Each year we find it harder and harder to get different types of vinegar with different % of acetic acid in them, which also have the % listed on the bottle. All vinegar seems to be around the 4% - 5% mark.
This year, we've been asked to supply white, white balsamic and apple cider vinegars from the SAME BRAND to make it a fair test, plus the % of acid must be listed on the bottle!
Wow - perhaps if you can't get it with % on the bottle (I don't think I have ever looked for it!) you could contact the manufacturers and ask for MSDS which should have it written there somewhere. Then you could laminate the relevant page and store it with your vinegar. That's my only thought. Usually we just do 2 brands (one cheap, one expensive) and do a comparison. They usually come out pretty close. I have even just made my own and stuck it in an old bottle when we ran out and I forgot to buy more!
