Ice Morphology: Fundamentals and Technological Applications in Foods

A comprehensive investigation of the use of freeze concentration appro aches for the concentration of fish protein hydrolysates

Fish protein hydrolysates (FPH) are inherently unstable in their liquid form, necessitating either freezing or dewatering for stabilization. Gentle methods such as freeze concentration can be used to remove water, this can be achieved by freezing water in solution by decreasing the bulk temperature below freezing point and separating pure ice crystals from concentrated solution. This approach serves as an alternative to techniques like evaporation and reverse osmosis for concentrating solutions that have high water content, significant nutritional value, and thermolabile compounds. This is crucial as many bioactive compounds degrade when exposed to elevated temperatures. Another notable advantage of this technology is its potential to reduce energy consumption by up to 40% when integrated into the FPH drying process. Although this technology is currently industrialized primarily for juices, it can achieve concentrations of up to 60°Brix and manage viscosities up to 400 mPa.s. Numerous studies have been dedicated to enhancing design and processes, leading to a 35% reduction in the system's capital cost and a 20% reduction in energy consumption. Moreover, freeze concentration can synergize with other concentration techniques, creating more efficient hybrid processes. This review aims to introduce freeze concentration as a superior option for preserving fish protein hydrolysates, enhancing their stability, and maintaining their nutritional and bioactive qualities.

Effects of ultrasonic pretreatment on drying characteristics and water migration characteristics of freeze-dried strawberry

The effects of ultrasonic pretreatment on the drying characteristics and microstructure of strawberry slices were investigated. The rehydration characteristics of freeze-dried products, which were pre-frozen at -20 °C and - 80 °C were explored, with a focus on water mobility and distribution. The ultrasonic pretreatment significantly increased the water mobility of the strawberry slices, resulting in a reduction in their water content. However, the application of ultrasound significantly decreased the rehydration speed, indicating a lower moisture absorption capacity in the pretreated sample. The micrographs revealed that the structure of the tissue was more uniform after ultrasonic treatment, and water loss was accelerated. In addition, the contact angle measurements showed that the samples were more hydrophobic after ultrasonic treatment, and the eutectic temperature and fold point of the samples increased. Therefore, this study found that ultrasonic-assisted freeze vacuum drying technology effectively reduces hygroscopicity, improves product storage, and represents a potential method for dried production.

Effect and mechanism of freezing on the quality and structure of soymilk gel induced by different salt ions

BACKGROUND

The increasing attention toward frozen soy-based foods has sparked interest. Variations exist in the quality and structure of soymilk gels induced by different salt ions, leading to diverse changes post-freezing. This study compared and analyzed the effects of calcium chloride (CC), magnesium chloride (MC) and calcium sulfate (CS) on the quality characteristics and protein structure changes of soymilk gels (CC-S, MC-S and CS-S) before and after freezing, and clarified the mechanisms of freezing on soymilk gel.

RESULTS

The formation rate of soymilk gel is influenced by the type of salt ions. In comparison to CS and MC, soymilk gel induced by CC exhibited the fastest formation rate, highest gel hardness, lowest moisture content, and smaller gel pores. However, freezing treatment deteriorated the quality of soymilk gel induced by different salt ions, leading to a decline in textural properties (hardness and chewiness). Among these, the textual state of CC-induced soymilk gel remained optimal, exhibiting the least apparent damage and minimal cooking loss. Freezing treatments prompt a transition of soymilk gel secondary structure from β-turns to β-sheets, disrupting the protein's tertiary structure. Furthermore, freezing treatments also fostered the crosslinking between soymilk gel protein, increasing the content of disulfide bonds.

CONCLUSION

The quality of frozen soymilk gel is influenced by the rate of gel formation induced by salt ions. After freezing, soymilk gel with faster gelation rates exhibited a greater tendency for the transformation of protein-water interactions into protein-protein interactions. They showed a higher degree of disulfide bond formation, resulting in a more tightly knit and firm frozen gel network structure with denser and more uniformly distributed pores. © 2024 Society of Chemical Industry.

Cryoprotective role of vacuum infused inulin on the quality of artichoke: Interactive effects of freezing, thawing and storage period

Freezing of artichoke is a promising alternative to storing it in brine and canning. The perishable vegetable was vacuum infused with inulin to improve freezing tolerance. Artichokes with and without inulin were frozen by static, air blast and individual quick freezing (IQF) methods and thawed by microwave, 25 °C and 4 °C temperature levels at each month of 6-months storage. Process conditions were evaluated by multivariate analysis of variance (MANOVA) and were found significant on the quality parameters. Inulin infusion better conserved the aw, color, texture, ascorbic acid and overall integrity of artichokes during frozen storage. Inulin incorporation and IQF showed mutual positive effect on drip loss. Polyphenol oxidase (PPO) activity values fitted to 2nd order kinetic and the highest residuals were determined in static freezing. PPO showed alleviating effect on total phenolic content. Vacuum impregnation caused a color difference prior to freezing, but was found effective for maintaining color during storage. As a result, the use of quick freezing techniques together with the addition of cryoprotectant was effective in the preservation of artichoke quality attributes during frozen storage.

