Certified Specialist of Wine Study Guide Review

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CertifiedSpecialistofWineStudy Guide Review
Wine Compositionand Chemistry
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Overview

• Introduction
• What Is Wine?
• Sugars
• Acids
• Alcohols
• Phenolic Compounds
• Aldehydes
• Esters
• Sulfites

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Introduction

• Wines are extremely complex chemically
  (especially red wines) with hundreds of thousands
  of different chemical or molecular components
• Main Sources for these complex compounds are
• Compounds present in grapes that remain intact
  during fermentation and aging
• Compounds produced/created during fermentation
  and aging
• Compounds that come about during the wine making
  process largely due to addition of certain
  elementslike sulfur

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Introduction

• Outside of water, low levels of minerals and few
  dissolved organic gases almost everything else
  in wine is organic
• These organic compounds are primarily
  responsible for a wines
• Structure
• Color
• Odor
• taste/flavor

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What is Wine?

• Water 80 to 85
• Alcohol 8.5 to 15
• Ethyl Alcohol or Ethanol main product of
  fermentation
• Glycerol sweet alcohol accounts for 7 to 10 of
  total alcohol content. Higher in high sugar
  levels in must with high yeast populations
• Alcohol gives wine body and weight
• Warmth or heat is the key sensation of alcohol
• Alcohol should not dominate it should be
  integrated into the overall impression of the
  wine

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What is Wine?

• Acidity Ranges within Total Acidity (TA) and the
  Strength of the Acid (pH average 2.9 to 3.9)
• Tartaric acid
• Citric acid
• Malic Acid
• Fermentation acids
• Freshness
• Protects against bacterial damage and premature
  aging

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What is Wine?

• Esters (Aromas)
• The most important distinguishing feature of any
  wine
• Wine consists of over 200 different compounds,
  similar to those found in fruits, vegetables,
  spices, and herbs.
• These volatile essences are then carried by
  thousands of nerve endings to the brain. We
  actually smell flavors.
• 85-90 of what we taste is in what we smell.
• How many aromas can we be trained to identify?
• 1,000

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What is Wine?

• Sugar .2 to ?
• Wines are classified in different levels of
  sweetness.
• Dry No detectable sweetness
• Off dry White Zinfandel
• Medium dry German Kabinett
• Medium sweet Vouvray
• Sweet Trockenbeerenauslese Sauternes
• Calories per 5oz. Dry Red and White approx.100
  to 120
• Carbohydrates per 5oz.
• Dry White approx. 1g
• Dry Red approx. 2.3g
• (the sweeter the wine the higher the Carbs)

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Sugars

• Presence or absence of residual sugar in wine is
  a pivotal point
• Sugar in wine
• Provides balance for high acidity
• May hide a multitude of flaws such as bitterness
  or lack of extract
• Some wines depend on higher amounts of sugar (the
  phenomenon of white zinfandel is a good example)
  for their essential style and character

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Sugars

• Grape is 1528 sugar at harvest
• These sugars are
• Six-carbon sugars
• Fermentable glucose
• Fermentable fructose
• Five-Carbon Sugars (unfermentable sugars)
• Arabinose
• Xylose
• Rhamnose

These unfermentable sugars remain in the wine,
so even dry wine may have an average of 0.2
residual sugar in the wine this may be reflected
in the tech.data.
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Sugars

• Glucose and Fructose are present in roughly
  equal amounts in a grape
• However, the sweetness level is not on par
• Fructose is twice as sweet as glucose (although
  yeast ferments glucose at a faster rate than
  fructose)
• It is significant that there is always more
  fructose than glucose as fermentation progresses

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Sugars

• Winemakers can leave residual sugar in wine in
  two ways
• Arrest fermentation before sugar is converted
• Ferment to dryness then blend in unfermented
  grape juice (sussreserve in German) to achieve
  the desired level of sweetness
• When sugar/acid is in balance and two wines are
  of equal sweetness, arrested fermentation wine
  will taste sweeter than sussreserve wine
• Why?
• Because residual sugar from arrested fermentation
  is primarily fructose sussreserve has more
  glucose. Fructose is the sweeter of the two
  sugars

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Sugars

• Sucrose (table sugar) is a legal, though
  generally controlled, addition to grape must in
  chaptalization
• Chaptalization is to boost alcohol levels in must
  that has not achieved sufficient ripeness/sugar
  development
• Sucrose is metabolized during fermentation and
  should not be present in the finished wine
• If sucrose is present, that is a sure sign of
  fraudulent sugar addition

