Preparation, isolation and hypothermia protection activity of antifreeze peptides from shark skin collagen

Ice recrystallization inhibition activity of pulse protein hydrolysates after immobilized metal affinity separation

Creating molecules capable of inhibiting ice recrystallization is an active research area aiming to improve the freeze-thaw characteristics of foods and biomedical materials. Peptide mixtures have shown promise in preventing freezing-induced damage, but less is known about the relationship between their amino acid compositions and ice recrystallization inhibition (IRI) activities. In this article, we used Ni2+ immobilized metal affinity chromatography (IMAC) to fractionate pulse protein hydrolysates, created by Alcalase and trypsin, into mixtures lacking and enriched in His, and Cys residues. The aim of this study was to fractionate pulse protein hydrolysates based on their amino acid compositions and evaluate their resulting physicochemical and IRI characteristics. Ni2+ IMAC fractionation induced IRI activity in all of the evaluated soy, chickpea, and pea protein hydrolysates regardless of their amino acid composition. Ni2+ IMAC fractionation produced chemically distinct fractions of peptides, differing by their molecular weights, amino acid composition, and IRI activities. The resulting peptide mixtures' molecular weight, amino acid composition, secondary structure, and sodium ion levels were found to have no correlation with their IRI activities. Thus, we demonstrate for the first time the ability of Ni2+ IMAC fractionation to induce IRI activity in hydrolyzed pulse proteins.

Cryoprotective Activity of Different Characterized Fractions Isolated from Enzymatic Hydrolysates of Croceine Croaker (Pseudosciaena crocea)

In this study, ultrafiltration fractions (<3 k Da, LMH; >3 k Da, HMH) and solid-phase extraction fractions (hydrophilic hydrolysate, HIH; hydrophobic hydrolysate, HOH) from trypsin hydrolysate purified from croceine croaker (Pseudosciaena crocea) isolate were obtained to investigate the cryoprotective effects of the different fractions, achieved by means of maceration of turbot fish meat after three freeze-thaw cycles. Alterations in the texture, color, moisture loss, myofibrillar protein oxidation stability and conformation, and microstructure of the fish were analyzed after freezing and thawing. The results demonstrate that HIH maximized the retention of fish texture, reduced moisture loss, minimized the oxidation and aggregation of myofibrillar proteins, and stabilized the secondary and tertiary structures of myofibrillar proteins compared to the control group. In conclusion, the HIH component in the trypsin hydrolysates of croceine croaker significantly contributes to minimizing freeze damage in fish meat and acts as an anti-freezing agent with high industrial application potential.

Selenium-Chelating Peptide Derived from Wheat Gluten: In Vitro Functional Properties

The efficacy of selenium-chelating polypeptides derived from wheat protein hydrolysate (WPH-Se) includes enhancing antioxidant capacity, increasing bioavailability, promoting nutrient absorption, and improving overall health. This study aimed to enhance the bioavailability and functional benefits of exogenous selenium by chelating with wheat gluten protein peptides, thereby creating bioactive peptides with potentially higher antioxidant capabilities. In this study, WPH-Se was prepared with wheat peptide and selenium at a mass ratio of 2:1, under a reaction system at pH 8.0 and 80 °C. The in vitro antioxidant activity of WPH-Se was evaluated by determining the DPPH, OH, and ABTS radical scavenging rate and reducing capacity under different conditions, and the composition of free amino acids and bioavailability were also investigated at various digestion stages. The results showed that WPH-Se possessed significant antioxidant activities under different conditions, and DPPH, OH, and ABTS radical scavenging rates and reducing capacity remained high at different temperatures and pH values. During gastrointestinal digestion in vitro, both the individual digestate and the final digestate maintained high DPPH, OH, and ABTS radical scavenging rates and reducing capacity, indicating that WPH-Se was able to withstand gastrointestinal digestion and exert antioxidant effects. Post-digestion, there was a marked elevation in tryptophan, cysteine, and essential amino acids, along with the maintenance of high selenium content in the gastrointestinal tract. These findings indicate that WPH-Se, with its enhanced selenium and amino acid profile, serves as a promising ingredient for dietary selenium and antioxidant supplementation, potentially enhancing the nutritional value and functional benefits of wheat gluten peptides.

