דו״ח מאומת

Cells can endure storage at low temperatures such as--196 degrees C for centuries. The challenge is to determine how they can survive both the cooling to such temperatures and the subsequent return to physiological conditions. A major factor is whether they freeze intracellularly. They do so if cooling is too rapid, because with rapid cooling insufficient cell water is removed osmotically to eliminate supercooling. Equations have been developed that describe the kinetics of this water loss and permit one to predict the likelihood of intracellular freezing as a function of cooling rate. Such predictions agree well with observations. Although the avoidance of intracellular freezing is usually necessary for survival, it is not sufficient. Slow freezing itself can be injurious. As ice forms outside the cell, the residual unfrozen medium forms channels of decreasing size and increasing solute concentration. The cells lie in the channels and shrink in osmotic response to the rising solute concentration. Prior theories have ascribed slow freezing injury to the concentration of solutes or the cell shrinkage. Recent experiments, however, indicate that the damage is due more to the decrease in the size of the unfrozen channels. This new view of the mechanism of slow freezing injury ought to facilitate the development of procedures for the preservation of complex assemblages of cells of biological, medical, and agricultural significance.…

PMID: 6383068

Organelles, cells, tissues, or any other biological construction can be preserved using a method called cryopreservation, in which samples are cooled to extremely low temperatures. The reaction of the living cell to the formation of ice is both theoretically intriguing and practically useful. Since osmotic shock, membrane damage, and ice crystal formation during freezing and thawing will result in cell death, other viable tissues and stem cells, which are of much importance for uses in basic research and medical applications, may not be preserved by simple cooling or freezing for large periods. With the aid of cryoprotective agents (CPAs) and temperature control technology, the successful cryopreservation of cells and tissues have been rising in recent time. Sometimes excessive use of cryoprotective agents may damage the original structure of preserved tissue. Therefore, cryoprotective agents should be used appropriately, and their quantities should be regulated. Excessive cooling may damage the membrane structure of the cell, so cooling should be done appropriately. Slow freezing and vitrification method are the two procedures that may be used for cryopreservation. Vitrification's main benefit is that it significantly reduces the likelihood of freeze damage, making it possible to maintain a high enough cell survival rate. Good manipulation skills are also required, and there is a considerable risk of infection with pathogenic pathogens. [As1] Fruitful cryopreservation of cells or tissues and their therapeutic use will require ongoing knowledge of the physical and chemical features which take place in the freezing and thawing cycle. We briefly discuss representative cryopreservation techniques and their clinical uses in this study.…

PMID: 36540535

Cryopreservation is a process that preserves organelles, cells, tissues, or any other biological constructs by cooling the samples to very low temperatures. The responses of living cells to ice formation are of theoretical interest and practical relevance. Stem cells and other viable tissues, which have great potential for use in basic research as well as for many medical applications, cannot be stored with simple cooling or freezing for a long time because ice crystal formation, osmotic shock, and membrane damage during freezing and thawing will cause cell death. The successful cryopreservation of cells and tissues has been gradually increasing in recent years, with the use of cryoprotective agents and temperature control equipment. Continuous understanding of the physical and chemical properties that occur in the freezing and thawing cycle will be necessary for the successful cryopreservation of cells or tissues and their clinical applications. In this review, we briefly address representative cryopreservation processes, such as slow freezing and vitrification, and the available cryoprotective agents. In addition, some adverse effects of cryopreservation are mentioned.…

PMID: 28462139

This paper discusses the role of ice crystal formation in causing or contributing to the difficulties that have been encountered in attempts to develop effective methods for the cryopreservation of some tissues and all organs. It is shown that extracellular ice can be severely damaging but also that cells in situ in tissues can behave quite differently from similar cells in a suspension with respect to intracellular freezing. It is concluded that techniques that avoid the formation of ice altogether are most likely to yield effective methods for the cryopreservation of recalcitrant tissues and vascularised organs.…

PMID: 32329718

Cryopreservation, the preservation of tissues at subzero temperatures, is a mainstay of brain banking that allows for the storage of brain tissue without the use of chemical fixatives. This is particularly important for molecular studies that are incompatible with tissue fixation. However, brain tissue is vulnerable to various forms of damage during the cryopreservation process, in particular due to the phase transition of water from a liquid to a solid state with the formation of ice crystals, which can disrupt cellular morphology. There is a critical need to characterize the effects of cryopreservation on brain cell structure at the microscopic level. In this review, we conducted a comprehensive literature search, identifying 97 studies that yielded 146 distinct observations of the effects of cryopreservation on neurohistology. We classified the reviewed studies into three main categories: cryofixation, freezing, and cryopreservation with cryoprotectants. Cryofixation techniques enable vitrification and excellent ultrastructural preservation of thin tissue samples but are limited in terms of the depth of tissue that can be preserved without ice artifacts. Freezing methods, particularly when applied to brain slices, can achieve rapid cooling rates that result in minimal ice artifacts detectable by light microscopy. Cryoprotectant-based approaches have the potential to reduce ice damage and achieve vitrification. For thin tissue samples, immersion in cryoprotectants has been found to be effective for structural preservation. However, for larger samples or the entire brain, perfusion of cryoprotectants is necessary to perform rapid distribution, and this has a more limited evidence base. In conclusion, while current cryopreservation methods can provide sufficient quality for some downstream applications, there is a need for improved techniques that enable the cryopreservation of larger brain tissue samples while maintaining excellent structural preservation.…

