L3: Chapter 7 Common Elements in Winemaking and Maturation Flashcards
Describe parts of the grape.
Seeds & stems - Stems are only available if hand harvested. both contain tannins. seeds have bitter oils.
Skins- the skin & area immediately beneath are the areas where the grape gets its signature varietal character. Also contains tannin and color (more tannins in black grapes).
Pulp -contains water, sugar. and acids. Yeast will use sugar to make alcohol. Tartaric is the most common acid, followed by malic acid.
How is oxygen avoided during winemaking process and why?
Oxygen can reduce primary fruit flavors.
To avoid the effects, some winemakers use sulfur to keep oxygen contact to a minimum.
Grapes can also be picked at night when it is cooler, which reduces risk of oxygen, because chemical reactions occur more slowly at lower temperatures.
Grapes will then be kept chilled until they reach the winery
Once at the winery anaerobic winemaking is used to keep grapes and juice away from oxygen by filling with airtight equipment.
How is oxygen utilized during maturation?
If a wine is made anaerobically and without oxygen, it usually will not benefit from oxygen during maturation and as a result those wine will be stored in airtight inert vats/tanks.
Wines matured in wooden vessels (oak) are in contact with oxygen (aerobic vessel). Small amounts of oxygen will make it through the oak and can help soften tannins & give more complexity to the flavors of the wine.
This results in primary fruits fading and tertiary leather/earth flavors developing.
Color changes as well - reds become paler, browner. Whites become deeper in color with more orange.
What does the size of an oak vessel have to do with oxidization?
The smaller the oak vessel (ie. 225 liter barriques, teh greater the effects of oxygen because there is a larger surface area of wood to wine.
As a result wines are rarely kept for barriques longer than two years. Wines can be matured longer in larger oak vessels.
What is a common oxidative technique for fortified wines?
The maturation vessel will not be completely filled, so that there is a deliberative oxidative style (such as in oloroso sherry, tawny port, and rutherglen muscat).
These wines develop tertiary characters of toffee, caramel and nuts.
What is the general effect of too much oxygen on wines?
Too much oxygen can damage wines resulting in the loss of fresh fruit flavors and taste
How is sulfur dioxide (SO2) used?
Sulfur dioxide (SO2) is used to protect grapes post harvest from oxygen. Anti-oxidant
Also an anti-septic- protects from many strains and bacteria
Because SO2 is toxic, the levels of it are strictly controlled and winemakers try to use as little as possible.
Some SO2 is produced naturally in fermentation.
In addition toxicity, when levels are too high it can make the wine seem harsh and lacking in fruit.
Once used to protect against Oxygen, SO2 becomes “bound” and loses it’s ability to protect. As a result, SO2 must be constantly monitored and replenished to ensure wine remains protected.
What are the impacts of oak on a wine?
-In addition to a level of oxygen introduced in maturation, oak:
–Oak tannins give more structure to red and white wine tannins, increasing textural complexity
–Oak gives aromas and flavors of toast, vanilla, smoke and cloves
(Note: oak vessels must be kept clean to prevent tainted wood which ruins wines).
What are 4 important factors to consider when using an oak vessel?
(1) The species and origin of oak
European & American oak have very different flavor profiles. French oak is known to be the finest.
(2) Size of the barrel
-small vessels (ie. 225-liter barriques & 228 liter piece) have a greater oxidative and flavor impact on wine because of surface area. Compare to vessels which can be in excess of 2000 liters.
(3) Production of oak barrels
-The toasting of the barrel is one of the most important procedures in how a barrel is made. This process is necessary to shape the staves into a barrel. But also it transforms oak tannins and flavors to give notes of toast, smoke and spices.
(4) Age
-The effect of barrel toasting diminishes each time a barrel is used
-after 4 uses a barrel has little flavor or tannin to impart
-New oak is only right for some wines, not all
What are alternatives to oak vessels that can impart oak flavors?
oak staves and chips can be used to impart oak flavors during fermentation or maturation.
