What is the difference between propionic acid and propionate?
Propanoic acid, propionic acid, propionate, sodium propionate - what do the different terms mean and what are the differences? Anyone who deals with short-chain fatty acids will inevitably ask themselves this question at some point. The descriptions often do not clearly distinguish between the terms. We will clear up the confusion of terms.
Propionic acid is produced naturally in the intestine
The short-chain fatty acid propionic acid is produced in the human large intestine by certain bacteria, known as clostridia. This happens naturally during the digestion of otherwise difficult-to-digest fiber. The terms propionic acid and propanoic acid are interchangeable. Propanoic acid is simply the scientifically correct term, while propionic acid is the trivial name for the short-chain fatty acid - even if the term does not really sound trivial. Propionic acid has also been approved for many years as a food additive for various purposes, such as preserving bread.
Propionates are the salts of propionic acid
Propionic acid in its pure form has clear disadvantages: concentrated propionic acid is caustic, tastes sour even when diluted, and has a very unpleasant smell. Ingesting a diluted solution would be perfectly safe, but the bad smell makes it quite unappetizing. However, the highly reactive propionic acid easily forms salts with equally reactive substances such as sodium, potassium, or calcium. The salts of propionic acid are called propionates. In food, manufacturers usually combine propionic acid with sodium, the chemical element that is also the basic ingredient for normal table salt (in this case: sodium chloride). In contrast to liquid, highly volatile propionic acid, its salts are white, crystalline, and odorless substances.
How does propionic acid become propionate?
One of the properties of short-chain fatty acids is that they are particularly reactive. Chemically speaking, they have a hydrogen atom that can easily be released and replaced by other substances. In the case of salts, this means: the superfluous hydrogen atom is gone, sodium is added - and the result is sodium propionate. Industrially, this is done using sodium hydroxide, also known as caustic soda. If you paid attention in chemistry, you'll remember that acid and alkali become salt and water. In the case of propionic acid, this looks like this:
This is how propionic acid becomes sodium propionate.
Is sodium propionate safe to use?
The European Food Safety Authority (EFSA) classifies propionic acid as harmless. It is approved as a food additive with the E numbers 280 for propionic acid and 281-283 for its salts. Propionic acid and its salts are used in the food industry, for example, because they have a fungicidal effect, i.e. they kill fungi and spores or prevent their growth. In this form of application, they prevent the formation of mold, which is why they are used to preserve sliced bread and baked goods. Propionic acid is also added to silage, the fermented feed of cows. While propionates are used for baked goods, propionic acid is used for silage, because a little more or less smell doesn't matter there. Since our noses and tongues are a little more sensitive and picky than cows' noses and tongues, sodium propionate is the logical choice for manufacturers.
