Winemaking Flashcards
describe the influence of oxygen in wine making
a winemaker wanting to make a wine dominated by primary fruit, oxygen contact is kept to a minimum
grapes are harvested at night
when in winery juice is kept away from oxygen by filling airtight equipment with carbon dioxide or nitrogen - this is anerobic/protective winemaking
a question of winemaking style could be to keep oxygen contact for complexity and character
Describe influence of oxygen in maturation
wines matured aerobically - intact with oxygen are stored in oak
small amounts can interact with wine, softening tannins and giving more complexity of flavours, tertiary and secondary aromas develop
small vessels (225l barriques) have more contact with oxygen - smaller barrels rarely age for more than 2 years
oxygen effects can also occur if container is not completely full (olorosso, port, rutherglen muscat) - pronounced caramel, toffee, nut
what can extreme contact with oxygen do?
wine will lose fruit flavour become stale and oxidized being unfit for sale
can turn to vinegar
what acts as an antiseptic and anti oxidant
so2
strictly controlled by law
if too high wine can harsh and lack fruit
how does so2 act as an antiseptic vs antioxidant
anti septic - toxic to yeast and bacteria that is unwanted
anti oxidident - protects grapes and juice from oxygen effect - once doing this it becomes bound, losing effect so it needs monitoring and replenishing
oak tannins give?
structure and textural complexity
what is a con of oak?
hygiene - difficult to keep free from yeast, bacteria, mould
what does the heating of oak barrels do
transforms tannins and flavour compounds in the oak giving sweet spice and toast
the temperature and length of heat exposure affects this
how can you get a oxidized effect in wine with oak chips or staves
adding a small amount of controlled oxygen to the vessel
how can you regulate temperature in stainless steel vats?
sleeves on the outside or internal coils that cold or hot liquid can be circulated
pros and cons of concrete vats?
harder to clean and maintain
cheaper to regulate temperature
briefly describe the grape processing process
1) grapes arive at winery, receive first dose of so2 and are sorted and checked (for premium)
2) optional destemming and crushing, crushing releases free run juice but should be careful not to crush the seed releasing oil and tannin causing unpleasant and astringent tastes
3) pressing, separating liquids and solids
white wine happens before ferment
red wine happens after ferment
what is a pneumatic press?
inflatable rubber tube tube with a preferred horizontal stainless steel cylinder
this applies pressure to a large area in a controlled way, closed tank to keep away from oxygen
how can juice be seperated during pressing?
the juice at the beginning vs end of pressing is different in flavour and texture, it is seperated into different pressings called fractions and can be blended in different proportions to create a certain style
what 3 things may need adjustments in winemaking?
sugar, alcohol, acid
why may there be insufficient sugar in grapes?
cooler climates
what is RCGM
Rectified concentrated grape must
a colourless, odourless syrup that raises alcohol because there is more sugar to ferment
what is chaptilisation
adding sugar from sources other than grapes (eg: beet)
besides enrichment and chaptilisation, how can a winemaker raise sugar levels?
remove water from the juice
this concentrates sugar but also tannin acid and flavour compound and any faults, also reduces volume of juice
can you remove alcohol from wine?
yes with modern machinery
how is acidification carried out?
addition of tartaric acid in powder form - permitted in warm regions of europe and common in warmer regions around the world
how is deacidification carried out?
common in cooler regions, it is neutralized by addition of alkali (chemical oppisite of acid)
the yeast species that is responsible for majority of wine fermentation’s is?
saccharomyces cerevisiae
why is SC (yeast) the majority yeast used?
tolerance to high alc and so2 levels
what is the temperature fermentation starts at
it will not start if it’s below 5 celcius
why could fermentation stop early or struggle to start?
if yeast run out of nutrients they need (other than sugar) or if temp goes over 35 celcius
when the sugar level is very high the combination of high sugar and high alcohol may cause yeast to struggle to start fermentation
if a winemaker wants to stop fermentation before all the sugar has been converted to alcohol it can be achieved by?
killing or removing yeast
this can be done by adding so2 or grape spirit
how can yeast be removed?
filtration, after the fermentation is haunted by chilling wine to below 5 celcius
what are the choices a winemaker makes regarding yeast?
whether to use ambient yeast found on grape bloom and in winery or by adding a cultured yeast
ambient yeast can produce complex flavours but the winemaker cannot control what yeast is present - also causes variations between batches
cultured yeast consistently preform and produce attractive flavours - some argue it limits complexity
what does controlling the temp of fermentation help?
if it becomes to hot yeast will die
fermenting at lower temps avoids loss of most volitile aromas which often have a floral character and can encourage fruit flavour
higher temps are necessary for extraction of colour and tannins
when and how is MLF carried out
after fermentation by lactic acid bacteria, concertina tart malic grape acid into soft lactic acids
it softens acidity and creates buttery flavours producing co2
it may be encouraged by raising temperature and not adding so2 after fermentation and can be avoided by storing at cool temperatures adding so2 and filtering bacteria
what are gross lee’s
the sediment of dead yeast cells and grape fragments this is heavy and falls to the bottom of vessel within hours causing unpleasant aromas if not removed
what are fine lee’s
finer particles, they are often removed gradually however a winemaker may chose to keep a white in contact with them for extra flavour and texture
if a winemaker wants to retain as many of the primary fruit aromas as possible the wine is likely to be bottled?
after only a few months of being stored in an inert vessel
to survive medium or long term aging wines need?
sufficient tannin, acidity and/or alcohol and flavours that will be worth wile
what can blending achieve?
balance - eg free run blended with press to increase tannin
consistency - different barrels or vessels need blending together in a large bay to smooth inconsistencies or from variations in fruit/harvesting time
style - could include seperating press fractions, fermenting in different vessels or only allowing a portion of wine to go through MLF
what are 3 methods of clarification?
sedimentation, fining, filtration
what is the process of racking?
wine slowly pumped into a different vessel leaving sediment of lee’s behind - clarity can be improved through repeated racking
this process can be accelerated by putting wine in a centrifuge- very expensive
what is the process of fining?
wine constituents slowly clump together, fining speeds this process up so they can be removed before bottling
adding a fining agent bonds with constituents and and are removed by filtering
some wine makers do not because they find it effects flavour and texture
what is the process of filtration?
physically removes particles from wine as it is passed through a filter after fermentation and during maturation to remove gross and fine lee’s quickly
what are the 2 methods of filtration?
depth filtration - used for gross lees and can handle very cloudy wines
surface filtration - removes fine sieves- expensive and clog up easily so used after a depth filter - referred to as sterile filtration
some winemakers believe filtration effects texture
3 stabilization methods are?
tartrate
microbiological
oxygen
explain tartaric stability
tartaric acid is less soluble than grape juice and it can form crystals - harmless and flavourless
cool temps accelerate the formation of them - so if matured a long time in cool cellar prior to bottling - they will develop
or they can be forced to form by chilling wine to 0 for a short time and then removed by filtration
which wine may be subject to microbiological stability easier?
a dry high acid wine that has gone through MLF
or a wine with low to medium alcohol low acidity and little RS
how can you prevent microbiological instability
so2
how can a winemaker avoid oxygen at bottling
flushed with carbon dioxide or nitrogen prior
what are cheaper alternatives to the pricy transport and cost of bottles
lighter weight bottles or transporting in bulk to be bottled where the wine will be sold
why do plastic and bag in box wines need to be consumed quickly from bottling?
oxygen contact can lose freshness and fruitiness
what causes corn taint?
TCA - mouldy and carboard like aroma
what is the premium conditions for bottle maturation
10-15 celcius, humidity, lying on side to keep cork moist and optimum seal is retained
