The process of curing meat (including fish, shellfish, and poultry) is an ancient process, the origins of it lost in antiquity. The origin of our verb to cure comes from the Latin verb curare, meaning "to take care of". The word passed into Middle French as curer, and after the Norman conquest in 1066 into what became Middle English as curen. Thus is shares its roots and ultimate meaning as the medical use, "to take care of".
Real curing requires salt, but for several reasons salt alone is not the ideal curing agent. In a truly cured meat (I shall continue to use that term to include the items in the first sentence), the salt content is high and the moisture level is low. Remember, the primary purpose of curing is to prevent bacterial and fungal attack on the meat, but there are other factors at play as well.
First a bit of history. Back in the days when there was no refrigeration, no canning, and little knowledge about chemistry and biology, it was extremely difficult to preserve meat except in cold weather for future consumption. It can be argued whether meat is essential for humans (actually, it really can not because people on well planned vegan diets do fine), but there is no argument that meat has and continues to be a central part of the diets of many cultures around the globe, from many time periods. Meat has many benefits, especially in societies that have or had few other sources of high quality protein. In addition, many meats are high in fat, which is the most concentrated source of energy. These days this can be a disadvantage, since obesity rates are high in the developed world, but back when malnutrition was the rule rather than the exception, fat was a critical factor in maintaining body mass.
Most of us have eaten actually very little truly cured meat. Most of the things that we think of as "cured" and actually just heavily brined. Over the millenia that we humans have consumed cured meats, we have developed a taste for cured items. Now that refrigeration is common, there is not such a need for curing, but we still like the flavor, and that is provided by treating meat with much smaller amounts of curing materials, and also leaving way to much water in them to preserve them. Here is a very simple and just about foolproof way to tell the difference: if a "cured" meat requires refrigeration, it is not really cured, but rather brined for flavor.
Truly cured bacon and ham can be stored at room temperature for months if not years without going off, but imagine putting a standard pound of bacon or a ham in your cupboard for even a week and trying to eat it! Cured meat will keep in porous cloth bags (used to keep it clean), but a "store" ham would be reeking in a cloth bag after a week, and would surely cause food poisoning.
It is likely that the first cured meat was jerky, and it was unlike the modern product. Originally, jerky was simply strips of meat with as much fat removed as possible that were sun dried, with or without salt. The meat became so dehydrated that no microbes could live in or on it, down to under 10% moisture content. The ancient peoples of the Andes had an even better system, very much like modern freeze drying. This is called charqui and is made by allowing the thin slices of meat to freeze at night, and under the low atmospheric pressure at those altitudes, some of the ice would pass directly to the vapor phase (technically called sublimation) , and then during the day the ice would melt, and liquid water would evaporate. This only works at very high altitudes, but produces a product quite different than jerky in that it is very porous and absorbs water quickly during cooking, where jerky is much slower to rehydrate. Both of these are truly cured in the sense that no refrigeration is require for storage. But neither of them are ham or bacon!
Fresh meat is around 75% water, give or take, with around 20% protein and 3% fat. We are talking only the muscle parts here, not the fat that often surrounds the piece of meat. Some meat has more fat and less protein and water than others have, but this a pretty good general rule of thumb. Fresh meat contains very little salt. The salt concentration in most living organisms is only about 1%, and that is mainly in the cellular or blood fluids. Muscle and fat contain far less.
A ham that is traditionally cured will be more like this: around 60% moisture and 6% salt, the remainder being protein and fat. Unlike jerky and charqui, these items contain much more moisture. The key is the salt, which is bacteriostatic and bactericidal. It also is somewhat less effective in killing or inhibiting molds, but doe have some effect on them. Traditionally cured ham, bacon, and corned beef will keep for months at ambient temperatures. By the way, the use of the word "corned" in corned beef has nothing to do with corn. In England, barley was one of the most important grains in the old days, and a grain of barley was called a "corn". The coarse salt at the time was about the size of a grain of barley, and the term was transferred.
Salt works by pulling out moisture from the meat, and also from any little microbial buggers that are on it. That is why it so important for preservation. However, meat cured purely by salt tends to have an unappetizing brown color and a couple of other defects. Enter nitrites. Originally added as nitrates (note the difference in spelling), it turns out that nitrites are essential for an effective cure for several reasons. Potassium nitrate, also known as saltpeter, was added to the curing process around 1550 (no one knows the date of the first use). There was an immediate improvement in the color of the product, and also its keeping abilities (more on this later when we discuss cured sausages). It turns out that some beneficial bacteria and convert nitrate to nitrite, and it is the nitrite that does the jobs. Since this is Pique the Geek, here are the chemical formulae for both nitrate and nitrite ions.
