Wine Components Flashcards
Wine components
Water: 85% by vol depending on alcohol and sugar and critical for how a wine flows
Alcohol: Ethanol formed during fermentation and dominant form of alcohol. Slightly sweet smell. Sense of sweetness, bitterness, and oral warmth and fullness of the body and mouth feel. Alcohol above 14.5 reduce volatility of aromas and increase sense of bitterness. Wines with high alc must have sufficient fruit concentration to be in balance.
Acids
Principle acids tartaric and malic come from the grape (2/3 in final wine). Others; lactic, aceitc are produced in fermentation or malolactic conversion.
Volatile acidity (vinegar smell) is acetic acid. Present in all wines in low levels and is a fault when excess. Reacts with alcohol to become ethyl acetate (nail polish remover), also a fault when excess
Acidity contributes to structure of the wine; making it refreshing and should be in balance with fruit concentration and RS. High acid makes wine appear lean on palate, excessive is tart, lack is flabby
Perception of acid impacted by sugar (seems lower in Riesling). Can impact taste; high malic in Chablis.
Total acidity and pH are linked but not correlated due to buffering effect of other molecules (potassium). High acidity is usually low pH.
Measured as Total Acidity (sum of all acids)and expressed as g/L. Typ in range of 5.5 g/L to 8.5 g/L. In FR may be expressed as sulfuric acid (ratio b/n sulfuric and tartaric)
pH is a scale for the concentration of effective acidity of a solution. Typ 3 - 4 with lower being more acidic. Logarithmic so a 3 is 10x more than 4. Lots of impact in winemaking. Low pH increases microbiological stability of a wine, increases SO2 effectiveness, gives a bright red color, enhances ageability.
Wine Aromatics
Aromas from grapes: Methoxypyrazines: grassy green pepper; Rotundone: pepper
Fermentaton aromas due to precursors in grapes: not aromatic until fermentation occurs. Thiols such as 4MMP box tree aroam in Sauv Blanc; Terpenes giving fruity floral aromas like linalool and geraniol in Muscat.
Aromas from fermentation and by-products.
Esters: formed by the creation of certain acids and alcohols; majority by actions of yeast in fermentation. Fresh fruity aromas critical for young wines. Isoamyl acetate is banana in Beaujolais. Most are unstable and break down a few months after fermentation.
Acetaldehyde: occurs due to the oxidation of ethanol. Masks fresh fruit aromas and a fault in most wines, but important in Fino Sherry
Diacetyl: buttery aroma assoc with malolactic conversion
Yeasts can produce reductive sulfur compounds during fermentatin and lees aging. can vary from struck match which may be desirable to rotten eggs; a fault
Aromas from other: vanillin from oak; eucalyptol volatized from eucalyptis trees by heat and absorbed into waxy layer of grape skins.
Residual Sugar
EU Classification of Sweetness for still wines
Takes into account the amount of sugar and total acid
Dry / Sec / Trocken: up to 4 g/L RS or 9 g/L if TA as Tartartic Acid g/L is not more than 2 g below RS. i.e. a 9g/L RS wine can be dry if TA is 7 g/L
Medium Dry / Demi-Sec / Halbtrocken: more than 4 g/L RS and not more than 12 g/L or up to 18 g/L provided TA is not more than 10 g/L below RS. So can be 18 if TA is 8
Medium / Medium Sweet / Moelleux / Lieblich: more than 12 not exeeding 45 g/L
Sweet / Doux / Suss: more than 45
Glycerol
Derived from sugar in grapes
Occurs in higher levels in wines from botrytised grapesand carbonic maceration
Contributes smoothness, perception of fullness to body, and slightly sweet taste
Phenolics
Occur especially in seeds, skins, stems
Include anthocyanins (color pigment) and tannins.
Tannins bind with proteins in the mouth giving a drying sensation on the palate.
The perception of tannins can be impacted by things. A little RS can make them softer where high acidity more astringent.
Unripe tannins are bitter and never desirable. Level and nature of tannins and role in balance and structure is critical to quality.
