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what are the components of wine supplied by the grape juice
sugar, acid, minerals, and nutrients, the polyphenols which embrace the tannins for 'grip' and the anthocyanins for color and crucial flavoring substances.
what is the predominant alcohol in wine
- ethyl alcohol also known as ethanol.
- all alcohols have chains of carbon atoms (C) with hydrogen atoms (H) attached.
why are higher alcohols/fusel oils called "higher alcohols'?
- they have a higher boiling point then ethanol.
- They remain behind at the end of distillation where they are a component of the 'tails'
is alcohol content important to taste?
yes but because it affects the mouth feel not the flavor
what are the two main acids in wine
tartaric and malic
what two acids are produced as a direct result of alcoholic fermentation
lactic acid and succinic acid
what causes acetic acid?
the oxidation of alcohol especially under the influence of acetic bacteria.
what three components make up the balance of all wines
alcohol, acidity and residual sugar
what is residual sugar
the sugar left over after fermentation.
what are the three ways to sweeten a dry wine
- suss-reserve (preserved grape juice)
- RCGM (rectified concentrated grape must)
- adding sugar to enrich before fermentation
what are the sugars present in must
fructose and glucose
in enrichment what happens to the sucrose
it is transformed into equal parts fructose and glucose by the acids in a process called inversion.
what is the next most abundant constituent of wine after water and alcohol?
- Glycerol (or glycerine).
- *the glycerol concentration is directly proportionate to the sugar content in the grape juice.
What is Glycerol?
colorless, viscous liquid with a slightly sweet taste. plays a considerable role in mouthfeel.
what is a ketone?
a product of oxidation, not of ethanol but as part of the complex metabolism of sugars. its effect in wine is 'diacetyl' a substance with a powerful buttery or toasty aroma. They have a powerful binding effect on sulfur dioxide thus adding to the problem of acetaldehyde.
what are the deposits in the bottom of some wine bottles?
proteins or tartrate crystals.
what is 'the gross lees' in terms of racking?
the dead yeast cells, and cellular matter from the grape, that fall to the bottom of the fermentation barrel.
what are the two purposes of fining? and what are most fining agents made of
fining is a type of clarification and its purposes are the prevention of haze, and the removal of some of the tannins to improve the balance of the wine. They are typically made from a naturally occurring purified protein.
what are colliods?
colliods are proteins whose molecules are large but not sufficiently large to render themselves visible or be removed by a filter. There are stable and unstable colliods. Unstable colliods carry a electrostatic charge when youthful and repel each other; with age they lose this charge and begin to clump and form solid matter.
name 7 fining agents
- albumin= egg whites
- gelatin= bones and hides
- casein= milk
- isinglass (dryfine)= fish guts
- bentonite= clay from volcanic ash
- silica gel (kiesesol)= mineral silicon dioxide
- PVPP= vinyl product (must be filtered)
what are the three fining agents used for reds
bentonite, egg whites, and gelatin. the others are only used for whites.
what is blue fining
potassium ferrocyanide. it is for the removal of excess iron and copper (which cause haze and are catalysts to oxidation). Must be done by a qualified chemist because if done incorrectly it can convert to cyanide.
what are the three processes for tartrate stabilization?
1. Cold Stabilization= wine is chilled to just above freezing point (-4C for 12% wine) and then is stored for up to 8 days in insulated tanks. This causes crystallization and then removal. not very effective.
2. Contact Process= chill wine to 0*C then add finely ground particles of potassium bitartrate (what the crystals are made of if left to form) and then stir vigorously for 1-2 hours. at the end the wine is filtered while still cold and the crystals are separated out and added to the new batch.
3. electrodialysis= specially selective membranes allow the passage of potassium, calcium and tartrate ions under the influence of an electrical charge.
what type of fermentation is malolactic fermentation
a bacterial secondary fermentation.
what group of compounds do flavanoids belong to?
which pressing method will give you the most oxidation and which will give you the least?
- most= pump over
- least= punch down
which grape component contributes most to the tannins
what family do yeast belong to?
what is the best way to stop a fermentation from completing?
chill the wine, then rack and add So2
what are the roles of enzymes in winemaking both good and bad?
enzymes act as a catalyst for chemical reactions, the good ones help with starting fermentation, and the bad ones help with oxidation (oxidases)
who was Louis Pasteur and why was he important.