Almost all modern brines and cures use potassium or sodium nitrite now rather than the nitrate, except for the very long cured ones that benefit from the slow bacterial conversion. As I said, meat cured without nitrite has a dullish, brown color where meat cured with nitrite is pink. The reason is that our old friend from a couple of weeks ago, nitric oxide (NO) is released as the nitrite reacts with the meat. The NO binds very tightly to the iron in myoglobin, one of the important constituents of meat. It turns out that this nitrosomyoglobin is pink and heat stable. The pink layer near the surface of meat cooked over charcoal or wood is also due to this, because the precursor of NO, nitrogen dioxide (NO2) is released from the fuel during burning, and it the surface of the meat can color it pink.
The NO bound to the iron also has an effect on fat. It turns out that iron in salt only cured meat catalyzes the breakdown of fat into sometimes ill smelling materials (technically called rancidification) and the NO effectively "caps" the iron, reducing that catalytic ability, so the fat is more stable. This is important for long term storage. Finally, nitrite is also a potent inhibitor for the deadly bacterium Clostridium botulinum, the cause of botulism, the most deadly form of food poisoning. This is not as important for things like ham and bacon, because the bacteria are on the surface of the meat, and the surface is exposed to oxygen. Since C. botulinum is a strict anerobe (can not grow in the presence of oxygen), that is of little cause for concern. (Remember, traditional bacon is not sliced until cooking time).
This is a huge problem in sausage. Most people think of botulism as a product of poorly canned foods, but it was known long before canning came to be, and it was known from sausages. As a matter of fact, the Latin for sausage is botulus! Since sausage is made by grinding meat, the surface of the original meat is now distributed throughout the meat, and the interior gets no oxygen exposure. Using nitrite is an effective method of eliminating this threat. I would caution anyone not to eat home cured traditional sausage if nitrite is not used. Most curing products do indeed contain nitrite. My favorite is Morton Tender Quick, and this product that contains both sodium nitrate and sodium nitrite in addition to the salt. The company website emphasizes to use it according to directions and not to exceed the recommended amount. I second that, because there is no benefit in excess nitrite and in high doses it does to your blood what it does to myoglobin: it nitrosoates the hemoglobin in your blood! Current FDA requirements allow no more than 200 parts per million of residual combined nitrate and nitrite in cured foods.
A reader on What's for Dinner? last week when I hosted and first floated the idea about this topic mentioned prosciutto di Parma ham. This is a sea salt only cured ham, without added nitrate or nitrite. It gets it color another way. Current research indicates that the extremely long cure time for this product (up to a year) allows the development of a couple of species of Staphylococcus bacteria (not the human infection causing species), tolerant of high salt concentrations, actually contribute the pink color. This makes sense, because many Staphylococci express highly colored metabolites. Anyone who has had a Staphylococcus aureus sinus infection will attest the the bright golden color of the discharge (hence the genus name aureus, Latin for "golden").
These hams do not need to be cooked, and most connoisseurs prefer them raw, thinly sliced and eaten as is. The long curing kills any Trichinella spiralis, the causative organism for trichinosis. Once again, since these are solid pieces of meat, nitrite is not necessary for prevention of botulism.
The procedure for making traditional cured whole meat (it is bit different for sausage) is to cover the, say, ham, is to pour a layer of curing mixture in a nonreactive vessel (glass is good, but plastic is OK too) and the put the ham in the vessel. Then add curing mixture until the ham is completely covered. It is best to do this in a cool place, but the refrigerator is so cold that it slows down the process. Sugar can be added to the mixture if desired, and it takes some of the edge off of the salt flavor. The ham is allowed to cure for several days, and then removed and repacked with curing agent (the old curing agent is fine to reuse if you discard any water saturated portion). This process is repeated every several days until the agent has penetrated to the bone. Depending on the conditions, 12 to 14 days are required, or longer for very long cured meats.
Too make sausages, the general procedure is to take the chopped meat and (usually) added fat, the curing agent, whatever spices are appropriate for the kind of sausage being made, and usually some sugar to act as bacteria food. Modern practice is to add the desired bacterial culture, but in the old days whatever was in the environment were what were used. This mixture is then pressed into casings, usually the carefully cleaned intestines of whatever the meat animal was, and tied. In addition to curing, there is also a fermentation because of the bacteria. The fermentation takes the better part of a day to several days, depending on the bacteria and the temperature. After drying for several weeks, the sausage is ready.
Many traditional whole meat and sausage cured products are smoked after curing, but not all. Smoking does make them keep a little better by coating the surface with mold inhibiting chemicals. They can be hot smoked, which cooks them at the same time, or cold smoked at a low enough temperature that they are not cooked. For effective preservation, they have to be smoked for quite a while. Once smoked (or not), the final products are traditionally placed in cloth bags to prevent insect or vermin attack, but often were just left hanging in the smokehouse on string or wire so that mice and rats can not get to them. Even bagged meat is not protected from those gnawing pests.
