Large Ice Crystals Research Articles

Effect of freezing rates on α-amylase enzymatic susceptibility, in vitro digestibility, and technological properties of starch microparticles

The aim of this study was to evaluate the effect of freezing rates using direct (LF: Liquid nitrogen) and indirect (RF: Cryogenic refrigerator and UF: ultra-freezer) methods at temperatures of (−20, −80, and − 196 °C) on the enzymatic susceptibility with α-amylase for microparticles. In vitro digestibility parameters and technological properties were also analyzed. Lower rates resulted in larger ice crystals, damaging the starch structure. Hydrolysis was more pronounced at slower rates RF: 0.07 °C/min and UF: 0.14 °C/min, yielding maximum values of RDS: 37.63% and SDS: 59.32% for RF. Type A crystallinity remained unchanged, with only a noted increase in crystallinity of up to 6.50% for FR. Starch pastes were classified as pseudoplastic, with RF exhibiting superior textural parameters and apparent viscosity. (RF: 7.18 J g−1 and UF: 7.34 J g−1) also showed lower values of gelatinization enthalpy. Freezing techniques were viable in facilitating the diffusion of α-amylase and reducing RS by up to 81%.

Effect of extruded wheat bran on the volatility and physical–chemical properties of bread during frozen storage

AbstractBackground and ObjectivesAt present, there are no sufficient data in the literature about the effect of extruded wheat bran on the volatility and physical–chemical properties of bread during frozen storage. Therefore, the current study aimed to investigate the effect of extruded wheat bran on the volatile components and physical–chemical properties of bread during frozen storage.FindingsFrozen storage could effectively extend the shelf‐life of bread. After 20 days of storage, the specific volume and cohesion of the control breads decreased significantly (2% and 21.55%, respectively). Moreover, the hardness and amylopectin retrogradation degree increased significantly (81.56%). After 30 days of storage, the amylopectin retrogradation degree of extruded wheat bran breads significantly increased (161%). After 40 days of storage, the cohesion of extruded wheat bran breads decreased significantly (7.67%). Extruded bran was conducive for improving bread stability during frozen storage. The transverse relaxation times (T2) of extruded wheat bran bread were shorter than those of the control bread. Bran inhibited water molecule migration and reduced the rate of bread quality deterioration. Further, 27 volatile components were detected in the control bread and 32 volatile components were detected in extruded wheat bran breads. The volatile components of all breads did not change significantly within the first 30 days of storage. Thereafter, the concentration of some volatile compounds decreased.ConclusionThe addition of extruded wheat bran significantly affected the volatility and physical–chemical properties of bread during frozen storage. The volatility and physical–chemical properties of extruded wheat bran bread changed gradually during frozen storage. The presence of bran inhibited water molecule migration and the formation and recrystallization of large ice crystals, and reduced the rate of bread quality deterioration during frozen storage.Significance and NoveltyThis study aimed to provide a reference for research on the storage and long‐term preservation of extruded wheat bran bread after production.

The Impact of Gravity Waves on the Evolution of Tropical Anvil Cirrus Microphysical Properties

AbstractAnvil cirrus generated by deep convection covers large fractions of the tropics and has important impacts on the Earth's radiation budget and climate. In situ measurements made with high‐altitude aircraft indicate a rapid transition in ice crystal size distributions and habits as anvil cirrus ages. We use numerical simulations to investigate the impact of high‐frequency gravity waves on the evolution of anvil cirrus microphysical properties. The impacts of both monochromatic gravity waves and ubiquitous stochastic mesoscale temperature fluctuations are simulated. In both cases, the interplay between wave‐driven temperature fluctuations, deposition growth/sublimation, and sedimentation causes accelerated removal of both small ice crystals (diameters less than about 10 μm) and large crystals (diameters larger than ≈30 μm). These changes are consistent with the observed evolution of anvil cirrus microphysical properties. The Kelvin effect (higher saturation vapor pressure over curved surfaces) is a critical factor in the anvil evolution, driving mass transfer from small to large ice crystals. The wave‐driven decrease in ice concentration is much faster for typical anvil cirrus detrained at ≃11.5–12.5 km than for less frequent anvils at 15.5–17.5 km because of the strong temperature dependence of deposition growth and sublimation rates. The simulations also show that waves, along with the Kelvin effect, drive growth of mid‐sized (5–20 μm) ice crystals, which is consistent with the observed transition to bullet rosette habits in aging anvil cirrus. We conclude that high‐frequency gravity waves, which are generally not resolved in large‐scale models, likely have important impacts on anvil cirrus microphysical properties and lifetimes.

