Unit 2 - Lesson 4 - Grape Flashcards
1
Q
What is the biological genus of grapes?
A
Vitis
2
Q
How many species of Vitis are approximately there?
A
75 species
3
Q
What is the most important species of grapes for wine and brandy production?
A
Vitis vinifera
4
Q
How many different varieties of Vitis vinifera grapes are estimated to be cultivated worldwide?
A
More than 10,000 varieties
5
Q
What are the four reasons grape juice is excellent for spirits production?
A
- Contains sugars that are easily fermented into alcohol by yeast
- Contains important nutrients for yeast growth and health
- Natural acids help prevent microbial spoilage in wine
- Flavour compounds are generally desirable in spirits
6
Q
What happens during the pollination period of grapevines?
A
Grapevines undergo self-pollination or receive pollen from nearby vines
7
Q
What is the phase called that occurs approximately six weeks after pollination?
A
Veraison
8
Q
What changes occur in grapes during the veraison phase?
A
- Berry tissue begins to soften
- Skin begins to darken
- Sugars start to accumulate
9
Q
What is the relationship between sugars and acids as grapes grow?
A
Inverse relationship; acid levels decrease as sugar levels increase
10
Q
What are the three components of a grape?
A
- Skin
- Seeds
- Pulp
11
Q
Which component of the grape is most important to the distiller and why?
A
Pulp.
It contains:
* fermentable sugars
* aromatic compounds
* acids that protect wine from spoilage
* trace amounts of vitamins and minerals important for yeast health
12
Q
What is ‘must’ in the context of grape processing?
A
The grape juice produced when the grape is pressed
13
Q
What is the typical composition of grape must (in % w/w)?
A
- Water - 78%
- Sugars - 20%
- Potassium tartrate - 1.2%
- Free acids - 0.70%
- Other material - 0.05%
14
Q
What does 1˚Brix represent?
A
One gram of sugar in 100 grams of solution
15
Q
What older sugar measurement scale is sometimes used instead of ˚Brix and what does it express?
A
Balling
sugar content of a solution as a percentage of the solution’s mass
16
Q
What two sugars are found in grape must?
A
- Glucose
- Fructose
17
Q
What is titratable acidity (TA)?
A
A measure of the total amount of acid in must and wine
18
Q
Fill in the blank: The biggest constituent of pulp is _______.
A
Water
19
Q
True or False: High levels of acidity in grape must help prevent spoilage.
A
True
20
Q
Why is it important to choose the correct grape variety for spirits distillation?
A
Different varieties have different characteristics that affect the quality of the spirit.
21
Q
What factors influence the choice of grape variety for distillation?
A
- Type of spirit required (e.g. aged, un-aged, neutral spirit)
- Local regulations
- Yield and harvest availability
- Price
22
Q
What do distillers primarily consider when making neutral spirits?
A
Price, yield, and availability of a grape variety.
23
Q
For un-aged grape brandy production, what is the main quality of a grape variety to be considered?
A
aroma
24
Q
What types of grape varieties are used for producing aged brandy?
A
Less aromatic varieties that work well with flavors from a wooden cask.
25
Which grape varieties are permitted for cognac distillers?
* Ugni blanc
* Folle blanche
* Colombard
26
What percentage of grapes used in cognac production is typically Ugni blanc?
Approximately 95%.
27
What is the primary concern for distillers when selecting grape varieties?
Local availability due to the perishability of grapes and transportation costs.
28
What are the main characteristics of Vitis vinifera?
* Vine-like growth, with tendrils that attach to structures to help support the vine.
* Flaky bark on the vine trunk.
* Flower buds that form late in the growing season and bloom after winter in the following spring.
* Producing grapes ranging from 6-30 mm, which grow in bunches.
* Grapes that have sugar contents of between 15-24% by weight.
29
When are vines typically planted?
During the spring, after being grown in vine nurseries for one year
30
How are one-year old vines transported to the vineyard?
