Use of electronic nose, validated by GC–MS, to establish the optimum off-vine dehydration time of wine grapes

Pedro Ximénez grapes were sun dried for 0, 2, 4, 6 and 9 days and the resulting must was analysed by gas chromatography and by an electronic nose. In the last stages of the process compounds related with ripe fruity and toasty aromas decreased whereas the concentration of sugars increases slightly, which suggests that the optimum dehydration time is reached before the ninth day. A discriminant analysis of data by the electronic nose allows for the differentiation of the must from dried grapes. Multiple regression analysis was made with the aim of relating the aroma that best described the must from dried grapes with the data reported by the electronic nose, obtaining a correlation above 99%. Therefore, according to the obtained results the electronic nose can be used as a tool for quick analysis that can help winemakers to decide the optimum drying time, taking into account the concentration of volatile compounds.