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Certified Specialist of Wine (2020) > Ch 1: Wine Composition + Chemistry > Flashcards

Ch 1: Wine Composition + Chemistry Flashcards

- Recognize the main categories of chemical compounds in wine - Identify the approximate concentrations of the major components of wine. - Describe specific types of alcohols, acids, and sugars that are most prominent in wine. - Discuss the types of phenolic compounds that are important in wine.

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1
Q

What is the most simple definition of wine?

A

The fermented product of grapes.

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2
Q

What is a scientist’s definition of wine?

A

A complex blend of chemicals that collectively give the liquid its visual, olfactory, and tactile characteristics.

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3
Q

Why does wine have an ever changing character?

A

Chemical reactions expand and evolve over time. Some concentrations of compounds increase and others decrease.

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4
Q

What inevitably happens to all wines with sufficient time?

A

Nearly all wines are overcome by undesirable components as chemical reactions reach their final stages.

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5
Q

What are the 5 major components of wine?

A
  1. Water (80 - 90%)
  2. Sugar
  3. Alcohol (10 - 15%)
  4. Acid (0.5 - 0.75%)
  5. Phenolic compounds
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6
Q

What percentage of a wine’s volume is made up of water?

A

80 - 90%

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7
Q

Why would a winemaker intentionally add water to wine during the winemaking process?

A

To dilute wine when potential alcohol, actual alcohol, or phenolic compounds are beyond desired levels.

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8
Q

What percentage of a wine’s volume is made up of alcohol?

A

10 - 15% (typically)

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9
Q

What is ethyl alcohol (ethanol)?

A

The principal alcohol found in wine and the primary result of alcoholic fermentation.

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10
Q

True or false:

Ethanol is a volatile compound.

A

True

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11
Q

What is a volatile compound?

A

A compound (such as ethanol) prone to evaporation and carries the wine’s aromas to the nose.

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12
Q

What are the 3 non-principal types of alcohol that occur in wine?

A
  1. Glycerol
  2. Methyl alcohol (mentanol)
  3. Fusel alcohols (fusel oils or higher alcohols)
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13
Q

What is alcohol’s effect on the palette?

A

Weight or body (the mouth-filling, tactile sensation)

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14
Q

Wines with ____ levels of alcohol tend to be ____ in weight. Wines with _____ levels of alcohol tend to be ____ in weight.

A

Wines with HIGHER levels of alcohol tend to be HEAVIER in weight. Wines with LOWER levels of alcohol tend to be LIGHTER in weight.

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15
Q

What are ‘tears’ or ‘legs’?

A

Streaks produced by viscous droplets of liquid that run slowly down the interior of a glass of wine after swirling.

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16
Q

What contributes to slow, thick-appearing tears (legs) when the wine is swirled?

A

High levels of alcohol

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17
Q

What percentage of a wine’s volume is made up of acid?

A

0.5 - 0.75%

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18
Q

What are the 6 principal acids in wine?

A
  1. Tartaric
  2. Malic
  3. Citric
  4. Lactic
  5. Acetic
  6. Succinic
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19
Q

Which of the 6 principal acids in wine are derived from fermentation?

A
  1. Lactic acid
  2. Acetic acid
  3. Succinic acid
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20
Q

Which principal acids can be found in grapes?

A
  1. Tartaric acid
  2. Malic acid
  3. Citric acid (in trace amounts)
  4. Succinic acid (in trace amounts)
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21
Q

What is acid’s effect on wine?

A

Acids give wine much of its:

  • structure
  • balance
  • thirst-quenching refreshment
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22
Q

What is the most common acid in grapes and wine?

A

Tartaric acid

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23
Q

Which is the acid with the strongest pH?

A

Tartaric acid

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24
Q

What is a tartrate?

A

A crystalline compound that is formed when wine contains more tartaric acid than it can retain in a dissolved state (particularly when the wine is chilled)

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25
Q

What is the proper name for a wine diamond?

A

A tartrate

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26
Q

What effect do wine diamonds have on a wine?

A

The tartaric acid will not re-dissolve into the liquid and the wine becomes noticeably less acidic.

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27
Q

True or false:

Tartrates (wine crystals) are considered a defect in most wines.

A

False

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28
Q

Which winemaking process can minimize tartrate formation?

A

Cold stabilization

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29
Q

What is malic acid?

A
  • Moderately strong acid
  • Sharp, green apple taste
  • Found in unripe and cool-climate grapes
  • Primary input to malolactic fermentation
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30
Q

True or false:

Malic acid decreases as grapes ripen.

A

True

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31
Q

Which winemaking technique can assuage high levels of malic acid?

A

Malolactic fermentation

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32
Q

What is citric acid?

A
  • Minor acid
  • Found in grapes in trace amounts
  • Sometimes used for acidification
  • Not considered appropriate for quality wines
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33
Q

Why is citric acid considered inappropriate for quality wines?

