Modified chitosan with different phenolic acids: Characterization, physicochemical properties, and biological activity.

This study synthesized five phenolic acid-chitosan copolymers utilizing the carbodiimide-mediated chemical crosslinking reaction. Comprehensive evaluations were conducted on their structural attributes, physicochemical properties, and biological activities. Fourier transform infrared confirmed successful grafting of phenolic acids onto chitosan via amide linkages. Additionally, ultraviolet-visible absorption spectroscopy and proton nuclear magnetic resonance analyses revealed novel absorption peaks between 200 and 400 nm and 6.0-8.0 ppm, respectively, attributable to the incorporated phenolic acids. Notably, the chitosan-gentisate acid copolymer exhibited significantly enhanced biological activity (p < 0.05) compared to pure chitosan and the other four conjugates, attributed to its highest grafting degree of approximately 295.93 mg/g. These modified chitosan derivatives effectively preserved the quality of sea bass (Lateolabrax japonicus) during refrigerated storage, extending its shelf-life by up to 9 days, 7 days, and 4 days relative to control, chitosan, and gentisate acid groups.

Characterization of active films based on chitosan/polyvinyl alcohol integrated with ginger essential oil-loaded bacterial cellulose and application in sea bass (Lateolabrax japonicas) packaging.

The poor mechanical properties, low water-resistance, and limited antimicrobial activity of chitosan (CS)/polyvinyl alcohol (PVA) based film limited its application in aquatic product preservation. Herein, bacterial cellulose (BC) was used to load ginger essential oil (GEO). The effects of the addition of BC and different concentrations of GEO on the physicochemical and antimicrobial activities of films were systematically evaluated. Finally, the application of sea bass fillets was investigated. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD) analysis indicated dense networks were formed, which was verified by enhanced physical properties. The mechanical properties, barrier properties, and antimicrobial activities enhanced as GEO concentration increased. CPB0.8 (0.8 % GEO) film had better tensile strength (TS) and barrier performance, improved the quality, and extended the shelf-life of sea bass for another 6 days at least. Overall, active films are potential packaging materials for aquatic products.

Effects of slightly acidic electrolyzed water combined with ԑ-polylysine-chitooligosaccharide Maillard reaction products treatment on the quality of vacuum packaged sea bass (Lateolabrax japonicas).

In this study, a new natural preservative, ε-polylysine (ε-PL) and chitooligosaccharides (COS) Maillard reaction products (LC-MRPs), was prepared by Maillard reaction. The preservation effect of LC-MRPs combined with slightly acidic electrolyzed water (SAEW) pretreatment (SM) on vacuum-packed sea bass during refrigerated storage was evaluated. The results showed that after 16 days, SM treatment could effectively inhibit the microbial growth and prevent water migration in sea bass. In addition, the highest water holding capacity (69.79 %) and the best sensory characteristics, the lowest malonaldehyde (MDA) (58.96 nmol/g), trimethylamine (TMA) (3.35 mg/100 g), total volatile basic nitrogen (TVB-N) (16.93 mg N/100 g), myofibril fragmentation index (MFI) (92.2 %) and TCA-soluble peptides (2.16 µmol tyrosine/g meat) were related to SM group. Combined with sensory analysis, we can conclude that the combined treatment of SAEW and LC-MRPs could prolong the shelf-life of sea bass for another 11 days compared with the DW group. Results disclosed that the composite treatment of SAEW and LC-MRPs is a promising technology to improve the shelf-life of vacuum-packed sea bass during refrigerated storage.

Phenolic acid-chitosan derivatives: An effective strategy to cope with food preservation problems.