In moistened bundles of 20-25 vines, with a root to tip length of 0.5-1 m
31
What do vineyard workers inspect the vines for?
Root health, signs of disease, and any pest infestation
32
What is the spacing between plants when vines are planted?
One to three m between plants
33
What is the spacing between rows when planting vines?
Three to five m between rows
34
What is a potential strategy for planting vines in some regions?
Planting as close together as possible
35
What effect does planting vines close together have?
Increases competition for water and nutrients, stressing the vines
36
What is thought to improve fruit quality in vines?
Stress from increased competition for water and nutients
37
How long are vines monitored after planting?
For the next three to four years
38
What is the purpose of a wire trellis system in vineyards?
To enable the vines to climb upwards, away from the ground.
39
What is a wire trellis system?
A series of poles and wires enabling the vines to climb upwards
40
What do vineyard workers do during the dormant winter months?
Prune unnecessary or unwanted vines and focus on a few strong canes
41
What are canes in the context of vine growth?
Shoots coming off the vine trunk that have reached at least one year of age
42
When does fruit begin to grow on the vine?
Sometimes as early as two years after planting
43
What is the quality of early grapes typically like?
Low in quality and quantity
44
What often happens to early grapes produced by the vine?
They are usually removed from the vine and discarded
45
When should the vine be ready for its first harvest of wine grapes?
At the fourth or fifth year of growth
46
What factors affect the decisions made by vineyard workers during the growing season?
* Grape variety
* Type of wine desired
* Yield of grapes required
* Soil conditions
* Available sunlight and water
* Pests and disease
* Local regulations
* Growing season conditions
47
What is 'terroir' in the context of viticulture?
The combination of environmental factors and farming practices that give a crop unique qualities.
48
Why do vineyard owners want to harvest grapes as soon as possible?
To avoid higher labour costs and the risk of crop damage from pests, fungi, and rain.
## Footnote
Harvest timing is crucial to minimize losses.
49
What do winemakers and distillers prioritize when harvesting grapes?
Optimum time for sugar and acid composition.
## Footnote
The balance of sugar and acid is key for wine quality.
50
How does wet weather affect grape harvesting?
It can lower sugar levels by dilution and increase the risk of fungal growth.
## Footnote
Weather conditions significantly impact grape quality.
51
Why might a distiller be less concerned about higher sugar levels compared to a winemaker?
The distiller may focus more on the timing of production rather than sugar content.
## Footnote
Different end products require different considerations.
52
Do all distilleries grow their own grapes?
No, many purchase grapes from vineyards.
53
What should distillers establish with vineyards regarding grapes?
Variety(s) of grapes, sugar and acid levels expected.
54
What does distillation concentrate?
Alcohols, aromas, and flavours.
55
Which factors affects the suitability of grapes?
* Sugar levels
* pH and total acidity
* Any sulphur treatments and their timing in the vineyard
* Any sulphur treatments in the winery (if the distiller is purchasing wine that has already been made for the distillery)
* Nutrient content of the must
* Pests and fungi
56
What is a common belief about high sugar levels in distillation?
High sugar levels are the most important factor for a distiller.
57
In which styles of brandy production can higher sugar levels cause problems?
Cognac and Armagnac production.
58
What substance do winemakers often add to combat spoilage organisms?
Sulphur dioxide.
59
What is the typical range of sulphur dioxide added to must and wine?
Approximately 10-50 mg/L.
60
Why do many distillers prefer grapes not treated with sulphur dioxide?
Sulphur dioxide can cause off-flavours in spirits.
61
What practice do many distillers employ to protect juice and fermentation from spoilage?
Harvesting the grapes early.
62
What is the benefit of harvesting grapes earlier?
Higher acid levels help to prevent spoilage of the grape must.
63
What issue can high sugar levels cause during fermentation?
Yeast stress resulting in long fermentations that do not ferment to completion.
64
What do many yeast strains produce in fermentations with high sugar levels?
Higher amounts of esters.
65
What device is used to test sugar levels in grapes before harvest?
