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

Interactions with alloparents are associated with the diversity of infant skin and fecal bacterial communities in Chicago, United States

INTRODUCTION

Social interactions shape the infant microbiome by providing opportunities for caregivers to spread bacteria through physical contact. With most research focused on the impact of maternal-infant contact on the infant gut microbiome, it is unclear how alloparents (i.e., caregivers other than the parents) influence the bacterial communities of infant body sites that are frequently contacted during bouts of caregiving, including the skin.

METHODS

To begin to understand how allocare may influence the diversity of the infant microbiome, detailed questionnaire data on infant-alloparent relationships and specific allocare behaviors were coupled with skin and fecal microbiome samples (four body sites) from 48 infants living in Chicago, United States.

RESULTS

Data from 16S rRNA gene amplicon sequencing indicated that infant skin and fecal bacterial diversity showed strong associations (positive and negative) to having female adult alloparents. Alloparental feeding and co-sleeping displayed stronger associations to infant bacterial diversity compared to playing or holding. The associations with allocare behaviors differed in magnitude and direction across infant body sites. Bacterial relative abundances varied by infant-alloparent relationship and breastfeeding status.

CONCLUSION

This study provides some of the first evidence of an association between allocare and infant skin and fecal bacterial diversity. The results suggest that infants' exposure to bacteria from the social environment may vary based on infant-alloparent relationships and allocare behaviors. Since the microbiome influences immune system development, variation in allocare that impacts the diversity of infant bacterial communities may be an underexplored dimension of the social determinants of health in early life.

Microbiome dynamics, antibiotic resistance gene patterns and spoilage-associated genomic potential in fresh anchovies stored in different conditions

Fresh fish is a highly perishable product and is easily spoiled by microbiological activity and chemical oxidation of lipids. However, microbial spoilage is the main factor linked with the rapid fish sensorial degradation due to the action of specific spoilage organisms (SSOs) that have the ability to dominate over other microorganisms and produce metabolites responsible for off-flavours. We explored the microbial dynamics in fresh anchovies stored in different packaging (air, modified atmosphere, under vacuum) and temperatures (0, 4 and 10 °C) using shotgun metagenomics, highlighting the selection of different microbial species according to the packaging type. Indeed, Pseudoalteromonas nigrifaciens, Psychrobacter cryohalolentis and Ps. immobilis, Pseudomonas deceptionensis and Vibrio splendidus have been identified as the main SSOs in aerobically stored anchovies, while Shewanella baltica, Photobacterium iliopiscarium, Ps. cryohalolentis and Ps. immobilis prevailed in VP and MAP. In addition, we identified the presence of spoilage-associated genes, leading to the potential production of biogenic amines and different off-flavors (H2S, TMA). In particular, the abundance of microbial genes leading to BA biosynthesis increased at higher storage temperature, while those related to H2S and TMA production were enriched in aerobically and VP packed anchovies, suggesting that MAP could be an effective strategy in delaying the production of these compounds. Finally, we provided evidence of the presence of a wide range of antibiotic resistance genes conferring resistance to different classes of antibiotic (β-lactams, tetracyclines, polymyxins, trimethoprims and phenicols) and highlighted that storage at higher temperature (4 and 10 °C) boosted the abundance of ARG-carrying taxa, especially in aerobically and MAP packed fish.

Extending the Shelf Life of Atlantic Salmon (Salmo salar) with Sub-Chilled Storage and Modified Atmosphere Packaging in Recyclable Mono-Material Trays

This study investigated the effect of sub-chilling whole gutted salmon and sub-chilled storage at -1 °C in modified-atmosphere packaging in two recyclable mono-material trays (CPET, HDPE). Quality parameters were measured, including water-holding properties, salt content, color, texture, lipid oxidation, and sensory and microbiological shelf life. The oxygen transmission rate was measured for the packages. Compared to traditional fish storage on ice, sub-chilling gave a 0.4% weight gain, better water-holding capacity, and higher salt content. The sub-chilled fish gave a significantly better sensory quality and microbiological shelf life of up to 49 days. Photobacterium was the dominating bacteria during storage. Salmon packaged in CPET trays had a higher drip loss than HDPE trays, but a lower rate of lipid oxidation (1-penten-3-ol). Our results showed the feasibility of significantly extending shelf life with sub-chilling, removing the need for ice. Moreover, using recyclable trays for packaging contributes to a circular economy without compromising food quality.

