Grape Development

Question 1

When is grape development in the Northern hemisphere?

Answer 1

June to October (6-10)

Question 2

What is grape development in the southern hemisphere?

Answer 2

December to April (12-4)

Question 3

What are the four stages of grape development?

Answer 3

1. grape berry formation
2. verasion
3. ripening
4. extra-ripening

Question 4

What happens during grape berry formation?

Answer 4

• hard green grapes start to grow in size
• tartaric and malic acids accumulate
• some aroma compounds and aroma precursors accumulate
• tannins (very bitter) accumulate
• sugar levels are low throughout this stage
• water flow into the grape is high at this stage

Question 5

What are methoxypyrazines?

Answer 5

Aroma compounds that contribute to herbaceous aromas/flavors in some wines, such as those from Sauv Blanc, Cab Sauv, and Cab Franc. They develop during grape berry formation.

Question 6

What causes a prolonged grape berry development period?

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, and how does this affect the final wine?

Answer 7

Mild water stress

• yields to smaller grapes
• reduces juice yield
• greater skin to pulp ration (can be associated with bitter quality in red wines)
• higher levels of color, 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-colored chlorophyll in skin cells is broken down
• grapes of black varieties start to become red in color 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 happens to the grape during ripening?

Answer 12

• the cells in the grape expand rapidly
• sugar and water accumulate
• acid levels fall
• tannins, color, and a number of aroma precursors and compounds develop

Question 13

What is the temperature required for photosynthesis to occur at the maximum rate?

Answer 13

18-33 C (64-91 F)

Question 14

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

Answer 14

• extreme water stress
• cause photosynthesis to slow or stop
• hinder sugar accumulation

Question 15

How do grapes develop sugar?

Answer 15

• sugar is produced in the vines’ leaves by photosynthesis
• a sugar solution is transported by the phloem into the grapes

Question 16

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

Answer 16

Faster = warm, dry conditions

Slower = cool, humid conditions

Question 17

How does the concentration of tartaric acid change during ripening?

Answer 17

• total amount of tartaric acid in the grape generally does not change
• however the concentration falls during ripening due to dilution, as sugar and water accumulate in the grape

Question 18

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

Answer 18

• 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 19

During the final month of ripening, what temperature range is crucial?

Answer 19

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

Question 20

What happens to methoxypyrazine levels during ripening?

Answer 20

• 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/flavors

Question 21

What aroma compound increases during ripening? What flavors can they create?

Answer 21

• terpenes
• give floral and citrus aromas, such as the grapey aromas found in Muscat

Question 22

What conditions give off “riper” aromas?

Answer 22

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

Question 23

In black grapes, when are tannin levels the highest?

Answer 23

• highest at verasion
• start to decrease slightly at ripening

Question 24

What tannins polymerize, how does it affect the flavor?

Answer 24

causes them to become less bitter

Question 25

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

Answer 25

- anthocyanins increase during ripening stage - plentiful sunlight, temps between 15 and 25 C

Question 26

What 4 factors determine the length of ripening?

Answer 26

1. variety 2. climatic conditions 3. management of the vine and vineyard 4. time of harvest

Question 27

Name 2 early ripening varieties

Answer 27

- Chardonnay - Pinot Noir

Question 28

Name 2 late ripening varieties

Answer 28

- Cab Sauv - Grenache

Question 29

In what climatic conditions is sugar ripening quickest?

Answer 29

- 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 30

Name 2 elements of vineyard management that can slow down ripening

Answer 30

1. heavy crop loads 2. excessive shading within the vine canopy

Question 31

What happens if ripe grapes are left on the vine?

Answer 31

- grapes start to shrivel - no more sugar or water are imported to the grape by 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 32

What are the factors that determine ripeness?

Answer 32

1. amount of sugar in the grapes 2. level of acidity in the grapes 3. flavor profile 4. tannin ripeness

Question 33

Describe the grape flavor evolution through ripening

Answer 33

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

Question 34

Describe tannins during grape formation and ripening

Answer 34

- during grape formation, skin tannins accumulate but are bitter to taste - during ripening, tannins polymerise and become less bitter

Question 35

What is a winemaker's main concern with tannins?

Answer 35

- avoid bitter, unripe tannins

Question 36

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

Answer 36

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

Question 37

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

Answer 37

Make adjustments during the winemaking process

Question 38

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

Answer 38

- sugar, alcohol, and acid are easier to adjust than bitter, unripe tannins - many growers will focus on attaining the desired level of tannin and aroma ripeness first since they can adjust other things

Question 39

What happens to the vines in late summer and autumn?

Answer 39

Late summer - cane formation: green shoots lignify Autumn - leaves fall - carbohydrate reserves stored in the roots, trunk, branches - vine enters its dormant period

Question 40

What happens to the vines in late summer and autumn?

Answer 40

Late summer - cane formation: green shoots lignify Autumn - leaves fall - carbohydrate reserves are stored in the roots, trunk, and branches - vine enters its dormant period