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

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.

Identification of changes in the microflora composition of Japanese horse mackerel (Trachurus japonicus) during storage to identify specific spoilageorganisms

Japanese horse mackerel (Trachurus japonicus) is an important marine resource, and its loss and waste should be reduced. This study aimed to identify the changes in the microflora composition during storage and specific spoilage organisms (SSOs) in Japanese horse mackerel, for spoilage prevention. They were stored at either 20 °C or 4 °C aerobically, and the bacterial viable counts, concentration of total volatile basic nitrogen (TVB-N), and microflora composition for each group were analyzed. Samples stored at 20 °C for 48 h showed similar viable counts to those stored at 4 °C for 168 h; however, the TVB-N concentrations increased at 20 °C, but not at 4 °C. 16S rRNA metagenome analysis showed that Shewanella became dominant genus in the microflora regardless of the storage temperature. However, dominant amplicon sequence variants (ASVs), which are a more detailed classification level than the genus, differed depending on the storage temperatures; therefore, dominant ASVs at 20 °C were assumed to be potential SSOs. Shewanella sp. Strain NFH-SH190041, which was genetically closely related to the dominant ASVs at 20 °C, was isolated, and its spoilage ability was verified. The strain NFH-SH190041 may be considered a novel SSO of Japanese horse mackerel because its 16S rRNA sequence is clearly different from those of known species.

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Changes in microflora in every part of the Japanese horse mackerel were visualized.

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NFH-SH190041 was assumed as novel specific spoilage organism.

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The spoilage ability of NFH-SH190041 was verified.

Prediction in the Dynamics and Spoilage of Shewanella putrefaciens in Bigeye Tuna (Thunnus obesus) by Gas Sensors Stored at Different Refrigeration Temperatures

Shewanella putrefaciens have a faster growth rate and strong spoilage potential at low temperatures for aquatic products. This study developed a nondestructive method for predicting the kinetic growth and spoilage of S. putrefaciens in bigeye tuna during cold storage at 4, 7 and 10 °C by electronic nose. According to the responses of electronic nose sensor P30/2, the fitted primary kinetic models (Gompertz and logistic models) and secondary model (square root function model) were able to better simulate the dynamic growth of S. putrefaciens, with high R² and low RMSE values in the range of 0.96–0.99 and 0.021–0.061, respectively. A partial least squares (PLS) regression model based on both electronic nose sensor response values and electrical conductivity (EC) values predicted spoilage of S. putrefaciens in bigeye tuna more accurately than the PLS model based on sensor signal values only. In addition, SPME/GC-MS analysis suggested that 1-octen-3-ol, 2-nonanone, 2-heptanone, dimethyl disulfide and methylamine, N, N-dimethyl- are the key VOCs of tuna inoculated with S. putrefaciens.

High Oxygen Packaging of Atlantic Cod Fillets Inhibits Known Spoilage Organisms, but Sensory Quality Is Not Improved Due to the Growth of Carnobacterium/Carnobacteriaceae

Improved quality control and prolonged shelf life are important actions in preventing food waste. To get an overview of the bacterial diversity of fillets from live stored mature Atlantic cod, bacterial isolates were identified before and after storage (air and vacuum) and freezing/thawing. Based on the load of dominating bacteria, the effect of different packaging methods and a short freezing/thawing process on prolonged shelf-life was evaluated (total viable counts, bacteriota, sensory attributes, and volatile components). Hand filleted (strict hygiene) cod fillets had a low initial bacterial load dominated by the spoilage organism Photobacterium, whereas industrially produced fillets had higher bacterial loads and diversity (Pseudomonas, Arthrobacter, Psychrobacter, Shewanella). The identified bacteria after storage in vacuum or air were similar to the initially identified bacteria. Bacteriota analysis showed that a short time freezing/thawing process reduced Photobacterium while modified atmosphere packaging (MAP; 60% CO₂/40% O₂ or 60% CO₂/40% N₂) inhibited the growth of important spoilage bacteria (Photobacterium,Shewanella, Pseudomonas) and allowed the growth of Carnobacterium/Carnobacteriaceae and Acinetobacter. Despite being dominated by Photobacterium, fresh fillets stored in MAP 60% CO₂/40% N₂ demonstrated better sensory quality after 13 days of storage than fillets stored in MAP 60% CO₂/40% O₂ (dominated by Carnobacterium/Carnobacteriaceae). Carnobacterium spp. or other members of Carnobacteriaceae may therefore be potential spoilage organisms in cod when other spoilage bacteria are reduced or inhibited.

