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Viticulture/Vinification > Harvesting and processing > Flashcards

Harvesting and processing Flashcards

1
Q

Regarding agrochemicals, what must you do in the vineyard before harvest?

A

There is a minimum number of days for last application before harvest. Causes fermentation and health problems. Late sulfur can cause problems with hydrogen sulfide

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2
Q

What late applications cause problems with fermentation?

A

Copper-based sprays (brown haze)

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3
Q

What pre-vintage plans must be taken into consideration?

A

Estimate crop levels for tank space
Check and clean harvesting and processing equipment
Clean tanks
Purchase necessary products

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4
Q

Advantages/disadvantages of manual harvesting?

A 
Good:
No damage
Select individual bunches for ripeness
No terrain, spacing, training limits
Little equipment needed

Bad:
high labor needed
Slower

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5
Q

When was machine harvesting first introduced and what were machines like? Now?

A

1960s - vertical metal fingers that beat the vine

Now - fiberglass rods strike foliage horizontally, then horizontal conveyor belts

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6
Q

Pros/cons for machine harvesting?

A

Good:
Speed
Night harvest
Lower costs

Bad:
Berry damage
Imprecise selection unless new machine
Expensive machine purchase
Terrain issues
Must have specific trellising systems
Rows must be ride enough
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7
Q

Techniques for limiting berry damage during picking and transport

A 
Shallow picking containers
Limit moving grapes
Reduce load level and dumping heights
Refrigerated truck
Minimize delay between picking and processing
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8
Q

What are the main concerns between picking and processing?

A

Oxidation (causes brown juice and loss of aroma)
Microbial growth
Contamination

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9
Q

How to limit oxidation before processing

A

Limit air contact (blanket with CO2 or N)
Add sulfur dioxide to freshly harvested grapes
Harvest when cool (rate of oxidation increases as temp increases)
Process quickly

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10
Q

What is microbial growth affected by?

A

Health of grapes
Hygiene
Temperature and time
Berry integrity

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11
Q

How can contamination occur before processing?

A 
Rainfall (dilutes sugar)
Leaves and stalks in bins
Picking shears in picking bins
MOG harvested by machines
Soil, oil, metal or plastic tains
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12
Q

What is MOG?

A

Material other than grapes

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13
Q

De-stemming advantages and disadvantages (for whites and reds)

A

Good:

  • Removal of stems which can be herbaceous and bitter when unripe
  • Removal of MOG
  • More fruit can fit in press (whites)
  • Stems can absorb color and alcohol (reds) and release more water and K

Bad (whites):

  • Cheap destemming machine can damage stems and release bitter flavors
  • Pressing without stems is slower
  • Pressing whole bunches releases fine juice with low phenolics and solids (bc fast drainage)

Bad (reds):

  • Increased compaction in the cap = more difficult temperature control and phenolic extraction
  • Tannins in stems can be good to fix oxidation and color
  • Slower pressing
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14
Q

When is de-stemming definitely NOT done?

A

Sparkling wines

Carbonic maceration

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15
Q

When can sorting be done?

A

Before destemming, after, or both

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16
Q

How does destemming work?

A

Spinning perforated drum allows berries only to pass through perforations and stems are pulled away by contra rotating blades

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17
Q

Why are grapes crushed?

A

Release juice so it is immediately available to yeast
Faster pressing in white winemaking (free run juice is liberated first)
Increase in tannin and color in reds (more contact)

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18
Q

Why not crush? Where?

A

semi-carbonic maceration keeps some whole berries intact

Spain, Beaujolais, Languedoc-Roussillon (Carignon)

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19
Q

How does crushing work?

A

Grapes passed between two rollers that break open berry skins
White: can be chilled prior to pressing
SO2 often added

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20
Q

What is pressing and when does it occur?

A

Using pressure to grapes to squeeze the liquids from the solids - gentle but increasing pressure
Whites: usually ASAP after reception (whole bunches or destemmed and crushed grapes). Free run juice drained first

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21
Q

What percentage of the total weight should pressing extract?

A

About 70%

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22
Q

Which white grapes might benefit from skin contact? Why?

A 
Sauvignon Blanc
Semillon
Muscat
Gewurztraminer
Riesling
Extract aromatic compounds but a richer style of wine also results
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23
Q

What aids extraction when doing white wine skin contract?

A

A pectolytic enzyme

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24
Q

What temperature is generally used when doing white wine skin contact? How long?

A

5-10C

3-24 hours

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25
Q

What is the concern of using skin contact for whites?

A

Releasing bitter phenolic compounds

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26
Q

What is press wine?

A

The wine released by pressing grape pomace at the end of fermentation and post-fermentation maceration
Reds
Is usually tannic and dark in color - can be astringent and bitter

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27
Q

Types of presses?

A 
Vertical screw press/basket press
Horizontal screw press (Vaslin)
Pneumatic press (Willmes)
Tank press
Continuous screw press
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28
Q

How does a basket press work? Pros/cons?