Preparation of high content collagen peptides and study of their biological activities

Collagen peptides play an important role in the increasing use of collagen peptides as dietary supplements in food and beverages and as bioactive ingredients in cosmetics, healthcare, and pharmaceuticals. Collagenase enzymatically cleaves gelatin to produce collagen polypeptides. However, the enzymatic activity of collagenase is very low (25900 U) and does not allow for adequate enzymatic digestion. Therefore, proteases are used to assist in enzymatic digestion. Porcine gelatin, bovine gelatin, and fish protein gum were enzymatically digested, and the content of collagen peptides in the enzymatically digested lyophilized powder was identified by high-performance liquid chromatography and mass spectrometry, and then the content of the desired collagen peptides was increased by isolation and purification, and the result of the determination was that the content of collagen peptides was the highest after enzymatic digestion and isolation and purification with the use of porcine gelatin as the raw material, and the content of the collagen peptides was about 45.47%. β-nicotinamide mononucleotide (NMN) was mixed with the prepared samples to determine its antioxidant properties and ability to promote the growth of human dermal fibroblasts. The results showed that the antioxidant capacity was enhanced with the increase of collagen polypeptide content, and NMN could promote the scavenging of DPPH• and •OH free radicals by collagen polypeptides. The ability to promote the growth of human dermal fibroblasts was enhanced with the increase of collagen polypeptide content. This paper aimed to prepare a high content of collagen polypeptides from three raw materials, porcine gelatin, bovine gelatin, and fish protein gum, and further to determine the biological activities.

Effects of tamarind seed polysaccharides on physicochemical characteristics of frozen dough: structure-function relationship

BACKGROUND

Recently, frozen dough has become more popular because of its ability to be quickly transformed into freshly baked foods. During the storage and transport process, frozen dough can suffer some degree of damage caused by ice crystallization and recrystallization. Adding polysaccharides to frozen dough is a good way to solve this problem. Tamarind seed polysaccharide (TSP) has excellent ice crystal steady ability and has also been widely used in frozen foods. However, there is no study on the use of TSP in frozen dough.

RESULTS

TSP can stabilize the bound water content, inhibit the freezable water content, and increase elasticity. However, the dough with different structures of TSP added was less firm after 30 days of freezing compared to the dough without TSP, and the porosity and stomatal density of the prepared steamed bread gradually decreased. The addition of TSP reduced gluten deterioration during the freezing process, thus decreasing the collapse and uneven porosity of the steamed bread.

CONCLUSIONS

The results could provide new insights into the structure of TSP and its effect on the quality characteristics of frozen dough. © 2023 Society of Chemical Industry.

Ice Recrystallization Inhibition Activity of Soy Protein Hydrolysates

Identifying and developing ice recrystallization inhibitors from sustainable food proteins such as soy protein isolate (SPI) can lead to practical applications in both pharmaceutical and food industries. The objective of this study was to investigate the ice recrystallization inhibition (IRI) activity of SPI hydrolysates, and this was achieved by using an IRI activity-guided fractionation approach and relating IRI activity to interfacial molecular activity measured by vibrational sum frequency generation (VSFG). In addition, the impact of molecular weight (MW) and enzyme specificity was analyzed using three different proteases (Alcalase, trypsin, and pancreatin) and varying hydrolysis times. Using preparative chromatography, hydrolysates from each enzyme treatment were fractionated into five different MW fractions (F1-F5), which were then characterized by high-performance liquid chromatography (HPLC). All SPI hydrolysates had IRI activity, resulting in a 57-29% ice crystal diameter reduction when compared to native SPI. The F1 fraction (of 4-14 kDa) was most effective among all tested hydrolysates, while the lower MW peptide fractions lacked activity. One sample (SPI-ALC 20-F1) had a 52% reduction of ice crystal size at a lower concentration of 2% compared to the typical 4% used. SFG showed a difference in H-bonding and hydrophobic interactions of the molecules on the water/air interface, which may be linked to IRI activity. This study demonstrates for the first time the ability of SPI hydrolysates to inhibit ice crystal growth and the potential application of SFG to study molecular interaction at the interface that may help illustrate the mechanism of action.

