Sodium Hydroxide
What it does
Acidity regulator (e.g. pretzels, olives).
How it's made
Manufactured (caustic soda).
Sodium hydroxide, also called caustic soda or lye, is a strong alkali used in food processing to regulate acidity and for specific traditional jobs such as curing olives, giving pretzels their brown crust and glossy skin, and peeling fruit and vegetables. It is a processing aid as much as an additive, and is largely neutralised or washed away in use.
It is manufactured on a huge industrial scale by the electrolysis of salt water (brine). Passing an electric current through a concentrated sodium chloride solution splits it, producing sodium hydroxide together with chlorine gas and hydrogen gas as co-products. This chlor-alkali process is one of the oldest and largest electrochemical industries.
The sodium hydroxide solution is concentrated and purified, and can be supplied as a liquid or as solid flakes or pellets. The food-grade material is refined to a high purity, and because it is so strongly alkaline it is handled carefully and used in controlled amounts, typically to adjust pH rather than to remain in the finished food.
Possible reactions
Safe as used after processing; corrosive in concentrate.