Fermentation

Question 1

Describe the basic reaction of fermentation

Answer 1

Sugar +yeast -> heat + CO2 + ethanol

Question 2

What is the Latin name of the most common strain of yeast used

Answer 2

Saccharomyces cerevisiae

Question 3

Give two examples of wild yeast

Answer 3

Candida

Kloeckera

Question 4

What are the benefits of saccharomyces cerevisiae? Cons?

Answer 4

Consistent
Reliable 
Tolerant to alcohol 
Resistant to SO2 
Good with high acid 
Fast fermentation 

Cons:
There is a cost to is as it’s not natural / ambient
Lack of uniqueness

Question 5

Explain some of the pros and cons of wild yeast

Answer 5

Pros
Interesting complex flavour 
Natural
Good marketing hook
Free 
Suitable for BD winemaking 

Cons
Inconsistent 
Dies at 5% ABV
Gets stuck 
Slow fermentation

Question 6

What does the fermentation create in the must

Answer 6

• flavours from precursors
• heat
• CO2
• Small amount of SO2 (10mg/L)
• ethanol
• volatile acidity
• fermentation aromas (esthers)
• glycerol

Question 7

How do you avoid other natural yeasts starting to ferment?

Answer 7

• cool the must

- add SO2

Question 8

What’s the benefit of a faster fermentation

Answer 8

• minimises risk of spoilage from oxygens and micro organisms

Question 9

Name three materials used for fermentation

Answer 9

• innox
• wood
• concrete
• plastic

Question 10

What are the benefits of concrete

Answer 10

• inert
• ## eggs thought to stimulate convection currents

Question 11

Pros and cons of fermentation in wood

Answer 11

Pros

• allows o2 in
• expensive up front but lasts for ages
• retains heat well
• can come in range of sizes (course is 4500L)
• flavours of wood imparted to wine

Cons

• allows o2 in
• large upfront cost
• Not suitable for reds as cap management required
• difficult to clean
• flavours of wood imparted to wine

Question 12

Pros and cons of fermenting in stainless steel

Answer 12

Pros

• cheaper than wood
• easy to clean
• Good temperature control
• no o2 coming in
• no flavours coming from material

Cons

• no flavours imparted
• can be expensive all the same

Question 13

What temperature is too hot gmfor fermentation- what happens that will stop fermentation at that point

Answer 13

35c. After that the yeast dies.

Question 14

When does controlled MLF take place

Answer 14

After alcoholic fermentation usually

Although it can be done during alcoholic fermentation which saves time and can help preserve fruit flavours

Question 15

What is the ideal temperature range and pH range for MLF?

Answer 15

18-22c

3.3-3.5pH

Question 16

How to avoid MLF?

Answer 16

• temp control (lower than 15c)
• SO2
• pH below 3.3
• addition of Lysozyne (enzyme that kills lactic bacteria)
• filtration
• hygiene

Question 17

What are the results of MLF?

Answer 17

Lower acidity 
Smoother texture
Less bright colour
Less instability 
Less fruit but more buttery flavours 
More volatile acidity

Question 18

Which wines would benefit from MLF?

Answer 18

Wines with naturally high acidity levels like Chablis

Question 19

Which other process Can take place at the same time as MLF, other than alcoholic fermentation

Answer 19

Less stirring
When MLF takes places in barrels, the two processes can be done simultaneously
It’s a good way of integrating the flavours but requires a lot of management as the barrels will need to have their temperature monitored individually