| Summary: | Real-time monitoring of meat quality requires fast, accurate, low-cost, and non-destructive analytical methods that can be used throughout the entire production chain, including the packaged product. The aim of this work was to evaluate the potential of a portable near-infrared (NIR) spectroscopy tool for the on-site detection of freshness of pork loin fillets in modified atmosphere packaging (MAP) stored on display counters. Pork loin slices were sealed in MAP trays under two proportions of O<sub>2</sub>/CO<sub>2</sub>/N<sub>2</sub>: High-Ox-MAP (30/40/30) and Low-Ox-MAP (5/20/75). Changes in pH, color, thiobarbituric acid reactive substances (TBARS), Warner–Bratzler shear force (WBSF), and microbiology (total viable counts, <i>Enteriobacteriaceae</i>, and lactic acid bacteria) were monitored over 15 days post-mortem at 4 °C. VIS-NIR spectra were collected from pork fillets before (through the film cover) and after opening the trays (directly on the meat surface) with a portable LABSPEC 5000 NIR system in diffuse reflectance mode (350–2500 nm). Quantitative NIR models by partial least squares regression (PLSR) showed a promising prediction ability for meat color (<i>L*</i>, <i>a*</i>, <i>C*</i>, and <i>h*</i>) and microbiological variables (R<sup>2</sup><sub>VAL</sub> > 0.72 and RPD<sub>VAL</sub> > 2). In addition, qualitative models using PLS discriminant analysis obtained good accuracy (over 90%) for classifying pork samples as fresh (acceptable for consumption) or spoiled (not acceptable) based on their microbiological counts. VIS-NIR spectroscopy allows rapid evaluation of product quality and shelf life and could be used for on-site control of pork quality.
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