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Freeze-drying process
1) The fruits or vegetables are frozen at very low temperatures (–50 tot –80 degrees Celsius).
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2) The drying process is done in two steps. The first step is quite slow and takes a couple of days. Under reduced air pressure most of the ice crystals are removed by sublimation, this means that the ice turns directly into water vapor. This takes place at temperatures that are typically several tens of degrees below freezing. The low temperature does make the sublimation take longer, but is also ensures optimal preservations of taste and texture. Finally, there is a phase of post-drying at higher temperatures to remove the last remaining water.
Spray-drying process
Spray drying is a method of producing a dry powder from a liquid by rapidly drying with a hot gas.
A spray dryer takes a liquid stream and separates the solute or suspension as a solid and the solvent into a vapor. The solid is usually collected in a drum or cyclone. The liquid input stream is sprayed through a nozzle into a hot vapor stream and vaporized. Solids form as moisture quickly leaves the droplets. A nozzle is usually used to make the droplets as small as possible, maximizing heat transfer and the rate of water vaporization.
Examples of this production method are milk powder, cocoa powder and instant coffee powder.
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In addition to the range of freeze-dried products Frubero recently also offers a small range of spray-dried fruit powders.
