Evaluation of negative behaviors for single specific spoilage microorganism on little yellow croaker under modified atmosphere packaging: Biochemical properties characterization and spoilage-related volatiles identification

Effect of air-conditioned packaging combined with temperature fluctuations on the preservation of mandarin fish (Siniperca chuatsi)

The objective of this study was to evaluate the impact of diverse packaging techniques on the moisture content, quality, microbiological profile and volatile compounds of mandarin fish (Siniperca chuatsi) fillets. Mandarin fish fillets were packaged in accordance with three distinct conditions: AP (Air packaging), MAP 1 (40 % CO2/45 % N2/15 % O2) and MAP 2 (50 % CO2/35 % N2/15 % O2) and stored at TC (Constant temperature at 4 °C) and TF (Temperature fluctuation at 4 °C and 8 °C), respectively. Results demonstrated that MAP effectively inhibited microbial growth, retarded pH increase, and reduced accumulation of TVB-N, TMA, and MDA. On the 18th day, the constant-temperature MAP 2 group exhibited optimal preservation, with TVB-N (14.70 mg/kg), TMA (2.74 mg/kg), and MDA (38.36 mmol/mg) lower than those in the fluctuating-temperature AP group (TVB-N: 115.07 mg/kg; TMA: 2.81 mg/kg; MDA: 84.39 mmol/mg). It proved that temperature fluctuations accelerated the spoilage process of mandarin fish.

Transcriptome Analysis Reveals the Molecular Mechanism of Pseudomonas with Different Adhesion Abilities on Tilapia Decay

This study aimed to investigate the molecular mechanism of Pseudomonas with varying adhesion capabilities to Tilapia's intestinal mucus influence the spoilage potential of Tilapia. Sodium chloride(NaCl) was used as an environmental factor to regulate Pseudomonas' adhesion ability. After being exposed to 3.5% NaCl stress, the PS01 strain with low adhesion showed an enhancement in adhesion ability, while the LP-3 strain with high adhesion exhibited a decrease. Correspondingly, the expression of critical adhesion genes, such as flgC, fliC, and cheB, was found to be altered. LP-3, with high adhesion ability, was observed to promote a relative increase in Nocardioides and Cloacibacterium in fish intestines. This led to the production of more volatile compounds, including 2-octen-1-ol Z, 2,3-Octanedione, and Eicosane, thus deepening the spoilage of tilapia. LP-3, with reduced adhesion ability after NaCl regulation, showed a diminished capacity to cause fish spoilage. Transcriptomics analysis was used to examine two Pseudomonas strains that exhibited different adhesion abilities, leading to the identification of an adhesion regulatory network involving flagellar assembly regulation, bacterial chemotaxis, quorum sensing, two-component systems, biofilm formation, and bacterial secretion systems. This study identified the Pseudomonas adhesion regulatory pathway and determined 10 key adhesion-related genes.

Changes in flavor quality of marinated Chinese mitten crab (Eriocheir sinensis) with vacuum pack during cold storage

In order to study the pattern of changes in quality of marinated Chinese mitten crabs (Eriocheir sinensis) during cold storage, three aspects of sensory, taste and odor were investigated. Sensory evaluation and total volatile basic nitrogen (TVB-N) were measured in viscera and abdomen muscle at 0, 7, 15 and 30 days of storage at 4°C. Sensory scores significantly declined at 15 d, coinciding with TVB-N levels exceeding 25 mg N/100 g. Taste profiling demonstrated distinct changes over the storage period. Arginine (Arg) in viscera and abdomen muscle decreased by 18.16 % and 43.26 %, respectively, while adenosine monophosphate (AMP) dropped to 48.46 and 22.22 mg/100 g after 15 days, contributing to loss of umami. Based on the correlation analysis, it was known that bitterness was related to freshness, with tyrosine (Tyr), phenylalanine (Phe), hypoxanthine (Hx) and hypoxanthine riboside (HxR) being more significant contributors to the bitterness. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis attributed late-stage undesirable odors to the production of aldehydes and ketones, particularly heptanone, 3-hydroxy-2-butanone, heptanal and glutaraldehyde. This study provided valuable guide for improving the flavor quality of Chinese mitten crabs in the field of prepared dish.

