Air Freeze Research Articles

Insights into the potential mechanism of diversified freezing techniques' influence on quality of golden pompano (Trachinotus ovatus): Focus on freezing speed, ice crystal morphology, water migration, and texture properties

The influences of air freezing (AF), liquid nitrogen freezing (LNF), immersion freezing (IF), magnetic field-assisted immersion freezing (MIF), and ultrasound-assisted immersion freezing (UIF) on the freezing time, water holding capacity, texture profile analysis (TPA), and microstructure of the golden pompano (Trachinotus ovatus) muscle was investigated. The findings indicated that the MIF and UIF groups were more effective in reducing the freezing time than other freezing method, with 84.35% and 85.81% shorter than that of AF, respectively. Among all the treatments, MIF had the best muscle integrity and closely packed myogenic fibers, which were more beneficial for maintaining the water holding capacity, textural properties, and color of the golden pompano muscle. Among all the groups, the MIF quality was the closest to unfrozen samples. Therefore, MIF effectively reduced the size of ice crystals, and inhibited the quality deterioration of frozen golden pompano.

Contribution to energy conservation and quality improvement of frozen pork via contact/contactless immersion freezing in NaCl solution

High energy consumption and quality deterioration are major challenges in the meat freezing process. In this study, the energy consumption and qualities of frozen pork were investigated using three freezing methods: nonpackaged pork air freezing (NAF), contactless immersion freezing (PIF) and contact immersion freezing (NIF) with NaCl solution as a refrigerant. The results indicated that NIF could improve the energy conservation and freezing efficiency in >4 freezing treatment-times by increasing the unfrozen water content, decreasing the frozen heat load, shortening the freezing time and reducing evaporation loss. NIF could also increase the a* value of the pork and improve the water-holding capacity by facilitating the conversion of free water to immobilized-water. The two immersion freezing methods could reduce freezing-thawing loss and protein loss by alleviating muscle tissue freezing damage. These results provide a suitable application of immersion freezing with energy conservation, high efficiency and good quality of frozen-pork.

Effect of low-frequency electric field assisted freezing on ice crystals of tilapia fish protein

The mechanism by which low-frequency alternating electric fields affect ice crystals and quality of aquatic products remain unclear. To study the effect of low-frequency electric field freezing (LF-EFAF) on product ice crystals, differences between LF-EFAF treated samples and air freezing (AF) were compared. The results showed that LF-EFAF increased the subcooling of fish protein by 0.3 °C and doubled the freezing time compared to AF. The equivalent diameter and cross-sectional area of LF-EFAF samples were reduced by up to 20% and 35% respectively, compared to AF samples. Moisture distribution of results showed that LF-EFAF restrained the increase in free water content of fish proteins. The LF-EFAF had a positive effect on the size and morphology. This resulted in less mechanical damage to the muscle fibres, which led to better water retention and inhibited moisture migration. Therefore, LF-EFAF can be an effective means of fish proteins preservation.

Role of ultrasonic freezing­treated pork dumpling filling during frozen storage: Insights from protein oxidation, aggregation, and functional properties

The effects of air freezing (AF), immersion freezing (IF), and ultrasonic freezing (UF) on the oxidation, aggregation, and functional properties of myofibrillar protein (MP) in pork dumpling filling during frozen storage were investigated. The findings demonstrated that, compared to AF and IF treatments, UF treatment had higher total and reactive sulfhydryl content, solubility, and absolute zeta potential. Conversely, it exhibited lower values in carbonyl content, dityrosine content, turbidity, and particle size within the same storage time (p < 0.05). SDS-PAGE revealed that UF treatment delayed the oxidation and excessive aggregation of MP during frozen storage. Moreover, samples treated with UF at 180 days (d) displayed similar functional and qualitative characteristics to those treated with IF at 90 d or AF at 60 d, as per the hierarchical cluster analysis findings. In conclusion, UF effectively delayed the oxidation, aggregation, and loss of functional properties of MP in pork dumpling filling during frozen storage.

