Winegrowers Supplies - Making Red Wine - from concentrated grape juice
1) Diluting the concentrated juice:
For red wine I suggest aiming for:-
12.5% alcohol = 91 °Oeschle juice (specific gravity 1.091) = 21.7 Brix
The concentrate may not be exactly 65 Brix, it could be up to 68% Brix, so:-
Pump good-tasting fresh water into the tank until it is 60% full. For concentrate at 65 Brix, 2 parts water to 1 part concentrate would give 21.67 Brix.
Start the tank-rouser running.
Use a Fork Lift Truck, with a rotary drum fitting, to lift a drum above an
open top variable-capacity tank
and slowly tip the concentrated grape juice into the water. Add more
drums until the tank is about 90% full, empty the drums completely.
Note: finally there will need to be at least a 50mm air space at the top of the tank, between the juice surface and the lid, to accomodate the fermentation foam. This is about 2% of the tank volume.
Measure the specific gravity (°Oechsle) of the diluted juice, with a refractometer.
Record the volume of diluted juice in the tank.
Calculate how much more water needs to be added to reduce the specific gravity to the intended 91 °Oe. Add this amount of water and re-measure and adjust until correct.
Take a sample of the diluted juice and measure the level of total SO2.
Add wine sulphur to raise the total SO2 to 20 mgm/litre.
Switch the rouser off but leave it in the tank.
2) Preparing the juice for fermentation:
a) Prepare bentonite; 1 gram per litre, for removing any excess protein.
b) Measure the acidity of the juice with a test such as the Sulfacor.
Calculate the amount of citric acid to adjust the acidity to 6.0 g/l.
Turn the rouser on again and add the acid crystals to the top of the tank, so that they are dissolved in the juice.
c) Add the bentonite suspension, after draining off excess water, and rouse in.
d) Add yeast nutrients (should be added before the addition of the yeast) and rouse in.
e) Rehydrate the selected yeast (Oenoferm Rouge);
Add to the must, rouse in, then switch off the rouser and remove it from the tank.
American-oak toasted-chips should be put in the tank at this stage, use about 2 grams per litre. The
chips should be in infusion bags, or muslin sheet tied to form a sack, with a stainless steel
weight to hold them below the surface, and secured
with a long nylon cord, so they can be pulled out easily from the top of the variable-capacity tank.
Before fermentation is the best time to add this, it can be left in afterwards to give extra complexity to the wine.
f) With the cooling plates fitted to the lid, lower it into the tank so that it is about 50 mm above the surface of the juice. Pump up the sealing tube to 0.5 bar so that the lid is supported.
Leave the juice to ferment. Monitor the temperature regularly, it should be at least 15 °C initially. When the fermentation starts and the temperature rises, run cooling liquid through the cooling plates, adjust the speed of flow to keep the temperature at about 16 °C.
The cooling liquid can be cold water. For a more efficient method then a closed circuit system using a glycol (antifreeze) solution recycled through a heat exchanger, enables the water-mixture to be cooled to a much lower temperature. A low speed pump is needed for circulation, with controllable flow rate to enable the temperature of the fermenting wine to be adjusted.
3) After the fermentation is complete:
Lower the lid of the variable-capacity tank so that it floats on the wine.
4) First racking:
Normally it takes about 4 weeks after the end of fermentation for the dead yeast to settle; however, this can be speeded up by chilling the wine to about 2 °C, in which case a few days at this temperature should be enough. This will also help to achieve tartrate stability (any excess tartrate will precipitate on the walls of the tank). After this the wine can be 'racked' (pumped) off from the sediment.
Normally racking is carried out through the flap-valve. If a tank is without a man-way door it is possible to rack off through the bottom outlet of the tank, although this is not normal practice; if the yeast-lees are compact enough only a small amount of lees is carried through. The first litre or so can be run off into a bucket, the juice from this can then be poured into the receiving tank leaving the solid sediment to be discarded. Pump into the bottom inlet of the receiving tank (clean and sterile); put the floating lid inside (with pneumatic seal deflated, and cooling tubes removed) so that it rides up with the wine.
Before starting to pump, put into the receiving tank a calculated
amount of wine sulphur; 7.5 grams per 100 litres of wine; providing 75 mgm/litre total SO2.
This is better for the wine than rousing it in afterwards.
Malo-lactic fermentation should never take place as the original process of concentrating the juice should have destroyed the bacteria.
5) After racking:
Measure the acidity of the wine with the Sulfacor test.
Calculate the amount of citric acid to adjust the acidity to 5.0 g/l.
If any acid needs to be added, use the rouser and add the acid crystals to the top of the tank, so that they are dissolved in the juice.
6) Sterile Filter and Bottle:
The wine usually needs rousing (for some hours) to remove excess CO2, unless you like spritzig/petillant wines. A small amount of Nitrogen gas can be squirted into the wine, with the lid off, but this would remove all of the CO2, which may not be desirable.
Test for protein stability, I have never found red wines to be protein unstable.
Measure and adjust the total SO2 level so that it is 50 to 75 mgm/litre.
To make the wine slightly off dry
and hence smoother: if there are no legal regulations about
the sweetening of the wine, it will be much cheaper to do this with some of
the concentrated grape juice (rather than Süss-reserve),
about 1%; carry out tastings at 0.5% intervals to ascertain the optimum % addition.
Add the desired amount and rouse in well.
Sterilise the ttles with 2% free SO2 solution, rinse with pure water afterwards.
Filter and bottle.