13. General Winemaking Options

Question 1

How to limit the effect of oxygen on must and wine?

Answer 1

• 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

Question 2

How to increase exposure to oxygen?

Answer 2

• 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

Question 3

What is the role of sulfur dioxide?

Answer 3

• anti-oxidant

- anti-microbial

Question 4

What steps are taken at grape reception to the winery?

Answer 4

• Chilling
• Sorting
• Destemming if required
• Crushing (not the same as pressing)

Question 5

What are the two types of presses?

Answer 5

Pneumatic - programmable, flushable with inert gas, avoids oxygen exposure
Basket - introduces oxygen

Question 6

What are the 5 must adjustments?

Answer 6

• Enrichment
• Reducing alcohol
• Acidification
• Deacidification
• Adding tannins

Question 7

What is must enrichment?

Answer 7

Chaptalization. Adding sugar in whatever form - dry, RCGM, etc

• or removing water
• common in cool regions

Question 8

What is the most common way to reduce alcohol?

Answer 8

addition of water

-however, this dilutes aromas/flavors

Question 9

What is acidification?

Answer 9

Typically addition of tartaric acid. Routine in most warm regions of the world

Question 10

Describe deacidification

Answer 10

-Adding calcium carbonate or potassium carbonate. Lowers acidity by formation and precipitation of tartrates.

Question 11

What is alcoholic fermentation?

Answer 11

conversion of sugar into ethanol

Question 12

What does yeast need for fermentation?

Answer 12

• viable temp range
• access to yeast nutrients
• nitrogen
• absence of oxygen

Question 13

Besides alcohol, what does fermentation produce?

Answer 13

• Volatile acidity
• very small amounts of sulfur dioxide
• wine aromatics - from precursors (thiols, terpenes)
• -from yeast - esters, sulfur compounds, acetaldehyde
• Glycerol

Question 14

What is the most common species of yeast in winemaking?

Answer 14

saccharomyces cerevisiae

Question 15

Advantages and disadvantages of ambient yeast

Answer 15

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

Question 16

Advantages/disadvantages of cultured yeast?

Answer 16

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

Question 17

Low levels of nitrogen during fermentation lead to what?

Answer 17

Low levels of nitrogen can stress the yeast causing them to produce undesirable sulfur compounds (rotten egg smell) or even stop fermentation.

Question 18

Name the three types of fermentation vessels

Answer 18

• stainless steel
• concrete
• wood

Question 19

Advantage/disadvantage of stainless steel fermenters?

Answer 19

-high level of control
-hygiene
-no added flavors
-protection from oxygen
-high level of mechanization
Dis:
-expensive initially

Question 20

advantage/disadvantage of concrete fermenters?

Answer 20

-maintain even temp more efficiently than stainless
-thought to have convection currents that mix must and lees during maturation
dis:
initially expensive

Question 21

advantage/disadvantage of fermenting in wood

Answer 21

-retains heat
-adds small amount of oxygen
-can be reused = inexpensive in long term
dis:
initially expensive

Question 22

What are the 4 outcomes of MLF?

Answer 22

• 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)

Question 23

What are two post-fermentation adjustments?

Answer 23

• Removal of alcohol

- Color