Point-of-Care Meat Freshness Evaluation: Myoglobin-Involved Redox Reaction Analysis via Smartphone Imaging

Meat freshness is essential for ensuring food safety and protecting consumer health. However, substantial resource waste often occurs when consumers rely on their senses to assess meat. Herein, we developed a smartphone-based platform utilizing the biocompatible redox indicator resazurin to visualize meat freshness through specific redox reactions. Spectrophotometric and coloration analysis confirmed that myoglobin (Fe²⁺) exhibits reducing activity, with higher Fe²⁺ content in fresh meat that correlates to stronger reducing capacity. This enhanced reducing capability produces more distinct color transitions as resazurin (blue) is reduced to resorufin (pink). Combined with color heatmaps extracted from RGB data of smartphone images, our approach has successfully evaluated the freshness of pork, beef, and chicken within 30 min, demonstrating its broad applicability and rapid detection capability. This low-cost (<$0.02 per test), nontoxic, and user-friendly (no instruments needed) visualization method shows great promise for promoting home-based meat freshness testing, thereby reducing resource waste while safeguarding consumer health.