Proteolysis and Its Control Using Protease Inhibitors in Fish and Fish Products: A Review

The inhibition mechanism of PostbioYDFF-3 on quality deterioration of refrigerated grass carp fillets from the perspective of endogenous enzyme and microorganisms changes

The protective mode of PostbioYDFF-3 (referred to as postbiotics) on the quality stability of refrigerated fillets was explored from the aspects of endogenous enzyme activity and the abundance of spoilage microorganisms. Compared to the control group, the samples soaked in postbiotics showed significant reductions in TVC, TVB-N and TBARS values by 39.6%, 58.6% and 25.5% on day 5, respectively. In addition, the color changes, biogenic amine accumulation and texture softening of the fish fillets soaked in postbiotics were effectively suppressed. Furthermore, the activity of endogenous enzyme activities was detected. The calpain activities were significantly inhibited (p < 0.05) after soaking in postbiotics, which declined by 23%. Meanwhile, high throughput sequencing analysis further indicated that the growth of spoilage microorganism such as Acinetobacter and Pseudomonas were suppressed. Overall, the PostbioYDFF-3 was suitable for preserving fish meat.

A review of inhibition mechanisms of surimi protein hydrolysis by different exogenous additives and their application in improving surimi gel quality

It is well known that aquatic products such as fish and shellfish, when stored for a long period of time under inappropriate conditions, can suffer from muscle softening. This phenomenon is mainly caused by endogenous proteases, which are activated during heating and accelerates the degradation of myofibrillar proteins, directly leading to weaker gels and poorer water retention capacity. This paper reviews the changes in fish proteins during storage after death and the factors affecting protein hydrolysis. A brief overview of the extraction of protease inhibitors, polysaccharides and proteins is given, as well as their mechanism of inhibition of protein hydrolysis in surimi and the current status of their application to improve the properties of surimi.

Insights into the fish protein degradation induced by the fish-borne spoiler Pseudomonas psychrophila and Shewanella putrefaciens: From whole genome sequencing to quality changes

The aim of this study is evaluating the protein degradation capacity of specific spoilage organisms (SSOs) Pseudomonas psychrophila and Shewanella putrefaciens in fish flesh during chilled storage and revealing the underlying genes by whole-genome sequencing (WGS). Biochemical and physical tests were performed on fish flesh inoculated with P. psychrophila and S. putrefaciens individually, including textural properties, myofibrillar fragmentation index, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles, free amino acid composition, total volatile basic nitrogen (TVB-N), trichloroacetic acid (TCA) soluble peptides, and muscle microstructure. Results showed that P. psychrophila and S. putrefaciens exhibited a strong capacity for decomposing the fish protein, and the deterioration of fish flesh texture was primarily attributed to P. psychrophila. The genes from SSOs associated with the production of proteases were identified by whole genome sequencing and serine protease may be the primary enzyme secreted by SSOs involved in the degradation of fish protein. Therefore, the present study has shed light on the mechanisms of protein degradation induced by SSOs, thereby offering valuable insights for the development of effective quality control strategies.

MassArray Genotyping as a Selection Tool for Extending the Shelf-Life of Fresh Gilthead Sea Bream and European Seabass

In modern aquaculture, genomics-driven breeding programs have emerged as powerful tools for optimizing fish quality. This study focused on two emblematic Mediterranean fish species, the European seabass (Dicentrarchus labrax) and the gilthead sea bream (Sparus aurata), with a primary aim of exploring the genetic basis of white muscle/fillet degradation in fresh fish following harvest. We identified 57 and 44 missense SNPs in gilthead sea bream and European seabass, respectively, located within genes encoding for endogenous proteases responsible for fillet quality. These SNPs were cherry-picked based on their strategic location within the catalytic/regulatory domains of endogenous proteases that are expressed in the white muscle. Using MassArray technology, we successfully associated differentiated enzymatic activity of those endogenous proteases post-harvest as a phenotypic trait with genetic polymorphism of six SNPs in gilthead sea bream and nine in European seabass. These findings can be valuable attributes in selective breeding programs toward the extension of freshness and shelf life of these species. The integration of MassArray technology into breeding programs offers a cost-effective strategy for harnessing the potential of these genetic variants to enhance the overall quality of the final product. Recognizing that fresh fish perishability is a challenge, extending shelf-life is pivotal in reducing losses and production costs.

Gelation characteristics of partially purified myofibrillar proteins extracted from commercially harvested Indian mackerel and threadfin bream

Gelling behaviors of partially purified myofibrillar proteins (PPMP) extracted from Indian mackerel (IM) and threadfin bream (TB) as a function of heating temperatures (20-75°C) were comparatively studied. PPMP obtained from IM (IM-MP) showed lower turbidity and surface hydrophobicity as compared to those extracted from TB (TB-MP). Moreover, lower disulfide bond content was noticed in IM-MP (7.7-9.46 mol/106  g protein) as compared to TB-MP (10.99-13.95 mol/106  g protein) during the heating process. There was no major difference in the amino acid profile noticed between PPMP from both the species, except lysine and glutamine contents, which were higher in TB-MP. Structural analysis, FTIR spectra, amide I band, and fluorescence intensity substantiated those changes. The protein pattern also revealed autolysis of IM-MP. The transmission analysis also showed lower aggregation and crosslinking ability of IM-MP than TB-MP. Therefore, poorer gelling behavior of IM-MP reconfirmed the inferior gel property of surimi gel from IM to gel from TB. Potential development is still required for the improvement of the gel properties of dark-fleshed fish surimi such as IM. PRACTICAL APPLICATION: Indian mackerel (IM) is an abundant and widely captured fish species. Due to overexploitation of lean fish, pelagic fish could be explored as a potential raw material for surimi production. However, poor gelling properties of IM limit its use in the surimi industry. This study provides an insight into the gelling behavior of myofibrillar proteins from IM during the gelation process in comparison with the lean fish (threadfin bream). Overall, structural and rheological changes of myofibrillar proteins play a role in gelation, thus affecting gel properties between two species. Further improvement of the gel of IM is still required.

