13. General Winemaking Options Flashcards
1
Q
What is the maximum temp. desired for fermentation?
Why (2)?
A
35 C / 95 F is max.
Above this, fermentation slows down / stops as yeasts struggle to survive. This can lead to stuck fermentation.
2
Q
What are benefits of concrete fermentation vessels (3)?
A
- high thermal inertia (maintain an even temperature more efficiently than steel)
- natural lees stirring occurs in egg-shaped vessels through convection currents.
- after initial investment, cost is low (re-usable)
3
Q
At what concentration must a wine state that it “contains sulfites?”
A
>10mg / L of SO2
4
Q
Explain what happens to SO2 when it is added to must/wine (3):
In what forms does SO2 exist when added to wine and which form is most effective?
A
When added to must/wine, SO2 dissolves and some of it reacts w/compounds in the liquid
=> Dissolved portion is called ‘bound SO2’ and is ineffective against oxidation/microbial spoilage
=> The unbound portion is ‘free SO2’.
Vast majority of free SO2 exists in a relatively inactive form, and a small portion is in the active molecular form, which is the most effective form.
5
Q
How does the timing and size of SO2 additions influence its efficacy (4)?
A
- Adding a larger amount at 3 key points is more effective than small amounts throughout:
CRUSHING / END OF MLF / BOTTLING
6
Q
What are disadvantages of cultured yeast? (2)
A
1) can lead to a similarity of fruit expression (“industrial wine”)
2) adds the cost of using a commercial product
7
Q
What happens if Nitrogen levels in must are low during fermentation?
What can winemakers do to correct this?
A
- Low nitrogen levels can lead to stuck fermentations and rotten egg smells from sulfur compounds.
- Winemakers can add yeast nutrients, e.g. Diammonium phosphate / thiamine.
8
Q
What does the fermentation process also produce aside from alcohol, CO2 and heat (4)?
A
1) volatile acidity (not enough to be detected)
2) very small amounts of naturally produced SO2
3) wine aromatics (from aroma pre-cursors + those created by yeast)
4) glycerol (increases body of wine)
9
Q
What are benefits of stainless steel fermentation vessels (5)?
A
- easy to clean
- large range of sizes available
- high level of mechanization (temp. control, auto pump-over, auto-emptying)
- neutral vessels (no added flavors from oak/oxygen)
- after initial investment, cost is low (can be re-used indefinitely)
10
Q
Historically, how did MLF occur?
How can it occur now (2)?
A
- often happened spontaneously in spring as temps rose.
- now process can be started by adding cultured lactic acid bacteria + ensuring favorable conditions.
11
Q
How does the presence of oxygen influence growth of spoilage bacteria?
A
Favors the growth of spoilage bacteria e.g. acetic acid bacteria + Brett., esp if other conditions are favorable, e.g. presence of RS.
12
Q
Why would / wouldn’t a wine maker conduct malolactic conversion in barrels vs larger batches in tanks (2)?
A
- Allows for the ability to stir lees at the same time as malo and promote better integration of flavors.
- This is also more labor-intensive because barrels may be at different temps, so all barrels need to be monitored individually.
13
Q
How can controlled exposure to oxygen be good for some wines (6)?
A
- promotes growth of yeast population to start/maintain fermentation.
- lessens reductive off-flavors.
- can lead to greater oxygen stabalization in some white wines = increased aging potential.
- essential for reaction btw/anthocyanins + tannins to create greater color stability in red wines.
- can give greater diversity of aromas/flavors (fresh vs dried fruits, honey, caramel, coffee etc…)
- vital for certain wines, e.g. Oloroso Sherry, Madeira, Tawny Port.
14
Q
How will sorting differ for good/bad vintages and grapes intended for inexpensive/premium wines (4)?
A
- Good years: grapes might be in perfect condition, little sorting may be needed (MOG still needs to be removed)
- Bad years: greater level of sorting required to remove moldy / under-ripe grapes.