Additionally, winemakers can add small controlled quantities of oxygen to wine.
What are inert winery vessels?
Inert vessels do not impart flavors or allow oxygen.
They can be made of stainless steel or concrete.
Stainless steel –used in most modern wineries. Can be made in any shape or size. Temperature control equipment used. Easy to clean.
Concrete vessels– used before stainless steel. Less easy to clean. Thick concrete can be used to regulate temperatures during fermentation and maturation without the need for expensive temperature control equipment.
What typically happens to grapes when they first arrive at the winery for high volume production and premium wines?
All grapes will usually receive their first does of SO2 (to prevent oxidization) when they arrive.
Premium grapes will be sorted to eliminate unripe and rotten grapes.
What happens at the destemming and crushing stages?
Both destemming and crushing are optional processes.
Destemming typically happens for all wines, even premium wines which are hand harvested.
Crushing then breaks the skins of the grapes, and liberates quantities of juice known as “free run juice” This is done while avoiding damaging/crushing the seeds, because seeds produce a bitter oil that will make wines bitter and astringent.
In reds, grapes will macerate/ferment after being crushed.
What is pressing?
Pressing is the process of separating the liquid of the grape from the solid parts of the grape.
In white wines -pressing always occurs before fermentation.
In red wines -pressing happens after fermentation, so that wines can mature/macerate/ferment on the skins (increases tannin).
Seeds must again remain undamaged in this process.
Describe the different types of wine presses that exist.
(1) vertical presses
-This is the traditional style where pressure is imposed on the grape from above using a plate that is lowered and raised w/ either a screw or lever. This is often used in the Champagne region, among other regions.
(2) pneumatic presses
-modern press which consists of an inflatable rubber tube which is surrounded by a perforated, horizontal stainless steel cylinder. The rubber tube allows for pressure to be applied to grapes over a larger area in a controllable way. (some pneumatic presses are built w/ a closed tank to limit the amount of oxygen coming into contact with the juice.
What are “fractions” and why do winemakers separate juices during pressing?
The juice released at the start of pressing is very different from the juice released towards the end.
As a result, winemakers might decide to separate the liquid into “fractions” so that they can treat and blend them into different proportions.
What are “adjustments” in winemaking and when can they be made?
Adjustments are changes to the wine, ie. the sugar, alcohol or acid level, that can occur before, during or after fermentation.
In the EU adjustments are subject to more regulation than anywhere else.
Why and how are adjustments to alcohol made?
Sometimes in cooler climates adjustments are needed to raise the alcohol levels (due to an insufficient amount of sugar for the yeast) in the wine to a satisfactory level.
To do this winemakers may:
(1) Add more Rectified Concentrated Grape Must (RCGM) - which is a colorless, odorless syrupy liquid that increases sugar levels. This addition occurs before or during fermentation
(2) Remove water from the juice in order to concentrate sugar levels leading to higher alcohol. The drawback is this method also concentrates tannins, acids, flavor compounds and any wine faults, so it’s not always desireable. It also reduces the volume of wine that can be sold due to less liquid.
***Wine with alcohol levels that are deemed “too high” can have alcohol removed with modern machinery.
How are adjustments to acid in wine made?
Acid levels may need to be increased if during ripening a grape’s acid has fallen too far.
Acidification is normally carried out by the addition of tartaric acid in powder form. In Europe this practice is only permitted in warmer regions, but is common in warm regions around the world.
In cooler regions, deacidification (reducing acid levels) occurs when the grape acids levels have not fallen sufficiently during ripening. Excess acid may be neutralized by the addition of an alkaline substance.
What is fermentation?
The conversion of sugar into alcohol through the action of yeast.
(heat and flavor are other by-products)
At what temperature will fermentation not happen?
Anything below 5 C or (41 F)
or above 35 C o r(95 F)
