Microbial Potentiometric Sensor Monitoring of Milk Fermentation

Microbial Potentiometric Sensors (MPS) utilize endemic biofilms to generate a signal using a measurable potentiometric difference, without the use of cleaning, maintenance, and reagents of conventional sensor monitoring methods. These advantages are suitable for monitoring bioreactions in water distribution systems, soils, and wastewater treatment. In controlled fermentation processes, monitoring seeks to avoid contamination and degradation, which results in loss of productivity. MPS have yet to be applied to monitor the fermentation of milk to yogurt. This study examined the feasibility of using MPS technology to monitor the progress of milk fermentation in real-time with a bench-scale model bioreactor. Signal data obtained by the MPS was analyzed and assessed for the ability to model and predict the time of complete fermentation. Analysis of complete fermentation times in conjunction with pH and MPS signal values found characteristics indicative of complete fermentation. The method detection limit was assessed to inform of the method’s capacity to distinguish complete fermentation time. A sensitivity analysis was conducted to develop a more robust method for predicting complete fermentation time. At this proof-of-concept scale, MPS successfully performed in this capacity to monitor bioreaction conditions continuously. MPS captured information as fermentation progressed, was completed, and as the yogurt product naturally began to decay. Analysis of the data obtained with the technology found predictions of complete fermentation time within a two hour range, with further assessment in the sensitivity analysis narrowing this timeframe to less than 45 minutes. This study revealed the challenges in precisely predicting complete fermentation;however, advancement of a robust analytical method and demonstration of technical feasibility promotes further MPS technology applications that seek to monitor conditions in real-time to preserve health and production.