Concentrating Table grape juice?

[qaz32152]

My uncle has a big grape vine plant, not sure what variety but it is some kind of Table grape variety. He would like me to try and make wine from the grapes. I know that table grapes do not have enough body/sugar/tannins/etc. I am wondering if it would be worth it to extract the juice and then concentrate it via heat to increase those qualities? I have read that heat/boiling will alter the flavor and may cause clarity issues.

The other idea I had was to use juice concentrate to help assist the fresh table grapes.

 

[Erik the Awful]

My very first wine, about 18 years ago, was a crapshoot of the worst practices. I bleached and thoroughly rinsed a laundry bag and twisted it to crush the grapes and get the juice. I didn't have a carboy, so I used a wide tupperware container. I didn't have an airlock, so I siliconed a copper tube to the lid and put a balloon on it. I used concorde grapes from my back yard, added no water or sugar, used bread yeast, and it turned out a bitter, cloudy mess. I left it at the back of my fridge and forgot about it. Two years later it had settled out and was pretty decent.

I've always had cloudiness if I let the must boil. If I just simmer, it clarifies better.

If you don't have a hydrometer, get one. They're relatively cheap and will clue you in on both how much sugar you have and how sweet your wine will be with the yeast you're using. If you use a yeast that's highly tolerant of alcohol, your wine will likely turn out crazy dry unless you find a way to increase the sugar content. If you use a yeast that makes a lower alcohol content, you might get away with just the grape juice. I highly recommend a carboy and an airlock.

I'm sure someone else has more experience that could give better advice, but I see it's been two weeks without an answer, so I hope this helps.

 

[bernardsmith]

Hi qaz32152 - and welcome. As it happens I am currently experimenting with a batch of store bought table grapes just to see what kind of wine I can get. Truth is that the flavor is indeed, pretty thin. But a couple of thoughts.
1. Cooking will concentrate the sugars (because you boil off the water) BUT cooking helps set the pectins so you are not going to get a bright and clear wine. You are likely to get a very thin jam...
2. An alternative way to remove some water is to freeze the juice and then collect the liquid that you allow to slowly thaw. If you aim to collect about 1/3 of the initial volume you are likely to double the SG and you are likely to have gathered all the sugars and flavors leaving behind (more or less) frozen water).
3. Wine grapes are rich in acids and in tannins but eating grapes are not so you might want to consider adding tartaric acid (the dominant acid found in grapes) and some tannin. Both of these can be found at your local homebrew store.
4. For red wines you want to macerate the grapes with the skins for about two weeks (this I did and was able to create what looks like a rose rather than a deep red wine. For White wines you want to allow the skins to sit with the crushed fruit for about a day at most and then press the grapes and so remove the skins. For both red and white wine you may want a) to add pectic enzymes not only to help remove the pectins but also to help with the extraction of the juice. You might also want to allow some stems to remain with the crushed fruit. The wood contains tannins and some of those tannins are water soluble and so are extracted during maceration.

Last points: You want a wine that will be bottled at around 12% ABV so you want the starting gravity to be around 1.090. Wine grapes when optimally ripe are usually right on target but table grapes may have about half the sugar content so you are likely to want to be adding sugar to the must. You will also want the wine to be somewhat acidic. By that I mean you want to try to get the pH close to about 3.5 This to help prevent volunteer bacteria from gaining a toehold and help (with the correct amount of Kmeta) to prevent oxidation). But a wine's taste is affected less by the strength of the acids in the wine (the pH) and far more by the amount of acids (whether strong or weak) in the wine as measured by TA. This you want to be around 6 g/L (or about .06%). But if the wine tastes bright and zingy your tongue is suggesting that the TA is more or less where you want it. If it tastes too sharp or too blah you may want to tweak the acidity either so that it is lower or higher. But remember TA is not pH and TA and pH can move in opposite directions.