Wineries need to make increasingly complex decisions around whether to use conventional cylindrical stainless–steel tanks, traditional oak barrels, or a selection of alternative types of vessel for fermenting grape juices into wine.
Alternative vessels include those made from forgotten and new material such as concrete, clay, or food-grade plastics. The use of oval-shaped vessels has also increased. While many claims are put forward around specific benefits from certain vessels, there is little scientific data about their impact on the composition and attributes of the finished wines.
A team of scientists set out to carry out a complete chemical, physical, and sensory characterisation of wines made from Sauvignon blanc grapes fermented in different vessels.1
After harvesting grapes from a vineyard in the Leyda Valley in Chile, the juice was extracted and fermented in four different vessels: 150 L cylindrical stainless-steel tanks, 980 L polyethylene oval–shaped tanks, 450 L concrete oval-shaped tanks, and 225 L clay jars.
The researchers found that the finished wine fermented in the concrete vessels had slightly higher acidity than that produced in the stainless-steel tanks, while products fermented in clay jars had the lowest amounts of specific volatile compounds.
The team included microelemental quantification using microwave plasma atomic emission spectroscopy. They used ultrapure water generated from an ELGA PURELAB® laboratory water purification system to reduce the risk of adding contaminants that might affect their results.
The wine fermented in concrete vessels contained the highest amounts of certain microelements, supporting the idea that inorganic compounds are released from the surface of this type of vessel during the process.
Oval–shaped vessels are thought to favour the formation of convection currents inside the liquids during fermentation, helping to solubilise macromolecular compounds. But the researchers found no differences in either the turbidity or polysaccharide content of the wines from differently shaped vessels.
However, wines produce in oval–shaped vessels did require a lower dose of a chemical needed to achieve protein stability than the others, suggesting that the vessel shape could impact on the stability of white wine proteins.
The wines fermented in oval-shaped vessels also had small differences in certain chemical and physical characteristics compared to other shapes. And a panel of wine experts described the fermented in these polyethylene tanks as the most bitter, and the product from these concrete tanks as the least fruity.
The study concludes that the type of vessels used to ferment white wine has little impact on its final colour, phenolic, or polysaccharide contents. But it may have a slightly greater impact on the wine acidity, elemental composition, volatile compounds content, potential stability, and sensory perceptions of the products.
However, as any shifts were all very small, this suggests that the fermentation vessel may not make much difference to the composition or qualities of the resulting wines.
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Dr Alison Halliday
After completing an undergraduate degree in Biochemistry & Genetics at Sheffield University, Alison was awarded a PhD in Human Molecular Genetics at the University of Newcastle. She carried out five years as a Senior Postdoctoral Research Fellow at UCL, investigating the genes involved in childhood obesity syndrome. Moving into science communications, she spent ten years at Cancer Research UK engaging the public about the charity’s work. She now specialises in writing about research across the life sciences, medicine and health.