A

It’s distinctive citrus fruit flavor

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34
Q

True or false:

Citric acid has no sensory impact on the majority of wines.

A

True

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35
Q

What is lactic acid?

A
  • Mild acid
  • Not found in grapes
  • Created primarily via malolactic fermentation
  • Note: Very small amounts are created during primary fermentation
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36
Q

How is lactic acid created?

A

Lactic acid bacteria is converts malolactic acid into lactic acid during malolactic fermentation.

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37
Q

True or false.

Lactic acid is more intensely acidic than malic acid.

A

False

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38
Q

What is lactic acid’s effect on the palette?

A

Creamy texture, buttery aroma

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39
Q

What is acid?

A

The class of chemical compounds that produce a tart, sharp, or biting character in wine

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40
Q

How is acetic acid created?

A

Created during fermentation by a specific bacteria (acetobacter) when wine is oxidized or exposed to air.

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41
Q

True or false:

High concentrations of acetic acid is considered a fault.

A

True

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42
Q

What is acetobacter?

A

The type of bacteria that may cause wine spoilage in the presence of oxygen by producing acetic acid.

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43
Q

Which acid is found in most types of vinegar?

A

Acetic acid

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44
Q

Which acid is volatile (and therefore adds complexity to a wine’s bouquet)?

A

Acetic acid

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45
Q

What is acetobacter’s effect on wine?

A

Can make a wine unpleasant and undrinkable

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46
Q

What is succinic acid?

A
  • Sharp, slightly bitter, slightly salty flavor
  • Minor component in grapes
  • By-product of normal alcohol fermentation
47
Q

Which acid has a sharp, slightly bitter, slightly salty flavor?

A

Succinic acid

48
Q

Which two numbers are used to describe the acidity level of a wine?

A

Total acidity (TA) and pH

49
Q

What is total acidity?

A

A measure of the quantity of all the acids in a wine, usually in grams per liter (g/L)

50
Q

What is pH?

A

A measure of the strength of an acid or of an acidic solution such as wine.

51
Q

In general, ____ acid equates to a ____ acidic taste.

A

In general, MORE acid equates to a MORE acidic taste.

52
Q

What is the typical pH level of wine?

A

2.9 - 3.9

53
Q

A ______ pH indicates a _____ acid content.

A

A LOWER pH indicates a STRONGER acid content.

54
Q

True or false:

A wine with a pH of 3.4 is more acidic than a wine with a pH of 2.9.

A

False

55
Q

Why do winemakers emphasize total acidity (TA)?

A

pH gives an indication of stability and plays a role in determining sulfur additions.

56
Q

Which acid exists in such minute quantities that it requires specialized equipment to measure it?

A

Citric acid

57
Q

What percentage of sugar do grapes contain at harvest?

A

15 - 28%

58
Q

Which two sugars do grapes contain equal amounts of?

A

Glucose and fructose

59
Q

True or false:

Glucose and fructose are both highly fermentable monosaccharides (simple sugars).

A

True

60
Q

What happens to sugar during fermentation?

A

Yeast converts sugars into ethanol (alcohol).

61
Q

How is a wine fermented to dryness?

A

When the yeast is able (or allowed to) convert all the sugars into alcohol.

62
Q

True or false:

There is no trace of sugar in dry wines.

A

False

63
Q

True or false:

Grapes contain tiny quantities of unfermentable sugars.

A

True

64
Q

True or false:

The human palette can detect unfermentable sugars.

A

False

65
Q

What indicates a dry wine?

A

Wines that have less sugar than a person can taste.

66
Q

What are the 4 levels of wine sweetness?

A
  1. Dry
  2. Off-dry (medium dry)
  3. Medium sweet
  4. Sweet
67
Q

What is residual sugar’s effect on the palette?

A

Typically: weight and viscosity

For sweet wines: mouthfeel, body, and texture

68
Q

True or false:

Some of the world’s most renowned dessert wines contain up to 24% residual sugar.

A

True

69
Q

What is sweetness used to balance in wine?

A

Acidity

70
Q

True or false:

Low quality wines sometimes use sweetness to hide the wine’s flaws.

A

True

71
Q

What are phenolic compounds?

also called phenolics, polyphenols, or polyphenolics

A

A class of complex carbohydrate molecules often responsible for certain organoleptic properties and other aspects of wine.

72
Q

Phenolics occur in _____ quantities, and have a ____ impact on the sensory profile of a wine.

A

Phenolics occur in MINOR quantities, and have a MAJOR impact on the sensory profile of a wine.

73
Q

What are the 5 most common phenolics found in wine?

A
  1. Anthocyanins
  2. Flavonols
  3. Tannins
  4. Vanillin
  5. Resveratrol
74
Q

What are anthocyanins?

A

A type of pigment found in plants that gives grapes and wine a blue, purple, or red coloration.

