Highly sensitive fluorometric ammonia detection utilizing Solenostemon scutellarioides (L.) extracts in MOF-tragacanth gum hydrogel for meat spoilage monitoring

Efficient monitoring of ammonia levels in meat products is imperative to uphold food safety, and quality control, and mitigate health risks associated with spoilage. Herein, we introduce a non-destructive and portable fluorometric assay designed for on-site ammonia monitoring —a critical biomarker for spoiled meat products. This assay incorporates a gum tragacanth-based hydrogel embedded with a MOF and natural dyes derived from Solenostemon scutellarioides (L.) plants. A thorough characterization of the sensor validates its exceptional chemical and photophysical stability, water permeability, hydrophobicity, commendable crystallinity, and desirable morphology. To enable real-time analysis, customized smartphone applications tailored for online signaling and fluorometric analysis were developed. The sensor displays two linear ranges for ammonia detection: 0-5.42 ppm and 5.42-80.47 ppm, boasting a detection limit of 49.6 ppb. Furthermore, the sensor demonstrates outstanding selectivity in the presence of other volatile organic compounds (VOCs) and humidity. It showcases acceptable repeatability both interday (RSD=3.65%) and intraday (RSD=3.012%), along with prolonged stability (5 days). The sensing platform has been successfully applied to monitor ammonia in spoiled veal, fish, and chicken. This research contributes valuable insights for the design and development of solid-state sensors and straightforward packaging indicators, enabling the monitoring of food freshness through smartphone-based online signaling and data analysis.