Application of Interactive and Intelligent Packaging for Fresh Fish Shelf-Life Monitoring

Smart packaging, also known as intelligent packaging, is responsive to external stimuli, moisture, light, oxygen, heat, pH, and bacterial growth. It has evolved from extensive applications in food safety, bacterial response, and medical packaging. Interactive packaging has a scientific basis for additional information about food products because these codes give all required data. This work deals with a combination of frontline food sciences, smart and interactive packaging that are applicable for future production of nutrition packages through smart detection of food spooling. Additionally, it verifies the best degree of food safety and population demands as the third generation of packaging technology. High qualified duplex laminated package with a nano-encapsulated pH monitoring label for fresh fish was printed. The interactive Quick Response code icon was combined in a designed package with important information about cooking, smart packaging, and fish quality. Therefore, particle size, zeta potential, and surface area are measured for a nanoencapsulated indicator which exhibits 74.4 nm, 23.6 mV, and 88.9 m²/g, respectively: overall migration, water vapor, and oxygen permeability. The properties of printing for 11 color spots are evaluated by x-rite before and after the cold storage period without any detectable changes in the rate of color change (ΔE). The bacterial count of the tested sample is examined by counting the microbial colonies in the agar plate media. There is good agreement between microbial count and smart indicator color change as an effective direct detection tool for sustainable food quality and safety.

Sustainable sources for antioxidant and antimicrobial compounds used in meat and seafood products

The contribution of food in promotion of health has become of most importance. The challenges that lie before the global food supply chain, such as climate changes, food contamination, and antimicrobial resistance may compromise food safety at international scale. Compounds with strong antimicrobial and antioxidant activity can be extracted from different natural and sustainable sources and may contribute to extend the shelf life of meat and seafood products, enhance food safety and enrich foods with additional biologically active and functional ingredients. This chapter describes the use of bioprotective cultures, essential oils, plant extracts, seaweed extracts and grape pomace compounds in production of value-added meat and seafood products with improved shelf life and safety, following the requests from the market and consumers.

Characterization of Bacterial Communities of Cold-Smoked Salmon during Storage

Cold-smoked salmon is a widely consumed ready-to-eat seafood product that is a fragile commodity with a long shelf-life. The microbial ecology of cold-smoked salmon during its shelf-life is well known. However, to our knowledge, no study on the microbial ecology of cold-smoked salmon using next-generation sequencing has yet been undertaken. In this study, cold-smoked salmon microbiotas were investigated using a polyphasic approach composed of cultivable methods, V3—V4 16S rRNA gene metabarcoding and chemical analyses. Forty-five cold-smoked salmon products processed in three different factories were analyzed. The metabarcoding approach highlighted 12 dominant genera previously reported as fish spoilers: Firmicutes Staphylococcus, Carnobacterium, Lactobacillus, β-Proteobacteria Photobacterium, Vibrio, Aliivibrio, Salinivibrio, Enterobacteriaceae Serratia,Pantoea, γ-Proteobacteria Psychrobacter, Shewanella and Pseudomonas. Specific operational taxonomic units were identified during the 28-day storage study period. Operational taxonomic units specific to the processing environment were also identified. Although the 45 cold-smoked salmon products shared a core microbiota, a processing plant signature was found. This suggest that the bacterial communities of cold-smoked salmon products are impacted by the processing environment, and this environment could have a negative effect on product quality. The use of a polyphasic approach for seafood products and food processing environments could provide better insights into residential bacteria dynamics and their impact on food safety and quality.

