A source of dimethyl disulfide and dimethyl trisulfide in grain spirit produced with a coffey still

The regulation of dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) concentrations in new-make grain spirit in the Scotch whisky industry are important because these polysulfides are significant flavor congeners. Methional could be a precursor in the pathway of DMDS and DMTS formation; therefore, the relationship between wash methional concentrations at the end of fermentation and DMDS and DMTS in spirit from two stills operating in parallel was investigated. Methional from wash and DMDS and DMTS from spirit were measured by purging them onto Tenax adsorbent and then injecting the volatiles onto a GC column using thermal desorption and cryogenic focusing. Sulfur compounds eluting from the column were quantified using a sulfur-specific Sievers chemiluminescence detector. Methional added as a 'spike' to wash and DMDS and DMTS added as spikes to spirit had recoveries of 104.5, 103.9, and 98.3% respectively. This established the validity of the analytical technique. Concentrations of methional varied in wash from ?50 to 710 µg/L. There was a linear positive correlation between wash methional and DMDS during two periods of distillery production (P < 0.01 for period 1 and P < 0.001 for period 2) investigated. Linear correlations between wash methional and DMTS were also found during period 2 (P < 0.001); however, correlations were only significant during period 1 (P < 0.1, still 1 and P < 0.05, still 2) In conclusion, DMDS and DMTS concentrations in new-make spirit are related to the concentration of methional in wash, although operation of stills can in particular modulate the final DMTS concentrations.