Effects of freezing and drying programs on IgY aggregation and activity during microwave freeze-drying: Protective effects and interactions of trehalose and mannitol

The acquisition of high quality lyophilized IgY products, characterized by an aesthetically pleasing visage, heightened stability, and a marked preservation of activity, constitutes an indispensable pursuit in augmenting the safety and pragmatic utility of IgY. Within this context, an exploration was undertaken to investigate an innovative modality encompassing microwave freeze-drying (MFD) as a preparatory methodology of IgY. Morphological assessments revealed that both cryogenic freezing and subsequent MFD procedures resulted in aggregation of IgY, with the deleterious influence posed by the MFD phase transcending that of the freezing phase. The composite protective agent comprised of trehalose and mannitol engendered a safeguarding effect on the structural integrity of IgY, thereby attenuating reducing aggregation between IgY during the freeze-drying process. Enzyme-linked immunosorbent assay (ELISA) outcomes demonstrated a discernible correlation between IgY aggregation and a notable reduction in its binding affinity towards the pertinent antigen. Comparative analysis vis-à-vis the control sample delineated that when the trehalose-to-mannitol ratio was upheld at 1:3, a two-fold outcome was achieved: a mitigation of the collapse susceptibility within the final product as well as a deterrence of IgY agglomeration, concomitant with an elevated preservation rate of active antibodies (78.57 %).

Ice Recrystallization Unveils the Binding Mechanism Operating at a Diffused Interface

Recrystallization of ice is a natural phenomenon that causes adverse effects in cryopreservation, agriculture, and in frozen food industry. It has long been recognized that ice recrystallization occurs through the Ostwald ripening and accretion processes. However, neither of these processes has been explored in microscopic detail by state-of-the-art experimental techniques. We carried out atomistic molecular dynamics (MD) simulations to explore ice recrystallization through the accretion process. Attempts have been made to elucidate the binding mechanism that is operating at the diffused ice-water interface. It is demonstrated that two ice crystals spontaneously recognize each other and bind together to form a large crystal in liquid water, resulting in ice recrystallization by accretion. Interestingly, the study reveals that the binding occurs due to the freezing of the interfacial water layer present between the two ice planes, even at a temperature above the melting point of the ice crystal. The synergistically enhanced ordering effect of two ice surfaces on the interfacial water leads to such freezing occurring during the binding process. However, proper crystallographic alignment is not necessarily required for the binding of the two crystals. Simulations have also been carried out to study the binding between an ice crystal and the model ice-binding surface (IBS) of an antifreeze protein above the melting point of the ice crystal. It is found that such binding at the IBS is accompanied by freezing of the interfacial water. This establishes that the synergetic ordering-driven freezing of interfacial water is a common binding mechanism at the diffused surfaces of ice crystals. We believe that this mechanism will provide a microscopic understanding of the process of recrystallization inhibition and thus help in designing suitable materials for potent applications in recrystallization inhibition.

Advances in single ice crystal shaping materials: From nature to synthesis and applications in cryopreservation

Antifreeze (glyco) proteins [AF(G)Ps], which are widely present in various extreme microorganisms, can control the formation and growth of ice crystals. Given the significance of cryogenic technology in biomedicine, climate science, electronic energy, and other fields of research, scientists are quite interested in the development and synthesis high-efficiency bionic antifreeze protein materials, particularly to reproduce their dynamic ice shaping (DIS) characteristics. Single ice crystal shaping materials, a promising class of ice-controlling materials, can alter the morphology and growth rate of ice crystals at low temperatures. This review aims to highlight the development of single ice crystal shaping materials and provide a brief comparison between a series of natural and bionic synthetic materials with DIS ability, which include AF(G)Ps, polymers, salts, and nanomaterials. Additionally, we summarize their applications in cryopreservation. Finally, this paper presents the current challenges and prospects encountered in developing high-efficiency and practical single ice crystal shaping materials. STATEMENT OF SIGNIFICANCE: The formation and growth of ice crystals hold a significant importance to an incredibly broad range of fields. Therefore, the design and fabrication of the single ice crystal shaping materials have gained the increasing popularity due to its key role in dynamic ice shaping (DIS) characteristics. Especially, single ice crystal shaping materials are considered one of the most promising candidates as ice inhibitors, presenting tremendous prospects for enhancing cryopreservation. In this work, we focus on the molecular characteristics, structure-function relationships, and DIS mechanisms of typical natural and biomimetic synthetic materials. This review may provide inspiration for the design and preparation of single ice crystal shaping materials and give guidance for the development of effective cryopreservation agent.

Ice crystallization and structural changes in cheese during freezing and frozen storage: implications for functional properties

Temperature-mediated preservation techniques offer a simple, scalable, effective, and fairly efficient method of long-term storage of food products. In order to ensure the uninterrupted availability of cheese across the globe, a critical understanding of its techno-functional properties as affected by freezing and frozen storage is essential. Detailed studies of temperature-mediated molecular dynamics are available for relatively simpler and homogeneous systems like pure water, proteins, and carbohydrates. However, for heterogeneous systems like cheese, inter-component interactions at sub-zero temperatures have not been extensively covered. Ice crystallization during freezing causes dehydration of caseins and the formation of concentration gradients within the cheese matrix, causing undesirable changes in texture-functional attributes, but findings vary due to experimental conditions. A suitable combination of sample size, freezing rate, aging, and tempering can extend the shelf life of high- and low-moisture Mozzarella cheese. However, limited studies on other cheeses suggest that effects and suitability differ by cheese type, in most cases adversely affecting texture and functional attributes. This review presents an overview of the understanding of the effects of refrigeration, freezing techniques, and frozen storage on structural components of cheese, most prominently Mozzarella cheese, and the corresponding impact on microstructure and functionality. Also included are the mechanism of ice formation and relevant mathematical models for estimation of the thermophysical properties of cheese to assist in designing optimized schemes for their frozen storage. The review also highlights the lack of unanimity in critical understanding concerning the effect of freezing on the long-term storage of Mozzarella cheese with respect to its functionality.

