Vinification Flashcards
Primary flavors in wine come from: the grapes, fermentation, or age?
Grapes themselves
What sugar does yeast prefer to consume?
Glucose
What is the conversion ratio used to estimate potential alcohol in the EU?
16.83 grams per litre of sugar in the must yields 1% abv
Yeasts convert roughly what % of sugar into alcohol?
90-95%
What is the main acid in grapes, are there others?
Tartaric
Yes, Malic & Citric
How do pH and TA differ in the perception of a wine?
pH affects texture
TA affects how “sour” a wine will be
What are the three categories of Phenolic compounds?
Flavonoids (polyphenols like Anthocyanins and Catechins)
Non-Flavonoids
Tannins
Which method of white wine pressing yields a higher degree of skin contact: destemming before pressing or whole-cluster pressing?
Destemming before pressing
In what style of winemaking is whole cluster pressing generally favorable?
Sparkling wine production
When does extraction begin in red winemaking?
As soon as berries are crushed
Are whole cluster fermentations warmer or cooler than destemmed fermentations?
Cooler - stems provide channels for airflow
What style of red winemaking is semi-carbonic?
Whole cluster
At what % of alcohol does intracellular fermentation generally stop?
2%
What are Pectolytic enzymes?
Enzymes that break down pectin in grape skins, used to increase extraction in a short period of time
What are the three methods of rose production ?
Direct press
Saignee
Blending
What is cold soaking?
Process where red must is held at a cool temperature to inhibit fermentation
Fruit enzymes break down skins to increase color
Are thermoinification and flash detente used in quality winemaking?
No
At what point does extraction end?
Pressing
What is the press cut?
When a winemaker decides when to switch from a light press to heavy press juice
What method of pressing is preferred for quality winemaking: Batch pressing or Continuous pressing?
Batch pressing
What is debourbage?
Settling of must overnight at a cold temperature then racking off sediment - done post pressing
When is Bentonite clay added to a wine to clarify it? How does it work?
After pressing before racking
Natural electrostatic processes (positively charged connects to negatively charged ions in the juice)
How might alcohol be adjusted in the winemaking process?
If potential alcohol is too high adding water to the must in tank BEFORE fermentation
During the process of Malolactic fermentation, what does Citric acid turn into?
Diacetyl
Does MLF increase or decrease a wines total acidity?
Decrease
What is the name of the main wine yeast?
Saccharomyces cervisiae
What is the name of the LAB that causes MLF?
Oenococcus oeni
Non-saccharomyces yeasts generally die off after what point in the winemaking process?
Just after fermentation begins
Botrytis is likely to carry what genus of Yeast? What does this yeast produce a lot of?
Pichia yeasts
It’s a spoilage yeast that produces a high amount of VA
What yeast strain produces a higher proportion of ethyl acetate?
Kloeckera apiculata - a cold tolerant yeast
Is Brettanomyces bruxellensis an alcohol tolerant yeast variety or not?
It is very alcohol tolerant
LAB converts glucose into what?
Lactic acid
What are biogenic amines and what causes them?
Off-putting aromas of putrescine and cadaverine
Caused by undesired LAB species
What are pyridines and what causes them?
Aromas of mousiness, flavors of acrolein (bitter), and causes ropiness
caused by undesired LAB species
What is ropiness in wine?
It’s a viscous slime that forms from polysaccharides linking together
What is the species of Acetic acid bacteria that can live in wine?
Acetobacter
What causes populations of acetobacter to rise?
Exposure to oxygen post fermentation
Can be managed by topping up barrels and also with SO2 during aging
Roughly how much C02 is produced in relation to volume of the must ?
CO2 is 60x greater than the volume of the must
Is fermentation a reductive or oxidative environment?
Reductive - CO2 displaces oxygen
How many yeast cells per milliliter are generally required for fermentation to begin?
Roughly 10 million cells
What are the three stages for yeast during fermentation?
Lag phase - yeast adapting to environment
Exponential phase - reproduction
Stationary phase - the act of fermentation
If nitrogen is too low during a fermentation what aroma can be produced? How does this actually affect the act of fermentation?
Hydrogen Sulfide (rotten eggs)
Can lead to a stuck fermentation
What are mercaptans? What are they derived from?
Bad smelling thiols (skunk, onion, rubber)
Created when hydrogen sulfide is produced and reacts w/ the wine to create other compounds
What is the temperature range that yeasts generally are able to operate within?
45-95 degrees Fahrenheit
What temperature range are yeasts most active in?
70-80 degrees Fahrenheit
What is the process of Remontage?
Pump overs
What is the process of Pigeage?
Punch downs
During Remontage what is the use of the “sprinkler” vs. “fire hose” technique?
Sprinkler will be less extractive
Fire hose is much more extraction
What is Delestage?
Rack and return
Removes the must to another tank w/ skins left behind then pumping the must back over the skins to mix thoroughly
Where is Submerged Cap fermentation historically popular?
Piemonte
Besides Lactic acid, what other compounds are created during MLF?
Acetic acid
Acetaldehyde
Diacetyl
Where was the technique of microoxygenation popularized?
Madrian in the 1990’s
What does microoxygenation try and mimic?
Aging in a porous vessel like oak
What wine fault is risked when microoxygenation is used?
Prem-ox
What is cliquage?
A technique that mimics the oxidative effects of racking with one large hit of O2
Are the following forests know for having tight grain, medium grain, or coarse grained oak:
Troncais
Allier
Jupilles
Nevers
Bertranges
Vosges
Limousin
Zemplen Hills (Hungary)
Troncais - Tight
Allier -Tight
Jupilles - Tight
Nevers - Medium
Bertranges - medium
Vosges - loose
Limousin - Coarse
Zemplen Hills - tight
If wines use 100% new oak how does the price increase per bottle (French and American)
French: $3.30-$7.50 / bottle
American: $1.65 + /bottle
What is the humidity range where alcohol and water evaporate at the same rate? If lower/higher, what happens to the wine?
70%
If lower - alcohol increases as water evaporates w/o the alcohol
If higher - alcohol decreases
What is the process of Ouillage? How often is it practiced?
Topping up of barrels
Every 2-6 weeks
May USDA certified organic wine contain added sulfites?
No
May USDA certified wine made from organic grapes contain added sulfites?
Yes up to 100ppm of SO2
When might SO2 be added to a wine?
Before fermentation to inhibit bad bacteria or undesirable yeast
During fermentation (stopping it)
After MLF to prevent oxidation
At bottling to inhibit oxidation that naturally happens during bottling
What is the French term for racking?
Soutirage
What is protective racking?
An anaerobic way to rack a wine pushing wine from a barrel using inert gasses
What is the tool that is used to rack a wine?
A racking wand or racking arm
How can mercaptans be removed from a final wine?
Using copper sulfate - reacts w/ insoluble compounds that fall out of solution
What are the legal limits of Copper sulfate use in the US and EU?
.5mg/L in the US
1mg/L in the EU
What is copper casse?
Excess copper in a wine that increases rate of oxidation and can cause haziness or a reddish/brown particulate in white wine
