Curing
Corning , in Austria and Bavaria also Suren called, is the treatment of food fish , meat - and sausages with salt and with sodium - or potassium salts of nitric acid ( sodium or potassium nitrate ) or nitrous acid ( sodium or potassium nitrite ), the so-called curing agents . In addition, there may be other curing additives such as ascorbic acid , types of sugar and gluconic acid delta-lactone , as well as spices . If no curing substances are used, one does not usually speak of curing, but of salts , but the traditional usage is inconsistent. Most of the products that are cured in one piece are pork , with beef and veal cured to a lesser extent . The proportion of cattle is higher for products made from minced meat.
The purpose of curing is to protect the goods from microbial spoilage and thus to make them durable , to change the red meat color and make it heat-resistant - the so-called reddening - and to give it a characteristic aroma . Preservation is only effective against some bacteria, and only to a limited extent; it is no longer in the foreground compared to color and aroma development. At the same time, in conjunction with other conservation measures such as drying , smoking and heating, it ultimately contributes to the production of long-life foods. The reddening, the cured aroma and the inhibition of bacterial growth, as far as it goes beyond the very limited effect of pure salting, are caused exclusively by the nitrite, not the nitrate. Nitrate curing is only possible because nitrate is enzymatically reduced to nitrite by certain microorganisms . It only works if the cured food matures unheated for a long enough time so that the cured flora can develop.
Word origin
The word pickle (masculine, for brine), from which the other forms are derived, comes from the Low German word pekel , and is related to the Dutch pekel and the English pickel , all of which refer to brine. Foerste , and with reference to this, for example, the Kluge , derives it from a reconstructed vulgar Latin form pīccāre ("sting"), so that it would be related to piquant , de Vries from ancient Greek πικρός pikrós , German , sharp, pointed, bitter 'stabbing' . Occasional popular declarations that a Dutchman named Beukel invented curing are not considered in linguistic literature and are probably legends. The synonymous Sur , hence suren and Surfleisch , comes from the word pissed off.
history
Meat and meat products were already preserved by the Babylonians , Sumerians and Romans by smoking and salting. This is from the Roman writer Marcus Terentius Varro (116-27 BC) and from the Roman cookbook with the help of Apicius ' " De re coquinaria " (2nd half of the 1st century BC with additions up to around 400) AD, copies and new editions up to modern times). Herodotus reports on salting the flesh in ancient Egypt .
Salting is a very old preservation method that was very common on long voyages so that meat was also available as a source of protein on the high seas. This conservation method is already mentioned in Hanseatic documents around 1300.
In 1891 the chemist Eduard Polenske (1849–1911) discovered that nitrate in meat is converted to nitrite by bacteria. Karl Bernhard Lehmann and Karl Kißkalt discovered in 1899 that nitrite is responsible for the reddish color of the cured food. In 1901, John Scott Haldane proved that the reddish color is the result of a chemical reaction between the nitroso group and the hemoglobin contained in meat . In 1929 it was found that nitrites slowed the growth of bacteria.
Active ingredients
In addition to table salt, the substances used in curing are the curing substances, nitrite and nitrate, which actually distinguish curing from pure salting. In addition, so-called curing additives are used, namely:
- Ascorbic acid or its sodium salt as a reducing agent
- Gluconic acid delta-lactone as an acidulant
- Types of sugar to favor the curing flora
In addition, the activity of various useful microorganisms that develop naturally in meat and, on the one hand, reduce nitrate to nitrite, and on the other hand, contribute to acidification and flavor formation, is of particular importance. The individual factors are described in more detail below.
Table salt
In terms of quantity, table salt is the most important of the chemical compounds that are added to meat during curing. In high concentrations, it removes water from the cell plasma of the microorganisms through osmosis and thus affects their life processes, whereby their growth is delayed or completely succumbs or the organisms even die. At 1.5–5%, the salt concentrations in edible meat products are typically so low that they can only delay bacterial growth, but not stop it. Therefore, pure salting is insufficient as a preservation method for ready-to-eat products and is only suitable for heavily salted intermediate products , the salt content of which is diluted again before the final processing for consumption. However, the growth retarding effect of table salt also works at lower concentrations and contributes to preservation.
nitrate
Potassium nitrate (colloquially simply "saltpeter") and sodium nitrate (Chile's nitrate) have no germ-inhibiting effect as such. They also do not cause any reddening or the development of a cured aroma. However, nitrate-reducing bacteria can convert nitrate to nitrite by producing nitrite reductase ; these are primarily many strains of micrococci , but also Enterococcus faecium . However, the prerequisite for their effectiveness is that the meat is cured long enough so that the microorganisms can grow and metabolize the nitrate.
nitrite
Potassium or sodium nitrite are either formed enzymatically during the curing process, as described, by the activity of the cured flora, or added directly to the cured goods. In contrast to table salt and nitrate, they have a significant bactericidal and bacteriostatic effect, which is effective against different types of bacteria. Nitrate-reducing bacteria are relatively insensitive; this includes the desired nitrate reducers in the pickling flora, particularly micrococci, but also the pathogenic Staphylococcus aureus . Significantly more effective is nitrite but against important spoilage: pseudomonas , coliform bacteria including Escherichia coli , Bacillus - and Clostridium species.
