Microbiological, biochemical and sensory assessment of mussels (Mytilus galloprovincialis) stored under modified atmosphere packaging

Bilayer coatings for extension of the shelf life of fish fillets: Incorporating seaweed sulfated polysaccharides in chitosan-alginate LbL structures

The aim of this study was to develop a new active coating of layer-by-layer (LbL) structure composed of alginate (as polyanions) and chitosan (as a polycation) containing sulfated polysaccharide (fucoidan) from Sargassum angustifolium, to protect rainbow trout fillets during refrigerated storage. Chitosan and alginate do not combine with each other as a homogeneous solution, so they are suitable for multilayer coatings. The results demonstrated that coating samples with chitosan and fucoidan significantly improved the quality of fish fillets and extended their shelf life from 6 to 16 days. The chemical values (TBARS and TVB-N) and bacterial growth (total viable count (TVC), total psychrophilic count (PTC), and lactic acid bacteria (LAB)) indicated lower levels in the LbL coating samples containing fucoidan compared to the alginate and control samples. Among the different coating samples, the LbL coating with fucoidan (AChF1) exhibited lower weight loss, improved chromaticity (L*, a*, and b*), and minimal changes in mechanical and sensory evaluations. Based on the findings, AChF1 was the most effective treatment for increasing the shelf life of rainbow trout fillets during refrigerated storage. Therefore, it has potential applications in the food packaging industry.

Bacterial metagenome analysis of Mytilus galloprovincialis collected from Istanbul and Izmir coastal stations of Turkey

Mytilus galloprovincialis is a marine mollusk belonging to the Bivalvia class. It has been distributed largely in Turkish shores and worldwide aquatic environments. Besides being known as an environmental pollution indicator, it is highly consumed as a food and has a high economic value. Due to their nutritional mechanisms by filtering water, they are affected by pollution in seawater and mussels can host-microbial diversity of environmental origin as well as pathogenic bacteria. Therefore, in this study, bacterial species found in Mediterranean mussels collected from the coastal stations of Istanbul [Rumeli Kavagi (RK), Kucukcekmece (KC)], and Izmir [(Foca (MF), Urla (MU)] were investigated and compared with microbiological and metagenomic analyses. According to microbiological analysis results, 34 mussel-associated Enterobacteriaceae and Vibrionaceae family members were identified. As a result of the culture-independent metagenomic analysis, taxonomic groups for each station were identified and compared based on Operational Taxonomic Unit data. For all stations, the most abundant bacterial genera were the unclassified bacterial genera. The total number of mussel-related total richness identified in all groups was 4889 (RK = 1605; KC = 1930; MF = 1508; and MU = 1125). According to the metagenomic data obtained in this study, different relative amounts of Lachnospiraceae and Bacteroidetes taxa groups were reported for all stations. The pathogenic bacterial genera identified by metagenomic analyses which may be significant for the public health are Arcobacter, Clostridium, Aeromonas, Vibrio, Escherichia_Shigella, Klebsiella, Campylobacter, Helicobacter, Pseudomonas, Morganella, Serratia, Corynebacterium, Enterococcus, Staphylococcus, Yersinia, Mycoplasma, Brucellaceae_unclassified, Pantoea, and Proteus.

Jamun fruit (Syzgium cumini) skin extract based indicator for monitoring chicken patties quality during storage

Natural plant pigment, anthocyanins have the capability to change its color with the change of its structure influenced by changing pH. This feature of anthocyanin has been harnessed to design a meat products quality indicator. In the present experiment anthocyanin rich Jamun fruit (Syzgium cumini) skin extract was used to develop quality indicator by immobilizing on filter paper strips with the purpose of application in chicken patties packets stored at refrigeration temperature (4 ± 1 °C). The indicator changed its color from violet to yellow due to changed pH in it when it was attached inside packet of chicken patties during storage, due to reaction with volatile basic compounds generated from meat. During storage for 21 days, various changes in quality attributes of chicken patties viz., pH, Total volatile basic nitrogen (TVBN), ammonia level, color value, sensory attributes and microbial evaluation were estimated. The pH decreased (P < 0.5) from 6.22 to 6.04. TVBN and ammonia and level increased significantly (P < 0.5) throughout storage. Redness, yellowness, hue and chroma value gradually changed during storage. Sensory scores also decreased significantly (P < 0.5). Microbial count also increased (P < 0.5) during this time. The experiment showed that, during storage, the color changing pattern of quality indicator was well correlated with the changes in quality attributes of chicken meat patties. Therefore, it is expected that the developed quality indicator can provide a convenient, non destructive, visual mean to monitor the meat products quality during refrigerated storage.

