Ice-binding proteins: a remarkable ice crystal regulator for frozen foods

Dual cryoprotection of gelatin-tea polyphenol microgels on surimi by targeting for ice inhibition and component stabilization

In this study, the gelatine-polyphenol microgels with dual cryoprotective roles were constructed by regulating the ratio of gelatin to tea polyphenols (1:50-1:250). The physicochemical attributes, ice recrystallization inhibition ability of microgels, and their dosage effects (1 %, 2.5 % and 4 %, w/w) on surimi were investigated. The results indicated that increased gelatin caused the reduced size and enhanced viscosity of microgels. Except for high viscosity and antioxidant activity, the GP-5 group also showed great IRI ability with minimum size distribution (125-214 μm2) of ice crystals. Furthermore, 2.5 G group and S group had a comparable TVB-N (3.81, 4.34 mg/100 g), TBARS (1.18, 1.32 mg/kg), sulfhydryl contents (29.52, 25.48 μmol/g) and Ca2+-ATPase activity (0.44, 0.36 μmolPi/gprot/h). Compared to uneven free water distribution of control group, S and 2.5 G group show more even immobilized-water distribution. Thereafter, the dual cryoprotective functions of microgels in surimi offer valuable insights for the development of effective antifreeze agents.

Insight into the structure-activity relationship of thermal hysteresis activity of cod collagen peptides through peptidomics and bioinformatics approaches

To elucidate the correlation between variations in thermal hysteresis activity (THA) and the physicochemical properties and structure, antifreeze peptides (AFPs) of isolated fractions (CCP-1 and CCP-2) were characterized on based peptidomics and bioinformatics. The results revealed a positive correlation between the THA of cod collagen antifreeze peptide (CCAFP) and peptide chain length, isoelectric point, and hydrophobic amino acid content. Notably, the THA of CCP-1, which has higher alkaline amino acid content, was 2.60 °C at a concentration of 10 mg/mL, significantly higher than CCP (1.90 °C) and CCP-2 (2.27 °C). Glycine, proline, and valine were the vital amino acids to the formation of hydrogen bonds. Conversely, aspartic and glutamic acids at terminal regions of AFPs tended to introduce kinks in their structures. This distortion reduced binding sites for ice crystals, thereby decreasing their THA, providing a theory for understanding the physicochemical properties and structure of AFPs that influence their THA.

Identification of novel antifreeze peptides from yak skin gelatin ultrasound-assisted enzymatic hydrolysate

In this paper, a new type of antifreeze peptide was identified from the ultrasonic-assisted enzymolysis product of yak skin. First, the antifreeze peptides were obtained by ultrasonic-assisted enzymolysis of yak skin gelatin. The obtained peptides with 150 W ultrasound treatment could increase the survival rate of Lactobacillus plantarum from 16 % to 60 % after four freeze-thaw cycles. Then, the component with the highest antifreeze activity in the peptides' ultrafiltration product was analyzed by LC-MS/MS to obtain 961 peptides. After screening of antifreeze activity and physical properties, three antifreeze peptide sequences were obtained (S1: GERGGPGGPGPQ, S2: PGGAEGPGRDAQQP, S3: VAPPGAPKKEH). DSC analysis, Lactobacillus plantarum cryoprotection experiments and molecular docking showed that the S1 sequence had the best antifreeze activity. This study provides a new idea for the high-value utilization of yak by-products and a potential candidate for food antifreeze agents.

Potential role of ice-binding protein in mitochondria-lipid and ATP mechanisms during freezing of plant callus

