Which innovative packaging feature was specifically introduced in the WWII K-Ration that revolutionized military food distribution and later influenced civilian food packaging?

During World War II, product packaging underwent a revolutionary transformation with the introduction of combat rations. These carefully designed food packages needed to be lightweight, durable, moisture-resistant, and provide adequate nutrition for soldiers in battlefield conditions. The development of these specialized product packages represents one of the most significant innovations in military logistics and has influenced civilian food packaging technologies we use today.

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Waterproof waxed cardboard boxes that could float and be used as emergency flotation devices
Individual meal units wrapped in moisture-resistant cellophane that extended shelf life to years without refrigeration
Self-heating metal containers that used chemical reactions to warm food without external heat sources
Color-coded packaging system that indicated caloric content for different combat intensity levels