He discovered that it was the presence of microorganisms that made fermentation occur.
who was rudolph steiner?
An austrian philosopher who was the first person to elucidate the principles of biodynamic farming.
what is Veraison?
Veraison is the point in maturity in the grape where the skins begin to change color and the grape begins to soften. Also the Carbs are becoming sugars. The Malic and Tartaric acids are equal; the malic begins to drop and the sugars begin to increase.
what are the three inert gasses used in winemaking
carbon dioxide, nitrogen, and argon
how many years must you be organic before you can be certified as such?
when should you do a acid adjustment? and why?
before fermentation so that the changes can 'marry' more thoroughly and make a more harmonious wine
what is a wild yeast?
wild yeasts are yeasts that are indigenous. they are found on the grapes, in the vineyards, and on all surfaces of the winery.
what are the three main bacteria responsible for malolactic fermentation?
Lactobacillus, Leuconostoc, Pediococcus.
Name the types of Cap Management
- Punch Down
- Submerged Cap
- Pumping Over (pump liquid from the bottom over the top)
- Delestage (drain one vat then return over the skins)
- AutoVinificator (carbon dioxide pressure)
- Rotary Fermentor (cement mixer one)
what is cold soaking
a form of skin contact
what is the oldest design of grape press still used today?
which press introduces the least amount of oxygen?
yeast cells are anaerobic as well as aerobic. which of the two can produce alcohol
what are the benefits of cultured yeasts?
a more standard wine, higher alcohol, predictable result.
most of the color is extracted from the skins within how many hours after crushing?
what are the three ways of making rose?
saignee, double pasta, Vin d'nuit.
how is fining different then racking?
fining is adding an agent to remove things whereas racking doesn't add anything it allows things to settle and then takes the juice off. fining removes colliods and stabilizes wine.
what is the difference between depth filtration and absolute filtration?
- depth filtration happens within the structure whereas absolute happens on the surface of the filter.
- depth filtration is cheaper.
- depth filtration lets particles through and absolute does not.
- depth can be used at any stage in winemaking, absolute can only be the last round before bottling.
what is Diatomaceous Earth (DE)? and what filter would you use with it?
DE (also known as Kieselguhr) is an earth that is mined in germany and consists of the skeletal remains of diatoms-tiny sea creatures. It is used in depth filtration.
what kind of filtration is 'plate and frame'?
plate and frame, aka pad filtration, aka sheet filtration is another form of depth filtration.
when using a membrane filter what pore size should be used to remove all bacteria and yeasts?
- .45u is needed for all bacteria and all yeasts.
- *.8u removes all yeasts but not all bacteria and is used in red wine alot.
what kind of filtration is cross-flow
its a membrane or absolute.
how do processing aids differ from additives?
Processing aids are something that leaves the wine, additives are something that stays with the wine until consumption.
what are the methods of clarification?
when do you settle a white wine? and what precent of solids should remain?
before fermentation. and .5-1% for fermentation control.
what is the main wine yeast?
at what rate does yeast convert sugar to alcohol?
- *the warmer the ferment the lower the alcohol.
name some of the additives in wine.
- sulfur dioxide-
- ascorbic acid (Vitamin C, antioxidant)(can produce hydrogen peroxide, and brown wine)
- sorbic acid/potassium sorbate (stops yeasts from fermenting)(smell of geranium leaves)
- Acacia (prevent crystal tartrates)
- Tartaric acid
- citric acid (treating high levels of iron)(can produce excess VA)
- copper sulfate
- lysozyme (kills certain bacteria by degrading cell walls)
what are the four properties of sulfur dioxide?
- Antiseptic (anti-microbial)
what makes the total So2
free So2 + bound So2
what is K-meta? and what percentage of sulfur dioxide is released as So2?
K-Meta =Potassium Metabisulphate. it is a white powder that releases sulfur dioxide at 57% of its weight
what causes an unwanted secondary fermentation?
residual sugars and viable yeasts in wine after non-aseptic bottling.
what level should the TA (total acidity) be at for red wines?
- 1% is too tart, .4% is flat.
Common wine faults?
- tartrate crystals
- foreign bodies
- musty taint
- secondary ferment
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