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.

Evaluation of Ice Recrystallization Inhibition of Ice-Binding Proteins by Monitoring Specific Ice Crystals.

Ice recrystallization is a phenomenon in which large ice crystals are formed at the expense of smaller ones. The resultant large ice crystals degrade the quality of frozen foods and cryopreserved biomaterials. To minimize freeze damage by controlling the ice recrystallization process, various compounds have been developed, including biological antifreezes, synthetic peptides, glycopeptides, polymers, and small molecules. To compare their efficiency, evaluation methods of ice recrystallization inhibition are important. This chapter describes a practical protocol to quantify the inhibition efficiency by observing specific ice crystals exhibiting uniform growth.

Hemp protein hydrolysates’ ability to inhibit ice recrystallization is influenced by the dispersing medium and succinylation

Freezing damage to foods can occur due to the formation of large ice crystals in the microstructure of foods, leading to unfavorable changes in the quality. The objective of this study was to determine the ice recrystallization inhibition (IRI) activity of hemp protein isolate (HPI) as affected by enzymatic hydrolysis and modification by succinylation. The IRI activity was evaluated using splat assay in phosphate buffer saline (PBS) and 10 mM NaCl. Enzymatic hydrolysis did not result in the production of IRI active hydrolysates when evaluated in PBS. Succinylation at 0.25:1 molar ratio of bromelain and trypsin hydrolysates resulted in the most IRI active hemp protein hydrolysates in PBS, having a 49% and 46% increase in IRI activity. When evaluated at 10 mM NaCl, both unmodified and modified HPI hydrolysates are IRI active. The unmodified hydrolysates were all significantly more IRI active in 10 mM NaCl, the hydrolysate produced by bromelain hydrolysis for 60 min had increased activity by 42% in the medium compared to PBS. Our results show that the ability of HPI hydrolysates to inhibit growth of ice crystal is influenced by the dispersing medium used during splat assay and succinylation.

Effect of supercooling phenomenon on liquid freezing in cylindrical vessel

AbstractFreezing has been used to extend the shelf life of food products. In freezing, the large ice crystals which are unfavorable for the texture and quality of food are mainly generated during a solid–liquid coexistence phase. It is well known the ice crystals produced after undergoing a supercooling state were finer than those produced without supercooling. This implies that the supercooling phenomenon affects the solid–liquid coexistence time during freezing. Therefore, in this study, the effect of the supercooling phenomenon on the solid–liquid coexistence time was investigated using a cylindrical vessel. The experimental results indicated that the solid–liquid coexistence time decreased with increasing degrees of supercooling. This result suggests that increasing the degree of supercooling is effective for producing finer ice crystals. Generally, the temperature distribution is uniform to promote the supercooled state. Thus, rotational motion of the vessel with a periodical switching the rotational direction every 180° clockwise and counter‐clockwise was imposed to relax the temperature distribution in the vessel. Below a certain rotational speed, it was observed that supercooling deepened; above that, multiple instances of supercooling release were observed owing to the inversion.

Cryoprotective role of saccharides in frozen egg yolks: Water/ice tailoring effect and improved freeze–thaw stability

Freeze-induced instability of food products causes substantial losses to food manufacturers annually, and the inhibition of freeze damage is conducive to the development of frozen food industries. However, we lack sufficient information on using saccharides as cryoprotectants in frozen egg yolk systems to inhibit gelation. Therefore, we investigated the cryoprotective effects of several saccharides (sucrose, L-arabinose, xylitol, trehalose, D-cellobiose, and xylooligosaccharides) on frozen egg yolks, focusing on the water/ice tailoring effect of saccharides and the freeze–thaw stability of egg yolks. To evaluate the water/ice tailoring effects, we investigated the total water content, water activity, water state, and water distribution of egg yolks before and after freeze–thawing. We investigated the physical and structural changes in egg yolks before and after freeze–thawing to evaluate their stability. We observed that saccharides exhibited the ability to mitigate texture hardening, whitening in color, disorder in crystallinity, aggregation, and damage in protein integrity of frozen-thawed egg yolks by decreasing the freezable water content, bulk water content, and large ice crystal formation. L-arabinose was found most effective in regulating the freeze‒thaw-induced egg yolk instability, followed by xylitol. Their exceptional gelation-regulating capability and low-calorie nature render them highly suitable additives for the cryopreservation of frozen egg yolks.

