QUIZ 2

Question 1

What is MLF?

Answer 1

Secondary fermentation “Malo-Lactic Fermentation” where Malic acid is converted to Lactic Acid by Lactic Acid BACTERIA (LAB)

Question 2

Is Malic Acid Less Acidic Than Lactic?

Answer 2

Lactic Acid is less acidic than malic acid (higher pKa) and only has 1 H+ available​

Question 3

How much Malic Acid is removed during the MLF?

Answer 3

1-3g/L of Malic Acid is REmoved generally

Question 4

How does an Enzyme Kit work?

Answer 4

Enzyme kit uses 2 enzymes to convert L-malic acid​

NADH is produced, which can be measured at 340nm​

Question 5

What gases are dissolved in wine?

Answer 5

N2, O2 and CO2 can be dissolved in wine

Question 6

What effect does Oxygen have on juice/must and wine??​

Answer 6

Oxygen is important for yeast pre-ferment & during ferment​:

-Yeast synthesis sterols and unsaturated fatty acids that protect their cell membrane integrity (alcohol weakens membrane)​

Oxygen causes oxidation​:

-Promotes tannin polymerization​
-Causes aging and browning of wine colour

Question 7

How can you remove dissolved Oxygen from wine?​

Answer 7

Use inert gases (N2 or CO2 or Argon) to sparge wine and push out oxygen​

Sparge inline during wine movements​

Sparge tank ​

Question 8

How does temperature affect the concentration of dissolved gases?​

Answer 8

Lower temperatures increase the solubility of O2 and CO2 in liquid

Question 9

How much oxygen is introduced at various stages of winemaking?​

Answer 9

Oxygen Intake during Winemaking​:

Topping Up: 0-1mg/L O2
Filter: 0-2mg/L O2
Pumping: 1-2mg/L O2
Centifuging: 0-2/3
Bottling: 0-4
Temp Reduction: 3-6mg/L
Racking w Aeration: 4-8mg/L

Question 10

How can you manage the amount of Oxygen introduced during wine movements?​

Answer 10

Use inert gases (N2 or CO2) to flush the spaces that could have air ​

Question 11

How can you remove dissolved Oxygen from wine?​

Answer 11

Use inert gases (N2 or CO2 or Argon) to sparge wine and push out oxygen​:

-Sparge inline during wine movements​
-Sparge tank

Question 12

How does Sparging work??​

Answer 12

a process used to remove unwanted gases, such as carbon dioxide (CO2), from the wine or to introduce a specific gas into the wine.

Question 14

How can you measure dissolved Oxygen in wine?

Answer 14

DO electrode (compatible with our pH meters)​
-Electrochemical​

​

Optical sensors​
-Obisphere

Question 15

When is it most important to check wine DO?​

Answer 15

Prior to bottling (want low DO!! ie <0.5mg/L or <0.3mg/L)​

-During bottling (first and last bottles off the line)​

Question 16

Where could the wine pickup more DO after bottling tank?​ (dissolved oxygen)

Answer 16

Any place where wine is exposed to oxygen​
-Transfer lines/pump​
-Filler head​
-Bottles​

Question 17

Is it possible to have too much Carbon Dioxide in wine?​

Answer 17

YES, desired CO2 level varies greatly with wine style​

-Minimal CO2 desired in full-bodies reds (ie <0.5g/L)​

-Aromatic whites higher CO2 level desired (0.8-1.3g/L)​

High sugar Riesling may want even higher level of CO2 (up to 1.8-2.0g/L CO2)​

CO2 level at bottling is a winemaker’s preference, usually verified by tasting​

Question 18

When would the CO2 level be highest in wine?