Microbiome Population Dynamics of Cold-Smoked Sockeye Salmon during Refrigerated Storage and after Culture Enrichment

ABSTRACT

Cold-smoked salmon is a ready-to-eat seafood product of high commercial importance. The processing and storage steps facilitate the introduction, growth, and persistence of foodborne pathogens and spoilage bacteria. The growth of commensal bacteria during storage and once the product is opened also influence the quality and safety of cold-smoked salmon. Here we investigated the microbial community through targeted 16S rRNA gene and shotgun metagenomic sequencing as means to better understand the interactions among bacteria in cold-smoked salmon. Cold-smoked salmon samples were tested over 30 days of aerobic storage at 4°C and cultured at each time point in a buffered Listeria enrichment broth (BLEB) commonly used to detect Listeria in foods. The microbiomes were composed of Firmicutes and Proteobacteria, namely, Carnobacterium, Brochothrix, Pseudomonas, Serratia, and Psychrobacter. Pseudomonas species were the most diverse species, with 181 taxa identified. In addition, we identified potential homologs to 10 classes of bacteriocins in microbiomes of cold-smoked salmon stored at 4°C and corresponding BLEB culture enrichments. The findings presented here contribute to our understanding of microbiome population dynamics in cold-smoked salmon, including changes in bacterial taxa during aerobic cold storage and after culture enrichment. This may facilitate improvements to pathogen detection and quality preservation of this food.

HIGHLIGHTS

Synergistic Antimicrobial Effectiveness of Plant Essential Oil and Its Application in Seafood Preservation: A Review

The synergistic potential of plant essential oils (EOs) with other conventional and non-conventional antimicrobial agents is a promising strategy for increasing antimicrobial efficacy and controlling foodborne pathogens. Spoilage microorganisms are one of main concerns of seafood products, while the prevention of seafood spoilage principally requires exclusion or inactivation of microbial activity. This review provides a comprehensive overview of recent studies on the synergistic antimicrobial effect of EOs combined with other available chemicals (such as antibiotics, organic acids, and plant extracts) or physical methods (such as high hydrostatic pressure, irradiation, and vacuum-packaging) utilized to reduce the growth of foodborne pathogens and/or to extend the shelf-life of seafood products. This review highlights the synergistic ability of EOs when used as a seafood preservative, discovering the possible routes of the combined techniques for the development of a novel seafood preservation strategy.

Innovative Seafood Preservation Technologies: Recent Developments

Fish and fishery products are among the food commodities of high commercial value, high-quality protein content, vitamins, minerals and unsaturated fatty acids, which are beneficial to health. However, seafood products are highly perishable and thus require proper processing to maintain their quality and safety. On the other hand, consumers, nowadays, demand fresh or fresh-like, minimally processed fishery products that do not alter their natural quality attributes. The present article reviews the results of studies published over the last 15 years in the literature on: (i) the main spoilage mechanisms of seafood including contamination with pathogens and (ii) innovative processing technologies applied for the preservation and shelf life extension of seafood products. These primarily include: high hydrostatic pressure, natural preservatives, ozonation, irradiation, pulse light technology and retort pouch processing.

Antimicrobial Blue Light versus Pathogenic Bacteria: Mechanism, Application in the Food Industry, Hurdle Technologies and Potential Resistance

Blue light primarily exhibits antimicrobial activity through the activation of endogenous photosensitizers, which leads to the formation of reactive oxygen species that attack components of bacterial cells. Current data show that blue light is innocuous on the skin, but may inflict photo-damage to the eyes. Laboratory measurements indicate that antimicrobial blue light has minimal effects on the sensorial and nutritional properties of foods, although future research using human panels is required to ascertain these findings. Food properties also affect the efficacy of antimicrobial blue light, with attenuation or enhancement of the bactericidal activity observed in the presence of absorptive materials (for example, proteins on meats) or photosensitizers (for example, riboflavin in milk), respectively. Blue light can also be coupled with other treatments, such as polyphenols, essential oils and organic acids. While complete resistance to blue light has not been reported, isolated evidence suggests that bacterial tolerance to blue light may occur over time, especially through gene mutations, although at a slower rate than antibiotic resistance. Future studies can aim at characterizing the amount and type of intracellular photosensitizers across bacterial species and at assessing the oxygen-independent mechanism of blue light-for example, the inactivation of spoilage bacteria in vacuum-packed meats.

