Fish Spoilage Research Articles

Effects of Gamma Irradiation on Inhibition of Urease Activity and Fishy Smell in Mackerel (Scomber japonicus) during Refrigerated Storage.

In this study, gamma-irradiated mackerel (Scomber japonicus) meat was stored in a refrigerator for 20 days to examine the physicochemical changes related to fishy smell. The effect of gamma irradiation on the inhibition of the activity of crude urease extracted from Vibrio parahaemolyticus was also evaluated. Increased levels of trimethylamine (TMA) and volatile basic nitrogen (VBN) content, which are the main components causing fishy smell, were significantly reduced by day 20 of storage after gamma irradiation, indicating that freshness was maintained during storage. The ammonia nitrogen contents of 3, 7, 10, and 20 kGy gamma-irradiated groups were significantly decreased by 6.5, 15.2, 17.4, and 23.9%, respectively, compared to non-irradiated groups on day 20 of storage. In addition, urease activity decreased in a gamma irradiation intensity-dependent manner. Volatile organic compounds (VOCs) were measured during the storage of gamma-irradiated mackerel meat. The contents of ethanol, 2-butanone, 3-methylbutanal, and trans-2-pentenal, which are known to cause off-flavors due to spoilage of fish, were significantly reduced by day 20 of storage. Therefore, gamma irradiation can be considered useful for inhibiting urease activity and reducing fishy smell during fish storage.

Development and Validation of an RP-HPLC-FLD Method for the Determination of Biogenic Amines after Pre-column Derivatization with a New Pyrazoline Based Reagent, 3- Naphthyl-1-(4-trifluoromethyl)-5-(4-carboxy phenyl)-2-pyrazoline

Application of 3-Naphthyl-1-(4-trifluoromethyl)-5-(4-carboxy phenyl)-2-pyrazoline (NFCP) as a novel fluorigenic label for the derivatization of biogenic amines (BAs) and separation by liquid chromatography (LC) was investigated. Optimum conditions for the pre-column derivatization and chromatographic separation were investigated. The resulting derivatives are fluorescent at λex/λem: 380/460 nm. For the sake of evaluating the efficacy of the proposed analysis of BAs of different nature, the formation of nine NFCP-BAs derivatives was tested individually. Simultaneous derivatization and separation of four BAs (histamine, tyramine, tryptamine, and phenylethylamine) were achieved under the isocratic elution mode. Furthermore, the derivatives were identified by the characteristic product ion obtained during LC-MS/MS analysis. The viability of the method was established by measuring levels of histamine in fresh and spoiled fish samples. Histamine concentrations were found to be 0.4 µgg-1 and 4.1 µgg-1 in fresh and spoiled tuna fish samples respectively. As a simple, reliable, and sensitive pre-column derivatization method, this work provides for future research to develop a novel HPLC method for the analysis of BAs from food samples such as fish and various other matrices by utilizing the new pyrazoline compound.

Synergistic effects of ε-polylysine hydrochloride and gallic acid on Shewanella putrefaciens and quality of refrigerated sea bass fillets

The abundant nutrients of raw sea bass are excellent media for specific microorganisms like Shewanella putrefaciens, which cause fish spoilage. In this study, gallic acid (GA), protocatechuic acid (PA) and chlorogenic acid (CA) were tested for their synergistic antibacterial effects with ε-polylysine hydrochloride (PL). A strong synergistic inhibitory effect against S. putrefaciens was observed in PL and GA treatment. The combination of 1/8 MIC PL and 1/4 MIC GA completely inhibited S. putrefaciens growth and caused cell death. This combination significantly damaged the cell structure, and induced serious leakage of electrolytes, nucleic acid, and protein. GA, PL and PL-GA treatments significantly reduced sensory deterioration, total viable counts, total volatile base nitrogen and thiobarbituric acid value of sea bass fillets during 4 °C storages, with PL-GA showing the best effect. The results suggested that the combination of PL and GA might be an effective preservative to control marine fish spoilage.