Effects of Vietnamese tamarind fish sauce enriched with iron and zinc on green mussel quality

Marinating is a traditional technology to improve the shelf - life and quality of products. Enriched Viet- namese tamarind fish sauce was prepared and used to marinate green mussels. Subjects of this research were: green mussels (C1), marinated green mussels (C2), and marinated green mussels packaged in modified atmosphere (M1, M2, and M3). A percentage of O :CO :N was 5:50:45 for M1, 5:70:25 for M2, and 5:90:5 for M3. Microbiological, hemical, and sensory qualities of the samples were analyzed during storage at 4°C for 30 days. The results indicate that glycogen, iron, and zinc contents as well as pH values decreased in all the cases during storage. In addition, TVB-N and TBARS values as well as mesophilic and lactic acid bacteria increased with time in all the samples. The number of psychrophilic bacteria in marinated samples was small or not detected at all. Escherichia coli, Staphylo- coccus aureus, Salmonella spp. and Vibrio cholera were below standard values. Based on sensory acceptability, the shelf-life of C1, C2, M1, M2, and M3 samples was 12, 18, 24, 24, and 27 days, respectively.

HRM analysis as a tool to facilitate identification of bacteria from mussels during storage at 4 °C

High-resolution melting (HRM) analysis followed by sequencing was applied for determination of bacteria grown on plates isolated from farmed mussels (Mytilus galloprovincialis) during their storage at 4 °C. The V3-V4 region of the 16S rRNA gene from the isolates was amplified using 16S universal primers. Melting curves (peaks) and high resolution melting curves (shape) of the amplicons and sequencing analysis were used for differentiation and identification of the isolated bacteria, respectively. The majority of the isolates (a sum of 101 colonies, from five time intervals: day 0, 2, 4, 6 and 8) from non-selective solid medium plates were classified in four bacterial groups based on the melting curves (peaks) and HRM curves (shape) of the amplicons, while three isolates presented distinct HRM curve profiles (single). Afterwards, sequencing analysis showed that the isolates with a) the same melting peak temperature and b) HRM curves that were >95% similar grouped into the same bacterial species. Therefore, based on this methodology, the cultivable microbial population of chill-stored mussels was initially dominated by Psychrobacter alimentarius against others, such as Psychrobacter pulmonis, Psychrobacter celer and Klebsiella pneumoniae. P. alimentarius was also the dominant microorganism at the time of the sensory rejection (day 8). Concluding, HRM analysis could be used as a useful tool for the rapid differentiation of the bacteria isolated from mussels during storage, at species level, and then identification is feasible by the sequencing of one only representative of each bacterial species, thus reducing the cost of required sequencing.

Effect of Lactic and Citric Acid Pretreatment on Quality Changes of Green Mussel (Perna Viridis) During Chilled Storage

Limited shelf life of green mussel restricts its accessibility to wider markets. The study assessed the potential of using organic acids (lactic and citric acids) in enhancing the quality and storage life of chilled mussel. Pretreatments included: 2% lactic acid (LA) and 2% citric acid (CA). Results from sensory analysis concluded that lactic acid (LA) pretreatment had 15 days of acceptability compared to the untreated sample. It had also lower the volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), psychrophilic and lactic acid bacteria count of the sample during the storage. The weight loss of the citric acid pretreated sample was higher compared to the lactic acid pretreated mussel. Results from quality assessment indicated that pretreatment using lactic acid can be used to improve the storage life of chilled green mussel for 15 days compared 6 days of untreated samples.

Spoilage microbial community profiling by 16S rRNA amplicon sequencing of modified atmosphere packaged live mussels stored at 4oC

