Gas-Liquid Chromatographic Determination of Monosaccharides and Glycerol in Aged Distilled Spirits

Abstract

Gas-liquid chromatography was utilized for the analysis of monosaccharides and glycerol in distilled spirits aged in new, charred white oak cooperage. Arabinose, xylose, fructose, glucose, galactose, and rhamnose were identified. Traces of fucose and mannose were indicated. Total concentration of sugars increased from 16 to 37 g/100 L at 100° proof and glycerol from 0.83 to 2.42 g/100 L at 100° proof during aging from 1 through 12 years. Compounds were identified by a comparison of GLC chromatograms of trimethylsilyl (TMS) ether derivatives, alditol acetates and trifluoroacetates, and TMS-aldono-l,4-lactones. Sugars and glycerol were quantitated as TMS ether derivatives with 3 % JXR organic phase on Gas-Chrom Q with an accuracy assessed at ±2—3%.

Liberation of recalcitrant cell wall sugars from oak barrels into bourbon whiskey during aging

“…In Fig. 5 we show that overall, hemicellulose was degraded during the maturation process, and a more complex pattern of deterioration emerged from whiskey maturation, rather than a simple loss over time that was expected from previous work on carbohydrate accumulation in bourbon whiskey 17 , 24 . Hemicellulose decreased during aging, to an extent that was significant in the ten-year-old barrel C layer when compared to the new C layer.…”

“…4B(ii) ) , we found that the quantity of glucose building blocks that could be released from an oak cask into the whiskey held within is equivalent to 300 g from the C layer alone. This amount would result in 1.3 g/L of glucose for a standard sized barrel - a greater amount than estimated in previous indirect studies 17 , 24 . This difference may be explained by the acidification of whiskey that occurs during maturation 17 .…”

“…The numerical variation may indicate an underlying complexity to hemicellulose hydrolysis during whiskey maturation. We believe it is no coincidence that one of the major carbohydrates found in bourbon whiskey, xylose, is also the monosaccharide that is present in the largest amount in the hemicellulose of oak heartwood 17 , 24 , 25 . We therefore quantified both xylose and glucose, the other major carbohydrate found in bourbon whiskey.…”