Dimethylpolysiloxane
What it does
Anti-foaming agent (frying oils).
How it's made
Synthesised silicone.
Dimethylpolysiloxane is a food-grade silicone oil used as an anti-foaming agent — it stops frying oils and other liquids from foaming and spattering, and prevents excessive froth during processing. A very small amount goes a long way, and it is well known as an additive in deep-frying oils used by fast-food chains.
It is a synthetic silicone polymer, built from silicon, oxygen and methyl (carbon-hydrogen) groups. Manufacturing starts from silicon metal, which is reacted to form methyl-chlorosilanes; these are then hydrolysed and polymerised into long silicone chains of controlled length, producing a clear, chemically inert oil.
The polymer is purified and its chain length adjusted to give the right thickness and performance for food use. Because silicones are extremely stable and unreactive, the food-grade oil is used in tiny quantities purely to control foam, and it is not broken down or absorbed to any significant degree.
Possible reactions
Generally safe at low levels.