Quality Evaluation of Mackerel Fillets Stored under Different Conditions by Hyperspectral Imaging Analysis

This study was designed to compare the quality changes in mackerel fillets stored under different conditions by using hyperspectral imaging (HSI) techniques. Fillets packaged in vacuum were stored for six days under five different conditions: refrigerated at 4°C (R group); iced at 5±3°C (I group); kept at an ambient of 17±2°C (A group); frozen at -18°C for 24 h and thawed in a refrigerator at 4°C for 5 h on the sampling day (FTR group); FTR thawed in tap water instead of thawing in a refrigerator (FTW group). The FTR group had the lowest total bacterial count, drip loss, 2-thiobarbituric acid reactive substances, volatile basic nitrogen, and texture profile analysis values among groups during the entire storage period (p<0.05). Scanning electron microscopy revealed that the FTR group had less damage, while the other groups had shrunken muscle tissues. HSI integrated with the partial least squares model yielded reliable and efficient results, with high R2cv values, for several quality parameters of the mackerel fillets. Overall, the FTR group, involving freezing and thawing in a refrigerator, appears to be the most favorable option for maintaining the quality of mackerel fillets, which could be practically implemented in the industry. HSI is a suitable and effective technique for determining the quality of mackerel fillets stored under different conditions.

Mechanism study of the gel-forming ability of heat-induced gel from Peruvian hake (Merluccius gayi peruanus) surimi

The commercial value of Peruvian hake (Merluccius gayi peruanus) meat is low because of its soft texture. This study investigated the major factor contributing to the gel-forming ability of Peruvian hake surimi by comparing the effects of endogenous protease activity and parasitic infection. Heat-induced gels could not be obtained at 50 °C-90 °C. Surimi with severe parasitic infection showed a stronger gel-forming ability. The endogenous protease activities were the main factor influencing the Peruvian hake meat proteolysis and contributed to the low gel-forming ability, rather than parasitic infection. Specifically, endogenous cysteine proteases played an essential role in protein degradation and low gel-forming ability. Moreover, endogenous transglutaminase was also shown to be involved in the gel-forming ability upon heating at 40 °C. These results suggested that Peruvian hake meat could be used as a raw material of frozen surimi for fish gel by inhibiting the activity of endogenous proteases.

Unrinsed Nemipterus virgatus surimi provides more nutrients than rinsed surimi and helps recover immunosuppressed mice treated with cyclophosphamide

BACKGROUND

The rinsing process in the production of surimi can cause the loss of some important nutrients. To investigate the differences in nutritional properties between rinsed surimi (RS) and unrinsed surimi (US), this study compared the elemental composition, amino acid composition, fatty acid composition, proteomics, and an immunosuppression mouse model of surimi before and after rinsing, and analyzed the nutritional and immunological properties of RS and US.

RESULTS

The results showed that the protein, fat, and ash contents of RS were decreased compared with those of US; specifically, the contents of essential amino acids, semi-essential amino acids, non-essential amino acids, saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids were decreased. In the non-labeled quantitative proteomics analysis, three high-abundance quantifiable protein contents and 68 low-abundance quantifiable protein contents were found in RS (P-values < 0.05, ratio > 2). Immune function experiments in mice revealed that both RS and US contributed to the recovery of immunity in immunocompromised mice. The effect of US was better than that of RS.

CONCLUSION

The rinsing process in surimi processing leads to the loss of nutrients in surimi. US promotes the recovery of immunity in immunocompromised mice more effectively than RS. © 2023 Society of Chemical Industry.

The Effect of Sodium Bicarbonate Injection on the Physico-Chemical Quality of Post-Harvest Trout

The muscle hardness of fish is an important parameter associated with meat quality, and the post-mortem decrease in the pH of fish tissue pH affects its physical properties. We hypothesized that maintaining a high pH in fish tissue after death would prevent protein denaturation and consequent textural deterioration. This study aimed to determine the effectiveness of sodium bicarbonate (SBC) injections in preventing tissue softening caused by low pH after death in trout. We injected varying molar concentrations of SBC in rainbow trout (Oncorhynchus mykiss; 0 M, 0.5 M, 0.75 M, and 1 M) after harvest, and the product quality was assessed at 0, 24, 48, 72, and 96 h of ice storage. Quality was evaluated using proximate analyses for color, pH, water holding capacity (WHC), texture profile, and rigor index. The 0 M group had the lowest pH, and the 0.75 M group had the highest pH at all time points during storage. We observed improved tissue texture during storage in fish treated with 0.75 and 1 M SBC. The texture profile analysis showed higher hardness, frangibility, and stickiness in the tail than in the other regions. These varying results can be explained by significant differences between parts of the fish and sampling point selection. We also observed the highest pH and WHC values in the groups injected with 0.75 and 1 M SBC during storage.

