Real-time fermentation process monitoring is extremely important in process control attaining high quality products in many food industries. Although microwave resonators offer non-contact, high sensitivity, real-time sensing capabilities at extremely low cost with reusable structures, the lack of selectivity even in controlled environments, limit their applications to single variable systems or binary sensing. Since fermentation is a more complex process with at least three variables that could change simultaneously, the traditional microwave sensing techniques fail to measure the volumetric fraction of each of the components. This paper presents a novel technique enabling microwave resonators to perform volumetric fraction analysis of complex dynamically varying liquids while keeping all the interesting aforementioned characteristics for microwave resonator-based sensors. Multiple simulation and experimental results verify the capabilities of the proposed technique in real-time monitoring of ethanol, water, and sugar concentrations during the fermentation process.
