A Piezoelectric Microelectrode Arrays System for Real-Time Monitoring of Bacterial Contamination in Fresh Milk

Abstract

An accurate, rapid, and simple piezoelectric microelectrode array (PMA) system was developed by integrating piezoelectric sensors and microelectrode arrays modified with conducting polymers for real-time monitoring bacterial contamination in fresh milk. The detection was based on the fact that the selected conducting polymer modified on the microelectrode arrays can react with the volatile metabolic biomarkers identified by GC/MS, which results in the conductance change of the polymer, and then the change can be both sensitively and specifically monitored by the PMA system in real time. The frequency shift-time response profiles were auto-recorded by self-developed software. Both the quantitative detection time (QDT) and relative frequency shift response value (ΔF max) were defined as informative parameters to detect bacterial contamination both quantitatively and qualitatively. The QDTs had a linear relationship with the logarithm values of initial concentration of bacteria in the range of 103~106 cfu/ml. The detection limit is 102 cfu/ml. The ΔF max values combined with multilayer perceptron (MLP)-based artificial neural network (ANN) were used to classify the bacterial species. A total of 50 fresh milk samples were identified. Comparative tests were also carried out by using the microbiological method. The identification time of the proposed method (about 2.0~6.5 h) was quicker than that of the microbiological method (more than 48 h). The results showed that the PMA system is accurate, rapid, simple, and economical. It will be potentially used for monitoring bacterial contamination in fresh milk in real time.