Effects of Liquid Nitrogen Freezing, Immersion Freezing, and Air Freezing on Properties of Perca fluviatilis Fillets and Analysis of Potential Protein Markers Based on Label-Free Proteomics

The effects of liquid nitrogen freezing (LNF), immersion freezing (IF), and air freezing (AF) combined with thawing in running water at 20°C on the quality of Perca fluviatilis fillets were investigated using label-free proteomics technology. The ice crystal equivalent diameter (12.30±0.33 μm) and ice crystal area ratio (7.61±2.81%) of LNF were significantly lower than IF and AF (P < 0.05). The ice crystals of LNF were small and evenly distributed, and the mechanical damage to the cell structure is small. LNF samples were closer to fresh samples regarding texture. Proteomic analysis identified a total of 11 differentially abundant proteins (DAPs) associated with LNF, IF, and AF. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that these DAPs were primarily catalytic proteins, metabolic enzymes, and structural proteins involved in metabolic pathways such as pyruvate metabolism, glycolysis, and arginine and proline metabolism. Among them, tubulin beta chain (A0A8C3G6F1), carbonic anhydrase (A0A2P1JP97), immunoglobulin-like and fibronectin type III domain-containing protein 1 (A0A484DE91), and tubulin are predicted to serve as potential protein markers for freezing, thawing loss, hardness, and springiness of Perca fluviatilis fillets post-thawing. These findings provide a basis for further research into the quality change induced by protein degradation of frozen Perca fluviatilis.

Effects of different freezing methods on muscle qualities and myofibrillar protein properties of red drum (Sciaenops ocellatus) during storage

The freezing of aquatic products without causing significant changes in quality is recently attracting much attention. In this study, the effects of air freezing (AF, -20 °C), blast freezing (BF, -35 °C), liquid nitrogen freezing (LNF), and immersion freezing (IF, -35 °C) by 20 % ethanol, 20 % propylene glycol, 10 % glycerol, and 10 % sodium chloride aqueous solutions, respectively, on muscle qualities and myofibrillar protein properties of the red drum were investigated. The results indicated that the freezing rate of IF was 2.66 cm/h, which was 6.33 times higher than that in AF groups. Compared with AF and BF, the ice crystals were smaller and more uniformly shaped, with properties of lower water migration and less texture softening after cryogenic liquid freezing of IF and LNF group aquatic products. Immersion freezing showed the same superiority in maintaining the freshness of fish fillets and retaining the protein structure as liquid nitrogen storage. Overall, IF has similar effects to LNF in maintaining muscle qualities and myofibrillar protein properties. This study describes a new freezing method that uses 20 % ethanol, 20 % propylene glycol, 10 % glycerol, and 10 % sodium chloride aqueous solutions as immersion freezing medium. The multi-compound freezing medium has the potential to be used for the freezing of aquatic products.

The impact of pressure-shift freezing on the three-dimensional network structure and properties of myofibrillar proteins in surimi gel derived from freshwater fish

Freezing treatment can prolong the shelf life of surimi products, but it will lead to deterioration of surimi gel quality. This study compared the effects of three different processing methods — non-freezing processing (control), conventional air freezing (CAF), and pressure-shift freezing (PSF) — on the three-dimensional (3D) network structure of grass carp surimi gel. After PSF treatment, the pores in the 3D gel network structure were denser compared to the control group which facilitates interaction of water and network structure. Furthermore, the ultraviolet and fluorescence spectral analysis indicated that PSF treatment mitigates the decline in stability of the tertiary structure of myofibrillar protein (MP) during freezing. The microstructure of MP showed that PSF treatment promotes the cross-linking of MP to form protein aggregates and then promotes the gelation of MP. Industrial relevancePSF can increase the commodity value of low-value freshwater fish products and has potential in the development of new products of surimi gels. This study reported a novel idea and theoretical basis for the application of PSF technology in the frozen food and aquatic product processing industry.