Chitosan, a cost-effective and eco-friendly natural polymeric material, possesses excellent film-forming properties. However, it has low solubility and biological activity, which hinders its widespread applications. To overcome these limitations, researchers have developed phenolic acid-chitosan derivatives that greatly enhance the mechanical, antibacterial and antioxidant properties of chitosan, expanding its potential application, particularly in food preservation. This review aims to provide an in-depth understanding of the structure and biological activity of chitosan and phenolic acid, as well as various synthetic techniques employed in their modification. Phenolic acid-chitosan derivatives exhibit improved physicochemical properties, such as enhanced water solubility, thermal stability, rheological properties, and crystallinity, through grafting techniques. Moreover, these derivatives demonstrate significantly enhanced antibacterial and antioxidant activities. Through graft modification, phenolic acid-chitosan derivatives offer promising applications in food preservation for diverse food products, including fruits, vegetables, meat, and aquatic products. Their ability to improve the preservation and quality of these food items makes them an appealing option for the food industry. This review intends to provide a deeper understanding of phenolic acid-chitosan derivatives by delving into their synthetic technology, characterization, and application in the realm of food preservation.

Effect of chlorogenic acid grafted chitosan on microbiological compositions of sea bass (Lateolabrax japonicus) fillets: Dominant spoilage bacteria, inhibition activity and membrane damage mechanisms.

This study investigated the effect of chlorogenic acid grafted chitosan (CS-g-CA) on the microbiota composition of sea bass (Lateolabrax japonicus), isolated and identified the specific spoilage organisms (SSOs) in the late stage of refrigerated fillets and evaluation of their spoilage potential. Moreover, antibacterial activity and membrane damage mechanism of CS-g-CA against spoilage bacteria was also investigated. Illumina-MiSeq high throughput sequencing results showed that CS-g-CA retarded the growth of Pseudomonas spp., which largely contributed to delaying the quality degradation of sea bass during storage. Then nine spoilage bacteria were isolated and identified from the fillets at the end of storage and inoculated into sterile fish fillets to determine their spoilage capacity. Results showed that fish fillets inoculated with spoilage bacteria exhibited a significant increase in TVB-N, TBA and putrescine content and decreased sensory quality during storage. Subsequently, the inhibitory activity of CS-g-CA against spoilage bacteria was investigated and strains that were more sensitive to the CS-g-CA with a strong spoilage capacity were selected for the study of the inhibition mechanism. Results suggested that CS-g-CA had strong inhibitory activity and led to bacterial death through the mechanism of membrane damage. Overall, this study analyzed the effect of CS-g-CA on the preservation of fish fillets from a microbiological point of view to provide a reference for the anti-bacterial preservation of aquatic products.

Natural phenolic compounds: Antimicrobial properties, antimicrobial mechanisms, and potential utilization in the preservation of aquatic products.

Natural antibacterials have stood out in the last decade due to the growing demand for reducing chemical preservatives in food. In particular, natural phenolic compounds are secondary metabolites produced by plants for numerous functions including antimicrobial defence. Polyphenol has significant antimicrobial activity, but its antimicrobial properties are affected by the cell structure difference of bacteria, the concentration, type, and extraction method of polyphenol, and the treatment time of bacteria exposed to polyphenol. Therefore, this paper analyzed the antibacterial activity and mechanism of polyphenol as an antimicrobial agent. However, there remained significant considerations, including the interaction of polyphenols and food matrix, environmental temperature, and the effect of color and odor of some polyphenols on sensory properties of aquatic products, and the additive amount of polyphenols. On this basis, the application strategies of polyphenols as the antimicrobial agent in aquatic products preservation were reviewed.

Synergistic Effect of Combined Treatment with Allicin and Antioxidant of Bamboo Leaves and Preservation of Bullfrogs (Lithobates catesbeiana) during Refrigeration Storage.

