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Ice Morphology: Fundamentals and Technological Applications in Foods
Abstract and Figures
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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... Thus, the results of both studies indicate that freezing combined with electrical disturbances decreased the smoothness of the surface 8 of 11 of ice crystals. The importance of ice crystal shape on product quality was reported by Petzold and Aguilera (2009), who found that round and smooth ice crystals are able to give a smooth body and texture to the frozen product [23]. The findings of this study highlight that microwave irradiation can produce finer ice crystals that can enhance the quality of the product. ...
... Thus, the results of both studies indicate that freezing combined with electrical disturbances decreased the smoothness of the surface 8 of 11 of ice crystals. The importance of ice crystal shape on product quality was reported by Petzold and Aguilera (2009), who found that round and smooth ice crystals are able to give a smooth body and texture to the frozen product [23]. The findings of this study highlight that microwave irradiation can produce finer ice crystals that can enhance the quality of the product. ...
... Thus, the results of both studies indicate that freezing combined with electrical disturbances decreased the smoothness of the surface of ice crystals. The importance of ice crystal shape on product quality was reported by Petzold and Aguilera (2009), who found that round and smooth ice crystals are able to give a smooth body and texture to the frozen product [23]. The findings of this study highlight that microwave irradiation can produce finer ice crystals that can enhance the quality of the product. ...
This study investigated the effects of microwave-assisted freezing on the quality attributes of button mushrooms (Agaricus bisporus). Four levels of microwave power (0, 10, 20, 30%) were applied to the mushroom samples during freezing. The quality attributes of the frozen and thawed mushrooms were then evaluated. The results suggested that higher microwave power produced the smaller and more uniform ice crystals. Moreover, the browning index of the mushroom samples increased with increasing microwave power. The textural properties (hardness) of the mushrooms were also affected by the microwave power, showing higher values as the power increased. Furthermore, the ratio of the microwave operating system’s power to the freezer power was low and approximately 20% at the highest power level. Therefore, these findings confirm the potential of microwave-assisted freezing for reducing freeze damage to mushroom tissue and, thus, provide frozen mushroom with a better texture.
... The pre-freezing temperature is a crucial parameter in the processing of freeze-dried Stropharia rugosoannulata products as it affects the sample's freezing rate. Studies have shown that the freezing rate significantly affects the formation of ice crystals, which in turn affects the drying rate and quality of freeze-dried products [25]. In our study, we specifically investigate the effects of different pre-freezing temperatures and times on the freeze-drying process and the resulting product quality of Stropharia rugosoannulata. ...
Stropharia rugosoannulata is a valuable medicinal and food fungus with high nutritive value. Freeze-drying addresses the storage and transportation challenges of fresh Stropharia rugosoannulata, expanding its market while preserving its flavor and quality more effectively than other drying methods. This study optimizes the vacuum freeze-drying process for Stropharia rugosoannulata using an orthogonal experiment method. The process parameters were optimized to determine their effects on the quality of the vacuum freeze-dried product, including pre-freezing temperature, pre-freezing time, and freeze-drying time. The optimal conditions were identified as a pre-freezing time of 60 h, a pre-freezing temperature of −80 °C, and a freeze-drying time of 72 h. The optimal product exhibited a bright color close to its natural state, with minimal browning and its natural white color maintained post-drying. During the drying process, the internal structure of the raw materials remained intact. After drying, the finished product retained its natural form, making it suitable for sale on the market. The soluble protein content of the vacuum freeze-dried Stropharia rugosoannulata reached 68 mg/g. Optimizing the freeze-drying process can better preserve the tissue structure and bioactive substances of Stropharia rugosoannulata, providing a reference for high-quality food processing and showing potential for sustainable development.
... Normally, sub-freezing is capable to reach a storage period that could not be achieved by all previous methods of incomplete freezing. Quality stabilization periods exceeding 70, 160 and 365 d were observed in the studies of Liang et al. [34] , Qian et al. [30] and Coombs et al. [35] , respectively. ...
... Recrystallization in frozen food is a critical phenomenon that affects the quality and texture of the food during storage. Generally, ice recrystallization in frozen food refers to the process where ice crystals grow and change in size, shape, and distribution over time during storage 1,2) . Larger ice crystals can create a gritty or coarse texture in frozen foods, affecting their palatability and mouthfeel. ...
Polysaccharides are widely used to preserve the texture of frozen desserts like ice cream by inhibiting ice recrystallization. Despite recent significant advances in research, a clear comprehension of the ice recrystallization inhibition mechanism of polysaccharides remains elusive. Some previous studies hypothesized that the ice recrystallization inhibition originates from the interaction between polysaccharides and ice crystal surface and tried to correlate it with the ice crystal shape. In this work, we have developed a novel method for analyzing the shape change of ice crystals during storage by curvature calculation. This method depicts the ice crystal shapes as the distribution of curvatures well expressing the changes of the ice crystal shapes. The newly developed method has been applied to evaluate the shape changes of ice crystals during the storage of sucrose solutions with and without kappa-carrageenan. The changes in curvature distributions revealed that ice crystals were rectangular with flat edges in the pure sucrose solution and were comparatively round in the sucrose/kappa-carrageenan solutions at longer storage time, which was not characterized in the roundness changes, showing the potentiality of using the curvature distribution to evaluate the shape change of ice crystals appropriately during storage.
... This slower heat transfer rate affects the temperature distribution during the freezing process, leading to a higher temperature gradient. Such a high gradient, in turn, results in smaller crystal sizes and more random orientations throughout the material, as different regions solidify at different rates [41]. ...