Changes in properties of myofibrillar protein and myofibrillar protein gel from freshwater fish after low-temperature and high-pressure collaborative treatment

This study investigated the effects of low-temperature and high-pressure collaborative and conventional air freezing (CAF) on myofibrillar protein (MP) characteristics from grass carp. Turbidity, solubility, and particle size analysis showed that the pressure shift freezing (PSF) treatment could inhibit the formation of large MP aggregates to a certain extent during freezing. Chemical interaction studies unveiled that PSF treatment not only mitigates damage to the inherent structure of MP during freezing but also enhances its crosslinking ability. Microstructure analysis revealed a densely woven fibrous protein network structure within the MP gel in the PSF group. MP gel with fiber shape network structure in the PSF group exhibited stronger water-holding capacity and mechanical properties compared to the CAF group having an incomplete protein network structure. This suggests that the combined application of low-temperature and high-pressure treatment holds promising potential for utilization in the surimi gel processing industry and aquatic products processing.Industrial relevance: The quality and safety of food are closely related to the commodity value of food. Combined low-temperature and high-pressure treatment can enhance the commodity value of low-value freshwater fish products and has potential in surimi gel new product development. This study provides theoretical guidance for high-pressure and low-temperature collaborative processing and industrial production of related aquatic products.

Freezing and Mechanical Failure of a Habitat-Forming Kelp in the Rocky Intertidal Zone.

Kelp and other habitat-forming seaweeds in the intertidal zone are exposed to a suite of environmental factors, including temperature and hydrodynamic forces, that can influence their growth, survival, and ecological function. Relatively little is known about the interactive effect of temperature and hydrodynamic forces on kelp, especially the effect of cold stress on biomechanical resistance to hydrodynamic forces. We used the intertidal kelp Egregia menziesii to investigate how freezing in air during a low tide changes the kelp's resistance to breaking from hydrodynamic forces. We conducted a laboratory experiment to test how short-term freezing, mimicking a brief low-tide freezing event, affected the kelp's mechanical properties. We also characterized daily minimum winter temperatures in an intertidal E. menziesii population on San Juan Island, WA, near the center of the species' geographic range. In the laboratory, acute freezing events decreased the strength and toughness of kelp tissue by 8-20% (change in medians). During low tides in the field, we documented sub-zero temperatures, snow, and low canopy cover (compared to summer surveys). These results suggest that freezing can contribute to frond breakage and decreased canopy cover in intertidal kelp. Further work is needed to understand whether freezing and the biomechanical performance in cold temperatures influence the fitness and ecological function of kelp and whether this will change as winter conditions, such as freezing events and storms, change in frequency and intensity.

Tracking protein aggregation behaviour and emulsifying properties induced by structural alterations in common carp (Cyprinus carpio) myofibrillar protein during long-term frozen storage

The effect of ultrasound-assisted immersion freezing (UIF), air freezing (AF), and immersion freezing (IF) on the protein structure, aggregation, and emulsifying properties of common carp (Cyprinus carpio) myofibrillar protein during frozen storage were evaluated in the present study. The result showed that, compared with AF and IF samples, UIF sample had higher reactive/total sulfhydryl, protein solubility, and lower protein turbidity (P < 0.05), indicating that UIF was beneficial to inhibit protein oxidation and aggregation induced by frozen storage. UIF inhibited the alteration of secondary structure and tertiary structure during frozen storage. Meanwhile, UIF sample had higher emulsifying activity index, and smaller emulsion droplet diameter than AF and IF samples (P < 0.05), suggesting that UIF was beneficial for maintaining the emulsifying properties of protein during storage. In general, UIF is a potential and effective method to suppress the decrease in protein emulsifying properties during long-term frozen storage.

Effect of liquid nitrogen spray freezing on the ice crystal size and quality of large yellow croaker

Large yellow croakers (Larimichthys crocea) were frozen by liquid nitrogen spray freezing (LNSF), liquid immersion freezing (LIF), and air freezing (AF), and the freezing rate, ice crystal size and product qualities were compared. LNSF was found to be a promising freezing technology because of the significantly (P < 0.05) shortest freezing time, smallest ice crystal, and best overall product quality. Then, the effect of processing parameters during LNSF on freezing characteristics, and microstructure and qualities of samples was studied. Freezing time was reduced by decreasing freezing temperature and increasing air velocity. A size uniformity index was proposed in this study to evaluate the distribution uniformity of ice crystals. The minimum cross-sectional area (605.83 μm2) with the best size uniformity was achieved at a freezing temperature of −90 °C, a final temperature of −30 °C, and an air velocity of 4 m/s, showing a reduction of 50.90% as compared to the maximum (1233.77 μm2). The qualities of samples frozen by LNSF with the aforementioned parameter values were well maintained and met the industrial standard. Therefore, the developed LNSF protocol was recommended for the industrial application for large yellow croaker.

