Pulp Fermentation Management (L2,3)

Question 1

What is the primary yeast used in winemaking that is characterized by higher tolerance levels?

Answer 1

Saccharomyces cerevisiae

Saccharomyces cerevisiae is known for its higher alcohol/sugar tolerance, SO2 tolerance, pH/acid tolerance, temperature tolerance, and ability to produce ethanol efficiently.

Question 2

What are the key characteristics of non-Saccharomyces yeasts?

Answer 2

Generally less alcohol/sugar/SO2 tolerant, aerobic, and potentially producing organoleptically defective wines with high volatile acidity (VA) and ethanal

Non-Saccharomyces yeasts are unable to ferment to wine alcohol levels.

Question 3

What positive contributions can non-Saccharomyces yeasts make to winemaking?

Answer 3

Contribute to the complexity of the wine

While less robust, non-Saccharomyces yeasts can enhance wine complexity.

Question 4

What can non-Saccharomyces yeasts influence in Saccharomyces cerevisiae?

Answer 4

Metabolism through competition, provision of substrates, removal of substrates, and release of enzymes and bioactive proteins

They can bring both synergy and complication to winemaking.

Question 5

What are the five key stages of fermentation?

Answer 5

• Preparing Yeast
• Lag
• Growth
• Stationary
• Decline

Each stage has better and worse practices that can impact fermentation outcomes.

Question 6

What is one advantage of direct inoculation in fermentation?

Answer 6

Easy to implement

However, it can be expensive.

Question 7

What is the benefit of direct inoculation with acclimatisation?

Answer 7

Reduces lag phase and improves viability

This method helps yeast adapt better to the fermentation conditions.

Question 8

What is a potential issue with hydration during yeast inoculation?

Answer 8

Wrong hydration temperature

Other issues include using yeast too early/late and allowing starvation.

Question 9

What does the term ‘pied de cuve’ refer to in winemaking?

Answer 9

Picking early to produce a starter

This method helps in initiating fermentation with a healthy yeast population.

Question 10

True or False: Non-inoculated fermentation is risk-free.

Answer 10

False

Non-inoculated fermentation can be riskier but may contribute to wine complexity.

Question 11

What should winemakers understand about different yeast strains?

Answer 11

Specific characteristics of both Saccharomyces and non-Saccharomyces

This understanding aids in informed decisions about inoculation and fermentation management.

Question 12

Fill in the blank: Regular _______ is crucial to identify and address potential problems in fermentation.

Answer 12

monitoring

Close monitoring helps in managing fermentation effectively.

Question 13

What is a method that involves the intentional/unintentional transfer of ferment?

Answer 13

Cross-seeding

This method can influence the yeast population in fermentation.

Question 14

What is a key takeaway regarding inoculation methods?

Answer 14

Careful consideration should be given to inoculation methods and proper yeast hydration

Minimizing stress factors is also essential for successful fermentation.

Question 15

What are the four distinct phases in yeast growth during fermentation?

Answer 15

• Lag Phase
• Growth (Exponential) Phase
• Stationary Phase
• Decline Phase

Each phase has specific characteristics and key actions for effective fermentation management.

Question 16

What occurs during the Lag Phase of yeast growth?

Answer 16

Acclimatisation period lasting 1-2 days where yeast adjusts to juice conditions

Key actions include ensuring correct temperature and SO2 levels.

Question 17

What characterises the Growth (Exponential) Phase?

Answer 17

Rapid increase in cell numbers with cells budding every 1-4 hours

Population doubles every few hours, from 5 x 10^6 to 0.5-1 x 10^8.

Question 18

What are key actions during the Growth (Exponential) Phase?

Answer 18

• Addition of oxygen/air for sterol production
• Nutrient addition
• Slow temperature adjustments

These actions improve yeast performance.

Question 19

What happens in the Stationary Phase?

Answer 19

Highest levels of sugar consumption and ethanol production

Rapid fermentation rates are observed during this phase.

Question 20

What key actions should be taken during the Stationary Phase?

Answer 20

• Maintain ferment temperatures
• Rectify nutrient deficiencies
• Consider agitation

These actions help sustain fermentation activity.

Question 21

What occurs during the Decline Phase?

Answer 21

Nutrient levels decrease and toxin levels increase, reducing yeast viability

This phase leads to slower fermentation rates.

Question 22

What are key actions to manage the Decline Phase?

Answer 22

• Allow temperature to increase
• Keep yeast suspended through agitation
• Remove toxins

Combat H2S formation with aeration or copper sulphate/citrate.

Question 23

What is a crucial best practice for yeast management regarding temperature?

Answer 23

Ensuring optimal temperatures for each growth phase

Cold settling temps and tank temperature variations can affect yeast acclimatisation.

Question 24

What is the importance of SO2 management in fermentation?

Answer 24

Using the correct amount of SO2 initially to prevent issues

Potential use of peroxide or sacrificial cultures if legal.

Question 25

What role does oxygen/aeration play in fermentation?

Answer 25

Supports sterol production and ethanol tolerance during growth and stationary phases ## Footnote Important for yeast health and activity.

Question 26

Why is nutrient addition important during fermentation?

Answer 26

To support yeast activity during growth and stationary phases ## Footnote Nutrient deficiencies can hinder fermentation.

Question 27

What does agitation achieve during fermentation?

Answer 27

Keeps yeast suspended, particularly during the decline phase ## Footnote It may also be beneficial during the stationary phase.

Question 28

How can toxins be managed during fermentation?

Answer 28

Addressing the accumulation of toxins, especially ethanol, through absorption onto yeast hulls ## Footnote This helps maintain yeast viability.

Question 29

What are the main areas of potential problems affecting fermentation?

Answer 29

* Physiochemical * Chemical * Biological ## Footnote Each area presents specific challenges to successful fermentation.

Question 30

What physiochemical issues can affect fermentation?

Answer 30

* Osmotic pressure * Oxygen levels * Temperature fluctuations * Juice clarity ## Footnote These factors can hinder yeast activity and fermentation efficiency.

Question 31

What chemical issues can impact fermentation?

Answer 31

* Nutrient deficiencies * Excessive ethanol * Presence of inhibitory chemicals ## Footnote These issues can inhibit yeast performance.

Question 32

What biological problems may arise during fermentation?

Answer 32

Micro-organism competition, especially in spontaneous fermentation ## Footnote This can lead to fermentation failure or off-flavors.

Question 33

What is the goal of good ferment management?

Answer 33

To address or pre-empt potential fermentation problems ## Footnote Ensures a healthy and efficient fermentation process.

Question 34

What measurements are essential for fermentation monitoring?

Answer 34

* Sugar Consumption * Carbon Dioxide Production * Alcohol Formation * Density Change * Yeast Numbers ## Footnote These metrics assess the health and activity of the fermentation.

Question 35

What is the significance of monitoring sugar consumption in fermentation?

Answer 35

Tracks the amount of sugar being consumed, indicating fermentation progress ## Footnote Essential for understanding yeast performance.

Question 36

How is density change monitored during fermentation?

Answer 36

Using hydrometers to measure specific gravity, Oechsle, Baume, Brix, Babo ## Footnote Requires temperature correction for accuracy.

Question 37

What is direct enumeration in yeast monitoring?

Answer 37

Counting yeast cells via haemocytometer, including viable and non-viable cells ## Footnote Methylene blue staining can be used for viable cell counts.

Question 38

What is indirect enumeration in yeast monitoring?

Answer 38

* Using agar plates * Visual estimation * Turbidimeter/spectrophotometer use * McFarland broths estimation ## Footnote These methods provide estimates of yeast populations.