There is little information on the microbial communities associated with modified atmosphere (MA)-packaged live mussels. There is also a dearth of information on how pre-packaging depuration modifies the microbial communities and spoilage of live mussels. Amplicon sequencing was used to describe spoilage microbial succession in MA-packaged live mussels during storage at 4 °C. Proteobacteria, Cyanobacteria and Firmicutes were the three major phyla observed in the mussel meat and pouch water of undepurated and depurated mussels. Among these phyla, Cyanobacteria was more predominant on day 0 in mussel meat of undepurated and depurated mussels while Proteobacteria was predominant in commercially-depurated mussels. Synechococcus was apparently dominant on days 0-7 in the meat of undepurated mussels and days 0-10 in depurated mussels. Shewanella was dominant on day 0 in commercially-depurated mussels and dominant on day 15 in undepurated while Acidaminococcus was dominant in depurated mussels on day 15. Psychromonas was observed to be dominant in commercially-depurated mussels on day 7 and further shifted to Acinetobacter by day 10 and 15. In the pouch water, Acinetobacter was dominant throughout the storage days in undepurated mussels while Psychrobacter was predominant in both depurated and commercially-depurated mussels. This study demonstrated the impact of depuration on the microbiota and the spoilage mechanism of MA-packaged live mussels. Shewanella was easily removed through depuration. However, spoilage bacteria such as Acidaminococcus could not be easily removed although they are not important at the beginning but grew at the end. Pouch water contributed suitable biological medium for the growth of Acinetobacter and Psychrobacter and both enhanced the growth of spoilage bacteria such as Shewanella and Acidaminococcus.

Seafood spoilage microbiota and associated volatile organic compounds at different storage temperatures and packaging conditions

Seafood comprising of both vertebrate and invertebrate aquatic organisms are nutritious, rich in omega-3 fatty acids, essential vitamins, proteins, minerals and form part of healthy diet. However, despite the health and nutritional benefits, seafood is highly perishable. Spoilage of seafood could be as a result of microbial activity, autolysis or chemical oxidation. Microbial activity constitutes more spoilage than others. Spoilage bacteria are commonly Gram negative and produce off odours and flavours in seafood as a result of their metabolic activities. Storage temperature, handling and packaging conditions affect microbial growth and thus the shelf-life of seafood. Due to the complexity of the microbial communities in seafood, culture dependent methods of detection may not be useful, hence the need for culture independent methods are necessary to understand the diversity of microbiota and spoilage process. Similarly, the volatile organic compounds released by spoilage bacteria are not fully understood in some seafood. This review therefore highlights current knowledge and understanding of seafood spoilage microbiota, volatile organic compounds, effects of storage temperature and packaging conditions on quality of seafood.

Bacterial microbiota profile in gills of modified atmosphere-packaged oysters stored at 4 °C

As filter-feeding bivalves, oysters can accumulate microorganisms into their gills, causing spoilage and potential safety issues. This study aims to investigate the changes in the gill microbiota of oysters packed under air and modified atmospheres (MAs, 50% CO₂: 50% N₂, 70% CO₂: 30% O₂, and 50% CO₂: 50% O₂) during storage at 4 °C. The diversity of bacterial microbiota in oyster gills was profiled through polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis on the 16S rRNA gene V3 region to describe the variation during the entire storage period. The DGGE profile revealed high bacterial diversity in the air- and MA-packaged oyster gills, and the spoilage bacterial microbiota varied in the MA-packaged oyster gills. Results indicated that CO₂:O₂ (70%:30%) was suitable for oyster MA packaging and that high bacterial loads in oyster gills need to be considered during storage. In addition, Lactobacillus and Lactococcus species were found to grow dominantly in fresh oyster gills under MA packaging, which supports the potential application of MA packaging for oyster storage.

Quality assessment of the blue mussel (Mytilus edulis): comparison between commercial and wild types

This study compared species identity, microplastics, chemical and microbial contamination between consumption mussels and wild type mussels, collected at Belgian department stores and Belgian groynes and quaysides, respectively. Species identification based on genetic analysis showed a high number of Mytilus (M.) edulis compared to M. galloprovincialis and M. edulis/galloprovincialis hybrid mussels. The number of total microplastics varied from 2.6 to 5.1 fibres/10 g of mussel. A higher prevalence of orange fibres at quaysides is related to fisheries activities. Chemical contamination of polycyclic aromatic hydrocarbons and polychlorobiphenyls could be related to industrial activities and water turbidity, with maximum concentrations at the quayside of port Zeebrugge. The inverse was noted for Escherichia coli contamination, which was relatively low at Zeebrugge quayside with a total count of 3.9 × 10(2)CFU/100 g tissue, due to limited agricultural effluents. Results of this complementary analysis stress the importance of integrated monitoring and quality assessment.

