067: Enhanced Quality Control in Irish Whiskey: Solvent Suppression Nuclear Magnetic Resonance Spectroscopy Coupled With Chemometrics

Introduction

According to the Irish Business and Employers Confederation (IBEC), the value of Irish whiskey exports to the all-island economy surpassed €1 billion (US$1.07bn) in 2022. In Ireland, the number of distilleries has grown from four to forty-two over the past twelve years, resulting in a wider diversity of Irish whiskey products. The whiskey production process generates a wide range of compounds at various stages. Understanding these compounds is vital for grasping the manufacturing process, maintaining quality control, and detecting counterfeit products. Therefore, ensuring that a whiskey product is authentic in the global market is essential to maintaining consumer confidence and sustainable growth of the industry.

Methods

A solvent suppression technique was employed to obtain Irish whiskey's 1D 1H nuclear magnetic resonance (NMR) spectra using a Bruker 400 MHz spectrometer equipped with a standard probe. This approach utilizes three channels to suppress signals from water, ethanol, and ethanol's 13C satellites. Automation streamlines this technique, allowing for rapid analysis of alcoholic beverages. The spectra underwent statistical analysis via Principal Components Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLS-DA).

Results

All 1H NMR spectra share common features across the chemical shift range from approximately 0 to 10 ppm. Although the classification of Irish whiskey samples was performed by PCA and PLS-DA, in principle, the metabolomic fingerprinting and profiling of Irish whiskey samples associated with the chemometric technique provided the most indicative information about the metabolic biomarkers responsible for Irish whiskey differentiation. Using different regions, both the whole spectrum and the higher alcohols, carbohydrate, and aromatic regions yielded similar results and reflected the variability in metabolite profiles for the differentiation of the samples. The analysis effectively modeled several parameters linked to whiskey production, including whiskey style. However, the age parameter could not be modeled to date. Based on the statistically significant discrimination between the various samples, the Variable Importance in Projection scores (VIPs) provide indicative information about the metabolic biomarkers responsible for whiskey differentiation.

Significance

This study illustrates that combining NMR spectroscopy with chemometrics has the potential to identify the congener composition of alcoholic beverages, including Irish whiskey, serving as a tool to combat fraud.

Authors: Chioke A. Okolo, Martin Kitson, David T. Mannion, Kieran N. Kilcawley, Christine O’Connor