Unit 4 - Lesson 4 - Grape

Question 1

Difference in grape must fermentation and malt or others?

Answer 1

1. High starting sugar concentration
2. low pH value (<4 pH) stresses yeast
3. Brix is higher from high sugars
4. Ferment without climate control meaning cold winters slow fermentation
5. Maybe nutrient deficient due to laws no adding
6. With nat fermentation low yeast count to start

Question 2

Problem with high Brix?

Answer 2

Potential increased osmotic pressure on yeast

Could lead to more esters

Question 3

What are typically the only items checked for grape must?

Answer 3

Brix and pH

Maybe for visible bacteria or yeast in a lab

Question 4

Why is yeast assimilable nitrogen (YAN) important

Answer 4

Health of the yeast

Question 5

What happens if YAN is too high or too low

Answer 5

Can create hydrogen sulphides

Question 6

What is typical if winemakers do not check YAN?

Answer 6

Adding 100-300 mg/L of nitrogen

Question 7

What is the problem with just adding DAP (di-ammonium phosphate). DAP is an inexpensive, inorganic nitrogen source?

Answer 7

It doesnt provide other nutrients

Question 8

What are some other nutrients that may be added?

Answer 8

Yeast hulls
Sterols and fatty acids
Free amino acids
Folic acid
Zinc
Magnesium

Question 9

What yeast is typically chosen for brandy?

Answer 9

1. Select a commercial strain suitable for wine or spirits production.
2. Allow the yeasts naturally present in the juice or on thegrapesto proceed with fermentation.

Question 10

What are commercial yeast strains for wine, what form?

Answer 10

Dry
Only need it once a year
It is simple, economical and consistent

Question 11

Torulaspora delbrueckii

Answer 11

yeast species produces pleasant aromatic profiles in wine. It also reduces acetic acid and acetaldehyde levels in wine

Question 12

Metschnikowia

Answer 12

Wine yeast not capable of fermenting high amounts of sugar, but do produce an array of fruity aromas

Question 13

Brettanomyces

Answer 13

A widely studied genus of yeasts, prized by some winemakers, and feared by others. They produce volatile phenols that may contribute smoky, medicinal, and barnyard aromas which are considered off-flavours to some winemakers in various parts of the world.

Question 14

Saccharomycescerevisiae

Answer 14

Common in vineyards around the world

These yeasts are usually the primary consumers of juice sugars, and thus produce the bulk of the wine’s alcoho

Question 15

Why use natural yeast for brandy?

Answer 15

1. Complex flavor
2. Cheaper than commercial
3. Law may ban eg Calvados
4. Marketing - Artisan/Craft

Question 16

How does natural yeast fermentation profile look?

Answer 16

1. Crush juice is immediately available for natural yeast
2. non Saccharomyces starts fermentation
3. Saccharomyces grows and takes over
4. 24-48 hr Saccharomyces is usually dominate

Question 17

Why would a natural wine maker use cold maceration?

Answer 17

To let other yeast flourish before Saccharomyces takes over

Question 18

What is the hybrid approach some yeast companies are doing for natural wine?

Answer 18

Isolating those beneficial natural yeasts other than Saccharomyces
Cultivating while keeping unwanted out

Question 19

Style of fermenters in wine?

Answer 19

Cylindro conical like beer

Question 20

What are key points of wine fermenters?

Answer 20

1. Solid construction
2. Easy to clean
3. Taller than wide 2:1
   4, Option to have cooling ability

Question 21

What is MLF?

Answer 21

It is not a alcohol fermentation
Malic acid is turned to lactic acid

Malic is tart / Lactic soft creamy
Also creates Diacetyl

Question 22

When does MLF occur?

Answer 22

After fermentation

Question 23

Kloeckera apiculata

Answer 23

A species of yeast naturally present ongrapesfrom all over the world. It is usually not very competitive with other yeasts, and can be kept at bay by them. However, given the opportunity, this yeast can produce large amounts of ethyl acetate.

Question 24

Acetobacter

Answer 24

A genus of bacteria that forms films on top of wine that has been exposed to the air for too long. These bacteria metabolise ethanol to produce acetic acid and ethyl acetate. The result is often a vinegar-like aroma in the wine.

Question 25

Lactic Acid Bacteria

Answer 25

A large group of bacteria. Some strains are more harmful to wine than others. Some strains includePediococcusspp.,Lactobacillusspp., andLactococcusspp. These organisms can cause a number of wine ailments including, but certainly not limited to, diacetyl production, excessive ethyl acetate levels, and more.

Question 26

Why do wine makers avoid using SO2 as a anti-microbial agent?

Answer 26

Too much can cause off aromas

Question 27

Pediococcusspp.,Lactobacillusspp., andLactococcusspp

Answer 27

Bad Lactic bacteria

Question 28

What can osmotic pressure do?

Answer 28

Cause yeast to produce more esters than normally. And not for the good.

Question 29

Why does calvados take 6m to ferment?

Answer 29

Apples picked late autumn so cold
Natural ferment
No climate control in fermenter
Winter hits slows or stops fermentation due to cold
Spring warms up and ferments all sugars before distill

Question 30

Clinitest

Answer 30

Clinitest method to assess the remaining amount of sugars. This method utilises tablets of copper sulphate, which react with reducing sugars to make a wine sample change colour. The resulting colour is then compared to a chart from which the approximate amount of residual sugar in the wine can be assessed

Question 31

How is MLF typically started? Why?

Answer 31

Can be natural but takes time
Wine makers usually add commercially cultured Oenococcus oeni bacteria and can time when to start MLF. Almost always after fermentation. Takes two weeks

Question 32

What grapes are used in Pisco?

Answer 32

muscat, italia, and torontel