Leqi Cui

High oxygen‐permeable vacuum skin packaging (10K VSP) is widely used for frozen seafood distribution to mitigate anaerobic pathogen risks, yet post‐thaw microbial dynamics during refrigerated display remain poorly characterized. This study evaluated post‐thaw microbial quality and bacterial community succession across 10 commercially frozen‐then‐thawed seafood species held under simulated retail refrigeration (4°C) on Days 1, 5, and 9. Aerobic plate counts, lactic acid bacteria, and coliform/ Escherichia coli indicator counts were determined, and bacterial communities were characterized using high‐throughput 16S rRNA gene sequencing. Average aerobic plate counts increased from 3.57 ± 1.03 log CFU/g on Day 1 to 6.00 ± 0.84 log CFU/g on Day 5 and 7.30 ± 0.64 log CFU/g on Day 9, although growth patterns differed among seafood products. Several products reached or exceeded microbial acceptability limits by Day 5 or Day 9. Sequencing revealed an ecological transition from initial Photobacterium and Psychrobacter dominance to a shift toward spoilage‐associated genera, particularly Pseudomonas and Brochothrix , during refrigerated storage under the tested oxygen‐permeable VSP condition. These findings provide study‐specific information on post‐thaw microbial changes in 10K VSP seafood products that may help inform future refrigerated handling and display recommendations.

Mass transport in oil-in-water (O/W) emulsions has been gaining attention. Among the proposed mechanisms, micelle-mediated transfer has emerged as a key pathway, but direct evidence remains limited. In this study, Förster resonance energy transfer (FRET) was employed to investigate mass transport through emulsifier micelles in O/W emulsions. FRET between fluorescein (FL)-loaded and octadecyl rhodamine B chloride (RB)-loaded emulsions was confirmed by decreased FL emission (524 nm) and increased RB emission (582 nm) once mixed. To further elucidate the action of micelles, FL-loaded emulsions were mixed with RB-loaded cetyltrimethylammonium bromide (CTAB) solutions below and above the critical micelle concentration (CMC) of CTAB. Results showed a simultaneous decrease in relative FL emission (up to 48.85%) and increase in RB emission (up to 1396.74%) with increasing CTAB concentration, confirming FRET. However, only limited changes were observed above the CMC of CTAB. These findings provide direct spectroscopic evidence of micelle-mediated mass transport in emulsions.

Gastrointestinal digestion and colonic fermentation determine phenolic transformation and reciprocal microbiome modulation, influencing the generation of gut-derived metabolites associated with epithelial integrity, inflammatory regulation, and metabolic homeostasis. Baby spinach phenolics possess antioxidant and microbiome-modulating potential; however, their functional efficacy is constrained by storage-induced degradation and limited gastrointestinal bioaccessibility. This study investigated phenolic transformation in fresh and stored baby spinach (4 °C and 25 °C) during simulated gastrointestinal digestion and subsequent colonic fermentation. Standardized in vitro digestion revealed limited phenolic bioaccessibility (10–15%), with storage at 25 °C accelerating oxidative degradation and reducing antioxidant capacity. Storage at 25 °C reduced TPC from approximately 465 to 265 µg GAE/g and decreased antioxidant activity by nearly 30%, whereas refrigerated storage (4 °C) better preserved phenolic stability and antioxidant capacity throughout the storage period. LC–MS/MS–based untargeted metabolomics characterized digestion-driven structural remodeling and identified diverse colonic metabolites generated during human fecal fermentation. Despite storage-induced alterations in precursor phenolics, 16S rRNA sequencing demonstrated microbiome relative microbial stability, with fermentation time exerting a stronger influence on community assembly than storage conditions. Microbial metabolism produced shared downstream metabolites, particularly phenylpropionic and flavonoid-derived intermediates. These results suggest that storage modifies phenolic availability during digestion, while gut microbial metabolism sustains the production of functionally relevant metabolites.

