Decanting Overview


# **A note about decanting** One of the questions we get most frequently is how we decant the wines we serve at our wine workshops. We follow a few evidence-based principles based on findings in the peer reviewed scientific literature. We read those nerdy publications so that you don't have to! Since 2016, we know that wine kept in open vessels (glasses and decanters) will lose 0.9% to 1.9% ethanol over a 2 hour period. This is based on research published in **[The Journal of Agricultural and Food Chemistry](**. The extract reads as follows: _"The relative proportion of water and ethanol present in alcoholic beverages can significantly influence the perception of wine sensory attributes. This study therefore investigated changes in wine ethanol concentration due to evaporation from wine glasses. The ethanol content of commercial wines exposed to ambient conditions while in wine glasses was monitored over time. No change in wine ethanol content was observed where glasses were covered with plastic lids, but where glasses were not covered, evaporation had a significant impact on wine ethanol content, with losses from 0.9 to 1.9% alcohol by volume observed for wines that received direct exposure to airflow for 2 h. Evaporation also resulted in decreases in the concentration of some fermentation volatiles (determined by gas chromatography–mass spectrometry) and a perceptible change in wine aroma. The rate of ethanol loss was strongly influenced by exposure to airflow (i.e., from the laboratory air-conditioning unit), together with certain glass shape and wine parameters; glass headspace in particular. This is the first study to demonstrate the significant potential for ethanol evaporation from wine in wine glasses. Research findings have important implications for the technical evaluation of wine sensory properties; in particular, informal sensory trials and wine show judging, where the use of covers on wine glasses is not standard practice."_ This means that a wine with 15% ABV (alcohol by volume) will turn into a wine with 13.1% - 14.1% ABV after two hours if kept in an open vessel. And if you decant for longer time, the alcohol evaporation continues further as per the chart below. Given this, we decant big, bold red wines for 2-3 hours covering the decanters with clingfilm as shown in the photo below. That way, we block ethanol evaporation and limit the loss of volatile fruity aromas. We normally decant young wines the day before, funnel back into the bottle and place the bottles in the fridge with a vacuum stopper. This gives the oxygen some time to work through through the wine in the event that this is helpful (the jury is still out as discussed below). However, we don't decant Pinot Noir this way. Color in red wines comes from anthocyanins shaped like a ring structure. For Pinot Noir, the anthocyanin groups do not have acyl groups attached. This means that they are prone to rapid oxidation unlike most other red wine varietals. Given this, we don't recommend decanting Pinot Noir the day before and for the same reason we recommend that all Pinot Noir bottles are finished on the same day as they are opened. Regarding the extent to which oxygen can impact red wine (apart from Pinot Noir) there is currently not much evidence in favor of this happening within hours to days. What is absolutely certain is that alcohol can evaporate and volatile aromas can escape be they negative odors (e.g. sulfur off flavors/aromas) or positive (e.g. fruity / floral aromas). This can significantly change the perceived character of the wines. We also know that oxygen plays a key role in long term ageing of wine and can play a beneficial role in polymerization of finely dispersed tannins, eventually leaving sediment in the bottles. But this process does not happen overnight. A good guide to this is micro-oxygenation of red wine as per the table below from the research article available **[here](**. This one published in Critical Reviews in Food Science and Nutrition - another must read journal for the wine nerds out there ;-) The striking thing from this table is that the duration of micro-oxygenation of wine post malolactic fermentation range from 30 days to 124 days. It follows from this that oxygen is unlikely to have much of an effect over just hours to days beyond letting ethanol and volatile aromas escape. This can greatly change the sensory perception of wine but this is due to ethanol and aromas having been removed rather than from the oxygen having had time to alter the wine's tannins and other compounds. Happy decanting!