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Sugars

• Average Recognition Threshold for sugar is 1
• Average Perception of Sugar is between 0.52.5
• This explains how two different people can taste
  the same wine and and have totally different
  perceptions of the wine
• Their sugar perception thresholds are different.
• Residual sugar below recognition level fleshes
  out a wine and makes it appear more full-bodied
• In many low end wines sugar is used (literally)
  as a substitute for flavor

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Acidity

• Acidity Acidity ranges within Total
  Acidity (TA) and the Strength of the Acid (pH
  average 2.9 to 3.9)
• Tartaric acid accounts for ¼ of total acid and
  is the strongest harsh and hard with sour-salt
  character
• Malic Acid Most fragile, will breakdown in hot
  conditions. Lactic bacteria will convert it to
  lactic acid
• Citric acid present but not predominant in
  grapes
• Fermentation acids lactic, succinic and acetic
• Freshness Protects against bacterial damage
  premature aging
• White Wines tend to have higher acid levels than
  red wine (Port wines have some of the lowest acid
  levels)
• Wines low in acid can be considered flabby

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Alcohols

• Ethyl alcohol (ethanol) main product of
  fermentation
• Carrier of aroma and bouquet
• Most table wines average 1015 by volume
• Methyl alcohol occurs in very small amounts
• More significant in high-pectin fruit wines and
  macerated wines
• In large amounts methyl alcohol (wood alcohol) is
  toxic
• Glycerol alcohol with sweetness equiv. to
  glucose
• Less volatile and has higher viscosity than
  ethanol
• Glycerol normally represents 710 of total
  alcohol
• Fusel Oils (high alcohols)less than 0.1
• More toxic contribute to hangovers

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Alcohol and Wine Legs

• Wine Legs or Tears
• Water molecules have affinity and are cohesive
• When alcohol is added to water surface tension
  decreases
• Alcohol evaporates and water molecules rush
  back together and form tears or legs
• These are an indicator of ethanol and
  evaporation
• Slower the tears are, the higher the ethanol
  content
• With dessert wines, additional glycerin creates
  viscosity

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Phenolic Compounds

• Phenolic compounds play a variety of important
  roles in wine
• Pigments
• Anthocyanin in reds, flavones and flavonols in
  whites
• Tannins--astringency and bitterness, particularly
  red wine
• Antioxidants helping protect wine from oxidation
• Aid in longevity
• Anti-carcinogenic free-radical scavengers
• Responsible for sediment during aging
• Anti-microbial, anti-bacterial, anti-viral
  properties
• Odiferous
• Strengthening cardiovascular system (increasing
  good cholesterol/high-density lipoproteins
  (HDLs) and lowering bad cholesterol (LDLs)

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Phenolic Compounds

• Eugenol/guaiacol/vanillin
• Phenols that affect a wines flavor and aroma
  profile
• Resveratrol
• Affects HDL/LDL levels
• Brettanomyces (yeast) can be positive or negative
  as to its effect on wines, depending on the
  nature of the associated phenolics
• 4-Ethylphenolmedicinal and pungent
• 4-Ethylguaiacolbacon and smoky odors
• In general, most healthful effects attributed to
  wine are attributed to phenolic compounds, such
  asresveratrol and quercetin

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Aldehydes

• Oxidized alcohols formed when wine is exposed to
  air
• Greatest in maderized wines such as Madeira,
  Marsala, vin santo, and sherry
• Sherry considered the most aldehydic wines in
  the world

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Esters

• Largest group of odiferous compounds in wine
• Formed when alcohol bonds with carbolyxic acid
• Biochemical esters caused by chemical reactions
  during fermentation and require action of yeasts
• Fruity esters are volatile and lost from
  hydrolysis unless cold fermentation is used
• Esterification can diminish perception of acid as
  wine ages (although acid will remain the same)

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Sulfites

• SO2 and other sulfites are naturally produced
  during fermentation
• Sulfur dioxide also used in viticulture as
  anti-fungal
• Free or unbound SO2 is important to winemakers as
  it prevents microbial spoilage, browning and
  oxidation
• Sulfite use has lessened over the years as
  technology has improved
• Contains sulfites labeling exists as a warning
  to sulfur-sensitive asthmatics on wines
  containing more than 10ppm of sulfites.