"To taste the difference" means to compare two or more things, usually similar in nature, in order to detect any variations or distinguishable qualities between them. Full definition
Yes, this is the one I've been making for years, and I didn't taste any difference between the flours — there is so little in there, anyway. (theviewfromgreatisland.com)
What do you notice in taste difference between the pea and basil versions? (tinnedtomatoes.com)
Lots of honey varieties and you can really taste the difference in each one. (asaladforallseasons.com)