Wine Components & Winemaking Flashcards

1
Q

What is the predominant alcohol in wine?

A

Ethanol

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2
Q

What are the main types of acid in grapes?

A

Tartaric and Malic

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3
Q

What is the typical total acidity in wine?

A

5.5-8.5g/L

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4
Q

What is pH?

A

A scale of measurement for the concentration of the effective acidity of a solution

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5
Q

What is the typical pH range of a wine?

A

3 to 4

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6
Q

How does the pH scale work?

A

It is an inverse scale so the lower the number, the more concentrated the acidity.
The scale is logarithmic so a pH of 3 is 10 times more acidic than a pH of 4

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7
Q

How does a low pH affect a wine?

A

A low pH increases the microbiological stability of a wine
Increases the effectiveness of SO2
Gives red wines bright red colour
Enhances wine’s ability to age well

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8
Q

What are the 4 sources of aromatic compounds in wine?

A

Aromas from the grapes
Aromas created by fermentation from precursors
Aromas originating from fermentation and it’s by-products
Aromas from other sources

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9
Q

What are 2 examples of aromas that come from the grape?

A

Methoxypyrazines and Rotundone

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10
Q

What are 2 examples of aromas that are created by fermentation from precursors?

A

Thiols and Terpenes

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11
Q

What are 3 examples of aromas originating from fermentation and it’s by-products?

A

Esters
Acetaldehyde
Diacetyl

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12
Q

What are Esters?

A

Compounds which has formed by the reaction of certain acids and alcohols.
Majority are created through the actions of yeasts in the fermentation process.
They are responsible for many fresh and fruity aromas, the most common ester is Oamyl Acetate which gives banana aromas

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13
Q

What is Acetaldehyde?

A

It is an aroma that occurs in wine due to the oxidation of ethanol.
It masks fresh fruit aromas and has a stale smell regarded as a fault in most wines
It is an important component in the smell of Fino Sherry

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14
Q

What is Diacetyl?

A

It is an aroma that is produced during fermentation and especially during Malolactic Conversion
It contributes a buttery aroma

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15
Q

What is Eucalyptol?

A

It is an aroma volatized from Eucalyptus trees by heat and absorbed into the waxy layer of the skins of grapes in nearby vines

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16
Q

What is the allowed residual sugar in a Dry/Sec/Trocken wine?

A

Up to 4g/L or not exceeding 9g/L provided that total acidity is not more than 2g lower than RS content

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17
Q

What is the allowed residual sugar in a Medium Dry/Demi Sec/Halbtrocken wine?

A

More than 4g/L and not more than 12g/L or up to 18g/L provided that total acidity is not more than 10g below the RS content

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18
Q

What is the allowed residual sugar in a Medium/Medium Sweet/Moelleux/Lieblich wine?

A

More than 12g/L and not exceeding 45g/L

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19
Q

What is the allowed residual sugar in a Sweet/Doux/Suss wine?

A

At least 45g/L

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20
Q

Why is oxygen threatening for the production of fresh fruity wines?

A

Oxygen breaks down the aroma compounds that gives these wines their style

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21
Q

What is the name of the practice of minimising oxygen exposure during winemaking?

A

Reductive or protective winemaking

22
Q

What are some ways of limiting the effect of oxygen on the must or wine?

A

Avoiding ullage in vessels
Use of inert gases
Addition of SO2
Use of impermeable containers
Cool, constant temperatures

23
Q

What are some techniques of increasing oxygen exposure?

A

Use of cap management techniques in red wine fermentation that spray or splash the must or wine
Use of small wooden barrels
Increasing the number of rackings or lees stirring
Allowing ullage in containers without use of inert gases in headspace
Use of techniques that involve pumping oxygen through the must/wine

24
Q

What is hyperoxidation?

A

A technique that involves pumping oxygen through the must

25
Q

What is micro-oxygenation?

A

A technique that involves pumping oxygen through wine

26
Q

What are the two main uses for Sulfur Dioxide?

A

Anti-Oxidant
Anti-Microbial

27
Q

How does Sulfur Dioxide work as an antioxidant?

A

It redues the effects of oxidation by reacting with the products of oxidation reactions, so they cannot oxidise further compounds in the wine

28
Q

How does Sulfur Dioxide work as an antimicrobial?

A

It inhibits the development of microbes such as yeast and bacteria

29
Q

What are the various forms of SO2?

A

Gas, liquid or solid
Sulfur dioxide, potassium metabisulfite or potassium bisulfite

30
Q

What is the maximum level of SO2 allowed in white and reds wines in the EU?

A

White wine - 200mg/L
Red wine - 150mg/L

31
Q

What is bound SO2?

A

When SO2 is added to must or wine it dissolves and some of it reacts with compounds in the liquid - this portion is called bound SO2

32
Q

What is free SO2?

A

The proportion of SO2 that is not bound is called free SO2, the vast majority of the free SO2 exists in a relatively inactive form and a small portion exists as molecular SO2

33
Q

How does a lower pH affect the efficacy of SO2 in a wine?

A

At lower pH levels a greater proportion of free SO2 is in the molecular form, making it more effective against oxidation and microbes

34
Q

What are some common forms of enrichment?

A

Adding dry sugar
Adding grape must
Adding grape concentrate
Adding RCGM

35
Q

What are some common processes of concentration?

A

Reverse osmosis
Vacuum extacting
Chilling

36
Q

Why would sugar be added when fermentation is already underway?

A

Because the yeasts are already active so they can cope better with the additional sugar in the must

37
Q

What acid is typically used for acidification?

A

Tartaric acid

38
Q

Why would acidification typically be done before fermentation?

A

So that the fermentation can benefit from a lower pH and it is believed to integrate better at this stage

39
Q

How is deacidification carried out?

A

Calcium carbonate (chalk) or potassium carbonate is added to the wine and it lowers the acidity by the formation and precipitation of tartrates

40
Q

What temperature should a ferment be for a fresh fruity white wine or rose?

A

Cool - 12-16°C

41
Q

What temperature should a ferment be for a easy drinking fruity red wine or a less fruity white wine?

A

Mid - 17-25°C
Middle of the range for less fruity white wines, top of the range for barrel fermented white wines

42
Q

What temperature should a ferment be for a red wine with pronounced flavour concentration?

A

Warm - 26-32°C

43
Q

At what temperature might a fermentation get stuck?

A

Above 35°C

44
Q

Why are concrete vats coming back into fashion as a fermentation vessel?

A

They have a high thermal inertia

45
Q

What is Malolactic Conversion?

A

The result of lactic acid bacteria converting malic acid into lactic acid and CO2, it also produces heat

46
Q

Which conditions encourage Malolactic Conversion?

A

Temperatures of 18-22°C
Moderate pH (3.3-3.5)
Low total SO2

47
Q

What conditions inhibit or prevent Malolactic Conversion?

A

Temperatures below 15°C
Low pH
Moderate levels of SO2

48
Q

What are the 4 main outcomes of Malolactic Conversion?

A

Reduction in acidity and rise in pH
Some colour loss in red wines
Greater microbial stability
Modification of the flavour

49
Q

What might an advantage of carrying out Malolactic Conversion in a barrel vs. a tank?

A

The ability to stir the lees at the same time as it is happening, and promote better integration of the flavours

50
Q
A