Probabilistic topic modelling in food spoilage analysis: A case study with Atlantic salmon (Salmo salar)

Probabilistic topic modelling is frequently used in machine learning and statistical analysis for extracting latent information from complex datasets. Despite being closely associated with natural language processing and text mining, these methods possess several properties that make them particularly attractive in metabolomics applications where the applicability of traditional multivariate statistics tends to be limited. The aim of the study was thus to introduce probabilistic topic modelling - more specifically, Latent Dirichlet Allocation (LDA) - in a novel experimental context: volatilome-based (sea) food spoilage characterization. This was realized as a case study, focusing on modelling the spoilage of Atlantic salmon (Salmo salar) at 4 °C under different gaseous atmospheres (% CO₂/O₂/N₂): 0/0/100 (A), air (B), 60/0/40 (C) or 60/40/0 (D). First, an exploratory analysis was performed to optimize the model tunings and to consequently model salmon spoilage under 100% N₂ (A). Based on the obtained results, a systematic spoilage characterization protocol was established and used for identifying potential volatile spoilage indicators under all tested storage conditions. In conclusion, LDA could be used for extracting sets of underlying VOC profiles and identifying those signifying salmon spoilage, giving rise to an extensive discussion regarding the key points associated with model tuning and/or spoilage analysis. The identified compounds were well in accordance with a previously established approach based on partial least squares regression analysis (PLS). Overall, the outcomes of the study not only reflect the promising potential of LDA in spoilage characterization, but also provide several new insights into the development of data-driven methods for food quality analysis.

Changes in the Microbial Community of the Mottled Skate (Beringraja pulchra) During Alkaline Fermentation

Beringraja pulchra, Cham-hong-eo in Korean, is a mottled skate which is belonging to the cartilaginous fish. Although this species is economically valuable in South Korea as an alkalinefermented food, there are few microbial studies on such fermentation. Here, we analyzed microbial changes and pH before, during, and after fermentation and examined the effect of inoculation by a skin microbiota mixture on the skate fermentation (control vs. treatment). To analyze microbial community, the V4 regions of bacterial 16S rRNA genes from the skates were amplified, sequenced and analyzed. During the skate fermentation, pH and total number of marine bacteria increased in both groups, while microbial diversity decreased after fermentation. Pseudomonas, which was predominant in the initial skate, declined by fermentation (Day 0: 11.39 ± 5.52%; Day 20: 0.61 ± 0.9%), while the abundance of Pseudoalteromonas increased dramatically (Day 0: 1.42 ± 0.41%; Day 20: 64.92 ± 24.15%). From our co-occurrence analysis, the Pseudoalteromonas was positively correlated with Aerococcaceae (r = 0.638) and Moraxella (r = 0.474), which also increased with fermentation, and negatively correlated with Pseudomonas (r = -0.847) during fermentation. There are no critically significant differences between control and treatment. These results revealed that the alkaline fermentation of skates dramatically changed the microbiota, but the initial inoculation by a skin microbiota mixture didn't show critical changes in the final microbial community. Our results extended understanding of microbial interactions and provided the new insights of microbial changes during alkaline fermentation.

Evaluating Sardinella brasiliensis quality indicators through the quantification of histamine and bacterial communities

Primarily formed by the microbial decarboxylation of the amino acid histidine, histamine is the leading global cause of food poisoning from fish consumption worldwide. In the present work, the quality of 12 fresh and 12 frozen marketed sardines (Sardinella brasiliensis) were evaluated for histamine concentration using High-performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD), while the detection and quantification of histamine-producing bacteria were performed via quantitative Polymerase Chain Reaction (qPCR), and the microbiota composition of sardines was assessed through amplification of the 16S rRNA gene using high-throughput sequencing (HTS). According to the results obtained by HPLC-DAD, histamine concentration ranged from 226.14 to 583.87 mg kg⁻¹. The histidine decarboxylase (hdc) genes from gram-negative bacteria (Morganella morganii, and Enterobacter aerogenes) were identified. The most abundant microorganisms present in fresh sardines belong to the genera Macrococcus spp., Acinetobacter spp., and Pseudomonas spp., while the genera Phyllobacterium spp., Pseudomonas spp., and Acinetobacter spp. were most abundant in frozen sardines.