Quality characteristics of milk ice cream with citrus fibers and gum

Currently at least 4 food additives — emulsifiers and hydrocolloids — are used for ice cream production to stabilize its structure. However adding these substances reduces the demand for this product among healthy lifestyle adepts. The aim of the research was to define the possibility of using citrus fibers and their compositions together with guar and xanthan gums to stabilize the milk ice cream structure. Samples with gelatin and a complex stabilizer (emulsifier) were used as control samples. It was established that adding of citrus fibers in amount of 0.6% makes the product bitter, does not provide the required level of dynamic viscosity of the mixture, it forms an unstable air phase and large ice crystals. The combination of dietary fibers with gums had a positive effect on these quality characteristics. The highest dispersion of ice crystals (average size accounted for 36–39 μm) and dynamic viscosity of the mixture, comparable with the quality characteristics of the sample with a complex stabilizeremulsifier, was achieved in the sample with added fibers and xanthan gum. The sample with dietary citrus fiber and guar gum showed better characteristics in terms of heat resistance in comparison with the samples with fiber only, as well as samples with plain fiber and guar gum. After 60 min of thermostating, the mass fraction of melt was equal to 7%, which is 2.8 and 2 times less than in samples without gums and with xanthan gum. The correlation was found between the parameter “hardness” and the parameter “thermal stability”: the hardest samples showed the highest resistance to melting. Based on the results of the research, the expediency of using combinations of citrus fibers and guar gum or xanthan gum in the production of ice cream with a limited number of food additives was established. Meanwhile it is necessary to take into account the state of structural elements during the product storage, and using the packaging that helps preserve the shape of the ice cream portion.

Stability Analysis of Ice Crystal Orientation

Abstract The stability of ice crystal orientation is studied by modeling the airflow around ice crystals at moderate Reynolds number, where an ice crystal is approximated by a cylinder with three parameters: diameter D, length L, and zenith angle of the axis θ. In this paper, the torque acting on ice crystals is simulated at different θ first, and then a special θ with zero horizontal torque, denoted as θe, is sought as an equilibrium of ice crystal orientation. The equilibrium is classified into two kinds: stable and unstable. Ice crystals rotate to θe of stable equilibriums while deviating from θe of unstable ones once they are released into quiet air. Multiple equilibriums of ice crystal orientation are found via numerical simulations. A cylinder with D/L close to one has three equilibriums, two of which are stable (i.e., θe = 0° and 90°). A cylinder with D/L away from one has only two equilibriums, one of which is stable (i.e., either θe = 0° or 90°). In addition, an asymmetric cylinder has two, three, or five equilibriums, and their θe is sensitive to the distance between its geometrical center and its center of gravity. The sensitivity of θe to crystal asymmetry suggests large symmetric ice crystals tend to become asymmetric (or irregular) and subsequently oriented randomly. Significance Statement Ice crystal orientation impacts high-cloud reflectance and satellite-based observations of high clouds significantly. However, its laboratory and field observations look dissimilar: the percentage of horizontally oriented ice crystals (HOICs) observed in the laboratory is quite high, while in the field it is often low and varies greatly in space and time. The motivation for this study is to elucidate what causes the difference between the laboratory and field observations. The torque acting on ice crystals are computed by modeling the airflow around ice crystals, revealing the conditions for nonhorizontal orientations of ice crystals. In quiet air, an ice crystal is oriented either horizontally or vertically when its shape is close to sphere. When its shape is elongated in one direction, its orientation depends on its asymmetry in density and shape. The sensitivity of ice crystal orientation to ice crystal asymmetry explains the low percentage of HOICs in the field, because asymmetric ice crystals are common in clouds. As an application, this sensitivity together with the observed percentage of HOICs can be used to infer the processes of ice crystal growth in clouds, providing clues to better representation of ice crystals in weather and climate models.