Bioactive compounds recovery by freeze concentration process from winemaking by-product

Grape pomace is the main solid residue of wine industry, containing high amounts of phenolic compounds. Considering its high potential, an extraction procedure was optimized for maximal recovery of anthocyanins from grape pomace (Vitis vinifera L.) using citric acid as a generally recognized as safe (GRAS) acidulant in water. Volume of solvent (3.2-36.8 mL), time (14.4-165.6 min) and pH of solvent (1.12-4.48) were the studied variables. Furthermore, the best condition to obtain extract rich in anthocyanins was submitted to the gravitational block freeze concentration process. The performance of the process was evaluated and cryoconcentrated and ice fractions were analyzed for physicochemical properties, bioactive compounds content, and antioxidant activity. Interaction, linear, and quadratic effects for volume and pH of solvent were significant by analysis of variance (ANOVA). The experimental design allowed the prediction for maximal recovery of anthocyanins (10 mL of solvent at pH 1.8). The bioactive composition of the optimized grape pomace extract was influenced by the cryoconcentration process. After three cycles using gravitational block freeze concentration, the total phenolics and monomeric anthocyanins were approximately 4 and 5 times higher than the initial condition of the extract, respectively. Consequently, an increase in antioxidant activity was observed. The increase in the concentration of bioactive compounds reached a process efficiency of 93% (stage 1) for phenolic compounds and 91% (stage 2) for anthocyanins. Therefore, the final water-based optimized method is safe and has a low cost and the concentrated extract certainly showed higher concentrations of total phenolics and anthocyanins, compared to the initial extract. The proposed clean extraction method and cryoconcentration technique can be considered important strategies for recovering and valuing grape pomace components, improving the approach to the circular economy concept in the wine industry.

Observation and Measurement of Ice Morphology in Foods: A Review

Freezing is an effective technology with which to maintain food quality. However, the formation of ice crystals during this process can cause damage to the cellular structure, leading to food deterioration. A good understanding of the relationship between food microstructure and ice morphology, as well as the ability to effectively measure and control ice crystals, is very useful to achieve high-quality frozen foods. Hence, a brief discussion is presented on the fundamentals/principles of optical microscopic techniques (light microscopy), electronic microscopic techniques (transmission electron microscopy (TEM) and scanning electron microscopy (SEM)), as well as other non-invasive techniques (X-rays, spectroscopy, and magnetic resonance) and their application to measuring ice formation rates and characterizing ice crystals, providing insight into the freezing mechanisms as well as direct monitoring of the entire process. And, in addition, this review compares (the negative and positive aspects of) the use of simple and cheap but destructive technologies (optical microscopy) with detailed microscopic technologies at the micro/nanometer scale but with pretreatments that alter the original sample (SEM and TEM), and non-destructive technologies that do not require sample preparation but which have high acquisition and operational costs. Also included are images and examples which demonstrate how useful an analysis using these techniques can be.

Impact of Processing and Preservation Methods and Storage on Total Phenolics, Flavonoids, and Antioxidant Activities of Okra (Abelmoschus esculentus L.)

Very few studies have thus far evaluated the impact of various processing and preservation techniques (blanching, frying, freezing, dehydration, and sun drying) on the levels of total phenolics, flavonoids, and antioxidant activities of okra. The primary objective of this study was to evaluate the effects of different processing and preservation methods on the levels of phenolics, flavonoids, and antioxidant activities of okra. The ethanolic extracts of each sample were analyzed before and after preservation and storage for a period of three months. The results showed a significant improvement (p < 0.05) in total phenolic content (134.1 mg GAE/100g) and DPPH (1-1-diphenyl1-2-pricrylhydrazyl) scavenging activity (IC50 value of 3.0 mg/mL) in blanched okra when compared to fresh okra (86.35 mg GAE/100g and IC50 value of 3.8 mg/mL, respectively). Fresh okra exhibited the highest flavonoid content (105.75 mg QE/100g), while sun-dried okra samples stored for three months exhibited a decrease in total phenolic content (14.45 mg GAE/100g), total flavonoid contents (13.25 mg QE/100g), reducing power activity (23.30%), and DPPH scavenging activity (IC50 value of 134.8 mg/mL). The DPPH inhibition activities of all okra treatments showed a significant and positive correlation with the okra phenolic and flavonoid content (r = 0.702 and 0.67, respectively). The reducing power activity (%) of okra treatments exhibited a strong correlation (r) with phenolic contents (r = 0.966), and the correlation with flavonoid contents was 0.459. Generally, different processing and preservation methods of okra revealed that the impact on total phenolic and flavonoid contents, as well as antioxidant activities, was slightly significant among samples preserved using the same method during storage. In addition, blanched and frozen okra resulted in the highest retention of phenolic contents and antioxidant activities.

