Food Biophysics (2009) 4:378–396 DOI 10.1007/s11483-009-9136-5
REVIEW
Ice Morphology: Fundamentals and Technological Applications in Foods Guillermo Petzold & José M. Aguilera
Received: 15 December 2008 / Accepted: 9 October 2009 / Published online: 22 October 2009 # Springer Science + Business Media, LLC 2009
Abstract Freezing is the process of ice crystallization from supercooled water. Ice crystal morphology plays an important role in the textural and physical properties of frozen and frozen-thawed foods and in processes such as freeze drying, freeze concentration, and freeze texturization. Size and location of ice crystals are key in the quality of thawed tissue products. In ice cream, smaller ice crystals are preferred because large crystals results in an icy texture. In freeze drying, ice morphology influences the rate of sublimation and several morphological characteristics of the freeze-dried matrix as well as the biological activity of components (e.g., in pharmaceuticals). In freeze concentration, ice morphology influences the efficiency of separation of ice crystals from the concentrated solution. The cooling rate has been the most common variable controlling ice morphology in frozen and partly frozen systems. However, several new approaches show promise in controlling nucleation (consequently, ice morphology), among them are the use of ice nucleation agents, antifreeze proteins, ultrasound, and high pressure. This paper summarizes the fundamentals of freezing, methods of observation and measurement of ice morphology, and the role of ice morphology in technological applications. Keywords Ice . Crystal morphology . Freezing . Freeze drying . Freeze concentration . Microstructure
G. Petzold (*) : J. M. Aguilera Department of Chemical and Bioprocess Engineering, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Macul, Santiago, Chile e-mail:
[email protected]
Introduction Freezing is the process of ice crystallization from supercooled water. It is an efficient process of food preservation because in the frozen state, water is immobilized as ice and the rates of deterioration are much slower than at higher temperatures.1 Ice morphology (e.g., the size and shape of crystals) is important in the quality of frozen foods as well as in freeze-related processes such as freeze concentration and freeze drying.2,3 The morphology of ice crystals plays an important role in the sensorial properties of foods that are consumed in the frozen state. For example, the texture of ice cream is derived, in part, from a large number of small ice crystals (
