Effect of a chitosan coating incorporating epigallocatechin gallate on the quality and shelf life of bighead carp (Aristichthys nobilis) fillets during chilled storage

Functionality, physicochemical properties, and applications of chitosan/nano-hydroxyapatite-tea polyphenol films

An active chitosan (CS) film containing a nano-hydroxyapatite-tea polyphenol (HAP-TP) complex was designed and prepared. The effects of HAP-TP loading on the structural and physicochemical properties of the CS-based film were evaluated. The mechanical and thermal properties of the film were significantly improved by the resulting intermolecular interactions and formation of hydrogen bonds between HAP-TP and CS, which reduced the water vapor and oxygen permeabilities of the film by 29.78 and 35.59 %, respectively. The CS-HAP-TP film exhibited excellent slow-release behavior and antioxidant activity, with a cumulative release rate at 700 h 6.79 % lower than that of CS-TP films. The CS-HAP-TP film significantly inhibited the deterioration of semi-dried golden pompano, and thus helped to retain the taste of umami and sweet amino acids in fish samples, while reducing off-flavor generation. The film therefore shows considerable potential as an active packaging material for the preservation of semi-dried fish products.

Insight into flavor changes in bighead carp (Aristichthys nobilis) fillets during storage based on enzymatic, microbial, and metabolism analysis

The flavor alterations in bighead carp subjected to varying storage temperatures and the underlying metabolic mechanism were elucidated. Analysis of volatile flavor compounds, electronic nose, free amino acids, ATP-related compounds, and sensory evaluations uncovered a progressive flavor deterioration during storage, especially at 25 °C. Metabolomics-based flavor relating component profiling analysis showed that free fatty acids formed various fatty aldehydes including (E, E)-2,4-heptadienal and nonanal under lipoxygenase catalysis. Alcohol dehydrogenase and alcohol acyltransferases were intimately involved in alcohol and ester generation, while alkaline phosphatase, 5'-nucleotidase, and acid phosphatase were closely associated with IMP, Hx, and HxR conversion, respectively. Aeromonas, Serratia, Lactococcus, Pseudomonas, and Peptostreptococcus notably influenced flavor metabolism and enzyme activities. The metabolism disparities of valine, leucine, isoleucine, lysine, and α-linolenic acid could be the primary factors contributing to flavor metabolism distinctions. This study offers novel insights into the flavor change mechanisms and potential regulation strategies of bighead carp during storage.

Chitosan/polyvinyl alcohol food packaging incorporated with purple potato anthocyanins and nano-ZnO: Application on the preservation of hairtail (Trichiurus haumela) during chilled storage

The objective of this work was to evaluate the potential application of chitosan/PVA food packaging films incorporating nano-ZnO and purple potato anthocyanins for preserving chilled hairtail pieces. The hairtail pieces were packaged with chitosan/PVA (CP) and chitosan/PVA/nano-ZnO/purple potato anthocyanins (CPZP), respectively, and Control named without any packaging. The changes in pH, total volatile basic nitrogen (TVB-N), total bacterial colony (TVC), thiobarbituric acid (TBA), color value, and sensory evaluation scores of hairtail pieces were periodically determined. Notably, pH, TVC, TVB-N and TBA values of CPZP group on day 15 were 11.67 %, 23.71 %, 80.73 %, and 35.07 %, respectively, lower than Control group. In addition, CPZP group also performed the best in color and sensory evaluation. These results indicated that CPZP, an active food packaging, could extend the shelf-life of hairtail at least 6 days. Overall, chitosan/PVA food films incorporated with nano-ZnO and purple potato anthocyanins (180 mg/100 mL) provides a potential application in food preservation.

Effects of different slaughtering methods on the energy metabolism, apoptosis process and quality of grouper (Epinephelus fuscoguttatus) during cold storage at 4 °C

BACKGROUND

The aquatic processing industry is increasingly aware of the need to ensure that slaughtering is carried out under high welfare standards, so there is a need to explore the impact of slaughter methods on fish fillets. This study aimed to investigate the effects of different slaughtering methods (M1, lethality by hammering; M2, gas mixture causing death; M3, lethality by clove oil anesthesia + ice slurry; M4, lethality by ice slurry; M5, lethality by gradient cooling) on the energy metabolism, apoptosis and flesh mass in grouper (Epinephelus fuscoguttatus).

