Wine with a touch of Eucalyptus?

Australian wine scientists are exploring the traditional practices Aboriginal people used to produce fermented beverages, with a view to trying something non-traditional.

A team from the University of Adelaide and the Australian Wine Research Institute (AWRI) has discovered there are complex microbial communities associated with the natural fermentation of sap from the Tasmanian cider gum (Eucalyptus gunnii).

“Cider gums produce a sweet sap that was collected by Aboriginal people to produce a mildly alcoholic beverage,” says the AWRI’s Cristian Varela, lead author of a paper in the journal Scientific Reports.

“The drink known as way-a-linah was made by the Tasmanian Palawa people in a traditional practice where the sap was given time to spontaneously ferment.

“To the best of our knowledge, the microorganisms responsible for this traditional Australian fermentation have never been investigated or identified.”

E. gunnii is native to the remote central plateau of Tasmania but is also commonly planted as an ornamental tree in parts of Britain and Europe – perhaps because it shows exceptional cold tolerance for a eucalypt (which likely also explains the high concentration of sugars in its sap).

It has been well studied as a possible source of bioenergy, phytochemicals and essential oils, the researchers say, but not in relation to its fermentation potential.

In fact, they say, while many indigenous fermented beverages have been produced worldwide – from the Ethiopian honey wine tej to the maize-based chicha of Peru – only a few have been characterised from a microbiological perspective.

For their study, Varela and colleagues worked with the Tasmanian Aboriginal Centre and the Tasmanian Land Conservancy to collect 84 cider gum samples – 45 from sap, 29 from bark and 10 from soil – from three locations in Tasmania.

Using DNA sequencing, they identified the bacterial and fungal communities they found. Some could not be matched to existing databases, suggesting they represent completely new classifications.

Analysis showed that although the same main fungal classes were common for cider gum and winemaking, genus diversity and/or relative abundance differed. Interestingly, the main genus responsible for alcoholic beverage fermentation, Saccharomyces, was barely found in the cider gum samples.

Research leader Vladimir Jiranek, from the University of Adelaide, says the work is shining a light on both the unique fermentations and their cultural significance.

“It also allows us to identify new strains, or species, of yeast and bacteria from the fermentations that are unique to Australia. Further work will characterise single microorganisms that have been isolated and grown from the cider gum.

“We are particularly interested in their fermentative abilities, their potential flavour impacts, how they’ve adapted to the cider gum environment and the possible symbiotic relationship they have with the trees.”

The Royal Institution of Australia has an Education resource based on this article. You can access it here.