages (literally, the locust-eaters) salted and smoked the crickets which arrived at their settlements in the spring in great swarms and which constituted, it was said, their sole food.
In Europe, medieval cuisine made great use of meat and vegetables, and the guild of butchers was amongst the most powerful. During the 12th century, salt beef was consumed by all social classes. Smoked meat was called carbouclée in Romance tongues and bacon if it was pork.
The Middle Ages made pâté a masterpiece: that which is, in the 21st century, merely spiced minced meat (or fish), baked in a terrine and eaten cold, was at that time composed of a dough envelope stuffed with varied meats and superbly decorated for ceremonial feasts. The first French recipe, written in verse by Gace de La Bigne, mentions in the same pâté three great partridges, six fat quail, and a dozen larks. Le Ménagier de Paris mentions pâtés of fish, game, young rabbit, fresh venison, beef, pigeons, mutton, veal, and pork, and even pâtés of lark, turtledove, cow, baby bird, goose, and hen. Bartolomeo Sacchi, called Platine, prefect of the Vatican Library, gives the recipe for a pâté of wild beasts: the flesh, after being boiled with salt and vinegar, was larded and placed inside an envelope of spiced fat, with a mélange of pepper, cinnamon and pounded lard; one studded the fat with cloves until it was entirely covered, then placed it inside a pâte.
In the 16th century, the most fashionable pâtés were of woodcock, au bec doré, chapon, beef tongue, cow feet, sheep feet, chicken, veal, and venison. In the same era, Pierre Belon notes that the inhabitants of Crete and Chios lightly salted then oven-dried entire hares, sheep, and roe deer cut into pieces, and that in Turkey, cattle and sheep, cut and minced rouelles, salted then dried, were eaten on voyages with onions and no other preparation.
Early modern era
During the Age of Discovery, salt meat was one of the main foods for sailors on long voyages, for instance in the merchant marine or the navy. In the 18th century, salted Irish beef, transported in barrels, were considered finest.
Scientific research on meat by chemists and pharmacists led to the creation of a new, extremely practical product: meat extract, which could appear in different forms. The need to properly feed soldiers during long campaigns outside the country, such as in the Napoleonic Wars, and to nourish a constantly growing population often living in appalling conditions drove scientific research, but a confectioner, Nicolas Appert, in 1795 developed through experimentation a method which became universal and in one language bears his name: airtight storage, called appertisation in French.
With the spread of appertisation, the 19th-century world entered the era of the "food industry", which developed new products such as canned salt meat (for example corned beef). The desire for safer food led to the creation of the Pure Food and Drug Act in 1906, followed by the national agencies for health security and the establishment of food traceability over the course of the 20th century. It also led to continuing technological innovation.
In France, the summer of 1857 was so hot that most butchers refused to slaughter animals and charcutiers lost considerable amounts of meat, due to inadequate conservation methods. A member of the Academy of Medicine and his son issued a 34-page summary of works printed between 1663 and 1857, which proposed some solutions: not less than 91 texts exist, of which 64 edited for only the years between 1851 and 1857.
Main article: Salting (food)
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, slowing down their growth. Doing this requires a concentration of salt of nearly 20%. In addition, salt causes the soluble proteins to come to the surface of the meat that was used to make the sausages. These proteins coagulate when the sausage is heated, helping to hold the sausage together.
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 such as Lactobacillus by feeding them.
Nitrates and nitrites
Nitrates and nitrites extend shelf life, help kill bacteria, produce a characteristic flavor and give meat a pink or red color. Nitrite (NO−
2) is generally supplied by sodium nitrite or (indirectly) by potassium nitrate. Nitrite salts are most often used to accelerate curing and impart a pink colour. Nitrate is specifically used only in a few curing conditions and products where nitrite (which may be generated from nitrate) must be generated in the product over long periods of time.
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 (see below), but increases the nitrosylation of iron.
The use of nitrite and nitrate salts for meat in the US has been formally used since 1925. Because of the relatively high toxicity of nitrite (the lethal dose in humans is about 22 mg/kg of body weight), the maximum allowed nitrite concentration in US meat products is 200 ppm. Plasma nitrite is reduced in persons with endothelial dysfunction.
Nitrite-containing processed meat is associated with increased risk of developing colorectal cancer. Adding nitrites to meat has been shown to generate known carcinogens such as nitrosamines, N-Nitrosamides and nitrosyl-heme, resulting from nitrosylation reactions; the World Health Organization (WHO) advises that each 50 g (1.8 oz) of "processed meats" eaten a day would raise the risk of getting bowel cancer by 18% over a lifetime; "processed meat" refers to meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation. The World Health Organization's review of more than 400 studies concluded, in 2015, that there was that there was sufficient evidence that "processed meats" caused cancer, particularly colon cancer; the WHO's International Agency for Research on Cancer (IARC) classified "processed meats" as carcinogenic to humans (Group 1).
The use of nitrites in food preservation is highly controversial due to the potential for the formation of nitroso-compounds such as nitrosamines, N-Nitrosamides and nitrosyl-heme. When the meat is cooked at high temperatures, nitrite-cured meat products can also lead to the formation of nitrosamines. The effect is seen for red processed meat, but not for white meat or fish. Nitrates and nitrites may cause cancer and the production of carcinogenic nitrosamines can be potently inhibited by the use of the antioxidants Vitamin C and the alpha-tocopherol form of Vitamin E during curing. Under simulated gastric conditions, nitrosothiols rather than nitrosamines are the main nitroso species being formed. The use of either compound is therefore regulated; for example, in the United States, the concentration of nitrates and nitrites is generally limited to 200 ppm or lower.
While the meat industry considers nitrites irreplaceable because they speed up curing and improve color, they have no effect on the growth of the bacteria which causes botulism: an extremely rare disease (less than 1000 cases reported worldwide per year), and almost always associated with home preparations of food storing. All Parma ham has been made without nitrites since 1993, and was reported in 2018 to have caused no cases of botulism.
Furthermore, while the FDA has set a limit of 200 ppm of nitrates for cured meat, they are not allowed and not recognized as safe in most other foods, even foods that are not cooked at high temperatures, such as cheese.
Nitrites from celery
Processed meats without "added nitrites" may be misleading as they may be using naturally occurring nitrites from celery instead.
A 2019 report from Consumer Reports  found that using celery (or other natural sources) as a curing agent introduced naturally occurring nitrates and nitrites. The USDA allows the term “uncured” or “no nitrates or nitrites added” on products using these natural sources of nitrites, which provides the consumer a false sense of making a healthier choice. The Consumer Reports investigation also provides the average level of sodium, nitrates and nitrites found per gram of meat in their report.
Consumer Reports and the Center for Science in the Public Interest filed a formal request to the USDA to change the labeling requirements in 2019. 
Main article: Smoking (cooking)
Meat can also be preserved by "smoking". If the smoke is hot enough to slow-cook the meat, this 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 the wood from fruit trees such as apple, cherry, and plum, and even corncobs.
Smoking helps seal the outer layer of the food being cured, making it more difficult for bacteria to enter. It can be done in combination with other curing methods such as salting. Common smoking styles include hot smoking, smoke roasting (pit barbecuing) and cold smoking. Smoke roasting and hot smoking cook the meat while cold smoking does not. If the meat is cold smoked, it should be dried quickly to limit bacterial growth during the critical period where the meat is not yet dry. This can be achieved, as with jerky, by slicing the meat thinly.
Effect of meat preservation
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.
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".
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. 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.