Luke Bohanan, Jeff Strekas, Roger Boulton, Hildegarde
Heymann, and David E. Block
Department of Viticulture and Enology
University of California, Davis
Some winemakers believe that this
process may strip subtle aromas and
flavors from the finished wine.
Clarity
Microbial Stability
Many winemakers argue that this
process is not only bad for the wine but
actually unnecessary. Others find it is
essential for clarity and stability.
Some winemakers choose not to filter
to avoid robbing the wine of its true
character
Need a systematic study
to examine the effects of
filtration

Investigate any transient changes in chemical
composition during filtration

Investigate the extent of oxygen pickup
during the filtration process

Evaluate the sensory and chemical impact of
sterile cartridge filtration on red and white
wines
• 2007 Sonoma Valley
• Post ML, oak aging
Chemical Analysis
Sensory Analysis
• Push with nitrogen (no pump)
• Filter right into bottling line
• Extended one run of PVDF to
look at transient behavior
Time Points:
0 Weeks
3 Week
5 Weeks
7 Weeks
9 Weeks
…
Rep 3
Filtration
Through 0.45
µm PES Filter
Rep 2
Rep 3
Rep 2
Filtration
Through 0.45
µm PVDF
Filter
Rep 1
Rep 3
Rep 2
Rep 1
Rep 1
Control – No
Filtration
Filtration
Through
Empty
Housing
Rep 1
Cabernet Sauvignon
Table 2. Color changes during one filtration run
Least Significant Difference
A420*
0.028
A520*
0.0309
Color Hue* Color Density*
0.0037
0.0569
Bottles 97-98
0.3805A
0.4427A
0.8597BC
0.8232A
Bottles 133-134
0.3790A
0.4408A
0.8599BC
0.8198A
Bottles 24-25
0.3692AB 0.4302AB
0.8582C
0.7993AB
Bottles 4-5
0.3612AB 0.4227AB
0.8545D
0.7838AB
Bottles 50-51
0.3600AB 0.4178AB 0.8616BC
0.7778AB
Bottles 73-74
0.3597AB 0.4155AB
0.8656A
0.7752AB
Bottles 13-14
0.3513B
0.4090B
0.8590BC
0.7603B
0.3503B
0.4063B
0.8621AB
0.7567B
Bottles 36-37
* Different superscripts denote a significant difference at alpha = 0.05
Each reported value is an average of six replicates
1.0
Color Parameter
0.8
0.6
0.4
A420
A520
Hue
Density
0.2
0.0
0
20
40
60
80
Bottle Number
100
120
140
Table 3. Tannin changes during filtration run
Tannin*
mg catechin eq/L
Least Significant Difference
18.209
Bottles
Bottles
Bottles
Bottles
Bottles
Bottles
Bottles
Bottles
36-37
73-74
133-134
50-51
97-98
4-5
24-25
13-14
238.369A
234.368AB
230.577AB
226.222AB
225.059AB
221.117AB
219.803B
218.152B
*Different superscripts denote a significant
difference at alpha = 0.05
Each reported value is an average of six reps
300
Tannin (mg cataechin eq/L)
250
200
150
100
50
0
0
20
40
60
80
100
120
Bottle Number
Figure 2. Tannin as a function of bottle number. Bottles were sampled
from the bottling line during the course of filtration with a PVDF membrane
filter. Tannin was measured on a sample from each bottle using the
Adams-Harbertson Assay.
140
Not much difference during filtration—Now let’s
examine differences between the filtration treatments
Table 1. Flavor, Mouthfeel, and Aroma Standard Compositions
Standard
Bitter
Sour
Sweet
Astringent
High-Viscocity
Low-Viscocity
Berry/Currant
Cherry
Dried Fruit
Vegetal
Spice
Black Pepper
Composition
0.75 g caffeine*
1.5 g citric acid*
3.5 g sucrose*
312 mg alum*
30 g/L Polycose*
H2O
1 sliced strawberry, 3 sliced raspberry, 3 sliced blackberry, 5 mL cassis**
