Pulp winemaking 2 Flashcards
Q: What happens during the lag phase of fermentation?
A: Yeast acclimate to juice conditions; it typically lasts 1–2 days but can be longer in difficult musts.
Q: What are best practices for pitching yeast?
A: Use correct temperature and SO₂ levels; avoid cold juice; consider sacrificial cultures and peroxide if legal.
Q: What characterizes the growth phase in fermentation?
A: Rapid increase in yeast cell numbers; cells can bud every 1–4 hours; population doubles every few hours.
Q: What is the typical yeast population change during growth phase?
A: From 5 × 10⁶ to 0.5–1 × 10⁸ cells/mL.
Q: What are best practices during the yeast growth phase?
A: Add oxygen or air to build sterols, add nutrients, and slowly adjust temperature to ferment levels.
Q: What defines the stationary phase of yeast fermentation?
A: Rapid fermentation, high sugar consumption and peak ethanol production
Q: Best practices for the stationary phase of fermentation?
A: Maintain temperature, use oxygen/nutrient such as DAP if needed, anticipate slow/stuck ferms and consider agitating.
Q: What happens during the decline (death) phase of fermentation?
A: Nutrients are depleted, ethanol and toxins rise, yeast viability decreases and ferm slows.
Q: Best practices during the decline phase?
A: Increase temperature, keep yeast suspended (agitation), remove toxins with yeast hulls, treat h2s with copper/air
Q: What types of issues can cause fermentation to go wrong?
A: Chemical (e.g ethanol, nutrient), physicochemical (e.g., temp, oxygen), and biological (e.g., microbial competition) issues.
Q: What is fermentation monitoring and why is it important?
A: Monitoring the kinetics and health of fermentation to ensure successful progression and detect problems early.
Q: What are 4 common indicators used to monitor fermentation?
A: Sugar consumed, CO2 produced, alcohol formed and must density changes
Q: What tools are used to measure fermentation density?
A: Hydrometers (SG, Brix, Baume, Oechsle), with temperature correction and sample homogenization.
Q: Why must samples be homogenized before density measurement?
A: To get an accurate and representative reading of the fermenting must.
Q: Why do tank temperature readings often vary?
A: Tops of tanks are warmer; tank perimeters cooler; red wine caps can be especially hot.
Q: How can yeast numbers be monitored during fermentation?
A: Via direct (haemocytometer) and indirect (agar plates) enumeration.
Q: What does direct enumeration of yeast involve?
A: Counting with a haemocytometer; includes viable/non-viable cells, can use methylene blue to distinguish viability.
Q: What does indirect enumeration of yeast involve?
A: Culturing on agar plates to assess yeast numbers and types.
Q: What are some visual methods for estimating yeast concentration?
turbidimeter and spectrophotometers
Q: What does good ferment management aim to do?
A: Address and pre-empt chemical, physical, and biological problems to ensure healthy fermentation.
