Automatic sensor system for the continuous analysis of the evolution of wine

An in situ and on-line electronic nose (e-nose) was developed and installed in a winery for the continuous measurement of wine evolution. The system has a novel sampling method that uses a carrier gas to extract aroma compounds directly from the headspace of the wine storage tank, and the volatile compounds are then automatically carried to the sensor cell. The system uses a tin oxide multisensor prepared by radio frequency sputtering onto an alumina substrate and treated with with chromium and indium. The whole system is fully automated and controlled by a computer and can be supervised remotely via the internet. Linear techniques such as principal component analysis and nonlinear ones such as artificial neural networks were used for pattern recognition, and partial least squares analysis was used for predicting GC-MS analysis. Results of two different wines show that the e-nose system can detect the evolution of aroma compounds for nine months. Correlation coefficients near to 1 were obtained in the prediction of the volatile organic compounds ethyl butyrate, isobutyric acid, isobutyl acetate, hexyl acetate, and ethyl octanoate. This system can be trained for monitoring wine preservation and evolution, detecting off-odors, and warning the wine expert to correct problems as soon as possible in order to prevent spoilage and improve wine quality.