Wine Composition & Chemistry Flashcards
What “wine” means legally in the US
4 aspects of grapes that make them ideal for winemaking
a beverage made from grapes.
grapes have the most valued combination of
1) fermentable sugars
2) significant acidity
3) desirable flavors
4) liquid content
5 major components of wine
3 other components that may be present
Water Alcohol Acid Sugar Phenolic
bacteria
yeast
proteins
% of wine that is water
3 sources of water in wine, with primary first and rarest last
Why the last source is performed
80–90% water
1) from the grapes themselves
2) small amounts of water may be added incidentally during winemaking.
3) intention addition of water
to dilute grape juice or wine when potential alcohol, actual alcohol, or phenolic compounds are beyond desired levels.
What is the most prevalent ingredient in wine after water
Usual percentage of it in wine by volume, with caveat
Specific type of this ingredient (scientific name)
alcohol
10–15%
Ethyl alcohol
AKA for ethyl alcohol
Process it is a product of
3 other kinds of alcohols that occur in smaller amounts
ethanol
alcoholic fermentation
glycerol methyl alcohol (or methanol) fusel alcohols (fusel oils) or higher alcohols.
What does volatile mean when used to describe ETOH
What olfactory quality these lends to wine
What tactile sensation ETOH lends to wine, with term used to describe it (2)
Note about ETOH and wine weight
Visual sign of high alcohol content in wine
it evaporates easily
it carries the wine’s aromas to the nose.
contributes to the mouth-filling, tactile sensation of a wine as it rests on the palate; this sensation is often referred to as a wine’s “weight” or “body.”
Wines with higher levels of alcohol tend to be heavier in weight than wines with lower levels of alcohol, all other things being equal.
slow, thick-appearing “tears” or “legs” in the glass after the wine is swirled.
6 kinds of acids found in wine, with most prevalent first
Tartaric Malic Citric Lactic Acetic Succinic
General wine type in which acid can make the most difference
3 things that a variety of acids can lend to wine
% of wine in volume made up by acids
white wines
structure
balance
thirst-quenching refreshment
0.5% and 0.75%
2 places where tartaric acid is the most prevalent acid
2 unique properties of tartaric acid
Name for second phenomenon
in both grapes and grape juice/wine
1) It’s the strongest in terms of pH.
2) It forms solid crystals at low temperatures.
“wine diamonds”
Note about tartaric acid “wine diamonds,” with result
Are wine diamonds considered a defect?
How they can be avoided or minimized in the winemaking process
They will not redissolve into the liquid, and the wine will become noticeably less acidic.
Not technically
cold stabilization
Taste of malic acid, and what it is often associated with
Two types of grapes typically high in malic acid
How malic acid decreases
2 types of wine that are low in levels of malic acid
How to reduce malolactic fermentation in wine
sharp-tasting; green apples.
1) Underripe
2) cool-climate grapes
during the ripening phase of the grapes on the vine.
1) Wines made from overripe grapes
2) grapes grown in hot climates
malolactic fermentation.
Note about prevalence of citric acid in wine
Usual impact of it on wine
Why it is sometimes added, but usually not
Citric acid is not usually considered to be a normal component of grapes, as it exists in such minute quantities that specialized equipment is required to measure it.
It has no sensory impact on the majority of wines.
to increase the total acidity in a wine, although its distinctive citrus fruit flavor makes it generally unsuitable for quality wines.
Is lactic acid usually found in grapes?
Process by which it’s created in wine, with chemical description
How wines that undergo this process taste, and why
A second taste by-product of this process
Another way lactic acid is produced in small amounts in wine
No
Through malolactic fermentation, where lactic acid bacteria convert malic acid into lactic acid
by lactic acid bacteria, which convert malic acid into lactic acid in the optional winemaking process known as malolactic fermentation.
They taste softer and smoother in mouthfeel because lactic acid is less intensely acidic than malic acid
Provides wine with a creamy texture and, in some cases, a “buttery” aroma.
during primary fermentation, albeit in very small amounts.
In what substance acetic acid is often found
What process in winemaking produces a low level of it in wine
Special quality of acetic acid compared to other wines, with benefit of this quality and wine time in which this quality is most prevalent
How high levels of acetic acid can appear in wine, potentially making it undrinkable
vinegar
fermentation
It is volatile, so it readily evaporates and joins the aromas of the wine, adding to the complexity of a wine’s bouquet, particularly in red wines.
chemical reaction between between ethanol and oxygen caused by harmful (to wine) bacteria called acetobacter
Nature of role of succinic acid in wine and how it appears in wine
Describe its taste (3)
a minor component, a by-product of normal alcoholic fermentation.
sharp, slightly bitter, slightly salty flavor.
4 grape acids
3 fermentation acids
Tartaric
Malic
Citric
Succinic
Lactic
Acetic
Succinic
Two numbers used to describe the acidity level of wine, with definitions, and why second is used more
1) total acidity (TA), which is the volume of all the acids in a wine.
2) The combined chemical strength of all acids present
In general, more acid equates to a more acidic taste. However, TA includes several different acids, some of which are stronger than others.
Is a lower pH more or less acidic than a higher pH?
Usual pH of wine
Why winemakers place particular emphasis on pH while looking at both numbers (2)
Lower pH is stronger
2.9 and 3.9
PH gives an indication of stability and plays a role in determining sulfur additions.
% of sugar in wine grapes at harvest
Two types of sugars contained in roughly equal amounts in grapes
Chemical type of these sugars with aka
Quality of these sugars in relation to winemaking
15% to 28%
monosaccharides, commonly known as “simple sugars.”
They are highly fermentable
Chemical reaction that occurs with glucose and fructose under the right conditions
What will result if the process is allowed to go to completion
What even such a fermented product will contain, and why, and concentration of these
yeast converts these sugars into ethanol, turning grape juice into wine.
the wine will be fermented to dryness
even dry wines contain a trace amount of sugar, as grapes actually contain tiny quantities of unfermentable sugars. These unfermentable sugars generally remain in concentrations below one’s ability to detect them.
Define the term “dry”
Why some wines have detectable sugar
2 qualities that residual sugar adds to wine
Wines that have less sugar than a person can taste are described as dry.
because fermentation was stopped, through winemaker intervention or by natural causes, before all of the sugar was converted to alcohol.
1) adds some weight, or “body,” to the wine
2) contributes to slow, thick-appearing tears in the glass after a wine is swirled
3 roles (examples) that sugar can play in wine, with % example for first
1) renowned dessert wines are extremely sweet, even up to 24% or more residual sugar
2) sweetness is used to balance high acidity in a wine, or vice versa.
3) In some lower-quality wines, sweetness may be used to hide the wine’s minor flaws.
5 primary phenolics found in wine
2 AKAs for phenolics
Anthocyanins Flavonols Tannins Vanilin Reservatrol
Polyphenolics
Polyphenols
What anthocyanins do for wine, with note on range
2 things that influence this property, with note on influence of non-anthocyanin component
give red wine its color, which in fact ranges from blue to purple to red.
amount of anthocyanins
acidity level of the wine
more acidic wines appear redder in hue, while less acidic ones appear bluer.