Facile mechanochemical fabrication of hybrid pigments with allochroic, antibacterial and superhydrophobic properties based on organo-palygorskite and curcumin

In this study, novel multifunctional durable intelligent hybrid pigments with allochroic, antibacterial, and superhydrophobic properties were facilely fabricated by a cleaner mechanochemical method, in which palygorskite was initially modified with cetyltrimethylammonium bromide to anchor curcumin by semidry grinding, and subsequently coated with organosilanes by one-step modification via semidry grinding. The obtained hybrid pigments were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmittance electron microscopy, EDS mapping, X-ray photoelectron spectroscopy, and the Brunauer–Emmett–Teller method. The density functional theory calculation was also performed to further explore the possible interaction among curcumin and organo-palygorskite. The results confirmed that curcumin was loaded on organo-palygorskite via electrostatic and hydrogen bond interactions. Due to the synergistic effect of the organic modification, the obtained hybrid pigments exhibited excellent antibacterial activity against Staphylococcus aureus with minimal inhibitory concentrations of 0.5 mg/mL. Furthermore, curcumin-loaded organo-palygorskite presented excellent thermal and chemical stability after subsequent modification with organosilanes at different heating temperatures and chemical reagents. The organo-palygorskite/curcumin@polymerized organosilane composites could intelligently monitor fish spoilage in real time based on the reversible allochroic properties of the loaded curcumin. Thus, hybrid pigments are expected to design promising multifunctional food packaging materials with allochroic, antibacterial, and superhydrophobic properties.

Mechanisms underlying the deterioration of fish quality after harvest and methods of preservation

Lipid oxidation and/or protein decomposition caused by endogenous enzymatic activity and microbial contamination have a negative impact on the quality of fish in storage, increasing their perishability. Safe and effective alternative approaches for preserving fish quality and extending their shelf-life have been investigated more intensely over the recent decade, due to concerns about the safety of conventional preservation chemicals and techniques. The present review article provides an overview of the factors responsible for fish spoilage and the mechanisms involved, and then reviews advances in effective measures for preserving fish quality. We provide information on the application of modified atmosphere packaging, the use of natural compounds (e.g., plant/algal extracts, biopolymers, gelatin, microbial-derived compounds, temperature/pressure treatments, and various combinations of these approaches. The impact of these technologies on the resident microbiota of fish is also presented. Bio-safe, effective measures are a critical component of an integrated management approach for extending the shelf-life of harvested fish. The relationship between the resident microbiota and fish quality is especially highlighted. In summary, the review provides information on the mechanisms responsible for the deterioration of fish quality during storage and provides an overview of a variety of methods that are used or being explored to preserve and extend the shelf life and quality of fish, including the use of a combination of approaches (hurdle technology). A discussion of the future research needed to better understand the mechanisms associated with the action of preservation technologies, and the need to develop effective packaging materials is also discussed. • The factors responsible for fish spoilage and the mechanisms involved was presented. • Recent advances in representative measures for preserving fish quality were reviewed. • The relationship between the resident microbiota and fish quality is highlighted. • The need to explore effective packaging materials is discussed. • Hurdle technology is promising for fish preservation.

Genomic Insights into Omega-3 Polyunsaturated Fatty Acid Producing Shewanella sp. N2AIL from Fish Gut.