The effects of allicin and antioxidant of bamboo leaves (AOB) on the quality of bullfrogs (Lithobates catesbeiana) during refrigerated storage (4 °C) were investigated. The quality changes in samples treated with deionized water (CK), allicin solution (All), antioxidant of bamboo leaves (AOB), and allicin solution combined with AOB solution (AA) in microbiological, physicochemical, and sensory evaluation were analyzed, respectively. The results demonstrated that combination treatment inhibited the increase in total viable counts, delayed the decrease in amino acid content, and retarded the sensory deterioration. Preservative treatment has an inhibitory effect on the early storage of PBC, which can reduce PBC by about 1.0 log CFU/g. The reduction in thiobarbituric acid (TBA) content and total volatile basic nitrogen (TVB-N) content indicated that combination treatment could better restrain the lipid oxidation and degradation of protein than the CK group and single-treatment group. In addition, the TVB-N content in the AA group still did not exceed the threshold on the 14th day. As a consequence, combination treatment prolonged the shelf life of bullfrogs for another six days. Therefore, allicin and AOB with excellent antioxidant and antimicrobial activity could be an effective approach to delay the biochemical reaction of refrigerated bullfrogs. This study has provided a potential approach for increasing the shelf life of bullfrogs and preserving their quality during refrigerated storage.

Antibacterial and antioxidant properties of phenolic acid grafted chitosan and its application in food preservation: A review.

Chitosan is a bio-renewable natural polymeric material. The antibacterial and antioxidant activity of chitosan can be enhanced by grafting with phenolic acids to further expand its application in food. Therefore, this paper focuses on reviewing the structure, antimicrobial and antioxidant activities and their mechanisms with phenolic acid-g-CS, evaluating its cytotoxicity, and describing its application in various food preservation. In general, different reaction mechanisms of phenolic acid-g-CS synthesis lead to different product structures. Compared to chitosan, phenolic acid-g-chitosan exhibited enhanced antibacterial and antioxidant activities. The toxicity assessment showed that phenolic acid-g-CS is not cytotoxic. Moreover, phenolic acid-g-CS has been applied to a variety of food products such as fruits, vegetables and meat with good results. Overall, this review provides a certain reference for subsequent researchers to design phenolic acid-g-CS more rationally and for the subsequent development of phenolic acid-g-CS in food preservation.

Recent developments in nanoemulsions against spoilage in cold-stored fish: A review.

Nanoemulsion-based technology is developing rapidly in the food industry, especially in the design of delivery systems for bioactive compounds. This review presents an in-depth understanding of the composition, function, antibacterial mechanism and successful application of nanoemulsions as preservative agents against fish spoilage. The results showed that the inclusion of bioactive substances in the food-grade nanoemulsions encapsulation system could improve its stability, control its release, inhibit the microbial growth and reproduction through a variety of targets. These nanoemulsions can inhibit fish spoilage via reducing microbial load and retarding the oxidation of proteins and lipids, thereby maintaining quality attributes of fish. In addition, nanoemulsions could be coupled with vacuum package for enhancing microbial destruction, retaining nutritional value and extending the shelf-life of fish. Accordingly, nanoemulsions are suggested as a promising strategy to inhibit fish spoilage.

Effect of food matrix on rapid detection of Vibrio parahaemolyticus in aquatic products based on toxR gene.

Vibrio parahaemolyticus has become an important public threat to human health. Rapid and robust pathogen diagnostics are necessary for monitoring its outbreak and spreading. Herein, we report an assay for the detection of V. parahaemolyticus based on recombinase aided amplification (RAA) combined with lateral flow dipstick (LFD), namely RAA-LFD. The RAA-LFD took 20 min at 36~38 â„ƒ, and showed excellent specificity. It detected as low as 6.4 fg/µL of V. parahaemolyticus in genomic DNA, or 7.4 CFU/g spiked food samples with 4 h of enrichment. The limit of detection in shrimp (Litopenaeus Vannamei), fish (Carassius auratus), clam (Ruditapes philippinarum) evidenced that sensitivity was considerably affected by the food matrix. The presence of food matrix reduced the sensitivity of spiked food samples by 10 ~ 100 times. In the filed samples detection, RAA-LFD method showed good coincidence with GB4789.7-2013 method and PCR method at rates of 90.6% and 94.1%, respectively. RAA-LFD has high accuracy and sensitivity for the detection of V. parahaemolyticus, which can serve as a model tool to meet the growing need for point-of-care diagnosis of V. parahaemolyticus.

