Thursday, 30 January 2014

Racking

One of the many cellarhand skills that I have been learning and performing regularly thus far is racking. I will describe this task for you in detail, as it is critical in the winemaking process:  it can be make or break in determining wine quality.

Racking is required at a number of points in the journey of grapes to a finished wine.  The first racking for white wine occurs when the grape juice collected from crushing and pressing has been sitting in a stainless steel tank for a few days to allow the grape skins, seeds, pulp and other solids to settle out.  These 'lees' are what needs to be separated from the clear juice.

1. Sanitising
Once the winemakers are happy that the grape juice is ready for racking, the first step is to ensure that the network of hoses and pipework that is to be used (sometimes totalling 100m) is sanitised before it can be used to move wine.

2. Sparging Then it is necessary to disperse a 'cellar mix' of Nitrogen and Carbon Dioxide gas into the empty tank that is to be filled to ensure no oxygen is present, which could damage the wine. This works because the cellar mix is heavier than air and displaces oxygen, forming a protective blanket in the tank whilst grape juice is added from a valve at the bottom.


3. Transferring
Next comes the fun part, where you hook up your lines, kick start the pump and begin to transfer the juice. You can tell when the juice is nearing the level of the door because nothing will come out of the sample valve when it is opened. It is then important to keep checking until the door can be opened - and this is where the art of racking begins.

4. Racking
Somewhere in the murky depths below is the layer of lees.  The challenge is to remove as much clear juice as possible (so as not to waste any) whilst also ensuring no lees are sucked up by the pump to contaminate the transferred product. To achieve this, a 'racking arm' is used.  This tool attaches to the side of the door, forming a pivot for a suction arm which can be slowly lowered down as the juice is pumped. Once the fluffy top of the lees become visible below the surface, you slow the pump right down and continue until it is no longer possible to suck clear juice (this is where technique and experience comes into it!).

5. Cutting Out
Once satisfied, the next job is to 'cut out' of the tank.  The network of transfer lines will still be full of juice once the pump is stopped and all this good juice needs to be sent to the tank.  So a water hose is connected up to the pipework at the racking end and started up.  At the tank end, there is a T-piece and a section of clear glass where you can see when the liquid stream turns from yellow coloured juice to clear water.  At this point, you quickly switch the valves at the T-piece so water goes onto the floor and nothing further goes into the tank (again, this takes much practice to master).

The lees remaining in the original tank are actually collected and treated through a filter to reclaim any trapped  juice. This juice (a small amount in comparison to the whole tank) is used for inoculating the yeast cultures - a process that I will be sharing as I learn more about it.

Whoever thought pumping some liquid from one place to another could be so involved! And I didn't even mention that you have to clean the whole tank when you are finished too...