Propylene Glycol
What it does
Humectant/carrier.
How it's made
Manufactured from propylene oxide.
Propylene glycol is a clear, slightly sweet liquid used as a carrier and solvent for flavours and colours, and as a humectant that helps keep foods such as cake icing and some confectionery moist. It mixes with both water and many oils, which makes it a versatile go-between in food formulations.
It is manufactured from propylene, a petrochemical building block. Propylene is first converted to propylene oxide, which is then reacted with water (hydration) to open its ring and form propylene glycol. The reaction produces mainly the desired product along with some larger related molecules that are separated off.
The crude glycol is purified by distillation to give a clear, nearly odourless liquid, and a specific high-purity grade is set aside for food and pharmaceutical use. It should not be confused with the toxic ethylene glycol used in antifreeze; food-grade propylene glycol is a different, well-tolerated substance used in small, regulated amounts.
Possible reactions
Generally safe at food levels; rare skin sensitivity.