Antibacterial mechanism of the polysaccharide produced by Chaetomium globosum CGMCC 6882 against Staphylococcus aureus

GCP, a polysaccharide produced by endophytic fungus Chaetomium globosum CGMCC 6882, was found to be antibacterial against Staphylococcus aureus via disrupting cell permeability. However, the antibacterial mechanism of GCP has not been studied before. In present work, results showed that GCP could retard the growth of S. aureus by inducing the depolarization of cell membrane, decreasing the activity of Ca²⁺-Mg²⁺-ATPase on cell membrane, and increasing the accumulation of calcium ions in cytoplasm. Moreover, we found that GCP could also inhibit the synthesis of whole cell proteins of S. aureus. Overall, this study proved that the antibacterial mechanism of GCP could be diversified and more studies are needed in the investigation of the antibacterial mechanisms of various polysaccharides.

Growth and spoilage metabolites production of a mesophilic Aeromonas salmonicida strain in Atlantic salmon (Salmo salar L.) during cold storage in modified atmosphere

AIMS

The aim of the study was to quantify the growth kinetic parameters and spoilage-associated metabolites of an inoculated strain of Aeromonas salmonicida in pre-rigor filleted Atlantic salmon (Salmo salar L.) stored in vacuum (VP) or modified atmosphere (MAP 60/40% CO₂ /N₂ ) at 4 and 8°C.

METHODS AND RESULTS

The maximum growth rate of A. salmonicida in VP salmon stored at 4°C was 0·56 ± 0·04 day^-1 with no detectable lag-phase and the concentration of Aeromonas reached 8·33 log CFU per g after 10 days. The growth rates and maximum population density of Aeromonas in MAP salmon were lower but the applied atmosphere did not inhibit the growth. A selection of metabolites associated with fish spoilage were quantified using ¹ H nuclear magnetic resonance (NMR) spectroscopy. The concentration of trimethylamine (TMA) was significantly affected by storage time and temperature, packaging atmosphere and inoculation with A. salmonicida (General Linear Model (GLM), P < 0·001 for all factors).

CONCLUSION

The study presents preliminary results on A. salmonicida as a potential spoilage organism in vacuum-packaged salmon during cold storage. The combination of refrigeration and a packaging atmosphere consisting of 60/40 % CO₂ /N₂ did not completely inhibit the growth but prevented the formation of TMA.

SIGNIFICANCE AND IMPACT OF THE STUDY

Little information is available on the spoilage potential of Aeromonas spp. in minimally processed salmon products under different packaging conditions. The study clearly demonstrates the importance of hurdle technology and provides data to further elucidate the significance of Aeromonas spp. as a spoilage organism.

Effects of lysozyme combined with cinnamaldehyde on storage quality of olive flounder (Paralichthys olivaceus) fillets

Effects of lysozyme (LYS) combined with cinnamaldehyde (CA) on quality enhancement of olive flounder (Paralichthys olivaceus) fillets during refrigerated storage at 4 °C for 20 days were assessed. Changes of total viable count (TVC), K-value, total volatile basic nitrogen (TVB-N), thiobarbituric acid (TBA), texture profile analysis (TPA), and trichloroacetic acid-soluble peptide (TCA-soluble peptide) in samples were determined periodically. Results demonstrated that the combination of LYS and CA treatment enhanced the antibacterial activity against S. putrefaciens and P. fluorescens, and lowered TVC values. Meanwhile, LYS combined with CA significantly retarded the increases of TBA value, TVB-N, K-value, and TCA-soluble peptide content compared to the control. Furthermore, the combined treatment also effectively maintained the texture properties of flounder fillets during the storage period. The efficiency was better than that of LYS or CA treatment alone. Thus, LYS combined with CA is promising in olive flounder shelf life extension.

A non-invasive method for quantitative monitoring of quality changes and water migration in bigeye tuna (Thunnus obesus) during simulated cold chain logistics using low-field nuclear magnetic resonance coupled with PCA

