I wouldn't recommend doing this, even if it is "clean"...
Why? Other than you would want to take care not to swallow the coin.
It's not the taste, it's the hardness. Gold is soft. Notice that people, in TV or real life, don't lick the gold with their tongue (where tasting is really done), they bite it with their teeth. They're testing the hardness.
When the Ferengi were biting the gold pressed latinum, I though perhaps that they were able to "sense" or taste the latinum inside the gold.
Making sure someone wasn't just handing them gold.