Plant calli, a perpetually undifferentiated cell culture, have defects in maintaining their genetic fidelity during prolonged tissue culture. Cryopreservation using ice-binding proteins (IBP) is a potential solution. Despite a few studies on cryopreservation using IBPs in plant calli, detailed insights into the intracellular metabolism during freezing, thawing, and re-induction remain sparse. This study investigated and employed IBP from polar yeast Leucosporidium sp. (LeIBP) in the cryopreservation process across diverse taxa, including gymnosperms, monocots, dicots, and woody plants. Molecular-level analyses encompassing reactive oxygen species levels, mitochondrial function, and ATP and lipophilic compounds content were conducted. The results across nine plant species revealed the effects of LeIBP on callus competency post-thawing, along with enhanced survival rates, reactive oxygen species reduction, and restored metabolic activities to the level of those of fresh calli. Moreover, species-specific survival optimization with LeIBP treatments and morphological assessments revealed intriguing extracellular matrix structural changes post-cryopreservation, suggesting a morphological strategy for maintaining the original cellular states and paracrine signaling. This study pioneered the comprehensive application of LeIBP in plant callus cryopreservation, alleviating cellular stress and enhancing competence. Therefore, our findings provide new insights into the identification of optimal LeIBP concentrations, confirmation of genetic conformity post-thawing, and the intracellular metabolic mechanisms of cryopreservation advancements in plant research, thereby addressing the challenges associated with long-term preservation and reducing labor-intensive cultivation processes. This study urges a shift towards molecular-level assessments in cryopreservation protocols for plant calli, advocating a deeper understanding of callus re-induction mechanisms and genetic fidelity post-thawing.

Food-derived peptides unleashed: emerging roles as food additives beyond bioactivities

Innovating food additives stands as a cornerstone for the sustainable evolution of future food systems. Peptides derived from food proteins exhibit a rich array of physicochemical and biological attributes crucial for preserving the appearance, flavor, texture, and nutritional integrity of foods. Leveraging these peptides as raw materials holds great promise for the development of novel food additives. While numerous studies underscore the potential of peptides as food additives, existing reviews predominantly focus on their biotic applications, leaving a notable gap in the discourse around their abiotic functionalities, such as their physicochemical properties. Addressing this gap, this review offers a comprehensive survey of peptide-derived food additives in food systems, accentuating the application of peptides' abiotic properties. It furnishes a thorough exploration of the underlying mechanisms and diverse applications of peptide-derived food additives, while also delineating the challenges encountered and prospects for future applications. This well-time review will set the stage for a deeper understanding of peptide-derived food additives.

Composition-antifreeze property relationships of gelatin and the corresponding mechanisms

The inherent functional fractions (gelation and ice-affinitive fractions) of gelatin enable it as a promising cryoprotectant alternative. However, the composition-antifreeze property relationships of gelatin remain to be investigated. In this study, the HW-PSG and LW-PSG fractions of gelatin from fish scales were obtained, according to the critical gelation conditions and ice-binding measurements, respectively. Thermal hysteresis (THA) value, associated with ice nucleation, of LW-PSG was higher than that of HW-PSG. Besides, the relatively low-sized ice crystals (210-550 μm2) indicated that HW-PSG showed strong ice recrystallization inhibition (IRI) ability, compared to other groups. These results suggested that LW-PSG inhibited ice nucleation, while HW-PSG displayed the strong IRI ability. Furthermore, the antifreeze mechanisms were clarified through IRI measurements and molecular dynamics simulation. The minimum size of ice crystals was found for HW-PSG gels with dense microstructure, suggesting the HW-PSG retarded the growth of ice crystals by restricting the migration and phase transformation of water molecules. The hydrogen bond interactions between the ice crystal surface and ASN1294 and PRO1433 residues of LW-PSG, and hydrophobic interactions contributed to inhibiting the nucleation of ice crystals. This study provided some references to further enhance antifreeze performance of gelatin by modulating fragment composition.

Structural and physicochemical characteristics of wheat starch as influenced by freeze-thawed cycles and antifreeze protein from Sabina chinensis (Linn.) Ant. cv. Kaizuca leaves

The effects of freeze-thawed cycles (FTs) and a new antifreeze protein from Sabina chinensis (Linn.) Ant. cv. Kaizuca leaves (ScAFP) on the structure and physicochemical characteristics of wheat starch were studied. The mechanical breaking exerted by ice crystals on starch granules during FTs gradually deepened, sequentially squeezing the surface (2-6 FTs), amorphous region (8 FTs) and crystalline region (10 FTs) of starch granules. These changes led to reduced thermal stability, increased retrogradation tendency, and weakened gel network structure. The addition of ScAFP retarded the damage of ice crystals on starch granule structure and crystal structure during FTs, and significantly reduced the retrogradation tendency. Compared with native starch, the hardness of freeze-thawed starch without and with added ScAFP after 10 FTs decreased by 17.85% and 9.22%, respectively, indicating ScAFP improved the gel texture properties of freeze-thawed starch. This study provides new strategies for improving the quality of frozen starch-based foods.

