I think the roast beef or something is labeled as 'gyro meat' aboard the carriers-experience.
What it is actually made of I have no idea.
The carrier often operates on a 'pay check to pay check' diet. The machine is packed with food stores, ammo, repair parts, etc and then it sallies forth.
The food is cooked, eaten, spoiled, otherwise consumed and must be replenished. Replenishing the machine is a huge phenomenon. Sometimes.the replenishing does not happen soon enough or there is rationing because they know the ritual of replenishment can only happen on x date which is a long way out.
With news articles like the one hyperlinked by someone, im sure the priests of the machine are going to ensure to gather a bountiful replenishment and spoil the men and women of the machine as soon as is actually possible--hopefully.