Characterizations and the Mechanism Underlying Cryoprotective Activity of Peptides from Enzymatic Hydrolysates of Pseudosciaena crocea

Antifreeze peptides are a class of small molecule protein hydrolysates that protect frozen products from cold damage under freezing or subcooling conditions. In this study, three different Pseudosciaena crocea (P. crocea) peptides were from pepsin, trypsin, and neutral protease enzymatic hydrolysis. It aimed to elect the P. crocea peptides with better activity through molecular weight, antioxidant activity, and amino acid analysis, as well as to compare the cryoprotective effects with a commercial cryoprotectant. The results showed that the untreated fillets were prone to be oxidized, and the water-holding capacity after freeze-thaw cycle decreased. However, the treatment of the trypsin hydrolysate of P. crocea protein significantly promoted the water-holding capacity level and reduced the loss of Ca²⁺-ATP enzyme activity and the structural integrity damage of myofibrillar protein in surimi. Moreover, compared with 4% sucrose-added fillets, trypsin hydrolysate treatment enhanced the umami of frozen fillets and reduced the unnecessary sweetness. Therefore, the trypsin hydrolysate of P. crocea protein could be used as a natural cryoprotectant for aquatic products. Hence, this study provides technical support for its use as a food additive to improve the quality of aquatic products after thawing and provides a theoretical basis and experimental foundation for the in-depth research and application of antifreeze peptides.

Identification of Novel Antifreeze Peptides from Takifugu obscurus Skin and Molecular Mechanism in Inhibiting Ice Crystal Growth

Foodborne hydrolyzed antifreeze peptides have been widely used in the food industry and the biomedical field. However, the components of hydrolyzed peptides are complex and the molecular mechanism remains unclear. This study focused on identification and mechanism analysis of novel antifreeze peptides from Takifugu obscurus skin by traditional methods and computer-assisted techniques. Results showed that three peptides (EGPRAGGAPG, GDAGPSGPAGPTG, and GEAGPAGPAG) possessed cryoprotection via reducing the freezing point and inhibiting ice crystal growth. Molecular docking confirmed that the cryoprotective property was related to peptide structure, especially α-helix, and hydrogen bond sites. Moreover, the antifreeze peptides were double-faces, which controlled ice crystals while affecting the arrangement of surrounding water molecules, thus exhibiting a strong antifreeze activity. This investigation deepens the comprehension of the mechanism of antifreeze peptides at molecular scale, and the novel efficient antifreeze peptides can be developed in antifreeze materials design and applied in food industry.

The Antifreeze and Cryoprotective Activities of a Novel Antifreeze Peptide from Ctenopharyngodon idella Scales

The purpose of this study is to obtain new antifreeze peptides (AFPs) that are natural, safe, and high activity from Ctenopharyngodon idella scales. The optimal hydrolysis conditions were investigated, and chromatography-based isolation was conducted using thermal hysteresis activity (THA) as an index. Molecular dynamic simulation (MDs) was explored to reveal the antifreeze mechanism of the AFPs. The results showed that the optimal hydrolysis conditions were 4000 U/g papain enzyme for 60 °C at pH 5.0 and substrate concentration (1:10) for 3 h, as unveiled by single-factor experiment results. The AFPs documented a THA of 2.7 °C when the T_h was 1.3 °C. Hydrophilic peptide, named GCFSC-AFPs, with a THA of 5.09 °C when the T_h was 1.1 °C was obtained after a series isolation of gel filtration, ion exchange, and reversed-phase HPLC chromatography. The AFPs had a molecular weight of 1107.54~1554.72 Da with three main peptides in the amino acid sequence of VGPAGPSGPSGPQ, RGSPGERGESGPAGPSG, and VGPAGPSGPSGPQG, respectively. The survival rate of yeast with GCFSC-AFPs reached 84.4% following one week of exposure at −20 °C. MDs indicated that GCFSC-AFPs interfered with the ice-water interaction and thus inhibited the ice crystallization process. Our data suggested that the GCFSC-AFPs were a novel and potential antifreeze agent in the food industry.