Simple SummaryThe microbial production of health-beneficial omega-3 fatty acids has gained research attention due to the limitations of availability, sustainability, and contaminants associated with the conventional fish source. Among the marine bacteria, the Shewanella genus is well known for eicosapentaenoic acid (EPA) production along with bioremediation of organic and inorganic pollutants and bioelectricity generation. We report the genome sequence of an EPA-producing bacterium, Shewanella sp. N2AIL, isolated from the gut of a freshwater fish, Tilapia. Analysis of genomic data revealed a variety of antibiotic and stress-responsive genes, metal-reducing genes, and secondary metabolite genes. Overall, the study has provided an understanding of the biosynthetic gene cluster of omega-3 polyunsaturated fatty acids in addition to adaptation strategies of Shewanella sp. N2AIL and could be utilized in developing a strain for the commercial production of EPA.The genus Shewanella is widely distributed in niches ranging from an aquatic environment to spoiled fish and is loaded with various ecologically and commercially important metabolites. Bacterial species under this genus find application in bioelectricity generation and bioremediation due to their capability to use pollutants as the terminal electron acceptor and could produce health-beneficial omega-3 fatty acids, particularly eicosapentaenoic acid (EPA). Here, the genome sequence of an EPA-producing bacterium, Shewanella sp. N2AIL, isolated from the gastrointestinal tract of Tilapia fish, is reported. The genome size of the strain was 4.8 Mb with a GC content of 46.3% containing 4385 protein-coding genes. Taxonogenomic analysis assigned this strain to the genus Shewanella on the basis of average nucleotide identity (ANI) and in silico DNA-DNA hybridization (DDH), phylogenetically most closely related with S. baltica NCTC 10735T. The comparative genome analysis with the type strain of S. baltica revealed 693 unique genes in the strain N2AIL, highlighting the variation at the strain level. The genes associated with stress adaptation, secondary metabolite production, antibiotic resistance, and metal reduction were identified in the genome suggesting the potential of the bacterium to be explored as an industrially important strain. PUFA synthase gene cluster of size ~20.5 kb comprising all the essential domains for EPA biosynthesis arranged in five ORFs was also identified in the strain N2AIL. The study provides genomic insights into the diverse genes of Shewanella sp. N2AIL, which is particularly involved in adaptation strategies and prospecting secondary metabolite potential, specifically the biosynthesis of omega-3 polyunsaturated fatty acids.

Investigation of spoilage in salmon by electrochemical impedance spectroscopy and time-domain terahertz spectroscopy

In this study, Spoilage of salmon was investigated using electrochemical impedance spectroscopy (EIS) and terahertz time-domain spectroscopy (TDS). Salmon tissues were continuously observed for more than 20 h, from fresh to full spoilage. The complex impedance ( Z ) and phase shift ( θ ) of the salmon samples were derived based on the EIS signal. Critical frequency changes, phase shifts, and impedance variations with time at different frequencies were extracted from the data and used as indicators of the freshness of salmon. In the THz TDS analysis, time-domain spectra were recorded in transmission and reflection modes. Four stages of fish spoilage were clearly observed in both the EIS and THz TDS spectra. Although EIS is more sensitive under the current experimental conditions, THz TDS in reflection mode provides a non-invasive and non-destructive way to monitor salmon spoilage, which is practically beneficial for the food quality control industry.

Inhibitory Effect of Rosemary Essential Oil and Its Nanoemulsion on the Formation of Biogenic Amines by Food-Borne Pathogens and Fish Spoilage Bacteria

The effect of nanoemulsions based on rosemary essential oil (BNE) and its purified version (BEO) on the growth of fish spoilage bacteria (P. luteola, P. damselae, V. vulnificus, E. faecalis, S. liquefaciens, and P. mirabilis) and foodborne pathogens (S. Paratyphi A, S. aureus, K. pneumoniae, and E. faecalis) and their biogenic amine formation were investigated in tyrosine decarboxylase broth (TDB) using HPLC method. The flavour compounds of extracted BEO were determined using GC-MS. Physical properties of BNE (viscosity, thermodynamic stability, droplet size, and surface tension) were analysed. Tween 80, BEO, and BNE were inhibitory effects on the growth performances of the pathogenic and spoilage bacteria. Differences in ammonia (AMN) and biogenic amine (BA) production among groups were statistically significant (p<0.05). The highest HIS production was obtained by spoilage E. faecalis (58.76 mg L-1) and the lowest by V. vulnificus (2.29 mg L-1). Almost all other BAs such as PUT, CAD, SPD, and PHEN were formed by pathogens and spoilage groups. S. aureus (143.05-702.88 mg L-1) was the main high tyramine (TYR) producer in TDB. HIS production by V. vulnificus was considerably suppressed in the presence of BNE (p<0.05). Although the effect of treatment groups (Tween 80, BEO, and BNE) varied depending on the bacterial strain and specific amine, all groups generally decreased AMN and BA accumulation by bacteria. Consequently, the results show that all bacteria tested are capable of decarboxylating more than one amino acid and conversion of rosemary oil into nanoemulsion suppressed BA production activity and its nano-form can be used as an alternative antimicrobial agent in processed or packaged fish or food products.

