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Grebneva Y 1,2, Herderich M 1, Rauhut D 2 , Bilogrevic E 1 and Hixson J 1
1 The Australian Wine Research Institute, PO Box 197, Glen Osmond (Adelaide) SA 5064, Australia, 2 Hochschule Geisenheim University, von Lade Str. 1, 65366, Geisenheim, Germany
Corresponding author’s email: [email protected]
Shades of Shading: Chemical and Sensory evaluation of Riesling grown under various shading techniques
Background
» Due to changing climate, Riesling may encounter a
tendency of developing an undesired premature 'aged'
character, also associated with 'kerosene-like' aroma
which is likely caused by the C13-norisoprenoid, TDN.
» TDN, as well as some other potent flavour
compounds found in Riesling, is derived from
carotenoids – photosensitive plant pigments.
» Plants regulate the formation of carotenoids in
response to environmental factors, especially light
quantity and quality.
Aims» Evaluate the effect of photoselective bunch zone
shading on key Riesling grape and wine parameters as
an adaptation strategy to changing climate.
» Examine the effect of coloured shadecloth (SC) on
TDN formation in Riesling wine.
» Understand the effect of coloured shadecloth
application in the vineyard on Riesling wine sensory
properties after 1 year and/or 2 years of storage.
ConclusionsRed
Green
Black
2018 vintage 2019 vintage
1-year-old 1-year-old
2-years-old Legend
1
Set-up
» TDN concentrations were reduced in juice and wine in
response to different shadecloth treatments without
negatively affecting the sensory properties of wines.
» Photoselective bunch zone shading provides a
promising and inexpensive adaptation to changing
climate.
»
Results
% r
ela
tive
to
co
ntr
ol
% r
ela
tive
to
co
ntr
ol
Grape Wine
0
50
100
150
YAN (mg/L) TSS (°Baumé) Malic acid (g/L) pH
Green SC Red SC Black SC
0
50
100
150
YAN (mg/L) TSS (°Baumé) Malic acid (g/L) pH
Green SC Red SC Black SC
0
50
100
150
Alcohol (% v/v) Glucose +
Fructose (g/L)
Malic acid (g/L) pH Bound TDN
(μg/L)
Free TDN (μg/L,
1 year)
Free TDN (μg/L,
2 years)
Green SC Red SC Black SC
0
50
100
150
Alcohol (% v/v) Glucose +
Fructose (g/L)
Malic acid (g/L) pH Bound TDN
(μg/L)
Free TDN (μg/L,
1 year)
Green SC Red SC Black SC
20
18
20
19
% r
ela
tive
to
co
ntr
ol
% r
ela
tive
to
co
ntr
ol
Control
n.d.
Control
Control
Control
» The use of coloured shadecloth significantly reduced free and total TDN concentrations in
wines compared to the control. While free TDN was not detected (n.d.) in all 2018 wines 1 year
post-bottling, after another year of storage and in 2019 wines the apparent reduction of TDN
levels in treated wines remained (green and black SC), as opposed to elevated TDN amounts
found in the control wines. Transmittance spectra
Control Green SC
Red SC Black SC
Wavelength (nm)
Tra
nsm
itta
nce
Wavelength (nm)
Tra
nsm
itta
nce
Wavelength (nm)
Tra
nsm
itta
nce
Wavelength (nm)Tr
an
smit
tan
ce
Absorption
spectra of
carotenoids
2019
2018 vintage 2019 vintage
1-year-old 1-year-old
2-years-old Legend
1
2 y
ea
rs1
ye
ar
2018
» The main difference was
noted for 'kerosene aroma’
rated significantly lower in
shaded treatments compared
to the control.
Recorded using Lighting PassportTM spectrometer (AsenseTek Inc., Taipei,Taiwan) interfaced with Spectrum Genius mobile phone application.
Lig
ht
red
uct
ion
by 7
7%
Lig
ht
red
uct
ion
by 8
3%
Lig
ht
red
uct
ion
by 8
1%
YAN: Yeast assimilable nitrogen; TSS: Total soluble solids
F: Flavour; A: Aroma
The authors thank Prue and Stephen Henschke for access to Eden Valley vineyards and grapes as well as the sensory panel for assessing the wines.
Sto
rag
e t
ime
vin
tag
e
vintage
