Changes in water-soluble taste compounds of tilapia (Oreochromis niloticus) fillets subjected to different thawing methods during long-term frozen storage.

BACKGROUND: The taste of fish is highly dependent on the composition of free amino acids (FAAs) and nucleotides. The present study aimed to investigate the effect of long-term frozen storage periods (-18 °C, up to 6 months) and thawing methods [water thawing (WT, 25 °C), air thawing (AT, 25 °C), and chilled air thawing (CAT, 4 °C)] on the taste quality of tilapia (Oreochromis niloticus) fillets. RESULTS: The results showed that increase in bitter FAAs of CAT samples was 150.57% at 6 months of storage, which was lower than that of AT and WT. Glycine was the most abundant FAA and CAT maintained the highest sweet FAAs (249.90 mg/100 g). Additionally, the inosine monophosphate (IMP) of CAT samples were 1.18 and 1.09 times higher than that of WT and AT, respectively, at a frozen period of 6 months. In particular, the increase in equivalent umami concentration (EUC) values ranged from 24.25% to 103.16% in the three groups during the first 2 months. Data from principal component analysis (PCA) and orthogonal partial least-squares discrimination analysis (OPLS-DA) indicated that the taste quality was highly correlated with high levels of FAAs, hypoxanthine inosine (HxR) and hypoxanthine (Hx) as the storage time progressed. CONCLUSION: In general, CAT is beneficial in maintaining the taste quality of tilapia fillets during frozen storage, and frozen durations for 2 months enhances the umami flavor. This study provides useful information for the preservation of frozen aquatic products during the storage and thawing, and enrich the theoretical knowledge of the flavor chemistry of fish products. © 2024 Society of Chemical Industry.

Ultrasound-assisted fermentation of Porphyra yezoensis sauce at different growth stages using Lactiplantibacillus plantarum: Metabolic response and biological activity.

This study first employed ultrasonic-assisted fermentation of seaweed foot material with Lactiplantibacillus plantarum to produce Porphyra yezoensis sauce. The aim was to examine L. plantarum's growth and metabolism of nutritional components at different growth stages under low- (133.99 W/L) and high-ultrasonic power densities (169.17 W/L). After 24-h fermentation, L. plantarum exhibited a 21.32 % increase in the sonicated P. yezoensis sauce at 133.99 W/L and the logarithmic growth phase compared to that at 169.17 W/L. In addition, compared to the non-sonicated sauce, total phenolic and flavonoid contents increased by around 58 % and 27 % in sonicated sauce at 133.99 W/L, reaching 92.38 mg GEA/g DW and 111.08 mg RE/g DW, respectively. Principal Component Analysis (PCA) of the evaluation criteria for different fermentation stages under 133.99 W/L power ultrasonication revealed that the P. yezoensis sauce generated more phenolic compounds and exhibited stronger antioxidant capabilities in the sonicated sample at the logarithmic phase of L. plantarum. Compared to the traditional treated P. yezoensis sauce, the content of free amino acids was significantly increased in sonicated sauce, especially for logarithmic phase. Finally, GC-IMS analysis demonstrated that the ultrasonication at logarithmic phase released more volatile compounds compared to the non-sonicated sauce. This led to a reduction in the fishy odour of the Porphyra yezoensis sauce and an improved release of favourable flavour compounds.

Shelf-life extension of soy sauce by using chitosan oligosaccharides combined with tea polyphenols.

Chitosan oligosaccharides (COs) and tea polyphenols (TPs) have antioxidant and antibacterial activities. This study aims to explore the preservative effects of 0.1 % COs alone and combined with 0.08 % TPs on soy sauce during room-temperature storage. Soy sauce treated with 0.1 % COs alone and combined with 0.08 % TPs had lower total bacterial count, Escherichia coli count and pH, and higher amino acid nitrogen and overall likeness score than those of the control group during room-temperature storage. Treatment with 0.1 % COs combined with 0.08 % TPs extended the shelf life of soy sauce by at least 15 months compared with the control group. Results showed 0.1 % COs combined with 0.08 % TPs may be a feasible method to extend the shelf life of soy sauce during room-temperature storage.

Ultrasound-assisted fermentation of ginkgo kernel juice by Lactiplantibacillus plantarum: Microbial response and juice composition development.

