Design and experiment of electrochemical device for quickly predicting remaining shelf life on fresh pork

Abstract: Fresh pork is popular due to its nutrient and good taste, and also one of the most important meat consumed. As the remaining shelf life is short, it is important for producers and retailers to evaluate the freshness and remaining shelf life of fresh pork under the storage temperature. Rapid detection on bacteria of fresh pork is required urgently. The rapid and accurate electrochemical detection are getting more and more concern. The purpose of this paper was to design and develop the device for predicting the remaining shelf life of fresh pork, which was combined with the prediction model of microbial growth and based on the electron transfer of microbial respiration and the principles of primary battery. And the signal acquisition and data analysis software of the device was developed with LabVIEW programming language. The dynamic growth model of total aerobic count was established and verified. The results indicated that the modified Gompertz model could well describe the growth of total aerobic count in fresh pork, and the coefficient of determination was 0.9954.The regression of Belehradek model finely described the effect of temperature on the maximum specific growth rate and the lag phase. The validation of the built model was carried out by comparing the actual and predicted growth curves of total aerobic count in fresh pork at 10 and 22 ℃, respectively. By calculating bias factor and accuracy factor, we found that the established model had high reliability and could predict the growth of total aerobic count in fresh pork in the range of temperature from 4 to 30 ℃ effectively. The electrode was constructed from platinum anode and cathode, and a proton exchange membrane filter was used for retaining the microbes and balancing the charge. The procedure of electrochemical signal from total aerobic count in fresh pork included 3 parts. Electron generated from oxidation of substrate was transmitted to the extracellular space by cytochrome C on cell membrane, then the electrochemical signal was amplified by electron shuttles from the exogenous, and finally it was delivered to Pt electrode. Samples containing microbes were attached to the surface of a platinum anode. The electrode was immersed in phosphate buffer solution (50 mmol/L, pH value of 7.0) containing a redox dye (2,4-dichlorophenolindophenol), and the voltage generated was measured. The software combined with the established growth model of total aerobic count was developed by LabVIEW for predicting the remaining shelf life of fresh pork. The response time of the electrochemical device was 20 min, and the voltage generated was proportional to total aerobic count above 104 CFU/g. The accuracy factor of predicting the remaining shelf life of fresh pork was between 1.02 and 1.06. The accuracy factor at 10 and 22 ℃ was 1.04 and 1.03, respectively. But the sensitivity and accuracy of the predicted remaining shelf life between 104 and 105 CFU/g needed further improvement. As this study only focuses on one part of pork, to achieve an accurate prediction of any part of fresh pork sample, the parameters of device and the prediction models should be adjusted with more varieties of fresh pork portion.