Freezing plays an important role in food preservation and the emergence of rapid freezing technologies can be highly beneficial to the food industry. This paper reviews some novel food freezing ...technologies, including high-pressure freezing (HPF), ultrasound-assisted freezing (UAF), electrically disturbed freezing (EF) and magnetically disturbed freezing (MF), microwave-assisted freezing (MWF), and osmo-dehydro-freezing (ODF). HPF and UAF can initiate ice nucleation rapidly, leading to uniform distribution of ice crystals and the control of their size and shape. Specifically, the former is focused on increasing the degree of supercooling, whereas the latter aims to decrease it. Direct current electric freezing (DC-EF) and alternating current electric freezing (AC-EF) exhibit different effects on ice nucleation. DC-EF can promote ice nucleation and AC-EF has the opposite effect. Furthermore, ODF has been successfully used for freezing various vegetables and fruit. MWF cannot control the nucleation temperature, but can decrease supercooling degree, thus decreasing the size of ice crystals. The heat and mass transfer processes during ODF have been investigated experimentally and modeled mathematically. More studies should be carried out to understand the effects of these technologies on food freezing process.
Fruits and vegetables are rich in essential nutrients such as minerals, vitamins, and antioxidants; however, they have short shelf life. Freezing is a superior method of preservation compared to ...other techniques with respect to nutrient retention and maintenance of sensory attributes. However, several physical and textural quality changes associated with freezing and thawing pose a serious problem to the quality of frozen products. Some of the disadvantages associated with the currently employed methods for freezing fruits and vegetables include low rates of heat exchange in blast freezers, shape limitation in plate freezers, high cost of operation in cryogenic freezing, and freezing solution dilution in immersion freezing. Therefore, novel freezing technologies have been developed to achieve controlled ice nucleation and crystallization, enhanced freezing rate, decreased phase transition time, and maintained temperature stability. This review discusses some of the most recent approaches employed in freezing and points to their adoption for maintaining the quality of fruits and vegetables with extended storage.
The reasonable prediction of ground frost heave provides guiding significance for tunnel construction that uses artificial ground freezing technique. Single-pipe freezing theory, which considers the ...freezing point of soil and assumes the constant surface temperature of a freezing pipe, is suggested for solving the radius of the freezing front before the closure of the frozen wall. By contrast, the radius of the freezing front after the closure of the frozen wall can be calculated using flat-panel freezing theory, which considers the freezing point of soil and determines the average temperature of the freezing pipe circle. On the basis of these suggestions and the analytical prediction proposed by Cai et al. (2014), an improved analytical prediction of ground frost heave was established by the stochastic medium theory according to the formation process of the frozen wall. The improved analytical prediction was applied to an actual tunnel freezing project. Then, the heaving and horizontal displacements of the ground surface are obtained, which agree well with the field-measured data. The effectiveness and practicality of the improved analytical prediction are verified in this study.
The phenomenon of freezing point depression in frozen soils results in the co‐existence of ice and liquid water in soil pores at temperatures below 273.15 K (0°C), and is thought to have two causes: ...(a) capillary and adsorption effects, where the phase transition relationship is modified due to soil‐air‐water‐ice interactions, and (b) solute effects, where the presence of salts lowers the freezing temperature. The soil freezing characteristic curve (SFC) characterizes the relationship between liquid water content and temperature in frozen soils. Most hydrological models represent the SFC using only capillary and adsorption effects with a relationship known as the Generalized Clapeyron Equation (GCE). In this study, we develop and test a salt exclusion model for characterizing the SFC, comparing this with the GCE‐based model and a combined salt‐GCE effect model. We test these models against measured SFCs in laboratory and field experiments with diverse soil textures and salinities. We consistently found that the GCE‐based models under‐predicted freezing‐point depression. We were able to match the observations with the salt exclusion model and the combined model, suggesting that salinity is a dominant control on the SFC in real soils that always contain solutes. In modeling applications where the salinity is unknown, the soil bulk solute concentration can be treated as a single fitting parameter. Improved characterization of the SFC may result in improvements in coupled mass‐heat transport models for simulating hydrological processes in cold regions, particularly the hydraulic properties of frozen soils and the hydraulic head in frozen soils that drives cryosuction.
Plain Language Summary
When the ground freezes during the winter, not all the water stored in the soil turns into ice, which is because soil particles hold tightly onto some of the water making it impossible to freeze the water and because of the presence of dissolved salts within the soil pore water. The presence of unfrozen water in frozen soils determines the hydraulic properties of the soil which are vital for models of flood forecasting during spring melt, snowmelt infiltration for crop growth and the mechanical properties that determine the stability of the ground for infrastructure in cold regions. In this study, we use laboratory and field experiments, as well as different theoretical models to understand the effect of either or both dissolved salt and soil particles on the amount of unfrozen water stored in the frozen soil, and we suggest that dissolved salts may often be the dominant control. We propose a new relationship for this phenomenon that could improve cold regions hydrological models.
Key Points
The soil freezing characteristic curve is an important property of frozen soils, and is required by cold regions hydrological models
The Generalized Clapeyron Equation (GCE) is found to under predict freezing point depression
A salt exclusion model and combined salt‐GCE model perform well in simulating observed soil freezing characteristic curves
Foods have been commercially frozen for over 140 years. While improper frozen storage often causes food quality loss, the frozen damage induced by ice crystal growth is a serious problem. Freezing ...point (FP) regulation that promotes and inhibits ice nucleation, and controls ice crystal growth and recrystallization, may alleviate this problem. Some naturally sourced biosubstances with eco-friendly, green, nontoxic and highly effective characteristics are verified to regulate FP, showing potential for application in foods and food-related areas.
