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Effects of Inoculation Level During and After Fermentation

Effects of Inoculation Level During and After Fermentation. Student Team. Meredith Bell, Sarah Harper, Joanne Oh, Diego Roig and Luke Bohanan. Fermentation Analysis. Diego Roig. Goal of Study.

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Effects of Inoculation Level During and After Fermentation

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  1. Effects of Inoculation Level During and After Fermentation

  2. Student Team Meredith Bell, Sarah Harper, Joanne Oh, Diego Roig and Luke Bohanan

  3. Fermentation Analysis Diego Roig

  4. Goal of Study • To compare the effect of different levels of inoculation of active dry commercial yeast preparations on fermentation and sensory characteristics of wine • Used Chardonnay juice and Premiere cuvee

  5. 2010 UC Davis Chardonnay • Crushed and Pressed 9/2/10 • Healdsberg crusher destemmer • Bucher Vaslin Press • Juice held in cold storage news.ucdavis.edu

  6. 2010 UC Davis Chardonnay • Split into six, 10 gal drums • Inoculated 10/8/10 • Premier cuvee • 6 inoculation levels skolnik.com

  7. Inoculation Levels Chemistry of Juice: Brix: 25.25; pH3.66; TA 4.98 (g/L) NOPA: 56; Ammonia:132; YAN: 188

  8. Fermentation • Cold fermentation cellar • Brix and Temp taken twice daily • When Dry, moved to cold storage

  9. Rate of FermentationInoculation Level • Inoculation size directly effects the rate of fermentation • Larger initial biomass • Less time/energy spent on achieving maximum cell density (2 x 108 cells/mL) despite lower maximum growth rate

  10. Temperature • Temperature is important component of any fermentation. • Premier cuvee yeast has temp. range of 7-35°C • Chardonnay temps were b/w 12-18°C, with no irregular heat spikes

  11. Temperature • Highest temperatures throughout study seen in natural fermentation despite slowest rate of fermentation • Max. temp. (natural fermentation): 17.9°C • Max. temp. (inoculated fermentations): 17.2-17.3°C • Possible explanations • Heat generation during yeast budding • Different yeast strain dominating fermentation • Closer to warmer area of room (not likely)

  12. Date Blend ID % EtOH pH TA (g/L) VA (g/L) 11/15 1 14.9 3.82 5.78 0.40 11/15 2 14.7 3.82 6.07 0.44 11/15 3 14.9 3.83 5.71 0.44 11/15 4 15.7 3.82 5.79 0.33 11/15 5 15.4 3.73 6.23 0.27 11/15 6 14.9 3.72 6.68 0.35 Lab Analysis of the Finished Wine

  13. 1 2 3 4 5 6 10/29 2-3% 1-1.5% 1-1.5% Trace Trace - Neg Neg 11/5 2% 1% 0.5% Trace Neg Neg 11/12 Trace 0.5-1% 0.5-1% Trace Neg Neg Results of the Residual Sugar Testing

  14. Chemical AnalysisEthanol Inhibition • Inoculation levels shown to increase EtOH tolerance • Current study confirms previous findings. • Slower rates of fermentation at lower inoculation levels possibly due to decreased EtOH tolerance of yeast

  15. Chemical AnalysisVolatile Acidity • Lower VA measurements at higher inoculation levels • Acetobacter repressed in absence of oxygen • Lower VA measurements correlated to shorter lag phase? • Different strains of S. cerevisiae produce varying amounts of acetic acid • May explain lower measurement in Lot 1

  16. Chemical AnalysispH/Titratable Acidity • Malolactic fermentation results in increase in pH and decrease in TA • Slower fermentations saw pH increase and decrease in TA • Possible that ML fermentation began? • Colder temps inhibit ML, Lots 5/6 moved to cold room 2 weeks sooner than rest of Lots

  17. Sensory Analysis Luke Bohanan

  18. Sensory Evaluation • Acceptance test with hedonic scale • Aroma only • 2 Repetitions all wines • Randomly numbered • Randomly ordered • Judge tracking

  19. Mean Preference Scores • Reasonable Variance • Two Distinct groups • Outliers…

  20. ANOVA • XLSTAT used • Judges H0 rejected = Not all Judges scored the same • Wines H0 rejected = Not all wines were scored the same • Reps H0 accepted = No significant difference between reps

  21. Judge Grouping From LS Mean

  22. Wine Grouping from LS Mean

  23. Preference Mapping • Judges in tight group compared to wines • Drastic difference in wine grouping

  24. Mean Factor Score from PCA • Wines 5 and 6 are disliked • Wines 1-4 are liked • Wine 4 is liked the most

  25. What does sensory tell us? • Highest concentration of desired aroma compounds at 106 cells/ml • Higher concentration of undesirable compounds at 107 cell/ml and above • Concentrations below 106 cells/ml show acceptable levels of desirable aromas

  26. Possible causes of negative aromas • Treatment 5 and 6 left on mass of lees = reductive environment = sulfur • Lack of nutrients • Post fermentation contamination • Headspace post fermentation = O2 Exposure

  27. Questions?

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