- Inexpensive wines: may not be sorted at all ($$$+time for machinery/labor)
- Premium wines: only the highest quality grapes will be used, high level of sorting required.
15
Q
What are 3 options for removal of alcohol after fermentation?
A
1) adding water (dilutes flavour)
2) reverse osmosis (most common high-tech option, very $$$)
3) spinning cone (extracts vol. aroma compounds from wine then removes alcohol – flavour components added back in)
16
Q
What is the difference between crushing and pressing?
A
- crushing = breaking grape’s skins and releasing juice, making it available for fermentation
- pressing = separation of juice/wine from skin/seeds
17
Q
What is the French word for grape sorting?
A
Triage
18
Q
Besides stainless steel, concrete and wood, what are 2 fermentation vessels used by wineries?
A
1) Plastic vessels (useful for small-batch, but permeable to oxygen + hard to control temp.)
2) Terracotta (e.g. amphorae in Georgia)
19
Q
What are the 2 pictures below of?
A
1) Pneumatic Press
2) Basket Press
20
Q
What is the relationship btw/Oxygen and Yeast (3)?
A
- Initially, yeasts need O to multiply quickly.
- Once O is used up by yeast via aerobic respiration, they switch to fermentation.
- Fermentation required the absence of oxygen (anaerobic environment).
21
Q
What are some ways a winemaker can actively discourage MLF (5)?
A
- cooling temp to below 15 C / 59 F
- adding SO2
- adding lysozyme (kills lactic acid bacteria)
- move any batch that is undergoing MLF (prevents spread of LA bacteria)
- filter out LA bacteria.
22
Q
What is reductive/protective winemaking?
A
Practice of minimizing oxygen exposure during winemaking process
23
Q
What are (3) advantages and (2) disadvantages of wood fermentation vessels?
A
AD: - retains heat well
- allows a small amount of oxygen
- can be re-used (inexpensive in the long term)
DIS: - great care must be taken to maintain hygenic conditions (wood can harbor spoilage orgs.)
- Initial investment of new barrels is high.
24
Q
What are the 2 main methods of chilling down grapes once they reach the winery?
What is a disadvantage of having to chill grapes, and how can this be avoided?
A
- Refrigeration unit (used for whole bunches); takes longer but can be a useful place to store grapes.
- Heat exchanger; works quickly on grapes that are de-stemmed/partially crushed.
Both methods = investments of equipment + energy usage. Harvesting at night/morning helps to avoid these costs.
25
What are disadvantages of ambient yeast? (3)
1) fermentation may start slowly -- results in build-up of VA and spoilage yeasts (e.g. Brettanomyces) = off-flavors.
2) fermentation to dryness may take longer + higher risk of stuck fermentation.
3) consistent product can't be guaranteed.
26
What is the most common species of yeast used in winemaking?
Why (4)?
- saccharomyces cerevisiae
- it can withstand high acidity/alcohol
- it is resistant to SO2
- reliably ferments must to dryness.
- there are different strains = winemakers can choose for desired outcome.
27
What are the 2 types of wine aromatics produced as a result of fermentation?
Give examples (2 each):
- Aromas from pre-cursors; e.g. thiols (gooseberry in SB), terpenes (floral notes in Muscat.)
- Aromas created by yeast; e.g. esters (banana from carbonic), acetaldehyde (paint thinner in Fino Sherry)
28
Why is de-acidification done?
What is the most common method and what is an alternative?
Why is the alternative less common?
- done in cool climates where grapes may have to be picked before they're ripe (e.g. inclement bad weather)
- adding calcium carbonate (chalk) or potassium carbonate.
- Ion exchange is an alternative = much more expensive.
29
What are some things that can be done to minimize the threats of oxidation and acetic acid bacteria in transportation to the winery (4)?
1) harvesting at night (cooler temps)
2) addition of SO2 (anti-oxidant / anti-microbial)
3) putting grapes in cold storage once received at winery
4) sanitizing equipment/bins
30
In the EU, what are the max. concentrations of SO2 for red and white wines?
