Wine flavour precursors revealed in new research
Scientists at The Australian Wine Research Institute (AWRI)
are investigating the development of the in-mouth flavour we perceive when
drinking wine
It’s the sort of research – and topic – that can’t help but
pique the interest of wine drinkers and scientists – what really causes the
flavours and lingering aftertaste we get in our mouth when we taste a memorable
glass of wine.
For the past 14 months, scientists at The Australian Wine
Research Institute (AWRI) have been looking in depth at glycosides – flavour
compounds attached to sugars in wine – and have shown they play a role in the
development of the in-mouth flavour we perceive when drinking wine.
Now, with proof of concept achieved, the AWRI team is moving
onto even more exciting discoveries.
The four-year project is funded by the Australian Grape and
Wine Authority and titled, ‘Flavour precursors: contribution to wine aroma,
in-mouth sensory properties and flavour release’.
AWRI scientist Mango Parker said the first year of research
had delivered some mixed results.
“First, we extracted flavour precursors, targeting
glycosides in particular, from a range of Chardonnay and Shiraz wines and
tasted them in a blind tasting,” Ms Parker said.
“Unfortunately there was almost no detectable flavour that
developed in the mouth arising from the glycosides. Luckily we had included a
wild card Gewurztraminer wine that was loaded with monoterpene glycosides, and
tasters could detect a floral or fruity flavour that built in the mouth after
tasting.
“I should point out that we went to great lengths to make
sure that we removed all the volatile aroma compounds, so our precursors didn’t
have any noticeable floral or fruity smell.”
By removing the aroma-causing compounds from the wine, Ms
Parker said they could be sure that any flavours that developed in the mouth
immediately after tasting were due to glycoside precursors releasing aroma
compounds by a process called hydrolysis.
“When we started in this area just over a year ago, we
didn’t know for sure if the flavour precursors naturally present in grapes
and/or wine would be potent enough to be able to taste in a wine-like matrix,”
she said.
“We’ve since followed up with a formal sensory study with
randomised order, triplicates of each sample and even black glasses to conceal
any slight colour, which confirmed our findings.”
Prior to starting this research, Ms Parker was investigating
the role of glycosides in relation to smoke taint.
“The chemistry going on in this current project, the
hydrolysis of glycosides in the mouth, is similar to what was seen with smoke
taint,” Ms Parker said.
“In that case, we could explain why some wines could smell
fine (no unusual smoke aroma) but after wines were tasted, volatile phenol
glycosides could impart a smoky, ashy flavour that some people found
objectionable.
“We investigated things like the effect of alcohol and pH on
this phenomenon, and did a series of thorough sensory experiments including a
full reconstitution study. So we knew that glycosides could impart lingering
flavours to wine, if the compound attached to the sugar was potent enough and
the concentration of the glycosides was high enough.”
In the case of smoke taint the glycosides were present due
to a contamination of the grapes by smoke, but Ms Parker said her current
project was focusing on naturally occurring flavour precursors and, thankfully,
“more of the pleasant flavour spectrum”.
Eventually, she said, the final goal of the project will be
to develop a better understanding of the flavour of wine in-mouth that is due
to precursor compounds, as well as retronasal (aroma by mouth) perception of
volatiles.
“For the wine scientists, it will mean being able to
characterise glycoconjugates and amino acid conjugates of volatile compounds,”
Ms Parker said.
“We will be able to assess the extent and sensory
significance of in-mouth breakdown of glycosides, amino acid conjugates and
free volatiles such as esters and determine the relationship between levels of
key precursors in grapes and the amounts remaining in wines.
“We should also be able to determine the effect of other
wine constituents, such as alcohol and non-volatiles on in-mouth release and
sensory properties of precursor-derived volatiles.
“Winemakers will have a better understanding of the factors
that are important for flavour persistence and overall intensity, which are
important features of high quality wines.
“This will lead to better analytical targets for quality
markers for grapes and wines,” Ms Parker said.
Commenti
Posta un commento