Figure 6.

Meat spoilage tracking using the proposed AOS. a) Transient ΔV _outs during the spoilage of chicken tenderloin. The images of the food are shown in the insets. b) ΔI _BLs, system‐inferred NH₃ gas concentration, commercial electrochemical sensor‐inferred NH₃ gas concentration, TD‐GC‐inferred H₂S gas concentration, system‐inferred H₂S gas generation time, and freshness score during food spoilage. The NH₃ gas concentrations in the ranges of 0.01–0.5 ppm and 0.5–5 ppm are inferred using I _ref−I _BL1 and I _BL3−I _BL2, respectively. The generation of H₂S gas is inferred using the change in the sign of I _BL5−I _BL4 from negative to positive. The freshness score is calculated using Score = 100−150 ×  NH₃ gas concentration. If the food generates >0.5 ppm of NH₃ gas, a freshness score of 0 is assigned. c) Method of classifying the food condition using the three outputs of the AOS as binary signals. The system provides binary signals whether 1) the NH₃ gas concentration is >0.01 ppm (low conc. NH₃ alarm, yellow line), 2) the NH₃ gas concentration is >0.5 ppm (High conc. NH₃ alarm, orange line), and 3) H₂S gas is generated (H₂S alarm, red line). By using three binary signals, the food conditions are labeled fresh (000), edible (100), spoiled (110), and completely spoiled (111).