Fermentations

Question 1

Alcholic Fermentation

Answer 1

Is the conversation of sugar into alchol and CO2 through the action of yeast.
The other by-products of this process are heat and flavour compounds.

The yeast responsible of the fermentation is Saccharomyces cerevisiae, due to ita tolerance of high levels of alcohol and SO2.

Alcoholic fermentation will not start if the temperature is below 5 *C and should continue natr until all the sugar has been consumed.

Alchoholic fermentation may stop when the temperature reaches over 35 *C.

Yeast can be killed by adding SO2 or by adding grape spirit.

Yeast can be removed using filtration after fermentation.

Question 2

The two important ways in which a winemaker can control the fermentation are:

Answer 2

The choise of Yeast

Temperature Management

Question 3

Yeast

Answer 3

The winemaker can choose between ambient yeast found on the grape skins and in the winery that increase the complexity of flavours but in this case the winemaker cannot control exactly which yeasts are present, or the cultured yeast that limits the potential complexity of the wine.

Question 4

Malolactic Conversion

Answer 4

Usually takes place once the alcoholic fermentation has finished and carried out by lactic acid bacteria by raising the temperature of the wine and by not adding SO2.
They convert the tart malic grape acid into the softer lactic acids.
Malolactic conversion softens and reduces acidity, as well as creating buttery flavours and producing CO2.

It can be avoided through storage at cool temperatures, the use of SO2, or by filtering out the bacteria.