1. Impact of Brettanomyces on Wine Quality
Lucy Joseph
Department of Viticulture and Enology
U.C. Davis

2. 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

3. 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

4. Strain Collection

5. 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
Undecanoic
Phenethyl
Ethyl valerate
2-methoxy
phenyl
Ethyl 2-methylbutyrate
Octyl-butyrate
Amyl-octanoate
Phenethyl formate
Fruit/floral chemical
Artificial fruit/floral
Chemical, smoke/spice
Sweaty/rotten cheese
Floral resin spice
Spicy wood smoke medicinal

6. Initial Screen Defined medium was used Supplemented with amino acids
All strains will make 4EP and 4EG with coumaric and ferulic acids

7. Positive and Negative Perception

8. 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”

9. Summary of Aroma for Strains Tested in Wine

10. 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

11. Cluster Analysis of Strains

12. Important Compounds That Determine Differences With Amino Acids

13. 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

14. Important Compounds That Determine Differences With Cinnamic and Amino Acids

15. 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

21. 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

22. 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

23. Wine Descriptions ($50 to $75)
black truffles, roasted meats, charcuterie, incense, roasted herbs and licorice; spice-accented 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

24. 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

25. 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