FTIR–ATR spectroscopy applied to quality control of grape-derived spirits

• A very accurate model was developed for methanol quantification.
• FTIR–ATR with PLS was used for calibration model construction.
• A fast methodology for laboratory quality control was developed.

The Fourier transform infrared (FTIR) spectroscopic method with attenuated total reflectance (ATR) was used for predicting the alcoholic strength, the methanol, acetaldehyde and fusel alcohols content of grape-derived spirits. FTIR–ATR spectrum in the mid-IR region (4000–400 cm−1) was used for the quantitative estimation by applying partial least square (PLS) regression models and the results were correlated with those obtained from reference methods.In the developed method, a cross-validation with 50% of the samples was used for PLS analysis along with a validation test set with 50% of the remaining samples. Good correlation models with a great accuracy were obtained for methanol (r2 = 99.4; RPD = 12.8), alcoholic strength (r2 = 97.2; RPD = 6.0), acetaldehyde (r2 = 98.2; RPD = 7.5) and fusel alcohols (r2 from 97.4 to 94.1; RPD from 6.2 to 4.1).These results corroborate the hypothesis that FTIR–ATR is a useful technique for the quality control of grape-derived spirits, whose practical application may improve the efficiency and quickness of the current laboratory analysis.

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