Study on the ice crystals growth under pectin gels with different crosslinking strengths by modulating the degree of amidation in HG domain

The ice crystal morphology formed under a series of amidated pectin gels with various crosslink strengths were investigated. The results showed that as the degree of amidation (DA) increased, pectin chains exhibited shorter homogalacturonan (HG) regions. Highly amidated pectin exhibited a faster gelation rate and a stronger gel micro-network via hydrogen bonds. Based on cryogenic scanning electron microscopy (cryo-SEM), smaller ice crystals were formed in frozen gel with low DA, suggesting that a weaker cross-linked gel micro-network was more effective at inhibiting crystallization. After sublimation, lyophilized gel scaffolds with high crosslink strength displayed less number of pores, high porosity, lower specific surface area, and greater mechanical strength. This study is expected to confirm that the microstructure and mechanical properties of freeze-dried pectin porous materials could be regulated by changing the crosslink strength of pectin chains, which is achieved by increasing the degree of amidation in the HG domains.

Food physics insight: the structural design of foods

Understanding food materials from the classical realm of physics including soft condensed matter physics has been an area of interest especially in the structural design engineering of food products. The contents of this review would help the reader in understanding the thermodynamics of food polymer, structural design principles, structural hierarchy, steps involved in food structuring, newer structural design technologies, and structure measurement techniques. Understanding the concepts of free volume would help the food engineers and technologists to study the food structural changes, manipulate process parameters and, the optimum amount of nutraceuticals/ingredients to be loaded in the food matrix. Such understanding helps in reducing food ingredient wastage while designing a food product.

Spatiotemporal Control of Ice Crystallization in Supercooled Water via an Ultrashort Laser Impulse

Focused irradiation with ultrashort laser pulses realized the fine spatiotemporal control of ice crystallization in supercooled water. An effective multiphoton excitation at the laser focus generated shockwaves and bubbles, which acted as an impulse for inducing ice crystal nucleation. The impulse that was localized close to the laser focus and accompanied by a small temperature elevation allowed the precise position control of ice crystallization and its observation with spatiotemporal resolution of micrometers and microseconds using a microscope. To verify the versatility of this laser method, we also applied it using various aqueous systems (e.g., plant extracts). The systematic study of crystallization probability revealed that laser-induced cavitation bubbles play a crucial role in inducing ice crystal nucleation. This method can be used as a tool for studying ice crystallization dynamics in various natural and biological phenomena.

Optimization of freezing methods and composition of frozen rice dough reconstituted by glutinous rice starch and gluten

This study investigated the effects of four different freezing methods on the texture of rice dough reconstituted by glutinous rice starch and gluten, and the changes of properties of rice dough with different gluten ratios after liquid nitrogen (LF) treatment. The profiles of frozen rice dough were studied by texture analyzer, low-field NMR, SEM, FT-IR, DSC, CLSM, X-RD and RVA. Results revealed that with the slowing down of freezing rate, the damage of freezing process to starch granules and protein structure in frozen rice dough increases, resulting in the increase of damaged starch, the decrease of protein ordered structure, the change of bound water in frozen rice dough to free water, the decrease of frozen rice dough hardness and elasticity, the decrease of storage modulus (G') and the deterioration of frozen rice dough texture. The addition of gluten in frozen rice dough will increase the short-range ordered structure and crystal structure of starch, reduce the digestibility of starch, and change the viscosity characteristics of frozen rice dough. Based on the experimental results, adding 10 % gluten is more suitable for making frozen rice dough, while LF has the least effect on frozen rice dough texture.

Frozen Stored Teeth: Autogenous Dentin as an Alternative Augmentation Material in Dentistry

Tooth Shell Technique (TST) with the use of autologous dentin has proven to be a suitable method of grafting in the context of lateral ridge augmentation. This present feasibility study aimed to retrospectively evaluate the preservation by lyophilization of processed dentin. Thus, the frozen stored processed dentin matrix (FST: 19 patients with 26 implants) was re-examined with that of processed teeth used immediately after extraction (IUT: 23 patients with 32 implants). Parameters of biological complications, horizontal hard tissue loss, osseointegration, and buccal lamella integrity were used for evaluation. For complications, the observation period was 5 months. Only one graft was lost (IUT group). In the area of minor complications, without the loss of an implant or augmentation, there were two cases of wound dehiscence and one case with inflammation and suppuration (IUT: n = 3, FST: n = 0). Osseointegration and integrity of the buccal lamella were present in all implants without exception. Statistically, there was no difference between the groups studied for the mean resorption of the crestal width and the buccal lamella. Results of this study show that prepared autologous dentin preserved with a conventional freezer had no disadvantage compared to immediately use autologous dentin in terms of complications and graft resorption in the context of TST.

Effects of electric and magnetic field on freezing characteristics of gel model food

The novel freezing technologies including electrostatic field assisted freezing (EF), static magnetic field assisted freezing (MF), electrostatic field combined with static magnetic field assisted freezing (EMF) were conducted on model food to facilitate comparing their application effect. The results show that the effect of EMF treatment was best, which significantly changed the freezing parameters of the sample. Compared with the control, the phase transition time and total freezing time were shortened by 17.2% and 10.5%, respectively; the proportion of the sample free water content detected by low-field nuclear magnetic resonance was significantly decreased; the gel strength and hardness were significantly improved; the protein secondary and tertiary structures were better maintained; the ice crystal area was reduced by 49.28%. Inverted fluorescence and scanning electron microscopic results indicated that the gel structure of EMF treatment samples was better than MF and EF. MF was less effective in maintaining the quality of frozen gel model.

