Bacon is one of those ‘indulgent’ foods that has been widely consumed despite decades of finger-wagging by the nutrition police. It has the reputation of being high in fat (saturated), salt (sodium), cholesterol and carcinogens (byproducts of curing and smoking). None of these stand up well to scrutiny.
Bacon is an ancient form of food preservation. It made use of the parts of the pig that the wealthy didn’t want, usually the side (i.e. belly), and it was considered food for the peasants (as were oysters).
The pork belly was salt-cured, aged, smoked and stored in a cool room — the larder (a name that derives from lard — rendered pork fat). The more common term these days, pantry, comes from the French for bread (pain) and was a small cupboard (often under the stairs) rather than a walk-in room.
The original 3-step process took time, which also helped improve flavour. Let’s look at the steps, all of which have been compromised by modern industrial manufacturing.
Curing. Salting is the main preservation method. Copious salt rubbed over the surface of the pork diffuses into the meat where it draws moisture out of cells by osmosis. The salt unravels muscle proteins (denatures them) and begins to break them up into their flavoursome components — the amino acids. This is not dissimilar to what happens when cooking with heat or acids. The salt draws moisture out of most microbes and destroys them by desiccation. Some microbes are salt-tolerant but usually harmless and can improve flavour during the ageing process to follow.
Early salts were not highly refined and contained impurities. One common impurity was saltpetre (potassium nitrate — KNO₃). Around the 17th century it was noticed that when this was present the bacon retained a nice pink colour and didn’t develop a cooked taste during curing.
Much later (~1900), chemists found that it was not the potassium or the nitrate that did the job but nitrate’s relative — nitrite (NO₂). With time, salt-tolerant microbes break the nitrate into nitrite, and the nitrite helps bind the iron in the myoglobin molecule (oxygen-binding meat protein) so that it is not lost by oxidation. Oxidation is what causes untreated meats to go from red to brown as they are cooked. Nitrite also controls for botulinum toxin.
Eventually, a blend of sodium chloride (table salt) with small amounts of sodium nitrate and sodium nitrite was used, the nitrite working at first and being replenished in time by the breakdown of the nitrate (a form of slow-release). The curing mixture was tinted pink so that it would not be mistaken for table salt and be consumed directly. Pink salt.
Ageing. Once cured, the meat was hung for months to further dehydrate and preserve it. The ageing had a fortuitous secondary effect — salt-tolerant microbes started to further break down the proteins and add a greater depth of flavour.
Smoking. Another preservation and flavour-enhancing step. Volatile molecules (phenols) in smoke are small enough to penetrate the meat and infuse flavour. They are anti-microbial and anti-oxidant, and further contribute to food preservation.
Thus each of these 3 steps added flavour and increased preservation. In modern times you will need to seek out an artisan producer if you want to experience the flavour of bacon prepared this way. The process is too time consuming for industrial manufacture.
Curing. An unnecessary step given modern refrigeration. The pork is lightly salted (mainly for flavour) by injecting a salt brine into the meat via banks of small needles. This injection can increase the water-weight of the bacon and increase the cost to the consumer. Alternatively, the bacon can be pre-sliced and immersed in the brine. In any event, the process takes no more than an hour or so. Sodium nitrite can be incorporated into the brine to maintain colour. Sodium nitrate is not used (the ‘curing’ step is too brief for the nitrate to break down into useful nitrite).
Ageing. Skip. Replace with heat-processing.
Smoking. Maybe. But the bacon is more likely to be sliced and sprayed with a product called liquid smoke. It’s not as bad as it sounds though (see later). Other flavours might be added such as sugars or syrups (e.g. honey — salty goes well with sweet). These additives can be incorporated into the brining instead (or as well).
Bacon and health
At the beginning I listed five perceptions that might influence how guilty you feel about eating bacon. Lets have closer look.
Fat. Bacon fat consists mostly of unsaturated fat (about 2:1 unsaturated to saturated) and the unsaturated fat is mostly mono-unsaturated.
Breaking the fat down into its main fatty acid components, bacon fat doesn’t look all that dissimilar to olive oil. The main unsaturated fatty acid in both fats is oleic acid, and it is this acid that is purported to give olive oil its health benefits (something that hasn’t been established). The saturated fatty acid, palmitic acid, is a significant component of both bacon fat and olive oil, although present at higher levels in bacon fat. The main remaining notable saturated fatty acid is stearic acid, some of which gets converted by the body into oleic acid when eaten. What does all this mean? Who knows. Fats are diverse (olive oil contains around 2000 chemicals); health-related analysis is futile.
Salt. Modern bacon is much lower in salt than traditional bacon because salt is not needed for preserving. Be aware that if you have your eggs and bacon on toast, then there is nearly as much sodium in the toast as there is in the bacon (it’s also about the same as the egg). Bread is a major (possibly the main) source of dietary sodium in the modern diet.
Cholesterol. Newly not important. The 2015 report of the Advisory Panel to the U.S. Departments of Health and Human Services (HHS) and Agriculture (USDA) has recommended removing dietary cholesterol as “a nutrient of concern”. They made no recommendation on an upper limit to dietary cholesterol. Besides, bacon is relatively low in cholesterol.
Carcinogens. There are two potential sources, nitrosamines from the curing salt (if one is used), and smoke byproducts (if the bacon is conventionally smoked).
The curing nitrite (NO₂) forms nitric oxide (NO) that binds to iron in the muscle myoglobin and has two effects — it stops the meat from oxidising and developing rancid flavour, and it maintains an agreeable pink colour. It also retards the bacterium that causes botulism. The down side is that there is a very small risk that NO will bind to amino acids released by the breakup of proteins and produce nitrosamines. There is no established link between ingested nitrosamines and cancer in humans, but if delivered in massive doses in animal studies they are carcinogenic.
Nevertheless, for prudence, food regulations limit the amount of nitrite that can be added to bacon, and furthermore require that it be combined with anti-oxidants such as vitamin C (ascorbate) which are known to retard the formation of nitrosamines. Nitrosamines are present in some fermented foods such as some beers and cheeses, and in powdered milk (and other powdered products such as celery) and fish.
Wood smoke contains an incredible chemical mixture, but the main flavours come from water-soluble phenol volatiles. Phenols are also anti-oxidants that control rancidity (and so contribute to food preservation). These volatiles are a gas and invisible, the smoke you ‘see’ is made up of solids (soot) and oils (tars). It is these that might be carcinogenic, although they cannot penetrate into the meat and remain a surface treatment. They are easily separated out by dissolving smoke in water, and waiting for the solids and tars to separate out from the liquid phase that contains the dissolved phenols. This is what is bottled as liquid smoke — smoke flavour without the potential carcinogens. Unless otherwise stated, most modern bacon will probably use liquid smoke.