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L4.1 Production > 2.5 Grape Development > Flashcards

2.5 Grape Development Flashcards

1
Q

When is Grape Development in the Northern Hemisphere?

A

June–October

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2
Q

When is Grape Development in the Southern Hemisphere?

A

December–April

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3
Q

What are the four stages of grape development?

A
  1. Grape Berry Formation
  2. Veraison
  3. Ripening
  4. Extra-Ripening
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4
Q

Describe berry development during the Early Grape Growth phase

A

Small green berries start to grow in size

  • tartaric and malic acids accumulate.
  • Some aroma compounds and aroma precursors (methoxypyrazines) dev
  • Tannins accumulate (very bitter)
  • Sugar levels are low in this phase
  • Water flow into grape is high in this phase
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5
Q

What are methoxypyrazines?

What wines would you find them in?

A

Methoxypyrazines are aroma precursors
- develop into herbaceous aromas/flavours
- in wines, such
Sauvignon Blanc, Cabernet Sauvignon and Cabernet Franc.

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6
Q

What causes a prolonged grape berry development period? Why? Why can this be harmful?

A
  • Too much water and nitrogen encourage shoot growth in preference to grape ripening
  • Causes delay in the onset of the ripening stage
  • May not be sufficient time for ripening before weather changes ~ harvest time
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7
Q

What speeds up the grape berry development period? Why? Describe the result in the final wine.

A

Mild water stress

  • Leads to smaller grapes
  • Reduces juice yield
  • Greater skin to pulp ratio (can be associated with better quality in red wines - higher levels of colour, tannins and aroma compounds)
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8
Q

Describe Veraison?

A
  • Grape growth slows down (lag phase)
  • Grape cell walls become stretchy and supple
  • Green-coloured chlorophyll in skin cells is broken down - black grapes start to become red in colour due to the synthesis of compounds called anthocyanins
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9
Q

What does the vine need during grape development?

A
  • Sunlight
  • Warmth
  • Mild water stress
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10
Q

What are adverse conditions during grape development?

A
  • Too much water and nutrients
  • Excessive shading of grapes
  • Very cold or very hot conditions throughout the day and night
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11
Q

When does shoot growth start to slow down?

A

At the start of the ripening phase.

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12
Q

What stage marks the end of ripening?

A

Harvest

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13
Q

When is Harvest in the Northern Hemisphere?

A

Sept–October

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14
Q

When is Harvest in the Southern Hemisphere?

A

March–April

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15
Q

What changes take place within the grape during the ripening phase?

A
  • Sugar and water accumulate
  • Acid levels fall
  • Tannins, colour and a number of aroma precursors and aroma compounds develop
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16
Q

What is the temperature required for Photosynthesis to occur at the maximum rate? What amount of sunlight is required?

A
  • 18–33°C (64–91°F)

- 1/3 of full sunshine

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17
Q

What amount of sunlight is required for Photosynthesis?

A
  • Sunlight levels that are above one third of full sunshine
18
Q

What effect do warmer years with extreme heat and dry conditions have on photosynthesis and thus, on the vine?

A
  • in extreme heat, or water stress the stomata close. - This pauses photosynthesis and therefore the production of sugar - sugar will not be accumulated as expected.
  • In severe cases the vine shuts down and may die.
19
Q

How do the grapes develop sugar?

A
  • Sugar is produced in the vines’ leaves by photosynthesis

- A sugar solution is transported by the phloem into the grapes

20
Q

In what conditions is the rate of grape transpiration faster? In what conditions is it slower?

A 
Faster = warm, dry conditions
Slower = cool, humid conditions
21
Q

How does the concentration of tartaric acid change during ripening?

A
  • Total amount of tartaric acid in the grape generally does not change
  • However concentration falls during ripening due to dilution, as sugar and water accumulate in the grape
22
Q

Why do wines from cooler climates tend to have higher natural acidity?

A
  • Malic acid is metabolised in respiration during the ripening stage
  • Respiration is slower at cool temperatures than warm ones
  • Cool night time temperatures also mean that less malic acid is lost during respiration
23
Q

During the final month of ripening, what temperature range is crucial? What happens if it’s too warm? Too cool?

A

Mean Temperature between 15° and 21° C (59 - 70 F)

  • Warmer than 21°C : rapid loss of acidity (rapid transpiration)
  • Cooler than 15°C: acidity levels are too high (slower transpiration)
24
Q

What happens to methoxypyrazine levels during ripening? What conditions can hinder this?

A
  • Levels fall
  • Cool temperatures and limited sunlight (e.g. due to excessive shading of bunches) can hinder this decrease and the resulting wines may show particularly herbaceous aromas/flavours
25
Q

What aroma compound increases during ripening? What types of aromas does this compound give off?