Ice Nucleation Promotion Impact on the Ice Recrystallization Inhibition Activity of Polyols

Heterogeneous ice nucleation occurs vis-à-vis nucleating agents already present in solution yet can occur within a rather broad range of temperatures (0 to ca. -38 °C). Controlling this temperature and the subsequent growth of resulting ice crystals is crucial for the survival of biological organisms (certain insects, fish, and plants that endure subzero temperatures), as well as in the context of medical cryopreservation and food science. In these environments, uncontrolled crystal shape and size can rupture the cell membrane causing irreversible and catastrophic damage. Antifreeze (AF) proteins and synthetic AF analogs address this issue to restrict crystal growth and to shape ice crystals. Yet, if the nucleation temperature is not controlled and occurs in a lower temperature range, nascent ice crystals will have grown to a significantly larger size before the AF agents can be active on their surface to halt or slow the Ostwald ripening process during recrystallization. At a higher nucleation temperature, diffusion of AF macromolecules is enhanced, and dynamic crystal shaping can start earlier, producing smaller crystals overall. While antifreeze proteins, the inspiration for these synthetic analogs, are always applied in a salt buffer aqueous environment (most typically phosphate-buffered saline (PBS) buffer), the heterogeneous nucleation events are stochastic and occur within a wide temperature range. Silver iodide (AgI), however, is a highly effective ice nucleation promoter as its crystal lattice structure is a 98% lattice match to the basal plane of hexagonal ice (Ih) crystals acting as a template for water molecule orientation and decreasing the interfacial free energy. Here, we expose the advantage of purposely seeding such nascent ice crystals with AgI at a defined and higher temperature (-7 °C) in ultrapure water (UPW) such that nucleation can only come from AgI (and also in AgI/PBS), resulting in the most potent synthetic IRI observed to date (at concentrations as low as 0.001 mg·mL^-1).

Distribution of florfenicol and norfloxacin in ice during water freezing process: Dual effects by fluorine substituents

Distribution in ice is regarded as one of important transport modes for pollutants in seasonal freeze-up waters in cold regions. However, the distribution characteristics and mechanisms of fluorinated antibiotics as emerging contaminants during the water freezing process remain unclear. Here, florfenicol and norfloxacin were selected as model fluorinated antibiotics to investigate their ice-water distribution. Effects of antibiotic molecular structure on the distribution were explored through comparative studies with their non-fluorinated structural analogs. Results showed that phase changes during the ice growth process redistributed the antibiotics, with antibiotic concentrations in water 3.0-6.4 times higher than those in ice. The solute-rich boundary layer with a concentration gradient was presented at the ice-water interface and controlled by constitutional supercooling during the freezing process. The ice-water distribution coefficient (K_IW) values of antibiotics increased by 34.8%-38.0% with a doubling of the cooling area. The solute distribution coefficient (K_bs) values of antibiotics at -20 °C were 65.6%-70.3% higher than at -10 °C. The K_IW and K_bs values of all antibiotics were negatively correlated with their water solubilities. The fluorine substituents influenced the binding energies between antibiotics and ice, resulting in a 1.1-fold increase in the binding energy of norfloxacin on the ice surface relative to its structural analog pipemidic acid. The results provide a new insight into the transport behaviors of fluorinated pharmaceuticals in ice-water systems.

Tailoring centripetal metamaterial with superelasticity and negative Poisson's ratio for organic solvents adsorption

Graphene metamaterials with a radial-like structure and negative Poisson's ratio (NPR) were assembled using a unique centripetal freezing technique. Driven by the centripetal temperature gradient, ice crystals were grown toward the center of an aqueous graphene dispersion and form a radially arranged skeleton. A reentrant structure was formed at the diagonal of the monolith as the ice crystals sublimate. The obtained centripetal graphene metamaterial (CGM) was endowed with NPR response. CGM maintained NPR under 50% compression, which reached a minimum (-0.18) at 10% strain. After 50 compressive cycles at 50% strain, CGM retained approximately 96% of the original compressive strength. The radial channels endowed CGM with fast absorption kinetics, and the NPR response effectively accommodated the damage caused by volume shrinkage during repeated adsorption-regeneration cycles. This strategy is an effective method for achieving NPR response and improving the mechanical properties of porous materials.

Recent Advances in Freeze-Drying: Variables, Cycle Optimization, and Innovative Techniques

Freeze-drying (FD) is the most substantial drying technique utilized in the pharmaceutical and biopharmaceutical industries. It is a drying process where the solvent is crystallized at low temperatures and then sublimed from the solid-state directly into the vapor phase. Although FD possesses several merits as its suitability for thermolabile materials and its ability to produce dry products with high-quality attributes, it is a complex and prolonged process that requires optimization of both; process and formulation variables. This review attains to disassemble freeze-drying complications through a detailed explanation of the lyophilization concept, stages, the factors influencing the process including controlled ice nucleation, and the modified and innovative freeze-drying technologies proposed in recent years to overcome the shortage of traditional freeze-drying. In addition, this work points out the quality by design (QbD), critical quality of attributes (CQAs), limitations, and drawbacks of lyophilization.HighlightsLyophilization is a propitious drying technique for thermolabile materials.Optimizing the lyophilization cycle requires controlling the process parameters.The formulation excipients and the dispersion medium play crucial roles in designing a successful process.Numerous approaches were developed to ameliorate the lyophilization performance.

