We have been measuring guaiacol and 4-methyl guaiacol levels in quite a few mini-ferment juices (as recommended in our previous blog post) as well as some wines made from the same vineyard blocks. The results do not always correlate.
In many cases we have seen that fermenting vineyard sample results are very low, while those for the finished wines have results that are much higher (above the sensory threshold values for the compounds) with the wines tasting obviously smokey.
It is very important that vineyard samples undergoing a mini-ferment be handled, as far as possible, in the same way the grapes would be handled in the cellar. Especially with respect to skin contact as this is where most of the smoke compounds are found.
Whatever the reason for the differences, we are noticing that they can be quite significant.
For this reason, we strongly recommend that if there is ANY RISK OF SMOKE TAINT in your vineyards, FOLLOW THE AVAILABLE PROTOCOLS to reduce the risk and concentration of smoke taint in your wines.
Note that the aroma threshold for 4-methyl guaiacol is 65µg/L in wine, and for guaiacol different threshold levels have been reported, ranging from 25µg/L (by the AWRI for levels in red wine) to 75-95µg/L from other sources.