7:50 PM Sunday. I just got back from talking with my neighbors, Elmer and Helen. They grew up curing their own pork, and here is how they did it. For a ham, Elmer says that it is critical to penetrate the joint betwixt the shank and butt portions and drain the synovial fluid or the ham will ruin. Then the hole that you made to drain the fluid gets filled with salt. His family used only rock salt, no nitrate, to cure hams and bacon. They would place the item on a wooden table sloped so that the fluid would drain. Then they would coat the meat to about half an inch with salt. Every couple of days they would check and add more salt if any had dissolved away or fallen off of the meat. Generally they would start around 15 November, depending on the weather (warm is bad) and kept applying salt as above until around 15 December. Then they would rub off the salt, bag the ham, and hang it. They did not smoke them.
After the initial cure, they let the ham hang until June, then it was ready. Elmer said that two years of hanging actually made a better ham, as its flavor developed more fully, so they rotated their hams by year of curing. I specifically asked him what color the meat was when it was cooked, and he confirmed my statement before that meat cured without nitrate or nitrite is dull. These hams are too salty to eat except as a snack without leaching out some of the salt. They did that either with cold water, or just below the simmer, depending on how soon they wanted to eat the ham. He further said that they cured essentially the entire animal except for the organ meat (which do not cure well and are eaten fresh) and the loin, eaten fresh because of the nature of the meat.
Neither Elmer or Helen made cured sausage growing up, and since they did not use nitrite that is probably a good thing. They would make fresh sausage and fry all of it at once in balls, then put the cooked balls in storage jars and cover them with the fat from the frying to keep out air and microbes. To use it, they just had to thaw the fat and reheat the already cooked fresh sausage.
It should be noted that a fully cured can be made with an extremely strong salt brine, but unless knows a benefit over the dry curing method I shall leave it alone here. Now to how modern things that pass for "cured ham" and "cured bacon" are made. First, a weak brine of salt, nitrite or nitrate or both, sugar, and sometimes other agents, such as smoke flavoring, is injected in many places into the ham or bacon slab. For ham, the injected hams are then placed in a tumbler to bruise the meat and distribute the brine evenly. Then they are sealed in plastic and refrigerated or frozen. This brining has almost no preservative effect, and acutally increases the water content of the meat from around 75% to 80% or more, so in that sense these hams are even LESS preserved than fresh ones!
Bacon is made in much the same way, except they use hundreds of small needles (whole bacon is flat, so it is easier to handle and thus no tumbling is needed) and it is usually skinned and sliced before packaging. It is just as perishable as a modern ham, the brine being for taste only.
These concepts apply to beef as well, although in the past only the worst cuts of beef were traditionally cured, such as brisket for corned beef and some other poor cuts, the majority of it being eaten fresh. Actually, until recently beef was not widely eaten because cattle had more value as dairy animals. Most red meet in the past came from sheep, lamb, and goat because they were not as valuable as cattle and due to their smaller size could be eaten fresh before the flesh spoilt.
Well, that pretty much does it for curing. Usually I have a joke in this spot, but will have a special comment a little later. I always learn much more than I could possibly hope to teach in writing this series, so please keep those comments, questions, corrections, and other feedback coming. The comment section is the best part of this series. I shall hang around as long as comments warrant this evening, and shall return tomorrow at about the same time for Review Time.
Now for the special comment: Fox "News" Channel continues to run a Sunday morning spot with the inept Dr. Isadore Rosenfeld. I have corrected him before about carbonated beverages, and shall correct him again about deodorants and antiperspirants. Actually, I wrote a piece on this very topic a long time ago, but in brief, deodorants prevent odor by inhibiting the population of bacteria, the actual culprits, from converting sweat components into odorous substances. This can be done with agents that kill bacteria, such as triclosan, or by agents that chelate essential elements for bacterial growth, making them unavailable for the bacteria. Antiperspirants work by plugging up the pores in the armpits, making sweat stop flowing. Most of them are based on aluminum chloride or some zirconium compounds. No sweat, no odor regardless of the presence of bacteria.
Dr. Rosenfeld incorrectly stated that all odor prevention products contain both kinds of agents. This is just fundamentally incorrect, and I have a newly purchased stick of deodorant that has no pore plugging agent at all. Dr. Isadore Rosenfeld is an embarrassment to himself and to the scientific and medical community as a whole and should retire from the program. I would have said that he is an embarrassment to Fox "News" Channel, but they are immune to being embarrassed. I understand that he still practices medicine and also is a professor of medicine who is still active. I surely would not want him as my physician.
Next Wednesday My Little Town will recall the days when outlaws essentially ran the town, and Friday Popular Culture resumes the comprehensive series on The Who, with the first half of Tommy on deck.