TWRA does not define bait because it was "defined" by the legislature in TCA 70-4-113:
70-4-113. Use of bait, pitfalls and certain other devices in taking birds and animals prohibited -- Penalty -- Exceptions.
(a) It is unlawful for any person at any time to make use of any pitfall, deadfall, cage, snare, trap, net, baited hooks, poison, chemicals, explosives, set guns, spotlights, electric lights or torches, bait, which includes any grain, or mixture of any ingredients, used as or for food purposes, or other devices for the purpose of killing, injuring, or capturing any birds or animals protected by the wildlife laws of this state, except as otherwise expressly provided.
TWRA does have a law enforcement procedure in dealing with this statute that allows the use of mineral type items as long as they are at least 51% salt or other minerals and contain NO non-refined foodstuffs.
The majority of products you see marketed on the hunting shows are basically ground up grain or other natural products, with examples such as Acorn Rage, Sugar Beet Crush, etc., etc., etc. They would be considered bait in TN. There is no way to compile a list of legal or illegal products as those type items are constantly changing on the marketplace.