Simulations of Halos Produced by Carbon Dioxide Ice Crystals in the Martian Atmosphere

AbstractIt has been known for decades that carbon dioxide (CO2) ice clouds exist in the Martian atmosphere. According to remote sensing observations and previous modeling studies, the Martian CO2 ice crystals may be sufficiently large to generate halos. However, observations of CO2 ice crystal halos have not been reported so far. This study simulates the scattering and polarized phase functions at a wavelength of 0.48 μm based on state‐of‐the‐art light‐scattering computational capabilities. The specific CO2 ice crystal habits considered in the simulations include cubes, octahedrons, cubo‐octahedrons, and truncated octahedrons of various sizes. The halos produced by CO2 ice crystals peak at approximately 29° and 42°. Moreover, large CO2 ice crystals may cause strong scattering peaks at 155° and 180°. An ensemble of water (H2O) ice crystals and CO2 ice crystals with appropriate mixing fractions might be responsible for a halo occurrence recently observed on Mars.

Modulation of ice crystal formation behavior in pectin-sucrose hydrogel by freezing temperature: Effect on ice crystal morphology and drying properties

A model solid food system was designed to investigate the effects of freezing temperature on freezing rate, ice crystal morphology, physical properties, and drying characteristics of freeze-dried pectin cryogels. The results indicated that the fractal dimension of ice crystals was significantly reduced in gels while the mean diameter and the diameter range tended to increase as the freezing rate accelerated. The drying time is positively correlated with the fractal dimension and negatively correlated with the proportion and the mean diameter of the ice crystal. Slow freezing (at 20 °C) produced large ice crystals (0.3 mm) with a low fractal dimension (1.662), resulting in a short drying time (9.46 h) and low hardness (max positive force and positive area were 436.69 g and 717.79 g mm, respectively). This study provides reference data that could help increase freeze-drying efficiency and improve the texture quality of food products.

Ocean turbulent boundary-layer influence on ice crystal behaviour beneath fast ice in an Antarctic ice shelf water plume: The “dirty ice”

The oceanic connection between ice shelf cavities and sea ice influences sea ice development and persistence. One unique feature in regions near ice shelves is the potential for sea ice growth due to crystal accretion on its underside. Here we present observations of ocean boundary-layer processes and ice crystal behaviour in an Ice Shelf Water outflow region from the Ross/McMurdo Ice Shelves. From a fast ice field camp during the Spring of 2015, we captured the kinematics of free-floating relatively large (in some cases 10s of mm in scale) ice crystals that were advecting and then settling upwards in a depositional layer on the sea ice underside (SIPL, sub-ice platelet layer). Simultaneously, we measured the background oceanic temperature, salinity, currents and turbulence structure. At the camp location the total water depth was 536 m, with the uppermost 50 m of the water column being in-situ super-cooled. Tidal flow speeds had an amplitude of around 0.1 m s-1 with dissipation rates in the under-ice boundary layer measured to be up to ε=10-6 W kg-1. Acoustic sampling (200 kHz) identified backscatter from large, individually identifiable suspended crystals associated with crystal sizes larger than normally described as frazil. Measurement of crystals in the SIPL found dimensions of the range 5-200 mm with an average of 93-101 mm depending on the year. The existence and settlement of crystals has implications for understanding SIPL evolution, the structure of sea ice, as well as the fate of Ice Shelf Water.

Freeze-Drying of Pharmaceuticals in Vials Nested in a Rack System—Part I: Freezing Behaviour

The distribution of biopharmaceuticals often requires either ultra-cold conditions or lyophilisation. In both cases, the drug product is frozen and, thus, exposed to similar stress conditions, which can be detrimental to its quality. However, these stresses can be inhibited or mitigated by a suitable formulation and/or an appropriate freezing design. This paper addresses how the key freezing parameters, i.e., ice nucleation temperature and cooling rate, impact the freezing behaviour of a sucrose-based formulation. The analysis included two loading configurations, vials directly resting on the shelf and nested in a rack system. The loading configuration affected the product freezing rate and the ice nucleation temperature distribution, resulting in larger ice crystals in the case of vials nested in a rack system. SEM micrographs and specific surface area measurements confirmed the different product morphology. Eventually, the different product morphology impacted the bioactivity recovery of lactate dehydrogenase.