Characteristics of the Intestine Extracts and Their Effect on the Crude Collagen Fibers of the Body Wall from Sea Cucumber Apostichopus japonicus

Sea cucumbers Apostichopus japonicus will vomit their intestines during certain stimulations, and the collagen of the body wall will then be degraded. To define the effect of the sea cucumber intestine extracts on the body wall, the intestinal extracts and crude collagen fibers (CCF) of sea cucumber A. japonicus were prepared. According to the gelatin zymography, the type of endogenous enzymes in intestinal extracts were mainly serine endopeptidases with optimal activities at pH 9.0 and 40 °C. According to the rheology results, the viscosity of 3% CCF decreased from 32.7 Pa·s to 5.3 Pa·s by adding intestine extracts. The serine protease inhibitor phenylmethanesulfonyl fluoride inhibited the activity of intestinal extracts and increased the viscosity of collagen fibers to 25.7 Pa·s. The results proved that serine protease in the intestinal extracts participated in the process of body wall softening in sea cucumbers.

Ethanolic Extract of Duea Ching Fruit: Extraction, Characterization and Its Effect on the Properties and Storage Stability of Sardine Surimi Gel

The quality of surimi gel can be improved using protein cross-linkers, especially from plant extracts. Apart from the presence of phenolic compounds, Duea ching fruit is rich in calcium, which can activate indigenous transglutaminase or form the salt bridge between protein chains. Its extract can serve as a potential additive for surimi. The effect of different media for the extraction of Duea ching was studied and the use of the extract in sardine surimi gel was also investigated. The Duea ching fruit extract (DCE) was prepared using distilled water and ethanol (EtOH) at varying concentrations. The DCE prepared using 60% EtOH (DCE-60) had the highest antioxidant activity and total phenolic content. When DCE-60 (0-0.125%; w/w) was added to the sardine surimi gel, the breaking force (BF), deformation (DF) and water holding capacity (WHC) of the gel upsurged and the highest values were attained with the 0.05% DCE-60 addition (p < 0.05). However, the whiteness of the gel decreased when DCE-60 levels were augmented. The gel containing 0.05% DCE-60, namely D60-0.05, showed a denser network and had a higher overall likeness score than the control. When the D60-0.05 gel was packed in air, under vacuum or modified atmospheric packaging and stored at 4 °C, BF, DF, WHC and whiteness gradually decreased throughout 12 days of storage. However, the D60-0.05 gel sample showed lower deterioration than the control, regardless of the packaging. Moreover, the gel packaged under vacuum conditions showed the lowest reduction in properties throughout the storage than those packaged with another two conditions. Thus, the incorporation of 0.05% DCE-60 could improve the properties of sardine surimi gel and the deterioration of the resulting gel was retarded when stored at 4 °C under vacuum packaging conditions.

Inhibitory effect of pre-gelatinized dialdehyde starch on heat-induced deterioration of sea cucumber

BACKGROUND

This study sought to investigate the inhibitory effect of pre-gelatinized dialdehyde starch (P-DAS) on the deterioration of sea cucumber during high-temperature sterilization.

RESULTS

It was found that pre-gelatinization reduced crystallinity and average molecular weight of dialdehyde starch (DAS), exposed free aldehyde groups, improved the solubility, and unified the particle sizes. According to the texture profiles of sea cucumber, the crosslinking power of P-DAS was higher than that of DAS. The results of free amino content, total soluble substance, water retention, water distribution, relaxation time and scanning electron microscopy all showed that the crosslinking effect was dose-dependent on crosslinking agent.

CONCLUSION

These results have proved that large molecules such as P-DAS, when properly handled, could also efficiently enter collagen hydrogels and perform crosslinking, providing reference for the development of new protein food stabilizing agents. © 2022 Society of Chemical Industry.

Marine enzymes: Classification and application in various industries

Oceans are regarded as a plentiful and sustainable source of biological compounds. Enzymes are a group of marine biomaterials that have recently drawn more attention because they are produced in harsh environmental conditions such as high salinity, extensive pH, a wide temperature range, and high pressure. Hence, marine-derived enzymes are capable of exhibiting remarkable properties due to their unique composition. In this review, we overviewed and discussed characteristics of marine enzymes as well as the sources of marine enzymes, ranging from primitive organisms to vertebrates, and presented the importance, advantages, and challenges of using marine enzymes with a summary of their applications in a variety of industries. Current biotechnological advancements need the study of novel marine enzymes that could be applied in a variety of ways. Resources of marine enzyme can benefit greatly for biotechnological applications duo to their biocompatible, ecofriendly and high effectiveness. It is beneficial to use the unique characteristics offered by marine enzymes to either develop new processes and products or improve existing ones. As a result, marine-derived enzymes have promising potential and are an excellent candidate for a variety of biotechnology applications and a future rise in the use of marine enzymes is to be anticipated.

Polyphenol extracts from Ascophyllum nodosum protected sea cucumber (Apostichopus japonicas) body wall against thermal degradation during tenderization

To retard the protein degradation during sea cucumber processing, polyphenol extracts from Ascophyllum nodosum (PhE) was used as a potential antioxidant to maintain the structural integrity of sea cucumber body wall. Accordingly, the protection effects of PhE (0, 0.5, 1.0 and 1.5 mg PhE/g SFBW) against thermal degradation of the solid fragments of body wall (SFBW) have been investigated in order to evaluate their impact on the oxidation level and structural changes. Electronic Spin Resonance results showed that PhE could significantly inhibit the occurrence of oxidation by scavenging the free radicals. The effect of PhE on chemical analysis of soluble matters in SFBW was characterized by SDS-PAGE and HPLC. Compared with thermally treated SFBW, samples with PhE presented a decrease in protein dissolution. Thermal treatment resulted in the disintegration of collagen fibrils and fibril bundles in SFBW samples, while the density of collagen fibrils was increased, and the porosity decreased in samples with PhE. The results of FTIR and intrinsic tryptophan fluorescence confirmed that the structures of SFBW were modified by PhE. Besides, the denaturing temperature and decomposition temperature were both improved with the addition of PhE. These results suggested that PhE appeared to have a positive effect on lowering oxidation and improving thermostability and structural stability of SFBW, which could provide a theoretical basis for protecting sea cucumber body wall against degradation during thermal tenderization.

