2.5 Grape Development

Question 1

When is Grape Development in the Northern Hemisphere?

Answer 1

June–October

Question 2

When is Grape Development in the Southern Hemisphere?

Answer 2

December–April

Question 3

What are the four stages of grape development?

Answer 3

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

Question 4

What happens during grape berry formation? What starts to develop?

Answer 4

Hard green grapes start to grow in size

• Tartaric and malic acids accumulate
• Some aroma compounds and aroma precursors
• Tannins accumulate (very bitter)
• Sugar levels are low throughout this stage.
• Water flow into the grape is high at this stage

Question 5

What are methoxypyrazines? When do they start to develop?

Answer 5

Methoxypyrazines is an aroma compound that contributes to herbaceous aromas/flavours in some wines, such as those made from Sauvignon Blanc, Cabernet Sauvignon and Cabernet Franc.
- Develops during grape berry formation

Question 6

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

Answer 6

• 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 the weather becomes cold and rainy and the grapes need to be harvested

Question 7

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

Answer 7

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)

Question 8

What occurs during Veraison?

Answer 8

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

Question 9

What does the vine need during grape development?

Answer 9

• Sunlight
• Warmth
• Mild water stress

Question 10

What are adverse conditions during grape development?

Answer 10

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

Question 11

When does shoot growth start to slow down?

Answer 11

Ripening

Question 12

What stage marks the end of ripening?

Answer 12

Harvest

Question 13

When is Harvest in the Northern Hemisphere?

Answer 13

August–October

Question 14

When is Harvest in the Southern Hemisphere?

Answer 14

February–April

Question 15

What happens to the grape during ripening? What accumulates? What falls? What develops?

Answer 15

• The cells in the grape expand rapidly
• Sugar and water accumulate
• Acid levels fall
• Tannins, colour and a number of aroma precursors and aroma compounds develop

Question 16

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

Answer 16

• 18–33°C (64–91°F)

- 1/3 total sunshine

Question 17

What amount of sunlight is required for Photosynthesis?

Answer 17

• Sunlight levels that are above one third of full sunshine

Question 18

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

Answer 18

• Extreme water stress
• Cause photosynthesis to slow or stop
• Hinder sugar accumulation

Question 19

How do the grapes develop sugar?

Answer 19

• Sugar is produced in the vines’ leaves by photosynthesis

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

Question 20

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

Answer 20

Faster = warm, dry conditions
Slower = cool, humid conditions

Question 21

How does the concentration of tartaric acid change during ripening?

Answer 21

• 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

Question 22

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

Answer 22

• Malic acid can be used 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

Question 23

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

Answer 23

• 15 - 21 degrees C (59 - 70 degrees F)
• Warmer than 21: rapid loss of acidity
• Cooler than 15: acidity levels are too high

Question 24

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

Answer 24

• 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

Question 25

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

Answer 25

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

Question 26

What conditions give off 'riper' aromas?

Answer 26

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

Question 27

In black grapes, when are tannin levels the highest? When do they start to decrease?

Answer 27

- Highest at Verasion | - Start to decrease slightly at ripening

Question 28

When tannins polymerise, how does it affect the flavor?

Answer 28

Causes them to become less bitter.

Question 29

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

Answer 29

- Anthocyanins increase during the ripening stage - Plentiful sunlight - Temperatures between ~ 15°C and 25°C

Question 30

What 4 factors determine length of ripening?

Answer 30

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

Question 31

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

Answer 31

- Chardonnay and Pinot Noir are examples of early ripening grape varieties. - Cabernet Sauvignon and Grenache are late ripening varieties.

Question 32

In what climactic conditions is sugar ripening quickest? What if it's too much?

Answer 32

- Sugar ripening is quickest in warm, dry conditions. | - However, very hot or dry conditions can cause the vine to shut down, which inhibits grape formation and ripening.

Question 33

Name 3 elements of vineyard management that can slow down ripening.

Answer 33

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

Question 34

What happens if ripe grapes are left on the vine?

Answer 34

- 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

Question 35

What are the factors that determine ripeness?

Answer 35

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

Question 36

Describe (generally) the grape flavor evolution through ripening.

Answer 36

- under-ripe (often herbaceous) - to fresh fruit - to riper fruit, - to even jammy or cooked fruit

Question 37

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

Answer 37

- 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

Question 38

What is a winemaker's main concern with tannins?

Answer 38

- Avoid bitter unripe tannins

Question 39

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

Answer 39

The desired sugar ripeness may be reached before the desired ripeness of aromas and tannins.

Question 40

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

Answer 40

Make adjustments to the wine

Question 41

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

Answer 41

- 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

Question 42

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

Answer 42

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