Preparation, Characterization, and Mechanism of Antifreeze Peptides from Defatted Antarctic Krill (Euphausia superba) on Lactobacillus rhamnosus

Defatted Antarctic krill powder is the main by-product in the manufacturing of krill oil. Exploring a high value-added approach for utilizing this protein-rich material has received much attention in research and industry. Given this, the preparation and primary characterization of antifreeze peptides from defatted Antarctic krill (AKAPs) were carried out in this study. The cryoprotective effect of AKAPs on Lactobacillus rhamnosus ATCC7469 was also investigated. The results showed that Protamex was the optimum protease for AKAP preparation from defatted Antarctic krill. AKAPs were found to be rich in short peptides, with the MW ranging from 600 to 2000 Da (69.2%). An amino acid composition analysis showed that AKAPs were rich in glutamic acid (18.71%), aspartic acid (12.19%), leucine (7.87%), and lysine (7.61%). After freezing, the relative survival rate of Lactobacillus rhamnosus in the 1.0 mg/mL AKAP-treated group (96.83%) was significantly higher than in the saline group (24.12%) (p < 0.05). AKAPs also retarded the loss of acidifying activity of L. rhamnosus after freezing. AKAPs showed even better cryoprotective activity than three commercial cryoprotectants (sucrose, skim milk, and glycerol). In addition, AKAPs significantly alleviated the decrease in β-galactosidase and lactic dehydrogenase activities of L. rhamnosus (p < 0.05). Furthermore, AKAPs effectively protected the integrity of L. rhamnosus cell membranes from freezing damage and alleviated the leakage of intracellular substances. These findings demonstrate that AKAPs can be a potential cryoprotectant for preserving L. rhamnosus, providing a new way to use defatted Antarctic krill.

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.

Preparation and Characterization of Thermally Stable Collagens from the Scales of Lizardfish (Synodus macrops)

Marine collagen is gaining vast interest because of its high biocompatibility and lack of religious and social restrictions compared with collagen from terrestrial sources. In this study, lizardfish (Synodus macrops) scales were used to isolate acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). Both ASC and PSC were identified as type I collagen with intact triple-helix structures by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and spectroscopy. The ASC and PSC had high amino acids of 237 residues/1000 residues and 236 residues/1000 residues, respectively. Thus, the maximum transition temperature (T_max) of ASC (43.2 °C) was higher than that of PSC (42.5 °C). Interestingly, the T_max of both ASC and PSC was higher than that of rat tail collagen (39.4 °C) and calf skin collagen (35.0 °C), the terrestrial collagen. Solubility tests showed that both ASC and PSC exhibited high solubility in the acidic pH ranges. ASC was less susceptible to the “salting out” effect compared with PSC. Both collagen types were nontoxic to HaCaT and MC3T3-E1 cells, and ASC was associated with a higher cell viability than PSC. These results indicated that ASC from lizardfish scales could be an alternative to terrestrial sources of collagen, with potential for biomedical applications.

