Programmable printing of a colorimetric sensor array mimicking human olfactory system for real-time detection of meat freshness

Concerning the massive economic loss and potential food-borne diseases due to meat spoilage, real-time and non-destructive surveillance techniques able to provide early spoilage alert became increasingly important in meat supply chain. Here, a colorimetric sensor array (CSA) consisted of 10 amine-responsive dyes encapsuled in a metal−organic framework material ZIF-8 (ARD@ZIF-8) mimicking human olfactory system was designed and fabricated for visual evaluation of meat freshness. It was demonstrated that the encapsulation in ZIF-8 significantly enhanced the sensitivity and stability (ΔE < 5) of amine-responsive dyes. Then, the CSA in size of 40 × 10 mm was prepared by programmable printing with high precision and uniformity. Upon a short exposure within 16 min to biogenic amines (BAs), sensitive colorimetric changes became straightforward for eye-inspection, which was further digitally documented and quantified with a smartphone. The detection linear range for the targeted BAs (ammonia, dimethylamine, trimethylamine) was 50–50000 μg/kg, with limits of detection at 7, 8, and 8 μg/kg, respectively. Furthermore, the optimized detection was validated with different meat samples, agreeing well with the data by the TVBN assay (R² > 0.969). Via chemoichiometric pattern recognition (principal component analysis and hierarchical cluster analysis), the status of meat freshness at different shelf-life stages could be clearly distinguished. Moreover, the CSA displayed high reproducibility (RSD <5 %) as well. Reaching an ideal balance in simplicity, reliability and cost-efficiency, the CSA might be valuable to next generation of intelligent food package enabling consumer-level monitoring of meat quality.