Vinification Flashcards
how is potential alcohol measured?
every 16.83 g/l of sugar in the must = 1% potential alcohol
but actual conversion ratio depends on efficiency of the yeast and typically ranges from 16.5 to 17.5- and between 5-10% of the sugar is not not able to be converted to alcohol
1 KMW is equivalent to approximately how many degrees Öechsle?
5
What does the Öechsle scale measure?
On the Oechsle scale, one degree Oechsle (°Oe) corresponds to one gram of the difference between the mass of one litre of must at 20 °C and 1 kg (the mass of 1 litre of water)
1 L of must weighing 1036 grams = 36 degrees Oechsle
What does Baume measure?
a specific gravity measurement. compares must weight to water with dissolved salt
juice at 14 degrees Baumé is likely to have a final alcohol concentration of about 14%. Baumé is converted to Brix by multiplying by a factor of 1.8.
What does Brix measure?
a speciic gravity measurement. compares must weight to water with dissolved sucralose. measures all dissolved solids, so it slightly overstates sugar proportion
1 degree Brix is equivalent to 1% sucrose by weigh
TA
titratable acid - determines perception of sourness—wine with a high titratable acidity (TA) tastes more sour.
during ripening, TA goes down, and pH goes up
wine pH
most wine is 3-4 pH
water is 7
during ripening, TA goes down, and pH goes up
catechins
small polyphenols that are extracted mostly from seeds and stems (though also from skins) and are largely responsible for bitterness in wine. While the concentration of catechin in wine is low, they are significant in wine as they are a major constituent of tannin.
anthocyanins and acid
Anthocyanin’s color is pH dependent, appearing redder at low pH (more acidic) and more purple at higher pH (less acidic)
when are the main phenolics extracted?
Anthocyanins extract rapidly at the beginning of fermentation. Tannins and catechins are more soluble in alcohol than water, so their rate of extraction is faster toward the end of fermentation
primary acid that occurs naturally in grapes?
Tartaric acid
degrees brix at harvest?
physiological ripeness
maturity of color, tannins, and flavors
physical signs it’s time to harvest
Seeds turn from green to brown and become crunchy. As the berries ripen, pulp separates from seeds more easily, the fruit seems juicier, and skins become softer and chewier. Berries soften and become susceptible to dehydration. The stems lignify, turning from green to brown, and berries become easier to remove.
foulage
crushing
maceration a froid
cold soaking. Red grape must is held at low temperature (close to 0ºC) prior to fermentation, typically for 2 to 10 days. fruit enzymes break down the grape skins, beginning the extraction process, Believed by some to enhance color extraction.
égrappage, éraflage
de-stemming
égouttage, écoulage
draining. Removing the wine from the fermentation tank, leaving skins and seeds behind. Often occurs just after primary fermentation.
collage
fining. The addition of a fining agent that selectively removes astringency, bitterness, proteins, or reductive aromas from the wine.
levurage
inoculation
levures = yeast
microbullage
or micro-oxygenation. adds small amounts of oxygen to wine post fermentation to accelerate maturation
Species of lactic acid bacteria preferred to complete malolactic fermentation?
Oenococcus oeni
LAB produce wine aroma and flavor compounds, including acetic acid, acetaldehyde, diacetyl, and others
gène
marc / pomace- skins and seeds left after pressing
remontage
pumpover
pigéage
punchdown
déléstage
rack and return
soutirage
racking
which yeast is responsible for alcoholic fermentation in wine?
Saccharomyces cerevisiae
échantillage
sampling from barrel or tank
ouillage
topping- Filling barrels to replace wine lost through evaporation during barrel aging. Typically done every two to four weeks.
décuvage
tank digoug. After a tank has been drained, the remaining solids are transferred to the press
bouchon
cork
béton
concrete
brouillard
fog
chapeau
cap
chai
cellar
corps étrangers
MOG
cuivre
copper
grappe entière
whole cluster fermentation
Saccharomyces bayanus
Found on winery surfaces and in small numbers on grapes
Fermentative yeast
Alcohol and SO2 tolerant
Fructophilic (metabolizes 5-carbon sugars)
Used to restart fermentations
semi-carbonic maceration
just some bunches are left whole- Juice in the bottom of the tank begins fermenting traditionally and produces carbon dioxide that induces carbonic maceration inside the intact clusters. The clusters may be broken down through cap management or foot-treading throughout the fermentation
effects of stem inclusion
Stems increase the concentration of phenolic compounds (especially catechins) and potassium. When stems are included, the resulting wine is often lighter colored and more tannic, with a higher pH and lower alcohol
rose- direct press vs maceration
direct press- whole red grape clusters are pressed, juice is treated like white wine
maceration or saignee- juice has a short period of skin contact. generally a byproduct of red winemaking, meant to concentrate the must. this juice is usually sweeter and less acidic than juice from grapes harvested for rose specifically
why use thermovinification?
