Development of the hot-wire viscosity sensor and its application to food and fermentation processes

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Hot-wire viscosity sensor, characterized by its simple structure with no moving part, is a viscosity sensor which analyzes the natural-convection heat-transfer coefficient from the hot-wire to measure the viscosity of the test fluid. The principle in the operation of the hot-wire viscosity sensor was analyzed theoretically through the stagnant-layr theory around the hot-wire.The hot-wire viscosity sensor was applicable only to the stagnant system because it cannot distinguish the effect of natural convection from that of forced convection in the heat-transfer process. Thererfore, a shielded hot-wire viscosity sensor was developed for the application of the hot-wire sensor to the flowing system. The shielded hot-wire viscosity sensor, compatible with the high pressure sterilization, was proved to be effective as an on-line sensor for the fermentation monitoring sensor in the xanthan fermentation by Xanthomonas campestris and the tobacco cell (Nicotina tabacum L.cv.BY-2) culture process, reflecting the change in the viscosity of the culture fluid because of the change in concentrations of metabolites and cell density. The hot-wire viscosity, shielded or nonshielded, proved to have a very wide coverage in the viscosity ranging from 1 to 2-3000mPa・s with a single sensor element.