10 canned bing cherries, 3 tsp cherry juice, 2 tsp cherry pie filling**
15 raisins, 2 sliced prunes, 1 sliced apricot**
1 cm2 green bell pepper, 2 cut string beans, 1 tsp canned asparagus juice, 1
tsp canned green bean juice, 5 blades grass**
1/8 tsp cinnamon, 1/8 tsp all spice, 3 cloves**
1/8 tsp ground black pepper**
2.5 mL of 1 drop rose essence in 200 mL H2O, 2.5 mL of 1 drop violet essence
in 200 mL H2O**
3x1 cm pieces of leather shoe lace, 1/8 tsp liquid smoke**
1 drop nail polish remover in 10 mL H2O**
3 small American oak chips**
5 mL Vanilla flavoring**
1.5 chopped chocolate chips**
15 mL vodka**
Floral
Leather/Smoke
Solvent/Chemical
Oak
Vanilla
Chocolate
Hot/Ethanol
* added to 1L H2O
** added to 50 mL Franzia Cabernet Sauvignon
Table 4. Repeated Measures ANOVA Results
Pr>F Value
Time
Time*Filter Time*Rep Time*Judge
Berry/Currant
0.0835
0.1272
0.0163*
<0.0001*
Cherry
<0.0001*
0.2252
0.9941
<0.0001*
Dried Fruit
<0.0001*
0.5785
0.8705
<0.0001*
Vegetal
<0.0001*
0.6287
0.2929
<0.0001*
Spice
0.0095*
0.7531
0.936
<0.0001*
Black Pepper
0.0016*
0.9479
0.3753
<0.0001*
Floral
<0.0001*
0.5798
0.4427
<0.0001*
Leather/Smoke
<0.0001*
0.8235
0.0278*
<0.0001*
Solvent/Chemical <0.0001*
0.4957
0.5963
<0.0001*
Oak
<0.0001*
0.0191*
0.3618
<0.0001*
Vanilla
0.0003*
0.3555
0.9706
<0.0001*
Chocolate
0.0016*
0.8618
0.5329
<0.0001*
Hot/Ethanol
<0.0001*
0.9904
0.8951
<0.0001*
Astringent
<0.0001*
0.1419
0.5326
<0.0001*
Bitter
<0.0001*
0.4845
0.7347
<0.0001*
Sour
<0.0001*
0.8656
0.923
<0.0001*
Viscous
0.0014*
0.4533
0.1336
<0.0001*
* Value is significant at alpha = 0.05
Berry
4.5
Visc
0 weeks
Cherry
4
3.5
Sour
DrFruit
3
2.5
Astrin
Vegetal
2
Astrin
1.5
1
0.5
Bitter
Spice
0
CTL W0
EMP W0
Bitter
PES W0
PVD W0
EtOH
Pepper
Choc
Floral
Vanilla
Leath/Sm
Oak
Solvent
EtOH
Cho
Berry
4.5
Visc
4
3.5
Sour
4
Visc
DrFruit
Sour
Vegetal
2
Sour
Spice
0
CTL W0
1
EMP W0
0.5
Bitter
Spice
0
PES W0
Pepper
Choc
EtOH
Choc
Vanilla
Berry
4
Visc
Sour
DrFruit
3
2.5
2.5
2
Vegetal
2
Astrin
1.5
Vegetal
1.5
1
1
0.5
Bitter
9 weeks
Cherry
3.5
DrFruit
3
Astrin
Spice
0
CTL W7
EMP W7
0.5
Bitter
Spice
0
PES W7
EtOH
Pepper
Choc
Floral
Vanilla
Leath/Sm
Solvent
CTL W9
EMP W9
PES W9
PVD W7
Oak
Leath/Sm
Solvent
Berry
7 weeks
Cherry
3.5
Sour
Floral
Oak
Solvent
PVD W9
EtOH
Pepper
Choc
Floral
Vanilla
Leath/Sm
Oak
EMP W5
PVD W5
Pepper
Vanilla
Leath/Sm
Oak
CTL W5
PES W5
Choc
Floral
Solvent
4
Spice
0
EtOH
Pepper
Leath/Sm
Visc
EMP W3
0.5
Bitter
PVD W3
Floral
Vanilla
CTL W3
PES W3
PVD W0
EtOH
Vegetal
1.5
1
1
Oak
2
Astrin
Vegetal
1.5
0.5
DrFruit
3
2.5
2
Astrin
1.5
5 weeks
Cherry
3.5
DrFruit
3
4
Visc
2.5
2.5
Bitter
3 weeks
Cherry
3.5
3
Astrin
Berry
Berry
0 weeks
Cherry
Solvent
Figure 1. The ef f ect of sterile f iltration on Cabernet Sauvignon. All treatments including the control change over
time in the bottle. However, there are f ew signif icant dif ferences between the treatments at any given time point.
0.8
FloralA
0.6
ChocoA
EMP7
DrFruitA
CV2(17.6%)
PVD7
-1.5
-1
0.4
AstrinT
CTL7
PES0
LeathSmA
PVD0
PES7
0.2
PES9
CTL9
VanillaA
OakA
PVD9 0 SpiceA
CTL5 PVD5 0
0.5
EMP9 EMP5 EMP3
PES5 ViscousT -0.2
CTL3
SourT
PVD3
-0.5
-0.4
PES3
CherryA
EthanolA
EMP0
CTL0
1
SolChemA
BerryA
BitterTBlPepprA
-0.6
-0.8
CV1(40.9%)
VegetalA
-1
