Simultaneous determination of alcohol and carbohydrate content in commercial beverages by ultrasound frequency analysis

Controlling the composition of commercial beverages is critical for quality control. Rapid on-line measurements would allow optimization in real time. We have developed a methodology to monitor the volume fraction of ethanol and the carbohydrate concentrations in liquid mixtures using ultrasound frequency analysis. Characteristic distortion to ultrasound waves propagating through liquids is induced by the specific chemical composition of the mixture. The distortion induced by the hydrogen bonding between water, ethanol, and sucrose can be monitored in the frequency domain using 5 MHz wideband ultrasonic transducers. Multilinear regression was used to quantify both ethanol and sucrose over a wide range of concentrations with correlation coefficients (r2) greater than 0.98. Calibrations based on prepared solutions were then used to estimate the ethanol volume and carbohydrate concentration in 22 commercial beverages ranging from sodas to distilled alcohols. Results indicate that the ethanol and carbohydrates could be estimated with a 3.18% and 0.032 g/mL error, respectively. Further, by focusing the analysis over a limited range, the error could be reduced to 0.81% ethanol. This technique demonstrates a strong potential for rapid, in situ monitoring of beverage production, which excludes sample extraction and pretreatment.