Insight into the mechanism of pressure shift freezing on water mobility, microstructure, and rheological properties of grass carp surimi gel

This study found that using pressure shift freezing (PSF) treatment could suppress the decline in the quality of grass carp surimi gel during the conventional air freezing (CAF) process, and even improve the original properties of surimi gel. The surimi gel breaking force was about 2.5 times followed by PSF treatment (4.5 N) compared to the CAF group (1.8 N). The formation of small ice crystals in the PSF group reduced the mechanical damage to the sample structure compared to the large ice crystals formed in CAF groups. In addition, PSF treatment was found to be responsible for the change in protein and water mobility in surimi gel, which in turn positively influences the physicochemical properties of surimi gel. Industrial relevanceThe output of this study revealed the significance of PSF technology in the surimi gel processing and meat processing industry. The development of new products and the use of new resources are very important in addressing the global food crisis and resource shortages. The application of PSF technology has also laid a foundation for freshwater surimi gel products to replace seawater surimi gel products.

Risk Assessment of Freezing–Thawing Hazards in the Daxing’anling Forest Region

The Daxing’anling forest region represents a crucial forestry hub in China and confronts some of the nation’s most severe freezing–thawing hazards. This study delved into the temporal trends and spatial distributions of various parameters related to freezing and thawing, including air temperature, ground surface temperature, freezing index, thawing index, and freezing–thawing frequency. Furthermore, this study assessed and delineated freezing–thawing hazards within the research area. The findings revealed a rapid increase in air temperature and ground surface temperature within the Daxing’anling forest region yet a lower rate of increase in ground surface temperature compared to Northeast China. Latitude had the strongest influence on mean annual air temperature, mean annual ground surface temperature, air freezing index, air thawing index, ground surface freezing index, ground surface thawing index, air freezing–thawing frequency, and ground surface freezing–thawing frequency, followed by longitude and elevation. Overall, freezing index, and air freezing–thawing frequency increased from south to north, whereas mean annual air temperature, mean annual ground surface temperature, air thawing index, ground surface thawing index, and ground surface freezing–thawing frequency decreased from south to north. The assessment outcomes underscore the importance of closely monitoring freezing–thawing hazards in regions north of the 50th parallel.

Effects of freezing methods on physicochemical properties, protein/fat oxidation and odor characteristics of surimi gels with different cross-linking degrees

This work investigated the effects of liquid nitrogen immersion freezing (LNF), −35 °C air freezing (AF-35℃) and −18 °C air freezing (AF-18℃) on the physical and chemical characteristics and flavor quality of surimi gels with different cross-linking degrees. Compared to AF-35 °C and AF-18 °C, LNF was shown to considerably delay the texture deterioration and water migration of frozen gels, as well as the accumulation of thiobarbituric acid reactive substance values and carbonyl contents. Additionally, an appropriate increase of cross-linking degree (45.83 to 62.99%) was found able to improve gel properties and inhibit quality deterioration during freezing. Moreover, LNF-treated gels were closer to fresh gels in the amount of volatile compounds, in contrast to most significant negative aroma changes in AF-18℃-treated gels. Furthermore, 29, 29 and 31 key differential volatile compounds were screened for gels with a cross-linking degree of 29.66, 45.83 and 62.99%, respectively, mainly including aldehydes, alcohols and esters.