Answer 18

Immediately after fermentation​

Will decrease as wine ages and with wine movements​

Question 19

How can you measure dissolved Carbon Dioxide in wine?​

Answer 19

Manual Veitshoechheim CO2 cylinder​
–Not very accurate – user dependent​

Optical sensors​
-Obisphere​

​

Question 20

shift in red wine colour from:​

Answer 20

violet-red
deep-red (520nm)
brick-red
brown (420nm)

Question 21

Colour-aeration trend: (red wine colour intensity)

Answer 21

wine becomes oxidized​

colour pigments polymerize with other flavonoids​

higher fraction of pigments in coloured form​

more stable against pH changes​

colour intensity is enhanced​

aerated red wine will have a more intense colour​

anthocyanin-tannin condensation stabilizes colour

Question 22

Wine/juice with sugar will have a _________ of SO2?

Answer 22

Wine/juice with sugar will have a high proportion of SO2​

Question 23

Dirty juice/must will consume SO2 meaning ________?

Answer 23

You will need to add extra SO2

Question 24

Total SO2 = ?

Answer 24

Total SO2 (TSO2) = Free SO2 (FSO2) + Bound SO2​

Question 25

Why is Molecular SO2 important in winemaking?

Answer 25

Most important form in winemaking​ Provides anti-microbial protection​ A strongest antioxidant in this form reacts with H2O2 and aldehydes​

Question 26

Sulfite (SO32-) is the least abundant at __________pH?

Answer 26

Sulfite (SO32-) is the least abundant at wine pH

Question 27

Total SO2 can be measured in 2 ways:​

Answer 27

Measure FSO2 first, then heat sample to determine the bound (add together for total)​ Measure FSO2 on a sample, then use a FRESH sample to determine the TSO2 while heating

Question 28

There are 3 different genera of bacteria that can produce lactic acid​

Answer 28

Leuconostoc: Pediococcus: ​ Lactobacillus:

Question 29

Lactobacillus:

Answer 29

Commonly associated with fermentation to produce yogurt and sauerkraut (full sour dill pickles )​ Can use both homofermentative and heterofermentative pathways

Question 30

Pediococcus:

Answer 30

Generally considered a spoilage organism that can produce biogenic amines (ie. Putrescine, cadaverine) ​ Glucose fermented into 2 moles lactic acid and 2 moles of ATP (Homofermentative)

Question 31

Leuconostoc:

Answer 31

Leuconostoc oenos (ie. Oenococcus oeni) are the most important strains for winemaking​ Glucose (& malic acid) fermented into lactic acid, ethanol, acetic acid, CO2 and 1 mole of ATP (Heterofermtative)​

Question 32

Lactic acid bacteria can only convert _______?

Answer 32

Lactic acid bacteria can only convert the L form of malic acid​ If you add malic acid to your wine, only the L-malic acid will be consumed​

Question 33

6 Factors that affect MLF?

Answer 33

Temperature​ Optimal temperature 18-24 °C (below 15 °C LAB will not grow)​ ​ pH​ Some strains of L. oenos can grow at pH 3-3.3​ Lactobacillus and Pediococcus cannot grow below pH 3.3 (ideal above 3.6)​ ​ Alcohol​ Optimal below 13% alcohol​ Difficult to complete MLF if alcohol is above 16%​ SO2​ LAB very sensitive to SO2​ Ideally FSO2 below 10ppm and TSO2 below 60ppm​ ​ Nutrients available​ Post fermentation, there may not be sufficient vitamins and amino acid for LAB​ Nutrients available from commercial suppliers​ ​ Toxins/inhibitors​ Fatty acids and fumaric acid inhibits LAB​ ​

Question 34

Taste/Flavour Changes due to MLF

Answer 34

Lower acidity​ Positive flavour​ Diacetyl (buttery tones positive to a threshold)​ ​ Negative flavour​ Excessive diacetyl, acetic acid (VA) production, sauerkraut, acrolein (bitter), mousiness, geranium tone

Question 35

How to prevent MLF?

Answer 35

SO2​ ​ Low temperature (below 15 °C)​ ​ Rack and/or fine wine to reduce nutrient content​ ​ Keep pH low​ ​ Sterile filter wine

Question 36

How to measure MLF in Lab?

Answer 36

Paper Chromatography to qualitatively assess