THE most important step in making wine is the fermentation process. Stainless steel vessels have been used since the 1970’s, but nowadays there is a wide choice of other materials in all shapes and sizes. Traditionally, winemakers have kept it simple and used open top fermenters for red wine and sealed vats for white. For white wine protecting the wine from oxidation is key to keeping the fruit flavours. Open top fermenters allow the winemaker to macerate the juice in the skins and aerate the fermentation via a number of methods such as pump over, plunging the cap or rack and return. Getting oxygen into ferments is increasingly used. Once thought to be the scourge of winemaking it is now being harnessed. Oxygen is needed to start the fermentation and in red winemaking it stabilises the colour and softens tannins which makes wine more approachable at an earlier age.
Stainless steel is an extremely hygienic material and easy to clean. Vats can have insulated jackets or be glycol cooled to control fermenting temperatures. They do not transfer any flavours and depending on their size, can be moved around the winery. When empty they are comparatively light weight. Variable capacity stainless steel tanks allow the winemaker to place different volumes of wine into the tank as they have floating lids that can be sat on top of the liquid. Some companies have invested in rotary fermenters. These are large stainless-steel machines that rotate via different computerised programs to keep the must in contact with the skins. They ferment the wines quickly but need a lot of space in a winery and are normally suited to larger scale wineries.
Small oak barrels are used for fermenting white wines and are an essential method in producing wines like chardonnay that don’t rely on primary fruit characters. Small amounts of oxygen enter through the bung holes and staves, and when the bung is removed to stir the lees then the wine is further exposed. When new they transfer vanillin, which is the flavour of sweet vanilla to the wine. But as the barrel becomes older this is significantly reduced, making it more of a neutral vessel. Larger oak casks, capable of holding many thousands of litres, can be used to ferment wines such as riesling and is a tradition found in Alsace and Germany. Wood is a good heat retainer but because the wine soaks into the wood, their use is limited to white wines, then onto red and possibly ending up used for fortified wines. They need constant care with the possibility of bacteria infections such as brettanomyces. Best’s at Great Western in Victoria use a large 2,500 litre oak ‘foudre’ which was crafted in Burgundy to make their impressive Foudre Ferment Riesling.
Prior to stainless steel becoming available wineries used concrete vats that were built in situ. Old wineries will often have large wax lined square, round or rectangular vats fitted into the space that was available. Concrete was viewed as old fashioned and give a winery that historic or ‘un-renovated’ look. However, many of Australia’s best wines are still made in these types of vats. Concrete has had a facelift in the last twenty years with the introduction of the ‘egg’ shape vessels.
Egg shaped fermenting vessels have their origins in ancient history. But the first egg in modern times was used by Michel Chapoutier in 2001 in the Rhone valley so they have been around a while.
Joining the new concrete eggs craze are clay and other ceramic amphora vessels. These are being taken up by winemakers across the nation. Samantha Connew from Stargazer Wines in Tasmania makes a number of white wines in both of these and is happy with them “Obviously as they are a little porous you get that slightly oxidative dimension from the ferments but I also think there is a slightly different ferment dynamic in the eggs as well – the fermenting juice seems to move around the oval quite actively. In terms of negatives, like all of these non-stainless-steel vessels they do take a bit of diligence when they are empty.”
But their use is not confined to white wines. Robin Brockett, winemaker from Scotchmans Hill in Geelong, uses an amphora to produce his own label syrah. “I started using Amphoras in 2013. This was after I had seen some wines made using these vessels which were impressive. It piqued my interest. The amphoras are made from terracotta and are hand made in Tuscany.”
It is interesting to compare the oxidative benefits that Sam Connew sees with the way that Robin uses his amphora. He sees a number of benefits. “Firstly, the style of fermentation is quite different with amphora and the way the yeast mix within the must and fermentation occurs. With the vessels being lined with beeswax it forms an anaerobic environment. With the ability to seal the amphora after fermentation is complete it gives me the ability to leave wines on skins and whole bunch for a long period. The anaerobic conditions of the vessel gives a brightness to the wine and leaving it on skins for up to 8 months delivers a very different and precise tannin structure without it being hard and bitter.”
This reminds me of the delicious Vin Santo of Tuscany where the small barrels, known as caratelli, are sealed and left to ferment for up to three years.
Staying in Geelong, winemaker Dwayne Cunningham from Austin’s Wines uses his 620-litre concrete egg to produce his Curated Shiraz. “We use the concrete eggs for fermentation of red wine on skins. Typically, we will destem, with a portion of handpicked fruit, and place it directly into the egg” he explains. The wine spends approximately 21 days on skins, with gentle plunging twice a day. “As concrete is porous, the ferment will naturally breath over this period. Natural oxygen ingress through the concrete is really beneficial and rarely do I see hydrogen sulphide in these ferments. No temperature control is applied as the concrete insulates much more efficiently than stainless-steel. The must will almost cold soak as the natural yeast slowly begin the fermentation process. Typically, wild yeast in concrete takes a day or two longer to begin than wild stainless-steel ferments,” he adds.
From this treatment Dwayne gets more roundness in his wine. “I am aiming for mouthfeel, texture and hopefully gather a hint of slaty tannin. They generally show more of that vivacious Cab Mac character, but also show some subtle stalk character. Historically I have seen less of the green herbaceous stalk character than wines fermented in stainless steel with similar proportions of whole bunch.”
Robin thinks it is still early days, which in a way, is exciting. “My view is you can use any variety you wish but it comes down to how you utilise the vessel and the style you wish to achieve. It’s all about the structure of the wine and its purity of flavour. We have a long way still to go on how we use amphoras.”