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WSET Diploma > Unit 2 - Week 5 > Flashcards

Unit 2 - Week 5 Flashcards

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1
Q

Creation of hydrogen sulfide and other stinky reductive compounds during fermentation is caused by

A

late sulfur application on black grapes

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2
Q

Adversly effect on yeast growth and activity is caused by

A

residual fungicides

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3
Q

Brown haze, potentially toxic levels of copper salts in the wine are caused by

A

copper-based sprays

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4
Q

What leads to browning of grape juice, potential loss of aroma compounds

A

oxidation

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5
Q

As temperature increase the rate of oxidation will

A

increase

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6
Q

What need to be done to reduce the treat of oxidation

A

limit contact with air (some harvest trailers will immediately blanket grapes with carbon dioxide or nitrogen) add small amount of sulfur dioxide to fresh harvested grapes to deactivate oxidising enzymes

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7
Q

Microbial growth is affected by

A

health of grapes hygiene temperature and time berry integrity

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8
Q

Contamination by occur by

A

rainfall (dilute sugar) leaves and stalks picking shears material other than grapes soil, hydraulic oil, metal or plastic taints.

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9
Q

What is material other than grapes

A

mechanical harvesting (leaves, stalks, canes, insects, lizards, etc

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10
Q

In red winemaking stems release what

A

water and potassium which is undesirable, also absorb color and alcohol

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11
Q

Why is grape processing more efficient when de-stemming occurs in white wine making

A

allows more fruit to fit into press

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12
Q

For production of white wines what are de-stemming disadvantages

A

pressing without stems is slower as stems provide drainage channels if its done wrong more bitter and herbaceous flavors are released pressing whole bunches release fine juice with low phenolics and low solid due to rapid drainage

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13
Q

For production of red wines what are de-stemming disadvantages

A

stems will reduce compaction of the pomace cap in fermentation tank, make temperature control and phenolic extraction easier in some varieties stems release good quality tannins which reduce damage done by oxidation, can help to fix color in wine stems increase speed and efficiency of pressing by providing drainage channels

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14
Q

What is added during crushing process

A

sulfur dioxide

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15
Q

In production of white wines pressing temperature, duration

A

between 5-10 C, few to 24 hous

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16
Q

In production of white wines why is pectolytic enzyme added

A

to aid extraction. aim is to extract aromatic compounds but a richer, fuller styl also results. danger is that bitter phenolic compounds may be extracted.

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17
Q

What white varieties may benefit from shor skin contact prior to pressing

A

Sauvignon blanc, muscat, riesling, gewurztraminer, viognier.

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18
Q

In production of red wines, pressing of the pomace at the end of fermentation release

A

more wine which is high in tannin and color. sometimes a portion is add back to wine but sometimes is too astringent and bitter.

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19
Q

This type of press is traditional, cylindrical basket, pressure from the top

A

Vertical screw press (basket press)

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20
Q

Vertical screw press (basket press) advantages

A

simple, easy to use, gives clear must or wine

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21
Q

Vertical screw press (basket press) disadvantages

A

filling and reloading is slow, labour intensive, requires time, risk of extracting bitter phenols, risk of oxidation

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22
Q

What is the name of the press that is basically basket press turned on its side

A

Horizontal screw press (Vaslin)

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23
Q

Horizontal screw press (Vaslin) advantages

A

filling and emptying is simple, automated, liquid can be protected from oxidation by blanketing with inert gas

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24
Q

Horizontal screw press (Vaslin) disadvantages

A

high pressure, reducing potential quality, violent breaking up marc results in extraction of phenolic and astringent matter from skins, seeds, stems

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25
Q

What is the difference between Horizontal screw press (Vaslin) and Pneumatic press (Willmes)

A

Pneumatic press (Willmes) is also basket press turned on its side but inside is cylindrical pneumatic bag or membrane which is inflated by compressed air or even water.

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26
Q

Pneumatic press (Willmes) advantages

A

even at low pressure, good liquid extraction, higher quality; gentle break up of pomace reduce extraction of bitter phenolics

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27
Q

Pneumatic press (Willmes) disadvatages

A

press cycle is slighty longer than horizontal screw press

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28
Q

This press is a variant of pneumatic press which can be pre flushed with inert gas, preventing oxygen exposure

A

The tank press

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29
Q

The tank press advantages

A

oxygen contact with luquid is eliminated, low pressure, gentle breaking of pomace, high quality juice

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30
Q

The tank press disadvantages

A

press cycle is longer than pneumatic press, most expensive type of press

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31
Q

All other presses are batch-process machines, which is labour intensive and time consuming. This press is used to process large quantities of grapes.

