Winemaking Ch 7: Oxygen & Oak Flashcards
Human Factors Ch 7
SWA: Define protective winemaking 2 marks; Why might a producer not want to do protective winemaking? 2 marks
See Common Elements in Winemaking SWA taped on blue flashcard (p. 44)
How is oxygen contact avoided during winemaking?
Protective or anaerobic winemaking: (1) Antioxidants like SO2. (2) Grapes picked at night when the effects of oxygen are reduced because chemical reactions occur slower at lower temps. (3) Chilling the grapes when they reach the winery. (4) Filling airtight vessels with CO2 or nitrogen before processing or winemaking. (p. 44)
Why do some winemakers allow exposure to oxygen during the winemaking process?
They argue that protective or anaerobic winemaking make the wine bland or uninteresting and oxygen develops complexity and character. (p. 44)
How is oxygen contact avoided during maturation?
Anaerobic maturation by maturing the wine in inert tanks or vats made of stainless steel or concrete lined with epoxy resin. (1) Vessels are kept completely full and (2) SO2 (antioxidant and antiseptic) is added with levels always monitored. (p. 44) Grapes receive their first dose of SO2 as a spray at arrival at winery. (p. 46)
How would a wine be matured aerobically? What are the effects?
In aerobic maturation, wine is stored in oak vessels for small amounts of oxygen contact. Small barrels: 225-litres barriques have most oxygen/flavor effects with proportionately larger surface area wood to wine. Red wines: tannins soften, primary fruit flavors fade and flavors become more complex, tertiary flavors develop (leather, earth), color becomes paler with hint of brown. Whites: color becomes deeper with hit of orange. (p. 44)
Why would larger oak barrels be used in maturation?
Larger oak vessels allow the wine to be matured longer without effecting the flavors as much as small barrels. For more, ‘deliberate oxidation’ the oak vessels are not completely full and extra oxygen contact can last many years (Oloroso Sherry, Tawny Port, Rutherglen Muscat). Wines develop ‘deliberate oxidation’ tertiary characters of caramel, toffee, and nuts (almond, marzipan, hazelnut, walnut). Note: too much oxidation in maturation can make wine stale, loss of fruit flavors, and bacteria turns ‘oxidized’ wine into vinegar. (p. 44)
How does SO2 serve as an antiseptic and an antioxidant? Why do SO2 levels need to be monitored and replenished?
As an antiseptic, SO2 prevents rot and mildew on grapes, is toxic to bacteria (can develop in grape juice) and certain strains of yeast (not the yeast involved in alcoholic fermentation- SO2 tolerant). As an antioxidant, it protects the grape juice from oxidation. But it slowly becomes ‘bound’ to oxygen and loses its effect so needs to be replenished. SO2 levels are also controlled by law. (p. 44)
What are some of effects of oak fermentation and/or maturation?
Wine can extract tannins and flavors from the oak barrels. Oak tannins give more structure to red and white wines, increasing ‘textural complexity’. Oak adds flavors of toast, vanilla, smoke, cloves (SAT: nutmeg, coconut, butterscotch, cedar, charred wood, chocolate, coffee, resinous). During maturation, oak vessels let in small amounts of oxygen, allowing for tertiary flavors. (p. 44)
What is a particular challenge with using oak?
It is difficult to keep wood vessels completely free of bad yeasts, bacteria, and molds. Wine can be ruined by tainted wood. Hygiene is crucial. (p. 44)
What are the four important considerations in the choice of oak vessels?
(1) Species and origin of oak (European: cinnamon, nutmeg, cooking spices. American: coconut, dill, whiskey tones - video). (2) Size and surface area (small: 225-litre barriques, large barrels: up to 2000 litres). (3) Production: ‘toasting of the barrel’: heating staves and bend into shape (heating process transforms tannins and flavor compounds in the oak, giving notes of toast, smoke, spices). ‘level of toasting’: high temp and long length of heat exposure makes flavors more intense. (4) Age: effects of toasting diminish after each use. New oak imparts more tannins and flavor; second use gives less but more subtle oak flavors, fourth use imparts little flavor or tannin. (p. 46)
