Water based-ionic liquid carbon dioxide sensor for applications in the food industry

Abstract

A new water-based sensor for carbon dioxide containing an ionic liquid is presented. The sensor is based on the acidity of the CO2 molecule. The sensor incorporates an ionic liquid in the matrix, which enhances CO2 solubility, and minimising the response and recovery times of the sensor. The entire concentration range (0–100%) of CO2 has been studied. The sensor is more sensitive at low CO2 concentrations as is usual in this kind of optical sensor. As the sensor is intended for smart food packaging, one of the most important characteristics is stability, and this has been studied under different conditions of light, temperature and relative humidity. The sensor was found to be stablef or more than 14 days, which is the period of use for the intended application.

Pork chops were packed at 4 °C and the production of CO2 studied in conjunction with total bacterial counts over a period of 14 days. The results show that the concentration of CO2 dioxide increases in time, in correlation with bacterial counts. As the threshold of CO2 content for human consumption of this meat is 20%, the sensor has been optimised for detection around this concentration.