A

The continuous screw press

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32
Q

The continuous screw press consist of

A

perforated drum, with Archimedes screw inside

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33
Q

The continuous screw press advantages

A

very high output

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34
Q

The continuous screw press disadvantages

A

quality is not as good as in the batch-process

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35
Q

Colorless, highly toxic gas, produced in small quantities (about 10 mg/L) by yeast during fermentation

A

Sulfur dioxide (SO2)

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36
Q

Sulfur dioxide (SO2) has 4 properties in winemaking

A

-antiseptic. inhibits development of microorganisms -antioxidant. comines with oxygen, removing it before harm can be done -antioxidasic. denatures oxidasic enzymes such as tyrosinase -combines with acetaldehyde (by product of oxidation)

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37
Q

Sulfur dioxide (SO2) is added in wineries in one of four forms

A

-potassium metabisulfite powder. - pure SO2 gas compressed into liquid form - dissoved in solution (normaly 5%) - burning sulfur tablets or candles (for cleaning barrels)

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38
Q

Potassium metabisulfite powder

A

when dissolved in acid solution release sulfur dioxide. due to health reasons not longer permitted to use

39
Q

SO2 is often added to juice before fermentation to control microbial activity and oxidation. (also added to grapes on way to winery) What is quantity used

A

for white must 60 - 100 mg/l for red must 10 - 60 mg/l Powdered form is used

40
Q

Levels of added SO2 can be increased according to style of the wine because

A

if priority is to preserve primary aromas

41
Q

Levels of added SO2 can be increased according to health of the grapes because

A

if rot is present you need to increase SO2

42
Q

Levels of added SO2 can be increased according to pH level because

A

wines with higher pH need more SO2 cause less is in active form

43
Q

What is a Free SO2

A

active, has protective properties. only molecular SO2 has any protective properties. it exists in more than one form in wine. portion dissolves in water to form sulfuruous acid, which is pH dependent. the other part remains as active molecular SO2. lower pH higher proportion remains as molecular SO2

44
Q

What is a Bound SO2

A

has combined with various components such as sugars, aldehydes and ketones. it is inactive

45
Q

What is a total SO2

A

sum of Bound SO2 and Free SO2

46
Q

What is a maximum permitted SO2 level in dry red wines

A

limit of 150 mg/l. natural anti-oxidants are present

47
Q

What is a maximum permitted SO2 level in dry white wines

A

limit of 200 mg/l

48
Q

What is a maximum permitted SO2 level in sweet wines

A

limit of 250 mg/l for off-dry white with 5 g/l RS up to 390 mg/l for beerenauslese/TBA, Sauternes, etc. higher levels due to binding powers of sugars.

49
Q

What is objective of pre-fermentation clarification in production of white and rose wines

A

to remove any solid particles suspended in must to produce cleaner flavors with more finesse and less bitternes

50
Q

How much clarification is needed for production of complex white wines

A

little clarification

51
Q

How much clarification is needed for production of delicate, highly aromatic white wines

A

lot of clarification

52
Q

What is benefits of using cold settling

A

it is simple, effective, natural by gravity. produce highest quality grape must. overnight, cool temp. (5-10 C), clear must racked off the sediment

53
Q

What is a purpose of adding pectolytic enzymes to the must during cold settling

A

they will destroy pectins which are responsible for holding particles of grape flesh in suspension

54
Q

What is a centrifugation

A

pre-fermentation clarification separating the solids by centrifugal force at high speeds

55
Q

What is diatomaceous earth filtration

A

pre-fermentation clarification which achieves highly clarified must, particularly suitable for aromatic varieties.

56
Q

What is a flotation

A

pre-fermentation clarification. bubbling small amounts of nitrogen, carbon dioxide or air through cloudy grape must from the bottom of the vat, used on large volume of wine. when air is used - hyperoxidation at same time

57
Q

What are advantages of centrifugation

A

high level of clarity, used in big wineries

58
Q

What are disadvantages of centrifugation

A

harsh technique, high risk of oxidation, expensive process

59
Q

What is disadvantage of diatomaceous earth filtration

A

it achieves highly clarified must but complete removal of solids can reduce nutrional content of must that yeast may struggle to ferment the sugars present

60
Q

Name four ways of achieving pre-fermentation clarification in production of white and rose wines

A

cold settling centrifugation diatomaceous earth filtration flotation

61
Q

Practice of adding sugar to grape must in order to increase potential alcoholic strength of wine is called

A

enrichment

62
Q

Enrichment is done by adding

A

sucrose (beet or cane sugar) - chaptalisation concentrated unfermented grape juice use of sucrose is preferred, most neutral, cheapest, each kg increase wine volume by 0.63 kg.

63
Q

How much sugar is need to raise ABV by 1%

A

for white wine: 17 g/l to raise ABV by 1% for red wine: 19 g/l to raise ABV by 1% - higher level of evaporation at higher temp. of fermentation and in pumping over

64
Q

What is natural alcohol

A

total alcohol in un-riched must or wine

65
Q

This must concentration technique involves evaporating must under vacuum, water evaporates at 20 C, low temperature minimises loss of aromatic and flavor potential

A

Vacuum evaporation

66
Q

This must concentration technique is actually a filtration which take adventages of differences in molecular weight

A

Reverse osmosis. Concentrates flavors, acids, tannins.

