Friday, April 13, 2007

Vintage 2007

Refractometer readings of a vineyard sampling showed the Cabernet sauvignon to be at a sugar level of around 12° Baume. The older vine leaves were starting to turn red which is suspected to be a result of a phosphorus deficiency in the soil (low pH) rather than the onset of autumn. Also a few bunches were beginning to shrivel which was more evidence that the vines had run out of "puff". So it was time to pick.

Easter Monday seemed a good time to start so under sunny blue skies, after the morning dew had dried off, we started hand harvesting. It is always fun battling the spiders, bees and ants as well as other creepy crawlies that have taken up residence in the vineyard over the last six months. And all the time you are concentrating on not cutting one of your fingers off.

Buckets were soon filled without incident and transferred to the "winery" otherwise known at other times of the year as the garage.
Hence our unofficial wine appellation classification of Vin de Garage.

Crusher / Destemmer and Fermenter
Here we have all the necessary basic equipment to make wine. But there is none of the high technology and sophistication of a modern winery. Therefore we rely on quick processing, good equipment hygiene and a detailed technical knowledge of winemaking techniques to protect the product from possible spoilage during the vinification phase.

The bunches were tipped into the crusher/destemmer where they are run through rollers to gently break the berry skins. The berries are then "beaten" off the stalks by rotating paddles and the crushed destemmed grapes fall through a stainless steel screen into the open fermenter.
Must in Open Fermenter
The stalks are ejected through the end of the machine and are eventually returned to the vineyard as mulch. Too many stalks in the ferment produce off flavours in the finished wine.

Tests on the resultant juice by refractometer and hydrometer confirmed a Baume reading of 12.0° . This means the wine will have an alcohol content of around 12%.
pH or acidity activity was 3.7. Acid levels are important as this determines the taste balance of the wine as well as how well certain additives eg. sulphur do their job. Acid levels can be increased (and pH reduced) by the addition of tartaric acid which is one of the naturally occurring acids in grape juice. The other main one is malic acid. Warm climate grapes are usually low in acidity and we keep the pH of our red wine between 3.5 and 3.6 by acid addition. Red wines usually have lower acidity than whites.
Another important measurement of acidity is titratable acid (TA) measured in g/L tartaric acid and sometimes called, wrongly, total acid.

Essential Winemaking Tools:
pH meter, hydrometer, refractometer
In Europe, sugar can be added at specified levels to grape juice to increase the final level of alcohol of wine. This is necessary as climatic conditions do not always allow grapes to ripen enough and wines of low alcohol are thin and insipid.
In the New World eg. Australia and the USA, the addition of sugar is prohibited. However in Australia the addition of grape juice concentrate (made by freezing the juice and removing the water as ice) is allowed but our warm climate most years guarantees grapes ripening to the required level. It should be pointed out that not all varieties are allowed to ripen to the maximum possible sugar level. New thinking has developed the flavour ripe theory where some grapes are picked at a lower sugar content according to the wine style being made eg. Semillon in the Hunter Valley of NSW is picked at between 10.0° and 11.0° Baume to produce a typical Hunter style. The same grape in Western Australia is allowed to ripen to 13.0° + Baume producing a bigger fruitier wine with less varietal characteristics. Some viticulturists even look at seed ripeness to determine when grapes should be picked.

Yeast and LAB Cultures
Back in the winery, sulphur was added to protect the must (grape skins, seeds and juice) from oxidation and wild yeasts before a controlled fermentation begins. This is done by adding a calculated amount of potassium metabisulphite at very low ppm rates.
A calculated amount of a commercial dried wine yeast (Saccharomyces cerevisiae) is then rehydrated in warm water. There are many wine style specific strains of that species available and this year I am trying a Bordeaux strain. Wild yeasts are present in all vineyards and they too can ferment the wine. But wild yeast fermentation is fraught with danger eg. slow or stuck fermentation and off flavours. Some say wild fermentation gives a wine special character. Maybe one day I will be brave enough to try it.
A lactic acid bacteria (LAB) culture was also rehydrated. This is added to the wine to initiate malolactic fermentation (MLF) where the bacteria convert the rather harsh malic acid in the grapes to the softer lactic acid. This also stabilizes the finished product. MLF can occur at any time but usually after the wine is made and is in storage.
It is essential that MLF occurs before bottling as a by-product of the reaction is carbon dioxide. This can make the bottled wine ‘fizzy’ and a bit musty tasting and can even blow the corks out of the bottle.

Disassembled Crusher Destemmer
The yeast and the LAB were then added to the must. The yeast metabolises the sugar in the grape juice turning it into alcohol and carbon dioxide. This takes some time to begin especially since the added sulphur initially inhibits the yeast.
But after a while the sulphur is "bound" to the red pigments in the grape skins and fermentation starts in earnest with increased temperature and obvious foaming. The crushed grapes release their juice as the alcohol level rises and the skins start to float to the surface. This layer is called the cap.
The carbon dioxide produced is now what protects the wine from oxidation. Another result of increased alcohol is the extraction of the red colour and tannins from the skins. Almost all grape juice whether from white or red grapes is clear with only the skins giving it colour. It is therefore necessary to keep pushing the cap down into the fermenting juice to extract as much colour and tannin as possible. This is done 4-6 times a day. Purple hands and arms result.
But there is nothing like the smell of fermenting wine up close.
Red wine is usually stored in oak barrels which, during controlled ageing, impart an oaky flavour to the wine. Wine barrels are very expensive, around $1000 for a hogshead (300L), so a cheaper way to get oak character is to add mini staves to the ferment. The two main types of oak are American and French. Like the barrels the staves are available in varying degrees of charring or toasting. This time I used medium toasted French oak in keeping with the Bordeaux style.

Oak Staves
After 7 days enough colour and tannins have been extracted from skins and it was time to drain the still fermenting wine off them.
Basket Press
We use the winepress for this, bucketing the must into the press basket and transferring the free running wine into a variable capacity stainless steel tank. The lids of these tanks float on the wine surface and seal by an inflatable tube.

Then the skins remaining in the basket are pressed slowly and thoroughly extracting more wine which has increasing levels of tannins and colour as the pressure increases. These pressings are also added to the tank along with the oak staves already removed from the ferment.
The skins that are left in the press (the marc) are almost dry and form a solid "cake" which is dumped back onto the vine rows as a fertiliser/mulch.

The wine is now left to finish fermentation and begin the settling process where solids begin to "fall out" and wine starts to clarify. We know when fermentation has finished when the Baume reading is below zero ie. no sugar is left.
The wine will then go through a number of racking processes where the clarifying liquid is separated from the settled solid residue. There are a number of settling aids eg. bentonite, but I prefer to let things happen naturally, albeit much slower, as any additions tend to strip the flavour. During this time oxidation can be a real problem so we will keep the wine under a blanket of carbon dioxide in the sealed tank. Any addition of sulphur, the normal antioxidant, at this stage would inhibit MLF.
VC Stainless Steel Storage Tank
So that’s the story so far. More on the progress of our 2007 vintage later.
White wines are made a little differently but that will be a blog topic for next year’s vintage.

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