Tannin levels vary between grape varieties. There is little tannin in white wine as skin contact isn't long. Oak contact can add tannin IIRC. What variety of grapes did you get?
Charles, thanks for your reply. I understand the tannin thing when it comes to the different varietals and how skin contact effects the ammount. But my question is how can I determine the amount of tannin present in a purchased juice and how and what can be used to increase it when it is low?
Andy
I don't know of a test for tannins in the way we test ph or acid, but instead use your sense of taste. I'm sure you've had tannic wines from commercial wineries. Tannins produce an astringent kind of effect on taste, similar to the way strong tea kind of puckers the mouth. Tannins also contribute to the "dry" taste sensation.
Most wine supply stores sell powdered grape tannin. Off the top of my head, I think a small amount (1/2 tsp maybe?) is needed to adjust the wine, the label will have the correct information. I'm still curious as to what variety of juice you bought since it might be a low tannin grape variety. HTH
Cabernet, Cab-Franc, Zinfandel, Chambourcin, Chardonnay
FWIW, Tim Vandergrift of Brew King cautions against using the generally available grape tannins in grape wine (at least kits) because he feels that the added tannin is more likely to bind to other compounds in the wine (colour and flavour compounds) and fall out of suspension taking the other things with it. He says there are relatively new products available that don't do this, but are not commonly available and are prohibitively expensive.
I believe you can get more tannin from the skins by adding pectic enzyme before fermentation. This may also extract other phenolics that you don't want. But most cautionary notes I've seen about its use is that it may extract too much tannin (people generally want to use it to extract more color and flavour, not tannins). I used some last year on my central california valley CabSauv and Valdepena (Tempranillo) because the grapes didn't seem very tannic to me, and the results were excellent -- though I have no way of knowing what it would've been like without the pectinase, since I haven't done similar varieties before. But of course this won't help with juice because you have no skins :-) BTW, I believe pectic enzyme is one of the main tools that the red juice producers use to extract color, flavour and tannins from the skins.
If you're sticking with the juice, your best bet is to simply explain your perceived results and your preferences to your supplier, who should be able to make the best recommendation to fit your tastes.
I would also caution you to have patience and let your wine mature more. I have several types of kit wines that are up to 2.5 years old now, and the flavour profiles have changed very noticeably over time
-- including the impression that both the overall flavour level and the tannin level seeming to drop and then come back. My expectation was that the wine would simply get more and more smooth over time, but I've definitely perceived that the flavours and tannin levels seemed to start increasing again during the second year of aging. Perhaps there isn't actually more tannin, but simply that the improved flavour causes me to savour the wine more, keeping it in my mouth longer, and thereby giving me a *perceived* increase in astringency...
Cheers, Richard
Andy, there is no a practical way for home winemakers to measure the amount of tannin in grape juice, nor is there a practical way of adding tannin to a juice .
Red wines are more complicated and the difference between red and white wines is much more than just the red color. "Tannin" in grapes is not just one single material. It consist of many different materials including both hydrolyzable tannins and condensed tannins. There are lots of important materials in the skins and seeds, and the materials that comes out of the seeds and skins during fermentation are some of the most critical components of good red wine. Fermenting the solids together with the juice is very important, and this is why making first class red wines from juice is practically impossible. (See Margalit, "Concepts in Wine Chemistry," page
105).lum
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