Vinification Flashcards
Define vinification
transformation of grape juice into wine
Why is SO2 added to fermenting must or juice beforhand
- prevents oxidation and bacterial contamination
- ensures rapid fermentation
What chemical is a sign of oxidation in finished wines?
Acetaldehyde
What is acetaldehyde converted to in new wine and what happens when that compound reacts with alcohol?
- Acetaldehyde is converted to acetic acid
- acetic acid reacts with alcohol = ethyl alcohol
- ethyl alcohol is volatile acidity
When VA is present as a fault, what happened?
Excess of acetic acid produced by activity of acetobacter (same bacteria that makes wine into vinegar in presence of oxygen)
What does low Nitrogen levels in must lead to?
-formation of Hydrogen Sulfide H2S (rotten egg smell)
bc yeast needs N to work
What are sulfites vs sulfides in winemaking terms?
- sulfites - SO2
- sulfides - H2S, mercaptans(thiols), and other foul smelling compounds produced under reductive conditions
Would you use small or large vessel if you want a short, hot fermentation?
large
What temp range is yeast active?
50-113*F
What temp can red wine fermentation reach
90s
-about 95 can risk volatized flavor compounds and stuck fermentations
What is benefit of hot fermentation for red wine?
increased extraction of color, tannin, and flavor compounds
How long is range for fermentation depending on yeast used?
a week to a month to ferment dry
Ways to remove alcohol from wine?
- spinning cone - modern (centrifuge)
- reverse osmosis
Two constituents of reverse osmosis?
permeate --- contains water and ethanol --- distilled to proper level before recombined retentrate --- wines aromatic compounds
Is de-alcoholization by physical separation legal in EU? How much can it be adjusted
Yes, as of 2009
-cant be adjusted by more than 2%
Two main acids used for acidification? Which is preferred, when?
Tartaric and malic acid
Tartaric acid added prior to fermentation is preferred
Compound responsible for butter aromas in wine? Result of?
Diacetyl
-results of Malo
What environment required for Carbonic Maceration?
Anaerobic - No oxygen!
-happens under blanket of CO2 in tank
What is MOG
Materials Other than Grapes
-removed during sorting
Name of machine used to crush grapes?
Crusher-destemmer
What is cold soak?
- pre-fermentation maceration technique
- relies on substantial SO2 additions and cold temp
- maybe up to a week
Are grape skins included in fermentation for red wines?
Yes
- fermentation and maceration occur in tandem
- want to extract phenols like tannin, color, anthocyanin, flavor with help of heat and alcohol
What is the chapeau?
Cap
Cap management techniques
Pigeage - punch down
Remontage - pump over
Délestage - fully drain off into separate vessel, then pour over
What is vin de goutte
high quality free run wine drained first from tank
What is result of pressing pomace
vin de presse - coarser, more tannic
basket press vs pneumatic bladder?
basket press - vertical pressure
pneumatic bladder - gentle pressure via inflation with air
what is élevage?
maturation period
what is racking? what is french word? what is point?
- soutirage
- movement of wine from one vessel to another
- provides aeration and clarification, removes wine from lees/sediment
When does ML fermentation occur in red wine?
quickly at end of fermentation or slowly during maturation
When is SO2 often added for red wine?
during maturation or just before bottling
When is wine fined/filtered?
prior to bottling, after being racked a final time
What is french word for fining? Benefits of fining and filtering?
- collage (fining)
- filtration promotes stability
- fining and filtering promote clarity
Common fininf agents
- bentonite (clay from volcanic ash)
- casein (milk protein)
- egg white
- isinglass (sturgeon bladder)
- gelatin
- egg whites
What is french word for letting juice settle? What is purpose?
Débourbage
-juice can be racked off solids and clarified before fermentation
What is cold filtration for in white wine production?
-causes tartrate crystals to precipitate out at 25*F
Why are off-dry and sweet white wines often filtered?
-sugar content can lead to unexpected refermentation in bottle!
4 methods of rose winemaking
- blending
- limited skin maceration
- direct press
- saignée
Is blending allowed in EU for rose?
- PROHIBITED but only below PGI!
- Most appellations preclude it, but Champagne obv allows it
Describe limited skin maceration for rose?
- red grapes subjected to short period of skin contact BEFORE fermentation
- can be several hours to several days
Describe Saignée
- bleed juice from maceration
- create rose as byproduct of red wine fermentation
- concentrates must for red wine
Describe direct press
- don’t crush grapes at all
- super pale hue
- direct pressing of whole red grapes or clusters
What does New oak contribute to wine?
- flavor - lactones, phenolic aldehydes like vanillin
- wood tannin
When does oak barrel become neutral?
4th-6th year of use
-most of flavor transmitted during 1st year
Two techniques that can be implemented to approximate effects of new barrel at fraction of cost
-micro-oxygenation (micobullage)
+
-oak chips
Species for French and American oak? Difference in grain?
French - Quercus robur, Quercus petraea
—tight wood grain, bc of slow growth
American - Quercus alba
—wider grain, bc grow faster
Why is French oak split and American sawn?
- French is split (provides fewer staves) bc it prevents leakage
- American is sawn bc it is less porous (has more Tylose) so no fear of leakage - releases more vanillin and lactones (coconut)
Difference in drying btwn French/American oak?
French oak is air dried - gentle process, leaches out som aggressive tannin and flavor
American oak - kiln dried - fast, concentrates lactones
3 stages of making barrel?
- warming (chauffage)
- shaping (cintrage)
- toasting (bousinage)
What is bousinage
toasting inside of barrel
What level of toasting leads to most extraction of wood tannin?
light
What is Foulage
old act of stomping grapes with feet