It has been shown that the growth-inhibiting effect of nitrite is stronger the more acidic the environment. It can be said, for example, that lowering the pH value by one unit reduces the amount of nitrite required to one tenth. This is probably due to the fact that the actual germ-inhibiting effect comes from the undissociated nitrous acid, the proportion of which increases as the pH value falls. Above pH 5.5, Staphylococcus aureus is no longer sufficiently inhibited at the nitrite concentrations that are possible during curing in order to produce a durable meat preserve without further preservation methods.
Furthermore, nitrite causes the reddening of the meat. The red or pink raw meat gets its color from the muscle protein myoglobin , which is not heat-resistant. When heated, it denatures to metmyoglobin , the meat turns gray-brown. In contrast, the addition of nitrite converts the myoglobin into nitrosomyoglobin, which under heat changes into a stable red form, the nitrosomyochromogen. Therefore, Kasseler, for example, does not turn gray when cooked. Reddening is also significantly favored by an acidic environment. By reacting with various muscle components, such as water-soluble proteins, the nitrite also contributes to the formation of an aroma that is typical of salted meat products.
The addition of nitrite must be strictly limited and is subject to legally stipulated limit values because nitrite is toxic. Traditionally, nitrite curing salt with a maximum of 0.5% sodium nitrite was permitted in Germany and up to 0.6% in Austria and Switzerland.
Ascorbic acid
Ascorbic acid (vitamin C) or sodium ascorbate reduces nitrite to nitric oxide and thereby increases the reddening, so that a considerably higher proportion of the myoglobin in the meat turns into cured red, namely up to 90% - without the addition of ascorbic acid, a maximum of two thirds are converted even under favorable conditions . In addition, it accelerates the reddening reaction, thus allowing the curing process to be shortened, and its antioxidant effect stabilizes the curing red. In addition, the addition of ascorbic acid results in lower residual nitrite levels in the end product and suppresses the formation of carcinogenic nitrosamines.
Gluconic acid delta-lactone
Gluconic acid delta-lactone has a strong acidic reaction; it only serves to lower the pH value. As already mentioned, a low pH-value increases the germ-inhibiting effect of the nitrite as well as the reddening. In addition, acidification also contributes to the general preservation of the product by inhibiting the growth of spoilage pathogens, as is the case with other foods that are preserved by acidification. However, an overly sour taste is not desired for salted meat, so that the addition of the acidulant is limited.
Types of sugar
The addition of various sugars, especially glucose and sucrose , as well as hydrolysis products of starch (dry starch syrup, “crystal pure”), serve as food for the curing flora, especially for the acid-producing organisms. The sugar is enzymatically broken down by these and thus contributes to acidification. Additions of up to 1.5% are common; excessive added sugar leads to over-acidification of the product.
Curing flora
The desirable, harmless microorganisms that develop in meat during the curing process include, in addition to the nitrate-reducing bacteria, mainly acid formers, which enzymatically ferment carbohydrates into lactic acid . These include lactobacilli , atypical streptobacteria, Leuconostoc and Pediococcus . But other bacteria and yeasts have also been detected in the curing flora. By breaking down not only carbohydrates but also fats and proteins to a limited extent, the complex composition of the curing flora contributes to the formation of a typical, rounded aroma. If the breakdown processes get out of hand, there is a risk that a bad taste and smell will develop.
As a rule, the bacteria of the cured flora do not need to be added to the cured goods because they are omnipresent in meat processing plants. However, starter cultures can also be used for more reliable process management and avoidance of incorrect ripening . It is also possible to inoculate newly prepared cured goods with material from previous operations; For example, in the production of raw sausage - such as salami - fresh sausage mass can be mixed with 2-3 week old raw sausage in an amount of 1%. Catched brine can also be returned to the process.
Procedure
The meat, which is usually pre-dried, can be cured in different ways, there are traditional and regional variants.
