Determination of aroma compounds in grape mash under conditions of tasting by on-line near-infrared spectroscopy

Abstract

The production of high-quality wines requires the use of high-quality grapes. Tasting represents a widespread method for the determination of grape maturity and quality aspects such as the corresponding aroma profile. However, sensory analysis always remains subjective and it is not possible to judge only aroma compounds because the overall impression is also influenced by main components (e.g. sugars and acids). In contrast, the use of near-infrared (NIR) spectroscopy allows the simultaneous determination of various compounds without being affected by personal preferences. In this study, grape mash samples were examined under comparable conditions to those in the mouth. Differences between grape mashes with varying phytosanitary status of the corresponding grapes as well as for different grape varieties were detected. The quantified concentrations of the detected aroma compounds were used to develop calibration models for determination by NIR spectroscopy. Using global calibration models, the single aroma compounds could be determined by NIR spectroscopy with accuracies reaching from R2C = 0.365 to R2C = 0.976. Separate calibration models for cultivation region and grape colour improved the prediction accuracy. Instrumental analysis cannot totally replace sensory evaluation, however, NIR spectroscopy has the potential to be used as an objective, additional method for the evaluation of grape aroma quality.