Shandong Agricultural University

Portable, ultra-sensitive, and highly specific detection of foodborne pathogens is significant for food safety. Here, we designed a portable PEC biosensor based on a Bi₇O₉I₃/In₂O₃ type-II heterojunction combined with an isothermal amplification strategy, realizing on-site PEC and colorimetric dual-mode quantitative detection of Escherichia coli O157:H7 (E. coli O157:H7) in milk using Zr-MOF nanozyme. By utilizing a very small U-disk electrochemical workstation with a portable LED lamp as the light source, a portable PEC biosensor was achieved with excellent sensitivity (10^0.3-10^7.2 CFU/mL), low limit of detection (2 CFU/mL), outstanding stability, selectivity and reproducibility. In addition, a colorimetric assay for E. coli O157:H7 was developed based on the phosphatase-like activity of Zr-MOF nanozyme, which hydrolyze 4-nitrophenyl phosphate to produce 4-nitrophenol. The output dual-signals from U-disk electrochemical workstation and RGB values were captured by smartphone-compatible Bluetooth, thus accomplishing on-site testing of E. coli O157:H7 in milk. To validate the suitability of the portable PEC biosensor, a variety of dairy products were spiked for quantitative detection and all showed excellent recoveries, which demonstrated the great potential application of portable PEC analysis for field testing.

This research explored the role of peroxiredoxin 6 (Prdx6)-mediated non‑selenium glutathione peroxidase (NSGPx) activity in modulating the tenderization process of beef during post-mortem aging, extending up to 168 h. Shear force, NSGPx activity, differential protein abundance, heat shock proteins (HSP70, HSP27), and troponin-T levels were analyzed in beef longissimus lumborum muscles treated with hydrogen peroxide (H₂O₂), N-acetylcysteine (NAC), mercaptosuccinic acid (MA), or saline (Control). MA treatment inhibited NSGPx activity and accelerated tenderization compared to NAC. Proteomics revealed that proteins differentially abundant between 0 and 24 h post-mortem were linked to cytoskeleton, extracellular matrix, amino acid metabolism, and apoptosis pathways.MA upregulated HSP70 abundance, oxidative stress, and troponin-T breakdown. H₂O₂ upregulated HSP70 and HSP27 abundance only within 6-12 h post-mortem. These results demonstrate that oxidative stress treatments modulate protein dynamics during aging, offering insights into strategies to enhance beef tenderness. SIGNIFICANCE: This study highlights peroxiredoxin 6 (Prdx6) as a crucial regulatory element that affects oxidative stress-associated pathways involved in the meat tenderization process during post-mortem beef aging. We demonstrate that inhibiting Prdx6's on‑selenium glutathione peroxidase (NSGPx) enzymatic activity with mercaptosuccinic acid (MA) increases HSP70 abundance and accelerates troponin-T proteolysis through enhanced oxidative stress and calcium signaling pathways. Conversely, antioxidant N-acetylcysteine (NAC) delays tenderization by preserving cytoskeletal integrity. Our TMT-based proteomics further identifies 35 core proteins linking extracellular matrix remodeling, amino acid metabolism, and apoptosis to tenderness modulation. These findings provide the first mechanistic evidence that targeted manipulation of Prdx6 activity can optimize beef aging efficiency. For the meat industry, MA treatment offers a science-driven strategy to reduce tenderization time by >20 % within 24-72 h post-mortem, lowering processing costs while maintaining quality. This work also establishes HSP70 and troponin-T degradation as novel biomarkers for real-time monitoring of oxidative stress in meat processing systems.