Chitosan-grafted-caffeic acid combined with ultrasound inhibits the oxidation and degradation of myofibrillar proteins in pompano (Trachinotus ovatus) during ice storage.

This study aimed to investigate the impact of chitosan-grafted-caffeic acid (CS-g-CA) and ultrasound (US) on myofibrillar proteins (MPs) in pompano (Trachinotus ovatus) during 24 days of ice storage. Fresh fish slices were treated with US (20 kHz, 600 W), CS-g-CA (G), and US combined with CS-g-CA (USG) for 10 min, respectively. Samples treated with sterile water served as study controls (CK). All samples were then stored in ice at 4 °C. The oxidation and degradation of MPs were evaluated at 4-day intervals. The results showed that US slightly accelerated the fragmentation of myofibrils, as confirmed by the increased myofibril fragmentation index (MFI). However, on day 24, the surface hydrophobicity (SH) of USG samples was 4.09 µg BPB bound/mg protein lower than that of G samples, and the total sulfhydryl content of USG samples was 0.50 µmol g-1 higher than that of G samples, suggesting that US could reinforce the antioxidant capacity of CS-g-CA. Regarding degradation of MPs, USG treatment maintained the secondary and tertiary structure of MPs by reducing the transition from ordered to disordered structures and by reducing the exposure of tryptophan residues. Sodium dodecyl sulphate- polyacrylamide gel electrophoresis (SDS-PAGE) showed that the inhibitory effect of USG on protein degradation may be related to the binding of CS-g-CA to MPs. The results of scanning electron microscopy (SEM) further clarified the fact that the USG treatment can protect the myofibril microstructure by maintaining the compact arrangement of muscle fibers. Additionally, USG treatment could improve the sensory properties of pompano. Overall, the synergistic effects of US and CS-g-CA can effectively delay the protein oxidation and degradation. The results provided in this study are valuable for the quality maintenance of marine fish.

Inhibitory effect of chlorogenic acid-grafted chitosan on seafood isolates Pseudomonas fluorescens and its biofilm.

This study aimed to examine the inhibition of chlorogenic acid-grafted chitosan (CS-g-CA) on Pseudomonas fluorescens (P. fluorescens) and its biofilm. The minimum inhibitory concentration (MIC) of CS-g-CA against P. fluorescens was 1.25 mg/mL. Alkaline phosphatase (AKPase) leakage assay and scanning electron microscopy (SEM) observation showed that CS-g-CA causes structural damage to cell walls and membranes, resulting in the loss of function. In addition, CS-g-CA was able to disrupt the antioxidant system of P. fluorescens, interfere with energy metabolism, and interact with genomic DNA, affecting the normal physiological function of bacteria. It was also found that CS-g-CA inhibited the flagellar motility of P. fluorescens, which may be responsible for the inhibition of its biofilm formation. CS-g-CA at 2MIC was able to remove 71.64% of the mature biofilm and reduce the production of extracellular polysaccharides (EPS) by 60.72%. This was further confirmed by confocal laser scanning microscopy (CLSM), which showed a significant reduction in the amount of biofilm. In summary, CS-g-CA has strong antibacterial and anti-biofilm activities against P. fluorescens, and it can be applied as a potential seafood bacteriostatic agent.

Characterization of Phage vB_SalM_SPJ41 and the Reduction of Risk of Antibiotic-Resistant Salmonella enterica Contamination in Two Ready-to-Eat Foods.

