Abstract
In this study, the suitability of attenuated total reflection (ATR) mid-infrared (MIR) spectroscopy, combined with principal component analysis (PCA) and partial least squares (PLS) regression, was evaluated as a rapid analytical technique for the classification of sparkling wine style and quality. Australian sparkling wines (n = 139) comprising a range of styles (i.e., white, rosé, red, Prosecco and Moscato) were analyzed by ATR-MIR spectroscopy combined with multivariate data analysis. The MIR spectra of 50 sparkling white wines, produced according to four different production methods (i.e., Carbonation, Charmat, Transfer and Methodé Traditionelle) were also evaluated against: (i) quality ratings determined by an expert panel; and (ii) sensory attributes rated by a trained sensory panel. Wine pH, titratable acidity (TA), residual sugar (RS), alcohol and total phenolic content were also determined. The sparkling wine styles were separated on the PCA score plot based on their MIR spectral data; while the sparkling white wines showed separation based on production method, which strongly influenced the style and sensory properties of wine (i.e., the intensity of fruit versus yeast-derived characters). PLS calibrations of 0.73, 0.77, 0.82 and 0.86 were obtained for sweetness, tropical fruit, confectionary and toasty characters (on the palate), respectively.
Highlights
Sparkling wine represents a small but significant proportion (~10%, 37 ML in 2012) of the Australian wine industry’s total production [1]
The attenuated total reflection (ATR)-MIR spectra of commercial sparkling wines showed moderate to strong absorbance peaks at 1045, 1085, 1640 and 3300 cm−1 (Figure 1); with peaks at 3300 and 1640 cm−1 corresponding to the O–H stretching and bending respectively, associated with water [16,17]
A comparison of the minimum and maximum ATR-MIR spectra (Figure 1) obtained from the sparkling wine samples indicated most of the variation observed amongst the samples occurred within the ‘fingerprint’ region; i.e., between 1500 and 900 cm−1
Summary
Sparkling wine represents a small but significant proportion (~10%, 37 ML in 2012) of the Australian wine industry’s total production [1]. The Australian sparkling wine market comprises white and rosé. The individual bottles of sparkling wine are blended in a pressurized tank following secondary fermentation, before being re-bottled; whereas the Methodé. Recent advances in infrared spectroscopic instrumentation, together with the introduction of sampling techniques such as attenuated total reflection (ATR), have made spectral methods increasingly attractive for the rapid analysis of complex matrices across many scientific fields. MIR spectroscopy has increasingly been employed for the rapid, convenient analysis of both juice and wine. This study sought to determine whether or not ATR-MIR spectroscopy can be used as a rapid analytical tool for the classification of Australian sparkling wines, according to style and quality
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