Use of Tuna Visceral Pepsin in Combination with Trypsin as Digestion Aid: Enhanced Protein Hydrolysis and Bioavailability

Freeze-dried tuna pepsin powder (TPP) was prepared using maltodextrin (10%) and trehalose (5%), while trypsin-loaded beads (TLB) with 5% glycerol were obtained via chitosan/alginate ionotropic gelation. The storage stability of TPP and TLB and their proteolytic activity toward red kidney bean protein (RKB), threadfin bream surimi (TBS) and egg white protein (EWP) in varying simulated in vitro gastrointestinal (GI) tract conditions were studied. The intestinal transepithelial transportation of generated peptides was also carried out through Caco-2 cell monolayers after the cytotoxicity test. Enzyme activity was dropped when TPP and TLB in blister packs were kept for 10 weeks of storage at room (28 °C) and refrigerated (4 °C) temperatures. TPP and TLB at a level of 50% (w/w of proteins) effectively hydrolyzed RKB, TBS and EWP in a simulated in vitro GI tract, as indicated by marked protein degradation and increased degree of hydrolysis. Some peptides generated after GI digestion could transport through Caco-2 cell monolayers. Those peptides had different molecular size distribution and antioxidant activities. The highest antioxidant activity was observed for RKB hydrolysate after passing through the Caco-2 cell monolayer. Therefore, TPP and TLB from skipjack tuna viscera could potentially be used for enzyme supplementation to help digest food proteins. Food-derived bioactive peptides generated after GI digestion could assist in improving human health due to their antioxidant activity.

Effects of Storage Method on the Quality of Processed Sea Cucumbers (Apostichopus japonicus)

This research aimed to establish an effective storage method to maintain the quality of processed sea cucumbers. In this study, sea cucumbers were stored by various methods including the storage of live sea cucumbers (seawater treatment, oxygen treatment, and ascorbic acid treatment) and the storage of dead sea cucumbers (frozen treatment). The sea cucumber quality was monitored after storage and boiling. The weightlessness rate and WHC of the frozen group increased to 86.96% ± 0.83% and 93.29% ± 0.32%, respectively. Frozen sea cucumbers shrunk with the meat's textural properties deteriorated. During the live sea cucumber storage, the tissue protein degraded from day 3 to day 7 which led to the promotion of TVB-N. Among these, the oxygen group showed the smallest TVB-N increase from day 0 (3.78 ± 0.60 mg 100 g^-1) to day 7 (10.40 ± 0.12 mg 100 g^-1). The oxygen group exhibited the most moderate change in weightlessness rate (4.24% ± 0.45%) and the most moderate texture parameters decline, such as the hardness of 32.52%, chewiness of 78.98 ± 5.10 N, and adhesion of 0.84 ± 0.00. The oxygen method showed the best condition of sea cucumber after 5 days of storage.

Effects of Replacing Fishmeal with Defatted Black Soldier Fly (Hermetia illucens Linnaeus) Larvae Meal in Japanese Eel (Anguilla japonica) Diet on Growth Performance, Fillet Texture, Serum Biochemical Parameters, and Intestinal Histomorphology

An 8-week feeding trial was conducted to investigate the effects of replacing fishmeal with defatted black soldier fly larvae meal (DBSFLM) in the diets of Japanese eel on their growth performance, fillet texture, serum biochemical parameters, and intestinal histomorphology. Six isoproteic (520 g kg^-1), isolipidic (80 g kg^-1), and isoenergetic (15 MJ kg^-1) diets were formulated with fishmeal replacement levels of 0% (R0), 15% (R15), 30% (R30), 45% (R45), 60% (R60), and 75% (R75). The growth performance, feed utilization efficiency, survival rate, serum liver function enzymes, antioxidant ability, and lysozyme activity of fish were not affected (P > 0.05) by DBSFLM. However, the crude protein and cohesiveness of the fillet in groups R60 and R75 significantly decreased, and the fillet hardness significantly increased (P < 0.05). Additionally, the intestinal villus length significantly decreased in the R75 group, and the goblet cell densities were significantly lower in the R45, R60, and R75 groups (P < 0.05). Overall, high levels of DBSFLM did not affect growth performance and serum biochemical parameters but significantly altered fillet proximate composition and texture and intestinal histomorphology (P < 0.05). The optimal fishmeal replacement level is 30% with 184 g kg^-1 DBSFLM.

Metabolomics insights into the potential of encapsulated essential oils as multifunctional food additives

Growing consumer concern about foodborne disease outbreaks and health risks associated with chemical additives has propelled the usage of essential oils (EOs) as novel food additives, but are limited by instability. In this regard, a series of EOs nano/micro-capsules have been widely used to enhance their stability and improve food quality. However, classical food quality assessment methods are insufficient to fully characterize the effects of encapsulated EOs on food properties, including physical, biochemical, organoleptic, and microbial changes. Recently, the rapid development of high-throughput sequencing is accelerating the application of metabolomics in food safety and quality analysis. This review seeks to present the most recent achievements in the application of non-targeted metabolomics to identify and quantify the overall metabolite profile associated with food quality, which can guide the development of emerging food preservation technologies. The scientific findings confirm that metabolomics opens up exciting prospects for biomarker screening in food preservation and contributes to an in-depth understanding of the mechanisms of action (MoA) of EOs. Future research should focus on constructing food quality assessment criteria based on multi-omics technologies, which will drive the standardization and commercialization of EOs for food industry applications.