Survivability of Collagen-Peptide Microencapsulated Lactic Acid Bacteria during Storage and Simulated Gastrointestinal Conditions

The intracellular homeostasis of lyophilized lactic acid bacteria (LAB) is destroyed by extreme cold stress, resulting in decreased stability. This study aimed to verify the validity of collagen as a potential protective agent for improving microbial stability deteriorated by freezing. The collagen types used in this study were low molecular weight collagen (LC) of less than 1000 Da and low molecular weight collagen-peptide (LCP) of less than 300 Da. By the accelerated stability test according to the addition of each collagen type, a 3% LCP displaying a protective effect on the viability of various LAB strains (Lactoplantibacillus plantarum MG989, Lactococcus lactis MG5125, Enterococcus faecium MG5232, Bifidobacterium animalis ssp. lactis MG741, and Streptococcus thermophilus MG5140) was finally selected. It was evaluated whether LCP enhances bacterial stability, survivability in the gastrointestinal (GI) tract, and heat resistance. LCP significantly improved the viability of all strains in the GI tract compared to sucrose and skim milk, which are conventional protective agents. Based on morphological observations, LCP was uniformly coated on the cell surface, resulting in protective effects against multiple external stress stimuli. Such findings indicate the applicability of LCP as an unprecedented protective agent, which can improve the stability of various probiotics with antifreeze effects.

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

Ice crystal growth during cold storage presents a quality problem in frozen foods. The development of appropriate technical conditions and ingredient formulations is an effective method for frozen food manufacturers to inhibit ice crystals generated during storage and distribution. Ice-binding proteins (IBPs) have great application potential as ice crystal growth inhibitors. The ability of IBPs to retard the growth of ice crystals suggests that IBPs can be used as a natural ice conditioner for a variety of frozen products. In this review, we first discussed the damage caused by ice crystals in frozen foods during freezing and frozen storage. Next, the methods and technologies for production, purification and evaluation of IBPs were summarized. Importantly, the present review focused on the characteristics, structural diversity and mechanisms of IBPs, and the application advances of IBPs in food industry. Finally, the challenges and future perspectives of IBPs are also discussed. This review may provide a better understanding of IBPs and their applications in frozen products, providing some valuable information for further research and application of IBPs.

Effects of gelatin-based antifreeze peptides on cell viability and oxidant stress of Streptococcus thermophilus during cold stage

Cold stage adversely affects cell proliferation and cell viability of probiotics such as Streptococcus thermophilus in food industry, new type of cryoprotectants continues to be needed. Gelatin-based antifreeze peptide becomes a popular topic because of its cryoprotective effects on cold-stressed probiotics. In this study the effects of tilapia scales antifreeze peptides (TSAPP) on cell viability and oxidant stress of S. thermophilus during cold stage were investigated. The results showed that the percentage of viable cells was increased 10.85 folds compared with control groups. Addition of TSAPP activated the activities of ATPases, relieved the hyperpolarization of cell membrane potential and regulated the intracellular Ca2+ concentration. Furthermore, TSAPP significantly inhibited reactive oxygen species level and malonaldehyde content in cells. Under cryopreservation with TSAPP, cells of S. thermophilus maintained higher activities of antioxidant enzymes including catalase, peroxidase and total antioxidant capacity. These findings indicate that TSAPP likely offered its cellular protection by maintaining membrane integrity and alleviation of oxidative stress.

Cryoprotective Effects of Protein Hydrolysates Prepared from By-Products of Silver Carp (Hypophthalmichthys Molitrix) on Freeze-Thawed Surimi

The cryoprotective effects of different amounts of protein hydrolysates prepared from by-products of silver carp using Protamex and Alcalase on surimi that were subjected to six freeze-thaw cycles were investigated. Commercial cryoprotectant (8% w/w 1:1 sucrose-sorbitol blend, SuSo) and control (without cryoprotectant) groups were used for comparison. After six freeze-thaw cycles, the lowest actomyosin extractability, Ca2+-ATPase activity and total sulfhydryl content, along with the highest surface hydrophobicity of actomyosin, were observed in the control group (P < 0.05). On the contrary, the group with addition of 2 g of hydrolysate prepared by Protamex hydrolysis (PH-2) displayed the highest actomyosin extractability, Ca2+-ATPase activity and correspondingly, lowest surface hydrophobicity of actomyosin (P < 0.05). Total sulfhydryl content of actomyosin and textural properties of heat-set surimi gels were similar between samples with PH-2 and those with SuSo (P > 0.05). Differences in molecular weight distribution, total and free amino acid compositions between the hydrolysates prepared by Protamex and Alcalase hydrolysis were possible reasons attributing to their variable cryoprotective effects on freeze-thawed surimi. Results from this study clearly support that hydrolysate prepared by Protamex hydrolysis at an appropriate amount could serve as an effective cryoprotectant without increasing the sweetness of surimi products. Furthermore, our findings suggest that the hydrolysates follow a different cryoprotection mechanism compared to SuSo (sucrose-sorbitol blend).