RESULTS

Therefore, 120 fish (24 per treatment) were slaughtered by the five methods. The results showed that the succinate dehydrogenase (SDH) enzyme activity of M5 sample was higher. The serum glucose level of M2 samples and DAPI staining fluorescence of M2 samples were the highest, indicating that the stress response of M2 was strong. In addition, the texture, pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA) and K value results showed M5 samples had better flesh quality.

CONCLUSION

Gradient cooling lethality had the least effect on oxidative damage and apoptosis in grouper during cold storage as the gradient cooling lethality had the least effect on antioxidant enzyme activities. © 2024 Society of Chemical Industry.

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.

Comparative Evaluation of Flavor and Sensory Quality of Coffee Pulp Wines

Coffee pulp wines were produced through the mixed fermentation of Saccharomyces cerevisiae, and the flavor and sensory characteristics were comparatively evaluated. A total of 87 volatile components were identified from five coffee pulp wines, of which 68 were present in all samples, accounting for over 99% of the total concentration. The sample fermented contained significantly higher levels of volatile metabolites (56.80 mg/g). Alcohols (22 species) and esters (26 species) were the main flavor components, with the contents accounting for 56.45 ± 3.93% and 31.18 ± 4.24%, respectively, of the total. Furthermore, 14 characteristic components were identified as potential odor-active compounds, contributing to sweet and floral apple brandy flavor. Although the characteristic components are similar, the difference in the content makes the overall sensory evaluation of the samples different. The samples formed by fermentation of four strains, which obtained the highest score (86.46 ± 0.36) in sensory evaluation, were further interpreted and demonstrated through the Mantel test. The results of the component analysis were effectively distinguished by OPLS-DA and PCA, and this validation was supported by sensory evaluation. The research results provided a technical reference for the production of coffee pulp wines.

Effect of Specific Spoilage Organisms on the Degradation of ATP-Related Compounds in Vacuum-Packed Refrigerated Large Yellow Croaker (Larimichthys crocea)

This study examined the spoilage potential of specific spoilage organisms on the degradation of adenosine triphosphate (ATP)-related compounds in vacuum-packed refrigerated large yellow croaker. The total viable count (TVC), ATP-related compounds and related enzymes of vacuum-packed refrigerated large yellow croaker inoculated with different bacteria (Pseudomonas fluorescens and Shewanella putrefaciens) were characterized using the spread plate method, high-performance liquid chromatography and assay kits, respectively. Results indicated that the TVC for both control and Shewanella putrefaciens groups reached spoilage levels at days 9 and 15, respectively. The changes of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and adenosine deaminase activity across all groups showed no significant difference attributable to microbial growth. The results suggested that ATP to inosine monophosphate (IMP) degradation primarily occurs via fish's endogenous enzymes, with minimal microbial involvement. On day 12, the IMP content in fillets inoculated with Pseudomonas fluorescens (0.93 μmol/g) was half higher than in those inoculated with Shewanella putrefaciens (0.57 μmol/g). Both spoilage organisms facilitated IMP degradation, with Shewanella putrefaciens making a more substantial contribution. Analysis of K values and correlation coefficients revealed that Shewanella putrefaciens was the primary factor in the freshness loss of refrigerated vacuum-packed large yellow croaker. These findings offer a reference for understanding quality changes in refrigerated large yellow croaker, especially regarding umami degradation at the microbial level.

Characterization of chitosan film incorporated pine bark extract and application in carp slices packaging

Active films based on chitosan incorporated with pine bark extract (PBE) were prepared and characterized. Subsequently, these films were utilized for packaging carp slices in refrigerated storage at 4 ± 1 °C. Analysis of the physicochemical properties and biological activity of the active films revealed that, except for water content, all assessed indices showed an increasing trend with an increase in the amount of supplemental PBE. As this trend progresses, scanning electron microscopy (SEM) analysis revealed deposition on the film surface accompanied by transverse lines and fractures, while the color of the film gradually changed from light yellow to reddish-brown. Fourier transform infrared spectroscopy (FTIR) indicated that the phenolic hydroxyl groups in PBE interacted with the hydrogen in the amino groups of chitosan molecules to form non-covalent bonds. X-ray diffraction analysis (XRD) showed that the reaction between PBE and chitosan altered the crystalline structure of chitosan molecules. Moreover, the analysis of the effects of active films on the pH, water-holding capacity, thiobarbituric acid values, and the total bacterial counts of carp slices revealed that in terms of preservation, films containing 30 % PBE were the most effective, using which the shelf life of carp slices could be extended by 50 %.

