Avondale is farmed organically and biodynamically. No chemicals are used in the vineyards or in the cellar, nor are chemicals added to the grapes when they arrive at the cellar. All our fermentations are spontaneous and natural caused by the unique yeasts present on the grapes.
In conventional winemaking the use of chemicals creates a high risk that there won’t be high numbers of natural yeasts on the grapes, therefore natural fermentation will fail due to the interaction between the natural yeasts (also known as ambient yeasts) and chemicals. For this reason in conventional production methods, yeast must be added to the must. The yeast is tailor-made in a laboratory according to the varietal. For example, the Sauvignon Blanc yeast option has a specific flavor style which ultimately creates a generic tasting wine. These commercially bread yeasts are extremely strong, can cope with the chemicals/sulphites and overpower the natural yeasts stripping the wine of any unique and natural identity. Because they are so strong and ferment vigorously the fermentation cycle is very short lived which is great if you want your wine on the shelf within a month of harvest.
There are lots of different yeast strains responsible for the natural fermentation of wine – the more the better. In essence in the total ferment process we should have between 50 to 100+ different strains at work, the idea is to encourage this and not have one dominant strain resulting in more elegance and complexity.
The natural fermentation process starts with the gentle hand harvesting of the grapes. They are then brought to the cellar where whole bunches are gently pressed allowing the fermentation process to begin. The fermentation process is driven purely by the natural yeasts and the only external factor controlled by the wine maker is the temperature where necessary.
In the beginning of fermentation the juice will be dominated by many different yeast strains of Hanseniaspora, Kloeckera, Pichia and many others – then as the alcohol increases different strains of Saccharomyces and Candida will take over because of their higher alcohol tolerability and they will consume the rest of the glucose and fructose to ferment the wine to dryness.
As all our fermentations at Avondale are natural, each fermentation follows its own unique process. Whilst we have never had a stuck fermentation, fermentations vary in length from 9 months to 1 year for white wines and red wines should be quite a bit faster at a controlled temperature of 24 – 25 degrees for white, and 30 – 32 degrees for red.
To give this context, conventional fermentation takes 5 days which can be slowed down by reducing the temperature to 14-20 days.
The wines have two fundamental fermentation temperature regimes which also influence the longevity of wines. The first being Reductive Fermentation where the temperature is controlled at between 12 – 15 degrees, this shows fruit flavor preservation and encourages the yeast to struggle. The other option is oxidative approach which is the warmer process and ranges between 24 – 25 degrees for white, and 30 – 32 degrees for red. This process you sacrifice the upfront fruit that you get with the cold ferment but you preserve the true core fruit which is awesome for ageability, this is the route that Avondale follows. This process cannot be done with commercial yeast as the process would then take a mere few hours.
In conclusion natural fermentation is important to Avondale because the end result allows each wine to express its individual unique character in its texture, mouth feel, body, flavor, elegance and complexity as Mother Nature intended.