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Ice Morphology: Fundamentals and Technological Applications in Foods

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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. KeywordsIce-Crystal morphology-Freezing-Freeze drying-Freeze concentration-Microstructure
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... It has been suggested that large crystals with sharp edges can rupture cell walls and contribute to texture deterioration due to drip water loss [110], whereas rapid freezing generates small, fine intracellular crystals in the muscle, which are evenly distributed and do not cause significant losses [109]. Therefore, the speed of freezing is the parameter used to control the size and distribution of ice crystals in the system [111]. A further complication is recrystallisation, which occurs due to temperature fluctuations during freezing, causing the formation of larger crystals from the smaller crystals formed at the beginning [112]. ...
... A further complication is recrystallisation, which occurs due to temperature fluctuations during freezing, causing the formation of larger crystals from the smaller crystals formed at the beginning [112]. It is the process in which, over time, the average size of ice crystals increases, and their number decreases due to the redistribution of water from smaller ice crystals to larger ones [111]. One way to prevent recrystallisation is to keep the temperature constant throughout the storage process of frozen meat [3]. ...
... To obtain good freezing results, several strategies have been applied to increase the heat extraction rate, however, for this, the product should ideally be small and individually frozen. Freezing large products only results in the formation of large crystals that reduce the quality of the food [111]. New preservation technologies have been explored to improve the quality of meat reaching the consumer. ...
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... The presence of water in the product influences the protein denaturation (Vanzi et al., 1998), starch gelatinization (Slade & Levine, 1993), and also the state transitions in amorphous food components (Matveev et al., 2000). Freezing of water involves the formation of ice resulting from the crystallization of pure water present in the food product and is important in determining the process efficiency and quality of the food products (Petzold and Aguilera, 2009). The degree of ice formation in food products depends upon the freezing temperature. ...
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