> I have asked some organic chemists about this, and they tell me
> that heating alone does not produce trans fats.  The process by
> which these trans bonds are made is: unsaturated fats are heated
> and hydrogen is bubbled through them under high pressure in the
> presence of nickel as a catalyst.  This doesn't happen in
> cooking.

frying does produce trans-fatty acids from cis-fatty acids.  This is why
cooking should be done with butter.

Andrew