Research progress on quality deterioration mechanism and control technology of frozen muscle foods

Freezing can prolong the shelf life of muscle foods and is widely used in their preservation. However, inevitable quality deterioration can occur during freezing, frozen storage, and thawing. This review explores the eating quality deterioration characteristics (color, water holding capacity, tenderness, and flavor) and mechanisms (irregular ice crystals, oxidation, and hydrolysis of lipids and proteins) of frozen muscle foods. It also summarizes and classifies the novel physical-field-assisted-freezing technologies (high-pressure, ultrasound, and electromagnetic) and bioactive antifreeze (ice nucleation proteins, antifreeze proteins, natural deep eutectic solvents, carbohydrate, polyphenol, phosphate, and protein hydrolysates), regulating the dynamic process from water to ice. Moreover, some novel thermal and nonthermal thawing technologies to resolve the loss of water and nutrients caused by traditional thawing methods were also reviewed. We concluded that the physical damage caused by ice crystals was the primary reason for the deterioration in eating quality, and these novel techniques promoted the eating quality of frozen muscle foods under proper conditions, including appropriate parameters (power, time, and intermittent mode mentioned in ultrasound-assisted techniques; pressure involved in high-pressure-assisted techniques; and field strength involved in electromagnetic-assisted techniques) and the amounts of bioactive antifreeze. To obtain better quality frozen muscle foods, more efficient technologies and substances must be developed. The synergy of novel freezing/thawing technology may be more effective than individual applications. This knowledge may help improve the eating quality of frozen muscle foods.

Improving the Gel Quality of Threadfin Bream (Nemipterus spp.) Surimi Using Salted Duck Egg White Powder

The effect of salted duck egg white powder (SDEWP) as a source of salt at different salt equivalent (SE) levels (0−2.5% SE) on gel qualities and texture properties of threadfin bream surimi was investigated. SDEWP possessed a high protein (64.59%) and salt (34.86%) concentration. The breaking force of surimi gel increased by the amount of SDEWP (p < 0.05). The addition of SDEWP up to 1.5% SE into the surimi gel has significantly increased the deformation (13.8%) and decreased the expressible moisture content (38.5%). Hardness, gumminess, and chewiness were augmented as higher levels of SDEWP were added, whereas cohesiveness decreased when the SDEWP above 1.5% SE was used. The incorporation of SDEWP had no significant effect on the springiness (p < 0.05). Less proteolytic degradation was observed in the surimi gel fortified with SDEWP. A higher amount of added SDEWP enhanced the whiteness of the surimi gel (p < 0.05). A denser and more ordered gel network was attained when SDEWP with 1.5% SE was added. SDEWP could be exploited as a source for salt and non-fish proteins in threadfin bream surimi, in which SDEWP containing 1.5% SE could significantly improve the quality of surimi gel.

Effects of Ultrasound-Assisted Immersion Freezing on the Protein Structure, Physicochemical Properties and Muscle Quality of the Bay Scallop (Argopecten irradians) during Frozen Storage

In this study, the comparison effects of ultrasound-assisted immersion freezing (UIF) at different ultrasonic power, immersion freezing (IF), and air freezing (AF) on the protein thermal stability, protein structure, and physicochemical properties of adductor muscle of scallop (Argopecten irradians) (AMS) during frozen storage were investigated. Principal component analysis and the Taylor diagram were used to comprehensively analyze all the indicators tested. The results showed that the UIF at 150 W (UIF-150) treatment was the most effective way to delay the quality deterioration of AMS during 90-day frozen storage. This was mainly because, compared to AF and IF treatments, UIF-150 treatment more effectively minimized the changes in the primary, secondary and tertiary structures of myofibrillar proteins, and it preserved the protein thermal stability of AMS by producing small and regular ice crystals in the AMS tissue during the freezing process. Moreover, the results of physicochemical properties indicated that UIF-150 treatment significantly inhibited the fat oxidation and microbiological activities of frozen AMS, and it finally maintained the microstructure and texture of AMS during frozen storage. Overall, UIF-150 has potential industrial application prospects in the rapid freezing and quality preservation of scallops.

The role of cathepsin L on structural changes of collagen fibers involved in textural deterioration of chilled grass carp (Ctenopharyngodon idella) fillets

BACKGROUND

Textural deterioration is a serious problem in chilled fish flesh. Cysteine proteinases are proposed to participate in disintegration of collagen fibers during this process, while its mechanism remains elusive. In the present study, a cysteine proteinase was purified from grass carp muscle and identified by mass spectrometry, and its effect on structural changes of collagen fibers was investigated.

RESULTS

During storage at 4 °C, cysteine proteinase activity in fillets increased to 1.53-fold at day 5 and maintained a high level later, and this variable was related to a decline in shear force and an increase in drip loss. A 29 kDa cysteine proteinase was purified through ammonium sulfate precipitation and column chromatography, and identified as cathepsin L. Cathepsin L caused collagen fibers to partly disintegrate into fibril bundles and individual fibrils at 48 h, while the triple helical structure of collagen molecules remained stable. Release of soluble proteins and glycosaminoglycans from cathepsin L-treated collagen fibers was time dependent, coinciding with a release of 4.12 ± 0.13% and 8.57 ± 0.03% at 48 h respectively. However, 0.85 ± 0.02% of hydroxyproline was freed from cathepsin L-treated collagen fibers at 48 h. Furthermore, scanning electron microscopy revealed that the inhibitory effect of cathepsin L could retard the destruction of intramuscular connective tissues (IMCTs).