Advanced review on type II collagen and peptide: preparation, functional activities and food industry application

Type II collagen is a homologous super-helical structure consisting of three identical α1(II) chains. It is a major component of animal cartilage, and is widely used in the food industry. Type II collagen can be extracted by acids, salts, enzymes, and via auxiliary methods and can be further hydrolyzed chemically and enzymatically to produce collagen peptides. Recent studies have shown that type II collagen and its polypeptides have good self-assembly properties and important biological activities, such as maintaining cartilage tissue integrity, inducing immune tolerance, stimulating chondrocyte growth and redifferentiation, and providing antioxidant benefits. This review focuses specifically on type II collagen and describes its structure, extraction, and purification, as well as the preparation of type II collagen peptides. In particular, the self-assembly properties and functional activities of type II collagen and collagen peptides are reviewed. In addition, recent research advances in the application of type II collagen and collagen peptides in functional foods, food additives, food coating materials, edible films, and carriers for the food industry are presented. This paper provides more detailed and comprehensive information on type II collagen and peptide for their application.

Progress in the application of novel cryoprotectants for the stabilization of myofibrillar proteins

In this review, the physicochemical and conformational changes of myofibrillar proteins (MPs) of freeze-induced mince-based aquatic foods were comprehensively summarized in depth. Studies have demonstrated that temperature fluctuation and long-time freezing negatively affect food quality, resulting in texture alteration, drip fluid, flavor degradation, and nutrition loss due to MPs denaturation, aggregation, and oxidation. Attempts have been made in ice-recrystallization inhibition, freezing point depression, and ice shape and growth control for better cryopreservation. Moreover, to further minimize the quality deterioration, cryoprotectants were acknowledged to reduce the denaturation and aggregation of the MPs effectively. Recently, interest in novel functional ingredients, including oligosaccharides, protein hydrolysates, and natural polyphenols demonstrated excellent cryoprotective effects while avoiding health concerns and undesirable flavor caused by traditional sugar-based or phosphates-based cryoprotectants. Therefore, the present review provides a systematic overview of these low molecular weight multifunctional substances with a particular sequence and highlights their underlying mechanism in the inhibition of ice recrystallization the stabilization of MPs.

New insight into the mechanism by which antifreeze peptides regulate the physiological function of Streptococcus thermophilus subjected to freezing stress

INTRODUCTION

Antifreeze peptides regulate the physiological functions of frozen cells and even their apoptosis; however, the mechanisms by which antifreeze peptides regulate these processes remain unclear, although the interactions between cell membranes and ice are well known to be important in this process.

OBJECTIVES

Our study aims to investigate how antifreeze peptides regulate cell physiological functions during the freezing process.

METHODS

We investigated the cryoprotective effect of rsfAFP on the physiological functions of S. thermophilus under freezing stress by measuring cellular metabolism activity, intracellular enzyme activity, cell membrane characterization, and cell apoptosis. The mechanism by which rsfAFP impacts S. thermophilus physiological functions under freezing stress was investigated using multispectral techniques and cryo-TEM.

RESULTS

We show that a recombinant antifreeze peptide (rsfAFP) interacts with the extracellular capsular polysaccharides and peptidoglycan of Streptococcus thermophilus and ice to cover the outer layer of the membrane, forming a dense protective layer that regulates the molecular structure of extracellular ice crystals, which results in reduced extracellular membrane damage, depressed apoptosis and increased intracellular metabolic activity. This interaction mechanism was indicated by the fact that S. thermophilus better maintained its permeability barrier, membrane fluidity, membrane structural integrity, and cytoplasmic membrane potential during freezing stress with rsfAFP treatment.

CONCLUSION

These results provide new insights into the mechanism by which rsfAFP regulates frozen cellphysiological functionsand apoptosis under freezing stress.