67
Q

This must concentration technique replicates naturally frozen grapes on vine

A

Cryoextraction. controversial

68
Q

What must concentration technique can be used to remove alcohol and high levels of volatile acidity in finished wine

A

Reverse osmosis.

69
Q

De-acidification

A

Total acidity can not be reduced by more than 1 g/l, expressed as tartaric acid. malic acid (harsher of the two) levels fall more rapidly then tartaric during grape ripening, so high levels in cool climates where double-salt is justified. in most ripe grapes tartaric is the main acid so adjustments are made using carbonate salts.

70
Q

De-acidification using potassium bicarbonate

A

adition of potassium biacarbonate to must post-clarification but before alcoholic fermentation. this is preffered method of de-acidification. potassium batartrate crystals are formed. remove only tartaric acid.

71
Q

De-acidification using calcium carbonate

A

high level of calcium tartrate form, leaving juice tartrate unstable until all crystals have been deposited. remove only tartaric acid.

72
Q

De-acidification using double salt

A

adding calcium carbonate with small amount of calcium tartrate-malate (brand name Acidex) remove both tartaric and malic acids as crystals of calcium tartrate-malate are formed, which are insoluble.

73
Q

De-acidification using malolactic fermentation

A

reduce only malic acid.

74
Q

Natural de-acidification

A

through tartrate deposition after alcoholic fermentation.

75
Q

De-acidification correlation with pH

A

De-acidification increases pH, which increase risk of microbial infection and decrease effectiveness of SO2

76
Q

Acidification

A

decreases the pH of grape must or wine, which increases effectiveness of sulfur dioxide and inhibits the growth of bacteria. increasing levels of potassium salts can cause a decrease in pH even if titratable acidity is unchanged.

77
Q

Correlation between pH and color of red wines

A

in red wines pH affects the color of pigmented tannins low pH wines appear brighter, more blue/purple high pH wines appear duller, more garnet/brown

78
Q

Legal limits for acidification in EU

A

tartaric acid is used for acidification, add before fermentation legal limits 1.5 g/l in musts, 2.5 g/l in wines. limited to warmest zones CII and CIII

79
Q

Adding of citric acid to wine

A

it increase wine stability. never before fermentation, it can be metabolised by yeast and bacteria to form acetic acid, thus increasing volatile acidity. EU limit of total citric acid in wine is 1 g/l

80
Q

Adding tannins to wine

A

always prior to fermentation, can provide some protection from oxidation, can stabilise color, improve mouth feel

81
Q

Adding bentonite

A

form of clay, used as fining agent in white winemaking, removes dissolved proteins. it is non selective, also remove flavor compounds.

82
Q

Benefits of flavor and color enhancing enzymes

A

aid juice extraction optimise extraction of aroma precursors improve color extraction increase efficiency of settling They are added at crushing operations

83
Q

From what source have enzyme preparations been developed

A

from a diverse species of fungi (aspergillus, rhizopus and trichoderma)

84
Q

Oxygen

A

colorless, odourless gas, makes 1/5 of Earth atmosphere small amount during fruit processing is essential for development of yeast at start of fermentation

85
Q

What is result of larger oxygen exposure during fruit processing

A

can lead to oxidation of phenolics, causing browning in white musts, and loss of primary aroma compounds in both color musts. activity of two oxidases-enzymes that catalyse oxidation must be restricted: laccase and tyrosinase

86
Q

Laccase (oxidases-enzyme)

A

found in fruit affected by high levels of grey rot, responsible for more serious permanent browning of grape musts and wines and loss of aromatics

87
Q

Tyrosinase (oxidases-enzyme)

A

found in healthy grapes. controlled by adding SO2.

88
Q

Laccase (oxidases-enzyme) solution

A

resistant to SO2. pasteurisation (heating must to 65-70 C) but primary aromas and flavors also destroyed.

89
Q

What are inorganic oxidasic catalysts

A

include many metal ions, especially copper. for this reason copper and bronze are avoided in modern winery equipment

90
Q

Reductive or Anaerobic handling

A

minimise exposure to oxygen. SO2 is used during grape processing, temperatures are kept low, inert gases are used to flush out presses, pipes, vats.

91
Q

Why black grapes are less vulnerable to oxidation

A

because greater concentration of tannins and pigments.

92
Q

When is controlled oxygen exposure justified

A

for some varieties, such as chardonnay, controlled oxygen exposure prior to fermentation can lead to development of more complex aromas and flavors

93
Q

What is hyperoxidation

A

process where enzymatic oxidation of phenolics is encouraged, converting them to insoluble polymers which may be removed by clarification treatments and resulting wine is more stable.

94
Q

Name some possible negative changes due to excessive oxygen exposure

A

production of high level of acetaldehyde (ethanol) - flat sherry like flavor creation of bitter-tasting components from the oxidation of phenolics development of spoilage bacteria such as acetic bacteria.

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