Salmonella enterica is a major cause of foodborne illness, and the emergence of antibiotic-resistant bacteria has led to huge pressures on public health. Phage is a promising strategy for controlling foodborne pathogens. In this study, a novel Salmonella phage vB_SalM_SPJ41 was isolated from poultry farms in Shanghai, China. Phage vB_SalM_SPJ41 was able to lyse multiple serotypes of antibiotic-resistant S. enterica, including S. Enteritidis, S. Typhimurium, S. Shubra, S. Derby, and S. Nchanga. It had a short incubation period and was still active at a temperature <80 °C and in the pH range of 3~11. The phage can effectively inhibit the growth of S. enterica in liquid culture and has a significant inhibitory and destructive effect on the biofilm produced by antibiotic-resistant S. enterica. Moreover, the phage was able to reduce S. Enteritidis and MDR S. Derby in lettuce to below the detection limit at 4 °C. Furthermore, the phage could reduce S. Enteritidis and S. Derby in salmon below the limit of detection at 4 °C, and by 3.9 log10 CFU/g and· 2.1 log10 CFU/g at 15 °C, respectively. In addition, the genomic analysis revealed that the phages did not carry any virulence factor genes or antibiotic resistance genes. Therefore, it was found that vB_SalM_SPJ41 is a promising candidate phage for biocontrol against antibiotic-resistant Salmonella in ready-to-eat foods.

Preparation and antimicrobial mechanism of Maillard reaction products derived from ε-polylysine and chitooligosaccharides.

Chitooligosaccharides can be combined with amino acids or polypeptide to form Maillard reaction products (MRPs) with the antibacterial characteristics through Maillard reaction. This research aims to clarify the structure, antimicrobial effect and mechanism against Shewanella putrefaciens (S. putrefaciens) of ε-polylysine and chitooligosaccharides Maillard reaction products (LC-MRPs). The results of intrinsic fluorescence (IF) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, proton nuclear magnetic resonance (1H NMR) spectra and scanning electron microscope (SEM) indicated Maillard reaction occurred between ε-polylysine and chitooligosaccharides. The observation of confocal laser scanning microscopy (CLSM), SEM and growth curves of S. putrefaciens evidenced that LC-MRPs have the strongest antibacterial effects. The leakage of alkaline phosphatase (AKP) and lactate dehydrogenase (LDH) implied that LC-MRPs sabotaged bacterial barrier (cell wall and cell membrane). The changes in content of nucleic acids, reactive oxygen species (ROS) level, lipid peroxidation content (LPO), succinate dehydrogenase (SDH) activity and adenosine triphosphate (ATP) content showed LC-MRPs will affect bacterial genetic gene transcription, material and energy metabolism. Therefore, the LC-MRPs were effective antibacterial agents to inhibit S. putrefaciens, which will help to preserve food with S. putrefaciens as the main spoilage bacteria.

Ultrasound assisted treatment improves the preservation performance of chitosan-grafted-chlorogenic acid on refrigerated sea bass (Lateolabrax japonicus) fillets.

BACKGROUND: Ultrasound can increase the mass transfer between preservatives and food, and enhances the effect of preservatives on food. Chitosan-grafted-chlorogenic acid (CS-g-CA) is a new synthetic compound with good antiseptic properties. Therefore, the present study evaluated the preservation performance of ultrasound-assisted CS-g-CA (GUA) coatings on refrigerated sea bass fillets in terms of changes in microorganisms, lipids, proteins, tissue structures, and moisture. RESULTS: The results showed that GUA treatment effectively inhibited the growth of microorganisms in sea bass fillets. Meanwhile, the changes in total volatile basal nitrogen, thiobarbituric acid reactive substances, and pH values were all slowed down under GUA treatment, indicating that protein degradation and lipid oxidation in sea bass were inhibited. Low-field nuclear magnetic resonance and magnetic resonance imaging results indicated that the GUA retarded the conversion of mobile water to free water. In addition, GUA treatment maintained the flavor quality of fish fillets, and also inhibited the reduction of inosine monophosphate and the production of bitter substances (inosine and hypoxanthine), suppressed muscle tissue degeneration, and maintained better sensory scores. CONCLUSION: Overall, GUA treatment inhibited microbial growth, protein degradation, lipid oxidation, moisture migration, decomposition of umami substances, and deterioration of sensory quality in sea bass fillets. Finally, the shelf-life of sea bass fillets with GUA treatment was extended by an additional 9 days. The results showed that ultrasonic assistance further enhanced the effect of preservatives on aquatic products. © 2022 Society of Chemical Industry.

