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2023 CSW > Wine Composition and Chemistry > Flashcards

Wine Composition and Chemistry Flashcards

1
Q

What is wine?

A

Wine is the fermented product of grapes.

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2
Q

What are major components in wine?

A
  1. Water - 80-90%
  2. Alcohol 10-15%
  3. Acid 0.5 -0.75%
  4. Sugar 15-28%
  5. Phenolic Compounds - minor
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3
Q

What are other (minor) components in wine?

A

Yeast and proteins may be present in small concentrations in wines that have undergone extensive aging in contact with yeast cells (sure lie)

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4
Q

How much water is present in wines?

A

80%-90%

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5
Q

Where does the water in the wine originates from?

A

The water in wine is primarily from grapes. Uncommon practice is to add water intentionally to dilute grape juice or wine when potential alcohol, actual alcohol, or phenolic compounds are beyond desired level.

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6
Q

What is the second most prevalent component (ingredient) in wine?

A

Alcohol. Usually 10-15% of the volume.

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7
Q

What is the primary type of alcohol find in wine?

A

Ethyl alcohol or Ethanol

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8
Q

What is Ethyl Alcohol?

A

The primary result of alcohol fermentation and the main alcohol component in wine.

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9
Q

What are secondary types of alcohol?

A
  1. Glycerol
  2. Methyl Alcohol (methanol)
  3. Fusel Alcohols (fusel oils) or higher alcohols
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10
Q

What is Alcohol’s role in wine?

A

Alcohol is the intoxicating element in wine that distinguishes wine from grape juice. It is a compound that contributes to mouth filling, tactile sensation of a wine as it rests on the palate: This sensation is referred to s the wight or body.

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11
Q

What is the Ethanol quality / roll in the wine?

A

Ethanol (Ethyl Alcohol) is a volatile compound which means that evaporates easily. When it does, it carries the wine’s Aroma to the nose.

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12
Q

When are wines describe as “heavy” and when are wines described as “light”?

A

Wines with. higher levels of alcohol tend to be heavier in weight than wines with lower levels of alcohol.

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13
Q

What are “tears” or “legs” in wine?

A

Heavy levels of alcohol can result in slow, thick-appearing “tears” or “legs” in the glass after the wine is swirled.

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14
Q

What is the role of the ACID in wine?

A

Acid is the component that make wine unique. A variety of acids, especially in the white wines give the wine much of its STRUCTURE, BALANCE and THIRST QUENCHING REFRESHMENT.

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15
Q

How much ACID is usually present in wine?

A

ACID. usually make up between 0.5 - 0.75% of wine volume.

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16
Q

What are principal acids in present in wine?

A
  1. Tartaric Acid
  2. Malic Acid
  3. Citric Acid
  4. Lactic Acid
  5. Acetic Acid
  6. Succinic Acid
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17
Q

List are GRAPE acids?

A

The following acids are naturally present in grapes to a some degree
1. Tartaric acid
2. Malic acid
3. (Citric acid) *
4. (Succcinic acid) *

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18
Q

List FERMENTATION Acids?

A

The following acids are usually find in wine as fermentation by product
1. Lactic acid - created as by product during malolactic fermentation
2. Acetic Acid
3. Succinic Acid - minor component in grapes and by product of fermentation

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19
Q

What is the most prevalent acid found in wine?

A

TARTARIC Acid is the most prevalent of the acids found in grapes and wine. It is also the strongest in terms of PH.

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20
Q

What are TARTRATES?

A

Crystals known as “wine diamonds” are solid form of Tartaric acid created in low temperatures.

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21
Q

What is unique propensity of Tartaric acid?

A

Tartaric acid forms solid crystals known as “wine diamonds” at low temperatures.

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22
Q

Are tartrate crystals
(TARTRATES) a wine defect?

A

Tartrate crystals are not considered a defect in most wines. Formation of tartrates in bottle can be avoided or minimized by cold stabilization.

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23
Q

Can tartrates dissolve in wine?

A

No. Once tartaric acid takes this form it will not redissolve into the liquid, and the wine will become noticeably less acidic.