Depletion interaction may reduce ice recrystallization inhibition activity of cellulose nanocrystals (CNCs) at high concentrations

In ice cream, food hydrocolloids are commonly used as stabilizers for controlling ice recrystallization. Recent studies suggest that some stabilizers might bind to ice crystal surfaces and inhibit recrystallization. However, this ice-binding mechanism is challenged by the fact that stabilizers at high concentrations sometimes have reduced activity or even accelerate ice recrystallization. In this work, we determined the ice recrystallization inhibition (IRI) activity of cellulose nanocrystals (CNCs) at different concentrations in the 3.0% sucrose solution by the splat assay and in the 25.0% and 40.0% sucrose solutions by the sandwich assay. Reduced activity at high CNCs concentrations was observed in the sandwich assay. It was not linked to the phase separation or liquid crystal phase formation of CNCs but was caused by the accretion of nearby ice crystals and the forming of large ice crystals with irregular morphology and high aspect ratios. A new explanation based on the depletion-interaction-induced accretion of ice crystals was proposed. Our findings might resolve the contradiction between the ice-binding mechanism and the stabilizer concentration effect and add more support to the interfacial mechanism of ice recrystallization inhibition. They also pointed out the importance of selecting suitable stabilizer concentrations for screening IRI active materials and manufacturing frozen desserts.

Microstructural analysis of frozen and salted fish and seafood meat

To evaluate the quality and safety of fish and seafood meat, along with generally accepted methods, new histological research methods are used, which allow establishing microscopic changes in fresh, spoiled, and canned foods. The purpose of this study is to examine the microscopic structure of salted fish meat (Herring, Pollock) and seafood (squid, mussels) by freezing. It was confirmed that fish meat is composed of skeletal muscle, fibrous connective (endo- , perimysium) tissues with blood, lymphatic vessels, and nerves. Muscle tissue fibres have the appearance of cylindrical formations, with well-defined transverse striation and numerous nuclei. The basis of seafood meat is smooth muscle tissue with layers of loose fibrous connective tissue, blood vessels, and nerve fibres. Smooth muscle cells are fusiform in shape, without transverse striation and with a single nucleus. During freezing of fish meat at a temperature of -18ºС, ice crystals are small and well-defined in the endo- and perimysium, and at a temperature of -23ºС – in muscle fibres. When fish is re-frozen, large ice crystals form in both the muscle fibres and the endomysium and perimysium of the muscles, the muscle fibres are fragmented and have cracks. In frozen seafood meat, there is a deformation of bundles of smooth muscle cells and their fragmentation. During the salting of fish meat, in the dehydration phase, a decrease in the diameter of muscle fibres and the width of the endo- and perimysium is noted, the transverse striation and nuclei of muscle fibres are well expressed, and in the dehydration phase, the reverse processes occur. Meanwhile, the fibres become straight with cracks and crevices, and graininess is noticeable in the endomysium and perimysium. Based on the results obtained, it is possible to evaluate the microstructure of frozen and salted fish and seafood meat, which is important when monitoring the suitability of food products for consumers

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.