Zero-Waste Approach Applied to Pomegranates for Prolonging Fish Burger Shelf Life.

In this study, the possibility of using whole pomegranate (juice, peel and seeds) according to the zero-waste approach, to prolong fresh fish shelf life, was evaluated. A preliminary antimicrobial in vitro test was carried out with peel and seeds as ground and re-ground powders. Then, the entire fruit, in the right proportions of juice and relative by-products as ground or re-ground powders, was added to fresh fish burger formulation to extend its shelf life. To this aim, a shelf-life test was performed on fortified fish products stored at 4 °C. Control samples were also tested for comparison. Specifically, the pH and microbiological and sensory quality of all the fish burgers were monitored during refrigerated storage for about 1 month. The results from the in vitro test clearly indicate that the peel is abundantly more effective than seeds on selected spoilage bacteria and that the ground peel powder is slightly more antimicrobial than the same re-ground powder. Results from the shelf-life test assessed that the control sample became unacceptable within a few days (about 3 days), while the samples with pomegranate juice and by-products maintained microbial stability for a longer time (2 or 3 weeks) (p < 0.05). The main microbiological problems are the proliferations of mesophilic and psychrotrophic bacteria, Pseudomonas spp. and Shewanella. The addition of pomegranate to the formulation allowed the fish spoilage to be controlled by at least 2 or 3 log cycles. In agreement with findings from the in vitro test, the best results from the microbiological point of view were found in fish burgers with juice, peel and seed ground powders. Furthermore, the addition of pomegranate was also appreciated from the sensorial point of view. In fact, products with pomegranate were prized for about 3 weeks for color, odor, appearance and texture of both raw and cooked products. Therefore, the current study reveals that the incorporation of the entire pomegranate, added in all parts according to the zero-waste concept, could promote a significant shelf-life extension of fish burgers, mainly due to the bioactive compounds present in fruit by-products, without changing the sensory quality.

Fish Spoilage Detector

This project work involves using Arduino Uno software integrated with MQ 137- Ammonia Gas Sensor, MQ 135- Gas Sensor Module and Humidity Sensor Module DHT11 to set up a Fish Spoilage Detector model for the determination of spoilage in fish. The study takes into consideration spoilage seen in fishes and how to detect it. To study the threshold values of Ammonia, and other gases like Carbon Monoxide, model trial runs are carried out to arrive at appropriate hard measures of the threshold values, to improve the stability of a conceptual fish spoilage detector. The ammonia sensor is initially tested with a pure ammonia sample before being used to quantify total volatile basic nitrogen in various fish samples of various freshness levels. When compared to standard procedures like microbe count and chromatography, which take hours to get a result, the sensor can determine the freshness of a sample in a matter of seconds. The sensor response was shown to be highly linked with fish deterioration, demonstrating that using sensors is an effective technique to swiftly test for spoiling in a sample. After calibrating the sensor(which involved watching the fish degrade for almost two days), it was put to the test using random samples, demonstrating that it can accurately distinguish the degree of freshness of the preserved fish at varied temperatures(for measuring which a temperature sensor is also fixed). The model is run until visible indications of fish spoilage are seen. The sensors detect critical levels of ammonia, carbon monoxide and also measure humidity and temperature thereby, emitting warning signals in the form of flashes of light and a sound warning. The model setup also consists of a 1602 (16x2) LCD Display with a 12C/11C Interface that will display the temperature, humidity levels as well as that of ammonia and other gases like carbon monoxide and thus, helps in spoilage detection when the levels of these reach a particular threshold value. Calibration could be improved with detailed studies containing data regarding the rate of spoilage in fishes, temperature and humidity parameters.

Paving the Way for a Green Transition in the Design of Sensors and Biosensors for the Detection of Volatile Organic Compounds (VOCs).