A
  • Terpenes

- Give floral and citrus aromas such as the grapey aromas found in Muscat

26
Q

What conditions give off ‘riper’ aromas?

A

Warmer, sunnier climates tend to produce grapes and wines with aromas that could be described as ‘riper’ than cooler, less sunny climates.

27
Q

What role does Tannin play in defining Ripeness and “ready for harvest”

A
  • Producers wish to avoid unripe tannins - tannin ripeness is an important parameter for deciding if grapes are ready for harvest.
  • Sunshine on grapes is essential for
  • -accumulation of tannins pre-veraison
  • -polymerisation of tannins post veraison (means they become less bitter)

Polymerisation is the process in which small molecules chemically combine to form large network molecules

28
Q

When tannins polymerise, how does it affect the flavor?

A

Causes them to become less bitter.

29
Q

What happens to anthocyanin during ripening? What factors encourage this?

A
  • Anthocyanins increase during the ripening stage
  • Plentiful sunlight
  • Temperatures between ~ 15°C and 25°C
30
Q

What 4 factors determine length of ripening?

A
  1. Grape Variety
  2. Climactic Conditions
  3. Management of the Vine & Vineyard
  4. Time of Harvest
31
Q

Name 2 early ripening grape varieties. Name 2 late ripening grape varieties.

A
  • Chardonnay and Pinot Noir are examples of early ripening grape varieties.
  • Cabernet Sauvignon and Grenache are late ripening varieties.
32
Q

Explain the development of sugar as the grapes are ripening

A

Sugar accumulation in the grape is related to photosynthesis & transpiration

Photosynthesis takes place between 18 - 33 deg C and needs >1/3 full sun.

HIgh sugar accum:
Warm/dry = rapid transpiration = rapid accum of sugar while acid falls, and before flavours/tannins ripen

Risk if extremely hot/water stress photosynthesis slows down.

Low Sugar accum:
Cool/cloudy = slow transpiration = slow accum of sugar and acids remain higher.

33
Q

Name 3 vineyard management techniques that can slow down ripening.

A
  1. Heavy crop loads
  2. Excessive shading within the vine canopy
  3. Shoots that are still actively growing
34
Q

What happens if ripe grapes are left on the vine?

A
  • Grapes start to shrivel
  • No more sugar or water are imported to the grape by the phloem at this stage, but water loss in the grape through grape transpiration means that sugars are concentrated.
  • Extra-ripe aromas can also develop in this stage
35
Q

What are the factors that determine ripeness?

A
  1. Amount of sugar in the grapes
  2. Flavor Profile
  3. Tannin Ripeness
36
Q

Explain the development of aroma and flavour compounds and pre-cursors during ripening (don’t forget to mention climate)

A
  • with sufficient sunshine methoxypyrazine levels fall
  • flavour/aroma compounds like terpenes increase
  • the synthesis, retention and degradation of aroma/flavour compounds is influenced by heat and light:
    cooler climates - green / citrus
    warmer climates - stone / tropical fruit
    warmest climates - jamminess

In general “warmer = riper”

37
Q

Describe tannins during grape formation? During ripening? During winemaking and maturing?

A
  • During grape formation, skin tannins accumulate but are bitter to taste.
  • During ripening, tannins polymerise and become less bitter.
  • During winemaking and maturation, the tannin compounds that are extracted from the grapes react with other compounds and as part of this their expression may change:
    • wines with res sugar tannins are masked (seem softer)
    • wines which are dry - tannins may seem more astringent
38
Q

What is a winemaker’s main concern with tannins?

A
  • Avoid bitter unripe tannins
39
Q

Why do wines from warm climates tend to have higher levels of alcohol?

A

The desired sugar ripeness is reached and the grape has high levels of sugar

40
Q

What can winemakers do if the optimal balance of sugar, acid and tannins isn’t achieved naturally?

A

Make adjustments to the wine

41
Q

What’s easiest to adjust: sugar, alcohol, acid, or tannin levels? What does this mean when grape growers try to find optimal ripeness?

A
  • Sugar, alcohol, acid is easier to adjust than bitter, unripe tannins
  • Many grape growers will focus on attaining the desired level of tannin and aroma ripeness first since they can adjust the other things
42
Q

What happens to the vines in late summer? In autumn?

A

Late Summer
- Cane Formation: green shoots lignify (become woody and rigid)

Autumn

  • Leaves fall
  • Carbohydrate reserves stored in the roots, trunk, branches
  • Vine enters its dormant period

L4.1 Production (78 decks)

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