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Dr Paul Boss CSIRODR PAUL BOSS is inhaling the complex molecular bouquet of flavour in his role as research scientist in CSIRO’s Plant Industry, working in the laboratories on the Waite campus in South Australia.

For the past decade Boss has been investigating the genes responsible for wine’s aroma and taste.

He leads a research group investigating flavour and aroma development in grape berries, with a particular interest in the link between grape secondary metabolism and wine flavour and aroma.

Originally from New Zealand, Boss moved to Australia and completed his doctorate in the molecular biological processes involved in producing anthocyanin pigments, which are responsible for colour in grape berry skins.

He then worked at CSIRO’s Plant Industry to investigate flower cluster formation in grapes with the goal of rapidly inducing flower production in young vines.

Now Boss and his team work on investigating flavour and aroma development in grape berries and the fruits of their labours are paying off.

The team has uncovered the gene responsible for producing capsicum/vegetal flavour compounds in grapes.

Identifying the gene responsible, and understanding how these compounds are produced in the fruit, means winemakers can have new ways of managing flavour in the vineyard in the future.

Boss said he gets the most satisfaction from working on flavour and aroma in wine.

“It feels good to do science you hope will benefit the wine industry,” Boss said.

“Having positive outcomes and seeing grape growers and winemakers taking up the results of our work is what drives me,” he added.

“I like complexity. It can be daunting to start with but I like to have difficult challenges to work on. When something is complex, you can really get your teeth into it.

“The genetic and biochemical processes involved in creating the signature flavours of your favourite drop are incredibly complex.

“Some grape varieties do not produce the compounds (methoxypyrazines) responsible for the capsicum/vegetal aroma, so by comparing genetic maps of grape varieties which do produce the compounds with those that don’t, we were able to pin down the gene responsible.

“We’ve known about methoxypyrazines, the compounds responsible for the green flavours in Cabernet Sauvignon or Sauvignon Blanc for years, but now we understand what gene is responsible for this character.

“At the moment I’m investigating when flavour compounds and precursors are produced during berry development. It is commonly thought that ripening is the key period where berry flavour develops, however we’ve found that some compounds are made in the early stages of grape development, and these can have positive or negative effects on wine composition.

“Understanding how these compounds are formed will allow us to optimise the process and provide growers with information about how to vary their vineyard management to produce better wine grapes.”

The volatile compounds responsible for aroma and flavour are exposed to a number of influences from vineyard to glass.

Boss said there are more than 800 volatile compounds in wine, interacting and sometimes suppressing each other.

But he said he and his team are teasing it apart, looking for associations between wine sensory characters and the compounds in grapes and wine.

For example, the main distinction in Cabernet Sauvignon seems to be that some compounds have a ‘green’ character while others are associated with more fruity flavours.

There is a growing understanding of the compounds which contribute to aroma and flavour in the finished wine, but there is currently little understanding of how compounds in the grape berries contribute to the final flavour and aroma characteristics.

Identifying these compounds, understanding how they are made and how they make it into wine opens the door to new ways of managing flavour in the vineyard.

Boss is also currently involved in developing objective measures of quality in grapes in collaboration with Dr Dave Jeffery and Dr Susan Bastian at the University of Adelaide.

“If we can objectively measure grape flavour attributes in the vineyard, it would be possible to predict and optimise wine flavour and aroma before the grapes are even harvested,” Boss said.

“That would provide tools to optimise grape flavour potential in the vineyard and deliver the means of producing grapes with a desired chemical profile that can be used to make wines of a specified flavour profile,” he said.

Boss is happy to talk about his work inside and outside the lab and his work hasn’t taken away the enjoyment of drinking wine.

“There is nothing better than when someone hands me a glass of wine and says ‘this is interesting, try this’.

“I look for new ones to include as part of my work. Occasionally I will bring the wine into work and run it on the machines to see if there is anything unusual about it. I’m always looking for something a little different.”

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