Fermentation

Question 1

Chemical symbol of yeast taking up simple sugars and converting them to alcohol and CO2

Answer 1

C6H12O6 (glucose) –> 2C2H5OH (ethanol) + 2CO2 (carbon dioxide)

Question 2

Glycolysis

Answer 2

Pathway used to break down glucose and simple sugars
-Generates energy that can be stored and used in other reactions eg. building new cell material
-Yeast makes 2 molecules of ATP for each molecule of glucose used

Question 3

Adenosine triphospate

Answer 3

“Main currency”
-Glycolysis breaking down sugars is mainly oxidations, which release energy
-Cells retain some of this energy as ATP

Question 4

Present gravity to °P

Answer 4

Divide by 4. eg PG 40 = 10° P

Question 5

Degrees Plato to present gravity

Answer 5

Multiply by 4. eg 10° P = PG 40

Question 6

Saccharometer

Answer 6

A hydrometer calibrated for the range of densities used in brewing; a weighted glass bulb with a scale

Question 7

Fermentation: Lag phase

Answer 7

Fermentation is started by adding yeast, which takes some time to adapt to the new environment of warm oxygenated wort. O2 is taken up early on to make lipids and sterols, which are shared with daughter cells. Eventually O2 is depleted and lipids drop off; growth stops.

Question 8

Fermentation: Log phase

Answer 8

“Exponential phase”, most changes occur.
-Yeast grows the fastest, max sugar uptake, max alcohol & CO2 formation.
-Greatest drop in pH

Question 9

Fermentation: Deceleration phase

Answer 9

-Limit of yeast growth
-When substances essential for yeast growth run out

Question 10

Fermentation: Stationary phase

Answer 10

Decrease in gravity stops
-All fermentable sugars used up
-Yeast stops growing and begins to flocculate

Question 11

Fermentation: End gravity

Answer 11

Attenuation gravity.
-Residual gravity is mainly the dextrins that brewing yeast cannot use

Question 12

Wort composition

Answer 12

Influences total yeast growth & beer flavor
-Oxygen solubility decreases with increase in wort concentration

Question 13

Temperature

Answer 13

Faster fermentation at higher temps
-No effect on total yeast growth, just rate

Question 14

Pitching rate

Answer 14

At low/medium values, increase in pitching rate increases fermentation rate

Question 15

Wort oxygenation

Answer 15

Increases fermentation rate and yeast growth
-Very high pitching reduces total yeast growth, as there is less O2 per cell

Question 16

Haemocytometer

Answer 16

The slide with the engraved grid for easier counting under a microscope