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24
Q

What is the by-product of the crystallization of tartaric acid?

A

Once the tartaric acid has crystalized and taken the solid form, the wine will become noticeably less acidic.

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25
Q

When do tartrates appear in wine? *Extra question

A

Tartaric acid’s solubility in wine is temperature-dependent. When a wine is chilled to temperatures below 40 degrees, the remaining tartaric acid will bind with the naturally occurring potassium in the wine to form crystalline deposits (potassium bitartrates), or tartrates

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26
Q

Can tartrates occur in white wine?

A

Yes. Tartrate crystals in white wine have been described as having a similar appearance to shards of glass or have been mistaken for unwanted or unnatural sediment – this is simply not the case. Though their appearance may be a bit off-putting, tartrates are completely harmless.

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27
Q

Why is Tartaric Acid important? *Extra question

A

Tartaric acid is arguably the most important in wine due to the prominent role it plays in maintaining the chemical stability of the wine, the wine’s color and influencing the taste of the finished product.
During the fermentation and barrel aging process, less than half of the tartaric acid present in a wine will settle out and bind with lees, pulp debris and precipitated tannins and pigments. Majority of the tartaric acid will remain soluble throughout the production process. The remaining tartaric acid present in a wine is the primary acid one tastes and is essential to the final mouthfeel and balance, adding an additional layer of complexity to a wine.

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28
Q

What is Malic Acid and why it is important?

A

Malic acid is one of three main acids found in wine grapes alongside tartaric, and citric acids. Each type of acid plays a key role in the wine production process and contribute different flavor profiles and textures to the end wine. Malic acid does contribute to the aromas of a wine, but it is more known for its role during the winemaking process through malolactic fermentation. In this process, the stronger malic acid is converted into the softer, smoother lactic acid.

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29
Q

What is the prevalent taste of Malic Acid?

A

Malic acid is a sharp-tasting acid frequently associated with green apples.

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30
Q

What type of grapes are typically hight in Malic Acid?

A

Underripe grapes and cool-climate grapes are typically high in malic acid. However, the level of malic cid decreases during the ripening phase of the grapes in wine.

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31
Q

Which wine has high an which one has low level of Malic acid?

A

Underripe grapes and grapes grown in cool climate will typically have high level of Malic Acid. Wines made from overripe grapes or grapes grown in hot climates tend to have relatively low levels of this acid.

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32
Q

What is Malolactic fermentation?

A

Malolactic fermentation is the process, in which the stronger malic acid is converted into the softer, smoother lactic acid.

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33
Q

Can formation of the tartrates be stopped?

A

Yes by winemaking process COLD STABILIZATION. Cold stabilization is the process of cooling the wine to around freezing temperatures in large stainless steel tanks for several days or weeks after the wine has aged and just before bottling. By cooling the wine prior to bottling, the potassium bitartrates will crystalize and drop to the bottom of the tank where they can then be filtered out of the wine. By doing this, the winemaker is ensuring that further tartrate crystals do not form in the bottle mainly for aesthetics reasons. However, at the same time, cold stabilization strips the wine of it acidity, takes away from its natural flavor profile and impacts the wine’s long-term ageability.

34
Q

Is Lactic acid normally found in grapes?

A

No. Lactic acid is not found in grapes, rather it is created in wine by lactic acid bacteria which convert malic acid in into lacti acid in the optional winemaking process known as malolactic fermentation.

35
Q

What is the quality/role of Lactic acid?

A

As lactic acid is less intensely acidic wines that undergo malolactic fermentation tend to be softer and smoother in mouthfeel than one that not. The byproduct of malolactic fermentation also provide wine with a creamy texture and in some cases buttery aroma.

36
Q

Can Lactic acid be created during primary fermentation?

A

Yes. Lactic acid is also created during primary fermentation although in very small amounts.

37
Q

What is Acetic Acid?

A

Acetic acid is a two-carbon organic acid produced in wine during or after the fermentation period. It is the most volatile of the primary acids associated with wine and is responsible for the sour taste of vinegar.

