Traditionally, we've always used red wine vinegar. Most any grocery store sells whole black peppercorns. The reason why that's best is because it lasts a long time and maintains it's flavor. I'm sure you've been to Olive Garden where those guys walk around with the silly 3 foot pepper grinders. You don't need one that big, but if you get a normal sized one, your pepper will be freshly ground and taste great. Pepper that has already been ground can lose it's flavor. We never worried about mold and I've never seen it on pepper corns.