Bigeye tuna (Thunnus obesus) is an important fish species worldwide due to its desirable flavour and rich nutrition. Cold chain logistics is one of the most common methods to store and sell bigeye tuna (Thunnus obesus). The purpose of this study was to investigate how bigeye tuna (T. obesus) deteriorate during simulated cold chain logistics with fluctuating temperatures by monitoring the quality changes and water distribution. The physical and chemical results showed that the sensory score, texture profile analysis (TPA), and water holding capacity (WHC) decreased, while total volatile basic nitrogen (TVB-N), K value, aerobic plate counts (APC), and psychrotrophic bacterial counts increased with fluctuating temperatures during 132 h. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) detection showed that the T₂₁ (trapped water) and proton density decreased, while T₂₂ (free water) decreased initially and then increased, indicating continuous water loss and water migration during storage. Principal component analysis (PCA) revealed that springiness, hardness, chewiness, T₂₁, and sensory score were correlated with each other (p < 0.05) and the linear combination of quality indicators and T₂transverse relaxation time was established. Besides, temperature fluctuation (batch 3) accelerated the deterioration of bigeye tuna according to the comprehensive score of PCA. Results were based on LF-NMR which can be used to monitor quality changes in a fast non-invasive manner.

Characterization of the Volatiles and Quality of Hybrid Grouper and Their Relationship to Changes of Microbial Community During Storage at 4 °C

To investigate the effects of spoilage bacteria on aquatic product quality and volatile organic compounds (VOCs) in hybrid grouper (Epinephelus fuscoguttatus ♀×Epinephelus lanceolatus ♂), the physical conditions were evaluated, the chemical changes including color, total volatile base nitrogen (TVB-N), VOCs, and free amino acids (FFAs) were determined, and biological profiles were made through microbial community (total viable counts (TVC), 16S rRNA gene amplification sequencing, and next-generation sequencing (NGS) technology on hybrid grouper, which were stored at 4 °C for 10 days. The results showed that the whiteness and TVB-N of grouper increased throughout the storage period. The contents of glycine, alanine, and total free amino acid decreased with the microbial activity towards the end of the study period. At the end of storage, the TVC reached 9.0 log10 (CFU/g). Seventy eight strains of bacteria were isolated from the hybrid grouper, most of which were shown to be Pseudomonas spp., after 16S rRNA sequencing. The results of the NGS test showed that the diversity of dominant bacteria decreased with time; Pseudomonas azotoformans was the dominant spoilage bacteria at the end of storage. The VOCs of fish and bacteria in the grouper's spoilage process were presented in headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Twenty eight compounds were identified in hybrid grouper, among which alcohol and aldehyde were used to characterize freshness, both of which were not only related to the overall flavor of the grouper, but were also affected by microbial activity. However, due to the complexity of microbial communities in aquatic products, the correlation between community changes and VOCs needs further research. This study provides insights into the correlation between VOCs and specific spoilage organisms (SSOs) through the analysis of the microbial community and VOCs.

An inkjet-printed sulfonephthalein dye indicator array for volatile amine detection

Colorimetric indicators are versatile for applications such as intelligent food packaging, for reflecting the actual quality and/or monitoring distribution history of food products. In this study, a colorimetric indicator array composed of sulfonephthalein dyes was successfully developed by piezoelectric inkjet printing, for the detection of volatile amines-the primary spoilage gases for fish and seafood products. The printing inks were formulated in water/ethanol/1-butanol mixture. By refilling the printer's cartridges with our formulated inks and controlling the red, green, and blue color parameters, a 7 × 9 indicator array was printed onto inkjet transparency films. The color response of the indicator array was tested with different volatile amines at various concentrations. The array indicator was capable of discriminating six different volatile amines: ammonia, trimethylamine, dimethylamine, triethylamine, piperidine, and hydrazine. The printability of the inks was investigated by characterizing their density, surface tension, and dynamic viscosity, dictating that all formulated inks were printable fluid. The microstructural morphologies of the printed dyes on transparency films were evaluated using scanning electron microscopy. Interactions of the dye with the volatiles were studied by Fourier transform infrared spectroscopy. In summary, the piezoelectric inkjet printing method presented in this study offers a convenient, efficient, and flexible means to fabricate colorimetric indicators for detecting food spoilage volatiles. These indicators are promising as sensing components in intelligent packaging systems, to reveal the freshness of fish products by correlating with quality parameters such as total volatile basic nitrogen, microbial growth, and sensory attributes. Further studies on the feasibility of using the array indicators in real food packaging systems, development of strategy to mitigate the potential migration of the indicator dyes, and designing array patterns optimal for machine/human interpretation, are important to commercialize the technology. PRACTICAL APPLICATION: Piezoelectric inkjet printing offers a convenient way to fabricate sensing materials and aligns with industrial packaging operations. The use of indicators on food package helps consumers more accurately perceive real-time food quality information.

