first midterm

Question 1

three categories of haze

Answer 1

• Microbiological stability - yeast and possibly
other microbes
• Colloidal stability - haze particles (proteins and
polyphenols)
• Flavour stability - change in beer flavour
(minimize oxidation)

Question 2

beer stabilization can

Answer 2

• Enhance beer clarity (more pleasing appearance)
• Enhance drinkability (adjust the mouthfeel and
flavour)
• Extend the shelf life

Question 3

Beer freshness

Answer 3

• Beer freshness starts to deteriorate right after

packaging

Question 4

• Beer stabilization process will depend on

Answer 4

• Beer style

* Brewery size

Question 5

size of brewers yeast

Answer 5

5-10 um

Question 6

size of wild yeast

Answer 6

3-10 um

Question 7

lactobacillus spp

Answer 7

0.5 - 1.0 um

Question 8

Pediococcus spp

Answer 8

0.5 - 1.0 um

Question 9

spores of micro-organisms

Answer 9

<0.5 um

Question 10

Three main changes in beer caused by the presence

of proteins and polyphenols:

Answer 10

• Increase in beer haze (colloidal instability)
• Increase in harsh taste (flavour stability)
• Increase in beer colour (following oxidation)

Question 11

Both substances are derived from

Answer 11

malt

Question 12

Oxidized polyphenols and polypeptides become

linked by

Answer 12

hydrogen bonding

Question 13

Chill haze is a

Answer 13

reversible association

Question 14

Permanent haze is characterized b

Answer 14

more durable

covalent bonding

Question 15

chill haze vs permanent haze temperatures

Answer 15

chill form at 0 ˚C and redissovle at 20 ˚C

permanent form at 0 ˚C and does not redissovle

Question 16

stability categories in the main reason for a limited beer shelf life

Answer 16

flavour stability

Question 17

loose bonding is

Answer 17

non visible haze

Question 18

terms associated with lagering

Answer 18

-Secondary Fermentation
• Maturation
• Stabilization

Question 19

Maturation

Answer 19

Maturation - includes diacetyl removal and
excretion (by yeast) of flavour positive compounds
(fullness)

Question 20

Stabilization

Answer 20

Stabilization – removal of haze forming materials

Question 21

Includes treatment with yeast and protein/tannin
removal agents (finings, silica gel, PVPP, etc.)

Answer 21

Stabilization

Question 22

gravity sedimentation, fining/clarifying agents, centrifuge

Answer 22

clarification

Question 23

diatomaceous earth, sheet, membrane, crossflow

Answer 23

filtration

Question 24

is the act of removing suspended particles
from beer (yeast, bacteria, permanent and chill
haze)

Answer 24

filtration

Question 25

n refers to the treatment of beer by absorbent materials to remove precursors of haze (use of PVPP, silica gel)

Answer 25

stabilization

Question 26

s stored at temperatures 0 to - 5°C • Vast majority of yeast and haze particles will settle to the bottom of the tank (low temp. and counterpressure) • This can achieve 10-fold turbidity reduction

Answer 26

gravity sedimentation

Question 27

draw back to gravity sedimentation

Answer 27

sludge at the bottom can be self insulating autolyzed yeast flavour sludge contains beer

Question 28

* Isinglass fining * Auxiliary finings * Bentonite * Tannic acid

Answer 28

group of additives for beer clarification- fining agents

Question 29

are mostly designed for yeast removal (they | do much less for chill stability)

Answer 29

Fining

Question 30

Active ingredient is protein known as collagen | • Positively charged at beer pH

Answer 30

Isinglass fining

Question 31

acidified silicates and acidic polysaccharides • Negative charge at beer pH

Answer 31

Auxiliary finings

Question 32

• Clay-like mineral - consists of insoluble aluminasilicates • Swells when mixed with beer - the large surface area adsorbs beer proteins

Answer 32

Bentonite

Question 33

* Precipitant - removes excess protein | * is a polyphenol extracted from gall nuts

Answer 33

Tannic acid

Question 34

Not strictly clarifying agents (stabilizing agents) • Used to improve colloidal stability of beer • Designed to improve beer shelf life and nonbiological stability • They include:

Answer 34

* Papain * Silica gel * PVPP

Question 35

artificial polymer that has a similar structure to proteins (also adsorbent) • React with the tannins in beer - reduce one of the haze forming pathways • Loose hydrogen-bonding between the polymer and the polyphenols

Answer 35

• PVPP (polyvinyl-pyrollidone)

Question 36

Yeast cells carry a _ surface charge.

Answer 36

negative