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.

Effect of Neutral Protease on Freshness Quality of Shucked Pacific Oysters at Different Storage Conditions

The aim of this study was to investigate the effect of neutral protease treatment on the biochemical properties of various parts of Pacific oysters (Crassostrea gigas) under different storage conditions. The mechanism of quality degradation in the mantle, adductor muscle, gill, and trunk of treated oysters stored at -1.5 °C (superchilling) or 4 °C (refrigeration) for several days using different storage methods was studied. The results showed that the oyster treated with the enzyme exhibited higher glycogen content, flavor nucleotide content, and sensory scores compared to the control group. Superchilling at -1.5 °C was observed to slow the increase in total volatile basic nitrogen (TVB-N), total viable count (TVC), and pH, while maintaining sensory scores better than refrigeration at 4 °C. Both wet superchilling (WS) and dry exposed superchilling (DeS) methods effectively preserved freshness and quality at -1.5 °C. The freshness of the oysters' body trunk changed most significantly. K value, K' value, and AEC value, as the evaluation indexes of oyster freshness, were affected by the storage medium. Therefore, neutral protease enhances the flavor of oysters in a short time, and oysters stored in wet superchilling or dry exposed superchilling conditions have an extended shelf life.

Shelf-life extension of Pacific white shrimp (Litopenaeus vannamei) using sodium alginate/chitosan incorporated with cell-free supernatant of Streptococcus thermophilus FUA 329 during cold storage

Seafood is highly perishable and has a short shelf-life. This study investigated the effect of chitosan and alginate (CH-SA) coating combined with the cell-free supernatant of Streptococcus thermophilus FUA329 (CFS) as a preservative on the quailty of white shrimp (Litopenaeus vannamei) refrigerated at 4° for 0, 3, 6, 9, 12, 15 days. Freshly shrimps were randomly divided into four groups: the CFS group (400 mL); the CH-SA group (1% chitosan/1% alginate); the CFS-CH-SA group (1% chitosan/1% alginate with 400 mL CFS) are treatment groups, and the control group (400 mL sterile water). The CFS-CH-SA coating effectively suppressed microbial growth total viable count and chemical accumulation (pH, total volatile basic nitrogen, thiobarbituric acid reactive substance) compared with the control. Additionally, the CFS-CH-SA coating improved the texture and sensory characteristics of shrimp during storage. The coated shrimp exhibited significantly reduced water loss (p < 0.05). The combination of CH-SA coating with CFS treatment can extend the shelf life of shrimp. PRACTICAL APPLICATION: Recently, edible films have received more consideration as a promising method to enhance the shelf life of seafood. The presence of Lactic acid bacteria metabolites in edible films reduces spoilage and improves consumer health. Our findings encourage the application of edible coating incorporated with cell-free supernatant of Streptococcus thermophilus FUA 329 to design multifubctional foods and preserve the qualities of shrimp.

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.

Antibacterial properties of hexanal-chitosan nanoemulsion against Vibrio parahaemolyticus and its application in shelled shrimp preservation at 4 °C

Vibrio parahaemolyticus has been considered as the leading pathogen associated with seafood-borne disease. Hexanal possesses antibacterial property but the hydrophobicity and volatility limit its application. The purpose of this study was to prepare hexanal-chitosan nanoemulsion (HCN), investigate its antibacterial ability against V. parahaemolyticus, and examine the combination of HCN with sodium alginate coating on the quality attributes of shrimp during cold storage. The mean droplet size of HCN fabricated by ultrasonic emulsification was 91.28 nm. HCN showed regular spherical shape and exhibited good centrifugation stability and storage stability at 4 °C. HCN exerted anti-V. parahaemolyticus effect with the minimum inhibitory concentration and minimal bactericidal concentration of both 5 mg/mL. Furthermore, HCN induced morphological changes and destroyed bacterial membrane, resulting in cell death. The results of preservation test showed that HCN alone and its combination with sodium alginate coating effectively retarded the quality deterioration and microbial spoilage of shelled shrimps during refrigerated storage. Comparatively, the combination treatment exhibited better preservation effect. The present study suggested that HCN prepared by ultrasonic emulsification is an effective alternative to control V. parahaemolyticus contamination in seafood and also shows great application potential in the quality maintaining of seafood during cold storage.