Understanding spoilage microbial community and spoilage mechanisms in foods of animal origin

The increasing global population has resulted in increased demand for food. Goods quality and safe food is required for healthy living. However, food spoilage has resulted in food insecurity in different regions of the world. Spoilage of food occurs when the quality of food deteriorates from its original organoleptic properties observed at the time of processing. Food spoilage results in huge economic losses to both producers (farmers) and consumers. Factors such as storage temperature, pH, water availability, presence of spoilage microorganisms including bacteria and fungi, initial microbial load (total viable count-TVC), and processing influence the rate of food spoilage. This article reviews the spoilage microbiota and spoilage mechanisms in meat and dairy products and seafood. Understanding food spoilage mechanisms will assist in the development of robust technologies for the prevention of food spoilage and waste.

Transcriptome and Volatilome Analysis During Growth of Brochothrix thermosphacta in Food: Role of Food Substrate and Strain Specificity for the Expression of Spoilage Functions

Brochothrix thermosphacta is one of the main spoilers in food, responsible for meat and seafood spoilage through the production of malodorous volatile organic compounds. The molecules produced by this bacterium depend on the substrate (meat or seafood) and the storage conditions such as gas mixtures used in the packaging. It seems also that the spoilage potential is strain dependent as production of diacetyl and acetoin, two molecules responsible for seafood spoilage, varies with strains. Therefore, this suggests the involvement of different metabolic functions depending on both food substrate and strain capacities. In this study, we selected two strains with different abilities to produce diacetyl and acetoin and compared their behavior after grown in beef or cooked peeled shrimp juices. We determined the genes upregulated by both strains depending on the growth substrate and those that were specifically upregulated in only one strain. The genes upregulated by both strains in meat or in shrimp juice revealed the importance of the substrate for inducing specific metabolic pathways. The examination of genes that were specifically upregulated in only one of the two strains revealed strain features associated to specific substrates and also strain-specific regulations of metabolic pathways putatively leading to different levels of spoilage molecule production. This shows that the spoilage potential of B. thermosphacta depends on nutrients provided by food substrate and on metabolic activity potential that each strain possesses.

Effect of low-temperature preservation on quality changes in Pacific white shrimp, Litopenaeus vannamei: a review

Shrimp has been widely accepted as an excellent resource for white meat due to its high-protein and low-fat content, especially low cholesterol. However, shrimps are highly perishable during preservation and retailing procedures due to the activities of enzymatic proteolysis, lipid oxidation, and microbial degradation. With increasing knowledge of and demands for safety, nutrition, and freshness of shrimp products, energy efficient, quality, maintained, and sustainable preservation technologies are needed. Low-temperature preservation, a practical processing method for improving the shelf life of food products, is widely used in the aquatic industry. This review focuses on the effects of low-temperature preservation on the quality changes in Litopenaeus vannamei. It considers physicochemical properties, sensory evaluation, melanosis assessment, and microbiological analysis. The perspectives of non-protein-based techniques on quality analysis of shrimps during preservation are also discussed. © 2019 Society of Chemical Industry.

Natural products with preservative properties for enhancing the microbiological safety and extending the shelf-life of seafood: A review

Seafood is highly perishable, presenting a rapid loss of its quality soon after capture. Temperature is the critical parameter that impacts on seafood shelf-life reduction, allowing the growth of foodborne pathogens and spoilage microorganisms. In recent years, the search by additional methods of preserving seafood has increased, able to ensure quality and safety. Several natural preservatives have highlighted and gained considerable attention from the scientific community, consumers, industry, and health sectors as a method with broad action antimicrobial and generally economical. Natural preservatives, from different sources, have been widely studied, such as chitosan from animal sources, essential oils, and plant extracts from a plant source, lactic acid bacteria, and bacteriocins from microbiological sources and organic acid from different sources, all with great potential for use in seafood systems. This review focuses on the natural preservatives studied in seafood matrices, their forms of application, concentrations usually employed, their mechanisms of action, factors that interfere in their use and the synergistic effect of the interactions among the natural preservatives, with a focus for maintenance of quality and ensure of food safety.