Effects of ε-polylysine and chitooligosaccharide Maillard reaction products on quality of refrigerated sea bass fillets.

BACKGROUND: The Maillard reaction is a promising and safe method for obtaining chitooligosaccharide conjugates with proteins or peptides as food preservatives. This study aims to investigate the moisture state, physicochemical properties, and shelf-life of sea bass fillets treated with ε-polylysine (ε-PL) and chitooligosaccharides (COS), which are Maillard reaction products (LC-MRPs), during refrigerated storage. RESULTS: The results of microbiological analysis and confocal laser scanning microscope (CLSM) revealed that LC-MRPs could retard microbial growth effectively. Compared with control, other treated groups could strongly retard the increase in the thiobarbituric acid (TBA) value, the K-value and the total volatile basic nitrogen (TVB-N) value, and also inhibited the softening of texture and the accumulation of biogenic amines in fish. The results of low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) indicate that LC-MRPs could delay the water migration of fillets and increase water holding capacity (WHC). Through sensory evaluation, the application of LC-MRPs increased the shelf-life of refrigerated sea bass fillets for another 9 days. CONCLUSION: Maillard reaction products derived from chitooligosaccharides and ε-polylysine have strong potential for preserving sea bass. © 2022 Society of Chemical Industry.

Slightly acidic electrolyzed water-slurry ice: shelf-life extension and quality maintenance of mackerel (Pneumatophorus japonicus) during chilled storage.

BACKGROUND: Different ice treatments were applied for the preservation of mackerel (Pneumatophorus japonicus). The quality changes of samples treated with flake ice (Control), slurry ice (SI) and slightly acidic electrolyzed water-slurry ice (SAEW-SI) in microbiological, physicochemical, protein characteristic, and sensory evaluation were investigated during chilled storage. RESULTS: SAEW-SI showed a significant advantage for the inhibition of microbial growth, which could extend the shelf-life for another 144 h at least, compared with Control group. SAEW-SI treatment also showed a strong inhibition for the increase in pH, total volatile basic nitrogen (TVB-N), K-value, histamine and metmyoglobin (MetMb) content. Results of texture profile analysis (TPA) and water holding capacity (WHC) indicated that SAEW-SI can obviously suppress the decrease of hardness value, and have a better protective effect on muscle structure compared to flake ice and SI (P < 0.05). During the whole experiment, the highest sensory scores and a* were obtained in the SAEW-SI group, which indicated that SAEW-SI treatment could maintain better sensory characteristics. According to the results of thiobarbituric acid reactive substances (TBARS) and fluorescence spectroscopy analysis, SAEW-SI treatment could effectively retard protein degradation and lipid oxidation compared with Control and SI group. In maintaining the quality of mackerel, SAEW-SI shows a better effect than SI due to the synergistic effect of fence factors. CONCLUSION: The results demonstrated that the shelf-life of mackerel could be extended and the quality of mackerel could be maintained effectively with SAEW-SI treatment during chilled storage. © 2022 Society of Chemical Industry.

Chemical modifications in the structure of marine polysaccharide as serviceable food processing and preservation assistant: A review.

Marine polysaccharides are a kind of natural polysaccharides which isolated and extracted from marine organisms. Now some marine polysaccharides, such as chitosan, sodium alginate and agar, have been proven to exhibit antibacterial, antioxidant functions and biocompatibility, which are often used to preserve food or improve the physicochemical properties of food. However, they still have the defects of unsatisfactory preservation effect and biological activity, which can be remedied by its modification. Chemical modification is the most effective of all modification methods. The advances in common chemical modification methods of chitosan, sodium alginate, agar and other marine polysaccharides and research progress of modified products in food processing and preservation were summarized, and the influence of additional reaction conditions on the existence of chemical modification sites of polysaccharides was discussed. The modification of functional groups in natural marine polysaccharides leads to the change of molecular structure, which can improve the physical, chemical and biological properties of marine polysaccharides. Chemically modified products have been used in various fields of food applications, such as food preservatives, food additives, food packaging, and food processing aids. In general, chemical modification has excellent potential for food processing and preservation, which can improve the function of marine polysaccharides.