Matrikines for therapeutic and biomedical applications

Matrikines, peptides originating from the fragmentation of extracellular matrix proteins are identified to play important role in both health and disease. They possess biological activities, much different from their parent protein. Identification of such bioactive cryptic regions in the extracellular matrix proteins has attracted the researchers all over the world in the recent decade. These bioactive peptides could find use in preparation of biomaterials and tissue engineering applications. Matrikines identified in major extracellular matrix (ECM) proteins like collagen, elastin, fibronectin, and laminin are being extensively studied for use in tissue engineering and regenerative medicine. They are identified to modulate cellular activity like cell growth, proliferation, migration and may induce apoptosis. RGD, a well-known peptide identified in fibronectin with cell adhesive property is being investigated in designing biomaterials. Collagen hexapeptide GFOGER was found to promote cell adhesion and differentiation. Laminin also possesses regions with strong cell adhesion property. Recently, cell-penetrating peptides from elastin are used as a targeted delivery system for therapeutic drugs. The continued search for cryptic sequences in the extracellular matrix proteins along with advanced peptide coupling chemistries would lead to biomaterials with improved surface properties. This review article outlines the peptides derived from extracellular matrix and some of the possible applications of these peptides in therapeutics and tissue engineering applications.

Phytonutrient and anti-diabetic functional properties of flavonoid-rich ethanol extract from Angelica Keiskei leaves

An extraction method was optimized to get a flavonoid-rich ethanol extract from Angelica keiskei leaves (FREE-AK). Trace elements and total flavonoid content of FREE-AK were identified, and the hypoglycemic and hypolipidemic effects of FREE-AK were studied in streptozotocin-induced diabetic mice. For FREE-AK extraction the optimal conditions were 65% ethanol, 45 °C and 15 min, resulting in a total flavonoid content up to 10.18% and K, Mg, Na, and Ca, content of about 36.59, 1.52, 14.51 and 7.486 mg/g, respectively. FREE-AK uptake could cause a marked decrease of fasting blood glucose and a significant improvement on glucose tolerance in diabetic mice. In addition, FREE-AK treatment with a dose of 800 mg/kg b.w. resulted in a reduction in the total triglyceride level (TC) in serum. Results demonstrated the effectiveness of FREE-AK for hypoglycemia and hypolipidemia in streptozotocin-induced mice and FREE-AK may be a potential dietary treatment for type 2 diabetes.

Characterization, Preparation, and Purification of Marine Bioactive Peptides

Marine bioactive peptides, as a source of unique bioactive compounds, are the focus of current research. They exert various biological roles, some of the most crucial of which are antioxidant activity, antimicrobial activity, anticancer activity, antihypertensive activity, anti-inflammatory activity, and so forth, and specific characteristics of the bioactivities are described. This review also describes various manufacturing techniques for marine bioactive peptides using organic synthesis, microwave assisted extraction, chemical hydrolysis, and enzymes hydrolysis. Finally, purification of marine bioactive peptides is described, including gel or size exclusion chromatography, ion-exchange column chromatography, and reversed-phase high-performance liquid chromatography, which are aimed at finding a fast, simple, and effective method to obtain the target peptides.