Red: 160 mg/L
White 210 mg/L
31
What is ambient yeast?
AKA (2)?
What are 2 species of ambient yeast?
Yeast that is present in the vineyard/winery
AKA "wild yeasts" / "natural yeasts"
Kloeckera / Candida
32
How do yeasts usually behave during a "wild fermentation" (3)?
- These yeasts will start the fermentation if not inoculated.
- Most die once alcohol \> 5%
- Saccharomyces cerevisiae will soon become dominant yeast.
33
Why doesn't destemming have to be carried out for machine-harvested grapes?
Machine-harvested grapes are collected by shaking grapes off their stems in the vineyard.
34
What is malolactic conversion?
When does it happen and why would a winemaker choose one time vs another?
- result of lactic acid bacteria converting malic acid into lactic acid and CO2 (and heat)
- happens after alcoholic fermentation and during it occasionally.
Studies have shown that when ML happens **during** fermentation it can increase fruity characteristics and reduce production times which saves money as the wines can be finished and sold earlier.
35
What is an example of a yeast cultured yeast species besides Saccharomyces cerevisiae and what particular wines is it used for?
*Saccharomyces bayanus*
Used for must w/high potential alcohol or for re-fermenting sparkling wine.
36
What is alcoholic fermentation?
The conversion of sugar into ethanol and CO2 carried out by yeast in the absence of oxygen (anaerobically)
37
What is an option for removing / adding color tints post-fermentation?
What consideration must be made regarding this process?
REMOVING: fining wine,
ADDING: using grape-derived coloring agents, e.g. MegaPurple.
Adding coloring agents is not legally allowed in certain regions, e.g. Ribera del Duero.
38
What are cool, mid-range and warm temperatures during fermentation and what styles of wine do they favor?
- cool (12-16 C / 54-61 F) favours fresher, fruiter whites and roses
- mid-range (17-25 C / 63-77 F) favours easy drinking fruity reds
- warm (26-32 C / 79-90 F) favours powerful reds
39
What are some factors determine the level of grape sorting performed, or whether it is performed at all (4)?
- _Ripeness and health of fruit_ (healthier, riper fruit from a high quality vintage may not require much sorting at all).
- _Intended final wine quality and price_ (meticulous sorting improves quality but also has extra costs implications of labor, time, discarding of grapes leading to lower yields).
- _Pre-arrival sorting_ (has sorting already been performed by skilled hand-pickers?)
- _Physical state of the grapes_ (grapes at the bottom of large containers will be crushed and too liquid to sort).
40
Why is oxygen threatening for the production of fresh, fruity white wines (3)?
Why are red wines not as susceptible to these effects?
- many fruity aroma compounds break down (e.g. thiols in Sauvignon B.)
- unwanted aromas can develop (e.g. acetaldehyde = nutty flavors)
- color of wines can darken w/oxidation (become gold/brown)
Red wines = more phenolic compounds that have an anti-oxidative effect, more oxygen is absorbed before effects are perceptible.
41
What are the 4 processes that may be employed once grapes are received for Standard Winemaking?
1) chilling
2) sorting
3) destemming (only for hand-harvested)
4) crushing
42
The EU stipulates the amount of acidification/enrichment allowed for wines depending on their Zone.
What are examples of regions in the 3 different Zones?
Zone A (Coolest Regions): Germany (excluding Baden), UK
Zone B-CIIIa (Moderate Regions): Bordeaux, Galicia (NW Spain), Trentino Alto-Adige.
Zone CIIIb (Hottest Regions): Most of Portugal, S. Spain, S. Italy, Greece.
43
What is happening in the pitures below?
Starter batches (grape must activated w/cultured yeast) are being added to a tank of unfermented grape must.
44
A Horizontal Screw Press is similar to:
How does it work (5) ?