Dry curing
With dry curing, the meat is rubbed or covered with curing salt and layered in layers. The tissue fluid is withdrawn by osmosis, which is how the “own fluid” is created. This process can take up to six weeks, depending on the size of the meat, but the high dehydration of up to 50% ensures the best shelf life. There is still a distinction to be made between “real” dry curing, in which the meat juice can drain off, and curing in its own brine, in which case the meat juice exceeds the pieces of meat after a few days, so that the process in the further course is comparable to wet curing .
Wet curing
For curing, the meat is placed in a brine . The water also diffuses through osmosis from the meat cells into the brine until the salt concentration in the meat corresponds to the concentration of the brine. At around four weeks, the process takes less time than dry curing, but it has a shorter shelf life because less cell fluid escapes. For the same reason, the meat stays juicier with this method.
Quick curing
Fast curing is a more labor-intensive variant of dry or wet curing to shorten the process time. In some cases, the methods can also be used in combination.
- dry
- Both the pieces of meat and the curing vessel are rubbed with curing salt and then the meat is layered tightly. After two days the meat is turned. The curing time is about five to seven days.
- Injecting
- The curing rake is injected directly into the meat, which shortens the process time to an average of three days.
- Rumble
- In this process, after the brine has been injected, the piece of meat is mechanically tumbled in order to distribute the liquid directly in the meat.
- vacuum
- By creating a vacuum, the escape of the tissue fluid is supported, the duration of the process is even reduced to two days per kilogram of the largest piece of meat.
Run away
Often the meat itself is not processed further after curing (smoked, air-dried), but instead a so-called burn - through phase takes place first . Here the salt supply is stopped (i.e. the meat is removed from the brine or salt), the diffusion now only takes place in the piece of meat, which means that the same salt content is established in the entire piece over time.
Curing salt
The use of normal table salt results in a reduction in the fluidity of the meat and thus a reduction in the number of bacteria. However, it does not work against the gray coloring of the meat and has a lower inhibiting factor against the bacterium Clostridium botulinum .
When curing, small amounts of nitrate or nitrite are added to the table salt. While this was 2–10% nitrates as admixture in the 19th century, their value has now (in Germany) reduced to 0.5–0.6% nitrite. In 1934 the use was regulated for the first time in the law on the use of nitric acid salts in food traffic, today this is the subject of various EU regulations and the German food book .
The guidelines of some organic seals prohibit the use of nitrate or nitrite; it is allowed with the European organic label.
Health concerns
Methemoglobin
As strong oxidizing agents, nitrites can oxidize hemoglobin to methemoglobin . The oxygen transport is impaired. This can be dangerous for small children; in adults, the enzyme methaemoglobin reductase converts the methaemoglobin back into hemoglobin.
Nitrosamine formation
The reaction of nitrites with amino acids can produce nitrosamines, which are considered carcinogenic . This is the reason that (speculative) concerns arose against the consumption of Hawaiian toast or salami pizza : At high temperatures, nitrites from the meat used could form nitrosamines with proteins such as those in cheese.
In the food technology department of the Technical University of Applied Sciences Berlin , analyzes of the corresponding dishes were then carried out and no higher nitrosamine levels were found than in dishes that are considered harmless.
The German Cancer Research Center assumes that the registered decline in gastric cancer is due to the reduced use of cured or smoked foods. In addition, epidemiological studies would suggest a positive correlation between the intake of nitrite from meat and sausage products and certain types of cancer.
The Federal Research Center for Nutrition and Food pointed out, however, that such foods are only responsible for around 3% of the daily nitrite intake and a significantly larger part comes from the intake of fertilized vegetables or from metabolic processes.
Reactive nitrogen compounds
A frequent diet with foods that contain nitrite or nitrite curing salt, such as ham or sausage, increases the risk of developing COPD ( chronic obstructive pulmonary disease ) according to a study . The cause seems to be the formation of reactive nitrogen compounds, which could lead to structural changes ( emphysema- like) in the lungs.
mania
A study of over 1,100 people found an increased risk of mania in people who consume more beef jerkey, a type of nitrate-treated meat. The risk was increased by about 3.5 times.
Legal regulation
Food ordinances, arranged according to product groups, regulate the use of nitrite and nitrate in Germany. Nitrite e.g. B. may only be added in combination with table salt as nitrite curing salt . In the additive approval regulation , for example, the maximum permissible amounts of residual nitrite and nitrate in the finished product are regulated.
In EU food law, curing salt is regulated as E249 ( potassium nitrite ), E250 ( sodium nitrite ), E251 ( sodium nitrate ), E252 ( potassium nitrate ) and must be labeled accordingly.
