Real-time monitoring of kefir-facilitated milk fermentation using microbial potentiometric sensors

Considering that fermentation is a microorganism-mediated redox process, an underlying hypothesis was postulated that the microbial potentiometric sensor technology could be used to monitor dairy fermentation or other similar food production processes. It was also hypothesized that the signal characteristics could be exploited to correlate the mass of inoculum and the fermentation completion time. Three objectives were addressed to test these hypotheses. First, a set of fermentation experiments were employed to measure the changes in the open-circuit potential signals from two carbon-based microbial potentiometric sensor (MPS) electrodes exposed to varying kefir inoculum to milk ratios. Second, the MPS signal patterns were analyzed to determine what signals were indicative of completion of the fermentation process. Third, regression analyses were conducted to determine the level of correlation between the fermentation completion time and the mass of the inoculum under constant conditions. The hypothesized capabilities of this technology for monitoring kefir fermentation processes of milk were validated. The MPS technology could be used to monitor kefir fermentation in real-time with high reproducibility. The regression analysis approach was able to discern a correlation between the fermentation completion time and the mass of kefir inoculum characterized with coefficients of determination R² > 0.94. Furthermore, the results from the MPS signal patterns offered unique perspectives at various phases of the fermentation process, which open new avenues to better understand fermentation. This study demonstrates that, when coupled with appropriate signal analysis tools and methodologies, the MPS technology offers unparalleled opportunities for real-time monitoring, optimization, and management of industrial-scale fermentation and other food or beverage production processes which are facilitated by microbial activity.