Effect of tea polyphenols on chitosan packaging for food preservation: Physicochemical properties, bioactivity, and nutrition

Chitosan packaging has been widely studied for food preservation, the application of which is expanded by the incorporation of tea polyphenols. This paper reviews the influence of tea polyphenols incorporation on chitosan-based packaging from the perspectives of physicochemical properties, bioactivity used for food preservation, and nutritional value. The physicochemical properties included optical properties, mechanical properties, water solubility, moisture content, and water vapor barrier property, concluding that the addition of tea polyphenols improved the opacity, water solubility, and water vapor barrier property of chitosan packaging, and the mechanical properties and water content were decreased. The bioactivity used for food preservation, that is antioxidant and antimicrobial properties, is enhanced by tea polyphenols, improving the preservation of food like meat, fruits, and vegetables. In the future, efforts will be needed to improve the mechanical properties of composite film and adjust the formula of tea polyphenols/chitosan composite film to apply to different foods. Besides, the identification and development of high nutritional value tea polyphenol/chitosan composite film is a valuable but challenging task. This review is expected to scientifically guide the application of tea polyphenols in chitosan packaging.

Investigation of the Alternations in Lipid Oxidation and Lipase Activity in Air-Dried Hairtail (Trichiurus lepturus) during Chilled Storage

The effects of water content and water activity on the lipid stability of air-dried hairtail (Trichiurus haumela) were investigated during chilled storage. Air-dried hairtail samples with high and low water contents were comparatively analyzed over 8 days of storage at 4 °C. The results indicated that the decreases in water activity and increases in the NaCl content significantly inhibited lipid oxidation in the air-dried hairtail samples. The peroxidation value (PV), conjugated diene value (CD), thiobarbituric acid reactive substance (TBARS) value, and p-anisidine value (p-AnV) of the air-dried hairtail significantly increased with the extension of storage time. The low water content significantly inhibited the activity of neutral and alkaline lipase, in addition to lipoxygenase, and retarded the rapid increases in the non-esterified fatty acid (NEFA) content in the hairtail samples. The correlation analysis results showed that the TBARS, p-AnV, and lipase activity were positively correlated in the air-dried hairtail samples, and the lower water content significantly inhibited the progress of lipid oxidation. This study offers a theoretical framework for the industrial processing and storage of air-dried hairtail products.

Flavor improving effects of cysteine in xylose-glycine-fish waste protein hydrolysates (FPHs) Maillard reaction system

A promising way to utilize fish by-products is to develop hydrolysis of fish proteins with enzymes. The obtained fish protein hydrolysates (FPHs) are rich in peptides and amino acids, but bitterness and aroma defects impede further utilization of FPHs. The present study adopted Maillard reaction to improve FPHs' flavor and illustrated the role of cysteine in this system. We investigated the impact of cysteine (0, 0.25%, 0.5%, 0.75%, and 1%) on the browning intensity, free amino acids (FAAs), molecular weight distribution, structure of MRPs, volatile compounds changes and organoleptic characteristics of xylose-glycine-FPHs Maillard reaction systems. Results showed that the addition of cysteine lowered the browning degree of Maillard reaction products (MRPs) by inhibiting the cross-linking of small peptides and reducing the production of melanin. GC-MS and GC-IMS analysis indicated that cysteine inhibited the formation of furans and nitrogen-containing compounds and facilitated the formation of sulfur-containing compounds contributing to the meaty flavor. Sensory analysis revealed that 0.25-0.75% range of cysteine increased the meaty, caramel, umami, mouthfulness and salty notes, and caused a decrease in bitter taste of the MRPs as confirmed by GC-MS. A highly significant correlation between the organoleptic characteristics and physicochemical indicators of MRPs was found by Mantel test. These results elucidated the influence of cysteine on the formation of Maillard reaction products and will help improve the flavor profile of meat flavorings.

