Carbon Black Polymer Sensor Array for Incipient Grain Spoilage Monitoring

Sensor arrays are currently used for classifying liquors, perfumes, and the quality of food products by mimicking the mammalian olfactory system. The use of this technology for the monitoring of stored grains and identifying the source of spoilage is a new application, which has the potential for broad economic impact. Carbon black polymer sensor array was fabricated and optimized for monitoring of incipient grain spoilage in a simulated stored grain bin. Various aspects of sensor array (flow rate, relative humidity, temperature, presence of background gas) were evaluated at stored grain conditions. Sensor response at low concentration (2% of vapour pressure) of 1-octanol, 1,4-benzoquinone, acetone was checked in presence of water vapour and 400 ppmv CO2 as background. Slightly variable sensor responses were observed compared to in absence of background gases. The responses were decreased by 6-15% on an average for poly(vinyl acetate), poly(bisphenol-A-carbonate) and poly(vinyl butaryl) sensor while exposed in presence of 50% water vapour. Polymers with high sensitive to background gases (H2O and CO2), such as PVP and P4VP were excluded from the array in this study. Co-polymers with styrene showed low sensitivity drop compared to non-styrene copolymers based on 9 months observation. Therefore, styrene copolymer sensors were best suited to build a stable sensor for the sensor array. Selected polymers for the sensor array retained their sensing properties despite being stored under a wide range of temperatures (-20 to 25 degrees C). The sensor array could recognize pure wheat as well as was able to determine the presence of red flour beetle on it.