FTIR analysis of ash in wine

Abstract

In a modern oenological laboratory determination of ash is a limiting factor regarding the speed of analysis, since functional FTIR analysis of ash are not common yet. Therefore 324 samples were analysed by FTIR spectroscopy on TDI Bacchus 3 as well as ISO 17025 accredited reference method (OIV–MA–AS2–04: R2009) in two duplicates. FTIR spectra and reference data were uploaded into software for the calibration development and validation performed. Already the original TDI calibration was ready to use, showing satisfying results. However, we tried to improve it. On 324 spectra, we have looked for optimal wavelengths and mathematical models, which gave the best results. The developed calibration was then confirmed by method validation: repeatability, reproducibility and accuracy. The expanded measurement uncertainty calculated was 0.3 g/L, which I slightly higher than of the reference method used. We have found another advantage over classical method: there is no influence of the air pressure or moisture. Nevertheless, we were able to confirm that our reference method was free of systematic error induced by the influence of the weather. Anyway, we can conclude that analysis of ash in wine by FTIR spectroscopy is a promising, fast and reliable new method.