Common Elements in Winemaking and Maturation Flashcards
what happens during alcoholic fermentation?
yeast converts sugar in the grape juice to alcohol
What are wines that have very little human intervention?
natural wines
what is the process of oxygen reacting with grape juice called?
oxidation
If you want more fruit flavors in the wine, what is one way to obtain this?
decrease oxygen by using more sulfuric dioxide
why are grapes picked when its cooler?
it reduces the effects of oxygen because the chemical interactions are slowed in cooler temperatures
what is protective or anaerobic winemaking?
the process of filling an airtight vessel with either carbon dioxide or nitrogen before they are used for grape processing or wine making
How do you mature wines that have had no oxygen during the winemaking process?
oxygen should not be used during maturation process. either inert steel or cement vats should be used and kept airtight
what kind of vessels are wines that matured in contact with oxygen in?
typically oak - may be watertight but is not airtight.
what can oxygen do to wines during maturation process?
soften tannins, and give more complexity to the flavors, eventually giving tertiary flavors (leather and earth)
how long are wines typically kept in barriques?
no longer than 2 years
the technique of not filling the oak barrel completely to leave room for oxidation is done with what types of wines?
fortified wines Olorosso Sherry, Tawny Port, and Rutherglen Muscat - gives smells of toffee, nuts and caramel
how is sulfur dioxide used in a wine?
acts as an antioxident and antisepti. It protects newly harvested grapes. wines can become harsh if too much used
what happens when SO2 protects the grape juice and wine from oxidation?
it becomes “bound” and can no longer have a protective effect
what kind of flavors does oak give to wine?
toast, vanilla, smoke and cloves
what are the four specific factors winemakers need to consider when looking at oak
- species and origin of oak
- size
- production of oak barrels
- age
why do smaller barrels have more impact on wine?
more of the wine is in contact with the surface of the barrel
what is one of the most important parts of the production of an oak barrel?
toasting it
what are some effects of heating an oak barrel?
the staves bend into shape, transforms the flavors and tannins (notes of toast and spice) and the amount of heat will (level of toasting) affects the flavors contributed to the wine.
What happens to a barrel after it is toasted?
the time each barrel can be used is diminished (the younger the barrel the more the flavor)
What are some alternative to oak barrels that can be used to still get oak flavors?
small planks of oak (staves), oak chips, or even adding small quantities of oxygen to the barrel
what is an inert vessel?
one that is not made of wood. Can be stainless steel or concrete. they do not add any flavors on the wine or allow oxidation.
why are stainless steel vessels used?
not to allow any new flavors in the wine and also easy temperature control
Why are concrete vessels used?
they are lined with epoxy resin which provides a waterproof barrier. not used frequently any more and most have been replaced by stainless steel
when do grapes receive their first dose of SO2
when they arrive at the winery
what happens if seeds are crushed during the crushing process?
they can release bitter oils and tannin and make the wine become more unpleasant, astringent, and bitter
when does pressing occur for white grapes?
before fermentation
when does pressing happen for red grapes?
after fermentation
what is a pneumatic press?
a press with a inflatable rubber tube within a perforated, horizontal, stainless steel cylinder, which makes it possible to apply pressure over a large area in a controlled way
when can adjustments to the wine be made?
before, during or after fermentation
what is grape juice commonly referred to as?
must
what will a winemaker do in a region where there is a cooler climate and there is not enough natural sugar to give it a satisfactory level of alcohol?
carry out a process called enrichment where they increase sugar levels in the juice by adding RCGM (Rectified Concentrated Grape Must) which is a colorless, ordorless, syrupy liquid. Can be added before or during fermentation
what is chaptalisation?
where sugar from sources other than grapes are added to juice (ex sugar beet)
what is a way to make wine higher in alcohol besides adding sugar?
removing water from the juice which concentrates the sugars, but also concentrates everything else (tannins, acids, flavor compounds, and faults).
What is acidification?
addition of tartaric acid in powder form to grape juice
Where is acidification permitted in Europe?
only in warmer regions
What is deacidification?
reducing of acid levels in grape juice - typically done by adding alkali (the chemical opposite of acid)
what is alcoholic fermentation
the conversion of sugar into alcohol and CO2 utilizing yeast.
what is the yeast species that is responsible for the most wine fermentation
Saccharomyces cerevisiae - it can tolerate high levels of alcohol and SO2
at what temperature will alcoholic fermentation start?
5 C
what might cause alcoholic fermentation to stop before all the sugar is consumed?
if the yeast runs out of nutrients they need other than sugar or the temperature is above 35 C. sometimes the sugar level can be so high the yeast can struggle to start in the first place
if a winemaker wanted to, how would they stop the fermentation before all the sugar has been converted to alcohol?
either killing or removing the yeast by adding S02 or grape spirit. yeast can then be removed using filtration after the fermentation has been temporarily halted by chilling the wine below 5 C
what are the two important ways a winemaker can control fermentation?
yeast and temperature management
what are the two types of yeast that the winemaker can add to the grape juice?
the various ambient yeast strains found on the grape bloom or in the winery; or adding a cultured yeast.
what does fermenting at lower temperatures do?
avoids the loss of the most volatile aromas which often have floral characteristics. it can also develop more fruity flavors in white wines.
what does fermenting at higher temperatures do?
extracts color and tannins from black grape skins
how can excess heat be released?
pumping over
when does malolactic fermentation take place?
after alcoholic fermentation
how is malolactic fermentation carried out?
lactic acid bacteria - converting the tart malic grape acid into softer lactic acids which reduce acidity and create a buttery flavor and produces CO2
what are gross lees?
the suspended particles that are left in wine directly after fermentation which will fall to the bottom of the storage vessel within a matter of hours. they can cause unpleasant aromas in the wine if not removed.
what are fine lees
smaller particles that settle to the bottom of the vessel after fermentation more slowly than gross lees. often removed gradually through maturation process.
when would a winemaker do if they want to retain as many primary fruit aromas as possible?
bottle the wine only after a few months of maturation in an inert vessel
when can blending take place?
at any stage, but mainly carried out after fermentation or during maturation
what is blending used for?
improve balance, attain consistency, or achieve a certain style.
why is consistency important?
significant variation among bottles can be seen as a fault.
what are three main techniques a winemaker can use to ensure the wine is perfectly clear?
- sedimentation
- fining
- filteration
when does sedimentation occur?
after fermentation has finished
what is sedimentation?
after the gross lees have settled in a deposit, the wine is slowly and gently pumped into a different vessel leaving the sediment behind (racking). Fine lees will continue to form during maturation causing repeated rackings to be needed
why is sedimentation a slow process and what can speed it up?
it relies on gravity to pull the suspended particles to the bottom and gravity is a weak and slow force. it can be sped up by putting the wine into a centrifuge.