The efficient and selective detection of volatile organic compounds (VOCs) provides key information for various purposes ranging from the toxicological analysis of indoor/outdoor environments to the diagnosis of diseases or to the investigation of biological processes. In the last decade, different sensors and biosensors providing reliable, rapid, and economic responses in the detection of VOCs have been successfully conceived and applied in numerous practical cases; however, the global necessity of a sustainable development, has driven the design of devices for the detection of VOCs to greener methods. In this review, the most recent and innovative VOC sensors and biosensors with sustainable features are presented. The sensors are grouped into three of the main industrial sectors of daily life, including environmental analysis, highly important for toxicity issues, food packaging tools, especially aimed at avoiding the spoilage of meat and fish, and the diagnosis of diseases, crucial for the early detection of relevant pathological conditions such as cancer and diabetes. The research outcomes presented in the review underly the necessity of preparing sensors with higher efficiency, lower detection limits, improved selectivity, and enhanced sustainable characteristics to fully address the sustainable manufacturing of VOC sensors and biosensors.

Antioxidant properties of medicinal plants and their effect on microbial spoilage of semi-finished meat, poultry and fish

Plant extracts rich in polyphenols can be used in the food industry as natural preservatives, extending the shelf life of prepared and semi-finished foods without chemical preservatives. In this paper, we investigate the polyphenolic composition, antioxidant activity and antibacterial properties of herbal extracts as part of food systems. The research objects were knot grass (Polýgonum aviculáre), marjoram (Oríganum), bur beggar-ticks (Bídenstripartíta), thyme (Thymus), whortleberry leaves (Vaccínium ida vítis), calendula (Calendula), sage (Salvia), chamomile flowers (Matricāriachamomīlla), eucalyptus (Eucalýptus) and bearberry (Arctostáphylosúva-úrsi). We determined the total content of phenolic compounds and flavonoids; the antioxidant activity by DPPH and FRAP methods; variations in the bacterial сontamination of animal raw materials over total bacterial count (TBC), coliform bacteria, yeast/fungi, salmonella and staphylococcus. Extracts of sage (1138±57 mg GA/100 g and 537±25 mg C/100 g), eucalyptus (1073±49 mg GA/100 g and 412±20 mg C/100 g), chamomile flowers (1002±36 mg GA/100 g and 493±22 mg C/100 g) and marjoram (1015±42 mg GA/100 g and 458±21 mg C/100 g) contain the largest amount of biologically active substances (phenols and flavonoids, respectively). Sage, eucalyptus and chamomile extracts demonstrate the highest antioxidant activity among the studied samples. Most of the studied extracts exhibit little or no effect on the organoleptic properties of finished products. In addition, chamomile flower, sage and eucalyptus extracts suppress the growth of pathogenic microorganisms in foods under experimental conditions. The microflora growth is significantly reduced when treating animal raw materials with calendula flowers, marjoram and thyme extracts. Extracts of sage, chamomile flowers, calendula flowers, marjoram and thyme can be recommended as components of food raw materials.

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.

Study of changes in freshness quality of mackerel (Scomberomorus commerson) with extract concentration and variation of mangrove leaves

Mackerel is one of the economic and important commodities, but fresh mackerel is a perishable food product that can rot easily. Deterioration in fish quality is inevitable and occurs very quickly in wet products that have high water and protein content. The main cause of fish deterioration process is by the microbial activity found in its body which quickly occurs after dies. The research method used was an experimental design with a completely randomized design (CRD) with 2 factors of factorial pattern (Rhizophora sp. Leaf Extract & Avicennia sp Leaf Extract) and 3 test levels (2%, 3%, and 4%). The aim of its study is to determine the potential of mangrove leaves and the types of phytochemical compounds contained in them and their effectiveness in inhibiting the rate of fish decay. The results that mangrove leaf extract could increase the organoleptic value and inhibit the rate of fish spoilage compared to samples without the addition of mangrove leaf extract. The best treatment was obtained by samples with Rhizophora sp mangrove leaf extract by 4% because it could maintain freshness and safe limits for consumption for 8 hours of storage in room temperature compared to control which was only 4 hours.

Colorimetric Paper-Based Dual Indicator Label for Real-Time Monitoring of Fish Freshness.

