Page 14 - Grapevine Jan-Feb 2020
P. 14
In The Winery
The Essence of Good Winemaking
By: Dr Richard Smart, Dr Misha Kwasniewski, Alex Fredrickson and Dr Angela Sparrow
T hink about it, if you will, what is the sheep-shearing shed) also offered the possibility
essence of winemaking? A very important
for Angela Sparrow and I to investigate how the
extraction from grape skins might be improved.
question.
Angela initially worked as a technician in the exper-
How about if wine is were made just from the imental winery before enrolling as a PhD candidate
juice and pulp. What an uninteresting beverage it at the University of Tasmania in 2011.
would be. Alcohol only, with no aroma and no fla-
vour. Spirits are not so uninteresting. Our first effort was a modification to fermenter
design which showed little promise. The second
All of the chemical compounds which make wine was the light bulb moment. We figured that a sim-
such an interesting beverage are to be found in the ple way to improve skin extraction would be to
skins, maybe a few in the seeds. These compounds make skin particles smaller (skin fragmentation), so
include colour phenolics and the complex of flavour that they had a larger edge to surface area ratio.
and aroma compounds which help to make varietal There would be a smaller diffusion path of skin
wines so distinctive. constituents to the skin edge from smaller rather
than larger skin particles. So extraction would be
So the answer to my rhetorical question is: the enhanced.
essence of good winemaking is in skin extraction.
We find in fact that most grape berries coming out
This leads then to the important question of how of commercial crushers are simply squashed or flat-
winery practices might be conducted to facilitate tened, each with a rather small broken skin edge.
extraction from the skins. I remember well my We call this phenomenon “flattened spheres”, each
friend Dr Chris Somers, distinguished wine phe- “envelope” often contains skin and seeds. We ana-
nolic scientist from the Australian Wine Research lysed a sample of Pinot Gris berries from a Bucher
Institute making the statement: ”everything that Vaslin crusher, and found that there were 181 flat-
winemakers want in their wines is to be found in tened spheres, and only 12 skin fragments.
the pomace”. In other words the standard wine-
making factors is inefficient at extraction from the We evaluated fragmenting grape skins simply
skins. using a laboratory blender. We were of course
mindful that such an operation should not dam-
How can Extraction from the age the seeds, and careful checking revealed that
Skins be Improved? this was the case. Therefore we proceeded to
make experiments using our micro-vinification
I have long thought about this remark made by techniques, and found that the color and phenolic
Chris Somers and wondered how might extraction extraction of Pinot Noir was greatly improved, and
from grape skins be improved. I had the opportuni- sensory evaluation showed that so was the wine
ty to investigate some solutions to this problem in quality. We were of course thrilled!
2011. As part of my consultancy with Tamar Ridge
Wines near Launceston in Tasmania we had estab- Figure 1 (On top of page 14) shows Pinot Noir
lished an experimental winery. This allowed us to must samples one hour after treatment. The sam-
make pilot scale fermentations to evaluate vine- ple on the left shows typical flattened spheres after
yard trials aimed to improve wine quality. crushing, with limited color diffusion. The sample
on the right was crushed then fragmented, and see
This facility (in fact a converted apple-packing cum the difference in color extraction!
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