Effect of vacuum and modified atmosphere packaging on moisture state, quality, and microbial communities of grouper (Epinephelus coioides) fillets during cold storage

The study aimed to assess the impact of different packaging methods on the moisture state, quality, and microbial composition of grouper fillets. The grouper fillets were packaged under the following four conditions: vacuum packaging (VP), 70% CO2/30% N2 (MAP1); 60% CO2/30% N2/10% O2 (MAP2); 40% CO2/30% N2/30% O2 (MAP3). Physicochemical and microbiological parameters were evaluated during 21 days of cold storage. The result demonstrated that MAP was effective in inhibiting microbial growth and accumulation of total volatile basic nitrogen (TVB-N), while also maintaining the water-holding capacity (WHC) of grouper fillets. Additionally, MAP1 effectively inhibited lipid and protein oxidation and protected the secondary structure of myofibrils compared to MAP2 and MAP3, with MAP1 samples having the lowest thiobarbituric acid reactive substances (TBARS) value (0.009-0.04 MDA/kg) and carbonyl content (0.20-0.26 μmol/g) and the highest sulfhydryl content (0.25-0.49 μmol/g) during cold storage. The results of high-throughput sequencing revealed that the presence of oxygen in the packaging system significantly influenced bacterial succession. Over time, Carnobacterium gradually became the dominant genera of fillets stored in MAP, and the presence of oxygen in MAP2 and MAP3 accelerated this transition by 9 days, compared to MAP1. In contrast, Enterobacteriaceae and Carnobacterium were the main dominant genera in VP. Remarkably, Enterobacteriaceae were virtually absent in MAP2 and MAP3 during storage, suggesting that the presence of oxygen exerted a significant inhibitory effect on Enterobacteriaceae. This study provides valuable insights into the application of MAP in the preservation of grouper fillets.

Chitosan coating with grape peel extract: A promising coating to enhance the freeze-thaw stability of beef

This study investigated the effect of chitosan coating with grape peel extracts (CH + GPE) on the physiochemical properties, protein and lipid oxidation, microstructure, and bacterial community diversity of beef during freeze-thaw (F-T) cycles. The results indicated that the CH + GPE groups had lower pH values, total aerobic count, total volatile base nitrogen, and thiobarbituric acid reactive substance values and better protection against color, water holding capacity, and sensory quality after five F-T cycles. The CH + GPE coating effectively inhibited beef microstructure destruction during the F-T cycles. High-throughput sequencing analysis revealed that the CH + GPE coating contributed to a decline in the bacterial diversity of beef and inhibited the growth of pathogenic bacteria. Interestingly, the CH + GPE coating affected the correlation between quality parameters and bacteria in beef. Consequently, the CH + GPE coating can be used as a novel packaging for preventing the loss of frozen meat quality due to temperature fluctuations.

Highly biologically active and pH-sensitive collagen hydrolysate-chitosan film loaded with red cabbage extracts realizing dynamic visualization and preservation of shrimp freshness

Accurate and efficient detection of food freshness is of great significance to guarantee food safety. Herein, pH sensitive colorimetric films with considerable biological activities have been prepared by combining red cabbage anthocyanin extracts (RCE) with collagen hydrolysate-chitosan (CH-CS) matrix film. The formation mechanism of CH-CS-RCE films was discussed by SEM, FT-IR and XRD, which showed that RCE was successfully fixed in CH-CS film through hydrogen bonding and electrostatic interaction. The CH-CS-RCE films exhibited good mechanical properties, high barrier ability, excellent thermal stability, significant antioxidant and antimicrobial activity, and especially sensitive response to pH and ammonia. Fickian diffusion was the main mechanism for the release of RCE from CH-CS-RCE films and such release mechanism facilitated the maintenance of functional features of films. During the storage of shrimps at 4 °C, CH-CS-RCE2% showed a remarkable preservation effect on shrimps, and their shelf life was prolonged from 2 d to 5 d. Furthermore, CH-CS-RCE2% provided a dynamic visual color switching to detect the freshness of shrimp, realizing real-time monitoring of freshness. Color information (RGB) extracted via smartphone APP was used to enhance the accuracy and universality of freshness indication. Thus, this multifunctional film has great potential in food preservation and freshness monitoring.