38
Q

What does Acetic Acid contributes to in wine?

A

Being highly volatile acetic acid will readily evaporate and join the aromas of the wine, adding to the complexity of the wine’s bouquet, particularly in red wines.

39
Q

When will high level of Acetic acid appear in wine?

A

During fermentation, activity by yeast cells naturally produces a small amount of acetic acid. If the wine is exposed to oxygen, Acetobacter bacteria will convert the ethanol into acetic acid. This process is known as the “acetification” of wine and is the primary process behind wine degradation into vinegar.

40
Q

What is Succinic acid?

A

Succinic acid is one of the relevant organic acids in wine (and a byproduct of ferementation), whose main role is to confer microbial stability to wines in relation to acidity and pH. They also preserve the colour and sensory properties of wines.

41
Q

What does Succinic acid taste like?

A

Succinic acid has a sharp, slightly bitter, slightly salty flavor.

42
Q

What is the role of Tataric acid? *Extra question

A
  1. TARTARIC Acid - Tartaric acid helps to control the acidity of the wine and is considered as one of the strongest acids in wine. It also plays a crucial role in enhancing the taste, feel, and color of wines. It also reduces the pH to kill the undesirable bacteria, thereby acting as a preservative.
43
Q

What is the role of Malic Acid? *Extra question

A

Malic Acid is one of the main acids found in the acidity of grapes. Its concentration decreases the more a grape ripens. Malic Acid provides a strong link to wines tasting ‘flat’ if there is not enough. If there is too much the wine will taste ‘sour’

44
Q

What is the role of Succinic acid? *Extra question

A

Succinic acid is one of the relevant organic acids in wine, whose main role is to confer microbial stability to wines in relation to acidity and pH. They also preserve the colour and sensory properties of wines.

45
Q

What is the role of Lactic acid? *Extra question

A

Lactic acid is an organic acid that is a principle acid in wine. Lactic acid is responsible for reducing the acidity of wines, providing a smoother flavour.

46
Q

What is the role of Acidic acid in wine? *Extra question

A

It adds a sharpness to the flavours and is detected most readily by a prickling sensation on the sides of the tongue and a mouth-watering aftertaste. Acetic acid is a two-carbon organic acid produced in wine during or after the fermentation period.

47
Q

What is TA?

A

Total acidity (TA) is the volume of all the acids in the wine. In general more acid equates to more acidic taste. TA includes several different acids.

48
Q

What is PH ?

A

The Ph level of wine represents the combined chemical strength of the acids presents.

49
Q

What is the Ph scale for the wine?

A

The wine usually measures between 2.9 and 3.9 on the logarimich Ph scale. A LOWER PH scale indicates STRONGER acid content. Wine will 2.9 ph will be more acidic than 3.4 ph wine.

50
Q

Why is Acidity in wine important?

A

Acidity is an essential component of any wine’s profile, and it greatly influences overall perception. If the pH is higher, the wine will be softer and rounder, and if the pH is lower, it will feel more linear. Total acidity tells us the concentration of acids present in wine, whereas the pH level tells us how intense those acids taste.

To get a complete picture of wine acidity you need to know TA and PH levels.

51
Q

Why is PH level important?

A

Winemakers place particular emphasis on Ph as it gives an indication of stability and plays a role in determining sulfur additions. pH is a major contributor to the following factors in wine: 1) microbial stability, and 2) color stability.

52
Q

What are major sugars in grape?

A

Glucose and fructose are the main sugars in the grapes.

53
Q

How much sugar does grape typically contains.

A

Grapes typically contains 15%-28 % sugar at harvest. More specifically grape contain roughly equal amount of two sugars: Glucose and fructose.

54
Q

What are simple sugars?

A

Glucose and fructose are both highly fermentable monosaccharides, commonly known as “simple sugars”

55
Q

What happens during fermentation?

A

During fermentation yeast converts sugars into ethanol turning grape juice into wine.

56
Q

What are level of sweetness in wine?