if botrytis is present- the quick exposure to heat can denature laccase, prevent premature oxidation. can also help with smoke taint and an excess of pyrazines.
flash détente can also accomplish this
thermovinification vs flash détente
In thermovinification: must heated to 140 to 180F for 30 min - 24 hr, with higher temperatures requiring less time. The must is often pressed directly after heating, and fermentation proceeds off of skins.
With flash détente, grape must is heated rapidly to near-boiling temperatures (185 degrees Fahrenheit), then cooled rapidly using a vacuum. results in complete destruction of the berries on a cellular level—it resembles jam. The treated must is usually settled overnight, drained, and pressed, and fermentation takes place off of the skins.
The wine produced using these techniques is fruity and accessible, with jammy flavors. Very little tannin is extracted with either method, and tannin is systematically added prior to or after heat treatment.
free run
juice liberated without the application of pressure. liquid drawn off the must prior to pressing
note- most of red wine is free run, press wine represents around 20% of the total volume
two main categories of wine press
batch (i.e. basket, pneumatic)
continuous
basket press
Pressure is applied to the lid, and the grapes are compressed slowly, releasing juice. Today, basket presses are used more often for reds than whites, since the pressure applied is uneven and results in low yields when used on unfermented berries
pneumatic press types
A bladder press has an inflatable cylindrical bladder in the center of the press that expands radially, compressing the grapes symmetrically against the tank’s sides.
A membrane press is similar, but the inflatable bladder is located along one side of the tank and grapes are compressed against the other side.
A tank press is a fully enclosed membrane press that allows the winemaker to exclude oxygen for very reductive winemaking. This may be preferred for bright and clean white wine styles with delicate aromas, like popular styles of Sauvignon Blanc
methods of clarifying juice after pressing
- débourbage
- floatation- gas pumped into juice so solids float to top
- bentonite clay added- it attracts proteins through electrostatic forces, does not dissolve, is removed in racking
must adjustments- potential alcohol
grapes not ripe enough: chaptalization with sugar, adding rectified grape must
too ripe: diluting with water- before or after fermentation, irrigation right before harvest
must adjustments - acidity
not enough acid- tartaric acid can be added- it doesn’t break down during fermentation. malic and citric can also be used
too much- deacidification. several methods involving adding salts that react with tartaric acid to form tartrate salts that settle out of the wine
must adjustments - tannin
tannin can be added to improve deficiencies, stabilize color, and improve a wine’s tannin structure
it reduces the oxidative impact of botrytis, as well as the sensory impact of pyrazine and other off-aromas, including smoke taint
non-saccharomyces yeast
Hanseniaspora (Kloeckera), Candida (Metschnikowia), and Torulaspora. These yeasts are often present at the beginning of fermentation, but most are not very alcohol tolerant, and their populations decline once alcohol begins accumulating
Zygosaccharomyces, Saccharomycodes, and the notorious Brettanomyces bruxellensis (Dekkera bruxellensis) are spoilage yeasts- more heat tolerant, so they are dominant toward the end of fermentation
important bacteria in winemaking
lactic acid bacteria- many types are inhibited at alcohol levels above 8%. Oenococcus oeni is preferred- is is alcohol and low pH tolerant, and less likely to create VA aromas. found on grapes and in wineries, and can also be added
acetic acid bacteria- converts alcohol to acetic acid (vinebar). sulfur dioxide and limiting exposure to oxygem keep it at bay
what nutrients does yeast require during fermentation?
oxygen- helps build healthy cell walls so it can survive in a high alcohol environment
nitrogen- low levels are associated with yeast’s production of hydrogen sulfide (H2S), a reductive thiol that smells like rotten eggs, and stuck fermentations
yeast assimible nitrogen (YAN) should be at 200 or more (sum of ammonia and amino acids present in the juice). diammonium phosphate (DAP), an easy-to-metabolize form of nitrogen can be added
reductive wine
- Low levels of nutrients, high temperature, and other stressful fermentation conditions will favor the production of sulfides
- All yeasts produce some H2S during fermentation, but some strains produce more than others.
