Pre-chopped white onions - vinegar added?

[gollyimholly]

Hello,

I bought some pre-chopped white onions from M&S and Asda. Under ingredients it just says "white onions". But now I've sauteed them they don't smell like what I'm used to sautéed white onions smelling like. Does anybody know if they might have vinegar added to them to preserve them? Even though it isn't included in the ingredients list?

Many thanks x

Onions can smell vinegary when they’re past their best/on the turn.

Oh dear :( I put SIX of them in