When sourcing survival food, the caloric density is the most critical factor; standard emergency rations typically provide 2,400 to 3,600 kcal per pack. Ensure the macronutrient ratio is balanced, usually favoring high carbohydrates and fats for immediate energy, with a protein content that does not induce excessive thirst. Technically, the food must be non-thirst provoking to conserve the user's water supply. Look for vacuum-sealed, multi-layered foil packaging that provides a barrier against moisture, oxygen, and light, ensuring a shelf life of 5 to 25 years depending on the processing method (e.g., compressed biscuits vs. freeze-dried meals).