This study is aimed to explore the feasibility of ultrasound on enhancing the fermentation properties of ginkgo kernel juice by Lactiplantibacillus plantarum Y2. Specifically, ultrasound at 20 kHz and different intensities (mild ultrasound intensity-84.42 W/L, moderate ultrasound intensity-115.50 W/L, high ultrasound intensity-173.88 W/L) with a pulse mode were applied to facilitate the fermentation process. The number of viable cells of Lactiplantibacillus plantarum Y2 increased by 5.06, 5.05 and 2.19% in the sonicated groups at 173.88, 115.50 and 84.42 W/L, compared with the non-sonicated juice after 24-h fermentation. Furthermore, mild intensity ultrasonication improved the permeability of the cell membrane, which is beneficial for the metabolism of phenolics, amino acids and organic acids. Ultrasonication increased in-vitro antioxidant activity of fermented ginkgo kernel juice by promoting the metabolism of phenolic acids, such as ferulic acid, chlorogenic and caffeic acids. At the end of fermentation, the sonicated group at 84.42 W/L has the maximum consumptions of total sugars and proteins (increased by 12.52 and 18.73%). Moreover, the reduction rate of the poison material 4'-O-methylpyridoxine (MPN) in ginkgo kernel juice increased by more than 16.40% with ultrasound treatment at 173.88 W/L after the fermentation for 48 h. Overall, ultrasound can improve the metabolizations of Lactobacillus plantarum and reduce the toxic substances, which promoted the nutritional value and flavors of ginkgo kernel juice.

The impact of osmotic stresses on the biofilm formation, immunodetection, and morphology of Aeromonas hydrophila.

Aeromonas hydrophila (Ah) is a zoonotic pathogen of great importance to aquaculture and human health. This study systematically evaluated the impact of salinity, sugar, ammonia nitrogen, and nitric nitrogen levels on the fitness of Ah by using Luria-Bertani (LB) broth supplemented with different concentrations of NaCl, sucrose, NH4Cl, urea, NaNO2 or NaNO3. Results showed that the static biofilm formation of Ah was higher at 28 °C compared to 37 °C (P < 0.05). At 28 °C, as the NaCl (>1 %) and sucrose levels increased, the Ah biofilm formation and the binding between Ah cells and monoclonal antibodies (mAbs, for immunodetection) decreased. Elevated ammonia nitrogen and nitric nitrogen levels generated no significant impact on Ah biofilm formation or immunodetection (P > 0.05). The expression of mAbs-targeted Omp remained unchanged under high NaCl or sucrose conditions. Further analysis showed that high sucrose conditions led to the over-expression of the extracellular polysaccharides (PS) and promoted the formation of capsule-like structures. These over-expressed PS and capsule structures might be one reason explaining the inhibited immunodetection efficacy. Results generated from this study provide crucial insights for the design of recovery and detection protocols for Ah present in food or environmental samples.

Fermentation of ginkgo biloba kernel juice using Lactobacillus plantarum Y2 from the ginkgo peel: Fermentation characteristics and evolution of phenolic profiles, antioxidant activities in vitro, and volatile flavor compounds.

In this study, a strain of Lactobacillus plantarum Y2 was isolated from the ginkgo peel, and showed adequate adaptation to the ginkgo biloba kernel juice. After 48 h of fermentation, the number of viable cells in the stable growth phase was remained at 10.0 Log CFU/mL, while the content of total organic acid increased by 5.86%. Phenolic substances were significantly enriched, and the content of total phenolic substances increased by 9.72%, and the content of total flavonoids after fermentation exceeded 55.33 mg/L, which was 3.6 times that of the unfermented ginkgo juice. The total relative content of volatile flavor compounds increased by 125.48%, and 24 new volatile flavor substances were produced. The content of total sugar, total protein, and total free amino acid decreased to 44.85, 67.51, and 6.88%, respectively. Meanwhile, more than 82.25% of 4'-O-methylpyridoxine was degraded by lactic acid fermentation, and the final concentration in ginkgo biloba kernel juice was lower than 41.53 mg/L. In addition, the antioxidant and antibacterial activities of fermented ginkgo biloba kernel juice were significantly enhanced. These results showed that LAB fermentation could effectively improve the nutritional value and safety of ginkgo biloba kernel juice.