Influence of starch with different degrees and order of gelatinization on the microstructural and mechanical properties of pectin cryogels: A potential pore morphology regulator

The applications of cryogels are defined by their porous morphology as well as mechanical properties. To achieve efficient regulation of porous properties for pectin cryogels, we selected starch as a potential polysaccharide regulator. Pectin/starch composite cryogels with different degrees of gelatinization were formulated, and two ways of starch gelatinization were considered: starch gelatinization occurred before or after pectin crosslinking during forming the hydrogel network. The results showed that high gelatinized starch (73.8 %-100.0 %) rendered pectin cryogels with denser pore morphology and higher mechanical strength. The pore diameter transferred from 160-200 μm to 40-60 μm with the degree of gelatinization, while the total porosity decreased by about 15 % and the specific surface area increased by about 100 m²/g. When starch gelatinization occurred before pectin crosslinking, the hydrogen bond interactions between gelatinized starch and pectin were formed to accelerate the gelation rate of the pectin Ca²⁺-dependent network. When gelatinization occurred after pectin crosslinking, the pre-formed pectin network delayed the breakdown of the starch crystalline structure during gelatinization. The qualitative regulation of the pore morphology in pectin cryogels by incorporating starches with varying degrees of gelatinization was confirmed.

Analysis of Gliricidia sepium Leaves by MALDI Mass Spectrometry Imaging

When investigating the potential use of plants as a raw material for an all-natural cosmetic formulation, the main parameters are the chemical composition, antioxidant potential, antimicrobial action, and toxicity. Additionally, the production of natural cosmetics should also consider the availability of primary materials and the environmental and socioeconomic impact. Gliricidia sepium is a species that produces a large amount of plant material, being cultivated in the agroforestry system. However, studies of phytochemical composition and chemical spatial distribution are scarcely using the MALDI MS (matrix-assisted laser desorption ionization mass spectrometry) and MALDI MSI (mass spectrometry imaging) techniques. A methodology was developed to optimize ionization parameters and analysis conditions by evaluating the efficiency of three matrices: α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxybenzoic acid (DHB), and 2-mercaptobenzothiazole in MALDI MS analysis. All results were compared to ESI MS (electrospray ionization mass spectrometry), and afterward, MALDI MSI analysis was performed on the leaf surface. This study showed through phytochemical analysis that G. sepium leaves are composed of polyphenols and tannins, concluding that the methanolic extract had a higher amount of flavonoid content. Four compounds were identified on the leaf surface, and their spatial distribution was analyzed by MALDI MS using DHB as a matrix. Kaempferol, isorhamnetin, and some fatty acids showed potential applicability for cosmetical use. All the extracts presented antioxidant activity or antimicrobial action and no cytotoxicity. Therefore, extracts of G. sepium could be used as raw materials in cosmetics.

Investigation of crystal growth of CO2 hydrate in aqueous fructose solution for the potential application in carbonated solid foods

CO₂ hydrate is applicable to solid carbonated foods. The hydrate crystal morphology, which represents the crystal size and shape, is an important characteristic that changes the texture of foods. We report an observational study of the crystal growth of CO₂ hydrate in aqueous fructose solution. The difference between the phase equilibrium temperature and the experimental temperature, ΔT_sub, is applied as an index of the driving force. Experiments were performed at ΔT_sub range of 0.9 K to 5.4 K. At all ΔT_sub, initial crystal formed at the gas-solution interface and grew along the interface. After covering the interface, the crystals grew in the liquid phase The individual crystals were identified as polyhedral with facets (ΔT_sub = 0.9 K), skeletal crystals (ΔT_sub = 2.0 K) and dendrites (ΔT_sub = 3.0 K and 5.4 K). Based on these results, the potential effect of gas hydrate morphology on texture of foods has been discussed.

Aspects of Lyophilization of Cardiac Bioimplant

The use of implants of biological origin in clinical practice has led to the search for methods of long-term storage of tissues without damaging their functional and structural characteristics. Xenografts (extracted from pericardium of pigs, horses, bulls) are drawing more and more interest. The bovine pericardium is exposed to chemical and physical factors providing complete purification of tissue from cells and their components. Such scaffolds are protein (collagen) complexes that fully replicate the microstructure of the pericardial tissue. Lyophilisation ensures long-term preservation of the extracellular matrix properties. The principle of the method is in drying pre-frozen tissue, in which water is sublimated. The method is intended for storage, transportation, and the subsequent use of the bioimplant in clinical practice. However, the lyophilization process may be accompanied by various undesirable factors that can lead to denaturation of the matrix protein or loss of its functionality and structure. To preserve the natural microstructure, stabilizers or various modifications (slow/fast freezing, reducing the degree of supercooling, etc.) of the lyophilization process are applied to biological prostheses. In this review, the main processes of lyophilization of biological tissue are described, which can affect the operation of a cardiac implant. A deep understanding of the parameters of the lyophilization process is crucial for creation of stable tissue grafts and their subsequent long-term storage.

