Fermentation Flashcards
Describe the basic reaction of fermentation
Sugar +yeast -> heat + CO2 + ethanol
What is the Latin name of the most common strain of yeast used
Saccharomyces cerevisiae
Give two examples of wild yeast
Candida
Kloeckera
What are the benefits of saccharomyces cerevisiae? Cons?
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
Explain some of the pros and cons of wild yeast
Pros Interesting complex flavour Natural Good marketing hook Free Suitable for BD winemaking
Cons Inconsistent Dies at 5% ABV Gets stuck Slow fermentation
What does the fermentation create in the must
- flavours from precursors
- heat
- CO2
- Small amount of SO2 (10mg/L)
- ethanol
- volatile acidity
- fermentation aromas (esthers)
- glycerol
How do you avoid other natural yeasts starting to ferment?
- cool the must
- add SO2
What’s the benefit of a faster fermentation
- minimises risk of spoilage from oxygens and micro organisms
Name three materials used for fermentation
- innox
- wood
- concrete
- plastic
What are the benefits of concrete
- inert
- ## eggs thought to stimulate convection currents
Pros and cons of fermentation in wood
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
Pros and cons of fermenting in stainless steel
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
What temperature is too hot gmfor fermentation- what happens that will stop fermentation at that point
35c. After that the yeast dies.
When does controlled MLF take place
After alcoholic fermentation usually
Although it can be done during alcoholic fermentation which saves time and can help preserve fruit flavours
What is the ideal temperature range and pH range for MLF?
18-22c
3.3-3.5pH
How to avoid MLF?
- temp control (lower than 15c)
- SO2
- pH below 3.3
- addition of Lysozyne (enzyme that kills lactic bacteria)
- filtration
- hygiene
What are the results of MLF?
Lower acidity Smoother texture Less bright colour Less instability Less fruit but more buttery flavours More volatile acidity
Which wines would benefit from MLF?
Wines with naturally high acidity levels like Chablis
Which other process Can take place at the same time as MLF, other than alcoholic fermentation
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
