freeze-drying

(verb)

Freeze-drying, also known as lyophilisation, lyophilization, or cryodesiccation, is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport.

Related Terms

Examples of freeze-drying in the following topics:

  • Desiccation

    • Pharmaceutical companies often use freeze-drying as a desiccation tool to increase the shelf life of products, such as vaccines and other injectables.
    • Another example from the pharmaceutical industry is the use of freeze-drying to produce tablets or wafers.
    • Water is usually removed by evaporation (air drying, sun drying, smoking, or wind drying) but, in the case of freeze-drying, food is first frozen and then the water is removed by sublimation.
    • Freeze-drying is performed using special equipment .
    • New freeze dryer which is equipped with systems for immediate feedback on the properties of the dried product, eliminating the lengthy trial-and-error approach.

  • Solid to Gas Phase Transition

    • Even ice has a measurable vapor pressure near its freezing point, as evidenced by the tendency of snow to evaporate in cold dry weather.
    • Such substances sublime; a common example is solid carbon dioxide (dry ice) at 1 atm of atmospheric pressure.
    • Solid carbon dioxide (known as "dry ice") sublimes into the air.

  • Freezing Point Depression

    • Freezing point depression is the phenomena that describes why adding a solute to a solvent results in the lowering of the freezing point of the solvent.
    • The freezing point depression can also be explained in terms of vapor pressure.
    • In this equation, $\Delta T_f$ is the freezing point depression, Kf is the freezing point depression constant, and i is the van 't Hoff factor.
    • The value of 0.93 oC is the change in the freezing point.
    • Discuss the effects of a solute on the freezing point of a solvent

  • Food Preservation

    • Drying is one of the most ancient food preservation techniques, which reduces water activity sufficiently to prevent bacterial growth.
    • Freezing is also one of the most commonly used processes for preserving a very wide range of food including prepared foodstuffs which would not have required freezing in their unprepared state.
    • Sugar is used to preserve fruits, either in syrup with fruit such as apples, pears, peaches, apricots, plums, or in crystallized form where the preserved material is cooked in sugar to the point of crystallisation and the resultant product is then stored dry.

  • Liquid to Solid Phase Transition

    • Freezing is a phase transition in which a liquid turns into a solid when its temperature is lowered to its freezing point.
    • Freezing, or solidification, is a phase transition in which a liquid turns into a solid when its temperature is lowered to or below its freezing point.
    • All known liquids, except helium, freeze when the temperature is low enough.
    • Most liquids freeze by crystallization, the formation of a crystalline solid from the uniform liquid.
    • But heat must be continually removed from the freezing liquid, or the freezing process will stop.

  • Specimen Collection

    • Lipemic, hemolyzed, or contaminated sera may cause erroneous results and should be avoided as should repeated freeze-thaw cycles.
    • Refrigerated CSF is acceptable for a limited number of serologic tests; however, if PCR is to be performed for the viral panels, the specimen must be frozen and shipped on dry ice.

  • Farenheit Scale

    • In the Fahrenheit scale, the freezing of water is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees.
    • On this scale, water's freezing point is defined to be 32 degrees, while water's boiling point is defined to be 212 degrees.
    • The Fahrenheit system puts the boiling and freezing points of water exactly 180 degrees apart.
    • Therefore, a degree on the Fahrenheit scale is 1/180 of the interval between the freezing point and the boiling point.
    • On the Celsius scale, the freezing and boiling points of water are 100 degrees apart.

  • Firmicutes

    • They can survive without nutrients and are resistant to ultraviolet radiation, desiccation, high temperature, extreme freezing and chemical disinfectants.
    • Up to 20% of the dry weight of the endospore consists of calcium dipicolinate within the core, which is thought to stabilize the DNA.

  • Marine Biomes

    • Therefore, living things that thrive in the intertidal zone are adapted to being dry for long periods of time.
    • Temperature decreases, remaining above freezing, as water depth increases.

  • Low Temperatures

    • Refrigeration (4ºC) and freezing (-20ºC or less) are commonly used in the food, pharmaceuticals and biotechnology industry.
    • For longer periods of preservation, freezing temperatures are preferred to refrigeration.
    • Freezing food slows down decomposition by turning residual moisture into ice, inhibiting the growth of most bacterial species.
    • Freezing temperatures curb the spoiling effect of microorganisms in food, but can also preserve some pathogens unharmed for long periods of time.
    • While it kills some microorganisms by physical trauma, others are sublethally injured by freezing, and may recover to become infectious.