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Ice crystal size changes during ripening in freeze concentration.
1Department of Food Engineering University of Massachusetts Amherst, MA.
Biotechnology Progress
|June 23, 2010
Summary
Ice crystal ripening, where smaller crystals melt and larger ones grow, is crucial for separating ice from sugar solutions. This process can be accelerated in food applications by controlling crystal sizes and removing certain components.
Area of Science:
- Physical Chemistry
- Food Science
- Crystallization Science
Background:
- Ice crystal size distribution impacts separation efficiency in freeze concentration.
- Surface energy effects drive melting of small ice crystals and growth of larger ones.
Purpose of the Study:
- To investigate the phenomenon of ice crystal ripening in sugar solutions.
- To understand the kinetics of crystal growth and melting.
- To determine factors influencing mass-transfer coefficients during ripening.
Main Methods:
- Photographic measurement of ice crystal sizes over time.
- Sequential analysis to determine neutral diameter (D(n)) and individual crystal diameters (D(i)).
- Controlled experiments with varying sugar concentrations and gelatin addition.
Main Results:
- Observed that crystals smaller than D(n) melt due to excess surface energy, while larger crystals grow.
- Melting and growth rates are proportional to (1/D(n) - 1/D(i)).
- Mass-transfer coefficients decreased with increasing sugar concentration and gelatin addition.
Conclusions:
- Ripening is a key process for producing large ice crystals for efficient separation from freeze-concentrated solutions.
- Ripening can be accelerated in food systems by optimizing initial crystal size and managing high molecular weight components.
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