Midterm Flashcards
The intensity of a sensory perception in wine is?
the concentration of the stimulus above the recognition threshold
The color of the wine depends on…
- The type & rate of combination among pigments.
- Grape variety (pigment fingerprinting)
- The age of the wine
The EQUILIBRIUM of SO2 in wine depends on…
pH ONLY
Marangoni’s effect is due to modification of water surface tension by
Ethanol content
The amount of CO2 diversifies the wine as…
Sparkling (>3 Bars)
not Medium sparkling (200-800mg/L) or
Still (1-2,5 bars)
This is because Still wines are at 200-800 mg/L (pay attention to units)
Olfactory Perceptions may be…
From grape variety, fermentation, fining and aging
Metallic perception is…
Due to exceeding iron and copper (which are oxidizing agents)
It is not produced by salts and is not always favorable
Minerals in wine give rise to…
Salified acidity at chemical measurement AND minerality at sensory evaluation NOT Umami perception
According to the classification into families, which is the main perception for fermentative aroma compounds?
Fruitiness (esters) AND solvent-like flavors (higher alcohols) NOT spiciness
The residual sugar level is used to classify still wines both for sensory analysis and for labeling. Among the following, which is the main sugar contained in this remaining fraction?
FRUCTOSE.
-not sucrose
-and not glucose because glucose is eaten directly during Glycolysis
Which are the main aromas contained in a bottle of Muscat wine?
Terpenic alcohols
Tartaric acid in wine is…
30 - 60% dissociated as HT-
NOT 80-90% dissociated as T2- because this is when the pH is super high
and NOT when calculated as the sum of all its four possible forms because there are only 3 forms
To acidify a wine by boosting its SOURNESS the following treatments should be considered…
Increasing T by adding MALIC acid that is admitted by EU regulation
AND
Selecting a yeast strain capable of releasing MALIC acid so to replace what was lost in the vineyard
NOT
Adding any kind of acid just to lower pH
Tartrate precipitation in wine are…
inevitable, because of an excess of KHT
NOT due to the presence of Calcium tartromalate and not triggered by CaT
Deacidifying a wine with KHCO3 is…
- Cheaper than with tartrates
- Effective to stimulate the malolactic fermentation
- Capable to origin a lot of bubbles when its added
Buffer capacity is a natural property of the wine form…
Weak acids coupled with strong bases.
NOT
Being a hydroalcoholic solution (as we would have to buffer it with acids, etc.)
NOT
Strong acids coupled with weak bases (as strong acids in wine would make it undrinkable)
By reducing pH we can increase the fraction of _______ SO2
The fraction of free SO2 (also molecular SO2)
NOT Total SO2 or Combined SO2
The Glycolysis (3 important aspects)
- Produces 2 co-factors that further need to be recycled.
- Is common both to respiration and fermentation pathways.
- Represents the first step in the sugar catabolism by yeast.
The “Crabtree Effect” is…
The “bottle neck” of the sugar catabolism in yeast cells depending on specific conditions
AND is Both
the activation of the respiration due to low sugar concentration and oxygen
AND
the suppression of the respiration due to high sugar concentration and no oxygen.
The Crabtree effect is a switch, in oenology we use positive. Positive does one pathway and negative does both.
Acetaldehyde is a determining intermediate in…
The production of ethanol
NOT sulphured compounds or lactic acid
Malo-Alcoholic fermentation…
Is a tool for a natural deacidification by converting malic acid directly into ethanol.
Among the following, which are the changes occurring during malo-lactic fermentation?
- Acetic acid increases due to catabolism of citric acid.
- the pH remains unmodified, but malic acid disappears.
- the pH diminishes for spontaneous precipitation of KHT
- Acetic acid increases due to catabolism of citric acid.
WHY?? because the pH increases
Concerning the factors affecting the timing of MLF… Which is true?
- Yeast Bacteria are not competing for nutrients
- SO2 binding and the products of yeast autolysis stimulate bacterial growth.
- Ethanol, bisulfite, and fatty acid formation by yeast dont inhibit bacterial growth.
SO2 binding and the products of yeast autolysis stimulate bacterial growth
