17.1 Concentrating the Grape Must

Question 1

What are the key winemaking factors related to producing wines from concentrated grape must

Answer 1

• concentration of sugar must be sufficient so that fermentation cb stopped before dryness (fermentation stopped prematurely by chilling and/or adding SO2 and then filtering to remove yeast, giving the winemaker greater control over the balance of alcohol and sweetness)
• yeast struggle in a sugary env, esp if alcohol is present (they naturally stop fermenting) ~ wines typically low alc
• concentration of sugar by reduction of water means the remaining components (acid, aroma compounds) are also concentrated - helps to keep these wines in balance
• the process of evaporation of water can add unique flavours (esp botrytis)
• volume of juice is low due to lost water, sugary pulp is hard to extract during pressing - factors that add to cost
• these wines always sell at premium prices.

Question 2

How is concentrated grape must produced, and what styles of wines are made with it?

Answer 2

3 ways: drying the grapes

• on or off the vine
• botrytis affected grapes
• freezing grapes.

These grapes make sweet and luscious styles of wine Typically of vg or os quality (too much effort and too little volume for any other quality level)

Question 3

Describe the method used to produce grapes with concentrated sugars by drying ON the vine.

Answer 3

• After normal harvest time, grapes will be left on the vine to enter into Stage 4 “Extra ripening” phase.
• Ripened, healthy grapes left on the vine start to shrivel as the grape no longer accumulates sugar and water.
• water is lost via transpiration and sugars, acid, aromas concentrate
• flavours develop taking on more ripe character / dried fruit
• a dry autumn is needed to avoid botrytis / grey rot
• Wines made with these grapes are labelled “late harvest”, “vendanges tardives” (Alsace) and “spätlese” (Germany).
• In Jurancon FR and in Aus, the vine branch will be cut, but left on the trellis accelerating the shrivelling of the grapes and evaporation of water. Flavours will not be as ripe, risk of botrytis is reduced but not eliminated.

Question 4

Describe the method used to produce grapes with concentrated sugars by drying OFF the vine.

Answer 4

• Ripened, healthy grapes are picked and dried off the vine (process can take months)
• In Italy and Spain the drying may take place outside in the sun
• Alternatively temperature and humidity controlled rooms will be used to dry these grapes (single layers on trays)
• The method is often called “Passito” (originates in Italy
• The wines made are Recioto de la Valpolicella and Vin Santo ES

Question 5

What can add to the costs of producing sweet wines made from grape must concentration?

Answer 5

• Because water is depleted, the volume of juice obtained from them is low - The very sugary pulp is also often hard to extract during pressing

Question 6

What is noble rot?

Answer 6

• involves the action of the fungus Botrytis cinerea - same fungus that causes grey rot - under certain conditions it can be used beneficially in sweet wine production

Question 7

Describe the required climatic conditions for harvesting botrytised grapes

Answer 7

Ripened and healthy grapes on the vine.

Region or area is normally close to a large body of water.

Humid, misty mornings are followed by dry and sunny afternoons.

The damp conditions in the morning allow rot to develop on the grape. The fungus punctures the skin making minute holes.

The warm sunny afternoon slows the fungus development and causes water evaporation through the tiny holes made. This concentrates sugar, acid and aromas.

These wines have characteristic aromas of honey, marmalade, citrus zest, ginger and dried fruit.

Question 8

Name 4 types of wines made with noble rot affected grapes.

Answer 8

1. Sauternes 2. Beerenauslese 3. Trockenbeerenauslese 4. Tokaji

Question 9

What term is typically seen on sweet wine labels made with noble rot affected grapes?

Answer 9

‘botrytised’

Question 10

Explain why the costs associated with making noble rot wines are high?

Answer 10

• spread of noble rot is never uniform and several pickings by hand may be needed to select the best grapes (skilled labour, long period of time)
• selective picking and the fact that water has evaporated from the grapes means that the volume of juice obtained is low
• ideal conditions for noble rot do not occur every year, making these wines relatively scarce and therefore expensive
• from time to time the vintage can be lost to rot.
• botrytised grapes are not easy to process. Enzymes called “laccase” are introduced by the fungus and these can oxidise many components of the grape. They are also increase resistance to so2. As a result in winemaking there could be increased use of so2, chilling, and inert gas to protect against negative reactions from oxidation.
• these wines are commonly aged in oak - especially if the variety is neutral (semillon) - oak provides broader texture and adds notes of vanilla. (aromatic varieties - SS)

Question 11

What happens if conditions are too damp?

Answer 11

The fungus will develop too rapidly and cause grey rot, splitting the grapes and encouraging infections

Question 12

Describe the vineyard management of grapes produced for sweet wine production that involves freezing grapes on the vine.

Answer 12

• Healthy grapes to be left to hang on the vine into the late autumn or winter months
• when freezing temperatures arrive, water in pulp turns to ice
• best quality (lowest qty) are picked in January
• in Canada temperatures MUST be −8°C (18°F) or below.
• when picked and pressed, ice remains in the press and the sugar content of the resulting juice is concentrated

Varieties - Riesling, Vidal - Cabernet Franc

Vines must be winter hardy, varieties must have resilient skins that can withstand the strain of “freeze-thaw” cycles (these cycles thought to contribute to specific “icewine character”

Risk of disease / being eaten by birds during the winter means that vineyards are often netted. (adds sign cost)

Question 13

Describe the winery management of grapes produced for sweet wine production that involves freezing grapes on the vine.

Answer 13

• when picked and pressed, ice remains in the press and the sugar content of the resulting juice is concentrated

Most are fermented in SS to retain varietal aroma purity.

Some fermented in oak for vanilla.

Question 14

What is cryoextraction?

Answer 14

• when grapes are picked in autumn (same time as dry wines) and then frozen at a winery to create an “icewine” style of wine - overall is cheaper than traditional Eiswein and Icewine production (but the cost of energy should be noted) These wines cannot use the term “icewein” or eiswein” on their labels

Question 15

What is the main benefit of cryoextraction?

Answer 15

• avoids risk of leaving the grapes on the vine into late autumn or winter and perhaps losing yield to disease or pests - it can be done in regions that do not naturally have the appropriate climate conditions to produce icewine