Fish freshness and quality monitoring are of high importance for consumers, retailers and fishing industry. Therefore, developing novel approaches that are simple, fast, non-destructive and inexpensive to monitor fish freshness in real time is of great value. One alternative is using Intelligent or smart packaging to monitor the freshness or conditions of packaged fish. On-package dual indicator label based on paper-based pH sensors was developed for real-time monitoring of the milkfish (Chanos chanos) freshness. The paper-based pH sensor was prepared using bromocresol purple (BCP) and bromothymol blue (BTB) that were immobilized onto a filter paper by dip coating. Herein, the fish degradation could be monitored visually by the dual indicator label, where the BCP changes from yellow to pink, then finally to purple, while the BTP changes from orange to green-yellow, and finally to green-blue to indicate fresh, medium fresh or spoiled product, respectively. The label responds to the pH change caused by the fish degradation and the colour of dual indicator changes to show the fish freshness at room temperature and chiller conditions. This pH change was followed by changes in the other parameters related to fish freshness, such as total volatile basic nitrogen (TVBN), total viable count (TVC), texture and odour. The threshold of fish spoilage at room temperature was observed at 8 h and under chiller conditions at 7 days when the deterioration time point was indicated by the colour changes. Thus, it can be concluded that the dual indicator label can be applied as a simple and low-cost on-package active label for fish freshness monitoring. Increasing consumer concerns about quality and safe food worldwide has boosted the search for a novel approach to food monitoring. In this work, a simple and practical on-package dual indicator label for real-time monitoring of fish freshness was developed. The colorimetric pH sensor was obtained simply by dip-coating of filter paper, yet it enables easy and accurate detection of fish spoilage with the naked eye. Similarly, the dual indicator label changes colour for other freshness parameters, such as TVBN, TVC, texture and odour.

A biopolymer-based pH indicator film for visually monitoring beef and fish spoilage

Food safety is a worldwide public concern that has recently gained increased attention due to the emerging outbreaks of foodborne diseases. Therefore, there is a pressing need to make simple, cost-effective, and environmentally friendly methods for detecting food spoilage and to mitigate the impact of possible outbreaks. The aim of this study is to develop a biodegradable indicator film which was made by combining cellulose-nanofiber/chitosan dyed with methyl red synthesis (CCM) as a pH indicator film and followed by a single layer coating of polylactic acid (PLA) on its surface, named PLA/CCM film. The microstructural properties of PLA/CCM films were studied using scanning electron microscopy (SEM) and results showed that PLA effectively adhered to the surface of CCM film. The microbial response to PLA/CCM film was determined via a bacterial plating method. It was found that the contact of film with the microbes caused a substantial color change in the film. The coating of PLA upon the CCM film decreased the percentage of the water vapor transmission rate (WVTR). The color of the film vividly altered from slightly red to yellow in response to a pH change in the range of 4–8. The PLA/CCM film was applied to monitor the spoilage of beef and fish at room temperature (23 °C) and revealed the onset of food spoilage by displaying the color change from red to yellow after 1 day. The total viable counts (TVC) of microorganisms and pH of the tested beef sample were determined, and the results revealed that both TVC and pH increased concurrently after beef spoilage.

Exploration of the roles of spoilage bacteria in degrading grass carp proteins during chilled storage: A combined metagenomic and metabolomic approach

Protein degradation11Protein degradation in this article refers to the deterioration of protein components, including both protein hydrolyzation and the further decomposing of protein hydrolyzation products like peptides and amino acids. caused by spoilage bacteria is highly related to fish quality deterioration during chilled storage. However, the exact roles of bacteria in degrading grass carp proteins are not fully known. In this work, we used metagenomics to analyze the microbiota composition in grass carp fillets, construct protein degrading pathways, and calculate taxonomic contributions to protein degrading functions. Besides, three dominant bacteria species were isolated and inoculated into sterile grass carp flesh, respectively. LC-MS-based untargeted metabolomics was then used to detect protein degradation metabolites produced by the inoculated bacteria. Combining the results of metagenomics and metabolomics, we found 1) Shewanella putrefaciens was active in hydrolyzing fish proteins (especially collagens) and produced quantities of putrescine through the arginine decarboxylase pathway; 2) Pseudomonas putida had potent potentials in utilizing oligopeptides and free amino acids; 3) Serine was a potential energy source for microbial growth and it was largely consumed by spoilage bacteria; 4) S. putrefaciens could form a metabiosis relationship with P. putida, due to their complementary roles in degrading fish proteins. Finally, we concluded that S. putrefaciens had the strongest spoilage potential among tested bacteria, suggesting the importance of S. putrefaciens inhibition in fish quality preservation. Meanwhile, this study contributed to a better understanding of microbial roles in fish spoilage and provided useful information for the development of new preservation methods.

