Real-time monitoring the freshness of food that stored in refrigerator is of great significance to alarm the potential food spoilage and prevent severe health problems. Among those frequently reported methods, discriminating the food freshness through tracking volatile compounds receives extensive attention. Nevertheless, the ambient environment of low temperature (normally below 4oC) and high humidity (90% R.H.) as well as poor selectivity in sensing gas species still remain the challenge. In this research, an integrated smart gas tracking device is deigned and fabricated. Through applying pump voltage on an yttria-stabilized zirconia (YSZ) membrane, oxygen concentration in the testing chamber can be manually tailored. Due to working principle of the sensor follows the mixed potential behavior, distinct difference in sensitivity and selectivity are observed for the sensor that operated at different oxygen concentration. Typically, the sensor gives satisfactory selectivity to H2S, NH3, C2H5OH at the oxygen concentration of 10%, 30% and 40%, respectively. In addition, acceptable response/recovery rate (within 24 s) is also confirmed. Finally, a refrigerator prototype that includes the smart gas sensor is built, and satisfactory performance in discriminate food freshness status of fresh or semi-fresh is verified for the proposed refrigerator prototype. In conclusion, these aforementioned promising results suggest that the proposed integrated smart gas sensor could be a potential candidate for alarming food spoilage.