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Wine Chemistry (winter semester) > Final Exam > Flashcards

Final Exam Flashcards

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1
Q

Name examples of inorganic sources of Nitrogen in grape must.

A
  1. Ammonia
  2. Nitrates
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2
Q

Quality Assurance vs Quality Control

A

Quality Assurance (QA) is an overall system/program for maintaining Quality Control (QC)
procedures. (i.e. QA = calibration procedures while QC = the calibration)

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3
Q

Name Organic Sources of Nitrogen in grape must.

A

-Amino Acids
-Polypeptides
-Proteins
-Vitamins

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4
Q

The ionization state of amino acids in dependent on ________?

A

Ionization state of amino acids is pH dependent

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5
Q

What is the ionization state of amino acids in ACIDIC solutions?

A

Amino group = ionized
Carboxyl group = not

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6
Q

What is the ionization state of amino acids in NEUTRAL solutions?

A

BOTH (amino and carboxyl group) are ionized

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7
Q

What is the ionization state of amino acids in BASIC solutions?

A

Amino groups = neutral
Carboxyl group = ionized

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8
Q

What is the most abundant amino acids in grape must?

A
  • Proline
    – not metabolized by yeast under anaerobic conditions (& Not considered an assimilable source of Nitrogen)
  • Arginine
  • Glutamine & Alanine
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9
Q

How are peptide bonds formed?

A

Peptide bonds are formed
when the amino group from
one amino acid is linked to
the carboxyl group of
another amino acids forming
the amide functional group

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10
Q

What are proteins made up of?

A

Proteins are made up of long
chains of amino acids linked
through peptide (amide)
bonds

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11
Q

What factors contribute to Total Nitrogen content?

A
  • Grape Maturity
  • Climate
  • Variety
  • Rootstock
  • Fertilization
  • Harvest method
  • Botrytis infection
  • Winemaking practices
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12
Q

What does YANC stand for?

A

Yeast Assimilable Nitrogen Content

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13
Q

What makes up YANC?

A

Ammonia content & FAN (Free Amino Nitrogen Content

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14
Q

What happens when yeast use Nitrogen in amino acids to build new amino acids?

A

Higher alcohol (Fusel alcohols) are formed (through deamination or transamination)

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15
Q

How are Fermenation Esters formed?

A

when higher alc reacts w carboxylic acids in white wine

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16
Q

What is Arginine Degradation? *

A

Arginine degradation releases urea,
which can react with ethanol to produce ethyl carbamate
* Ethyl carbamate is carcinogenic
* LCBO has limits for ethyl carbamate
content

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17
Q

Vitamin Deficiencies are not common, but name 3. *

A
  • Thiamin
  • Required for decarboxylation of pyruvate to
    acetaldehyde, lead to pyruvate accumulation
  • Pyridoxin
  • Used as a cofactor in Met synthesis, can cause build up
    of H2S
  • Pantothenic Acid
  • Required for synthesis of CoA (in acetyl CoA)
  • Acetyl CoA required in intermediate step of Met and Cys
    synthesis, can lead to H2S production
  • Also lead to acetic acid accumulation
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18
Q

What is the formula for Alcoholic Fermentation?

A

C6H12O6 + yeast –> 2C2H5OH + 2CO2

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19
Q

How can you determin Alcohol in a wine?

A

-Cash Still (distillation)
-Ebulliometry

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20
Q

How is sucrose transported?

A

Sucrose is transported through phloem

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20
Q

What sugar type is more prominent in grapes?

A

Glucose + Fructose

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21
Q

In warmer climates, is there more or less glucose?

A

warmer climate = riper fruit = less glucose

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22
Q

In cooler climates is there more or less glucose?

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A

cool climates = less ripe fruit = more glucose

23
Q

What is the 1st step in sugar metabolism?

