Development of a Fiber Optic Refractometer to Measure the Partial Hydrogenation of Edible Oils.

A fiber optic refractometer has been developed to measure the refractive index of edible oils. This prototype refractometer, intended for on-line measurements, operates in the presence of particles suspended in the oils as part of the hydrogenation process. Sensing elements of the refractometer are: (1) an optical fiber whose fused silica core is exposed to the flow of edible oil, and (2) precision temperature detectors immersed in the oil. The principle of operation involves modulating the oil temperature until the monochromatic light transmitted through the fiber reaches a minimum. An algorithm is developed correlating the temperature measured at this light transmission minimum to the oil refractive index as referenced to sodium D light and 50.0 ^circC. A dispersion constant and a refractive index vs temperature constant for the oil are determined using the fiber optic refractometer as a measuring device. Results, obtained using actual edible oil process samples, correlate to within 0.0001 RI units when compared to measurements taken with an Abbe refractometer.