Screening of a Novel Lactiplantibacillus plantarum MMB-05 and Lacticaseibacillus casei Fermented Sandwich Seaweed Scraps: Chemical Composition, In Vitro Antioxidant, and Volatile Compounds Analysis by GC-IMS.

Lactic acid fermentation is a promising method for developing sandwich seaweed scraps. The objectives of this study were to investigate the effect of fermentation with Lactiplantibacillus plantarum MMB-05, Lactiplantibacillus casei FJAT-7928, mixed bacteria (1:1, v/v) and control on the physicochemical indexes, in vitro antioxidant activity, and volatile compounds of Porphyra yezoensis sauce. Sensory evaluation was also performed. The results indicated that all lactic acid bacteria strains grew well in P. yezoensis sauce after 72 h of fermentation, with the viable cell counts of L. plantarum MMB-05 exceeding 10.0 log CFU/mL, the total phenolic content increasing by 16.54%, and the lactic acid content increasing from 0 to 44.38 ± 0.11 mg/mL. Moreover, the metabolism of these strains significantly increased the content of umami, sweet and sour free amino acids in P. yezoensis sauce. The total antioxidant capacity of L. plantarum MMB-05, L. casei FJAT-7928, mix and control groups increased by 594.59%, 386.49%, 410.27%, and 287.62%, respectively. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis suggested that aldehydes and ketones accounted for the largest proportion, and the relative contents of acids and alcohols in P. yezoensis sauce increased significantly after lactic acid bacteria fermentation. In addition, the analysis of dynamic principal component analysis (PCA) and fingerprinting showed that the volatile components of the four treatment methods could be significantly distinguished. Overall, the L. plantarum MMB-05 could be recommended as an appropriate starter for fermentation of sandwich seaweed scraps, which provides a fundamental knowledge for the utilization of sandwiched seaweed scraps.

Preparation of Slowly Digested Corn Starch Using Branching Enzyme and Immobilized α-Amylase.

The aim of this study was to modify the digestibility and structure of corn starch by treatment with compound enzymes. Corn starch was treated with two enzymes (α-amylase, which catalyzes hydrolysis, and branching enzyme, a transglycosidase that catalyzes branch formation), and the reaction was monitored by determining the content of slowly digestible starch in the reaction product. The fine structure and physical and chemical properties of enzyme-modified starch samples were analyzed using scanning electron microscopy, gel chromatography, and X-ray diffraction methods; modified starch has a high degree of branching, a high proportion of short-chain branched structures, and greatly improved solubility. The results show that the slow digestion performance of corn starch was significantly improved after hydrolysis by α-amylase for 4 h and treatment with branching enzyme for 6 h. These results show that enzymatic modification of corn starch can improve its slow digestibility properties.

Recombinant expression and immunogenicity evaluation of a TonB-dependent receptor of Vibrio parahaemolyticus.

This study constructed the recombinant plasmid of a TonB-dependent receptor from V. parahaemolyticus and evaluated the immunogenicity of the recombinant protein in mice. The TonB-dependent receptor gene (GI: 28901321) was obtained by PCR amplification and cloned into plasmid pET-32a (+). The recombinant plasmids were transformed into Escherichia coli BL21, and the protein expression was induced by isopropyl-ß-d-thiogalactopyranoside (IPTG). The 6 × His-tagged TonB-dependent receptor inclusion bodies were purified by Ni-NTA Agarose column and renatured by gradient urea dialysis. The soluble and inclusion bodies of the TonB-dependent receptor were emulsified with Freund's adjuvant and subcutaneously injected into BALB/c mice. The serum titers with seven V. parahaemolyticus strains, eight Vibrio species, and nine other bacteria were studied by enzyme-linked immunosorbent assay and immunoblotting. The results showed that the serum homogenously bound the target protein in the V. parahaemolyticus cell lysates. The titers against the immunized protein were above 89K, while the titer against whole cells of seven V. parahaemolyticus strains ranged from 4.12K to 12.5K. However, the titers were higher for the soluble TonB-dependent receptor. The serums reacted with E. coli strains but did not cross-react with eight Vibrio species and Photobacterium damselae. These results showed that the TonB-dependent receptor proteins in this study were immunogenic, and the serums showed adequate specificity for V. parahaemolyticus. However, the availability of the TonB-dependent receptor on V. parahaemolyticus cells is probably limited.