A

Grapes are placed in a cylindrical basket and a removable lid is placed on top. Pressure is applied to top against a stationary plate at bottom. Liquid seeps out between slats and is collected.

Good:
Simple and easy
Filtered through stalks/pomace as extracted, giving clear must

Bad:
Slow and labor intensive
Long time
Exposed to oxygen

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29
Q

How does a horizontal screw press work? Pros/Cons?

A

Basket press on its side with pistons at either end
Stainless steel screw running through center
Pistons move together

Pros:
Simple to fill and empty
Operation can be automated
Partially protected from oxidation by blanketing receiving tray with gas

Cons:
Breaking up the pomace between cycles is violent (extracts phenolics)
High pressures = reduced quality

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30
Q

How does a pneumatic press work? Pros/Cons?

A

Horizontal but with a pneumatic bag/membrane that can be inflated by air or water
Grapes are place in between bag and drum which presses against the holes and liquid passes through

Pros:
Good liquid extraction at low pressure
Gentle breaking of pomace

Cons:
Longer press cycle

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31
Q

What is the tank press? Pros/cons?

A

Variant of pneumatic
Pressing occurs in a closed tank that can be pre-flushed with inert gas
Grapes put in a non-perforated tank and pressed against internal drains by bag

Pros:
No oxidation
Low pressures high extraction

Cons:
Longer press cucles
Expensive

32
Q

What is the continuous screw press? Pros/cons?

A

Used for large quantities as it isn’t a batch press
Perforated drum with screw inside
Grapes loaded into one end and then screw pushes the grapes towards resistance at far end to expell liquid from perforations

Pros:
Continually loaded, high output

Cons:
Higher pressures and rough screw=lower quality uice

33
Q

What is SO2?

A

A colorless but toxic gas used since 17th century in winemaking

34
Q

How much SO2 is produced by yeast in fermentation?

A

10mg/L

35
Q

Why is SO2 used in winemaking?

A

Antiseptic (inhibits development of microorganisms)
Antioxidant (combines with oxygen so doesn’t oxidize)
Antioxidasic (Denatures enzymes that propel oxidation)
Combines with Acetaldehyde (byproduct oxidation)

36
Q

How is sulfur added in wineries (what forms)?

A

Potassium metabisulfite powder (can be dissolved in an acid solution) - harvested grapes directly
Pure SO2 gas in liquid form
Dissolved in solution (5%)
Burning sulfur tablets or candles (in barrels)

37
Q

What are the general recommendations for sulfur additions in grape must?

A

White: 60-100 mg/L
Red: 10-60 mg/L

38
Q

Why would sulfur additions be increased?

A

Style of wine (more aroma preservation = more sulfur)
Grape health
pH (more pH = higher SO2)

39
Q

What is the total sulfur dioxide?

A

The sum of free SO2 and bound SO2 present in juice or wine

40
Q

What is free SO2? How does it exist in wine?

A

Portion that is active and has protective properties - only molecular SO2
Two parts:
Active molecular SO2
Dissolved in present water to form sulfurous acid

41
Q

How does pH relate to active SO2?

A

In free SO2, only the molecular SO2 has any protective properties, although all free SO2 is active. The amount of molecular SO2 that is dissolved into sulfurous acid is dependent o pH.
Lower pH = higher molecular SO2 remaining

42
Q

What is bound SO2?

A

The portion of sulfur dioxide that has combined with various components in grape must. (sugars, aldehydes, ketones)
It is inactive at this point

43
Q

What are the maximum limits for total SO2 in dry and sweet wines?

A

Dry red: 150 mg/L
Dry white: 200 mg/L
Off-dry (5g/L sugar): 250 mg/L
Lusciously sweet BA/TBA, Sauternes: 390 mg/L
Organic wines lower
Sweet is higher bc sugars bind with SO2 readily

44
Q

Why clarify a grape must? How?

A

Whites and rosés
Remove solid particles suspended in must = cleaner flavors and less bitterness

Ways:
Cold settling
Centrifugation
Diatomaceous earth filtering
Flotation

NOTE: Fermentation necessitates clarification again

45
Q

How does cold settling work?

A

Simple and effective - uses gravity - HIGHEST QUALITY
Settle pressed must overnight between 5-10C
suspended solids sink to the bottom and clear must is racked off
Pectolytic enzymes can be used

46
Q

How does centrifugation work?

A

Separate solids at high speed by centrifugal force
Harsh and oxidation risk BUT very clean
Expensive
Large wineries

47
Q

How does diatomaceous earth filtration work?

A

Filter with a diatomaceous earth filter
Used for aromatic varieties
Can reduce nutritional content too much = yeasts struggle to ferment

48
Q

How does flotation work?

A

Bubble small amounts of air (N, CO2) through cloudy must from bottom
Bubbles catch solid particles and float to surface
Rarely used
Large wineries

49
Q

How is enrichment done?

