To eliminate an issues with wood expansion, contraction and cracking, many fabricators recommend HDF, high density fiberboard.

i'm pleased with my white painted maple, as beverly says the center panels are mdf as a floating wood panel would shrink and contract and split the paint lines.

Our white cabinets are paint grade hard maple. The center panels are paint grade maple veneer with a MDF core. A solid MDF center panel is OK. Birch and Poplar also accept paint well but are softer than maple -- some of our Birch furniture was easily nicked so we went with maple. Avoid oak because of grain.