Antimicrobial and anti-biofilm activities of chlorogenic acid grafted chitosan against Staphylococcus aureus.

In this work, Chitosan-grafted-chlorogenic acid (CS-g-CA) was prepared by the carbodiimide method. The purpose of this study was to investigate the antibacterial and anti-biofilm activity of CS-g-CA against Staphylococcus aureus (S. aureus). The minimum inhibitory concentration (MIC) of CS-g-CA against S. aureus was identified as 0.625 mg/mL. S. aureus treated with 1/2 × MIC of CS-g-CA had a longer logarithmic growth phase than that of the CK group, while 1 × MIC and 2 × MIC inhibited the growth of bacteria. The damaging effect of CS-g-CA on bacterial cells was analyzed by measuring the activity of cellular antioxidant enzymes (Catalase (CAT) and Glutathione peroxidase (GSH-Px)) and intracellular enzymes (alkaline phosphatase (AKPase) and adenosine triphosphatase (ATPase)). The results of DNA gel electrophoresis illustrated that CS-g-CA disrupted the normal metabolism of bacteria. Scanning electron microscopy (SEM) results showed that S. aureus shrank and died under CS-g-CA treatment. 1 × MIC of CS-g-CA can significantly inhibit the formation of biofilms, and 1/2 × MIC of CS-g-CA control the swimming speed of S. aureus. In addition, 77.53% mature biofilm and 60.62% extracellular polysaccharide (EPS) in the mature biofilm of S. aureus were eradicated by CS-g-CA at 2 × MIC. Confocal laser scanning microscopy (CLSM) observation further confirmed these results. Therefore, CS-g-CA was an antimicrobial and antibiofilm agent to control S. aureus, which can effectively controlling the growth of S. aureus in food, thereby preventing the occurrence of food-borne diseases.

The effects of tea polyphenol-ozonated slurry ice treatment on the quality of large yellow croaker (Pseudosciaena crocea) during chilled storage.

BACKGROUND: The aim of the current study was to evaluate the synergistic effects of tea polyphenol-ozonated slurry ice on the quality, physicochemical and protein characteristics of large yellow croaker (Pseudosciaena crocea) during chilled (4 °C) storage. To 0.3% tea polyphenol combined with ozone water was added sodium chloride until the salt concentration reached 3.3% and with the use of an ice machine the mixture formed the tea polyphenol-ozonated slurry ice. Microbial [total viable count (TVC)], physicochemical [total volatile basic nitrogen (TVB-N), K value], myofibrillar fragmentation index (MFI), Ca2+ -ATPase activity, total sulfhydryl content, intrinsic fluorescence intensity (IFI), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were analyzed during chilled (4 °C) storage for up to 20 days. RESULTS: The results showed that tea polyphenol-ozonated slurry ice could effectively inhibit the increase of TVC and TVB-N, reduce the degree of adenosine triphosphate (ATP) degradation. In addition, the tea polyphenol-ozonated slurry ice treatment could protect the integrity of myosin in myofibrillar proteins (MPs) by inhibiting the decrease of Ca2+ -ATPase activity and the content of total sulfhydryl. Furthermore, the tea polyphenol-ozonated slurry ice presented a superiorly protective effect on protein structure in MPs as manifested by the results of IFI, FTIR and SDS-PAGE. It was possible that due to the addition of tea polyphenol, the antioxidant activity of this complex was significantly improved. CONCLUSION: The tea polyphenol-ozonated slurry ice treatment can maintain the quality of large yellow croaker by decreasing the damage of MP caused by the interaction between microorganisms and endogenous enzymes. © 2022 Society of Chemical Industry.