13. General Winemaking Options Flashcards
How to limit the effect of oxygen on must and wine?
- Avoid headspace between wine and top of barrel, “topping off” (ullage)
- Use of inert gasses to flush oxygen from vessels
- addition of sulfur dioxide.
- Impermeable containers
- cool, constant temps
How to increase exposure to oxygen?
- Cap management techniques that spray or splash the must
- small wooden barrels
- increasing number of lees stirring during again, racking, anything that involves removing bung.
- allowing ullage in containers w/o inert gas
- hyperoxygenation, micro oxygenation
What is the role of sulfur dioxide?
- anti-oxidant
- anti-microbial
What steps are taken at grape reception to the winery?
- Chilling
- Sorting
- Destemming if required
- Crushing (not the same as pressing)
What are the two types of presses?
Pneumatic - programmable, flushable with inert gas, avoids oxygen exposure
Basket - introduces oxygen
What are the 5 must adjustments?
- Enrichment
- Reducing alcohol
- Acidification
- Deacidification
- Adding tannins
What is must enrichment?
Chaptalization. Adding sugar in whatever form - dry, RCGM, etc
- or removing water
- common in cool regions
What is the most common way to reduce alcohol?
addition of water
-however, this dilutes aromas/flavors
What is acidification?
Typically addition of tartaric acid. Routine in most warm regions of the world
Describe deacidification
-Adding calcium carbonate or potassium carbonate. Lowers acidity by formation and precipitation of tartrates.
What is alcoholic fermentation?
conversion of sugar into ethanol
What does yeast need for fermentation?
- viable temp range
- access to yeast nutrients
- nitrogen
- absence of oxygen
Besides alcohol, what does fermentation produce?
- Volatile acidity
- very small amounts of sulfur dioxide
- wine aromatics - from precursors (thiols, terpenes)
- -from yeast - esters, sulfur compounds, acetaldehyde
- Glycerol
What is the most common species of yeast in winemaking?
saccharomyces cerevisiae
Advantages and disadvantages of ambient yeast
Adv:
-can add complexity resulting from yeast species producing different aroma compounds
-it’s free
-yeast population may be unique to a place/region
-may be used as part of marketing
DIS:
-fermentation may start slowly and may build up unwanted VA and spoilage organisms, leading to off flavors
-fermentation to dryness takes longer
-risk of stuck fermentation
-cannot guarantee a consistent product
Advantages/disadvantages of cultured yeast?
adv: -fast, reliable fermentation to dryness -low levels of VA -less danger of spoilage organisms -helps produce consistent product -winemaker's choice of yeast can affect wine style Dis: -cultured yeast may lead to similarity of fruit expression -adds cost
Low levels of nitrogen during fermentation lead to what?
Low levels of nitrogen can stress the yeast causing them to produce undesirable sulfur compounds (rotten egg smell) or even stop fermentation.
Name the three types of fermentation vessels
- stainless steel
- concrete
- wood
Advantage/disadvantage of stainless steel fermenters?
-high level of control
-hygiene
-no added flavors
-protection from oxygen
-high level of mechanization
Dis:
-expensive initially
advantage/disadvantage of concrete fermenters?
-maintain even temp more efficiently than stainless
-thought to have convection currents that mix must and lees during maturation
dis:
initially expensive
advantage/disadvantage of fermenting in wood
-retains heat
-adds small amount of oxygen
-can be reused = inexpensive in long term
dis:
initially expensive
What are the 4 outcomes of MLF?
- reduction in acidity and rise in pH (softer, smoother wine style)
- Some color loss in red wines
- Greater microbial stability (prevents MLF from happening spontaneously later)
- Modification of flavor (slight loss of fruit character w/addition of buttery notes)
What are two post-fermentation adjustments?
- Removal of alcohol
- Color