Identification of a specific surface epitope of OmpC for Escherichia coli O157:H7 with protein topology facilitated affinity mass spectrometry.

The goal of this work was to identify the target protein and epitope of a previously reported Escherichia coli O157:H7 (ECO157)-specific monoclonal antibody (mAb) 2G12. mAb 2G12 has shown high specificity for the recovery and detection of ECO157. To achieve this goal, the target protein was first separated by two-dimensional gel electrophoresis (2-DE) and located by Western blot (WB). The protein spots were identified to be the outer membrane protein (Omp) C by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). After that, the target protein was purified by immunoaffinity chromatography (IAC) and subjected to in situ enzymatic cleavage of the vulnerable peptides. Eight eluted peptides of OmpC identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) were further mapped onto the homologous protein structure of E. coli OmpC (2IXX). The topology of OmpC showed that three peptides had extracellular loops. Epitope mapping with overlapping peptide library and sequence homology analysis revealed that the epitope consisted of a specific peptide, "LGVING," and an adjacent conservative peptide, "TQTYNATRVGSLG." Both peptides loop around the overall structure of the epitope. To test the availability of the epitope when ECO157 was grown under different osmolarity, pH, and nutrition levels, the binding efficacy of mAb 2G12 with ECO157 grown in these conditions was evaluated. Results further demonstrated the good stability of this epitope under potential stressful environmental conditions. In summary, this study revealed that mAb 2G12 targeted one specific and one conservative extracellular loop (peptide) of the OmpC present on ECO157, and the epitope was stable and accessible on ECO157 cells grown in different environment. KEY POINTS: • OmpC is the target of a recently identified ECO157-specific mAb 2G12. • Eight peptides were identified from the OmpC by using LC-MS/MS. • The specificity of mAb 2G12 is mainly determined by the "LGVING" peptide.

Effect of chitosan coatings incorporated sodium phytate on the shelf-life of Antarctic krill (Euphausia superba).

Chitosan is a preservative with potent antibacterial activity, and sodium phytate has antioxidant activity and potent ion chelating ability. The present work aimed to explore the effects of chitosan coating combined with sodium phytate (0.1% sodium phytate + 1% chitosan) on preserving Antarctic krill (Euphausia superba) during partially frozen storage. Treatment of chitosan coating combined with sodium phytate significantly suppressed microbial growth, the increases in pH value, total volatile basic nitrogen and sensory deterioration of Antarctic krill (E. superba) during partially frozen storage. Therefore, chitosan coating combined with sodium phytate may be a practical method to suppress quality deterioration of Antarctic krill and thus extend its shelf life.

Modulation of the growth performance, body composition and nonspecific immunity of crucian carp Carassius auratus upon Enteromorpha prolifera polysaccharide.

The present study investigated dietary Enteromorpha prolifera polysaccharide (EPP) on the growth performance, body composition and non-specific immunity of crucian carp Carassius auratus. Crucian carps with body weight of 51.24 ± 4.08 g were randomly divided into five groups: one group was fed with basic diet, while the other four groups were fed with diets containing 20, 40, 60 and 80 g/kg EPP. After 60 days of feeding, dietary administration of 40 g/kg EPP increased the body weight gain rate, feed conversion ratio, specific growth rate, body crude protein content, intestine digestive enzyme activities, serum lysozyme activity, acid phosphatase activity, alkaline phosphatase activity, complement 3 level, superoxide dismutase activity and catalase activity and decreased body fat content and serum total cholesterol, triacylglycerol, alanine aminotransferase activity and glutamic oxaloacetic transaminase activity compared with those of the control group. All levels of EPP improved the resistance to Aeromonas hydrophilia compared with the control group. The results indicated that EPP could promote the growth of crucian carp and improve their disease resistance and may be used as a dietary supplement for crucian carp.

Identification of Vibrio parahaemolyticus and Vibrio spp. Specific Outer Membrane Proteins by Reverse Vaccinology and Surface Proteome.

