Question for the Winemakers/Biochemists

My poor description is probably going to make identification of what I am looking for impossible, but I'll give it a try anyawy.

There is an aroma present in some homemade wines, and sadly also in a few commercial wines. It is something that I describe as a 'raw' note that is foreign to well made wine and jumps out at you once you have experienced it.

The minute I smell it I know there is something amiss (many people pass over it, not being sansitive or familiar with it). It isn't something that cuases you to recoil, but I view it like I would a slight secondary fermentation - something that normally would not be happening.

I wish I could describe it better but I am taking a shot in case there are other people that will know what I am referring to - and hopefully one who has winemaking experience and can identify the sort of compound that causes this and perhaps what step in winemaking cuses it to occur.


Anyone have any ideas?

[Jenise]

Are you specifically talking about homemade wines from actual grapes and ruling out concentrates? I presume so, but since you're in Canada where there seems to be a home-winemaking-kit store on every block, I had to ask.

Are you specifically talking about homemade wines from actual grapes and ruling out concehntrates? Since you're in Canada where there seems to be a home-winemaking-kit store on every block, I had to ask.

Doesn't seem to make much difference whether it is a wine made from concentrate or grapes. The wine I noted this aroma in was a Joie (BC) white - uled ot at an Alsatian event yo mayhae attended in a pathetic attempt a ringer

My note:

2005 Joie “A Noble Blend” – a BC wine, present with prior approval of the organiser, made from various German and Alsatian varietals. Very light colour and I spotted it right off the bat as a BC wine because it had that identifiable amateur wine making sort of raw note in the nose. OK on palate I suppose, but light and forgettable. This one won’t be making the Alsatians lose any sleep.

I said it was BC wne because it has been years since I noted that same smell from any decent commercial wine.

You're right - it's hard to figure out exactly what you're describing, but there are at least a few things that can easily go wrong, especially for home winemakers. Too much time in contact with either the skins or lees can affect the flavor, especially in whites. Prompt racking is essential. Marginal fruit - the presense of mold. Failure to provide proper nutrients to the yeast can produce H2S, which can lead to mercaptans. The failure to maintain a proper SO2 level can encourage bacterial spoilage and the developement of vinegar. Small amounts of vinegar may not be perceptible on its own, but would overall be detrimental to the aroma and flavor. However, probably the most frequent error made by home winemakers is exposure to air - not keeping vessels (carboys, barrels, etc.) filled will lead to a rapid decline in the quality of the wine.

To add to Howie's list, producing wine too quickly, maybe skipping some of the racking necessary, and then bottling it too soon, leaves a kind of rawness.

Bill,
Maybe just youth. My whites take a minimum of about 10 months from end-of-fermentation to start "coming around." Reds take longer, though exactly how long depends on a number of issues. Home winemakers sometimes rush things a bit, and I suspect some commercial winemakers too.
Best