Molecular Factors of Ice Growth Inhibition for Hyperactive and Globular Antifreeze Proteins: Insights from Molecular Dynamics Simulation

The molecular mechanism behind the ice growth inhibition by antifreeze proteins (AFPs) is yet to be understood completely. Also, what physical parameters differentiate between the AFP and non-AFP are largely unknown. Thus, to get an atomistic overview of the differential antifreeze activities of different classes of AFPs, we have studied ice growth from different ice surfaces in the presence of a moderately active globular type III AFP and a hyperactive spruce budworm (sbw) AFP. Results are compared with the observations of ice growth simulations in the presence of topologically similar non-AFPs using all-atom molecular dynamics simulations. Simulation data suggest that the ice surface coverage is a critical factor in ice growth inhibition. Due to the presence of an ice binding surface (IBS), AFPs form a high affinity complex with ice, accompanied by a transition of hydration water around the IBS from clathrate-like to ice-like. Several residues around the periphery of the IBS anchor the AFP to the curved ice surface mediated by multiple strong hydrogen bonds, stabilizing the complex immensely. In the high surface coverage regime, the slow unbinding kinetics dominates over the ice growth kinetics and thus facilitates the ice growth inhibition. Due to the non-availability of a proper IBS, non-AFPs form a low-affinity complex with the growing ice surface. As a result, the non-AFPs are continuously repelled by the surface. If the concentration of AFPs is low, then the effective surface coverage is reduced significantly. In this low surface coverage regime, AFPs can also behave like impurities and are engulfed by the growing ice crystal.

Effect of antifreeze proteins on the freeze-thaw cycle of foods: fundamentals, mechanisms of action, current challenges and recommendations for future work

Freezing is widely used in food preservation, but if not carried out properly, ice crystals can multiply (nucleation) or grow (recrystallization) rapidly. This also affects thawing, causing structural damage and affecting overall quality. The objective of this review is to comprehensively study the cryoprotective effect of antifreeze proteins (AFPs), highlighting their role in the freeze-thaw process of food. The properties of AFPs are based on their thermal hysteresis capacity (THC), on the modification of crystal morphology and on the inhibition of ice recrystallization. The mechanism of action of AFPs is based on the adsorption-inhibition theory, but the specific role of hydrogen and hydrophobic bonds/residues and structural characteristics is also detailed. Because of the properties of AFPs, they have been successfully used to preserve the quality of a wide variety of refrigerated and frozen foods. Among the limitations of the use of AFPs, the high cost of production stands out, but currently there are solutions such as the use the production of recombinant proteins, cloning and chemical synthesis. Although in vitro, in vivo and human studies have shown that AFPs are non-toxic, their safety remains a matter of debate. Further studies are recommended to expand knowledge about AFPs, to reduce costs in their large-scale production, to understand their interaction with other food compounds and their possible effects on the consumer.

Effects and mechanism of antifreeze peptides from silver carp scales on the freeze-thaw stability of frozen surimi

The objective of this work was to investigate the cryoprotective effects of antifreeze peptides obtained from silver carp scales (ScAFPs) on the freeze-thaw stability of surimi, and to explore the action mechanisms of ScAFPs on frozen surimi. The comprehensive analysis of ice crystal size, myofibril protein oxidation, water retention, surimi gel properties, and rheological properties of surimi after different freeze-thaw cycles were investigated. Results showed that frozen surimi treated with ScAFPs exhibited a higher Ca²⁺-ATPase activity, salt-soluble protein concentration and sulfhydryl group content, while lower surface hydrophobicity, carbonyl content and disulfide bond content. Moreover, the gel properties and water holding capacity of surimi and surimi gel were improved significantly by regulating the size of ice crystals during freeze-thaw process. These findings indicate that ScAFPs could serviced as a new food ingredient with anti-freezing function for frozen products.