The discovery of outer membrane proteins (OMPs) with desirable specificity and surface availability is a fundamental challenge to develop accurate immunodiagnostic assay and multivalent vaccine of pathogenic Vibrio species in food and aquaculture. Herein 101 OMPs were systemically screened from 4,831 non-redundant proteins of Vibrio parahaemolyticus by bioinformatical predication of signaling peptides, transmembrane (TM) α-helix, and subcellular location. The sequence homology analysis with 32 species of Vibrio spp. and all the non-Vibrio strains revealed that 15 OMPs were conserved in at least 23 Vibrio species, including BamA (VP2310), GspD (VP0133), Tolc (VP0425), OmpK (VP2362), OmpW (VPA0096), LptD (VP0339), Pal (VP1061), flagellar L-ring protein (VP0782), flagellar protein MotY (VP2111), hypothetical protein (VP1713), fimbrial assembly protein (VP2746), VacJ lipoprotein (VP2214), agglutination protein (VP1634), and lipoprotein (VP1267), Chitobiase (VP0755); high adhesion probability of flgH, LptD, OmpK, and OmpW indicated they were potential multivalent Vibrio vaccine candidates. V. parahaemolyticus OMPs were found to share high homology with at least one or two Vibrio species, 19 OMPs including OmpA like protein (VPA073), CsuD (VPA1504), and MtrC (VP1220) were found relatively specific to V. parahaemolyticus. The surface proteomic study by enzymatical shaving the cells showed the capsular polysaccharides most likely limited the protease action, while the glycosidases improved the availability of OMPs to trypsin. The OmpA (VPA1186, VPA0248, VP0764), Omp (VPA0166), OmpU (VP2467), BamA (VP2310), TolC (VP0425), GspD (VP0133), OmpK (VP2362), lpp (VPA1469), Pal (VP1061), agglutination protein (VP1634), and putative iron (III) compound receptor (VPA1435) have better availability on the cell surface.

Stimulating effects of polysaccharide from Angelica sinensis on the nonspecific immunity of white shrimps (Litopenaeus vannamei).

Angelica sinensis polysaccharide (ASP) was prepared by hot water extraction. Then, high-performance liquid chromatography and ion chromatography analyses were conducted, and the results indicated that ASP is a heteropolysaccharide, has a molecular mass of 82,000 Da and consists of arabinose, galactose and glucose (molar ratio of 6:1:1). The effects of ASP on the nonspecific immunity of white shrimps (Litopenaeus vannamei) were investigated by feeding them with ASP-containing diets (0.5, 1 and 1.5 g/kg) during a 12-week breeding experiment. Oral ASP administration significantly improved the survival rate, phenoloxidase activity, superoxide dismutase activity, glutathione peroxidase level, disease resistance against V. alginolyticus, total haemocyte count and number of hyaline cells, semigranular cells and granular cells (p < .05). ASP exhibits immunostimulatory effects on Pacific white shrimps (L. vannamei) and may thus be used as a diet supplement for them.

Purification and characterisation of a novel angiotensin-I converting enzyme (ACE)-inhibitory peptide derived from the enzymatic hydrolysate of Enteromorpha clathrata protein.

Hydrolysates containing angiotensin-I converting enzyme (ACE)-inhibitory peptide were prepared from Enteromorpha clathrata protein using alcalase. The hydrolysates were fractionated into two molecular-weight ranges (below and above 10kDa) by ultrafiltration. The below-10kDa fraction showed higher ACE-inhibitory activity and was subsequently purified by Sephadex G-15 gel filtration chromatography. The structure of active peptide was identified as Pro-Ala-Phe-Gly by HPLC-Q-TOF-MS and its IC50 value was 35.9µM. The yield of this peptide from E. clathrata protein was 0.82%. Lineweaver-Burk plots demonstrated that the inhibitory kinetic mechanism of this peptide was non-competitive. Stability study revealed that the purified peptide showed resistance against gastrointestinal proteases. Thus, E. clathrata protein hydrolysate treated with alcalase is a beneficial ingredient of nutraceuticals and pharmaceuticals against hypertension and related diseases.

Effect of water-soluble chitosan in combination with glutathione on the quality of pen shell adductor muscles.

In this study, the effects of the water-soluble chitosan (WSC) in combination with glutathione on preservation of pen shell adductor muscles (PSAM) during frozen storage were investigated. The PSAM samples were soaked in the solution containing 0.1% WSC in combination with 0.1% glutathione (treatment group) or in water (control group), and then they were stored under frozen conditions for 10 months, during which the samples were taken periodically and their total viable count, pH, total volatile basic nitrogen, and overall acceptability score were evaluated. Compared with the control group, treatment of WSC in combination with glutathione resulted in slower bacterial growth, lower pH increasing, lower total volatile basic nitrogen, and higher overall acceptability score of PSAM during frozen storage. The results show that treatment with WSC in combination with glutathione could prolong the shelf life of PSAM for up to 10 months.

