Study of hop aroma components using chemical sensors

Abstract

An array of sensors was selected taking into account the specific component composition of the essential oil contained in the hop plant. The aroma intensity of several hop varieties was investigated using high-frequency piezoelectric resonators with a high sensitivity and low detection limits for volatile components. Analytical signals of the sensor array in the vapour of the equilibrium gas phase of the samples were assembled into a multidimensional data set, presented in the form of a “visual imprint” (diagrams were plotted according to the maximum responses of the sensors in the equilibrium gas phase of the samples during a time interval of 60 s). Data for the samples with acceptable organoleptic characteristics complying with regulatory documents were taken as the standard. For the samples under study, the responses of chemical sensors in the equilibrium gas phase were presented in the form of a total signal and compared with the “visual imprint” of the maxima for the standard; the areas of indentation figures were calculated – S_Σ, G_c.s.. As additional characteristics, 5 identification parameters A_ij were used, calculated from the signals of individual sensors in the gas phase of the analyzed samples and selected standards. The identity between the composition of the sample under analysis and the corresponding standard was established, when the relative difference in the parameters of the "visual imprint" figures did not exceed 20%. Conversely, a sample was considered not identical to the selected standard, when the relative difference was higher than 20%. The experimental results were used to establish the identity or authenticity of hop pellet samples from different batches.