Advanced Solvent Signal Suppression for the Acquisition of 1D and 2D NMR Spectra of Scotch Whisky

Will Kew,Nicholle G.A Bell,Dušan Uhrín,Ian Goodall

doi:10.1002/mrc.4628

Abstract

Scotch Whisky is a culturally significant high value commodity. To gain a better understanding of the production processes and whisky maturation chemistry as well as addressing authenticity concerns, advances in chemical analysis of whisky are required. NMR spectroscopy represents a means to detect, identify, and quantify all major components of whisky by a single technique. It is an untargeted technique allowing for simultaneous profiling of different compound classes, albeit with a limited dynamic range and sensitivity. In common with other alcoholic beverages, whisky primarily comprises of two protonated compounds – water and ethanol. Their signals dominate the standard 1H spectra of spirits and need to be suppressed to allow observation of important lower-abundance congeners. We have presented a simple and robust solvent suppression technique that enables acquisition of high quality NMR spectra of alcoholic beverages on cryoprobe instruments and applied it to acquire 1D and 2D NMR spectra of Scotch Whisky.

Highlights

Scotch Whisky is a culturally significant and high value commodity
We present an automated ethanol/water solvent suppression methodology allowing for the acquisition of high resolution, high sensitivity 1D 1H NMR spectra of whisky with minimal sample preparation
Scotch Whisky is an acidic solution, with acidity increasing during maturation

Summary

Introduction

Scotch Whisky is a culturally significant and high value commodity. Chemical analysis of ScotchWhisky is essential to gain a better understanding of the production processes and maturation chemistry [1,2] as well as for addressing food safety challenges,[3,4,5] and authenticity concerns.[6,7,8,9,10,11] Scotch Whisky is produced by the fermentation of a cereal source, distillation to below94.8% (v/v) ethanol, and maturation in oak casks in Scotland for a minimum of three years.[12]. Scotch Whisky is a culturally significant and high value commodity. Whisky is essential to gain a better understanding of the production processes and maturation chemistry [1,2] as well as for addressing food safety challenges,[3,4,5] and authenticity concerns.[6,7,8,9,10,11] Scotch Whisky is produced by the fermentation of a cereal source, distillation to below. 94.8% (v/v) ethanol, and maturation in oak casks in Scotland for a minimum of three years.[12] Its production follows strict guidelines outlined in the Scotch Whisky Regulations (2009)[13], and yet every distillery produces a unique spirit. Chemical analysis of whisky has used standard MS techniques, in particular GC- and LCMS, to identify and quantify its compounds, referred to as congeners.[12,14] These methods are labour intensive to establish, often compound specific, and require several instruments and skilled operators to prepare the samples and interpret the results

Methods

Results

Conclusion