Emulsifier micelles have been reported to play a crucial role in influencing lipid oxidation in oil-in-water (O/W) emulsions. Meanwhile, previous studies found that salts can alter antioxidant distribution in emulsions by altering micelle formation. However, direct evidence of such an effect is lacking. In this study, we report a 1H NMR and 1D NOESY-based method to demonstrate that salts (NaCl and KCl) can influence micellar interactions between antioxidants (Trolox or α-tocopherol) and emulsifiers (cetyltrimethylammonium bromide (CTAB) or Tween 20). For both CTAB and Tween 20, whose critical micelle concentrations decrease upon salt addition, 1D NOESY spectra in salt-containing systems showed peaks at 0.8 ppm and 3.2 ppm (CTAB tail and head), and 1.2 ppm and 3.6 ppm (Tween 20 tail and head), indicating spatial proximity between antioxidants and specific micellar domains. In contrast, without salt, no such peaks were observed, suggesting the absence of spatial association between antioxidants and emulsifiers.

Vacuum skin packaging (VSP) has emerged as an innovative solution to enhance the safety and freshness of seafood and extend the shelf life of food products. However, its efficacy on seafood products remains completely underexplored. This study aims to evaluate the shelf life and characterize the microbial community dynamics of 10 oxygen permeable skin packed seafood products during refrigeration. Vacuum skin-packed flounder, mahi, perch, salmon, scallop, shrimp, snapper, swai, tilapia, and tuna were collected from a seafood processor in Florida. Samples were defrosted at 4°C and evaluated on days 1, 5, and 9 for aerobic, coliform, and lactic acid bacteria counts. Microbial DNA from samples was extracted and used to characterize bacterial community dynamics during storage. The sequencing data were analyzed using the CLC Genomics Workbench. On day 1, the average aerobic plate count for all 10 samples was 3.5 log CFU/g, which increased to 6 log CFU/g by day 5 and reached 7.5 log CFU/g by day 9. The overall enumeration data indicate that the seafood samples exceeded the spoilage thresholds established by the FDA and FAO by day 5 under refrigeration. Sequencing data revealed Photobacterium, Psychrobacter, Pseudomonas, and Brochothrix as the dominant bacterial genera across most seafood species. Notably, Pseudomonas emerged as the predominant genus by day 5, surpassing all other bacterial genera in abundance. These data provide evidence-based refrigerated handling guidance for oxygen-permeable VSP seafood that processors and retailers can use to manage display time, thereby reducing spoilage-related losses and protecting consumers.

In the United States, testing data indicate that up to 30% of shrimp sold are misrepresented. Among species harvested from U.S. waters, royal red shrimp (Pleoticus robustus) is one of the most valued and is therefore frequently substituted with Argentine red shrimp (Pleoticus muelleri). This study developed and validated an RNase H‑dependent polymerase chain reaction (rhPCR) assay to accurately distinguish P. robustus from P. muelleri. Primer pairs targeting the COI gene were designed, screened for specificity, and subsequently converted into RNase H2‑activated primers labeled with FAM and biotin for lateral‑flow detection. The optimized assay was validated using genomic and crude DNA extracted from 65 barcoded shrimp tissue samples representing seven commercially relevant species: L. setiferus, L. vannamei, P. aztecus, P. duorarum, P. monodon, P. muelleri, and P. robustus. To assess real‑world performance, the assay was further applied to 20 blinded retail samples marketed as royal red shrimp and collected by a state food‑safety division. Results revealed a 60% species‑substitution rate, with 30% of samples identified as P. muelleri, demonstrating the assay’s effectiveness for detecting mislabeling in commercial products. The assay achieved 100% specificity, correctly differentiating royal red and Argentine red shrimp from all non‑target species. Analytical sensitivity reached 0.1 ng/µL for P. robustus and 0.01 ng/µL for P. muelleri crude DNA, with a total turnaround time of 150 minutes for processing 20 samples. These assays provide enforcement agencies with a robust, field‑deployable method for detecting royal red shrimp substitution and supporting evidence‑based regulatory decisions.