Figure 5. Canonical Variate Analysis (CVA) of sensory properties of Cabernet
Sauvignon after filtration. This CVA plot illustrates distinct difference over time with
very little difference as a function of filtration treatment.
Table 5. Color as a function of filtration treatment
Least Significant Difference
A420*
A520*
0.0491
0.0567
Color Hue* Color Density*
0.1058A
0.0043
Day 1 PVDF
0.3841A
0.4455A
0.8616A
0.8297A
Day 3 PVDF
0.3510A
0.4077A
0.8610A
0.7587A
Day 2 PES
0.3490A
0.4053A
0.8610A
0.7543A
A
A
AB
Day 1 PES
0.3670
0.4267
0.8602
0.7937A
Day 2 PVDF
0.3790A
0.4408A
0.8599AB
0.8198A
Day 3 PES
0.3765A
0.4382A
0.8596AB
0.8147A
Day 3 No Filter
0.3516A
0.4092A
0.8596AB
0.7608A
Day 1 No Filter
0.3791A
0.4412A
0.8594AB
0.8203A
Day 1 Control
0.3510A
0.4097A
0.8566B
0.7607A
0.3633A
0.4243A
0.8562B
0.7877A
Day 2 No Filter
* Different superscripts denote a significant difference at alpha = 0.05
Each reported value is an average of six replicates
Table 6. Tannin as a function of filtration treatment
Tannin*
mg catechin eq/L
20.868
Least Significant Difference
Day
Day
Day
Day
Day
Day
Day
Day
Day
Day
1
2
1
2
3
1
1
3
3
2
PES
PES
No Filter
PVDF
No Filter
Control
PVDF
PES
PVDF
No Filter
232.42A
231.03A
230.84A
230.58A
230.35A
230.16A
227.20A
226.56A
225.58A
217.85A
*Different superscripts denote a significant
difference at alpha = 0.05
Each reported value is an average of six reps
Merlot
• 2009 Oakville
• Post ML, oak aging
Chemical Analysis
Sensory Analysis
• Push with nitrogen (no pump)
• Filter right into bottling line
Time Points:
1Weeks
2 Week
4 Weeks
6 Weeks
12 Weeks
16 Weeks
…
Rep 3
Rep 2
Filtration Through
Pad, 1 µm Depth,
and 0.45 µm PES
Filter
Rep 1
Rep 3
Rep 2
Filtration Through
Pad, 1 µm Depth,
and 0.45 µm
PVDF Filter
Rep 1
Rep 3
Rep 2
Filtration
Through Pad
and 1 µm
Depth Filter
Rep 1
Rep 3
Rep 2
Rep 1
Rep 1
Control – No
Filtration
Filtration
Through Pad
Filter
Week 1
Key
1
15 5.000
2
1 MxBerryA
Mixed Berry
4.000
3
3.000
214MCherryA
Medicial
Cherry
CTL
2.000
13
4
3 FrVegA
Fresh
Vegitable
DEP
1.000
PAD
0.000
Cooked
Vegitable
12 4 CookVegA
5
PES
VDF
511 HerbalA
Herbal
6
6 BkPepprA
Black Pepper
10
7
9
8
7 EarthyA
Earthy
8 VanillaA
Vanilla/oak
Week 4
9 CdBoardA
Card Board
1
15 5.000
2
10 ChemA
Chemical
4.000
3
3.000
11 14SourT
Sour
CTL
2.000
13
4
12
BitterT
Bitter
DEP
1.000
PAD
0.000
13
AstrinT
Astringent
12
5
PES
VDF
1411 ViscousT
Viscousity
6
15 AlcoholT
Alcohol/Heat
10
7
9
8
Week 2
1
15 5.000
4.000
14
2
3
3.000
2.000
13
CTL
4
DEP
1.000
0.000
12
5
11
PES
VDF
6
10
PAD
7
9
8
Week 6
1
15 5.000
4.000
14
2
3
3.000
2.000
13
4
0.000
12
5
11
6
10
7
9
CTL
DEP
1.000
8
PAD
PES
VDF
Week 12
Week 16
1
1
15 5.000
4.000
14
15 4.000
2
3.000
2.000
13
4
0.000
5
11
6
10
7
9
CTL
8
PAD
PES
VDF
3
2.000
13
4
1.000
DEP
1.000
12
3.000
14
3
2
DEP
0.000
12
5
11
6
10
7
9
CTL
8
PAD
PES
VDF

Very few differences noted during filtration for
color and tannin-no transient is obvious

So far, no major differences observed between
filtered and unfiltered wine

Still completing chemical studies on red wines

Completed Week 4 of sensory panel for White
Wine.







Chik Brenneman
Paul Green
Jennifer Heelan
Ron Runnebaum
Tarit Nimmanwudipong
Sensory Panelists
Rodger Pachelbel


Gallo Sonoma
Silverado Vineyards

American Vineyard Foundation