A
  1. Bone Dry - Less than 1g/L
    White and red blends, Cabernet Sauvignon
  2. Dry 1-10g/L residual sugar - Pinot Noir, Shiraz, Gamay, Chardonnay, Sauv Blanc
  3. Off Dry - 10-25g/L
  4. Medium 25-45g/L
  5. Sweet - 45-120g/l *Moscato, Asti, Moscato di Asti, Ruby and Tawny port
  6. Dessert 120 - 220 g/L - Sauternes, Late Harvest, Spatlese
57
Q

What is the role of sweetness in wine?

A

In small amounts can be used to balance high acidity in wines, and in some low quality wines sweetness can be used to hide wine flaws.

58
Q

What are Phenolic Compounds in wine?

A

The phenolic content in wine refers to the phenolic compounds—natural phenol and polyphenols—in wine, which include a large group of several hundred chemical compounds that affect the taste, color and mouthfeel of wine. These compounds include phenolic acids, stilbenoids, flavonols, dihydroflavonols, anthocyanins, flavanol monomers (catechins) and flavanol polymers (proanthocyanidins).

Phenolic acids are largely present in the pulp, anthocyanins and stilbenoids in the skin, and other phenols (catechins, proanthocyanidins and flavonols) in the skin and the seeds.

59
Q

What are anthocyanins?

A

Anthocyanins, also known as anthocyans, are water soluble flavonoid pigments that, depending on pH, and in some cases complexing agents, can contribute diverse colors such as red, purple and blue

Color is one of the most important attributes of red wines, and the principal sources of red color in wines come from. Normally, anthocyanins are mainly located in the grape skins, with a few exceptions, in the so-called “teinturier” grapes, which have anthocyanins in both of the skin and the pulp.

60
Q

What are Flavonols?

A

Flavonols constitute a group of flavonoids that vary in colour from white to yellow and are closely related in structure to the flavones.
These yellow pigments are found in white wines. Flavanols (flavonets) increase in grapes with exposure to sunlight, therefore white wines from sunnier climates tend to have more golden color than wines from cooler climate.

61
Q

What are Tannins?

A

Tannins are astrigent, bitter compounds found in the skins, seeds and stems of grapes. They are also found in oak and oak barrels. These compounds form part of the structure or “backbone” of big red wines.

62
Q

What is the role of Tannins?

A

Tannins are a natural preservative and help to protect red wines from oxidation during the aging process.

63
Q

What is Vanilllin in wine?

A

A compound in oak barrels that is ultimately imparted to wine as a flavor and smell reminiscent of vanilla beans.

64
Q

What affects level of vanillin?

A
  1. Species of the oak
  2. Age and size of the barrel
  3. Level of seasoning used in preparation of the barrel and the age

New barrels have more vanillin than older barrels, and hence wine stored in new barrels has a more pronounced vanilla character. In general the level of vanillin increases (as compared to raw oak) with light to medium toast levels and may decrease with the use of heavier levels of toast.

65
Q

What is resveratrol?

A

A polyphenol called resveratrol is one substance in red wine that’s received attention for its health benefits.

66
Q

Where can phenolic be find in grape?

A

The natural phenols are not evenly distributed within the fruit. Phenolic acids are largely present in the pulp, anthocyanins and stilbenoids in the skin, and other phenols (catechins, proanthocyanidins and flavonols) in the skin and the seeds. During the growth cycle of the grapevine, sunlight will increase the concentration of phenolics in the grape berries, their development being an important component of canopy management. The proportion of the different phenols in any one wine will therefore vary according to the type of vinification. Red wine will be richer in phenols abundant in the skin and seeds, such as anthocyanin, proanthocyanidins and flavonols, whereas the phenols in white wine will essentially originate from the pulp, and these will be the phenolic acids together with lower amounts of catechins and stilbenes. Red wines will also have the phenols found in white wines.

67
Q

Phenolic in white vs red wines

A

The phenolics of a grape are concentrated primarily in skin and seeds. Because of this red wines which are fermented in contact with grape solids are much richer in phenolic compounds than white wines.

68
Q

What happens to phenolic compounds over time?

