So, of course, I went and looked up the ingredients to the chewing gum.

Sweeteners (Sorbitol, mannitol, maltitol syrup (sugarfree), aspartame, acesulfame K),
gum base,
humectant glycerine (non-animal), flavourings,
sodium bicarbonate 0.24% (bi-white),
antioxidant E320,
emulsifier lecithin


I'm betting it the sugar alcohols (sorbitol & maltitol), plus the putrid sweet (aspartame) that are the culprits here. Just a guess, though.

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