Effects of interactions between microorganisms and lipids on inferior volatile compound production during cold storage of grouper (Epinephelus coioides)

The interaction between microorganisms, proteins, and lipids plays a critical role in the odor production of fish. To explore the specific impact of the interaction between lipids and microorganisms on the overall odor of grouper, this study excluded the influence of proteins and assessed lipid (POV and TBARS) and microbial characteristics (biofilm mass and ATP content) in lipid solutions. The Results showed that microbial growth and lipid oxidation mutually promote each other. Lipidomics analysis identified 44 differential lipids, and microbial diversity analysis pinpointed five key microorganisms (Carnobacterium, Pseudomonas, Gluconacetobacter, Vagococcus, and Shewanella). Furthermore, 20 key volatile compounds (VOCs) related to odor changes in the grouper lipid solution were identified using HS-SPME-GC-MS. Correlation network analysis revealed potential microbial and lipid contributions to VOC categories, including alcohols, aldehydes, ketones, and nitrogen- and sulfur-containing compounds. This study provides new insights into the roles of microorganisms and lipids in flavor formation, offering valuable knowledge for improving seafood quality control.

Microbial composition of spoiled irradiated ready-to-eat chicken feet and their spoilage characteristics

The spoilage of irradiated ready-to-eat chicken feet (RTECF) seriously affects the food's quality, resulting in package swelling and off-flavors, both of which are highly undesirable to stakeholders and consumers. To investigate the spoilage characteristics of irradiated RTECF and the microorganisms responsible for the spoilage and swelling, the changes in physicochemical properties, microbial community, and volatile organic compounds (VOCs) between normal and spoiled RTECF were evaluated. Compared with normal samples, the spoiled RTECF showed a higher pH value and total volatile basic nitrogen (TVB-N) value, lower color value, and texture features (P < 0.05). Acinetobacter, Pseudomonas, Lactobacillus, and Candida were the dominant genera responsible for RTECF spoilage as confirmed through both culture-dependent methods and high-throughput sequencing (HTS). The results of the verification for gas-producing strains showed that Lactobacillus brevis could cause RTECF packaging to swell. A total of 20 key VOCs were identified using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results of Pearson correlation analysis (|r|>0.8, P < 0.05) showed that 12 dominant core microbial genera had a significant effect on the flavor of RTECF before and after spoilage. This study provides a theoretical reference for solving the problem of RTECF spoilage and improving the overall quality of RTECF products.

Mechanisms of polyphenols on quality control of aquatic products in storage: A review

Aquatic products are easily spoiled during storage due to oxidation, endogenous enzymes, and bacteria. At the same time, compared with synthetic antioxidants, based on the antibacterial and antioxidant mechanism of biological agents, the development of natural, nontoxic, low-temperature, better-effect green biological preservatives is more acceptable to consumers. The type and molecular structure of polyphenols affect their antioxidant and antibacterial effectiveness. This review will describe how they achieve their antioxidant and antibacterial effects. And the recent literature on the mechanism and application of polyphenols in the preservation of aquatic products was updated and summarized. The conclusion is that in aquatic products, polyphenols alleviate lipid oxidation, protein degradation and inhibit the growth and reproduction of microorganisms, so as to achieve the effect of storage quality control. And put forward suggestions on the application of the research results in aquatic products. We hope to provide theoretical support for better exploration of the application of polyphenols and aquatic product storage.

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.

Changes in the Quality and Microbial Communities of Precooked Seasoned Crayfish Tail Treated with Microwave and Biological Preservatives during Room Temperature Storage

The qualities of precooked foods can be significantly changed by the microorganisms produced during room temperature storage. This work assessed the effects of different antibacterial treatments (CK, without any treatment; microwave treatment, MS; microwave treatment and biological preservatives, MSBP) on the physicochemical properties and microbial communities of precooked crayfish tails during room temperature storage. Only the combination of microwave sterilization and biological preservatives significantly inhibited spoilage, as evidenced by the total viable count (4.15 log CFU/g) after 3 days of room temperature storage, which satisfied the transit time of most logistics companies in China. Changes in pH and TVB-N were also significantly inhibited in the MSBP group compared with those in the CK and MS groups. More than 30 new volatile compounds were produced in the CK groups during room temperature storage. However, in the MSBP groups, the volatile compounds were almost unchanged. The correlations between the microbial composition and volatile compounds suggested that specific bacterial species with metabolic activities related to amino acid, energy, cofactor, and vitamin metabolism, as well as xenobiotics biodegradation and metabolism, were responsible for the changes in volatile compounds. These bacteria included Psychrobacter, Arthrobacter, Facklamia, Leucobacter, Corynebacterium, Erysipelothrix, Devosia, Dietzia, and Acidovorax. Overall, our findings provide a foundation for the development of strategies to inhibit spoilage in precooked crayfish tails stored at room temperature.

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.