Comparison of air freezing, liquid immersion freezing and pressure shift freezing on freezing time and quality of snakehead (Channa Argus) fillets

The objective of this study was to investigate the freezing time and quality differences in Snakehead fillets frozen by pressure shift freezing (PSF), conventional air freezing (AF) and liquid immersion freezing (LIF) at −20 °C, −40 °C and − 60 °C, respectively. The results showed that liquid immersion freezing at −60 °C maintained the quality best, with a freezing time of 3.62 min and the cross sectional area of 209.11 um2. Air freezing at −20 °C had the longest freezing time (184.58 min) and the largest cross sectional area (4470.79 um2), and lowest hardness and springiness of the fillets. Pressure shift freezing did not demonstrate the well established advantages of maintaining better product quality found in similar technique with some other foods. The samples of pressure shift freezing also had higher thawing loss and free water ratio after thawing. Therefore, the liquid immersion freezing at lower temperatures was demonstrated to better maintain the quality of frozen products and held significant potential for commercial application. Industrial relevanceFreezing is a widely used method for extending the shelf life of aquatic products, but some freezing methods, especially the slower ones, often lead to the decrease in the quality and commercial value of frozen products during storage. This paper explored the comparison of industrially used freezing techniques (air freezing and liquid immersion freezing) with the novel pressure shift freezing technique. Liquid immersion freezing at −60 °C was found to be the preferred freezing method for Snakehead fillets, which maintained better frozen product quality, with a simple freezing process and low cost.

Comparison of immersion freezing, osmo‐dehydrofreezing and air freezing on freezing parameters and physicochemical properties of mango (Mangifera indica L.)

SummaryEffects of immersion freezing (IF), osmo‐dehydrofreezing (ODF) and air freezing (AF) on freezing parameters and physicochemical properties of frozen mango were studied. Results showed that IF had the shortest freezing time, followed by ODF and AF. In ODF groups, dehydrofreezing in 50% glucose (G‐50) showed the highest quality. Mangoes pre‐treated in glucose had higher quality than those pre‐treated in trehalose. The quality of osmo‐dehydrofrozen mangoes was more affected by freezing rate than by difference between freezing temperature and the glass transition temperature (T−). Compared with the AF, IF in 60% ethylene glycol (EG‐60) and ODF in G‐50 significantly improved the quality of mangoes, including colour change and drip loss reduced by 43.7%, 28.6%, 41.4% and 19.6%, hardness increased by 540.7% and 413.6%, and contents of vitamin C and total phenol increased by 30.7%, 24.3%, 18.3% and 6.4%, respectively. Overall, IF in EG‐60 was the most favourable method for frozen mangoes.

Effect of Heat Transfer Medium and Rate on Freezing Characteristics, Color, and Cell Structure of Chestnut Kernels

This paper compared the effects of air and nitrogen on the freezing characteristics, color, and cell structures of chestnut kernels at different rates of heat transfer and adopted liquid nitrogen spray quick-freezing (NF-40 °C/-60 °C/-80 °C/-100 °C) and still air freezing (AF-20 °C/-40 °C) as the freezing methods. The ratio of heat transfer coefficients in N2 groups was two times as high as those in air groups, and NF-100 °C and NF-80 °C showed better freezing characteristics, good protection for cytoskeletons, and the color was similar to those of the fresh group. Taking both Multivariate Analysis of Variance (Principal Components Analysis and Cluster Analysis) and economic factors, NF-80 °C can be used as a suitable method for chestnut kernel freezing. When the ambient freezing temperature was lower than Tg, both NF and AF treatment groups presented poor quality. The rate and medium of heat transfer jointly influenced the freezing characteristics and quality. The former had a greater effect than the latter, however.

Synergism effect of low voltage electrostatic field and antifreeze agents on enhancing the qualities of frozen beef steak: Perspectives on water migration and protein aggregation

