It's interesting to compare the different ingredients lists for UK McDonalds and Canada/US McDonalds. The fries and the bun seem to have completely different ingredients, quite scary ones in Canada. Although they could just be called different things over here. They all say the burger is 100% beef and salt and pepper only.
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For example here are the ingredients of UK fries:
Potatoes, Vegetable Oil (Sunflower, Rapeseed), Dextrose (only added at beginning of season). Prepared in the restaurants using a non-hydrogenated vegetable oil. Salt is added after cooking
Here are the ingredients of Canadian fries:
Potatoes, canola oil, hydrogenated soybean oil, safflower oil, natural flavour (vegetable source), dextrose, sodium acid pyrophosphate (maintain colour), citric acid, dimethylpolysiloxane (antifoaming agent), (cooked in vegetable oil - Canola oil, corn oil, soybean oil, hydrogenated soybean oil with THBQ, citric acid and dimethylpolysiloxane), salt.