From grapes to data: rapid must characterization using benchtop NMR spectroscopy

Abstract

Fast and reliable compositional analysis of grape must is essential for process control and quality assurance in winemaking. Fourier-transform infrared (FTIR) spectroscopy is widely used in routine analysis but relies on calibration models and can show reduced accuracy for individual compound quantification in highly variable sample matrices. These limitations are particularly relevant for quality markers associated with grape rot, such as gluconic acid, glycerol and acetic acid, where sensitivity and robustness may be limited. Nuclear magnetic resonance (NMR) spectroscopy enables direct molecular detection and quantification without matrix-dependent calibration. While high-field NMR systems are restricted to specialized laboratories due to cost and infrastructure requirements, recent technological and methodological advances in benchtop NMR have improved performance and robustness, enabling broader application in routine must and wine analysis. In this study, ¹H benchtop NMR spectroscopy was applied for quantitative analysis of relevant must components across a wide compositional range. Must samples from different grape quality levels, including rot-affected material, were analyzed. Optimized measurement protocols combined with an advanced spectral evaluation algorithm [1] were used to enhance signal quality, spectral resolution and quantification reliability. Results were compared with FTIR measurements and validated using established reference methods, including enzymatic and titrimetric analyses. Benchtop NMR enabled simultaneous quantification of multiple compound classes relevant for must quality assessment, including organic acids and selected rot-associated markers. Results showed strong agreement with reference methods and, for selected parameters, improved analytical performance together with robustness against matrix effects and turbidity. Sample preparation was minimal, enabling fast analytical workflows. Limitations occurred at very low analyte concentrations due to signal overlap and baseline variability, highlighting the need for further spectral optimization. Benchtop NMR represents a versatile platform for comprehensive must characterization, enabling rapid, calibration-independent quantification and showing strong potential for routine quality monitoring, including early detection of rot-related deviations. With further validation, benchtop NMR can support data-driven decision-making in grape processing and fermentation management.

References

[1] Matviychuk, Y., Haycock, S., Rutan, T., Holland, D. J. (2021). Anal. Chim. Acta, 1182, 338944.