- At low concentration, these compounds can be responsible for “positive reduction” (matchstick, flint) and can add complexity to wine, while higher levels cause unpleasant reductive aromas (eggs, skunk, rubber, cabbage, garlic, sewage).
reductive winemaking = reducing exposure to oxygen, to preserve delicate aromatics.
only the action of yeast gives the flinty, matchstruck “reduction” aromas. however, a lack of oxygen for the yeast early on can encourage sulfide production, and exposure to oxygen later can mask some unpleasant aromas
temperature of fermentation?
white wine: mid 40s-mid 60s F
red wine: mid 70s to low 90s F
yeast can survive and work between 45 and 95 F
purpose of cap management
helps to regulate the fermentation temperature by breaking up hot and cold pockets, keeps the cap from drying out, and discourages the growth of acetic acid bacteria. It can also be used to introduce oxygen into the fermentation for yeast health
battonage
or lees stirring.
- Toward the end of primary fermentation, stirring may be used to keep yeast in suspension and encourage the fermentation to finish.
- Stirring is also employed during wine aging to improve mouthfeel by incorporating mannoproteins, which are proteins found in yeast’s cell walls, and other products of yeast autolysis.
- The presence of yeast creates a reductive aging environment, and bâtonnage introduces oxygen that is consumed by the yeast. In general, stirring keeps the lees fresh and reduces reductive aromas.
how to prevent malo?
wine is sulfured as soon as possible following primary fermentation and is almost always sterile-filtered prior to bottling to prevent refermentation in bottle.
French oak species
Quercus robur and Quercus petraea (or Quercus sessilis),
coarser grained, more tannic
American oak species
Quercus alba
denser, with less tannin and a higher concentration of oak lactones, resulting in more vanilla and coconut flavors
French oak forests
oak from the forests of Tronçais, Allier, and Jupilles are tighter grained,
Nevers and Bertranges are medium grained, and Vosges is looser grained.
Oak from Limousin is Q. robur-dominant, coarse grained, and often preferred for spirits over wine.
humidity and barrel aging
Wine aged in a cave with a relative humidity of around 70% will lose alcohol and water in the same proportion.
If the relative humidity is higher than 70%, the alcohol level will decrease through aging.
Alternately, if the relative humidity is less than 70%, alcohol will increase.
benefits of SO2
anti-microbial and highly effective at inhibiting bacteria and some non-Saccharomyces yeast, though Saccharomyces and Brettanomyces have higher tolerances and may not be disabled completely by SO2.
reduces impact of oxidation by binding with products of oxidation, and acetaldehyde
bound SO2 = SO2 that has bound to sugar, tannin, acetaldehyde, etc
free SO2 = what protects the wine
types of tannin fining agents
casein (milk), albumin (egg whites), isinglass (fish swim bladder), and gelatin (tendons and muscles).
Alternatively, PVPP and nylon are synthetic, vegan fining agents used to remove small phenolic compounds that cause bitterness and browning in white wine.
Fining is more prevalent in cooler regions, where fruit is harvested less ripe and tannins may be underripe or rustic.
bentonite fining
bentonite is a clay that is used in white winemaking both for clarification and removing solids, and also for binding to proteins before bottling so the wine is protein stable.
small fluctuations in heat after bottling can make proteins in wine less soluble, and the wine can become hazy. removing these ensures the wine stays clear
copper fining
removes unpleasant thiols, or mercaptans, that cause reductive aromas (rotten eggs, onion, garlic, skunk) in wine. these aromas originate from unhealthy yeast during fermentation and aging
cold stabilization
When wine is chilled, the solubility of tartrate salts in the wine decreases, forcing them to precipitate out of solution. In many wines, potassium bitartrate and, to a lesser extent, calcium bitartrate, known colloquially as tartrates, are important examples of this phenomenon. Often, a wine is saturated, or at maximum capacity, with these tartrate salts. When the temperature is reduced, the tartrates become less soluble and form crystals.
preventing oxidation in barrel
regular topping up
SO2 additions
how to stop fermentation
either by temperature reduction and sulfur addition, which inhibits the yeast, or
through filtration or centrifugation, which remove the yeast.
Fortification with a high-proof spirit is another option to arrest fermentation
