Seafood Spoilage Research Articles

Rapid species identification of seafood spoilage and pathogenic Gram‐positive bacteria by MALDI‐TOF mass fingerprinting

The rapid identification of food pathogenic and spoilage bacteria is important to ensure food quality and safety. Seafood contaminated with pathogenic bacteria is one of the major causes of food intoxications, and the rapid spoilage of seafood products results in high economic losses. In this study, a collection of the main seafood pathogenic and spoilage Gram-positive bacteria was compiled, including Bacillus spp., Listeria spp., Clostridium spp., Staphylococcus spp. and Carnobacterium spp. The strains, belonging to 20 different species, were obtained from the culture collections and studied by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). A reference library was created, including the spectral fingerprints of 32 reference strains and the extracted peak lists with 10-30 peak masses. Genus-specific as well as species-specific peak masses were assigned and could serve as biomarkers for the rapid bacterial identification. Furthermore, the peak mass lists were clustered with the web-application SPECLUST to show the phyloproteomic relationships among the studied strains. Afterwards, the method was successfully applied to identify six strains isolated from seafood by comparison with the reference library. Additionally, phylogenetic analysis based on the 16S rRNA gene was carried out and contrasted with the proteomic approach. This is the first time MALDI-TOF MS fingerprinting is applied to Gram-positive bacterial identification in seafood, being a fast and accurate technique to ensure seafood quality and safety.

Continuous quality and shelf life monitoring of retail-packed fresh cod loins in comparison with conventional methods

This study investigated the applicability of a new photochromic time-temperature indicator (TTI) to monitor the quality and shelf life of fresh cod loins in retail packs at different storage conditions; also compared this automatic monitoring method with other methods of quality control, such as sensory, chemical and microbiological analyses; and with a shelf life prediction model. TTI placed on the bottom of the packs effectively reflected the temperature condition of the product. TTI with the initial square value of 61 was suitable for continuous monitoring of the quality and shelf life of the product repacked on day 6 after processing. The estimated product shelf lives based on TTI and on the square-root model for relative rate of spoilage of fresh seafood were well correlated.

Safety Assessment of Fresh and Processed Seafood Products by MALDI-TOF Mass Fingerprinting

Foodborne intoxications caused by the consumption of fish and other products of marine origin contaminated with bacterial pathogens are an ever-present threat, either due to bacteria and/or its metabolites. In addition, the rapid spoilage of seafood due to microbial activity, results in high economic losses. The development of the microbiota in seafood products depends on the microbiological ambience of capture, processing and storage, and the applied preservation method. Thus, pathogenic and spoilage bacterial species in seafood may come from the indigenous microbiota of the aquatic ambience or are introduced by contamination during processing. Rapid and accurate bacterial species identification is essential for an effective control program to ensure safety and quality of either processed or minimally processed seafood. In the present work, matrix-assisted laser desorption ionization-time of flight mass spectrometry was successfully applied to identify 26 bacterial strains isolated from fresh fish and processed seafood samples. The approach was based on the comparison of unknown spectra to a reference spectral library and demonstrated to be a fast and accurate technique for bacterial species differentiation, which can be used for the rapid identification of foodborne pathogens and spoilage bacteria potentially present in products of marine origin.

Species Differentiation of Seafood Spoilage and Pathogenic Gram-Negative Bacteria by MALDI-TOF Mass Fingerprinting

Species differentiation is important for the early detection and identification of pathogenic and food-spoilage microorganisms that may be present in fish and seafood products. The main 26 species of seafood spoilage and pathogenic Gram-negative bacteria, including Aeromonas hydrophila, Acinetobacter baumanii, Pseudomonas spp., and Enterobacter spp. among others, were characterized by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) of low molecular weight proteins extracted from intact bacterial cells by a fast procedure. From the acquired spectra, a library of specific mass spectral fingerprints was constructed. To analyze spectral fingerprints, peaks in the mass range of 2000-10 000 Da were considered and representative mass lists of 10-35 peak masses were compiled. At least one unique biomarker peak was observed for each species, and various genus-specific peaks were detected for genera Proteus, Providencia, Pseudomonas, Serratia, Shewanella, and Vibrio. Phyloproteomic relationships based on these data were compared to phylogenetic analysis based on the 16S rRNA gene, and a similar clustering was found. The method was also successfully applied for the identification of three bacterial strains isolated from seafood by comparing the spectral fingerprints with the created library of reference fingerprints. Thus, the proteomic approach demonstrated to be a competent tool for species identification.