Refractometer.
66
What is the typical sugar concentration range for grapes used in brandy production?
16-22 ˚Brix.
67
What effect do grape acids have on the must’s pH level?
Protecting it from spoilage organisms
68
What is the ideal pH range of grape must?
3.4-3.7
69
How can pH be assessed in the vineyard?
Using a pH meter or pH test papers
70
Is testing for total acidity easily done in the field?
No
71
What measurements are required for proper grape assessment?
Measuring pH and total acidity (TA)
72
Which grape varieties generally have lower total acidity values?
Red grape varieties
73
What are the typical total acidity levels for red and white grape varieties?
* Red: 6 g/L
* White: 8 g/L
74
Fill in the blank: The lower the pH, the greater the stress on the _______ during fermentation.
yeast
75
What is sulphur commonly used for in vineyards?
To treat several types of fungi
76
How should sulphur be used in brandy production?
Used sparingly in the vineyard or winery, or not used
77
What can result from careless use of sulphur in spirits?
Off-flavours, such as a struck match aroma
78
When should the final sulphur treatment be applied to the vines?
More than four to five weeks before the expected harvest time
79
What practices help prevent spoilage organisms in the winery?
Lower pH in the must, good distillery hygiene, clean fruit handling practices
80
What should the free sulphur dioxide levels in must or wine be?
Less than 10 mg/L
81
What negative effect can sulphur compounds have on grape spirits?
Cause off-flavours
82
What is the most important parameter to consider in grape must?
Yeast assimilable nitrogen (YAN)
83
What does YAN measure in grape must?
Amino acids, ammonium ions, and small peptides
84
Why is it important to understand the YAN of grape must?
To know if nutrients need to be added before fermentation
85
What are some methods for assessing YAN?
Enzymatic assays, titrations, chromatography
86
True or False: Assessing YAN is easy to do in the vineyard.
False
87
What is the ideal YAN level in grape must?
150-200 mg/L
88
What can happen if YAN levels are too high or too low?
Yeast can produce high levels of hydrogen sulphide
89
What is hydrogen sulphide considered in fermentation?
An undesirable flavour compound
90
Fill in the blank: Adding excessive amounts of nutrients can result in _______.
Undesirable flavours in spirit
91
What are some common pests that affect grapes?
Various insects, including the brown marmorated stink bug
92
What damage does the brown marmorated stink bug cause to grapevines?
Damages leaves and can cause fruit to rot before harvest
93
What can insect damage to grapevines lead to?
Wounds that create openings for fungal infections
94
What is botrytis also known as?
Noble rot
95
What effect does botrytis have on grape sugar concentrations?
Can lead to incredibly high sugar concentrations that cause problems during fermentation
96
How does botrytis affect fermentation?
Emits anti-fungal compounds that inhibit yeast's ability to ferment sugar effectively
97
Fill in the blank: Low levels of _______ may not be detrimental to wine making.
botrytis
98
What is the typical acceptance level of botrytis infection for winemakers?
Usually at an infection count of three percent, or less
99
What are pomme fruits?
Pomme fruits include apples, pears, and quince.
100
What is a key difference between the sugar levels in pomme fruits and grapes?
Pomme fruits’ sugar levels are usually much lower than grapes.
101
What is the approximate sugar concentration of most pomme fruit varieties?
Approximately 14 ˚Brix.
102
Why are acid levels in pomme fruits, particularly pears, significant?
Lower acid levels can encourage spoilage organisms during fermentation.
103
What is pomace brandy made from?
Pressed grape skins left over from winemaking.
104
What must a distiller consider regarding the timing and handling of pomace?
Pomace should ideally reach the distillery within 48 hours of pressing because it can oxidise and become contaminated with spoilage organisms.
105
How can the time for processing pomace be extended?
By using refrigeration.
106
Why does the level of pressing matter when selecting pomace for distillation?
Some wineries use very high pressures to extract more juice or more tannin content from the grapes which can remove almost all the sugar left in the pomace.
