SPR, TRANSMITTANCE AND LIGHT SCATTERING SENSORS APPLICATION TO MONITORING OF BEER FERMENTATION PROCESSES

Beer is an alcoholic beverage obtained by the fermentation of barley by the action of yeast as the Saccharomyces cerevisiae, with the addition of hops. The yield guarantee and quality of beer is monitored during fermentation by laboratory analysis such as quantification of yeast cells, wort density and alcohol content, among others. These activities require qualified personnel and specialized equipment, as well as the need for sample collection. Thus, continuous monitoring of the process with the use of electronic sensors could reduce the analysis time and consequently reducing time for corrective actions, risk of contamination during collection and also allowing remote monitoring. The objective of this work is the development of a low-cost, single-probe sensor for the monitoring of fermentation process in handmade Pilsner beer utilizing three different principles of operation simultaneously: Surface Plasmonic Resonance (SPR) through U-shaped probes coated with 70 nm gold thin film, transmittance, and light scattering sensors. The sensors responses are read by a microcontroller optoelectronic interface. The probes sensitivities were measured in ethanol obtaining to 2 V/RIU for the SPR sensor, 2 V/RIU for transmittance sensor, and 18 V/RIU for the light-scattering sensor. For measurements of gradual ethanol addition in commercial Pilsner, Lager and 0,0% Pilsner beers, the probe sensibility was around 7 V/RIU. Although a calibration process should be performed for each type of beer, Pilsner fermentation was monitored by the proposed sensor and it was possible to determine different fermentation phases: the adaptation, growth and stationary phases. The sensor system shows promising results for monitoring the fermentative progress of beer.