Controlled rate slow freezing with lyoprotective agent to retain the integrity of lipid nanovesicles during lyophilization

We designed a novel lyophilization method using controlled rate slow freezing (CSF) with lyoprotective agent (LPA) to achieve intact lipid nanovesicles after lyophilization. During the freezing step, LPA prevented water supercooling, and the freezing rate was controlled by CSF. Regulating the freezing rate by various liquid media was a crucial determinant of membrane disruption, and isopropanol (freezing rate of 0.933 °C/min) was the optimal medium for the CSF system. Lyophilized lipid nanovesicle using both CSF and LPA retained 92.9% of the core material and had uniform size distributions (Z-average diameter = 133.4 nm, polydispersity index = 0.144), similar to intact vesicles (120.7 nm and 0.159, respectively), after rehydration. Only lyophilized lipid nanovesicle using both CSF and LPA showed no changes in membrane fluidity and polarity. This lyophilization method can be applied to improve storage stability of lipid nanocarriers encapsulating drugs while retaining their original activity.

Design of an Ice Recrystallization-Inhibiting Polyampholyte-Containing Graft Polymer for Inhibition of Protein Aggregation

Freezing-induced damage to proteins, through osmotic stress and ice recrystallization, during protein processing and long-term storage is a serious concern and may lead to loss of protein activity owing to denaturation. In this study, graft copolymers composed of a cryoprotective polymer (capable of preventing osmotic stress) and poly(vinyl alcohol) (PVA; known for its high ice recrystallization inhibition (IRI) property) were developed. The polymers had high IRI activity, albeit slightly lower than that of PVA alone, but substantially higher than that of succinylated ε-poly-l-lysine (PLLSA) alone. The graft polymers showed an efficiency higher than that of PVA or PLLSA alone in protecting proteins from multiple freeze-thaw cycles, as well as during prolonged freezing, indicating a synergy between PVA and PLLSA. The PLLSA-based graft polymer is a promising material for use in protein biopharmaceutics for the long-term storage of proteins under freezing conditions.

Blueberry juice: Bioactive compounds, health impact, and concentration technologies-A review

Blueberries are a popular fruit with an attractive flavor and color, as well as health benefits. These health benefits have been attributed to the important number of bioactive compounds in blueberries with activities such as antioxidant, antitumor, antimutagenic, and antidiabetic effects and the prevention of cardiovascular diseases. Despite these advantages, blueberries are only obtained fresh in certain seasons; therefore, the food and beverage industry transforms them into jelly, puree, or juice. However, the concentration process could help preserve the bioactive compounds of blueberry byproducts. Concentration technologies focus on the removal of excess water to increase the product stability and reduce storage and transportation costs by causing them to take up less space or as a pretreatment before dehydration. These technologies include evaporation, reverse osmosis, and freeze concentration, and each one has different effects on the efficiency, quality, and nutritional value of the final concentrates. However, freeze concentration and reverse osmosis produce a higher-final quality concentrate than evaporation due to the use of low temperatures, which prevents the loss of thermolabile components such as bioactive compounds. Therefore, this review summarizes the impact of concentration technologies on the bioactive compounds and health benefits of blueberry juice.

Technological innovations or advancement in detecting frozen and thawed meat quality: A review

Frozen storage is one of the main storage methods for meat products. Freezing and thawing processes are important factors affecting the quality of stored foods. Deterioration of texture, denaturation of protein, decline of water holding capacity etc. are among the major quality issues during freezing that must be addressed. A number of advanced technologies are now available to detect the quality changes that can occur during freezing and/or thawing. This paper presents an overview of the techniques commonly used for the detection of meat product quality; these include: advanced microscopy, molecular sensory science and technology, nuclear magnetic resonance, hyperspectral technology, near infrared spectroscopy, Raman spectroscopy etc. These direct and indirect measurement techniques can characterize the quality of meat product from many different angles. The objective of this review is to provide an in-depth understanding of possible quality changes in meat products during freezing and thawing cycle so as to improve the quality of frozen and thawed meat products in industrial practice.

Influence of Freezing Parameters on the Formation of Internal Porous Structure and Its Impact on Freeze-Drying Kinetics

The main objective of this study was firstly to investigate the influence of freezing process parameters on the formation of the internal structure of frozen coffee granules. It was investigated how these frozen internal structures affect the drying kinetics during freeze-drying. A design of experiment study was carried out using the response surface method to quantify the influence of the freezing step that occurs in a scraped surface heat exchanger (SSHE). Therefore, the coffee extract at a concentration of 30% w/w is entering the SSHE as a liquid and gets partially crystallized up to a weight-based ice content of 0.364. During this step, the influence of factors like cooling temperature, scraper rotation speed and temperature cycles on ice crystal structure was investigated. In a second freezing step, the influence of freezing rates during hardening of the product by air-blast freezing is investigated, where the freezing rate is significantly affected by the cake thickness. The produced frozen granules were freeze-dried in single layer experiments. During drying the influence of internal structure on the drying kinetics was investigated. Results show that all factors have a significant impact on structure parameters for 30% w/w coffee solutions. A lower degree of supercooling during freezing in an SSHE, a higher number of temperature cycles (2 to 8 times) and lower freezing rates during hardening (2 °C/min to 10 °C/min) were leading to increased crystal size. This increase accelerates the primary drying rate and decreases the total drying time. A higher number of temperature cycles leads to a significant increase of crystal size and therefore larger pore size at the end of the primary drying. Furthermore, in combination with temperature cycles in the SSHE, it was found that high freezing rates during air blast freezing generally lead to a second nucleation step of ice crystals.