This review introduces three groups of FP-regulating biosubstances, including ice-nucleating proteins (INPs), anti-freezing proteins (AFPs) and natural deep eutectic solvents (NADES). Existing knowledge of these biosubstances and updated information concerning their mechanisms for regulating FP are summarized. In addition, current applications of these natural FP regulators in foods or in food-related areas are presented, involving food processing, packaging and transgenic foods. Future applications of these biosubstances in the food and food-related researches are briefly discussed.
The effect of natural FP regulators in improving food quality is worthy of further investigation into more extensive food applications, especially for INPs and NADES. The current review indicates that natural FP regulating biosubstances reveal application potential in foods and food-related areas. Future studies should mainly focus on bio-based or bio-inspired anti-freezing, micro/none ice-based cold storage and energy conservation in the food and food-related researches.
•Ice-nucleating proteins effectively elevate freezing points.•Anti-freezing proteins and natural deep eutectic solvents reduce freezing points.•Ice-binding proteins regulate freezing points through special function domains.•Natural freezing point regulators can be applied in the food industry.•This is an updated review on natural freezing point regulators in food area.
Freezing temperature parameterization significantly impacts the heat balance at sea‐ice bottom and, consequently, the simulated sea‐ice thickness. Here, the single‐column model ICEPACK was used to ...investigate the impact of the freezing temperature parameterization on the simulated sea‐ice thermodynamic growth during the MOSAiC expedition from October 2019 to September 2020. It is shown that large model errors exist with the standard parameterization and that different formulations for calculating the freezing temperature impact the simulated sea‐ice thickness significantly. Considering the winter mixed layer temperature, a modified parameterization of the freezing point temperature based on Mushy scheme was developed. The mean absolute error (ratio) of simulating sea‐ice thickness for all buoys reduces from 7.4 cm (4.9%) with the “Millero” scheme, which performs the best among the existing schemes in the ICEPACK model, to 4.2 cm (2.9%) with the new developed scheme.
Plain Language Summary
The heat transferred from the ocean to the sea‐ice influences the growth and melting of the sea‐ice. Freezing temperature is an essential parameter for calculating the heat transfer. Nevertheless, few studies have attempted to evaluate the impact of different freezing temperature parameterizations on the simulated sea‐ice thermodynamic growth. This study uses observed atmosphere and ocean data to force a single‐column model. Using different methods to calculate the freezing temperature significantly impacts the simulated sea‐ice thickness. After a series of testing and comparisons, we have developed a modified parameterization of freezing temperature that significantly reduces the simulation deviation from the observations.
Key Points
Different parameterizations of the freezing temperature significantly influence the simulated sea‐ice thickness
A modified‐Mushy parameterization method is developed for the freezing temperature, significantly improving ice thickness simulation
The control of freezing temperatures throughout the artificial ground freezing (AGF) process is always difficult. An overly high temperature of the circulating refrigerant may lead to insufficient ...frozen soil strength, while an overly low temperature may cause unnecessary energy waste, and even excessive pore ice may damage the soil structure and reduce the frozen soil strength. What's more, overly freezing may damage buildings on the surface. Therefore, it is of great significance to study the optimum freezing temperature (OFT), which is very important for better and more energy-efficient employment of the AGF method. In this paper, we use uniaxial compression and direct shear tests to obtain dynamic mechanical parameters in the soil freezing process. After the analysis of varying mechanical parameters by the entropy weight TOPSIS principal component analysis method, the results show that the interval range of OFT for saturated and unsaturated sandy gravel is − 10 °C, − 15 °C and − 15 °C, − 20 °C, respectively. The findings indicate that, in the AGF method, a lower temperature is not always preferable. According to the results, constructive measures to optimize the temperature field distribution in the AGF method are proposed. The research results will contribute to the assessment of the safety and efficiency of AGF projects.
•Impact freezing for water droplets supercooled deeply is carried out.•The nucleation in different dynamic phases has a significant influence on the final freezing morphology.•There are multiple ...freezing morphologies under constant conditions due to the uncertain nucleation time.•The relationship between freezing morphology and freezing type is proposed.•Three kinds of impact freezing process for room temperature water droplets are observed.
The freezing morphologies and types for droplets at supercooled (−15 °C) and room temperature (20 °C) to impact onto a cold and polished aluminum substrate are investigated experimentally in this paper. It is found that the nucleation in different dynamic processes has a significant effect on the final freezing morphology and there are multiple freezing morphologies under constant conditions due to the uncertain nucleation time. Thus, based on the final freezing shapes, a basic classification for the different freezing morphologies is presented in terms of basin, pancake and semisphere; and three corresponding freezing types, including instantaneous freezing, non-instantaneous freezing and quasi-static freezing, are proposed based on the nucleation in distinct dynamic phases. Furthermore, the relative number of nucleation drops is taken as a function of time, and then the probability of various freezing morphologies and types in each experimental condition is provided. As a result, for both of the supercooled and room temperature water droplets, although the relative number of nucleation drops have roughly the same variational tendency for impact freezing, the nucleation time and the probability of various freezing morphologies remain different, for example, no basin shapes were attained in the case of room temperature water droplets under the experimental conditions of the current study. Meanwhile, the experimental results show that there are obvious diversities on freezing process. Three kinds of freezing processes, including traditional supercooled water freezing process, are presented for the impact freezing of room temperature droplets, which is mainly determined by the nucleation time. Therefore, for further studies of ice formation, the present results suggest that not only the effect of kinetics and heat transfer but also the influence of the nucleation time should be considered, particularly for the large droplets supercooled deeply.
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