Why is it a less popular choice in wineries (2)?
- Similar to basket press, but horizontally on top of a rectangular tray.
- grapes are loaded =\> pressed =\> skins removed =\> press is cleaned =\> next batch loaded.
- Very time consuming / less gentle
45
When transporting hand-harvested fruit to the winery, what is a consideration that should be made to ensure quality is maintained (2)?
- If fruit from crates is tipped into larger hoppers, some fruit will be naturally be crushed by weight on top of it, leading to potential oxidation, microbial spoilage, and unwanted premature fermentation.
- Therefore SO2 might be added in the form of potassium metabisulfite to maximize quality.
46
Give 2 examples of how different strains of Saccharomyces cerevisiae can offer different outcomes depending on the style of wine desired?
- some strains boost aromatic character (e.g. used for Marlborough SB)
- some strains produce a more restrained fruit profile (e.g. used for Sancerre)
47
What are some steps winemakers can take to limit the effects of oxidation on grape must / wine (5)?
1) avoiding ullage by topping up vessels
2) use of "inert" gases (nitrogen, CO2, argon) to flush out oxygen from machinery/fill ullage
3) addition of SO2
4) use of impermeable containers for fermentation/maturation (e.g. stainless steel / concrete) as well as packaging (glass bottles w/screwcap)
5) cool, constant temperatures which slow the rate of oxidation.
48
Why would a winemaker choose to chill down grapes as they reach the winery (3)?
- If grapes were harvested in warm conditions (sunny, warm afternoon)
- decreases rate of oxidation = preservation of fruity aromas
- reduces microbial spoilage
49
What are 4 examples of must adjustment?
1) enrichment (adding alcohol)
2) reducing alcohol
3) acidification
4) de-acidification
50
What conditions encourage and discourage Malolactic Conversion (3 each)?
- encourage = 18-22 C / moderate pH (3.3-3.5) / low total SO2
- discourage = temps
51
What are options for temperature control during fermentation (3)?
Which option is the most common?
1) temperature of cellar (sluggish ferments can be moved to warmer room)
2) use of water or glycol in jackets that surround vessels (most common)
3) temperatures can be reduced by pumping over (releases heat)
52
What is cultured yeast?
AKA (2)?
- strains that are selected in a lab and then grown in volumes suitable for sale
AKA selected yeast / commercial yeast
53
How does a pneumatic press work (2)?
aka:
Cylindrical cage with bladder that runs down middle
-\> bladder inflates and grapes are pushed against grates on side of cage
aka 'air bag press'.
54
What are 3 ways to "enrich" wine?
1) adding dry sugar (beet or cane) (called "chaptalisation")
2) adding grape must, grape concentrate or RCGM
3) the processes of concentration (reverse osmosis, vacuum evaporation, cryoextraction)
55
What are 3 technological methods of concentrating sugar levels in must?
How do these methods compare in terms of cost?
1) Reverse Osmosis
2) Vacuum Evaporation
3) Cryoextraction (freezing must/wine, removing ice from it)
Reverse Osm. + Vacuum Evap. = expensive, only suitable for high return / high volume wines.
Cryo. = less costly, used more widely
56
What are some advantages of using a Pneumatic Press for crushing grapes (3)?
- Can be programmed to exert different amounts of pressure according to the level of extraction desired.
- Can be flushed w/inert gases before use to protect grapes from oxidation.
- Appropriate for large-scale wineries.
57
How do destemmers generally work?
Series of blades within a rotating drum that removes grapes from stems.
58
When can acidification take place?
When do winemakers typically prefer to do it, and why?
- Before, during or after fermentation.
- Before is preferred, because acidity is integrated better within the profile of the wine as a whole.
59
What are advantages of ambient yeast? (4)
1) can add complexity (numerous yeasts = numerous aroma compounds)
2) costs nothing
3) adds to "terroir" (region-specific yeasts)
4) can be used in marketing of wine
60
What is a unique rule in the EU regarding chaptalization and acidification (2)?