CONCLUSION

These results indicated that cathepsin L might be involved in collagen fiber breakdown by degrading collagen-associated proteoglycans during textural deterioration of grass carp. © 2022 Society of Chemical Industry.

Effect of sodium bicarbonate on textural properties and acceptability of gel from unwashed Asian sea bass mince

Asian sea bass mince gels having different adjusted moisture/water content (80 and 85%; w/w) were prepared with addition of sodium bicarbonate (SB) at various concentrations (0, 0.05 and 0.1%; w/w). Fish mince gels of 80% water content added with 0.05 and 0.1% SB (G80-0.05 and G80-0.1, respectively) had the highest increase (135-139%) in breaking force (BrF) than the respective control gel (G80) (P < 0.05). For gel with 85% water content, a lower increase (17-28%) in BrF was found with the addition of SB as compared to their corresponding control (G85). Whiteness of all samples was continuously decreased with increasing amount of SB, however the water holding capacity was increased drastically with augmenting levels of SB, regardless of the water content (P < 0.05). A loss in the elasticity of gel was attained with the addition of SB as indicated by decreasing storage modulus. A finer and more compact network was detected in a gel containing SB, irrespective of water content. Based on sensory scores, gel having 85% water content added with 0.05 and 0.1% SB had similar acceptability to the control gel (G80) containing 80% water content (commercial level). Therefore, SB at the appropriate level could improve the gelling properties with higher water holding ability of the mince gel with high acceptability.

Resource recovery from fish waste: Prospects and the usage of intensified extraction technologies

Globally, the valorization of fish biowaste as a feedstock to recover valuable components is an emerging research and commercial interest area to achieve the SDG goals by 2030. Fish waste-derived biomolecules are increasingly finding diverse applications in food and other biotechnological fields due to their excellent chemical, structural and functional properties. The focus of this review is to highlight the conventional valorization routes and recent advancements in extraction technologies for resource recovery applications, primarily focusing on green processes. Biointensified processes involving ultrasound, microwave, sub- and supercritical fluids, pulsed electric field, high-pressure processing, and cold plasma are extensively explored as sustainable technologies for valorizing fish discards and found numerous applications in the production of functional and commercially important biomaterials. With challenges in recovering intracellular bioactive compounds, selectivity, and energy requirement concerns, conventional approaches are being relooked continuously in the quest for process intensification and sustainable production practices. Nonetheless, in the context of 'zero waste' and 'biorefinery for high-value compounds', there is immense scope for technological upgradation in these emerging alternative approaches. This work details such attempts, providing insights into the immense untapped potential in this sector.

Rapid quality deterioration of harpiosquillid mantis shrimp (Harpiosquilla raphidea) during iced storage

Changes in physicochemical, textural, microbial, and sensory quality of harpiosquillid mantis shrimp (Harpiosquilla raphidea) (HMS) during 10 days of iced storage were studied. Weight and cooking losses were increased during storage (p < 0.05). Drastic decrease in myosin heavy chain was found after 2 days of storage. Increases in total volatile basic nitrogen, trimethylamine, peroxide value, and thiobarbituric acid reactive substances with coincidentally augmented pH were found during the storage (p < 0.05). For microbiological analyses, total viable counts exceeded the limit at day 6. Melanosis score increased with a decreased L* value as storage time increased. Rapid decreases in hardness, springiness, cohesiveness, gumminess, and chewiness were associated with pasty and softened texture, which was supported by looser arrangement of muscle fiber along with gapping. This was reconfirmed by lowered shear force. Based on the quality evaluation, HMS could maintain the freshness and quality for not longer than 2 days in ice.

Asian Carp, an Alternative Material for Surimi Production: Progress and Future

Asian carp is a general designation for grass carp, silver carp, bighead carp, and black carp. These fish species belong to the family Cyprinidae. In 2018, more than 18.5 million tons of Asian carp were produced globally. Asian carp can be used for producing surimi, a stabilized myofibrillar protein concentrate that can be made into a wide variety of products such as imitation crab sticks, fish balls, fish cakes, fish tofu, and fish sausage. Surimi is usually made from marine fish, but Asian carp have been widely used for surimi production in China. The quality of surimi is affected by various factors, including the processing methods and food additives, such as polysaccharides, protein, salt, and cryoprotectant. With an impending shortage of marine fish due to overfishing and depletion of fish stocks, Asian carp have a potential to serve as an alternative raw material for surimi products thanks to their high abundancy, less emissions of greenhouse gases from farming, desirable flesh color, and sufficient gel forming ability. The utilization of Asian carp in surimi production could also contribute to relieving the overflow of Asian carp in the United States.

Changes in Biochemical Properties and Activity of Trypsin-like Protease (Litopenaeus vannamei) Treated by Atmospheric Cold Plasma (ACP)

The changes in the functional properties of trypsin from shrimps (Litopenaeus vannamei) after, Atmospheric Cold Plasma (ACP) treatments, have been evaluated in terms of enzyme inactivation, surface hydrophobicity, secondary structure, fluorescence intensity, and particle size distribution. Different exposure voltages of 10, 20, 30, 40, and 50 kV at various treatment times (1, 2, 3, and 4 min) have been employed, in a separate assay. The results showed that trypsin-like protease activity decreased (by about 50%), and the kinetic constants K_m value increased, while the k_cat value decreased. Surface hydrophobicity and fluorescence intensity revealed a significant increase compared to the control sample. A high degree of protein degradation has been noticed by SDS-PAGE analysis. In addition, circular dichroism indicated that random coil and α-helix contents declined while β-turn and β-sheet contents have raised. A sharp drop in the particle size was observed with increasing the treatment voltage from 0 to 40 kV for 4 min, and the corresponding peak reached the minimum of 531.2 nm. Summing up the results, it can be concluded that the ACP technique effectively affects the activity of trypsin-like protease, which in terms enhances the quality of dietary protein.