Study These Flashcards
A

Glycolysis (Anaerobic metabolism)

24
Formula for alcoholic fermentation?
C6H12O6 + yeast --> 2C2H5OH + 2CO2
25
What sugar type do yeast prefer to consume?
Most wine yeast prefer to consume glucose over fructose * Most saccharomyces are glucophilic
26
What types of sugars are reducing sugars?
Aldehydes and alpha-hydroxy ketones: * Glucose, fructose, mannose, etc. * Pentose (5-carbon) sugars * Ribose, arabinose, rhamnose, xylose
27
Is sucrose a reducing sugar?
NO! It must perform sugar inversion prior to testing
28
Why might you add sugar to must or wine?
* Increase final alcohol of fermentation * Add RS post-fermentation (generally adding SUCROSE)
29
Rebelein Method Considerations
Sugar concentration must be <28g/L * Above 28g/L dilute to the appropriate range and multiply the final result by dilution factor -and use DI water as a blank - and decolourize red wine prior
30
Grape juice/must contain which ratio?
Generally, grape juice/must contain a 1:1 concentration of glucose:fructose
31
How to test RS?
Rebelein Enzymatic testing FOSS Fermen-Test
32
What is a buffer?
A buffer is a solution that can resist pH change upon the addition of an acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.
33
What is NTU?
* Nephelometric Turbidity Units * Turbidity is the amount of cloudiness in a liquid
34
What is cold stability?
Tartrate stability
35
What are tartrates?
* Tartaric acid (H2T) * Bitartrate ion (HT-) * Tartrate ion (T2-)
36
What are wine crystals?
Potassium bitartrate precipitates to form ‘wine crystals’
37
How can we cold stabilize wines?
* Chill wines to 0-4 ° C for an extended period (Rack off tartrate crystals while wine is still cold) * Chill wines to 0 °C and seed with crystal (Small crystals of KHT will introduce nucleation points to promote further crystallization) * Add crystallization inhibitors
38
Cold Stability testing
Qualitative methods * Freezer test: Freeze wine completely * Do crystals redissolve into solution? * Fridge test: Store wine at 4 °C for predetermined period (ie.7 days) * Quantitative method * Conductivity testing
39
Tartrate stability is especially important for sparkling wine, why?
Any tartrate crystals will act as nucleation points for bubbles * Larger bubbles, or gushing at disgorging
40
Total SO2 (TSO2) = ?
Free SO2 (FSO2) + Bound SO2
41
If your must is dirty, how will that affect how much SO2 you add?
Dirty juice/must will consume SO2 (will need to add extra)
42
What is the most important form of SO2?
Molecular
43
How do you measure SO2?
Ripper Method (indirectly) Aspiration (directly)
44
Factors that affect MLF
* Temperature * pH * Alcohol * SO2 * Nutrients available * Toxins/inhibitors
45
Name 3 Bacteria that can produce lactic acid?
-Leuconostoc -Pediococcus -Lactobacillus
46
What gases can be dissolved in wine?
N2, O2 and CO2
47
What effect does Oxygen have on juice/must and wine?
-Oxygen is important for yeast pre-ferment & during ferment -Oxygen causes oxidation
48
How can you remove dissolved Oxygen from wine?
Use inert gases (N2 or CO2 or Argon) to sparge wine and push out oxygen
49
How does temperature affect the concentration of dissolved gases?
Lower temperatures increase the solubility of O2 and CO2 in liquid
50
How can you measure DO (dissolved wine)?
-DO electrode -Optical sensors
51
When is it most important to check wine DO?
Prior to bottling
52
Is it possible to have too much Carbon Dioxide in wine?
yes. each style varies
53
When would the CO2 level be highest in wine?
* Immediately after fermentation * Will decrease as wine ages and with wine movements
54
What are the two types of tannins?
-Hydrolysable tannins (gallic acid) -Condensed tannins (flavanoids)
55
There are 5 types of taste receptors on your tongue
* Sweet * Sour * Salty * Bitter * Umami (savoriness)
56
Name an inert gas dissolved in wine (heavy) that helps protect against oxidation
CO2

Wine Chemistry (winter semester) (6 decks)

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