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Impact of Malolactic Fermentation Strain on Wine Composition

Impact of Malolactic Fermentation Strain on Wine Composition. Lucy Joseph U.C. Davis Department of Viticulture and Enology. Outline. Introduction to malolactic fermentation (MLF) Lactic acid bacteria metabolism Commercial inoculum Wine matrix effects Interaction with oak

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Impact of Malolactic Fermentation Strain on Wine Composition

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  1. Impact of Malolactic Fermentation Strain on Wine Composition Lucy Joseph U.C. Davis Department of Viticulture and Enology

  2. Outline • Introduction to malolactic fermentation (MLF) • Lactic acid bacteria metabolism • Commercial inoculum • Wine matrix effects • Interaction with oak • Timing of inoculation

  3. Malolactic Fermentation Any wine containing malic acid could be considered unstable. Certain indigenous bacteria can metabolize malic acid as a very poor carbon and energy source in the fermenter and in the bottle. Conversion of malic to lactic acid by a controlled malolactic fermentation prior to bottling eliminates the instability. It can be a problem to start, very slow activity, long time to finish and can start and stop.

  4. MALOLACTIC BACTERIA • What are they? • “bacteria”: single-celled non-nucleated microorganisms • “lactic acid bacteria”: produce lactic acid from sugar • Acid loving • Nutritional fastidious • Carry out many food fermentations

  5. Malolactic bacteria are lactic acid bacteria which can convert malic acid to lactic acid: CO2 Lactic Acid + Carbon Dioxide Malic Acid stronger acid weaker acid 2 carboxyl groups 1 carboxyl group

  6. Oenococcus oeni Only two species Oenoccocus oeni (formerly Leuconostoc oenos) are only found in wine Oenococcus kitaharae was ‘discovered’ in 2006 in the spoiled remains of a sake mash (shochu, high pH) and lacks the gene for malolactic fermentation

  7. What happens during a malolactic fermentation Deacidification Each gram per liter of malic converted to lactic creates a loss of 7.46 mM/L of titratable H+ ions, or 1.12 grams/L as tartaric measured by titration (TA) pH changes Micronutrients are sequestered Secondary metabolites can contribute to the flavor profile

  8. THE COURSE OF THE MLF Bacterial growth is finished several days after the conversion of malate to lactate. Full bacteria growth in wine is only 107 cells/mL, and the malate has usually disappeared at 106 cells/mL. (Diacetyl may be being formed at that time.)

  9. Relevant Metabolic Activity in Oenococcus oeni

  10. ML Metabolism

  11. Buttery CharacterDiacetyl

  12. Acetaldehyde Conversion J.P. Osborne et al. /FEMS Microbiology Letters 191 (2000)

  13. Mousy Character

  14. Commercial Malolactic Strains Oenococcus oeni Lactobacillus plantarum

  15. Commercial Strains - Inoculation • Direct inoculation Bacteria is pre-adapted and can be added directly to the fermentation • One step strains Bacteria need to be rehydrated and grown for 24 hours prior to addition • Traditional Requires growth and build up of inoculum prior to addition

  16. Commercial Strains-Selection Criteria • pH tolerance • Alcohol tolerance • SO2 tolerance • Temperature range • Competitive ability • Stuck MLF • Biogenic amine production

  17. Commercial Strains-Sensory Diacetyl production Color stability Mouthfeel Varietal enhancement Avoidance of defects, i.e. vegetative, sulfur Interaction with oak

  18. Wine Matrix Effects

  19. Cultivar & Strain Influence

  20. Compounds found in MLF wines by GC-MS • Purge and trap system of Montrachet wines • 4-Methyl-3-pentenoic acid • Methyl acetate (Sweet, solvent-like) • Ethyl hexanoate (Fruity, rum-like) • Hexyl acetate (Fruity) • Freon 114 extraction of Epernay 2 wines • 1,12-Tridecadiene* • Hexadecanoic acid (mild waxy)* • 1,2-Benzene dicarboxylic acid (mild ester)* • Farnesol (floral)* *Spectral fit < 900 Am. J. Enol. Vitic., Vol. 43, No. 3, 1992 R. M. AVEDOVECH, M. R. McDANIEL, B. T. WATSON, and W. E. SANDINE

  21. Other Reported Flavor Enhancers 1-hexanol - fruity ethyl acetate - fruity ethyl lactate - buttery diethyl succinate - brandy butyrolactone – aroma enhancer glycoaldehyde – aroma complexity, browning

  22. MLF in Oak Bacteria can breakdown glycosides in solution to release the aglycone

  23. Breakdown of Glycosides Glycosidic activities for a selection of Oenococcus oeni strains on four substrates: p-nitrophenyl-β-D-glucoside, p-nitrophenyl-α-L-arabinofuranoside, p-nitrophenyl-α-L-rhamnopyranoside, p-nitrophenyl-β-D-xyloside

  24. Tannat Wines- Different MLF-Before Aging Control (gray filled square), MLF with DSM 7008 (black filled square)and D-11 (open square) J. Agric. Food Chem. 2009, 57, 6271–6278. E. Boido, K Medina, L. Farina, F. Carrau, G. Versini, E. Dellacassa

  25. Timing of Inoculation

  26. Summary Reduction in acid Production of desirable compounds (diacetyl) Production of other flavor compounds during growth (1-hexanol, ethyl acetate, ethyl lactate, diethyl succinate, butyrolactone, glycoaldehyde, glyoxal, 2,3-butanediol, caprylic acid, hydroxycinnamic acid) Release of aglycones from glycosides in the wine

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