Winemaking & Maturation

Question 1

What roles does yeast play during alcoholic fermentation?

Answer 1

• Converts the sugar to alcohol.

Question 2

What are the 3 components of the pulp?

Answer 2

• Water
• Sugar
• Acid (tartaric & malic)

Question 3

What’s the biggest threat to a wine dominated by primary aromas during the wine making process? Which antioxidant is used to prevent this threat?

Answer 3

• Oxygen.
• Sulfur dioxide.
(grapes are picked during the night when temp is lower)

Question 4

What does protective or anaerobic winemaking entail?

Answer 4

• Keeping the grapes from oxygen by filling airtight winery equipment with carbon dioxide or nitrogen whilst the grapes await processing/winemaking.

Question 5

What are inert vessels?

Answer 5

Airtight vessels:
• Stainless steel vessels - easy to clean, can be of any shape and size. Can incorporate temperature control mechanisms in the form of sleeves (outside) or coils (inside) that carry hot or cold liquid.

• Cement lined with epoxy resin - less easy to clean. Used prior to stainless. The thick concrete helps regulate temperature without expensive equipment.

Question 6

What does matured aerobically mean?

Answer 6

• Wines that were stored in oak vessels. Small amounts of oxygen interacts with the wine to soften tannins and add complexity.

Question 7

What has greater oxidative effect, small or large oak vessels?

Answer 7

• Small vessels like a barrique, have greater oxidative effect as they present a proportionately larger surface area of wood to the wine. (wines are rarely kept in barriques for more than 2 years)

Question 8

What are the 2 effects of Sulfur dioxide (SO2) in wine?

Answer 8

• Antioxidant - protects the grape juice wine wine from oxygen.

• Antiseptic - SO2 is toxic to the many strains of yeast and bacteria that can cause unwanted flavors. (the principal yeast used in fermentation can tolerate SO2 unlike the rest of the yeast species)

Question 9

What effect does oak vessel have on a wine and what is a particular challenge?

Answer 9

• Softens the wines natural tannins.
• The oak tannins gives structure and textural complexity.
• Can develop tertiary aromas.
• Hygiene can be a particular challenge in terms of moulds, bacteria and yeast. (wine can be ruined by tainted wood)

Question 10

What are 4 factors to consider when selecting an oak vessel?

Answer 10

• Species and origin of oak (European or American)

• Size (ranges from 225l to 2000l)

• Production (the level of toasting of the actual vessel)

• Age (by the time the vessel is on its fourth usage it imparts little to no tannins and flavor)

Question 11

What are these size of oak barrel called?
1. 225 litre
1.228 litre

Answer 11

1. Barrel / Barrique
2. Piece

Question 12

What’s a cheaper alternate to oak?

Answer 12

• Staves or wood chips in an inert vessel. (oxygen can be added by small controlled quantities.)

Question 13

What is free run juice?

Answer 13

• Comes from the crushing of the grapes as they arrive at the winery. Note, this happens before pressing & fermentation.

Question 14

How does a pneumatic press work?

Answer 14

• An inflatable rubber tube, within a perforated, horizontal, stainless steel cylinder. Applies pressure over a larger area in a controllable way. Oxygen can be kept to a minimum.

Question 15

What’s another word for grape juice?

Answer 15

• Must

Question 16

What is must weight?

Answer 16

• The level of sugar in the must (grape juice).

Question 17

When can a wine maker choose to add RCGM?

Answer 17

• Before or during fermentation. Rectified Concentrated Grape Must is a colorless, odorless and syrupy liquid that gets added when the naturally occurring must weight (sugar) is insufficient.
Note - this will enhance the alcohol as there will be more sugar for the yeast to convert. This is only allowed in certain parts of the world.

Question 18

1. What can be done if the acid level has fallen too far during ripening?
2. Haven’t fallen sufficiently?

Answer 18

1. Acidification - normally in the form of powdery tartaric acid. In Europes it’s only permitted in warm regions. A common treatment in warm and hot regions in the rest of the world.
2. Deacidification - excess acid is naturalized by an alkaline substance. Common in cooler climates.

Question 19

What is alcoholic fermentation and what are the by products?

