Application of sensor technologies for functional control of Kveik yeast in beer production

The results of analysis of the equilibrium gas phase over beer samples prepared using different yeast types at various temperatures are considered. The priority objective of the study is investigating the volatile profile of beverages using new Kveik yeast strains. The importance of selecting the operating conditions for the new strains is associated with their high stress resistance to fermentation temperatures and ethanol levels, which is promising for the production of new beverages. The second objective was optimizing a set of analysis methods to speed up the brewing engineering process. The paper compares the results of beer sample analysis using gas chromatography and instrumental assessment of the volatile fraction using an artificial olfactory system ("MAG-8" piezosensor gas analyzer). Based on the results of the equilibrium gas phase analysis over the beer samples, it was found that the content of odor-forming compounds (mainly alcohols, aldehydes, ketones) depends on the nature of the yeast and the fermentation temperature. This is consistent with the results of gas chromatography and the features of the technology. The developed algorithms for processing data from signals of an array of non-selective sensors made it possible to estimate the relative content of individual classes of compounds, compare samples by odor intensity, and evaluate the effect of temperature and storage time on changes in the composition of volatile compounds in different beer samples. A number of features of changes in the saturation of the drink odor during storage were established depending on the nature of the yeast and the fermentation temperature. Samples obtained at 40 °C with Kveik yeast retain the aroma better than those obtained using standard yeast. Low fermentation temperature (25 °C) does not allow Kveik yeast to fully develop the aroma of the drink; at a temperature of 32 °C, its maximum saturation is achieved. During storage, the composition of the volatile fraction of beer changes the most for these fermentation conditions, and the composition of the volatile fraction of compounds is the most stable for samples obtained using innovative Kveik yeast at 40 °C. Compared with gas chromatography, the technology of artificial olfactory systems does not provide accurate estimates of the content of individual compounds in beer, but it does evaluate the patterns of change in the composition of the volatile fraction. For devices with the "electronic nose" methodology, no additional sample preparation is required, the measurement time is 60 s, the results processed using the author's approaches are clear and easy to compare. With a repeatability of sensor signals of 5%, the level of significant difference in the integral signals of the sensor array was taken to be 15%. A new method of color coding the results of piezoelectric quartz microweighing was used, according to which the samples are divided into groups by color marks, which allows quick comparison of the proximity and difference in the composition of volatile compounds of the samples without detailing the composition.