Rapid Depressurization Based Controlled Ice Nucleation in Pharmaceutical Freeze-drying: The Roles of the Ballast Gas and the Vial

Controlled ice nucleation offers several key benefits to the pharmaceutical lyophilization process, including reducing lyophilization cycle time, control of ice crystal morphology, and increased consistency of lyophilized product quality attributes. The rapid depressurization based controlled ice nucleation technique is one of the several demonstrated controlled ice nucleation technologies and relies on the rapid discharge of an inert pressurized gas to induce ice nucleation. In this work, a series of custom wireless gas pressure and temperature sensors were developed and applied to this process to better understand the mechanism of controlled ice nucleation by depressurization. The devices capture highly transient conditions both in the chamber near the vial and within the vial headspace throughout the entire process. The effects of ballast gas composition, initial charge pressure, and vial size on gas pressure and headspace/chamber temperature are explored individually. We model the depressurization as an isentropic process, allowing the influence of these parameters to be evaluated quantitatively. It is demonstrated that monatomic gases (e.g. argon) with low thermal conductivity produce the most favorable conditions for ice nucleation at the end of depressurization, based on temperature drop in the vial headspace. Experimental data also reveal a correlation between initial charge pressure and vial size with the temperature drop within the vial headspace, during depressurization. These findings ultimately provide deeper insight into the rapid depressurization based controlled ice nucleation process and help lay the foundation for a more robust process development and control.

The Effect of Different Freezing Rates and Long-Term Storage Temperatures on the Stability of Sliced Peaches

The purpose of this research was to determine if freezing rates and holding temperatures influence peach quality during short- and long-term frozen storage. Fresh peaches (Prunus persica) were purchased locally, sliced, dipped in 2% ascorbic acid then drained, and packaged. The study was divided into two experiments, one to determine the effect of the freezing rate on peach quality and the second to determine the effect of frozen holding temperatures on peach quality. For the freezing rate experiment, freshly packaged peaches were placed in freezers at different temperatures (-7°C, -12°C, -18°C, -29°C, and -77°C) then removed for testing when the core temperature of the peaches reached the temperature of all freezer temperatures. The second experiment determined the long-term holding effect on quality using both fresh and prefrozen peaches held at -7°C, -12°C, -18°C, -29°C, and -77°C through 360 days. Quality measurements included freeze thaw and weight loss, lightness, firmness, moisture content, ascorbic acid equivalent antioxidant capacity (AAEAC), hexanal detection using gas chromatography (GC), scanning electron microscopy (SEM), and sensory evaluation. During the freezing phase (experiment 1), peach weight loss and surface ice crystal pore size significantly decreased with increased freezing rates. Peaches held at -77°C and -29°C maintained overall quality to a greater degree than the higher holding temperatures. However, all samples enzymatically browned when thawed; therefore, frozen peaches may best if used in the frozen state or in applications where appearance is a critical factor. In general, fresh and prefrozen peaches were not acceptable by the sensory panelists after 270 days of frozen storage.

Instability of therapeutic proteins - An overview of stresses, stabilization mechanisms and analytical techniques involved in lyophilized proteins

Solid-state is the preferred choice for storage of protein therapeutics to improve stability and preserve the biological activity by decreasing the physical and chemical degradation associated with liquid protein formulations. Lyophilization or freeze-drying is an effective drying method to overcome the instability problems of proteins. However, the processing steps (freezing, primary drying and secondary drying) involved in the lyophilization process can expose the proteins to various stress and harsh conditions, leading to denaturation, aggregation often a loss in activity of protein therapeutics. Stabilizers such as sugars and surfactants are often added to protect the proteins against physical stress associated with lyophilization process and storage conditions. Another way to curtail the degradation of proteins due to process related stress is by modification of the lyophilization process. Slow freezing, high nucleation temperature, decreasing the extent of supercooling, and annealing can minimize the formation of the interface (ice-water) by producing large ice crystals with less surface area, thereby preserving the native structure and stability of the proteins. Hence, a thorough understanding of formulation composition, lyophilization process parameters and the choice of analytical methods to characterize and monitor the protein instability is crucial for development of stable therapeutic protein products. This review provides an overview of various stress conditions that proteins might encounter during lyophilization process, mechanisms to improve the stability and analytical techniques to tackle the proteins instability during both freeze-drying and storage.

Pressure-related cooling and freezing techniques for the food industry: fundamentals and applications

Cooling and freezing are two widely used methods for food preservation. Conventional cooling and freezing techniques are usually with low efficiency and prone to damage foodstuffs. In order to increase cooling and freezing efficiencies and ensure better food quality, many efforts have been performed. As effective solutions, pressure-related techniques such as vacuum cooling (VC), vacuum film cooling (VFC), vacuum spray cooling (VSC), pressure shift freezing (PSF) and isochoric freezing (ICF) have attracted a lot of interests. The current review intends to provide an overview of pressure-related cooling and freezing techniques for the food industry. In the review, the fundamentals including principles, experimental systems, thermodynamic and kinetic mechanisms and their relevant mathematical models are presented, latest applications of these techniques in the food industry are summarized, and future trends concerning technological development and industrialization are highlighted. Pressure plays an important role in improving the cooling and freezing processes and ensuring food qualities, and mathematical modeling is an effective tool for understanding the thermodynamic and kinetic mechanisms of these processes. However, the latest researches showed that despite many merits of these pressure-related processes, limitations still exist in applying some of the techniques in the food industry. For achieving technological development and industrialization of the pressure-related processes, further researches should focus on improving model performance, integrating multiple technologies, and cost control.