# Use of Phase Change Materials for Food Applications--State of the Art in 2022
###### Abstract  
The availability of food to a growing world population is a matter of concern for decades. Despite that, post-harvest losses are large in many countries, due to insufficient food preservation. And recently rising prices for fossil energies additionally increase food cost, thus increase the demand for energy efficiency. Probably the first application of phase change materials (PCM) ever was the use of ice for food storage, for preservation. Related to that is the use of ice for transport, and for fast cool down in food processing. The result of a desktop study shows the range of food applications of PCM, the advantages using PCM, and the state-of-the-art, meaning past and ongoing R&D, also including existing commercial products. The overview covers food processing, e.g., industrial process cooling and heating, local pre-cooling of harvested food, solar drying and cooking, for storage and transport e.g., solar cold rooms, fridges, display coolers, trucks and containers, and for food production specifically greenhouses and water purification. PCM are used in many real applications as commercial products, and in many other applications their advantages are proven. Regarding future R&D, the overview also identifies potential for improvement, possibly even of commercial products.  
energy storage; phase change material; food; processing; storage; transport; production; preservation; application +
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temperature, that a PCM needs to be cooled below the phase change temperature before the phase change starts (called subcooling or supercooling), or in general that phase change on heating and on cooling follows different temperature behavior (called hysteresis).  
The ability to store a significant amount of heat by changing phase in a small temperature range results in two main fields of use [1]: heat storage (also called thermal energy storage) with high storage density (per unit mass or volume) in a small temperature interval, and passive temperature stabilization (temperature control). Because of these advantages, PCM are used today in a wide range of applications [2]: in buildings for space heating and cooling as well as to prepare domestic hot water, in logistics, specifically the cold chain, for heating or cooling of the human body, even including medical applications, in mobility, in electronics, as well as industrial processes.  
Common PCM are for example water, paraffins, fatty acids, sugar alcohols, salt hydrates, and salts. PCM as bulk material are commercially available in a temperature range from about \(-50\)\({}^{\circ}\)C to about \(+90\)\({}^{\circ}\)C. For application, the PCM is often encapsulated, sometimes combined with another material to a composite material to modify one or several of its properties, or to add a completely new property.  
The most common PCM is water, if solid called ice. Ice has been used for cooling food and beverages already in ancient times, and this is still the most common application of water as PCM. It is directly added to food or beverages (if the water quality is good enough), e.g., as ice cubes, or encapsulated, e.g., in plastic containers, to prevent contact or even mixing with other things as well as preventing the water from flowing away such that it can be used over and over again. Encapsulated water, often just called ice packs, are e.g., used to cool picnic boxes. With a volume of up to thousands of m\({}^{3}\), ice storages are common, for cooling industrial processes, buildings, even parts of towns [3].