Yes but the reason is pretty stupid and complicated. It’s the same reason why they don’t get cold from flying through the clouds or burn up on impact when reentering from space. The episode where omniman teach Mark to fly. Remember how he talks about being able to freely move off of air and space. Viltrumites don’t fly by overcoming gravity, but by removing themselves from it entirely, they move the space around them, the same way Aquaman swims in water. In that space the force of this ability creates cavitation, like a forcefield, that cuts through the space around it. So that would, relatively, keep food being delivered roughly the same temperature(and possibly balance) as when it began cavitating.