Ch 13 : General Winemaking Options

Question 1

What are the main risks in grape transportation to the winery?

Answer 1

Oxygen
Ambient yeasts
Acetic acid bacteria

Question 2

What are protective and preventative options for grape transport?

Answer 2

Harvesting and transporting at night
Adding SO2 at harvest
Putting grapes in cold storage
Sanitising tools to avoid microbial spoilage
Collecting in small batches to minimise crushing

Question 3

What are the two functions of SO2

Answer 3

Anti oxidative
Anti microbial

Question 4

What techniques would a winemaker use to promote oxygen exposure in the wine?

Answer 4

Cap management
Small wooden vessels
Lee’s stirring and racking
Allowing ullage
Hyperoxidation

Question 5

How would a winemaker protect their wine/must from oxygen?

Answer 5

Minimising ullage
Flushing vessels with inert gas
Adding SO2
Using innert vessels
Fermenting and storing at cool constant temperatures

Question 6

When are SO2 additions most effective?

Answer 6

At crushing, Malo, and bottling. Ideally in larger amounts compared to constant smaller additions throughout

Question 7

How does pH affect SO2 efficacy?

Answer 7

At lower pH, the environment favours the development of molecular SO2 which is most effective. A low pH wine may not require so much SO2 which is cheaper and may help winemakers adhere to laws and guidelines in their region/style (eg organic, AOP etc.)

Question 8

What are the negative affects of oxygen in wine?

Answer 8

Acetaldehyde
Colour change
Biological instability eg. Brettanomyces, acetic acid

Question 9

What are oxidation reactions?

Answer 9

When oxygen acts indirectly on the wine or must by promoting one reaction which develops reactive compounds that may affect colour, flavour etc.

Question 10

What are the most common press types

Answer 10

Pneumatic press and basket press

Question 11

What are the benefits of a pneumatic press?

Answer 11

Can be programmed for different pressures
Can be flushed with inert gas prior

Can be a big up front expense, seen more in mid to large scale winemaking

Question 12

What are the benefits of a basket press

Answer 12

Exposure to oxygen for certain styles
More artisan in nature

Question 13

When would a winemaker add rcgm/sugar to enrich the wine?

Answer 13

After ferment has started as yeast are active and can handle the high sugar levels

Question 14

What options, aside from must enrichment, exist to concentrate grape sugars?

Answer 14

Reverse osmosis
Vacuum evaporation
Cyroextraction

Question 15

How would a winemaker reduce alcohol levels?

Answer 15

Adding water to the must
Removing alcohol from wine post ferment

Question 16

Why would a winemaker expose their white grape must to oxygen before fermentation?

Answer 16

greater long term oxygen stability
increased ageing potential

Question 17

what are the two roles of SO2?

Answer 17

antimicrobial
antioxidant

Question 18

What are the max levels of SO2 permitted for red and white wines in the EU

Answer 18

150 mg/L for reds
200 mg/L for whites

Question 19

what are the three forms of SO2

Answer 19

bound
free
molecular

Question 20

will the proportion of SO2 required be higher or lower at a pH of 3.1?

Answer 20

lower, because there is more molecular SO2 available

Question 21

What are options for grape sorting?

Answer 21

• sorting at picking
• hand sorting
• optical sorting

Question 22

difference between pressing and crushing

Answer 22

crushing releases the juice
pressing removes the juice from skins and seeds

Question 23

what are the most common pressing options

Answer 23

pneumatic press
basket press
screw press
continuous press

Question 24

what constituents can be added to must in enrichment?

Answer 24

dry sugar
grape must
grape concentrate
RCGM

Question 25

What processes can result in must enrichment?

Answer 25

reverse osmosis
vacuum extraction
chilling

Question 26

When is enrichment often carried out?

Answer 26

once ferment has started as yeasts are active

Question 27

when is acidification carried out?

Answer 27

before ferment starts to benefit from effects of lower pH and enhance acid integration during ferment

Question 28

What does yeast need to ferment?

Answer 28

viable temperature, nutrients, nitrogen, no oxygen

Question 29

at what alcohol % do most yeasts species die out

Answer 29

5%

Question 30

what are the risks of ambient ferment?

Answer 30

slow start means potential build up of VA and growth of spoilage organisms (eg. Brett)

Question 31

Why does yeast need nitrogen?

Answer 31

its a nutrient. Without sufficient nitrogen, the yeast gets stressed and produces undesirable sulphur compounds or stops ferment

Question 32

what are common yeast nutrient additions?

Answer 32

Diammonium phosphate (DAP)
thiamine (B1)

Question 33

what are the ferment temperatures for cool, mid, and warm brackets?

Answer 33

cool : 12-16C

mid : 17-25C

warm : 26-32C

Question 34

what are the required conditions for MLF?

Answer 34

18-22C
moderate pH (3.3-3.5)
low total SO2

Question 35

how can winemakers artificially ensure MLF does not occur?

Answer 35

adding the enzyme lysozyme
dropping temperatures
adding SO2

Question 36

how does MLF affect the wine?

Answer 36

less acid, raised pH
colour loss in red wine
microbial stability
flavour modification

Question 37

name two alcohol removal techniques

Answer 37

reverse osmosis
spinning cone

Question 38

how does reverse osmosis work?

Answer 38

• cross-flow filtration removes flavourless permeates of water and alcohol
• this is then distilled to remove the alcohol
• the watery permeate is blended back into the wine