A

Add either sucrose (beer sugar or cane sugar) = chapitalization
^^^ cheaper and more netural
Add concentrated unfermented grape juice aka rectified concentrated grape must (RCGM)

50
Q

What is RCGM?

A

Rectified concentrated grape must used for enrichment

51
Q

How much does each kilogram of sugar increase a wine’s volume by?

A

1kg=.63L increase

52
Q

Generally, how much sugar does it require to raise ABV by 1% (white and red)?

A

White: 17g/L
Red: 19g/L (higher fermentation temp and pumping over = evaporation)

53
Q

Techniques for concentrating must

A

Concentrates grape juice by removing water - a form of enrichment

  • Cryoextraction
  • Reverse osmosis
  • Vacuum evaporation
54
Q

How does vacuum evaporation work?

A

Used since 1989 in France
Evaporate must in a vacuum
Evaporates at 20C to minimize loss of aromatic and flavor potential

55
Q

What is reverse osmosis and how does it work?

A

Filtration technique that is superceding vacuum evaporation
Uses differences in molecular weight
High pressure applied to must along a membrane filter - water passes through membrane
Concentrates EVERYTHING even off flavors and unripe tannins
ALSO USED FOR removing alcohol and volatile acidity

56
Q

What is cryoextraction?

A

Freeze fresh grapes until water freezes, press solids and frozen water off
OR freeze grape must (controversial)

57
Q

What are the level rules for concentrating musts?

A

Musts may not be enriched by concentrated by more then 2% potential alcohol
OR by a maximum reduction in volume of 20%
Whichever is lower

58
Q

What is potential alcohol?

A

Concentration of alcohol that would result from the fermentation to dryness of all the sugar dissolved in a must

59
Q

What is actual alcohol

A

Actual level of alcohol in a wine after fermentation

60
Q

What is total alcohol?

A

The actual alcohol plus potential alcohol from residual sugar

61
Q

What is natural alcohol?

A

The total alcohol in an unenriched must or wine

62
Q

How much can total acidity be reduced by?

A

no more than 1 g/L (expressed by tartaric acid)

Forbidden in warmest regions

63
Q

How to de-acidify?

A
  • Add potassium bicarbonate post-clarification, pre-fermentation (preferred) - only tartaric
  • Add calcium carbonate (high levels of calcium tartrate form which are harder to remove and tartrate-unstable) - only tartaric
  • Double-salt deacidification (add special calcium carbonate which has calcium tartrate-malate added) Removes both tartaric and malic acids
  • Malolactic fermentation - only malic
64
Q

When might the expense of a double salt deacidification be justified?

A

In very cool regions when malic acid levels don’t have a chance to fall with ripening
Typically tartaric is the main acid so it isn’t necessary

65
Q

What is a risk of de-acidification?

A

pH raises which increases the risk of microbial infection and decreases SO2 effectiveness.

66
Q

Why don’t titratable acidity and pH correspond directly?

A

1) Buffering effect of dissolved salts

2) pH is a logarithmic scale while TA is a linear scale

67
Q

How does pH affect color in red wines?

A

Low pH = brighter and more blue/purple

High pH = duller and more garnet/brown

68
Q

What type of acid is used for acidification? When? What are the legal EU limits and where?

A 
Tartaric acid
Before fermentation (better integration)
Must: 1.5 g/L
Wine: 2.5 g/L
Only in CII and CIII zones
Some exceptions in very warm years
69
Q

What is the limit for citric acid? When should it be added?

A

Not as desirable as tartaric acid but increases stability
Total citric acid concentration: 1g/L
Add AFTER fermentation because it can be metabolised into acetic acid aka volatile acidity during fermentation

70
Q

What are other additives to must?

A
  • Tannins
  • Bentonite: form of clay used as a fining agent in white wines to remove dissolved proteins (usually after fermentation but sometimes before depending on winemaker preference)
  • -Also removes flavor compounds so use sparingly
71
Q

Why might a winemaker choose to handle a must oxidatively?

A

Some varieties show that this leads to more complex aroma and flavor development
ie: Chardonnay

72
Q

What is hyperoxidation?

A

The enzymatic oxidation of phenolics which converts them to insoluble polymers that can be removed by clarification
Result: more stable wine
Bubble oxygen through a wine for a length of time

73
Q

For which varieties is hyperoxidation most effective when it comes to color stabilisation?

A 
Alsatian
German
Chardonnay
Chasselas
Garganega
Trebbiano

NOT SAUV B

74
Q

What does excessive oxygen exposure do for must?

A

Produces acetaldehyde (sherry like flavor)
Creates bitter components from phenolic oxidation
Develops spoilage bacteria

75
Q

What is ascorbic acid and why is it used?

A

Vitamin C
Supplements SO2
Can’t replace it bc no antiseptic effect
Forms Hydrogen peroxide without the presence of SO2

Viticulture/Vinification (7 decks)

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