In this study, a synergistic strategy utilizing low-voltage electrostatic field (LVEF) and antifreeze agents (4% sucrose +4% sorbitol) was proposed to reduce quality deterioration of prepared beef steak during freezing. The effects of the synergistic treatment on the water holding capacity, texture and muscle ultrastructure, myofibrillar protein (MP) aggregation was studied. Results showed that co-treatment significantly reduced thawing losses (about 41%) by preventing the migration of immobilized water to free water and reduced ice crystal size compared to air freezing (AF). In addition, co-treatment positively affected texture properties by shortening the gap between muscle fibers and maintaining the structural integrity of the sarcomeres. Moreover, synergistic treatment inhibited the unfolding of the MP structure and the formation of MP aggregates by strengthening non-covalent interactions. These results seem to demonstrate that LVEF can remarkably enhance the effects of cryoprotectants, which provides a new perspective on food cryoprotection. Industrial relevanceFreezing is the most common method of preserving prepared meat products, however, the formation of large ice crystals and the denaturation of muscle proteins are two major causes of quality deterioration during conventional air-freezing. In this study, a LVEF system was applied to the freezing process of prepared meat products, and a comparative and synergistic study was carried out with the current industry common chemical freezing protection methods (addition of antifreeze). The results showed that the synergistic treatment greatly promoted the nucleation of food products, shortened the phase transition time, reduced the ice crystal size and effectively reduced the thawing losses by approximately 41%. The green freezing system can be easily adapted to scenarios such as cold chain transport and cold storage. And the LVEF intensifies the interaction of antifreeze molecules with protein and water molecules, which seems to open up even more possibilities in cryopreservation.

Effects of Ultrasound-Assisted Immersion Freezing on the Protein Structure, Physicochemical Properties and Muscle Quality of the Bay Scallop (Argopecten irradians) during Frozen Storage.

In this study, the comparison effects of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power, immersion freezing (IF), and air freezing (AF) on the protein thermal stability, protein structure, and physicochemical properties of adductor muscle of scallop (Argopecten irradians) (AMS) during frozen storage were investigated. Principal component analysis and the Taylor diagram were used to comprehensively analyze all the indicators tested. The results showed that the UIF at 150 W (UIF-150) treatment was the most effective way to delay the quality deterioration of AMS during 90-day frozen storage. This was mainly because, compared to AF and IF treatments, UIF-150 treatment more effectively minimized the changes in the primary, secondary and tertiary structures of myofibrillar proteins, and it preserved the protein thermal stability of AMS by producing small and regular ice crystals in the AMS tissue during the freezing process. Moreover, the results of physicochemical properties indicated that UIF-150 treatment significantly inhibited the fat oxidation and microbiological activities of frozen AMS, and it finally maintained the microstructure and texture of AMS during frozen storage. Overall, UIF-150 has potential industrial application prospects in the rapid freezing and quality preservation of scallops.

Influence of the pressure shift freezing and thawing on the microstructure of largemouth bass

The objective of this study was to use a new self-cooling laboratory system for carrying out the pressure shift freezing (PSF) and evaluate the influence of PSF at 150 MPa on the microstructural properties of largemouth bass relative to liquid immersion freezing (LIF) and conventional air freezing (CAF). CAF, LIF and PSF showed average total freezing times of 176 ± 7.4, 65.3 ± 6.8 and 23.2 ± 3.1 min, and the cross sectional area of ice crystals in the muscle were 1002 ± 778, 501 ± 248 and 143 ± 50.6 μm2, respectively, demonstrating a significant reduction in crystal size to be associated with PSF. It was observed that damage caused by the ice crystals during the freezing to the muscle microstructure was irreversible. The thawing and cooking losses of largemouth bass after the freezing were lower for PSF as compared to the other two freezing methods. PSF reduced the damage to myocytes and resulted in lower drip loss due to reduced microstructure disruption due to their small ice crystals, thereby maintaining the muscle tissue to better retain the fluids. Color and texture properties were less affected by PSF. Industrial relevanceFreezing is the most used preservation method for aquatic products. Rapid freezing results in better texture retention while the slow freezing damages the product texture because of the formation of extracellular large ice crystals developed during the freezing process. Thus, the nature of freezing affects the quality of frozen foods. Successful freezing processes aim at employing rapid freezing conditions which result in the formation of small ice crystals. Pressure shift freezing (PSF) is a novel technique with advantages of high degree of super-cooling, short phase transformation time, and results in very small ice crystals. This study makes use of a laboratory self-cooling system to carryout PSF of largemouth bass. This cooling system overcomes the limitation of previous studies on PSF which are expensive, limited to small size and impractical for commercial exploitations. The cooling system employed in this study can be easily adapted to large-scale production of PSF aquatic products. Test results provide a basis for the commercial exploitation of PSF for largemouth bass and such other aquatic foods for driving the quality advantage.