Supercooling Freezing Research Articles

Effectiveness of supercooled freezing in suppressing ice recrystallization during frozen storage

Ice recrystallization often occurs during frozen food storage, an undesirable occurrence that can cause further damage to food cells and tissues. One factor that triggers its occurrence is the initial structure of the ice crystals formed during the freezing phase. During frozen storage, small ice crystals may recrystallize due to their high surface-to-volume ratio and excess free energy. In this study, the ice recrystallization of supercooled frozen tofu was evaluated during a 12-week frozen storage period and compared with that of slowly and rapidly frozen tofu. The storage temperature was at − 10 ± 2 ℃. Slow freezing at − 10 ℃ static air has produced large crystals up to 0.6 mm before storage and tended not to grow further. Rapid freezing at − 80 ℃ static air with elongated ice crystals exhibits the highest recrystallization rate, especially on the surface of the sample, where the maximum ice crystals grew from 0.23 mm before storage to 0.45 mm after 12 weeks. Supercooled freezing has produced small and homogeneous ice crystals, the largest being 0.15 mm, but their spherical shape tends to have a low affinity for recrystallization, which has allowed the crystals to maintain their size and structure during the frozen storage.

Rocket drops: The self-propulsion of supercooled freezing drops

Supercooled water drops move spontaneously while freezing in vacuum. This self-propulsion phenomenon is caused by an enhanced evaporation rate from the frozen regions of the drops. The evaporating molecules carry momentum, and the drops acquire an opposite momentum, the same as in rocket propulsion.

Effect of supercooled freezing on the quality of pork tenderloin meat under different thawing conditions

This study investigated the influence of freezing after supercooling, which we also referred to as supercooled freezing, on the quality of pork tenderloin meat. Experiments for slow and rapid freezing with and without supercooling were carried out. Ice crystal formation was examined using X-ray computed tomography and optical microscope. Thawing of the frozen samples was subsequently conducted to contribute a holistic study on the quality of pork meat prior to further processing or consumption. The investigated thawing methods include the use of tap water, refrigerator, room air, and ice water. Quality measurements such as drip loss, texture, and impedance were employed after thawing. Results showed that the supercooled rapid and slow freezing conditions produced homogeneously distributed smaller ice crystals compared with the conventional non-supercooled freezing. The thawing method has a substantial influence on the drip loss and electric impedance at high frequencies. Supercooled rapid freezing combined with refrigerator thawing was found to be the best method that can improve the meat quality, owing to the morphology of ice crystals and better reabsorption of water during thawing.

Effect of different freezing and storage condition on the physical properties of protein coagulum (Firm Tofu)

This article attempted to apply supercooling freezing under atmospheric pressure to minimize the freezing damage on firm (momen) tofu, which is a representative of agglomeration type protein coagulum. Especially, we focused on the influence of different freezing rate after the releasing from supercooling state. Storage test up to one month with different storage temperature was also carried out. The quality parameters such as drip loss, texture, and microstructure were analyzed and compared with conventional methods (slow freezing and rapid freezing) after the storage under −80 °C and -20 °C up to one month. As the results, significant advantages were confirmed on the sample prepared by supercooling freezing even after the one-month storage. Further, higher freezing rate after the releasing from supercooling states successfully reduced the drip loss and kept good texture, with less microstructural damage. The possible mechanism on which supercooling freezing affects ice crystals formation and quality degradation are thoroughly discussed.

Effect of supercooling accompanying the freezing process on ice crystals and the quality of frozen strawberry tissue

Degradation of agricultural product quality occurs hugely during the freezing process, since ice crystal formation with volume expansion and increased osmotic pressure between cell membranes damages their microstructure. Recently, it is studied a freezing accompanied supercooled state for the entire food product, which induces finer and more homogenous ice crystals and improved the quality of soy bean gels after thawing. In this study, texture, drip loss, and microstructural changes were measured in frozen-thawed strawberries prepared by freezing with supercooling. In addition, ice crystals were observed directly using synchrotron X-ray computed tomography in supercooled frozen strawberries. The results showed, although supercooled freezing has the potential to form finer ice crystals in strawberry tissues, the quality of frozen strawberries was not improved compared with conventional slow freezing. It assumed that a higher and momently ice nucleation caused by supercooling was promoted a drastic water migration and huge degradation on strawberry cells by osmotic pressure in the frozen strawberries.