75
Q

More acidic wine appears ____ in hue, less acidic wine appears ____ in hue.

A

More acidic wine appears REDDER in hue, less acidic wine appears BLUER in hue.

76
Q

What phenolic compound gives red wine its color?

A

Anthocyanin

77
Q

What is a flavonol (flavones)?

A

A phenolic compound found in plants that gives grapes a yellow coloration.

78
Q

White wines from ____ climates contain ___ flavonols (and therefore golden color).

A

White wines from SUNNIER climates contain MORE flavonols (and therefore) golden color.

79
Q

True or false:

Flavonols decrease with increased exposure to sunlight.

A

False. Flavonols increase with increased exposure to sunlight

80
Q

What are tannins?

A

A phenolic compound found in grapes that gives wine a somewhat bitter taste and distinctive mouth-drying feel.

81
Q

True or false:

Tannins are found in oak and oak barrels.

A

True

82
Q

What are tannins’ effect on the palate?

A
  • Somewhat bitter taste
  • Textural, drying sensation in mouth
  • Forms part of the structure of a red wine
83
Q

How do tannins act as a preservative?

A

Tannins help to protect wines from oxidation during the aging process.

84
Q

Which phenolic compound is aromatic?

A

Vanillin

85
Q

True or false:

Vanillin impacts a vanilla scent to barrel-aged wines.

A

True

86
Q

True or false:

Resveratrol has negative effects on human health.

A

False

87
Q

Where are the phenolics of a grape concentrated?

A

Grape skin and seeds.

88
Q

Which type of wines are richer in phenolic compounds?

A

Red wines

89
Q

What happens when phenolic compounds polymerize?

A

Phenolic compounds combine into longer molecule chains that become too heavy to stay suspending in liquid and drop out of the solution as sediment.

90
Q

Whic phenolic compounds polymerize most frequently?

A

tannins, anthocyanins, and flavonols

91
Q

What impact does the polymerization of phenolic compounds have on wine?

A

Major impact on the flavor of the wine and is one of the main results of the aging process.

92
Q

What does new research suggest about the polymerization of tannins?

A

Research suggests polymerized tannins can possibly continue to alter in structure and may eventually break down during extended aging. This means it may be impossible to predict how tannins in a well-aged wine will be perceived by tasters.

93
Q

What is an aldehyde?

A

Any of several chemical compounds caused by the oxidation of wine.

94
Q

Which wines are made using techniques that encourage aldehyde formation?

A

Sherry and Madeira

95
Q

True or false:

Any wine will take on a maderized character is it has been exposed to excessive oxygen during production or storage.

A

True

96
Q

What are two ways your wine can become oxidized at home?

A
  1. Keeping a bottle open for too long

2. Exposing a bottle to heat

97
Q

What is the most common aldehyde?

A

Acetaldehyde

98
Q

What is acetaldehyde?

A

The most common aldehyde, formed by the oxidation of ethanol.

99
Q

What effect does acetaldehyde have on Sherries?

A

It gives Sherries their distinctive aroma

100
Q

What are esters?

A

Any of various chemical compounds that result from the joining of an acid and an alcohol.

101
Q

What represents the largest group of odiferous compounds?

A

Esters

102
Q

True or false:

Esters are considered undesirable at low concentrations.

A

False. Esters are considered desirable at low concentrations.

103
Q

What is the most common ester?

A

Ethyl acetate (the ester of acetic acid and etholic)

104
Q

What effect does ethyl acetate have on a wine?

A

In low concentrations: fruity, flowery aroma

In high concentrations: aroma of nail polish remover, varish, or glue

105
Q

What is oxidation?

A

Chemical changes that take place in the presence of oxygen

106
Q

How do winemakers avoid oxidation?

A

Add sulfur to absorb any frere oxygen molecules

107
Q

What gives wine it’s bubbles?

A

Carbon dioxide

108
Q

True or false:

Carbon dioxide is a natural by-product of fermentation.

A

True.

109
Q

True or false:

Still wines contain no trace of carbon dioxide.

A

False. Small amounts of carbon dioxide are present even in still wines.

110
Q

What is petillance?

A

A slight bubbling under the surface when the wine is poured, created by leaving enough carbon dioxide in the wine.

111
Q

What effect does carbon dioxide have on wine?

A
  • Keeps wine feeling fresh and lively

- Promotes the release of the wine’s aromatic compounds

112
Q

What is the purpose of sulfur?

A

To act as an antioxidant and antibacterial agent to keep wines stable after fermentation.

113
Q

True or false:

All wines contain at least trace amounts of sulfites.

A

True.

All wines contain at least trace amounts of sulfites even if no sulfur is added during winemaking.

114
Q

When are wines destined for US commerce required to display a “Contains Sulfites” warning?

A

When wines contain more than 10 part per million (ppm) of sulfur dioxide.

Certified Specialist of Wine (2020) (3 decks)

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