Distribution in Europe
According to the Association of Potash and Salt Industry, around 80 to 90 percent of all processed meat and sausage products in Europe are cured.
Curing in other cultures
The salting as a method of preservation is common in many cultures, increased just where hardly cooling devices are present. This means that untreated meat can be stored for longer. Another reason is that meat is carried along on the long walks of the cattle keepers. In Brazil - especially in the arid northeast - there are Charque , Carne do sol and Carne seca, which differ in the amount of salt used and the type of additional drying that takes place in the blazing sun at Carne do sol , and the draws water out of the meat to varying degrees. It is made exclusively from beef, the popular type of meat, and is also an ingredient in the Brazilian national dish Feijoada , for example . In the Trieste kitchen the calandraca is prepared with salted meat. A US-American variant of the preservation of beef, in which curing is used as a preservation method, is known as beef jerky . Other areas are also known worldwide for salt meat .
The actual curing - salting with the addition of nitrates or nitrites - has remained limited in the real sense to Europe.
Web links
- Text of the additives traffic regulation
- Information on the tension between curing salt and cancer risk
- Salted meat - definition, production and deception of the consumer, presentation by the Berlin-Brandenburg State Laboratory 2010 , accessed on April 20, 2014.
Individual evidence
- ^ A b c Oskar Prändl, Albert Fischer, Thomas Schmidhofer: meat. Technology and hygiene of extraction and processing . Ulmer, Stuttgart 1988, ISBN 3-8001-2135-2 , pp. 332 ff., 568 ff .
- ^ Bibliographical Institute (Mannheim). Dudenredaktion .: Duden, the dictionary of origin: Etymology of the German language . 5., rework. Edition Dudenverlag, Mannheim 2014, ISBN 978-3-411-04075-9 , p. 644 .
- ^ Friedrich Kluge : Etymological dictionary of the German language. 24th edition. Verlag De Gruyter, 2002, ISBN 3-11-017473-1 .
- ^ Curing. In: Digital dictionary of the German language .
- ↑ a b "Geselchtes" on traditional foods ( memento of the original from January 28, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , (PDF, 178 KB) accessed on January 24, 2015.
- ↑ G. Jüdell: About the methods of preserving meat. In: Polytechnisches Journal . 223, 1877, pp. 78-80.
- ↑ Sur . In: Jacob Grimm , Wilhelm Grimm (Hrsg.): German dictionary . tape 20 : Strom – Szische - (X, 4th section). S. Hirzel, Leipzig 1942, Sp. 1259 ( woerterbuchnetz.de ).
- ↑ Eduard Polenske: About the loss of nutritional value that the beef suffers from curing, as well as the changes in saltpeter-containing curing sheets. In: Work from the Imperial Health Office. 7th volume, Springer, Berlin 1891, pp. 471-474. See also: Eduard Polenske: Chemical analysis of various preservatives for meat and meat products found in the trade. In: Work from the Imperial Health Office. 5th volume, Springer, Berlin 1889, pp. 364-369.
- ↑ Josef Schormüller : The preservation of food . Ferdinand Enke, Stuttgart 1966, p. 711 ff .
- ↑ Additives - comparison of the Bioland guidelines and the EC organic regulation. (PDF) Bioland, accessed on September 2, 2017 .
- ↑ U. Pollmer, S. Warmuth: Lexicon of popular nutritional errors: misunderstandings, misinterpretations and half-truths from alcohol to sugar. 3. Edition. Piper, 2009, ISBN 978-3-492-25335-2 .
- ↑ P. Jakszyn, CA Gonzalez: Nitrosamine and related food intake and gastric and oesophageal cancer risk: a systematic review of the epidemiological evidence. In: World J Gastroenterol. 12 (27), Jul 21, 2006, pp. 4296-4303. PMID 16865769 .
- ↑ Information Service Science: "No connection between nitrite curing salt and cancer development"
- ↑ R. Varraso, R. Jiang et al: Prospective study of cured meats consumption and risk of chronic obstructive pulmonary disease in men. In: American journal of epidemiology. Volume 166, Number 12, December 2007, pp. 1438-1445, ISSN 1476-6256 . doi: 10.1093 / aje / kwm235 . PMID 17785711 . PMC 2573990 (free full text).
- ↑ Chris Aiken: Mania Linked to Beef Jerky: Hot Dogs and Bacon May Be Next. In: psychiatrictimes.com. October 8, 2018, accessed December 3, 2018 .
- ↑ Salt as a food: indispensable and valuable. 4th edition. Association of the Potash and Salt Industry V., Berlin 2009, p. 7, (PDF; 1.5 MB).
