7 - Common Elements in Winemaking and Maturation

Question 1

which parts of the grape contain tannins?

Answer 1

seeds and stems

Question 2

true/false: oak can contribute tannin to red and white wines?

Answer 2

true

Question 3

what are the most abundant acids in the pulp of grape?

Answer 3

tartaric, followed by malic acid. both acids are present in finished wine

Question 4

What is the waxy surface that covers skins of the grapes, and contains yeast that can be used to ferment wine?

Answer 4

bloom

Question 5

what is protective or anaerobic winemaking? What steps are involved?

Answer 5

winemaking that minimizes oxygen contact.
steps: grapes are picked at night when it is cooler (effect of oxygen reduced because chemical reactions slower at low temps)
grapes and juice kept away from oxygen by filling winery equipment with CO2 or nitrogen

storage: usually wines made in this way do not benefit from oxygen contact during maturation. they are stored in stainless steel or cement lined with epoxy resin.

Question 6

What is role of oxidation in oak maturation in terms of structure, complexity, aromas and color of wine?

Answer 6

structure: softens tannins
complexity: offers complexity to whites
aromas: develop tertiary characters like leather and earth
color: red wines become paler and more brown. red wines become deeper and more orange

Question 7

true/false: wines are usually kept in barriques for 2+years

Answer 7

false. barriques are small oak vessels and have larger oxidative effect than larger vessels. therefore they are rarely kept in barrique for over two years

Question 8

What happens to wine in extreme cases of oxidation?

Answer 8

bacteria uses oxygen to change wine into vinegar

Question 9

What is role of SO2 (sulfur dioxide) in the winery?

Answer 9

Antioxidant and antiseptic
antioxidant effects: protects grape juice and wine from oxidation. It can be become ‘bound’ (losing ability to have further protective effect) which necessitates levels being monitored and toopped up
antiseptic effects: SO2 is toxic to yeast and bacteria that cause unwanted flavors. Luckily the principal yeast that ferments alcohol can tolerate SO2

Question 10

What are the effects of the 4 factors to consider in selecting oak vessels (species and origin, size, production, age)

Answer 10

species and origin: different species have different characteristics. Also depending on where grown, same species might have different characteristics (i.e. American vs. European oak).

size: small vessels (called barrels) like 225-litre barrique or 228-litre piece have more effect on wine than larger vessels.

production of oak barrels: toasting involves heaving staves to be bent into shape. the heating process (temperature and length of heating) transforms tannins and flavor compounds in oak - gives sweet spice and toast.

age: effect of toasting diminishes each time barrel is used. by the time cask if on 4th usage, imparts little flavor or tannin.

Question 11

what are more cost effective options to replicate effects of oak maturation or barrel ageing?

Answer 11

oak chips or staves can be inserted during fermentation or maturation to give oak aromas/tannins.

to replicate oxidative effects, oxygen added to vessel.

Question 12

What are the two main types of inert winery vessels and what are pros and cons of each?

Answer 12

stainless steel: most modern vessels made from this. pros: can incorproate temp control mechanisms (like sleeves on outside of vessel, or internal coils)

concrete vessels: these are inert bc lined with epoxy resin which provides waterproof barrier and is inert. not as commonly used after stainless steel introduced. cons: not as easy to clean and maintain as stainless steel. pros: thick concrete shell helps regulate temperature.

(glass is also inert vessel used for storage and maturation)

Question 13

True/false: destemming and crushing are not optional and must take place for all grapes regardless of style of wine it’s intended for

Answer 13

false. these are optional.

if machine-harvested, grapes arrive at winery without stems.

Question 14

how does timing of pressing typically differ for whites vs. reds?

Answer 14

for whites, wine is pressed before fermentation

for reds, pressed after fermetnation

Question 15

what is the more recent form of pressing that conssists of an inflatable rubber tube within a horizontal steel cylinder that applies pressure in a controllable way?

Answer 15

pneumatic pressing

Question 16

Why are adjustments to sugar and alcohol carried out? What are the main ways this is done

Answer 16

Why: in cooler climates, insufficient natural sugar which results lower alcohol.
how: to address this, winemakers might increase sugar levels by adding RCGM before or during fermentation. chaptalisation is when sugar from sources other than grapes is added

another option - remove water from juice which concentrates sugars along with tannins, acids, flavor compounds as well as faults. also reduces the volume

if there is too much sugar: it is difficult to remove sugar, but after fermentation, unwanted alcohol can be removed.

Question 17

what is a colorless, odorless syrupy liquid added to grape juice to increase sugar levels?

Answer 17

RCGM (rectified concentrated grape must)

Question 18

Why and how would winemakers carry out acidification or deacidification?

Answer 18

acidification: adding tartaric acid in powder form. common in warm or hot regions where acid levels have fallen too far during ripening
deacidification: common in cooler climates when acid levels haven’t fallen enough during ripening. adding alkali (chemical opposite of acid) can neutralize excess acid

Question 19

What is the yeast species responsible for majority of wine fermentations?

Answer 19

Saccharomyces cerevisiae

Question 20

What are reasons alcoholic fermentation may stop before all sugar is consumed? What are reasons yeast may struggle to begin fermentation in first place?

