Unit 2 sida 104-125 Flashcards
How much sugar g/l is needed to create 1% abv in wine?
around 16-18g/l
And 1% abv is how much sugar?
around 8g/l of alcohol - the rest of the sugar needed to create it becomes carbon dioxide gas.
Which one of fructose and glucose is the dominant sugar in the early ripening stage of the grape?
Glucose
Can fructose ever be the dominant sugar in the grape?
Yes, the riper the grape the more fructose is accumulated. Can be become dominant in late harvested grapes/botrytis
Is either glucose or fructose easier to ferment?
Yes, glucose is much easier than fructose - fructose rich musts can be hard to ferment to dryness.
what is the name of the compound created threw fermentation that adds to the weight/body of the wine?
Glycerol - slightly sweet and and adds smoothness/weight.
Why is stainless steel tanks one of the easiest vessels to ferment in?
- Easy to clean
* Can easily be temperature controlled and doesn’t retain heat.
What can be the drawbacks when using wooden fermentation vessels?
Cleaning and precise care of the wood is needed to make sure no yeast or bacteria thrive in the wood. It’s also harder to manage temperature since wood retain heat much more then steel tanks.
Besides wood and steel, cement fermentation vessels are becoming popular how so?
Relatively cheap to install and easy to clean - even oxygen exchange may occur on smaller vessels such as cement tanks. They are also quite resistant to temperature change.
What is the main yeast responsible for alcoholic fermentation after 4% regardless of wild or cultivated yeast?
Saccharomyces cerevisiae
Why are winemakers prone to get other indigenous yeast out of the way when it comes to start fermenting?
Other “wild” yeast may slow down the start up process of fermentation and lead to creation of off-flavours and microbiological spoilage.
Using an “active dry yeast” has numerous benefits, which are?
- rapid fermentation start
- Ability to ferment highly clarified juice
- More even fermentation rates and controllable
- No undesirable off-flavours
- efficient sugar to alcohol conversion
- Minimal risk of a “stuck ferment”
- Low VA production (acetic acid)
Is the level of SO2 tolerance the same between indigenous and cultivated yeast?
No, indigenous yeast have a much lower tolerance to SO2 rather than cultivated yeast.
When fermentation starts how does winemakers measure the rate of fermentation?
By checking the density of the liquid. Since alcohol has a lower density then water the decrease in density marks the start of fermentation. Fermentation if optimum should go evenly - a constant conversion rate rather then too fast at first and slow later on.
What are the benchmark temperatures for fermenting white wine and red wine?
For white wine -> 10-18°C
For red wine -> 20-32°C
Name three risks when fermentation vessels reach excessively high temperatures?
- Oxidation & microbiological spoilage
* Loss of aromas, flavour and even alcohol due to volatilisation
Name three risks when fermentation vessels reach excessively low temperatures?
- May lead to retention of isoamyl acetate (pear-drop/banana aromas)
- For red wines, poor extraction of colour and tannins
- Can cause sluggish or stuck ferments
- Can lead to production of ethyl acetate resulting in volatile aromas
is aeration prior to fermentation needed for white or red wine making?
Not for white wines, they receive enough of oxygen threw processing and pressing.
However for reds, yes, some aeration is needed at the start of fermentation to make sure the yeast multiplies. Either threw remontage or piegage. Reds have a higher resistant to oxygen exposure due to tannins and pigments.
How will you know when the fermentation is complete?
Daily checking the density and once it drops below one (basicly waters density) one can start measuring sugar levels. All dry wines will have sugar up to 2g/l which is unfermentable.
