Influence of the Scanning Temperature on the Classification of Whisky Samples Analysed by UV-VIS Spectroscopy

Abstract

The definition of the optimal temperature and its effects (either increasing or variations) during analysis of alcoholic beverages are of importance to develop protocols based in spectroscopy. Although several reports have been published on the use of spectroscopy combined with chemometrics to classify and authenticate alcoholic beverages (e.g., wine, tequila, whisky), few reports deal with issues related with the spectra collection (e.g., temperature, path length) and its effect on the classification performances. The objective of this study was to evaluate the effect of increasing temperature on both the UV-VIS spectra of whisky and on the classification results of the samples according to country of origin. Whisky samples from different commercial labels were analysed at different temperatures (25, 35, 45, 55 °C) using a UV-VIS instrument (Agilent, Cary 3500). Principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) models based in cross validation were used to classify whisky samples according to scanning temperature and origin. The results of this study indicated that temperature did not affect the classification of whisky samples according to country of origin. Overall, well defined protocols need to be defined for routine use of these methods in research and by the industry.

Characterisation of single malt Scotch Whisky using low powered ultrasound and UV‐Visible spectroscopy

“…The UV‐Visible spectroscopic analysis of the Scotch Whisky samples showed absorbance in similar regions to the UV spectra of other distilled alcoholic beverages, with the bulk of absorbance occurring between 200‐300 nm. This result is consistent with spectroscopic measurements of Scotch Whisky in the UV‐Visible range ( 48, 49, 77 ) . These peaks correspond to congeners produced during fermentation and maturation such as vanillin.…”

“…Spectrophotometry results were obtained using a double beam Specord 210 Plus spectrophotometer (Analytik Jena AG, Jena, Germany). The variable bandwidth of the instrument was set to measure between 200 and 900 nm in agreement with previous studies ( 48, 49 ) . Samples were diluted by a factor of 10 using Milli‐Q water and compared with reference samples of Milli‐Q water.…”

“…UV‐Visible spectroscopy has been used to detect adulterated syrups ( 46 ) and to determine food colourant concentration ( 47 ) . UV‐Visible spectroscopy does not measure the absorbance of water, ethanol and sugar between the wavelengths of 200 and 600 nm ( 48 ) making it an ideal technique for tracing compounds with conjugated double bonds or aromatic rings in Scotch Whisky. In the alcoholic beverage industry, UV‐Visible spectroscopy has been used to detect fraudulent Scotch Whiskies, to correctly identify commercial Scotch Whisky brands, to monitor colour and to determine the distillery of origin ( 48, 49 ) .…”

“…UV‐Visible spectroscopy does not measure the absorbance of water, ethanol and sugar between the wavelengths of 200 and 600 nm ( 48 ) making it an ideal technique for tracing compounds with conjugated double bonds or aromatic rings in Scotch Whisky. In the alcoholic beverage industry, UV‐Visible spectroscopy has been used to detect fraudulent Scotch Whiskies, to correctly identify commercial Scotch Whisky brands, to monitor colour and to determine the distillery of origin ( 48, 49 ) . A multiple wavelength, portable, handheld UV spectrometer has been developed to monitor ambient aerosols ( 50 ) that could be repurposed for distilleries.…”

A Brief History of Whiskey Adulteration and the Role of Spectroscopy Combined with Chemometrics in the Detection of Modern Whiskey Fraud

“…Similarly, Joshi et al [71], also reported the successful application of UV-Vis combined with chemometrics to classify whisky samples from several geographical regions. The authors reported that PLS-DA models correctly classified 100% of the whisky samples belonging to the USA and Canada and 98% of those belonging to Scotland and Ireland respectively.…”