Grapevine issue

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Grapevine issue

Postby tonyhibbett » Tue Sep 27, 2016 18:40

My neighbours share a very large chardonnay grapevine on a pergola, which is impracticable to protect with netting. I've been scaring the wood pigeons off with a cap gun, but blackbirds just ignore it. I tested juice from a sample bunch of grapes and found the sugar content 15%, which is fairly good, but the acidity is 8.5 ppt (tartaric), pH 2.9, which is way too high. I have belatedly started mid season pruning, which should concentrate energy into ripening the grapes further, but the growing season is on the wane.
A simple way to reduce acidity is to dilute the juice with water and add extra sugar. This is of course sacrilege to the purist grape winemaker but wine kit makers do it as a matter of course, 50% dilution being the norm.
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Re: Grapevine issue

Postby tonyhibbett » Thu Sep 29, 2016 13:47

As the pigeons have got wise to the cap gun, I decided to start picking the grapes. So far 10 kilos (birds had about 1 kilo). After crushing and pressing twice I got little more than 5 litres of juice at sg 1060, requiring 500 g of sugar to get 1090. I put the 4 kilos of skins, pips and stalks in a bucket with 2.5 litres of warm water and some pectic enzyme to soak for 24 hours before pressing again. This will extract up to 1 litre more of juice while the water dilutes the acid. With added sugar, this weak must will be added to the main brew, boosting it to about 8 litres.
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Re: Grapevine issue

Postby Rolfster » Fri Sep 30, 2016 09:52

Have you considered getting a hawk?
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Re: Grapevine issue

Postby tonyhibbett » Sat Oct 01, 2016 11:25

Tried a dummy hawk which worked for a while. It's not a serious problem. There are only 3 wood pigeons and 2 blackbirds. I have calculated that I lost a kilo of grapes and the total harvest was 13 kilos.
I have solved the problem of excess acidity. Using the soaking method, I extracted an extra 3 litres of juice. With the water and extra sugar, the must ended up 15 litres at pH 3.1. Rather than dilute further than 20%, I added 7 g of precipitated chalk to the 15 litres, giving pH 3.3, just under 6 ppt, which is fine.
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Re: Grapevine issue

Postby tonyhibbett » Wed Oct 05, 2016 10:25

I have a Wrotham pinot (meunier) vine which doesn't make a good red wine. The variety is used with chardonnay (50%) and pinot noir (25%) to make most champagnes. The yield was low (3.5 kilos) this year, but this sugar level (16%) is quite good. After crushing and pressing, I got 2 litres and added it to the brew. When making white wine from black grapes, the skins are not fermented. However to extract more juice, I soaked them overnight with 1 litre of water and got another 500 ml of juice which was slightly pink. When added to the main brew, a pink tinge remained. Ideally I need 18.5 litres to fill one of my casks, so I topped up with 3 litres of apple juice, bringing the total to 20.5 litres, which will end up as 19 litres after fermentation, racking and fining, leaving 500 ml for topping up. The yellow apple juice turned the light pink to light orange. Another 7 g of chalk was added to adjust the pH back to 3.2. The fine pulp was skimmed from the surface and oak chips added.
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Re: Grapevine issue

Postby tonyhibbett » Mon Oct 10, 2016 13:04

I had neglected to recalibrate my pH meter and found it to read 6.7 instead of 7.0. 0.3 may not seem much but the difference between 2.9 and 3.2 certainly is. So after racking the actual pH was 3.7. However titration gave 6.25 ppt tartaric, really the upper limit for a dry white wine, which my taste buds confirmed.
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Re: Grapevine issue

Postby tonyhibbett » Tue Oct 11, 2016 11:32

Fining didn't completely clear the wine but that's ok because wine improves in cask when sitting on a small amount of yeast. the cask was long winded. I bottled the last few litres in a polypin and filled it with the wine in the cask. This required topping up with the wine previously bottled. Having rinsed the cask, I filled it with the new batch. This frees up the fermenting bin for the next batch, but sadly there are no grapes left to harvest!
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Re: Grapevine issue

Postby tonyhibbett » Mon Oct 24, 2016 13:46

After 2 weeks, I sampled the wine which has turned into pink fizz, on account of the cask previously holding red wine and a malolactic fermentation taking place.
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