Self-heating food packaging (SHFP) is active packaging with the ability to heat food contents without external heat sources or power. Packets typically use an exothermic chemical reaction. Other types of active packaging are self-cooling food packaging and radio-frequency identification (RFID). Packages like these are typically used by the military during operations when it is unsafe to have a fire to cook. Bananas, meat pastes, and many other foods are examples of foods that can be stored this way.
Commercial heat sources for self-heating food packaging use an exothermic reaction (heat being lost to the surroundings) between quicklime, or calcium oxide, and water, which generates 58 calories of heat per gram. Quicklime, inexpensive and readily available, is generally recognized by the FDA as safe. The by-product of the reaction is calcium hydroxide.
For the military's Meals Ready to Eat or the flameless ration heater, the military uses calcium chloride heater. Water activates the heater, which generates heat of 310 calories per gram. Hydrogen is released as a byproduct. Civilian versions are available; it is rarely possible to buy packets individually from legitimate sellers.
Current research focuses on cost reduction using reactions without odor or fumes. One heat source in development uses air-activation reactions that utilize oxidation of common metals like iron or zinc. Another uses solid fuel energy storage technology. The heating element contains aluminum and silica, two benign materials, which in an intimately mixed powdered state can undergo a chemical reaction to give off a large amount of heat. The small heater unit is formulated to give high utilization of the chemical energy content and generates 720 calories of heat per gram.  To view a demonstration of the aluminum/silica self-heating "Self-Heating Coffee Demonstration" on YouTube Neither technology is commercially available.
Books, General References
- Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6
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