Effects of deletion of siderophore biosynthesis gene in Pseudomonas fragi on quorum sensing and spoilage ability

Siderophores are important factors in the spoilage process of Pseudomonas fragi, considered to be one of the main spoilage bacterium of tuna, and the secretion of siderophores is regulated by quorum sensing (QS). This study aimed to construct a mutant with the deletion of the siderophore synthetase gene of P. fragi (MS-10), and to explore its effects on the growth, QS, and spoilage potential of P. fragi. The results showed that the deletion of the siderophore biosynthesis gene slowed down the growth rate of the strain. The apoptosis rate increased by 27.7 % compared with that of the wild-type strain at 4 °C for 48 h. Biofilm formation, extracellular protease expression, and signal molecule production were all significantly lower in the mutant strain compared with the wild-type strain. The total viable count and the histamine content showed that the tuna sterile fish block inoculated with the wild-type strain exceeded the acceptable standards by 5 days and was completely spoiled by 7 days, whereas the mutant strain exceeded the acceptable standards by 6 days and was completely spoiled by 9 days. The pH, texture, and other indicators showed that the variation range of the mutant strain was lower than that of the wild-type strain. The deletion of the siderophore biosynthesis gene reduced the spoilage ability of P. fragi. Based on the results, the development of novel preservation agents targeting the control of the siderophore biosynthesis gene could be a new idea for the preservation of aquatic products.

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.

Effects of Sous Vide Cooking on the Physicochemical and Volatile Flavor Properties of Half-Shell Scallop (Chlamys farreri) during Chilled Storage

This study explored the effects of sous vide (SV) cooking treatments on the physicochemical quality and volatile flavor of half-shell scallop (Chlamys farreri) during 30 d of chilled storage. The vacuum-packed scallop samples were cooked at 70 °C (SV-70) and 75 °C (SV-75) and maintained for 30 min. The samples were compared with the positive control (cooked at 100 °C for 10 min, CK). The results indicate that the total volatile basic nitrogen (TVBN), pH, texture, and malondialdehyde (MDA) content gradually increased, while the myofibrillar protein (MP) extraction rate of the CK, SV-70, and SV-75 samples significantly decreased with increasing chilled storage time. Significantly, the SV cooking treatments maintained a much higher water-holding capacity of scallop muscle, compared with the conventional cooking process at 100 °C. Additionally, the SV-75 cooking treatment maintained relatively stable TVBN, pH, and MDA content, springiness, and shearing force properties of scallop samples, especially during 0-20 d of storage. Volatile flavor analysis showed that a total of 42 volatile organic compounds (VOCs) were detected in the scallop samples, and there were no considerable differences in these VOCs between the CK and SV-75 cooked samples (0 d). Overall, the SV cooking treatments effectively maintained acceptable and stable physicochemical and volatile flavor properties of half-shell scallop samples during chilled storage.

Response to Cold Adaption in Acinetobacter johnsonii XY27 from Spoiled Bigeye Tuna (Thunnus obesus): Membrane Protein Composition and Protein Biomarker Identification by Proteomics

Acinetobacter johnsonii is one of the major food-spoilage bacteria and can survive under cold stress. In this study, the membrane composition, membrane permeability, and energy transduction of A. johnsonii XY27 cultured at 4 and 30 °C were examined comparatively by flow cytometry combined with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. The Na⁺/K⁺ATPase activity, alkaline phosphatase and ATPase activity, fluorescence intensity, and cell viability in A. johnsonii XY27 increased with the decrease in cultivation temperature. The polyunsaturated fatty acid and monounsaturated fatty acids have a higher content in A. johnsonii XY27 cultured at 4 °C compared to that cultured at 30 °C, in which the contents of methyl palmitoleate, methyl myristoleate, and methyl oleate increased dramatically with decreasing temperature. Comparative proteomics analysis revealed that 31 proteins were downregulated and 4 proteins were upregulated, in which catalase-peroxidase 1 and cold shock proteins as biomarker proteins could effectively control A. johnsonii during cold adaptation.

AI-2/Lux-S Quorum Sensing of Lactobacillus plantarum SS-128 Prolongs the Shelf Life of Shrimp (Litopenaeus vannamei): From Myofibril Simulation to Practical Application

Retarding the protein deterioration of shrimp during storage is important for maintaining its quality. Lactobacillus plantarum SS-128 (L. plantarum SS-128) is a biocontrol bacterium that can effectively maintain the fresh quality of food. This research establishes a myofibril simulation system and refrigerated control system to explore the impact of L. plantarum SS-128 on the quality and shelf life of refrigerated shrimp (Litopenaeus vannamei). Through the bacterial growth assay and AI-2 signal molecule measurement, the effect of the AI-2/LuxS quorum sensing (QS) system of L. plantarum SS-128 and shrimp spoilage bacteria was established. In the myofibril simulation system, a study on protein degradation (dimer tyrosine content, protein solubility, sulfhydryl content, and carbonyl content) showed that adding L. plantarum SS-128 effectively slowed protein degradation by inhibiting the growth of food pathogens. The application to refrigerated shrimp indicated that the total volatile basic nitrogen (TVB-N) value increased more slowly in the group with added L. plantarum SS-128, representing better quality. The total viable count (TVC) and pH results exhibited similar trends. This study provides theoretical support for the application of L. plantarum SS-128 in storing aquatic products.

