Which military food packaging innovation, developed during WWII, revolutionized food preservation and later became ubiquitous in civilian product packaging?

Throughout military history, feeding troops has been as crucial as arming them. The evolution of military rations reflects advances in food preservation, packaging technology, and nutritional science. From ancient Roman legionaries carrying dried meat and biscuits to modern MREs (Meals, Ready-to-Eat) with flameless heaters, military product innovation has often led to civilian product developments. Test your knowledge about one of the most famous military product developments that revolutionized both combat feeding and civilian food packaging.

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K-rations in waxed cardboard boxes
SPAM in pull-tab cans
Retort pouches (flexible packaging that can be heat-sterilized)
Dehydrated food in laminated foil packaging