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HOW IT WORKS

WHAT IS FREEZE DRYING

Freeze drying (lyophilization) is the most perfect method of preservation known. The steps involved require the product to first be frozen and placed in a chamber where the pressure can be reduced. The ice crystals in the product will then be removed through sublimation. Sublimation involves the ice being transformed from a solid to a gas without going through the liquid phase. This method of water removal takes place while the product is frozen in a solid matrix. 

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Drying at these low temperatures creates an end product that retains its original nutritional value, including vitamins and minerals, making it a perfect preservation method for food. 

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STAGES INVOLVED IN FREEZE DRYING

FREEZING:

Freezing the product can be accomplished in advance of loading into a freeze dryer, by using commercial freezers, including walk-in freezers. Also, many types of freeze dryers have a refrigeration system on the product chambers, allowing for the product to be frozen in the product chamber.

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Products need to be frozen solidly before starting the freeze drying process. This will help retain the overall shape of the product, eliminating shrinkage and shriveling. Freezing the product quickly results in smaller ice crystals and a higher quality end product. 

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FREEZING 

02

PRIMARY DRYING

03

SECONDARY DRYING

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PRIMARY DRYING:

Primary drying is the secondary stage of the freeze drying process. During this stage, the pressure in the product chamber is reduced using a vacuum system, and heat is applied to the product. The addition of heat energy encourages sublimation to occur. As water vapor comes out of the product, it migrates to either an internal condensation chamber or remote condenser. These cold surfaces remove the heat energy (heat of sublimation) from water vapor, causing it to solidify on the condenser surface as ice. The condenser traps migrating water vapor, protecting the vacuum pump.

SECONDARY DRYING:

The final stage of freeze drying (adsorption). Once the primary moisture is removed, the remaining moisture is chemically bound. This moisture is removed by increasing the temperature of the product, breaking the bonds between the moisture and the product. Normally this additional heat is added slowly, using a known recipe that does not harm the product.

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