White Wine Making Flashcards
What is wine science
Viticulture and enology (wine science) explores every step of the winemaking process, from growing grapes in the vineyard (viticulture), to processing those grapes to make wine, to evaluating sensory components that make for excellent premium wines (enology).
What 5 main substances are present in an average white wine bottle (in %)
86.8% water
11.2% ethanol
1% trace components (sugar, vitamins ect)
0.5% volatiles (esters, ketones)
0.5% acids (mainly tartaric acid)
When should white grapes for white wine be harvested
Usually in the early morning when it’s still cool or when it’s harvested when it’s a bit warmer it should first be cooled and dried overnight.
Why is it important to harvest the grapes at the right time in the year?
For the purpose of the sugar content, as a decrease in sugars leads to a decrease in alcohol percentage.
How can too much rain impact the grapes’ quality
If there is to much precipitation, the sugar in the grapes will be diluted and that will cause a decrease in alcohol percentage.
What happens if the white grape berries are left on the vine for too long in extreme heat or is exposed to a lot of heat ?
The berries become softer and they break easily, exposing the juice to oxidation which will cause the juice to turn brown and will lower the quality of the wine as a whole.
How can we protect the berries from oxidation?
By using a product called Sulphur Dioxide.
What does SO2 do ?
It protects the berries from oxidation and from microbes. It is widely used as a preservative for the juice to prevent it from turning brown.
What does an increase in sugar of the berry cause ?
It causes an increase in ethanol
What are the main differences between machine harvesting and hand harvesting
MH: faster, efficient, cost effective for big farms, expensive machinery used, can damage grapes and overall quality of wines, can get to the cellar quicker
HH: time consuming, more cautious, minimal damage to berries, gets to cellar as a whole
Why will a bigger container for transportation lower the quality of the wine
A bigger container will place more pressure on the bottom grapes, this will cause the berries to burst open and expose the juice to oxidation which will make the juice brown and lower the quality of the wine
Why is it important to quality check the grapes
To determine if any adjustments will have to be made before fermentation and it determines the final price supplied to the grower
What happens when the grapes finally arrive at the cellar
The grapes are put through multiple quality parameters such to determine sugar concentration ,acidity, and the phenolic contents present. Then it is off loaded to be processed.
When the grapes are off-loaded into the stemmer crusher, what substance do they add to the grapes and what role does it play?
They add Nitrogen to minimize the contact of oxygen
Why is machine sorting better than hand sorting?
Hand sorting requires a lot of labour and with increased labour costs, it has become a expensive measure.
How does machine sorting work?
Fruit passes under a detecter which can be set to look out for many differences in berries like size and or colour. The intensity of the grapes’ colour is assessed by infrared spectrum detecters. Depending on the instructions set to look out for the computer decides whether the berry is up to standard or not, those that aren’t are rejected.
Why are most grapes not pressed with stems intact?
Stems contains tannins which is a substance that will make the wine bitter or astringent (acidic or bitter ) and it also makes the wine brown
What is the difference between crushing and pressing
Crushing: is the matter of bursting the skins so that all the in er solids can be exposed to the fermentation. It also produces free flow juice, which is juice which automatically flows from the burst open grapes.
Pressing: is the process that separates the grape juice from the fiber and other solids of the grape. It’s also to extract even more juice.
What happens during the process of crushing?
Crushing involves pressing berries against perforated wall (wall with holes) or passing it through a set of rollers moving towards each other. The spacing between the to rollers can be adjusted to accommodate different cultivars or any change in yearly produce. By adjusting the spacing you also prevent seed rupture which can influence the quality of the wine by contaminating the must with seed oils.
What is free run juice?
Free run juice is the juice that runs oit of the berries in the presser before the berries are even pressed. This juice often produces the huge quality white wines as it has no additional compounds released in the must because of the pressing process
Why is free run juice better than pressed juice?
Free run juice has lower levels of astringent phenolics which are compounds that cause high acidity, browning, bitterness and oxidation. All of these causes have a negative impact on the wine quality.
What happens during clarification?
Murky or turbid juice after pressing has to be made more clear, this can be done by a few processes
What is racking?
It is the siphoning of the clear juice after clarification
Why are enzymes rather used than cold settling for clarification?
Enzymes are more cost effective than coolers and they are more environmentally friendly
What are the different methods to exercise clarification?
- Cold settling: murky juice is left over night at a temperature of 15 degrees celsius or lower, it is left until particles in the juice settles to the bottom, then the clear juice on top can be pulled off into a new container
- Adding Pectolytic enzymes: these molecules bind to the particles making them heavier to settle to the bottom quicker.
- Centrifugation: method of seperating molecules with different densities by spinning them in solution around an acis at high speeds.
- Adding bentonite: bentonite is a clay, it is rehydrated and mixed into the must, it removes proteins that cause hazes. But it’s expensive and not environmentally friendly
- Filtration: a filter is used to remove unwanted particles (filter like activated carbon)
What is the optimal pH of white wine
3.1-3.4
Is white grapes preferable harvested at low or high sugar levels
Low sugar levels
How would you achieve a crispy fresher white wine?
A lower pH value would give you a crispier fresher wine and it would enhance the shelf life
Name a few de- acidification methods
(MLF) Malolactic fermentation: the conversion of malic acid to lactic acid leading to a reduction in acidity and the production of aroma and flavor compounds.
(KHT) Potassium bitartrate precipitation: tartaric acid is one of your main acids along with malic acid and lactic acid. So if you chill the wine then the potassium binds with the tartaric acid and forms the crystals. So you remove the crystals with (the acid) by racking the wine in another canister.
You can also add CaCO3
What are the 2 positive characteristics SO2 has that benefits a wine?
Its antiseptic against microbes and antioxidant to prevent oxidation
What are the 2 forms that are possible for SO2
Bound form and free form
Bf: binds to pigments and proteins to help stabilize flavors and pigments
Ff: active against microbes
What is the correlation between pH and effectiveness of SO2
Higher pH = lower effectiveness
Lower pH = higher effectiveness
Why is more SO2 needed in white wine than red wine
White wine shows more browning because it is a lighter color whereas red wine has a darker red color and it won’t show as much browning
Therefore white wine needs more SO2 to protect it against oxidation
How much SO2 is needed in white and red wine
210mg/L for white
160mg/L for red
How does skin contact work in white wines
Only happens in certain white wine makings, when some aromas associated with the skin should be present in the wine
Its done for less than 24h at low temperatures, 5-10 degrees Celsius
Add SO2 after skin contact
What are the aromas called that are situated in the skin of grape for the making of Gewürztraminer, Muscat cultivars and Sauvignon blanc?
Gew: methoxypyrazines
Sauv: terpenes
