Impact of Brettanomyces on
Wine Quality
Lucy Joseph
Department of Viticulture and Enology
U.C. Davis
Introduction
• Brettanomyces is considered to be the primary
spoilage yeast in finished wine
• However, many consumers and critics like the
complexity that is derived from Brett growth
in wine
Compounds Produced by Brett
in Wine
• Signature spoilage compounds - ethyl phenols,
vinyl phenols
• Other spoilage compounds – acetic acid, ethyl
acetate, fatty acid, carboxylic acid
• Compounds that are positive – Esters, higher
alcohols, terpenes
Strain Collection
Alcohol
Aldehyde Ester
Ethyl Phenol
Fatty Acid
Terpene
Vinyl Phenol
Isoamyl
Nonanal
Ethyl
butanoate
4-ethylphenol
Butanoic
Ocimene
4-vinylphenol
Amyl
(active)
Pentyl
formate
4-ethylguaiacol
Heptanoic
Bisabolene
4-vinylguaiacol
2-ethyl
hexanol
Ethyl
isovalerate
Phenethyl
Ethyl
valerate
2-methoxy
phenyl
Ethyl 2methylbuty
rate
Undecanoic
Octylbutyrate
Amyloctanoate
Phenethyl
formate
Fruit/floral
chemical
Artificial
fruit/floral
Artificial
fruit/floral
Chemical,
smoke/spice
Sweaty/rott
en cheese
Floral resin Spicy wood
spice
smoke
medicinal
Initial Screen
• Defined medium was used
• Supplemented with amino acids
• All strains will make 4EP and 4EG
with coumaric and ferulic acids
Percentage of evaluations
Positive and Negative Perception
100%
90%
80%
%+/-
70%
%-
60%
%+
50%
40%
30%
20%
10%
0%
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83
Strains
Selection for Test in Wine
• Descriptors, intensity, and likability used to
score strains
• Out of the initial 83 that were successfully
screened in the initial screen, 17 were chosen
as “positive” and 5 as “negative”
Summary of Aroma for Strains Tested
in Wine
Table 5 Aroma summary of strains selected for growth in wine
Likeability
Number of aroma descriptors by category*
Strain
Intensity
+
+/- Sa An R So Ac M Fe D Sp W Fl
Fr
V
605
2.89
16% 58% 26%
0
1
2
4
11
0
4
0
2
1
6
2
0
2404
3.10
10% 40% 50%
0
2
5
5
3
0
8
0
1
1
8
2
1
2051
4.75
8%
42% 50%
3
2
2
4
4
0
5
0
0
1
12
0
0
2408
4.19
19% 44% 38%
0
3
3
3
5
0
4
1
3
4
1
5
0
2504
3.00
19% 31% 50%
1
3
0
1
4
0
5
2
3
5
4
3
1
2402
4.50
25% 13% 63%
2
1
2
2
3
0
4
2
0
2
3
0
0
2406
2.75
13% 50% 38%
1
1
1
2
2
0
2
1
0
3
2
0
0
2509
4.44
8%
50% 42%
0
0
7
0
5
0
2
2
3
2
6
0
0
2066
2.68
40% 30% 29%
1
0
0
3
3
3
4
2
3
0
4
1
1
2091
4.93
0%
42% 58%
1
3
2
3
7
0
4
1
0
5
6
3
2
2752
5.50
0%
38% 63%
0
0
5
4
4
0
1
0
0
3
2
0
0
2508
4.69
0%
58% 42%
0
1
6
2
2
2
3
1
4
3
3
0
3
2385
3.83
0%
45% 55%
0
4
5
4
6
0
8
0
1
3
7
0
0
2505
3.44
0%
50% 50%
0
2
3
2
3
0
7
3
1
5
4
5
0
2092**
6.08
0% 88% 13% 2
1
8
3
6
0
3
0
0
3
4
1
1
2077**
5.00
0% 67% 33% 2
5
6
3
9
0
4
0
1
0
3
0
0
*Sa=savory, An=animal, R=Rotten/Putrid, So=solvent, Ac=acetic, M=musty, Fe=fermentation, D=dairy, Sp=spicy,
W=woody, Fl=floral, Fr=fruity, V=veggie **denotes “negative controls”
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32
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SPME-GCMS
• These strains were also screened chemically
• Used defined medium supplemented with
– Aromatic amino acids
– Cinnamic acids and aromatic amino acids
• Goal was to identify strains that produced low
negative characters
Cluster
Analysis
of Strains
Important
Compounds
That
Determine
Differences
With Amino
Acids
Relative Concentration of Compounds in
“Most Liked” Strains – Amino Acid Supplemented
• Phenethyl acetate – Sweet, honey, floral rosy