Freeze casting, a manufacturing technique widely applied in biomedical fields for fabricating biomaterial scaffolds, poses challenges for predicting directional solidification due to its highly nonlinear behavior and complex interplay of process parameters. Conventional numerical methods, such as computational fluid dynamics (CFD), require adequate and accurate boundary condition knowledge, limiting their utility in real-world transient solidification applications due to technical limitations. In this study, we address this challenge by developing a physics-informed neural networks (PINNs) model to predict directional solidification in freeze-casting processes. The PINNs model integrates physical constraints with neural network predictions, requiring significantly fewer predetermined boundary conditions compared to CFD. Through a comparison with CFD simulations, the PINNs model demonstrates comparable accuracy in predicting temperature distribution and solidification patterns. This promising model achieves such a performance with only 5000 data points in space and time, equivalent to 250,000 timesteps, showcasing its ability to predict solidification dynamics with high accuracy. The study’s major contributions lie in providing insights into solidification patterns during freeze-casting scaffold fabrication, facilitating the design of biomaterial scaffolds with finely tuned microstructures essential for various tissue engineering applications. Furthermore, the reduced computational demands of the PINNs model offer potential cost and time savings in scaffold fabrication, promising advancements in biomedical engineering research and development.
Antifreeze proteins (AFPs) have unique features to sustain life in sub-zero environments due to ice recrystallization inhibition (IRI) and thermal hysteresis (TH). AFPs are in demand as agents in cryopreservation, but some antifreeze proteins have low levels of activity. This research aims to improve the cryopreservation activity of an AFPIV. In this in silico study, the helical peptide afp1m from an Antarctic yeast AFP was modeled into a sculpin AFPIV, to replace each of its four α-helices in turn, using various computational tools. Additionally, a new linker between the first two helices of AFPIV was designed, based on a flounder AFPI, to boost the ice interaction activity of the mutants. Bioinformatics tools such as ExPASy Prot-Param, Pep-Wheel, SOPMA, GOR IV, Swiss-Model, Phyre2, MODFOLD, MolPropity, and ProQ were used to validate and analyze the structural and functional properties of the model proteins. Furthermore, to evaluate the AFP/ice interaction, molecular dynamics (MD) simulations were executed for 20, 100, and 500 ns at various temperatures using GROMACS software. The primary, secondary, and 3D modeling analysis showed the best model for a redesigned antifreeze protein (AFP1mb, with afp1m in place of the fourth AFPIV helix) with a QMEAN (Swiss-Model) Z score value of 0.36, a confidence of 99.5%, a coverage score of 22%, and a p value of 0.01. The results of the MD simulations illustrated that AFP1mb had more rigidity and better ice interactions as a potential cryoprotectant than the other models; it also displayed enhanced activity in limiting ice growth at different temperatures.
An installation is described for continuous crystallization of liquids by freezing. The installation performs liquid preliminary cooling under predetermined temperature; adding gas into cooled liquid and their intermixing; delivering mixed liquid and gas through the refrigerated evaporator; winding round mixed liquid and gas into the refrigerated evaporator; a pumpless refrigeration circuit, including compressor, water condenser, cooling tower, indirect refrigerated evaporator, expansion valve, low pressure receiver and required refrigeration accessories, for the realization of cooling volumetric crystallization of liquid flowing through the refrigerated evaporator. These processes cause the formation of a bubble slurry with crystal nuclei, gas bubbles and concentrated, unfrozen liquid; preparation means are described for transportation and further storage or use of bubble slurry...
Freezing is an excellent preservation method for foods [1,2]. The quality of frozen foods is closely related to the size and distribution of ice crystals. Existence of large ice crystals within the frozen food tissue could result in mechanical damage, drip loss, and thus reduction in product quality.
A new technique for characterizing the structure of firn and bubbly ice is presented. This technique, based on observation of etched (sublimation) surfaces in coaxial reflected light, enables une to see simultaneously the pore network of the firn or bubbles in the ice and the crystal boundaries. At the same time, the main stages of image processing used to transform the initial photographs into clean binary images are described.
The article contains Sections titled: 1.Introduction and Classification2.Quality Specifications and Analyses3.Mix Ingredients3.1.Fats3.2.Milk Solids-Not-Fat and other Protein Sources3.3.Sweeteners3.4.Stabilizers and Emulsifiers4.Manufacture of Mix5.Freezing Mix to Produce Ice Cream5.1.Dynamic Freezing5.2.Quiescent Freezing5.3.Flavoring Ingredients5.4.Impulse/Hand-held/“Novelty”/Fancy-molded Products6.Physical Structure and Properties7.Storage and Transportation8.Legal Aspects9.Economic Aspects Frozen desserts in the meaning assumed here are emulsions that are frozen while being whipped to incorporate air and are consumed while still frozen, usually as a scooped product or as a single-serving item. Mix ingredients typically include sources of fat, protein, sweeteners, stabilizers, and emulsifiers. Further classification depends on the presence of nonfat dairy ingredients as the protein source, to make frozen dairy desserts, and the presence and quantity of milk fat, to make ice cream. Frozen desserts are manufactured by the production of a mix, via blending of ingredients, pasteurization and homogenization, freezing that mix dynamically to incorporate air and produce small and discrete ice crystals, incorporation of discrete flavoring particulates (fruits, nuts, etc.) and either packaging and further freezing (hardening) the semifrozen ice cream product or shaping it into novelty or hand-held products (with or without stick insertion) followed by hardening. Quality is often defined by chemical and microbial composition, quantity of air incorporated, and size of the major structural elements (ice crystals and air bubbles). Maintenance of quality post-manufacturing depends heavily on temperatures of storage and distribution.
It is not possible to provide a complete coverage of all aspects of ice cream and frozen desserts in one chapter. However, various aspects are covered in numerous books (1,2), book chapters (3-8), and review papers (9-11).