PMID: 39844781

Freezing is the most effective preservation technique for maintaining the quality and nutritional integrity of vegetables, particularly in tropical regions where postharvest losses are high. However, during long-term frozen storage, undesirable changes in color and texture often occur, reducing consumer acceptability and export quality. These alterations are linked to biochemical and physical mechanisms, including pigment oxidation, enzymatic activity, ice crystal formation, and cellular structure collapse. This review critically summarizes recent research on color and texture stability in frozen tropical vegetables such as taro stolon, lablab bean seeds, okra, and green beans, which were selected due to their economic importance in tropical regions, high moisture content, and pronounced susceptibility to postharvest quality deterioration during freezing and storage. The mechanistic insights are discussed in relation to processing factors such as blanching, freezing rate, and storage temperature (-20°C), along with advanced modeling approaches for predicting quality degradation. The review also highlights the role of natural antioxidants, pretreatments, and novel freezing technologies in improving color and textural stability, providing a foundation for future industrial and mechanistic research. Despite extensive research, an integrated mechanistic link between physicochemical changes, microstructural damage, and predictive modeling in tropical frozen vegetables under dynamic cold chains remains limited. This review synthesizes degradation pathways and combines kinetic, spectroscopic, and data-driven models for comprehensive quality prediction.…

PMID: 42255710

Flavor and textural changes are major quality challenges for prepared dishes, especially for precooked meat. However, studies mainly focused on raw meat and have not comprehensively evaluated integrated freezing and thawing methods. In this study, the effects of quick freezing with ultrasonic (QFU, 4.41 cm/h) combined with high-voltage electrostatic field-assisted thawing (HVEF) on the quality of precooked duck meat were investigated, in comparison to traditional freezing, including -18 °C freezing (CON, 1.0 cm/h), -40 °C quick freezing (QF, 2.07 cm/h), liquid nitrogen freezing (LNF, 8.16 cm/h) and thawing methods, including high-capacity refrigerator (HR), cool water flowing (CWF), and room temperature thawing (RT). The results demonstrate that with a higher freezing rate, QFU reduced the centrifugal loss of meat by 17.2%, improved textural attributes, and depressed the lipid and protein oxidation. Scanning electron microscopy showed that QFU and LNF produced orderly ice-crystal structures, with 70.5% of LNF ice crystals smaller than 12 μm². In addition, faster freezing rates were associated with a lower proportion of T23 water. The HVEF thawing rendered the textural properties of precooked meat closer to those achieved by CWF. The HR thawing resulted in a lower free water content in precooked meat, despite the longest thawing time. These results provide a reference for maintaining quality of precooked meat through the industrial supply chain.…

PMID: 42111849

With the sustained expansion of global meat consumption, advanced freezing and thawing technologies have become essential to preserve quality and extend shelf life within the food supply chain. This review systematically consolidates recent progress by examining fundamental principles, conventional techniques, emerging multi-physics methods (e.g., high-pressure-, ultrasound-, and electric field-assisted processing), and the integration of artificial intelligence (AI). It details the mechanism of ice-crystal formation and its impact on meat quality attributes. While conventional methods remain prevalent, their limitations in controlling ice crystallization are evident. Emerging technologies demonstrate superior capability in regulating ice morphology, thereby mitigating cellular damage. AI applications, including numerical simulation, quality monitoring via machine learning, and predictive modeling of thawing parameters, show considerable potential to enhance processing efficiency-though challenges in data scarcity and model generalizability remain. Collectively, these advancements form an integrated "theory-technology-intelligence" framework, supporting the development of more sustainable, efficient, and quality-focused meat processing systems.…

PMID: 41596994

To preserve the structure and quality of critical edible regions in frozen bighead carp (BHC) heads. Air freezing (AF, -30 °C), composite immersion freezing (CIF, -30 °C), and liquid nitrogen spray freezing (LNSF, -90 °C) were compared for the effects on the water status, ice morphology, microstructure, protein characteristics, and lipid oxidation of gill side flesh (GSF) and collar flesh (CF). Dendritic ice crystals formed in AF samples, fracturing collagen fibers. CIF and LNSF promoted spherical ice, preserving adipocytes and collagen structure. LNSF reduced water migration, maintained the α-helix content (27.68%), and suppressed protein unfolding in GSF, resulting in smoother and intact surfaces of the muscle bundles. LNSF treated CF showed the lowest values of malondialdehyde (0.27 mg/kg), acid value (1.53 mg/g), and peroxide value (5.01 mmol/kg). Overall, the quality of BHC heads was preserved by LNSF at -90 °C. This study establishes freezing technological for frozen fish heads.…

PMID: 41674698