I have a friend who was a fairly well known tester, before becoming a commercial vendor himself. His background is being a trained master chef. As for reviewing juice, some he paid for himself, and obviously, some were provided for him, free of charge. His focus was not just simply whether he liked the flavor or not, but the accuracy of the flavors, as it related to the description of the juice, provided by the maker. He would evaluate the juice using various devices, such as dripping atomizers, tanks, RDAs, etc.