• Ethyl decanoate – sweet, waxy, fruity, apple
• Ethyl hexanoate – sweet, fruity, pineapple, waxy
green banana
• Ethyl octanoate – fruity, wine, waxy, sweet
• 2-phenylethanol – floral, rose, rose water
• Octanoic acid – fatty, rancid oil, cheesy
• Ethyl acetate – nail polish remover, solvent
• 3-methylbutanoic acid – sour, stinky feet, sweaty, cheese
• Decanoic acid – rancid, sour, fatty, citrus
• 2-phenylacetaldehyde – honey, sweet, rose, green, grassy
Important
Compounds
That
Determine
Differences
With
Cinnamic
and Amino
Acids
Relative Concentration of Compounds in
“Most Liked” Strains – Amino Acid and Phenolic
Acid Supplemented
•
•
•
•
•
•
•
•
•
•
Ethyl octanoate – fruity, wine, waxy, sweet
2-phenylethanol – floral, rose, rose water
Ethyl decanoate – sweet, waxy, fruity, apple
4-ethylphenol – medicinal, Band-Aid, barnyard
4-ethylguaiacol – spicy, smoky, phenolic, clove
Octanoic acid – fatty, rancid oil, cheesy
Decanoic acid – rancid, sour, fatty, citrus
Phenethyl acetate – Sweet, honey, floral rosy
Ethyl acetate – nail polish remover, solvent
Decanol – waxy, floral, orange, sweet
Wine Descriptions (under $25)
•
•
•
•
•
•
•
•
•
•
•
rose petal and earl grey tea, baking spices
pepper, baking spices, flowers
violets and spices
bittersweet iris-like, brioche as well as butter
black licorice and roasted herbs
mocha and anise
spice, licorice and wild bush, mineral
peppery spice, dust
fruit with nutty, savory complexity
popcorn, brioche, grilled nuts
smoke-accented aromas, cola and spices
Wine Descriptions ($25 to $50)
• forest floor, black pepper, moss covered tree bark and game
• potpourri and orange zest, with a subtle smoky overtone; spicy
floral, loamy earth, cedar and savory herb
• Sappy, spice-accented, medicinal cherry note, with clinging
spicecake and cracked pepper
• musky aromas, smoked meat, bacon fat and licorice and chocolate
flavors
• smoky, savory; smoke and bacon with chocolaty finish; violets and
baking spices
• bread crust, coffee and dark chocolate and a touch of spices
• crushed rock, camphor, and a hint of pen ink
• smoked meat, cracked pepper, tobacco and masses of crushed
stone / mineral
• creosote, minerals, and toasty oak
• incense and rose oil; sandalwood and tea leaf
Wine Descriptions ($50 to $75)
• black truffles, roasted meats, charcuterie,
incense, roasted herbs and licorice; spiceaccented aromas and potpourri, hint of
spicecake; charcoal notes, long, tarry finish
• graphite, savory herbs, white flowers, orange
peel, spices, nutmeg, clove; mineral and cedar;
violet, grilled meat and tar, cassis and licorice
• bay leaf, sage, anise, toast and chocolate, mineral
and earth; roasted coffee, herb; earthy black
currant and fig, and charcoal-infused fruit
• exotic, smoky oak; sage and underbrush, even a
touch of gun oil
Using Descriptors
• Wines were purchased from an online site
by searching using descriptors from the
aroma wheel
• These wines were tested for the presences
of microbes by plating, microscopy, and
qPCR
• Wines were also analyzed for 4EP and 4EG
What We Found
• 35 wines were selected
• 17 had viable lactic acid bacteria by plating
(49%)
• 9 had viable Brett by plating
• An additional 5 had Brett by qPCR
• Another 4 had Brett by 4EP and 4EG levels
• A total of 18 showed evidence of Brett (51%)
• All of the wines were positive for microbial
contamination