Answer 20

if yeast consumes all of the sugar

if yeast runs out of nutrients they need (other than sugar)

if temperature reaches over 35 degrees C

struggle to begin fermentation:
alcoholic fermentation will not start if temp is below 5 degrees C

may sruggle to start fermentation if sugar level is too high

Question 21

What are ways winemaker would stop fermentation before all of sugar is converted to alcohol?

Answer 21

Killing or removing yeast

Killing yeast: add SO2 or grape spirit

Removing yeast: chiling wine below 5 degrees Celsius and removing via filtration

Question 22

What are pros and cons of using ambient yeast strain found on the grape bloom vs adding culutred yeast strain to the must?

Answer 22

ambient yeast strains can produce complex flavors but can be unpedictable and cause variation between batches

cultured yeasts consistently perform and produce attractive flavors but may limit potential complexity

Question 23

What does fermenting at cool or higher temps accomplish in the style of wine?

Answer 23

cool: preserves floral and fruity aromas. floral aromas are most volatile

higher temps: extract color and tannin from black grape skin

Question 24

What is the process that can occur after fermentation is finished, by which lactic acid bacteria convert tart malic grape acid into softer lactic acids? What are the effects of this process on the wine?

Answer 24

Malolactic Fermentation

softens and reduces acidity. creates buttery flavors and produces CO2

Question 25

How can MLF be encouraged or avoided?

Answer 25

encouraged: raising temperature of wine and not adding SO2 after fermentation
avoided: storing at cool temp, using SO2, or filtering out bacteria

Question 26

what is the difference between gross lees and fine lees?

Answer 26

gross lees and fine lees are both dead yeast cells/grape fragments that are suspended in wine after fermentation.

gross lees: sediment that falls to bottom of vessel in matter of hours. Cause unpleasant aromas.

fine lees: smaller particles that settle more slowly. Often removed gradually during maturation process. Sometimes winemaker keeps fine lees in contact with white wine during pre-bottling maturation to add flavors and texture.

Question 27

What are the 3 main constituents of wine and their approx volumes?

Answer 27

1. Water (70-90%)
2. Ethanol (8-22%) - the main alcohol in wine
3. Sugars (.1-20%)

Question 28

What are the 3 main reasons blending is carried out?

Answer 28

Balance, consistency, style

balance: allowing winemaker adjust balance of wine. For instance, blending free run wine with press wine to increase tannin in red wine
consistency: maintain consistency across bottles, due to variations in fruit or inconsistencies during winemaking or maturation like small differences between wines matured in different barrels
style: some winemakers may create as many blending options as possible to help them achieve a certain house style. options include: Separating different press fractions, fermenting or maturing wine in different vessels, allowing only portion of wine to undergo MLF, using wines from different varieties, vineyard plots and vintages.

Question 29

What are the three main techniques for clarification?

Answer 29

sedimentation: happens in most wines after fermetnation. once gross lees settle into deposit, wine is pumped into a different vessel with sediment left behind. this is called racking
fining: speeds up process by which constituents slowly clump together so that they can be removed before bottling. A fining agent is added to wine. this forms bonds with constitudents and causes clumps to form.

filtration: physically removes particles by passing them through filter. 2 methods:
depth filtration: thick filter - solid parts become trapped inside the material. can remove gross lees
surface filtration: very fine sieve used to trap particles, usually used after wines already passed through a depth filter.

Question 30

What are the three areas in wine that require stabilisation?

Answer 30

tartrate stability: over time wine forms tartrates, which are crystals less soluble in wine than in juice. crystals can be forced to form by chilling wine to 0degrees C. they are then removed by filtration

microbiological stability: yeast and bacteria thrive in wine and grape residues and can spoil wine. wines that have not undergone MLF and are not high alcohol and high acidity are particularly at risk. careful handling and SO2 is required to protect wine.

Oxygen Stability: oxygen dissolved in wine or entered through packaging can cause oxidation, loss of fresh fruit and browning. by avoiding oxygen exposure and topping up SO2, this can be avoided. Bottles can be flushed with carbon dioxide or nitrogen before filling to eliminate oxygen during packaging

Question 31

why are glass bottles preferred over plastic or bag-in-box?

Answer 31

glass bottles do not allow air to get into packaging and do not taint the wine’s flavors. however they are heavy and rigid which means higher transport costs and packing limitations

Question 32

what is main advantage and disadvantage of cork closures?

Answer 32

advantage: allows small amount of oxygen to gradually enter bottle and allows some tertiary characteristics to develop.
disadvantage: small percent of bottles suffer cork taint due to TCA chemical in some corks and gives moldy, cardboard aromas. and some allow too much oxygen in.

Question 33

what style of wine is best suited for screw cap closures?

Answer 33

wines where winemaker wishes to preserve primary aromas. because they provide impermeable seal from air, theypreserve fruit flavor longer than cork.

Question 34

what are ideal conditions for bottle ageing?

Answer 34

cool dark place with constant temp around 10-15 degrees C. Constant humidity and bottles sealed with cork should be lying on side so corks remain moist