Preparation of Linalool/Polycaprolactone Coaxial Electrospinning Film and Application in Preserving Salmon Slices

A linalool/polycaprolactone (LL/PCL) antibacterial film was prepared by using a coaxial electrospinning process, and its physical and chemical properties were characterized. The antibacterial film was formed into an active antibacterial gasket, and its effect on salmon preservation was analyzed. The results show that the LL/PCL nanofiber membrane had a well-developed microstructure, and the fiber surface was smooth and uniform. The diameter of the fibers in the PCL membrane without the core material (linalool) was 113.92 ± 23.74 nm. In contrast, the diameter of the coaxial nanofiber membrane with linalool increased, and the diameter of the LL/PCL membranes with 20% and 40% linalool was 220.62 ± 44.01 and 232.22 ± 56.27 nm, respectively. The hydrophobicity and water vapor permeability were enhanced, whereas the tensile strength and elongation at break decreased slightly, while the thermal stability did not differ significantly with the incorporation of linalool. Analysis of the sustained release of linalool showed that the LL/PCL coaxial fiber membranes could release linalool into the reaction system for a long time. The LL/PCL nanofiber film was used to create an antibacterial active gasket for salmon preservation experiments. Sensory evaluation and analyses of the total bacterial count, total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), pH, texture (hardness, elasticity, chewiness, and viscoelasticity), water distribution change, and aroma using an electronic nose were used to determine the quality of salmon. It was found that food-grade tinfoil and the PCL gasket had no significant effect on the freshness of salmon, while the active antibacterial gasket samples containing linalool could decrease the rate of decay salmon and effectively prolong the shelf-life of salmon by releasing linalool.

Assessment of gelatinolytic proteinases in chilled grass carp (Ctenopharyngodon idellus) fillets: characterization and contribution to texture softening

BACKGROUND

Texture softening is always a problem during chilling of grass carp fillets. To solve this problem and provide for better quality of flesh, understanding the mechanism of softening is necessary. Gelatinolytic proteinases are suspected to play an essential role in the disintegration of collagen in softening of fish flesh. In the present study, the types and contribution of gelatinolytic proteinases in chilled fillets were investigated.

RESULTS

Four active bands (G1, 250 kDa; G2, 68 kDa; G3, 66 kDa; G4, 29 kDa) of gelatinolytic proteinases were identified in grass carp fillets by gelatin zymography. The effect of inhibitors and metal ions revealed that G1 was possibly a serine proteinase, G2 and G3 were calcium-dependent metalloproteinases and G4 was a cysteine proteinase. The effect of the inhibitors phenylmethanesulfonyl fluoride (PMSF), l-3-carboxy-trans-2,3-epoxy-propionyl-l-leucine-4-guanidinobutylamide (E-64) and 1,10-phenanthroline (Phen) on chilled fillets revealed that gelatinolytic proteinase activities were significantly suppressed. Collagen solubility indicated that metalloproteinase and serine proteinase played critical roles in collagen breakdown during the first 3 days, and cysteine proteinase revealed its effect after 3 days. Meanwhile, during chilled storage for 11 days, the final values of shear force increased 19.68% and 24.33% in PMSF and E-64 treatments when compared to control fillets respectively, whereas the increase after Phen treatment was 49.89%.

CONCLUSION

Our study concluded that the disintegration of collagen in post-mortem softening of grass carp fillets was mainly mediated by metalloproteinase and to a lesser extent by serine proteinase and cysteine proteinase. © 2021 Society of Chemical Industry.

Determination of protease inhibitors, glycinin, and beta-conglycinin in soybeans and their relationships

In order to search for suitable soybean varieties for different applications, the protein contents of Kunitz trypsin inhibitor (KTI), Bowman-Birk trypsin inhibitor (BBI), glycinin (11S), and β-conglycinin (7S) of 93 soybean samples from different sources and harvest years were quantified by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Meanwhile, the protease inhibitory activities against trypsin and chymotrypsin were determined. Results showed that the individual protein contents and trypsin inhibitor activities differed significantly (p < 0.05) among soybean samples. KTI contents ranged from 5.25 to 14.60 mg·g-1 ; BBI contents ranged from 1.81 to 5.74 mg·g-1 ; 11S varied from 13.65% to 48.55% and 7S varied from 15.68% to 42.15% of total soluble protein; trypsin and chymotrypsin inhibitory activities were 8.93-20.95 mg TI·g-1 and 4.18 -12.79 mg CI·g-1 , respectively. Excellent linear relationships existed between trypsin inhibitor contents and their activities. The regression equations offer a rapid method for estimating the activity of KTI or BBI in raw soybeans. PRACTICAL APPLICATION: The regression equations established based on a large number of soybean varieties offered a rapid method to estimate the activity of trypsin inhibitors. The data presented here provided useful information for the food industry or breeders to select soybean varieties with different inhibitory activities or protein contents for different food processing applications.

Development of a High-Yield Isolation Protocol Optimized for the Retrieval of Active Muscle Satellite Cells from Mouse Skeletal Muscle Tissue

Background and Objectives

Difficulties often encountered in separating and purifying active muscle satellite cells (MSCs) from skeletal muscle tissues have limited the supply of cells for muscle therapy and artificial meat production. Here, we report an effective isolation protocol to economically and conveniently retrieve active MSCs from skeletal muscle tissues in mice.