Исследования льдообразующих свойств кластеров из нанотрубок оксида цинка

Introduction. In recent years, the volume of funds used in the practice of weather modification has been growing in the world. Silver, the main component of weather modification funds, is a rather expensive metal. Therefore, the issue of reducing the silver content in the formulations of pyrotechnic compositions or the use of other effective ice-forming agents is relevant. Zinc oxide, like silver iodide, has ice-forming properties. When zinc is sublimated in water vapor, clusters of nanotubes of various sizes are formed. In this regard, experimental studies of the mechanism of ice formation on clusters of zinc oxide nanotubes seem to be an urgent task. The results of these studies are presented in this article. Materials and research methods. During thermal sublimation of reagents nanoscale particles are formed. These particles combine into clusters. The shape and size of these clusters, as well as their ice-forming properties, depend on the thermodynamic state of the medium in which they are formed. Tests of the ice-forming efficiency of such reagents should be carried out in conditions in clouds. This article presents the results of laboratory modeling of the formation of ice crystals during the interaction of zinc oxide clusters consisting of nanotubes, and the results of their comparison with the pyrotechnic composition AD–1 used in practice of weather modification, which is used in anti-hail products of the type «Alazan–6» and «Alazan–9» [1]. Research results and their discussion. The article presents the equipment and methods of performing experiments to study the ice-forming properties of clusters of zinc oxide nanotubes obtained in a cloud chamber during zinc sublimation in the presence of water vapor. The experiments were carried out on laboratory installations in the temperature range from –3 to –14 °C. The effectiveness of a reagent based on clusters of zinc oxide nanotubes has been investigated and compared with the effectiveness of the pyrotechnic composition of AD–1. The research results are presented in Tables 1–6 and Figures 2–7. Conclusions. In the course of laboratory experiments, a method for studying the ice-forming properties of clusters of zinc oxide nanotubes has been developed. When the pyrotechnic composition of AD–1 is sublimated, particles with a diameter from 20 nm to 400 nm with a modal value of 70 nm are formed. Zinc oxide clusters have a porous, loose structure, low density and larger sizes, almost two orders of magnitude larger than the sizes of silver iodide particles. Large ice crystals are formed on them. The total area of crystals formed on clusters of zinc oxide nanotubes is an order of magnitude larger than the total area of crystals formed on particles of the pyrotechnic composition AD–1. The reagent consisting of zinc oxide clusters is comparable in ice-forming characteristics to the pyrotechnic composition of AD–1 and can be recommended for practical use.

Intensification of water extraction of non-fruit parts of sea buckthorn (Hippóphaë rhamnóides)

The healing properties of extracts from sea buckthorn fruits have been confirmed by numerous studies, however, the infertile parts remaining after harvesting or after pruning young trees also contain valuable components. Leaves, bark, shoots and woody parts of sea buckthorn are very promising raw materials for the extraction of biologically active substances. The introduction of non-waste technologies, issues of resource conservation, the search for rational ways to isolate valuable components from the non-fruit part of sea buckthorn determined the relevance of this study. The choice of the optimal method for the extraction of non-fruit parts of sea buckthorn is aimed at accelerating heat and mass transfer processes and increasing the rate of diffusion extraction of biologically active substances. The paper reflects the results of experimental studies of traditional aqueous extraction of non-fruit parts of sea buckthorn, namely leaves, bark, shoots and wood, and the results of intensification of extraction by preliminary freezing of the feedstock. The influence of the raw material freezing rate on the size of the formed ice crystals is analyzed. It has been established that at a freezing rate of 0.1-1 cm/ h, large ice crystals form in the intercellular space of plant raw materials, causing mechanical damage to cellular structures and contributing to better leaching of biologically active substances, which is confirmed by experimental studies.

Growth Mechanism of Ice Crystals with Five‐Fold Symmetry by the Phase‐Field Method

In order to simulate the ice crystal growth with five‐fold symmetry, a new phase‐field model was established. The finite difference method was used to solve the governing equation, reproduce the growth morphology of ice crystals with five‐fold symmetry, and study the influence of interfacial energy anisotropy and undercooling on the growth mechanism of ice crystals. The results indicate that when the strength of interfacial energy anisotropy (ε5) is greater than the critical value (1/24), the interface discontinuity and corners form at the tips of the main stem and side branches. The characteristic parameters of the ice crystal tip in the horizontal direction have an extreme value at ε5 equal to 0.1. With an increase in undercooling, the main branch becomes slender and side branches appear, which is consistent with the mechanism of crystal continuous growth. When undercooling reaches 0.4, ice crystal growth changes from diffusion control to dynamic control. Therefore, by selecting the quick freezing conditions, undercooling is controlled at around 0.4 and the interfacial energy anisotropy at around 0.1, and the tip radius of curvature is minimized so as to prevent large ice crystals from damaging the cell wall and leading to the decline in the quality of quick‐frozen food. The findings of this study can help us have a better understanding of ice crystal growth in the process of quick‐frozen food preservation.