Characterization of the Spoilage Microbiota of Hake Fillets Packaged Under a Modified Atmosphere (MAP) Rich in CO2 (50% CO2/50% N2) and Stored at Different Temperatures

The aim of this study was to characterize the spoilage microbiota of hake fillets stored under modified atmospheres (MAP) (50% CO₂/50% N₂) at different temperatures using high-throughput 16S rRNA gene sequencing and to compare the results with those obtained using traditional microbiology techniques. The results obtained indicate that, as expected, higher storage temperatures lead to shorter shelf-lives (the time of sensory rejection by panelists). Thus, the shelf-life decreased from six days to two days for Batch A when the storage temperature increased from 1 to 7 °C, and from five to two days—when the same increase in storage temperature was compared—for Batch B. In all cases, the trimethylamine (TMA) levels measured at the time of sensory rejection of hake fillets exceeded the recommended threshold of 5 mg/100 g. Photobacterium and Psychrobacter were the most abundant genera at the time of spoilage in all but one of the samples analyzed: Thus, Photobacterium represented between 19% and 46%, and Psychrobacter between 27% and 38% of the total microbiota. They were followed by Moritella, Carnobacterium,Shewanella, and Vibrio, whose relative order varied depending on the sample/batch analyzed. These results highlight the relevance of Photobacterium as a spoiler of hake stored in atmospheres rich in CO₂. Further research will be required to elucidate if other microorganisms, such as Psychrobacter, Moritella, or Carnobacterium, also contribute to spoilage of hake when stored under MAP.

Defining the Distinct Skin and Gut Microbiomes of the Northern Pike (Esox lucius)

The microbiome of freshwater fish has important implications for both commercial and recreational fishing because it can have significant impacts on host heath, spoilage rates, and susceptibility to disease. The aqueous environment serves as a possible avenue for continuous introduction of microbes to an animal host, but little is known about how the surrounding microbiota contribute to piscine microbiomes. To better understand the composition of the fish microbiome exposed to the natural environment, we profiled the microbial composition of the gut and the skin mucosal surface (SMS) of northern pike (Esox lucius) and the surrounding river water. We collected fish samples from eight sites along a single river in southwestern Quebec, Canada and analyzed the microbial composition via 16S rRNA sequencing. Our results reveal robust taxonomic differences between the SMS and the gut, indicating a divergence between the microbiomes. The gut community was characterized by a lower alpha diversity compared to the SMS and a large proportion of Cetobacterium, a genus previously linked to carnivorous species. On the other hand, the SMS was more similar to the water than the gut at the family level but divergent at lower taxonomic levels, with fewer than 30% of amplicon sequence variants (ASVs) shared between the SMS and water. In total, our results suggest the establishment of distinct communities across the two fish sites, as well as a clear separation from the microbes in surrounding waters. These data indicate that despite continuous exposure to water, pike are able to establish and maintain unique microbial communities.

Study on the Volatile Organic Compounds and Its Correlation with Water Dynamics of Bigeye Tuna (Thunnus obesus) during Cold Storage

Volatile organic compounds (VOCs) and water play a key role in evaluating the quality of aquatic products. Quality deterioration of aquatic products can produce some off-odour volatiles and can induce water content changes. However, no previous study has investigated a correlation between water dynamics and VOCs of bigeye tuna during cold storage. The changes in VOCs, water dynamics and quality attributes of bigeye tuna (Thunnus obesus) upon storage at 0 °C and 4 °C for 6 days were investigated. The results showed that the values of ATP, adenosine diphosphate (ADP), adenosine monophosphate (AMP), T₂₁ (trapped water) and the relative value of T₁ decreased (p < 0.05), while drip loss and histamine contents increased (p < 0.05), which indicated quality deterioration during cold storage. With haematoxylin and eosin (HE) staining, muscle tissue microstructure was observed. VOCs such as hexanal, heptanal, 4-Heptenal, (Z)-, pentadecanal-, 1-pentanol, 1-hexanol significantly increased, which sharply increased the content of off-odour volatiles. T₂₁ was positively correlated with 1-octen-3-ol, 1-penten-3-ol, while T₂₁ was negatively correlated with hexanal, 1-hexanol. Therefore, good correlations between water dynamics and some VOCs were detected during quality deterioration of bigeye tuna throughout cold storage.