In friends Phoebe sings about smelly cat, smelly cat most episodes but have you ever heard of someone singing about smelly wine??
The smell of rotten eggs can really put a consumer off, but this is a naturally made aroma during the fermentation process. If the grapes have produced a low amount of Yeast Assimilable Nitrogen (YAN), the yeast has less compounds to attach and react with. Because the nitrogen is low and not enough for the yeast to attach, they will then attach to sulphides which then release faults and creates hydrogen sulphides. The adding of Di-ammonium phosphate and other additives is added to give the yeast those compounds to attach to and create the delicious aromas that does not leave your nose scrunched up.
Unfortunately, there are times when aromas were not treated and end up in the finished product or produced in the bottle. These sulphur compounds show up either as H2S ( your rotten egg smell), mercaptans (cabbage or garlic) and di-sulphides (cooked cabbage or burnt rubber).
We did fining trials to 3 separate wines with faults. We needed to figure out which wine has H2S, mercaptans and disulphides in it. By using a 1%w/v Copper (II) Sulphate solution in our first wine we could see that it was H2S causing the fault. It was slightly more challenging for the second wine but by adding a 10% w/v Ascorbic acid solution the faults had slightly improved but where still present. This wine had mercaptans and lastly the wine has Disulphides present and the same solution as wine two removed the odour completely.
Very interesting to see what different finning agents will do to different wines. And that if a fault has occurred during the winemaking, we can still remove it without having to dump it down the drain!
By Emma Gordon