A

Over time phenolic compounds, particularly tannins and pigments tend to polymerize or combine into longer molecule structure. These heavy chains eventually become too heavy and drop out of the oslution as sediment. This development has a major impact on the flavor of the wine and its is one of the main results of aging process. In many cases, the production of sediment in a properly aged wines renders a wine lighter in color and less astringent.

69
Q

What are other components in Wine ?

A
  1. Aldehydes
  2. Esters
  3. Disolved gases
  4. Sulfates
70
Q

What are Aldehydes?

A

Aldehydes are oxidized alcohols that are formed when wine is exposed to air.

71
Q

What is maderization?

A

Maderisation is a process that involves the heating and oxidization of a wine through which the formation of aldehydes is encouraged. The term is named after the process used in the production of Madeira wine, where it occurs while the wine is in cask. The resulting wine darkens in color and acquires a Sherry-like character. Outside Madeira wine, it is generally seen as a wine fault, but is desirable in the case of certain dessert wines where it occurs over the course of long bottle aging.

72
Q

What is the most common Aldehyde in wine?

A

Acetaldehyde (or ethanal) is the most important volatile wine carbonyl compound and can be formed both biologically (through yeast activity) and chemically (by wine oxidation- oxidation of ethanol) . It is a small and highly reactive molecule with a green grass, apple-like or nutty aroma. It is very volatile and flavour active with a sensory threshold of approximately 100 mg/L in table wines, and chemically very reactive. Acetaldehyde contributes to the distinctive aroma of fino Sherry .

73
Q

What are Esters?

A

Esters are formed when alcohols, including ethanol, the primary alcohol created by fermentation of grape sugars, react with organic acid molecules that are either native in the grapes or created during fermentation.

74
Q

Why are Esters important for wine?

A

Esters can contribute positively to the aroma of a wine. In low concentrations these compounds are perceived as generically fruity or floral and can boost the awareness of the innate fruit and floral characteristics of the grape varietal. However if they are present in too high of a concentration may be off putting. As with some of the sulfur compounds, low concentrations are desirable, high concentrations may negatively impact the wine.

75
Q
A

There are two classes of esters formed in wine the ethyl esters and the acetate esters. Esters derive from the combination of an alcohol with an acid. The most common acyl-CoA molecule found in yeast is acetyl-CoA and thus the most common esters are acetate esters. At low concentrations esters can add complexity to a wine and due to their generic floral and fruity notes enhance the aroma characteristics of the varietal. High concentrations of esters can be objectionable depending upon the matrix of the wine and impart aromas of nail polish remover, varnish or glue. Wines containing more than 90 mg/L of ethyl acetate or 200 mg/L of total esters are considered defective.

76
Q

What are the most important dissolved gases in wine and what is their impact.

A

Dissolved gases (oxygen and carbon dioxide) have a significant impact on the perceived quality of the wine.

77
Q

What is the impact of dissolved oxigen in wine?

A

Dissolved Oxigen promotes many chemical reactions through the process known as oxidation. While it may be beneficial in some wines, it can also be damaging. Thus winemakers try to avoid air exposure and often add sulfur to absorb any free oxigen molecules before they can harm the wine.

78
Q

What is the impact of dissolved CO2 in wine?

A

This is gas that gives bubbles to sparkiling wine. C02 is a natural by product of fermentation. Small amounts are present even in still wines and some winemakers leave enough co2 to create a bit of petillance (slight bubbling udner surface) . C02 in wine keeps a wine feeling fresh and lively in the mouth and promotes the release of wine aromatic compounds.

79
Q

What are sulfates?

A

Sulfates are a class of chemicals that are based on element of sulfru. Sulfur is an important preservative that is widely used to keep wines stable after fermentation. Therfore all wines contain at least trace of sulfates.

80
Q

What is sulfur?

A

Sulfur is antioxidant and antibacterial agent. Producing wine without addition of sulfur is challenging.

81
Q

What are the legislation in USA for sulfur?

A

In USA the wine that contain more than 10 parts per million ppm of sulfur dioxide is required to display the “Contains sulfites: warning on the label.

2023 CSW (1 decks)

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