Winemakers may not both acidify *and* chaptalize their wine musts.
This rule prevents wines from being "stretched" by the 2 additions.
61
Why would small crates be used to transport grapes to the winery (3)?
1) Maintining quality of grapes by reducing damage.
2) Small scale of operation, e.g. in many Italian regions grape growers only have 1 ha to harvest.
3) Minimal crushing = minimal oxidation + microbial spoilage.
62
2 examples of fermentation/maturation vessels that are impermeable to oxygen:
2 examples that are permeable:
Stainless steel / thick cement.
Wooden vessels / plastic.
63
If a winemaker desires to use cultured yeasts, what are 2 methods of assuring that ambient yeasts are supressed?
1. Must is cooled down to prevent fermentation, cultured yeasts are added which overwhelm native yeasts.
2. SO2 is added to supress native yeasts and a starter batch w/ cultured yeast is added to tank.
64
What are advantages (1) and disadvantages (4) to using a Basket Press to crush grapes?
AD: - some winemakers believe they are gentler than Pneumatic presses.
DIS: - not sealed vessels = oxygen/microbial exposure cannot be avoided.
- can only press small loads
- much more labor intensive
- only really suited for small wineries making premium wines
65
What are advantages of cultured yeast? (4)
1) produces reliable, fast fermentation to dryness
2) produces low levels of VA and less risk of spoilage
3) consistent product from one year to another
4) many strains to choose from = style of wine can be influenced.
66
How does computerization of modern presses help winemakers achieve a certain style of wine (3)?
- Pressure and length of cycle can be adjusted.
- less pressure = less tannin / color from skins, but also less vol. of wine.
- longer press cycle extends contact = more aroma/flavor/tannin.
67
What factors might affect a winemaker's decision of adding SO2 (4)?
- Max. concentrations of SO2 are defined by local laws.
- Sweet wines = permitted to contain higher levels.
- Organic wines in EU must contain less than non-BIO (in US, additions are not permitted)
- If a "natural" style is desired, might choose to add less/no SO2.
68
How can oxygen exposure be increased during winemaking? (5)
1) use of cap management techniques that spray/splash e.g. pump-over.
2) use of small wooden barrels
3) increasing number of rackings/lees stirring during aging
4) allowing ullage w/out inert gases.
5) use of techniques that involve pumping oxygen through must (e.g. hyperoxidation) /wine (e.g. microbullage/micro-oxygenation)
69
What are the outcomes of malo? (4)
1) reduction in acidity and rise in pH - lactic acid = weaker\>malic.
2) some colour loss in reds
3) greater microbial stability (less likely that MLF will happen later at inconvenient time)
4) modification of flavour (buttery notes in white wine, slight loss of fruit character)
70
How does an Optical Sorting Machine work (2)?
What are the disadvantages of this system (2)?
Who is most likely to use this system?
- High tech machine that uses digital imaging + software to scan individual grapes and eliminate those that do not meet the standards chosen by the grape grower.
- Also removes MOG.
- Major investment of machinery / cannot be used for whole-bunch winemaking.
Used mainly for high value grapes e.g. Grand Cru Classé estates of Bordeaux.
71
What are the various forms in which SO2 can be applied (4)?
- Gas, liquid or solid
- Sulfur Dioxide
- Potassium Metabisulfite
- Potassium Bisulfite
72
How can excess SO2 affect the flavors of the final wine (2)?
What can be done by a winemaker to lessen the amount of SO2 needed (4)?
- Excess SO2 can dull wine aromas/flavors + make it taste harsh.
- Good winery hygiene / effective sorting / limiting O2 exposure / maintaining cooler temps.
73
How does a basket press work (3)?
2 synonyms?
A "basket" is filled with grapes and pressure is applied from above
- \> juice runs through gaps/holes in side of basket and collected by a tray
- \> pipe transfers juice/wine from tray to another vessel.