Biogenic amines formation, nucleotide degradation and TVB-N accumulation of vacuum-packed minced sturgeon (Acipenser schrencki) stored at 4 °C and their relation to microbiological attributes

BACKGROUND

Sturgeon (Acipenser schrencki) were filleted, minced, vacuum-packed and stored at 4 °C. Minced sturgeon muscles were analysed for 10 days to determine biochemical [eight biogenic amines, ATP and breakdown products, K value, total volatile basic nitrogen (TVB-N) and pH], microbiological (total viable counts, Enterobacteriaceae, Psychrotrophs, Pseudomonas, Aeromonas, Vibrio, Lactobacillus and Brochothrix thermosphacta) changes and their relationships.

RESULTS

The shelf-life of sturgeon was found to be 3-4 days according to microbiological assessment. At the end of the storage, Psychrotrophs, Enterobacteriaceae and Aeromonas became the dominant bacteria, reaching 7.85, 7.98 and 8.02 log cfu g(-1), respectively. Biogenic amines, hypoxanthine and the K value increased significantly (P < 0.05) during the storage. Putrescine and cadaverine was the dominant biogenic amines while tryptamine was not detected during the storage. In addition, putrescine, cadaverine and hypoxanthine were highly related to storage time and total viable counts (r(2), 0.876-0.962), indicating that they can be good biomarkers for quality assessment of vacuum-packed minced sturgeon stored at 4 °C.

CONCLUSION

In this study, key biochemical and microbiological attributes were established to monitor the spoilage and shelf life of vacuum-packed sturgeon. These results could help to establish better cold storage management of minced sturgeon products under commercial conditions.

Evaluation of the processing of Perna perna mussels: the influence of water quality involved in the cooling operations in the physico-chemical and microbiological characteristics of the product

BACKGROUND

The state of Santa Catarina in Brazil is a large producer of Perna perna mussels. However, raw and processed mussels have a short shelf life because of their high microbiological count, such as Vibrio spp. This study evaluated the microbiological and physicochemical quality of raw and ready-to-eat mussels and the quality of water and ice used in the processing of mussels.

RESULTS

The microbiological conditions of water and ice used in the processing are not in accordance with Brazilian legislation because of the presence of coliforms and Vibrio spp. For ready-to-eat mussels, counts of psychrophilic and psychrotrophic micro-organisms reached 10(5) colony-forming units g(-1) , a value close to the onset of product degradation during storage. Counts of coliforms, coagulase-positive Staphylococcus, Salmonella spp. and sulfite-reducing Clostridium in the mussels analysed during processing are in accordance with Brazilian law. The F value for the sterilisation procedure was lower than that required for Clostridium botulinum.

CONCLUSION

The study shows that microbiological cross-contamination occurred during the processing of mussels. Rigorous control is necessary from the production area of mussels to retailers. Good manufacturing practices must be implemented in the industry and cross-contamination avoided, mainly by Vibrio spp. after heat treatment.

Botulism challenge studies of a modified atmosphere package for fresh mussels: inoculated pack studies

A series of botulism challenge studies were performed to determine the possibility of production of botulinum toxin in mussels (Mytilus edulis) held under a commercial high-oxygen (60 to 65% O(2)), modified atmosphere packaging (MAP) condition. Spore mixtures of six strains of nonproteolytic Clostridium botulinum were introduced into mussel MAP packages receiving different packaging buffers with or without the addition of lactic acid bacteria. Dye studies and package flipping trials were conducted to ensure internalization of spores by packed mussels. Inoculated mussel packages were stored at normal (4°C) and abusive (12°C) temperatures for 21 and 13 days, respectively, which were beyond the packaged mussels' intended shelf life. Microbiological and chemical analyses were conducted at predetermined intervals (a total of five sampling times at each temperature), including total aerobic plate counts, C. botulinum counts, lactic acid bacterial counts, package headspace gas composition, pH of packaging buffer and mussel meat, and botulinum toxin assays of packaging buffer and mussel meat. Results revealed that C. botulinum inoculated in fresh mussels packed under MAP packaging did not produce toxin, even at an abusive storage temperature and when held beyond their shelf life. No evidence was found that packaging buffers or gas composition influenced the lack of botulinum toxin production in packed mussels.

