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Thursday, July 31, 2014

Making Good Wine: Fermentation Part Two (White Wines)

The juice now separated from the skins, sulphured and rests for 24 hours in demijohns. The prior skin contact will evolve in the flavours of the finished wine.

At this time it is possible to clarify the juice by continuing to chill but choosing not to clarify leads to a richer wine.

Now is the time to perform some testing. Firstly sugar levels using either S.G. or as it is done at HHF a refractometer. Now that all the grapes are combined and everything standardised the reading is accurate. Whether sugar is to be added really depends on the grape variety. Some like Hunter Semillon will do fine at 18.5 Brix (alcohol level of 10.5%). As a general rule at HHF anything above 20 Brix is fine as long as the fruit is ripe. Although there is more comfort in 21.5 Brix. At that level the wine has some body and keeps well without too much sulphur.

The second test which adds value is the pH test using either pH papers which are cheap but not as easy as a meter, although the meter needs to have calibration checked when unused for a period. Various guides recommend a lower level of 3.0 and an upper level of 3.3 through to 3.5. A goal of 3.25 is ideal and adjust only with Tartaric acid. 3.5 is the absolute upper limit but with 3.25 much less sulphuring is required.

If it has been a dry or drought year then yeast nutrient is critical. But don't use a lot and only add it after one third of the way into the fermentation. add the last yeast nutrient at two thirds through the fermentation and none after that.

While the testing is going on a bit of juice has been taken and the sample container sits in a bowl of hot water to get the sample to 40 C at which point the yeast is added. When the yeast commences fermentation a little cold juice is added until the temperature drops by no more than 10 C. This is left until the fermentation fires up again and then more cold juice is added and so on until the temperature of the yeasted juice falls to within 10 C of the main batch of juice. It is then gently added. Now wait until the airlock begins bubbling, usually about 24 hours.

There is a school of thought that the airlock should now be removed and replaced with cotton wool to allow the gases to vent more easily, especially any off aromas.. At HHF both methods have been used with success. although an airlock is safer.

The demijohn must now be slowly cooled to between 10 and 15C. This is done by placing the vessel into a refrigerator with an adjustable thermostat. The cooler fermentation results in the production of more fruity esters.

Test the sugar levels of the wine every day to follow the falling levels. At the same time shake up or stir the sediments in the fermentation container. This will add a complexity to the final wine. When two thirds of the sugar has expired take the demijohn out of the cooling chamber and allow it to finish at a higher temperature but not more than 30 C, 27 C being ideal. This serves two purposes. Firstly, helps prevent a stuck fermentation and secondly, adds another dimension to the final wine. All these manipulations do really add complexity into the wine some of which may not be apparent until the wine has aged a few years.

At this two thirds point when the wine reaches the ambient temperature, usually about a day, it ideally should be racked into vessels with as little head space as possible to finish fermentation. At the end of fermentation allow 30-40 days for the sediment to settle and then rack into clean containers. Getting it off the gross lees is important to prevent the production of Hydrogen Sulphide from the dead yeast cells.

When racking off gross lees is also the best time to add oak chips. Anywhere from 0.5 to 4 grams/litre although 5 grams has shown a good result in Semillon. The amount of Oak really depends on the fruit ripeness. More ripeness handles more Oak. Don't use Oak on Sauvignon Blanc or Traminer as they have strong spicy aromatics of their own.

It can be racked again if desired although at HHF the least amount of handling has produced the best results. If lees really build up then a racking is a good idea but if there is only a fine film it is left alone. 

Bottling is best done during the period leading up to no moon and ideally in the cool of mid to late Winter. The experience here is no sediment problems even after a number of years in bottle. Natural settling is far superior to fining or filtering.


  1. Hello Jean and John, You've been quiet; hope all is well with you?

    1. Yes Barb, all well just a bit hectic preparing for Spring and monitoring a calving herd. Finding time to blog is difficult at the moment. Thanks for the concern.