AKA "Vertical Press" / "Champagne Press"
74
What are the right conditions for yeast to convert sugars in must into alcohol? (3)
1) viable temperature range
2) access to yeast nutrients (nitrogen)
3) absence of oxygen
75
Explain how reverse osmosis removes alcohol from wine (2):
RO is a form of cross-flow filtration that removes flavorless permeate of alc + water, which is then distilled to remove alcohol.
- the permeate is then blended back to recreate the wine.
76
What is a definition of yeast (3)?
A collective term for the group of microscopic fungi
=\> that converts sugar into alcohol **AND**
= \> affects the aroma/flavour characteristics of a wine
77
What is the definition of Potential Alcohol?
The amount of alcohol that would be created if all naturally-occurring sugars in the must are fermented into alcohol.
78
What do grape stems contain that must be considered when choosing to destem or not (3)?
- Stems contain tannins.
- Not desired for most white wines.
- If stems are not ripe = unwanted green flavors / bitter tannins in wine.
79
What is Chaptalization?
What is used?
When in the fermentation process is this usually carried out and why?
The addition of dry sugar to must/wine in order to increase its final alcohol content.
Beet or Cane sugar can be used.
- Usually carried out when fermentation is underway b/c yeasts are already active and can cope better w/additional sugar.
80
What is "ullage"?
Ullage is the headspace of air btw/wine and the top of the vessel it is stored in.
81
How does a continuous press work?
Major advantage?
Best suited for:
Why is it a less popular choice in wineries?
- Grapes continually loaded into the press using a screw mechanism.
- Quicker processing of high volumes of grapes.
- Best suited for high volume / inexpensive wines.
- Not very gentle
82
What is sulphur dioxide's two main properties?
1) anti-oxidant -- reduces effects of oxidation by reacting w/products of oxidation reactions + inhibits oxidative enzymes.
2) anti-microbial -- inhibits development of microbes such as yeast and bacteria
83
How does pH level affect how much SO2 needs to be added to musts (3)?
- Generally speaking, the higher the pH, the less effective SO2 is.
- A greater proportion of free SO2 exists in the molecular form in lower pH levels.
- Therefore, greater amounts need to be added to wine/musts with high pH levels to protect from oxidation/microbes.
84
What are 3 options for sorting grapes?
- Removing unwanted grapes/bunches before picking/during hand-harvesting.
- Sorting by hand on a table / vibrating belt (can occur before/after destemming)
- Optical sorting
85
Where would reducing alcohol in a wine be an appropriate action?
In warm/hot regions where sugar accumulates in grapes quickly = undesirablly high alcohol levels.
86
At which stages is SO2 usually added (3)?
- Soon after grapes are picked/reach the winery
- then at various points during winemaking
- at bottling
87
What are 3 examples of when grapes would NOT be de-stemmed?
1) red wine fermentations using whole bunches (ex. PN in Burgundy)
2) carbonic maceration (e.g. Gamay in Beaujolais
3) whole bunch pressing for some whites (high quality sparkling)
88
Why is acidification done and what type of acid is typically used to acidify wines?
What are less common acids used (3)?
Where is it typically carried out?
- done to bring back freshness in warm-climate grapes where malic acid drops dramatically as grapes ripen
- tartaric acid = most common.
- citric acid (not in EU) / malic acid (could turn to lactic during MLF) / lactic acid (less harsh than malic)
- Typical in warmer climates for all types of wine.
89
Even though they might eventually cool or warm must as is required, at what temp. do winemakers tend to start their fermentations?
Relatively warm, e.g. 25 C / 77 F.
90
Identify 3 regions that have a tradition of using large wooden fermentation casks:
How large are these vessels?
Alsace / Germany / Tuscany.
1,000L+
91
What exactly is "must" and what does it typically refer to (2)?
- The mixture of grape juice, pulp, skins and seeds that comes from the crusher.
- Typically refers to the substance that is being fermented.