Protective Effect of a Non-Bacteriocinogenic Lactococcus piscium CNCM I-4031 Strain Against Listeria monocytogenes in Sterilized Tropical Cooked Peeled Shrimp

The protective activity of a non-bacteriocinogenic Lactococcus piscium CNCM I-4031 strain against Listeria monocytogenes was investigated in tropical cooked peeled shrimp stored at 8°C in modified atmosphere packaging (50% N2–50% CO2). When inoculated alone (L. piscium 107 CFU g−1 and L. monocytogenes 104 CFU g−1), protective culture and target strain grew very well on shrimp reaching a maximum cell number of 109 CFU g−1 after 7 and 14 days, respectively. In the presence of L. piscium, growth of L. monocytogenes was totally prevented after 3 days of storage. The count was 3.4 log CFU g−1 lower than in the control after 10 days and until the end of storage (31 days). Using the Seafood Spoilage and Safety Predictor Software (http://sssp.dtuaqua.dk), it was shown that pH decrease from 6.58 to 5.94 and lactic acid concentration of 89.65 mM measured in the co-inoculated batch did not fully explain the inhibition observed.

Study on seafood volatile profile characteristics during storage and its potential use for freshness evaluation by headspace solid phase microextraction coupled with gas chromatography–mass spectrometry

Seafood volatile profile characteristics at different storage phases are various and can be used for freshness evaluation during storage. It is imperative to obtain the full volatile information prior to the further study of seafood volatile profile characteristics during storage. Also, the efficient data-processing method is another important factor for the interpretation of seafood volatile profile characteristics during storage and related potential volatile markers. In this work, a new analytical strategy, including the efficient sampling technique, sensitive detection and suitable data-processing method, for seafood freshness evaluation was developed based on the volatile profile characteristics during storage. First, the study of volatiles of seafood samples including razor clam, redspot swimming crab and prawn at different storage phases were conducted by headspace solid phase microextraction (HSSPME) followed by gas chromatography–mass spectrometry (GC–MS) detection. Then, seafood volatile profile characteristics at different storage phases were statistically interpreted by a combination data-processing method including normalization, principle component analysis (PCA) and common model strategy. The different seafood volatile profile characteristics and potential volatile markers were attempted to be distilled. The results tentatively suggested that the different seafood volatile profile characteristics during storage could reflect the transitional changing seafood freshness and provide more precise warning information for seafood spoilage during storage than any single chemical markers. This work developed an analytical method for study of seafood volatile profile characteristics and tentatively proposed a new idea of using seafood volatile profile characteristics during storage for the freshness evaluation from the point of view of analytical chemistry.

Spoiling and formaldehyde-containing detections in octopus with an E-nose

The seafood dipped with formaldehyde to prevent from spoiling by dishonest mongers is a big danger to the physical health of consumer. An E-nose with six TGS gas sensors was used for spoiling and formaldehyde-containing detection of seafood in this paper. Two static features R 0 (resistance in the air), S (sensor response), and one dynamic feature DR (desorption rate) were extracted. Fresh octopus samples dipped in water solutions with different formaldehyde concentrations were measured. In these measurements, the stability of sensors and features was evaluated and compared. The mean relative errors of these three features were 23.6%, 19.7%, and 4.1%, respectively. The results showed that the dynamic feature was more stable. With principal component analysis, the spoilage of seafood could be easily detected. And the correct recognition rate of different octopus samples was 93.1%. The results showed that electronic nose analysis could be an efficient method for seafood quality assessment.