Effect of different freezing methods on drip, texture, microstructure in fresh cheese (paneer)

Paneer is acid heat milk coagulated soft cheese popular in South East Asia. The shelf life is a major limitation for its utilization; even when kept under refrigeration. Similarly, the texture becomes flaky and fluffy after thawing. Freezing rate effects on the growth of ice crystals as well as microstructure damage that is responsible for the change in the textural quality of the Paneer. In this study, the effect of two-dimensional freezing by static air observed before and after freezing. Effect of freezing on panner were subject to analyses under slow freezing at -30°C, rapid freezing at -80 °C and supercooling freezing conditions. The quality evaluation carried out by means of drip loss, textural analysis, and microscopic observation. By using this technique, it was possible to decide the supercooling freezing is significantly best method for preserve the paneer to keep required hardness, low drip and small cracks and rupture in a microstructure in compare to another method.

磁場下過冷却凍結保存法のための凍結槽一体型磁場印加用コイルの開発

In this paper, we developed a magnetic field generating coil for finding out an effective magnetic field for supercooled freezing of biological tissues under the magnetic field. The range of the frequency and the magnetic flux density of the inducing magnetic field was expanded by reducing the resistance compared with the previous coil. The upper range of the frequency increased from 2 kHz to 10 kHz and that of the magnetic flux density increased from 0.3 mT to 2.0 mT. We evaluated the magnetic field dependency of the degree of supercooling of the porcine ovarian tissues using the developed coil. In supercooled freezing, it is reported that the growth of the ice crystals, which is a cause of cell destruction, was suppressed with the increase of the degree of supercooling. This result indicates that increasing the degree of supercooling may enable to prevent cell destruction. Therefore we evaluated the effect of the magnetic field by measuring the degree of supercooling. As a result of the measurement, the averages of the degree of supercooling at 10 kHz frequency of 2.0 mT magnetic field increased the most from 9.1 ± 1.7 °C for without magnetic field to 10.5 ± 1.7 °C.

Ⅲ-1. 食品冷凍への過冷却利用とその効果

Ⅲ-1. 食品冷凍への過冷却利用とその効果

Phylogenetic analyses in cornus substantiate ancestry of xylem supercooling freezing behavior and reveal lineage of desiccation related proteins.

The response of woody plant tissues to freezing temperature has evolved into two distinct behaviors: an avoidance strategy, in which intracellular water supercools, and a freeze-tolerance strategy, where cells tolerate the loss of water to extracellular ice. Although both strategies involve extracellular ice formation, supercooling cells are thought to resist freeze-induced dehydration. Dehydrin proteins, which accumulate during cold acclimation in numerous herbaceous and woody plants, have been speculated to provide, among other things, protection from desiccative extracellular ice formation. Here we use Cornus as a model system to provide the first phylogenetic characterization of xylem freezing behavior and dehydrin-like proteins. Our data suggest that both freezing behavior and the accumulation of dehydrin-like proteins in Cornus are lineage related; supercooling and nonaccumulation of dehydrin-like proteins are ancestral within the genus. The nonsupercooling strategy evolved within the blue- or white-fruited subgroup where representative species exhibit high levels of freeze tolerance. Within the blue- or white-fruited lineage, a single origin of dehydrin-like proteins was documented and displayed a trend for size increase in molecular mass. Phylogenetic analyses revealed that an early divergent group of red-fruited supercooling dogwoods lack a similar protein. Dehydrin-like proteins were limited to neither nonsupercooling species nor to those that possess extreme freeze tolerance.

THE TEMPERATURE–TIME DEPENDENCE OF THE TRIPLE POINT OF WATER

The important, but elusive, temperature–time dependency of the triple point of water has been thoroughly investigated in 10 triple point cells from two sources. During the first 2 days after preparation of the cells, the temperature was found to increase by amounts ranging from 0 to 5 × 10−4 °C with the average rise being 2 × 10−4 °C. After the second day the temperature continued to rise at a rate of about 0.1 × 10−4 °C per day for about a week and finally stabilized. In practice, if an ice mantle in a cell is allowed to age for about three days before the cell is used the temperature should be reproducible to about 10−1 °C.A series of experiments are described which suggest that this initial temperature rise may well be due to the growth of crystals in the ice and/or strains in the freshly prepared ice. The slow rise after the second day could be accounted for by crystal growth. These two possibilities are discussed in detail and a formula relating the temperature to crystal size is compared with the observed results.Tests in pyrex cells up to 5 years old showed that they contain no significant amount of impurities and, therefore, that the segregation of impurities during the freezing process is not likely to be the cause of the initial temperature variations.On the assumption that the above explanations are true, a number of methods of eliminating this troublesome initial temperature rise were tested. Since none of these tests was completely successful, methods of extending the usefulness of old mantles were examined.Different methods of preparing and using the cells were critically examined; the earlier method of supercooled freezing was found to be quite inadequate. The effect of different thermal bonds in the thermometer well and of different cell environments was investigated. As a result of this work a new importance is attached to the standard practice of melting the inner layer of ice next to the thermometer well.The effect of the temperature–time dependency on previous measurements of the difference in temperature between the ice and triple points of water is discussed.