Identification and Evaluation of Cryoprotective Peptides from Chicken Collagen: Ice-Growth Inhibition Activity Compared to That of Type I Antifreeze Proteins in Sucrose Model Systems

The ability of chicken collagen peptides to inhibit the growth of ice crystals was evaluated and compared to that of fish antifreeze proteins (AFPs). This ice inhibition activity was assessed using a polarized microscope by measuring ice crystal dimensions in a sucrose model system with and without collagen peptides after seven thermal cycles. The system was stabilized at -25 °C and cycled between -16 and -12 °C. Five candidate peptides with ice inhibition activity were identified using liquid chromatography and tandem mass spectrometry and were then synthesized. Their ice inhibition capacity was compared to that of type I AFPs in a 23% sucrose model system. Specific collagen peptides with certain amino acid sequences reduced the extent of ice growth by approximately 70% at a relatively low concentration (1 mg/mL). These results suggest that specific collagen peptides may act in a noncolligative manner, inhibiting ice crystal growth like type I AFPs, but less efficiently.

Chicken collagen hydrolysate cryoprotection of natural actomyosin: Mechanism studies during freeze-thaw cycles and simulated digestion

The cryoprotective effect of chicken collagen hydrolysate (CCH) obtained from chicken skin was investigated at 0%, 4%, 8% and 12% (w/w) on natural actomyosin (NAM) model system to elucidate the possible mechanism. Ice dimensions in the NAM dispersions were measured after 7 thermal cycles (stabilized at -20°C and cycled between -16°C to -12°C) using a polarized microscope, demonstrating a significant reduction of ice crystal size induced by CCH. To determine the ice-controlling effect of CCH on protein freeze-denaturation, NAM samples were subjected to 7 freeze-thaw cycles between -20°C and 4°C. The results suggest that the presence of CCH can inhibit the ice crystals growth in NAM to reduce protein freeze-denaturation and oxidation similarly to the commercial cryoprotectants, resulting in higher protein solubility and a better gel structure with higher digestibility after freeze-thaw cycles.

Microbial collagenases: challenges and prospects in production and potential applications in food and nutrition

Microbial collagenases are promising enzymes in view of their extensive industrial and biological applications.

Revisão: Proteínas anticongelantes – uma tecnologia emergente para o congelamento de alimentos

Um dos métodos mais tradicionais na conservação de alimentos, o congelamento também pode alterar de forma significativa as características do produto. Grandes cristais de gelo provocam alteração na textura e/ou danos a membranas e componentes celulares. As técnicas de congelamento rápido formam cristais de gelo menores do que o processo lento, porém as flutuações de temperatura durante a distribuição e transporte podem promover o crescimento dos cristais. Esse processo é conhecido como recristalização e é uma barreira na utilização do congelamento como método de conservação em muitos casos. O uso de crioprotetores tradicionais, como a sacarose, é uma alternativa limitada, uma vez que concentrações elevadas são requeridas. Na década de 1970, foi descrita em peixes de águas frias uma classe de proteínas que, em baixa concentração, pode interagir e influenciar o crescimento do cristal de gelo. Elas foram chamadas de proteínas anticongelantes (PACs), sendo encontradas também em plantas, animais e micro-organismos ambientados a baixas temperaturas. Essas proteínas podem intervir no processo de formação do núcleo inicial do gelo, reduzir o ponto de congelamento da água, ou, ainda, inibir a recristalização, principalmente para PACs de vegetais. Há diversos trabalhos publicados e algumas patentes registradas para o uso de PACs em diversos alimentos, como lácteos, carnes, massas, frutas e hortaliças, conservando de melhor forma as características originais do alimento. Atualmente, o custo ainda é uma barreira para utilização comercial das PACs. Contudo, a descoberta de novas fontes pode reduzir seu custo e tornar essas proteínas uma ferramenta efetiva na manutenção da textura de alimentos congelados. Baseada em trabalhos que avaliaram aspectos químicos das PACs e exemplos de sua aplicação, esta revisão tem como objetivo principal apresentar as características gerais das PACs e discutir sobre sua utilização.