Determination of Biogenic Amines and Endotoxin in Squid, Musky Octopus, Norway Lobster, and Mussel Stored at Room Temperature

Little research has been published on the indicators of spoilage in Mediterranean molluscan shellfish and crustaceans. Thus is why we studied changes in the concentrations of endotoxin and four biogenic amines (histamine, putrescine, tyramine and cadaverine) in European common squid (Loligo subulata, Lamarck, 1798), musky octopus (Eledone moschata, Lamarck, 1798), Norway lobster (Nephrops norvegicus, Linnaeus, 1758), and mussel (Mytilus galloprovincialis, Lamarck, 1819) from the Adriatic Sea stored at room temperature for 24 h. Endotoxin load in fresh squid, Norway lobster, and mussel (<1 EU mg-1) indicated good microbiological quality of raw samples. Biogenic amine index (as the sum of histamine, putrescine, tyramine, and cadaverine) correlated well with endotoxin load in squid (r=0.978, p<0.001) and musky octopus (r=0.874, p<0.01). A good correlation was also found between endotoxin and putrescine in Norway lobster (r=0.777, p<0.05). The highest endotoxin load was found in decomposed mussels and was associated with histamine alone. In conclusion, increase in biogenic amine levels is species-specific. Endotoxin analysis could be used for rapid assessment of microbiological quality of cephalopods and shellfish.

Protease activity in post-mortem red swamp crayfish (Procambarus clarkii) muscle stored in modified atmosphere packaging

Protease activity during storage is thought to be an important contributor to decreased shelf life of fresh seafood. To examine this, three batches of red swamp crayfish ( Procambarus clarkii) tails, placed on trays, were packed with a polyvinyl chloride film (aerobic packaging or AP), under vacuum (vacuum packaging or VP), or under a modified atmosphere (MAP: 80% CO 2/10% O 2/10% N 2), and proteolytic activity was measured on days 0, 1, 3, 6, and 10 during storage at 2 degrees C. The crude extract from the crayfish digestive system (gut) did not have an apparent role in muscle proteolysis as negligible proteolytic activity was detected. However, the loss of calpastatin (the endogenous calpain inhibitor) was identified in MAP-stored muscle samples on day 10, suggestive of high m-calpain activity. Tail samples stored in AP showed no appreciable proteolysis, but those stored in MAP and VP showed significant decreases in the levels of 53, 66, 71, and 110 kDa polypeptides during storage. The observed proteolytic activity and myofibrillar protein degradation did not correspond to muscle textural properties as the MAP samples had an increased toughness ( P < 0.05) after storage for 10 days. These findings suggest that other physicochemical mechanisms are involved in postmortem alteration in the crayfish muscle structure under the packaging systems investigated.

Shelf-life extension of refrigerated Mediterranean mullet (Mullus surmuletus) using modified atmosphere packaging

The present work evaluated the quality and freshness characteristics and the effect of modified atmosphere packaging (MAP) on the shelf-life extension of refrigerated Mediterranean mullet using microbiological, biochemical, and sensory analyses. Fresh open sea red mullet (Mullus surmuletus) were packaged in four different atmospheres: M1, 10%/20%/70% (O2/ CO2/N2); M2, 10%/40%/50% (O2/CO2/N2); M3, 10%/60%/30% (O2/CO2/N2); identical fish samples were packaged in air. All fish were kept under refrigeration (4 +/- 0.5 degrees C) for 14 days. Of the three gas atmospheres, the 10%/40%/50% (M2) and 10%/ 60%/30% (M3) gas mixtures were the most effective for inhibiting growth of aerobic microflora in mullet samples until day 10 of refrigerated storage. H2S-producing bacteria and pseudomonads were part of the mullet microflora and their growth was partly inhibited under MAP conditions. Between these two bacterial groups, H2S-producing bacteria (including Shewanella putrefaciens) were dominant toward the end of the storage period, regardless of the packaging conditions. Brochothrix thermosphacta and lactic acid bacteria were found to be members of the final microbial flora of MAP and air-packaged mullet, whereas the Enterobacteriaceae population was lower than other bacterial groups. Of the chemical freshness indices determined, thiobarbituric acid values were variable in mullet samples irrespective of packaging conditions indicative of no specific oxidative rancidity trend. Based on sensorial data and aerobic plate count, trimethylamine nitrogen and total volatile basic nitrogen limit values in the range of ca. 15 to 23 and 52 to 60 mg N/100 g of fish muscle were obtained, respectively, for mullet packaged under modified atmosphere and air. Sensory analyses (odor and taste attributes) showed that the limit of sensorial acceptability was reached after ca. 6 days for the samples packaged in air, 8 days for the M1 and M3 samples, and after 10 days for the M2 samples. Respective shelf-life extension for fresh whole mullet was ca. 2 days (M1 and M3 gas mixtures), and 4 days (M2 gas mixture).