Cellulase-assisted extraction and antioxidant activity of the polysaccharides from garlic.

In the present study, the polysaccharides were prepared from garlic by using a cellulase-assisted extraction method and the antioxidant activity of garlic polysaccharides (GPs) was evaluated. To improve the yield of GPs, the influences of the several factors such as extraction time, temperature, pH, and cellulase amount on the extraction efficiency were studied. The optimal conditions for extraction of GPs were determined as follows: time, 80 min; temperature, 45 °C; pH, 5; cellulase amount, 8000 U/g. Under the optimised extraction conditions, the yield of GPS reached up to 35.34%. The GPs product exhibited strong antioxidant activity including hydroxyl radical scavenging activity, 2,2-diphenyl-ß-picrylhydrazyl radical scavenging activity, and reducing power. The results suggest that the GPs could be used as potential antioxidants.

Effect of trehalose on Lateolabrax japonicus myofibrillar protein during frozen storage.

The effect of trehalose on the denaturation of weever (Lateolabrax japonicus) myofibrillar protein during frozen storage at -18 °C for 90 d was investigated. Trehalose (2.5-10 g dry weight) was added to 100 g of myofibrillar protein, and changes in the Ca(2+)-adenylpyrophosphatase (ATPase) activity, solubility, sulfhydryl content, and unfrozen water content of myofibrils were examined during frozen storage. Ca(2+)-ATPase activity and myofibrillar protein solubility decreased gradually during frozen storage at -18 °C upon addition of trehalose. By contrast, Ca(2+)-ATPase activity and myofibrillar protein solubility in the control group dropped drastically during the first 45 d of storage and then further decreased gradually for up to 90 d of storage, indicating a biphasic denaturation pattern. Trehalose addition significantly increased sulfhydryl and unfrozen water contents in the myofibrillar protein of the treatment groups compared with that of the control group (p<0.05) during frozen storage at -18 °C.

Effect of chitooligosaccharides on the denaturation of weever myofibrillar protein during frozen storage.

We investigated the effect of chitooligosaccharides on the denaturation of weever (Lateolabrax japonicus) myofibrillar protein during frozen storage at -18 °C for 90 days. Chitooligosaccharides (2.5-10 g dry weight) were added to 100 g of myofibrillar protein, and the changes in the Ca-adenylpyrophosphatase (ATPase) activity, unfrozen water content, solubility, and sulfhydryl content of the myofibrillar protein were examined during frozen storage. We observed that the Ca-ATPase activity and solubility of the myofibrillar protein decreased gradually during frozen storage at -18 °C following the addition of chitooligosaccharides. In contrast, the Ca-ATPase activity and solubility of the myofibrillar protein of the control group decreased markedly during the first 45 days of storage and then further decreased gradually for up to 90 days of storage, indicating a biphasic denaturation pattern. The addition of chitooligosaccharides resulted in a significant increase in unfrozen water and sulfhydryl contents of the myofibrillar protein of the treatment group compared with that of the control group (p<0.05) during frozen storage at -18 °C.

Chitooligosaccharides suppress the freeze-denaturation of actomyosin in Aristichthys nobilis surimi protein.

Effect of chitooligosaccharides on the denaturation of bighead carp (Aristichthys nobilis) surimi protein during frozen storage at -18 °C was investigated. The addition of 4 g of chitooligosaccharides to 100 g of the bighead carp (A. nobilis) surimi effectively inhibited the inactivation of the Ca(2+)-ATPase during frozen storage at -18 °C for 15 days compared to the control group (p<0.05), while excessive chitooligosaccharides decreased the inhibition effect. The Ca(2+)-ATPase activity of actomyosin for the treatment group decreased gradually during frozen storage at -18 °C, while that of the control dropped drastically and could not be detected after 30 days of storage. On the other hand, the addition of chitooligosaccharides also significantly increased the solubility of actomyosin compared to the control group (p<0.05) during frozen storage at -18 °C up to 120 days.