Answer 19

• The conversion of sugar into alcohol and CO2 through the action of yeast.
• Heat and flavor compounds.

Question 20

Which yeast species is responsible for alcoholic fermentation and why?

Answer 20

• Saccaromyces cerevisiae - because of its tolerance to alcohol and SO2.

Question 21

What temperature is too cold & too hot for alcoholic fermentation?

Answer 21

• Anything below 5C or anything above 35C

Question 22

1. What is used to kill yeast in order to stop fermentation?
2. What is done to remove yeast?

Answer 22

1. SO2 or by adding grape spirit.
2. Filtration after chilling the fermentation down to below 5C.

Question 23

1. What is true for commercially cultured yeast?
2. What is true for ambient yeast (already existing on the grapes)

Answer 23

1. Consistently perform and produce attractive flavors. Suitable for high volume production.
2. Increases the complexability. May vary between batches and the winemaker can’t control exactly which strains is present.

Question 24

1. When does malolactic fermentation take place and what does it convert? Also known as MLC & MLF.
2. How do you encourage & avoid MLC to take place?

Answer 24

1. After alcoholic fermentation. Converts the tart malic acid to softer lactic acid.
2. Encourage by raising the temperature and not adding SO2. Avoided by storage at cool temperature, adding SO2 or by filtering out the bacteria.

Question 25

What are the 6 constituents (parts) of a wine?

Answer 25

• Ethanol
• Tannins & color
• Acids
• Water
• Sugars
• Aroma & flavor compounds

Question 26

Blending is vital to almost all wines. What are the 3 different ways to blend wine?

Answer 26

• From different vineyard locations and vintages. This may be restricted by local wine laws.

• Free run juice with pressed juice to enhance tannins in the final product.

• Different varieties

Question 27

Why do wines in matured in small barrels need to be blended together in a large vat prior to bottling?

Answer 27

• To smooth out any inconsistency that maybe be present. Can be due to the oak, fruit development, vineyard sites, harvest time etc.

Question 28

What is a fraction?

Answer 28

• Different batches of grape juice (must) throughout the pressing. The juice from the first press is very different from the juice of the last press.

Question 29

What is racking?

Answer 29

• The process of removing gross lees after they have settled into a deposit. The wine is slowly and gently pumped into a separate vessel leaving the sediment behind.

Question 30

How can the time it takes for sedimentation be accelerated?

Answer 30

• By a centrifuge but this equipment is very expensive.

Question 31

What does Fining entail?

Answer 31

• A process that speeds up the finer lees to clump together quicker by adding a fining agent. These are then removed through filtering.

Note - some winemakers do not fine their wines as they believe it can affect the the flavor and texture.

Question 32

What are the 2 methods of Filtration?

Answer 32

• Depth filtration - filters are made from a thick material. As the wine passes through the solids particles will be trapped in the material. Good for gross lees.

• Surface filtration - filters resemble very fine sieves. The solid particles gets trapped on the surface of the material. Good for fine lees and generally used after depth filtration.

• Note - when pore size is small enough to remove bacteria and yeast of a surface filtration, it’s called sterile filtration.

Question 33

What are tartrates, how are they formed and removed?

Answer 33

• White or purple crystals formed by tartaric acid.

• Cool temperatures accelerates the formation. Can be deposit during pre-bottling maturation for some wines. Can be forcefully formed by chilling the wine down to 0C for a short period and then removed by filtration.

Note, these crystals are flavorless and harmless but can ruin the appearance for a consumer.

Question 34

What is true about microbiological stability when talking about spoilage?

Answer 34

• Wines that have undergone MLC are more resistant to yeast and bacterial spoilage.

• Wines with low alcohol, low acidity, little sugar and no MLC are particularly at risk and therefore get sterile filtered prior to bottling.

Question 35

What are two things that can be done to wine bottles prior to bottling in order to avoid oxidation?

Answer 35

• Flushing with nitrogen or CO2 before bottling.

Question 36

What is the lifespan of a wine in a bag-in-box?

Answer 36

• 18 months. The plastic will allow for some air to enter can this packaging is not suitable for long term aging.