Effect of CO2 on the spoilage potential of Shewanella putrefaciens target to flavour compounds

To investigate the regulation mechanism of CO₂ (0% CO₂, 20% CO₂, 60% CO₂, and 100% CO₂) on the spoilage potential of S. putrefaciens target to flavour compounds, the metabolic activity of S. putrefaciens and the changes in flavour compounds extracted from inoculated large yellow croakers were evaluated. Results showed that CO₂ significantly reduced biofilm formation capacity and suppressed synthesis of intracellular adenosine triphosphate (ATP). The production of unpleasant flavour compounds, such as total volatile basic nitrogen (TVB-N), trimethylamine (TMA), inosine (HxR), hypoxanthine (Hx), histidine, lysine, histamine, putrescine, 1-octen-3-ol, hexanal and benzaldehyde, was inhibited by CO₂. The hydrolysis and oxidation of lipid in CO₂-treated samples were alleviated and unsaturated fatty acids (UFAs) were in a higher percentage. In summary, CO₂ efficiently reduced the spoilage potential of S. putrefaciens and contributed to better flavour quality of samples during 4 °C storage. A more effective inhibition by 100% CO₂ was observed.

Spoilage of tilapia by Pseudomonas putida with different adhesion abilities

Four Pseudomonas putida strains isolated from spoiled tilapia were divided into three adhesion abilities—high, medium, and low—by an in vitro mucus model. Four strains had no significant difference in spoilage ability to the inoculated fish fillets. However, according to the in vivo experiment, the spoilage caused by the four P.putida was positively correlated with their adhesion abilities. High adhesion strains not only caused more TVB-N in chilled fish, but also activated the spoilage activity of intestinal flora. The diversity of intestinal flora and the changes in volatile components in fish were detected by high-throughput sequencing and SPME-GC/MS. The strains with high adhesion abilities significantly changed the intestinal flora, which led to a significant increase in low-grade aldehydes, indole, and esters in flesh of fish, as well as the production of a fishy and pungent odor. The intestinal adhesion ability of spoilage bacteria was considered the key factor in spoilage of chilled fish.

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A positive correlation between the intestinal adhesion ability of P.putida and the spoilage ability in vivo.

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P.putida affected the intestinal microflora and led to increase in fishy and pungent odor.

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The intestinal adhesion ability of P.putida was considered as a key factor in spoilage.

Chitosan-grafted-phenolic acid copolymers against Shewanella putrefaciens by disrupting the permeability of cell membrane

Chitosan (CS) is a kind of high molecular polymer with antibacterial properties. A copolymer with high bacteriostatic activity can be formed by grafting phenolic acid compounds into the chitosan molecular chain, which can inhibit the growth of dominant spoilage bacteria in aquatic products. The study aimed to investigate the antibacterial effect and mechanism of chitosan-grafted-phenolic acid copolymers on Shewanella putrefaciens (S. putrefaciens). CS-grafted-protocatechuic acid (CS-g-PA) and CS-grafted-gallic acid (CS-g-GA) were attained by EDC/NHS coupling reaction. The antibacterial tests indicated that CS-g-PA and CS-g-GA had the same minimum inhibitory concentration (MIC) (1.25 mg/mL) and minimum bactericidal concentration (MBC) (5.0 mg/mL) against S. putrefaciens. According to the change trend of growth curve, the growth of S. putrefaciens was significantly restrained under 2MIC graft copolymers (P < 0.05). Moreover, the increment of alkaline phosphatase (AKPase) activity and electrical conductivity demonstrated that the cell wall and membrane permeability of S. putrefaciens were damaged respectively. In addition, the increase of lactate dehydrogenase (LDHase) activity, protein and nucleic acid absorbance and the decrease of adenosine triphosphatase (ATPase) activity suggested that the cell membrane was incomplete and poor fluidity. The irregular shape of bacteria and the outflow of intercellular contents were also observed from scanning electron microscope (SEM). The above results manifested a great potential of CS-g-PA and CS-g-GA for use as food preservatives to aquatic products.