The Application of Bacillus subtilis for Adhesion Inhibition of Pseudomonas and Preservation of Fresh Fish

Inhibiting the growth of spoilage bacteria, such as Pseudomonas spp., is key to reducing spoilage in fish. The mucus adhesion test in vitro showed that the adhesion ability of Bacillus subtilis was positively correlated with its inhibition ability to Pseudomonas spp. In vivo experiments of tilapia showed that dietary supplementation with B. subtilis could reduce the adhesion and colonization of Pseudomonas spp. in fish intestines and flesh, as well as reduce total volatile basic nitrogen (TVB-N) production. High throughput and metabolomic analysis showed treatment with B. subtilis, especially C6, reduced the growth of Pseudomonas spp., Aeromonas spp., Fusobacterium spp., and Enterobacterium spp., as well as aromatic spoilage compounds associated with these bacteria, such as indole, 2,4-bis(1,1-dimethylethyl)-phenol, 3-methyl-1-butanol, phenol, and 1-octen-3-ol. Our work showed that B. subtilis could improve the flavor of fish by changing the intestinal flora of fish, and it shows great promise as a microecological preservative.

Preparation of fish freshness colorimetric indicator label based on the dye of BTB grafted on MOF carrier

This work introduces a potential fish freshness indicator film based on cellulose acetate (CA) and polyethylene glycol 4000 (PEG 4000) incorporated with a novel dye of bromothymol blue (BTB) grafted on MOF (Cr-MIL-101-NH2) carrier. The characterization results of the modified dye (MOF-BTB) infer that most of the BTB is integrated with the framework by intermolecular force without breaking the MOF structure. The colorimetric film's oxygen transmission, water vapor transmission, and elongation at break, after the addition of MOF-BTB, shows a decrease, while the tensile strength of the film increase. The MOF-BTB film has observed no BTB migration in the simulated food liquid of neutral, acidic, and alcoholic food; besides, it preserves the color-change ability and is more profound and stable than the BTB film with the same effective dye content. We use the prepared freshness label for Grass carp freshness monitoring under 25 ℃. The freshness label produces a noticeable color change consistent with the fish spoilage around the total volatile basic nitrogen (TVB-N) threshold, which can warn the spoil of the fish. Therefore, the developed colorimetric freshness label can track fish freshness visually and non-destructively using synthetic dye without worrying about contaminating the fish from migration.

Electronic nose based on hybrid free-standing nanofibrous mats for meat spoilage monitoring

Food safety and quality control have become nowadays a major priority for the sake of public health to protect consumers from the risks of foodborne diseases and food poisoning. For instance, in the case of the decomposition of meat protein, ammonia and biogenic amines content can be used as a parameter to evaluate meat quality. However, practical analytical methods for in loco evaluation of amines release by meat are still on demand. Herein, we report hybrid free-standing composite nanofibers as sensing platforms to identify volatile amines (ammonia, methylamine and trimethylamine), as one of the main components of the gas produced in the process of meat spoilage, and to monitor fish freshness at room temperature. For that purpose, SiO2:In2O3, SiO2:ZnO and SiO2 nanofibers, prepared by electrospinning followed by thermal treatment, were deposited onto interdigitated electrodes and then modified with polyaniline and poly(styrene sulfonate). Seven sensing units of distinct compositions were employed in an impedimetric electronic nose, and multidimensional projection was used to help in the discrimination of standard analytes as well as of analytes released during the deterioration of fish real samples. The frequency selection resulted in improved discrimination by multidimensional projection and the sensor array showed an excellent performance to be applied in fish spoilage monitoring.