Steamrolling

In cartoons, the characters frequently get flattened by steamrollers. Clearly, steamrolling does not cause permanent damage, because the characters always pop back out of their flattened shapes.

Steamrolling is the only technique for flattening grapefruits that is reversible. Like cartoon characters, a steamrolled grapefruit has the ability to pop back out of its flattened disc shape. Steamrolling does no damage to the insides of a grapefruit.

Steamrolling can be a convenient technique for creating portable stacks of grapefruit. Just take a bag of grapefruit, steamroll each one into a flat disc, and stack up the flattened discs of grapefruit. You can take them on trips, unflattening them whenever you get hungry.

The only problem with bringing stacks of flattened grapefruit on trips is that you won't be satisfied. Because grapefruit tastes awful, you will become tired of your food supply within the first day or so of your journey.