Technology - History of the FluorLite-LX Sensor Development

The development of the FluorLite-LX fluorescent sensor technology for measuring protein concentration in whey permeate began in July 2012 in the lab of Professor Fred Payne at the University of Kentucky. The goal was to develop a fluorescent sensor technology that would measure the true protein content of whey permeate based on fluorescence of the amino acid tryptophan. The development effort with a bench scale laboratory setup which showed that protein fluorescence at very low concentrations using an ultraviolet LED could be detected.  After these initial tests, a small sensor device was developed and tests conducted to determine the fluorescent response to variations in product pH, temperature, whey solids, and protein concentrations.  Because the UVLED had a short lifetime, microprocessor control was added to pulse the UVLED. These initial results suggested that a commercial sensor was technically feasible.

The next step was to design and manufacture a sensor for a plant test. The design of the optics and microprocessor control of a prototype sensor began in February 2014. The first prototype fluorescence sensor as shown in Figure 1was installed at a dairy plant in Wisconsin in May 2015.  The sensor was tested on several whey permeate solutions with samples taken for “true” protein analysis.  The results showed that protein in the whey permeate could be detected at very low concentrations; the sensor performed as designed; a calibration algorithm relating fluorescence to “true” protein was needed; and the fluorescent measurement decreased with whey permeate solids content.

Development of a second prototype fluorescent sensor for plant testing proceeded was initiated in June 2015.  The optics were refined and a microprocessor with additional programming capacity added. The second prototype fluorescent sensor, named FluorLite-P and shown in Figure 2, was installed at a Wisconsin dairy plant in April 2016 and operated successfully. Data analysis and optimizations continued for nearly two years at this plant as well as at two other U. S. dairy plants.

The experience gained from the three plant tests between 2016 and 2019 gave a very strong indication that the sensor needed to correct for the solids content of the whey permeate to be a viable commercial product.  Solids varied between 1 and 8% and it became obvious that it was inefficient to calibrate each sensor for different solids contents. In January 2020, it was concluded that it was essential that the sensor needed to automatically correct for the solids content in whey permeate.

In February 2020 laboratory testing of several different optical technologies for correcting for solids content began. A concept that used fluorescent light extinction appeared very promising and could be easily adapted within the existing sensor design. The testing of the light extinction concept continued with intensity, focus, and few distractions. A prototype of the new measurement technique was quickly assembled using existing parts and delivered for plant testing in August 2020. The prototype FluorLite-LX sensor, with the LX standing for light extinction, worked extremely well.  It measured true protein between the ranges of 0.01 and 0.35% protein and simultaneously corrected for the solids content of the whey permeate.

This successful plant test initiated the optimization of the optics and electronics for a commercial unit. In February 2021, a second prototype light extinction sensor was delivered to the cheese plant to verify the optimized optics, calibration technique, and algorithm. It performed as designed. As of June 2021, both sensors are still operating successfully and the plant plans to add between 2 and 5 more when the commercial design becomes available in mid-2021. Figure 3 shows a sketch of the new FluorLite-LX sensor that will be available mid-2021.

Many different technologies and technical developments were required to develop the FluorLite-LX sensor. Three development efforts were particularly difficult: obtaining a UVLED that met the required design requirements; development of a thin sapphire optical window that withstands process pressure; and development of a calibration algorithm that translates fluorescent measurements into “true” whey protein content corrected for solids.  The result of the long development is a simple stand-alone fluorescence sensor that measures “true” protein content in whey permeate corrected for solids and operated by the plant PLC system. The goal established in the summer of 2012 was met after 9 years of development effort. This sensor technology is expected to find a significant market in monitoring the performance of whey filtration systems as well as evolve and find other measurement applications.

History of the FluorLite-LX Sensor Development

Written by Fred Payne, President of Reflectronics, Inc.

Last updated May 25, 2021