Propyl Gallate
What it does
Antioxidant for fats/oils.
How it's made
Synthesised gallate ester.
Propyl gallate is a synthetic antioxidant used to stop fats, oils and fat-containing foods from becoming rancid, protecting flavour and colour. It is an ester made by joining gallic acid with propanol, and is often used together with other antioxidants, which can work better in combination than alone.
Its starting material, gallic acid, comes from natural tannins — plant substances found in sources such as gall nuts and tea — which are broken down (hydrolysed) to release gallic acid. This gallic acid is then reacted with propyl alcohol in an esterification reaction, joining the two to form propyl gallate and water.
The product is purified by crystallisation into a white to creamy powder. Although its gallic-acid backbone is plant-derived, the finished additive is a defined synthetic ester, used in small, regulated amounts and often paired with antioxidants like BHA or BHT for a stronger protective effect.
Possible reactions
Possible allergic reactions and stomach upset; caution in asthmatics.