Antifreeze Peptides Preparation from Tilapia Skin and Evaluation of Its Cryoprotective Effect on Lacticaseibacillus rhamnosus

Antifreeze peptides can protect cell membranes and maintain the cell viability of probiotics under cold stress. Given this, antifreeze peptides were prepared from tilapia processing byproducts of tilapia skin by enzymolysis using the response surface methodology (RSM) method. The cryoprotective effects on Lacticaseibacillus rhamnosus ATCC7469 were investigated. Trypsin was selected as the protease for tilapia skin hydrolysis. The optimal hydrolysis conditions consisted of the amount of enzyme (2200 U/g), solid–liquid ratio (1:10, w/v), reaction temperature (49 °C), and reaction time (6.8 h), and the relative survival rate of L. rhamnosus reached 98.32%. Molecular weight (M_w) distribution and peptide sequences of the antifreeze peptides prepared from tilapia skin (APT) under the optimal conditions were analyzed. APT significantly reduced the leakage of extracellular proteins and protected β-galactosidase and lactate dehydrogenase activities of L. rhamnosus. Compared with the saline group, scanning electron microscopy (SEM) observation showed that cells had a more normal, smooth, and entire surface under the protection of APT. These findings indicate that APT can be a new cryoprotectant in preserving probiotics.

Novel synergistic freezing methods and technologies for enhanced food product quality: A critical review

Freezing has a long history as an effective food preservation method, but traditional freezing technologies have quality limitations, such as the potential for water loss and/or shrinkage and/or nutrient loss, etc. in the frozen products. Due to enhanced quality preservation and simpler thawing operation, synergistic technologies for freezing are emerging as the optimal methods for frozen food processing. This article comprehensively reviewed the recently developed synergistic technologies for freezing and pretreatment, for example, ultrasonication, cell alive system freezing, glass transition temperature regulation, high pressure freezing, pulsed electric field pretreatment, osmotic pretreatment, and antifreeze protein pretreatment, etc. The mechanisms and applications of these techniques are outlined briefly here. Though the application of new treatments in freezing is relatively mature, reducing the energy consumption in the application of these new technologies is a key issue for future research. It is also necessary to consider scale-up issues involved in large-scale applications as much of the research effort so far is limited to laboratory or pilot scale. For future development, intelligent freezing should be given more attention. Freezing should automatically identify and respond to different freezing conditions according to the nature of different materials to achieve more efficient freezing. PRACTICAL APPLICATION: This paper provides a reference for subsequent production and research, and analyzes the advantages and disadvantages of different novel synergistic technologies, which points out the direction for subsequent industry development and research. At the same time, it provides new ideas for the freezing industry.

Snow flea antifreeze peptide for cryopreservation of lactic acid bacteria

Cryogenic machining is one of the most commonly used techniques for processing and preserving in food industry, and traditional antifreeze agents cannot regulate the mechanical stress damage caused by ice crystals formed during recrystallization or thawing. In this study, we successfully developed an express system of a novel recombinant snow flea antifreeze peptide (rsfAFP), which has significant ice recrystallization inhibition ability, thermal hysteresis activity and alters ice nucleation, thus regulating extracellular ice crystal morphology and recrystallization. We showed that rsfAFP improved the survival rate, acid-producing ability, freezing stability, and cellular metabolism activity of Streptococcus thermophilus. We further showed that rsfAFP interacts with the membrane and ice crystals to cover the outer layer of cells, forming a dense protective layer that maintains the physiological functions of S. thermophilus under freezing stress. These findings provide the scientific basis for using rsfAFP as an effective antifreeze agent for lactic acid bacteria cryopreservation or other frozen food.

Recent development in evaluation methods, influencing factors and control measures for freeze denaturation of food protein

Frozen storage is most widely adopted preservation method to maintain food freshness and nutritional attributes. However, at low temperature, food is prone to chemical changes such as protein denaturation and lipid oxidation. In this review, we discussed the reasons and influencing factors that cause protein denaturation during freezing, such as freezing rate, freezing temperature, freezing method, etc. From the previous literatures, it was found that frozen storage is commonly used to prevent freeze induced protein denaturation by adding cryoprotectants to food. Some widely used cryoprotectants (for example, sucrose and sorbitol) have been reported with higher sweetness and weaker cryoprotective abilities. Therefore, this article comprehensively discusses the new cryopreservation methods and providing comparative study to the conventional frozen storage. Meanwhile, this article sheds light on the freeze induced alterations, such as change in functional and gelling properties. In addition, this article could be helpful for the prolonged frozen storage of food with minimum quality related changes. Meanwhile, it could also improve the commercial values and consumer satisfaction of frozen food as well.