Optimisation of the optical path-length for the measurement of volatile compounds in wine using ultraviolet/visible/and near-infrared spectroscopy

Abstract

Analytical methods used for wine analysis, particularly secondary metabolites and volatile compounds, demand expensive instrumentation and require time-consuming extraction processes. Conversely, ultraviolet–visible (UV–Vis), and near-infrared (NIR) spectroscopy, have emerged as valuable analytical tools due to their simplicity, rapid analysis, and non-destructive nature. There is a significant lack of research reporting the optimal path length required for the routine analysis of wine samples. This study evaluated four optimal path lengths (1, 2, 5, and 10 mm) on the UV/Vis/NIR spectra in commercial red and white wine samples. Calibration models were developed for volatile compounds analysed using gas chromatography–mass spectrometry and the UV/Vis/NIR spectra of the samples. The best calibrations were achieved using the spectra of the wine samples collected using 1 mm cuvette, particularly for decanoic acid (r2v = 0.82; RPD = 3.37), ethyl hexanoate (r2v = 0.94; RPD = 3.32), isoamyl acetate (r2v = 0.89; RPD = 4.06), and phenylethyl acetate (r2v = 0.95; RPD = 4.38). The results of this study demonstrated the importance and the effect of the optical path length on UV/Vis/NIR spectra of wine samples for the calibration of volatile compounds, as well as the potential of this technique in predicting these compounds.