What Are Preservatives in Food? The Six Main Classes Explained

Preservatives are substances added to food to stop spoilage from bacteria, mold, yeast, or oxidation. They fall into two functional camps: antimicrobials, which keep microorganisms from growing, and antioxidants, which keep fats from going rancid and colors from fading. Salt, vinegar, sugar, and smoke did this job for millennia; the modern versions do it in milligram doses. The useful question is not whether preservatives are good or bad as a category, but which class is in your food and what the evidence says about that specific one.

Nitrites and nitrates (sodium nitrite E250, potassium nitrate E252) are the most consequential class. They cure bacon, ham, hot dogs, salami, and deli meats, blocking Clostridium botulinum and fixing the pink color. The trade-off is that nitrites can react with amines in meat to form nitrosamines, particularly under high-heat cooking, and nitrosamines are among the reasons the WHO's IARC classified processed meat as a Group 1 carcinogen in 2015. This is why manufacturers add ascorbate alongside nitrite to suppress the reaction, and why products labeled uncured still contain nitrate from celery powder, chemically the same ion from a different source.

Benzoates and sorbates are the workhorses of acidic foods. Sodium benzoate (E211) preserves soft drinks, pickles, and salad dressings; it is generally regarded as safe, with two caveats. Combined with vitamin C it can form traces of benzene, which forced soft drink reformulations after FDA testing in 2005 to 2007, and benzoates were among the additives in the 2007 Southampton study that linked certain additive mixes to hyperactivity in children, which is why some EU products carry warning labels. Potassium sorbate (E202) and sorbic acid (E200) inhibit mold in cheese, wine, baked goods, and dried meats, and have one of the cleanest safety records of any synthetic preservative.

Sulfites (sulfur dioxide E220 through sodium metabisulfite E223) keep dried apricots orange, wine stable, and dehydrated potatoes white. Their issue is not carcinogenicity but acute sensitivity: an estimated 3 to 10 percent of people with asthma react to them, which is why the FDA banned sulfites on fresh salad-bar produce in 1986 and requires declaration above 10 parts per million. Propionates (calcium propionate E282) are the mold inhibitors in packaged bread; they are produced naturally in Swiss cheese fermentation and in your own gut, though a small trial has linked high doses to irritability in children and metabolic effects, keeping them mildly contested.

The most contested class is the synthetic antioxidants: BHA (E320), BHT (E321), and TBHQ (E319). They protect oils, cereals, chips, and packaging liners from rancidity. BHA is listed by the IARC as possibly carcinogenic to humans based on rodent studies, and California's Proposition 65 lists it, while the FDA continues to allow both BHA and BHT as GRAS at capped levels. The EU permits them in fewer categories at lower limits. This regulatory split reflects genuinely mixed evidence, and it is why rosemary extract (E392) and tocopherols (E306 to E309, vitamin E) have been steadily replacing them in better formulations.

Context matters when you read a label: citric acid, ascorbic acid, and salt are also preservatives, and their presence says nothing negative about a product. A useful mental model is that one or two well-chosen preservatives in an otherwise short ingredient list is normal food engineering, while a stack of them alongside emulsifiers, colors, and flavorings, the pattern we map in common food additives, is the signature of an ultra-processed formulation. If you only track a handful, make it nitrites in meats you cook hot, BHA and TBHQ in fatty snacks, and sulfites if you have asthma; all three sit high on our list of ingredients to avoid. A scan sorts every one of these classes for you in seconds.