Fractional freezing

Fractional freezing separates a mixture by partially freezing it, so crystals form with a different composition from the remaining liquid. The crystals and liquid can then be separated and processed further.

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Freezing-point depression: The lowering of a liquid’s freezing point when another substance is dissolved in it. As the liquid becomes concentrated in dissolved material, its freezing point shifts during partial freezing.
Freeze distillation: A concentration method that freezes part of a liquid and removes the resulting ice. It concentrates drinks by separating relatively pure ice from the remaining liquid.
Phase transition: A change between physical states of matter, such as liquid and solid. Fractional freezing uses the liquid-to-solid transition to partition mixture components.
Distillation: A separation method that vaporizes and condenses components according to differences in volatility. Distillation separates through vaporization, while fractional freezing separates through solidification.
Energy consumption in food processing: The energy used to transform, preserve, package, and store food products. Freezing and refrigeration can make freeze concentration energy-intensive despite avoiding evaporation.
Solid–liquid phase diagram: A graph showing which solid and liquid phases are stable at different temperatures and compositions. It predicts the compositions of crystals and residual liquid during freezing.
Applejack: An alcoholic drink traditionally concentrated by freezing cider and removing ice. It is a historical example of concentrating ethanol-containing liquid through partial freezing.
Eutectic system: A mixture whose components solidify together at a specific composition and lowest melting temperature. Eutectic behavior can limit how far a mixture separates by freezing.
Evaporation: The conversion of liquid into vapor at a surface below its boiling point. Evaporation removes solvent as vapor rather than as crystals of frozen solvent.
Volatile aroma compounds: Aromatic molecules that readily enter the gas phase and contribute to smell and flavor. Low-temperature concentration can retain these compounds that heat may drive off.