Impact of Brettanomyces on Wine Quality

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

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 DifferencesWith 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 DifferencesWith 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 • Octanoicacid – fatty, rancid oil, cheesy • Decanoicacid – 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