Polyphenol Uses in Seafood Conservation

Oxidative reactions are the main culprits in color alterations associated with seafood spoilage. Black spot formation or melanosis is a natural post-mortem oxidative mechanism, which cause crustaceans rejection by consumers because of their appearance. The use of phenolic compounds, such as 4-hexylresorcinol, appears to be a good alternative to the conventional sulphites, allowing longer conservation periods. Lipidic oxidation is also one of the main restrictive factors in the preservation of fish products. The application of natural plant extracts to prevent oxidative rancidity has been studied in a number of fish products. However, polyphenol-protein interactions may have a masking effect on the free radical scavenging activity of polyphenols and may also have a detrimental effect on the in vivo bioavailability of both phenolics and proteins. Polyphenolic plant extracts may be included into fish gelatin-based films in order to obtain an edible film with antioxidant properties. These films applied on the surface of raw or mild processed salted or smoked fish may increase the shelf life of fish products by reduction the lipid oxidation during the chilled storage.

Seafood Spoilage Predictor—development and distribution of a product specific application software

To allow shelf-life prediction of a range of products, the Seafood Spoilage Predictor (SSP) software has been developed to include both kinetic models for growth of specific spoilage microorganisms and empirical relative rates of spoilage models. SSP can read and evaluate temperature profile data of different formats and in this way the software is a flexible device for electronic time–temperature integration. Predicted values of microbial growth and of remaining product shelf life can be exported from SSP as graphs and tables in ASCII, HTML and eXtensible Mark-up Language (XML) formats and this allows SSP to be used in combination with other programmes. More than 300 people have downloaded SSP and distribution of this software from the internet has been efficient in stimulating the application of predictive microbiology and of mathematical seafood shelf-life models within industry, research, seafood inspection and teaching.

Antimicrobial effect of essential oils on the seafood spoilage micro-organism Photobacterium phosphoreum in liquid media and fish products.

To evaluate the antimicrobial effect of nine essential oils (EO) on P. phosphoreum and determine the effect of oregano oil on the shelf-life of modified atmosphere-packed (MAP) cod fillets. The antimicrobial effect of EO was studied in a liquid medium and in product storage trials. Oils of oregano and cinnamon had strongest antimicrobial activity, followed by lemongrass, thyme, clove, bay, marjoram, sage and basil oils. Oregano oil (0.05%, v/w) reduced growth of P. phosphoreum in naturally contaminated MAP cod fillets and extended shelf-life from 11-12 d to 21-26 d at 2 degrees C. Oregano oil reduced the growth of P. phosphoreum and extended the shelf-life of MAP cod fillets. Mild and natural preservation using EO can extend the shelf-life of MAP seafood through inhibiting the specific spoilage organism P. phosphoreum.

Temperature logging of fish catches using autonomous sensing units

Temperature profiles for fish catches including on-trawler and in auction rooms have been captured using autonomous temperature monitoring units. The profiles have been imported into Seafood Spoilage Prediction software and Remaining Shelf-Life estimated. The limitations of the monitoring system employed, and the impact of rapid developments in sensing and communications technologies on the food industry are discussed.

A technique for the determination of trimethylamine-N-oxide in natural waters and biological media.

Trimethylamine-N-oxide (TMAO) is a nitrogenous osmolyte widely distributed in marine organisms. The reduction of TMAO to TMA has long been implicated as characteristic reaction associated with fish and seafood spoilage. However, it is now apparent that, in the marine environment, TMAO can act as precursor to a range of reduced nitrogenous biogases that can play a significant role in the biogeochemical cycle of nitrogen and in the regulation of atmospheric pH. Although methods exist for the analysis of TMAO in some biological samples, they lack the sensitivity required for measurement of TMAO in natural waters. Here we present a new, safe and sensitive method for the determination of TMAO in aqueous and biological media, where TMAO is enzymatically reduced to TMA and subsequently quantified using Flow Injection Gas Diffusion-Ion Chromatography (Gibb et al. J. Autom. Chem. 1995, 17 (6), 205-212). The limit of detection was calculated to be 1.35 nmol dm-3 TMAO, and the response was linear for both fresh and seawater (R2 = 0.996 and 0.993, respectively). Precision (RSD) for standards in the range 40-600 nmol dm-3 was within 3%. The specificity and competitive inhibition of the enzyme are addressed and the applicability of the technique demonstrated through analysis of a number of natural water and biological samples.