Methods and Results

We optimized an enzyme-based tissue digestion protocol for isolating skeletal muscle-derived primary cell population having a large number of active MSCs and described a method of differential plating (DP) for improving purity of active MSCs from skeletal muscle-derived primary cell population. Then, the age of the mouse appropriate to the isolation of a large number of active MSCs was elucidated. The best isolation yield of active MSCs from mouse skeletal muscle tissues was induced by the application of DP method to the primary cell population harvested from skeletal muscle tissues of 2-week-old mice digested in 0.2% (w/v) collagenase type II for 30 min at 37℃ and then in 0.1% (w/v) pronase for 5 min at 37℃.

Conclusions

The protocol we developed not only facilitates the isolation of MSCs but also maximizes the retrieval of active MSCs. Our expectation is that this protocol will contribute to the development of original technologies essential for muscle therapy and artificial meat industrialization in the future.

Combined effects of ultrasound and antioxidants on the quality maintenance of bay scallop (Argopecten irradians) adductor muscles during cold storage

The combined effects of ultrasound and the antioxidants of bamboo leaves (AOB) on the quality maintenance of the adductor muscle of scallops (AMSs) during cold storage was investigated. Ultrasound power at 350 W coupled with AOB solution (2% w/v) (UAOB-350) was applied to treat the AMSs according to Taylor diagram analysis. The microstructure, oxidative changes (lipid and protein oxidation), total numbers of colonies, total volatile basic nitrogen, and texture of the AMSs during 6 days of cold storage were analysed. The results indicated that UAOB-350 treatment could effectively retard protein and lipid oxidation and bacterial growth and maintain better microstructure and texture characteristics than AOB solution treatment alone, prolonging the shelf life of the AMSs by 2 days during storage at 4 °C. These results indicate that the UAOB-350 combination method has promising potential to maintain the quality and extend the shelf life of AMSs during cold storage.

Vacuum impregnation of chitosan coating combined with water-soluble polyphenol extracts on sensory, physical state, microbiota composition and quality of refrigerated grass carp slices

Herein, the effects of chitosan (CH) coating with different water-soluble polyphenol extracts (pomegranate peel (PPE), grape seed (GSE) and green tea (GTE)) through vacuum impregnation on the quality retention and microflora of refrigerated grass carp fillets were studied. Generally, the quality degradation of carp fillets was remarkably alleviated using coatings when compared to the control. As suggested by microbial enumeration and high-throughput sequencing, protective coatings were conductive to inhibit bacteria growth, especially spoilage bacteria of Pseudomonas. As a result, the indicator related to bacteria such as total volatile basic nitrogen (TVB-N) and K value had lower levels in coating groups than that in control. In addition, coating also slowed down the deterioration of physical properties of color, texture and water holding capacity in fillets, giving fillets a better edible quality. By contrast, the fillets treated by composite coatings had better quality during storage when compared to chitosan coating alone, and a relatively good synergistic antibacterial effect between chitosan and extracts was also observed, especially for CH-GTE. Overall, the best performance to inhibit quality deterioration was recorded in CH-GTE, with the lowest values of TVB-N, TBARS, K-value and water loss, and highest values of shear force and sensory preference among groups.

Multifunctional bioactive coatings based on water-soluble chitosan with pomegranate peel extract for fish flesh preservation

This study aimed to reveal the effects of vacuum-impregnated carboxymethyl chitosan (CMCS) coating with pomegranate peel extract (PPE) on quality retention of fish flesh during refrigeration. Herein, CMCS-PPE coating was effective in attenuating quality loss of grass carp fillets. Compared to Control, the levels of drip loss, total volatile base nitrogen, and K value in coated samples were sharply decreased (p < 0.05) by 24.5%, 35.3% and 25.2% on day 9, respectively. Meanwhile, the coating also helped inhibit oxidation, bioamine accumulation, and texture softening in fillets. Moreover, the microbial enumeration was reduced by >1.4 lg cfu/g as compared to Control on day 6 afterward, and high throughput sequencing analysis further showed the active coating contributed to the notable growth suppression of spoilage bacteria like Shewanella. Additionally, the positive effect of the coating scheme was also verified in longsnout catfish and snakehead, further confirming its good applicability for fish flesh preservation.

Reduced Washing Cycle for Sustainable Mackerel (Rastrelliger kanagurta) Surimi Production: Evaluation of Bio-Physico-Chemical, Rheological, and Gel-Forming Properties

Although dark muscle is currently the most important obstacle in marketing high-quality Indian mackerel (Rastrelliger kanagurta) surimi, reducing washing remains a challenge for long-term surimi production from this species. Herein, the impact of washing cycles (one (W1), two (W2), and three (W3) cycles) with a 1:3 mince to water ratio on the bio-physico-chemical properties, rheology, and gelling ability of mackerel surimi was evaluated. The yield, Ca2+-ATPase activity, TCA-soluble peptide, and myoglobin contents of surimi decreased as the number of washing cycles increased, while lipid removal, reactive SH content, and surface hydrophobicity of surimi increased. Surimi generated by W2 and W3 provided the same rheological patterns and Fourier-transform infrared spectroscopy (FTIR) spectra as unwashed mince, with the highest gel strength and whiteness, as well as the lowest expressible drip, thiobarbituric acid reactive substances (TBARS), and fishy odor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated the presence of polymerized proteins stabilized by disulfide and other interactions. Using a scanning electron microscope, several concentrated dense areas and distributed pores generated by myofibrillar proteins gel networks were found. Surimi from W2 and W3 appeared to be of similar overall quality, however W2 had a larger yield. As a result of the evaluation of bio-physico-chemical, rheological, and gel-forming capabilities, as well as product yield, W2 may be the best option for producing high-quality surimi from Indian mackerel in a sustainable manner.