As for the “anti-foaming” agent E900 in my local cooking oil, that’s a new one to me. A quick Google reveals that, popular with McDonalds and...

Here in the US, there's been a decades long saga of McDonalds and fryer oils. Up until the late 80s, they'd been using beef tallow (saturated animal fat, probably mostly stearic acid, safe to keep at deep-fryer temps). Some vegetarians lobbied the company to change away from tallow. As, at the time, saturated oil had been vilified, they changed.

At the time, I was mostly eating vegetarian, but McD's fries were one of my guilty pleasures (not because of the sat fat but because I'd spent summers on a dairy farm, considered cows to be big puppy dogs, major hazard was getting licked, had issues with eating them). Anyway, when I learned that McD had changed away from tallow, I had to go try them. Blech! I stopped eating them.

I've read that since then, they've tried all sorts of formulas to get the original taste back. I'd expect those formulas are proprietary, so WTH knows what's in there(?) And once that mixture's been in a fryer for some hours...(?) They're not using sat fat, so most probably trans, but what else is going on?