Selection of lactic acid bacteria for biopreservation of salmon products applying processing-dependent growth kinetic parameters and antimicrobial mechanisms

Biopreservation using lactic acid bacteria (LAB) is a promising technology to prevent the growth of pathogenic microorganisms in fresh and mildly processed food. The main aim of this study was to select LAB, originally isolated from ready-to-eat (RTE) seafood, for biopreservation of fresh salmon and processed salmon products. Ten LAB strains (five Carnobacterium and five Leuconostoc) were selected based on previously demonstrated bioprotective properties to investigate their antimicrobial mechanisms and temperature-dependent growth kinetics in a sterile salmon juice model system. Furthermore, five strains (three Carnobacterium and two Leuconostoc) were selected to test process-dependent growth kinetic parameters relevant to the secondary processing of salmon. Two strains (Carnobacterium maltaromaticum 35 and C. divergens 468) showed bacteriocin-like activity against Listeria innocua, while inhibitory effect of cell-free supernatants (CFS) was not observed against Escherichia coli. All selected strains were able to grow in sterile salmon juice at tested temperatures (4, 8, 12 and 16 °C), with specific growth rates (μ) ranging from 0.01 to 0.04/h at 4 °C and reaching a maximum population density of 8.4-9 log CFU/ml. All five strains tested for process-dependent growth kinetic parameters were able to grow in the range of 0.5-5% NaCl and 0.13-0.26% purified condensed smoke (VTABB and JJT01), with inter- and intraspecies variation in growth kinetics. According to the temperature-dependent growth kinetics and antimicrobial assay results, two strains, Leuconostoc mesenteroides 68 (Le.m.68) and C. divergens 468 (C d.468), were selected for in situ test to validate their ability to grow in vacuum-packed fresh salmon at 4 °C. Both strains were able to grow at maximum growth rates of 0.29 ± 0.04/d for Le. m.68 and 0.39 ± 0.06/d for C.d.468, and their final concentrations were 7.91 ± 0.31 and 8.02 ± 0.25 log CFU/g, respectively. This study shows that LAB, originally isolated from RTE seafood, have promising potential as bioprotective strains in fresh and processed salmon products.

Growth and Spoilage Potential of an Aeromonas salmonicida Strain in Refrigerated Atlantic Cod (Gadus morhua) Stored under Various Modified Atmospheres

Aeromonas spp. are ubiquitous aquatic bacteria, frequently isolated from seafood. The growth and spoilage potential of an inoculated strain of Aeromonas salmonicida (SU2) in Atlantic cod (Gadus morhua) fillets were assessed as a function of various modified atmospheres (MA) (CO2 (67%) with O2 (33%) or N2 (33%), and vacuum packaging (VP)) under refrigerated storage (4 °C) for 13 days. Additionally, the general microbiological quality was assessed by quantifying total aerobic psychrotrophic count (PC), total aerobic plate count (APC), and H2S-producing bacteria. A selection of spoilage metabolites was quantified by nuclear magnetic resonance (NMR) spectroscopy. The MA containing CO2/O2 and CO2/N2 significantly inhibited the growth of the inoculated strain throughout storage (p < 0.001), whereas VP allowed for a 3-log increase of Aeromonas in 13 days. No significant effect of the inoculation with A. salmonicida on spoilage metabolite production was detected. Applying O2 instead of N2 in the CO2-enriched atmosphere resulted in a significantly lower PC for 10 days, and H2S-producing bacteria were inhibited in both MAs compared to vacuum. This study provides data that can be used as a basis to further elucidate the role of bacteria belonging to the genus Aeromonas as potential spoilage organisms in marine fish species.

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

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