Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

5) Food Microbiology > 6) Beer, Wine and Cider > Flashcards

6) Beer, Wine and Cider Flashcards

You may prefer our related Brainscape-certified flashcards:
Gourmet Food flashcards Biology 101 flashcards
1
Q

define brewing

A

process of preparing beverages from infusion of grains that have undergone sprouting and fermentation of the sugary solution produced by yeast, where a proportion of the CHO is converted to ethanol and CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

define gravity

A

density of the wort or a way of calculating amount of dissolved substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how is gravity expressed?

A
  • degrees Plato
  • original gravity (OG)
  • starting gravity (SG)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how is original gravity expressed?

A

as a ratio of density relative to pure water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how is OG related to the final alcohol content?

A

the significant digit of OG is an estimation of the final alcohol content

eg. 1.040 wort = 1.040 times as dense as pure water = 4.0% Alcohol By Volume (ABV)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does ABV stand for? what is it?

A

ABV = alcohol by volume = percent of ethanol in finished beer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how is gravity measured?

A

by hydrometer (weight glass tube with scale which stops at relative density of liquid being measured) or refractometer (Based on refractive properties of sugar. Alcohol distorts readings)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe terminal gravity. What can it be used for?

A

how much gravity is left after the fermentation is finished. Can be used to calculate the alcohol content of the finished beer/wine/cider

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the ABV equation?

A

ABV = (OG - T) * 131.25

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is color measured by in beer?

A

lightness/darkness is measured by spectrophotometer

color is assessed by Tristimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how is bitterness in beer measured?

A
  • in bitterness units (BU) which relates to ppm isomerized alpha acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is attenuation?

A

way of measuring how complete a fermentation process is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the eqn of apparent attenuation?

A

apparent attenuation = (OG - TG) / OG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how can attenuation of a beer be altered?

A

by sugar type, mashing method, composition of the wort or type of yeast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

high apparent attenuation represents what?

A

a dry beer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

low apparent attenuation represents what?

A

a sweet beer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is malting?

what is the goal of it?

A
  • the process of allowing the grain to germinate (usually by soaking in water)
  • the goal is to transform food reserves in the grain into substrates that are convenient for masking in the brewery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

describe the malting process

A
  1. before start, moisture content of the grains should not be higher than 20%
  2. to start, grains are soaked in water to increase to 42-46% moisture for germination
  3. drainage periods where air is blown through (so that water is not left on grains). This also disperses CO2 to promote germination. As air is blown through germinating grain beds, grains are turned slowly in drums or by automated turning arms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is milling?

A

process that breaks down the malt into smaller fermentable sizes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are 2 types of milling?

A

wet and dry milling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is mashing?

what is the result of mashing?

A

process where ground malt is mixed with brewing water, so that fermentable extract is produce to support growth of yeast

results in wort

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are 3 varieties of hops according to function in brewing?

A

aroma
alpha
dual purpose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how are hops used in brewing?

A
  • hops are boiled with the wort

- afterwards, yeast is added

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what sensory properties does hops add?

A

bitterness, but also floral, fruity or citrusy aromas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what happens when too much or too little Sc is added to the wort?

A

Adding too little = very slow initial fermentation

Adding too much = competition between yeast and poor growth

26
Q

why is temperature imp when adding yeast?

A

if wort is more than 5C cooler than yeast, it results in cold shock which causes prolonged LAB period

27
Q

in industrial fermentations, why must microbes start growing as fast as possible?

A

so growth of other MO is discouraged

28
Q

what is the composition of wort?

A 
maltose (50-60%)
dextrins
maltotrios
glucose
fructose (2%)
sucrose (2%)
29
Q

describe the O2 req needed for yeast growth

A

can grow anaerobically or aerobically

30
Q

in anaerobic conditions, yeast produes what?

A

alcohol

31
Q

how does O2 presence affect sugar up take of yeast?

A

decreases

32
Q

why do yeast fermentations not keep going, even if anaerobic conditions and sugars are present?

A

b/c budding requires cell wall synthesis, which can’t occur in anaerobic conditions. Eventually, growth must cease

Also, the level of ethanol will eventually become toxic to yeast, which slows the yeast growth

33
Q

describe the exponential growth phase

A
  • when yeast density increases 4-6x
  • highest level of utilizing sugars and producing ethanol + CO2
  • high heat production. Requires cooling down to keep temp lower.
  • lasts around 48-60 hrs
  • after this phase, growth slows
34
Q

what happens during exponential growth phase when temp is too high?

A

higher alcohols (pronaol, isoayl alcohol or isobutyl alcohol) will be produced which imparts off flavours

35
Q

what happens to beer post-fermentation?

what is it called at this stage?

A
  • once beer has been fermented down to its final desired gravity, it is chilled
  • called “green beer”
  • must be conditioned before packaging
36
Q

what are 5 considerations during conditioning of beer after fermentation?

A
  1. flavour maturation: yeast removes undesirable compounds by the purging process (eg. H2S, acetaldehyde, diacetyl).
  2. clarification: allows beer to settle so that yeast can be removed by sedimentation
  3. stabilization: to prevent a non-biological precipitate to form during storage, stabilizers are added to remove precursors of precipitates
  4. carbonation: CO2 is more soluble at reduced temp, so a top pressure of CO2 is maintained in conditioning tanks
  5. minimize O2: O2 is low in green beer. If O2 comes back in, antioxidants are added
37
Q

wort and beer are both prone to _____

A

spoilage organisms

38
Q

why is wort especially prone to spoilage?

A

since it provides a nutrient and O2 rich environment

39
Q

how can you prevent spoilage of wort and beer?

A

use process control to prevent contamination

40
Q

why is beer not a good growth media for bacteria?

A

since it has low pH and nutrients

41
Q

how does turbidity and ropiness quality occur in beer?

A
  • aerobic beer spoilers (primary AAB) results in oxidation of ethanol to acetic acid
  • causes raft of surface growth in beer
42
Q

what gives beer a rotten egg smell?

A

pectinatus and megasphaera

43
Q

what causes “cider sickness”? how?

A

Zymomonas

  • causes secondary fermentation with frothing, loss of sweetness and off odors due to H2S and acetaldehyde production
44
Q

vintage vs non-vintage wines?

A

vintages: superior, can’t be blended with other wines

non-vintage: blended to have acceptable products even in bad years

45
Q

what are 3 main phases of wine fermentation?

A
  1. lag phase: few hours long
  2. growth phase: 24-36 hours
  3. stationary phase: longest phase where most sugars are converted to alcohol. Yeast activity decreases although viability is around 90% until sugar is depleted
46
Q

what is the desirable outcome of wine fermentation?

A

complete degradation of sugars to ethanol + CO2 to provide metabolites and aroma cmpds

47
Q

what is malolactic fermentation?

A
  • imp in taste and development of wine
  • carried out by LAB or Oenococcus onesie
  • L-malic acid –> L-lactic acid + CO2
48
Q

what conditions are required for Sc to dominate the fermentation by removing other yeasts?

A
  1. sulfating
  2. anaerobic conditions (since many spoilage organisms need oO2)
  3. rapid and complete exhaustion of sugars
49
Q

what is the main use of sulfur dioxide in wine?

what are other uses?

A

to kill natural yeast species to allow wine specific Sc (which are resistant to sulfur dioxide) to dominate the fermentation

other: anti-oxidative and anti-microbial properties

50
Q

describe the chemical rxn of sulfur dioxide in wine

A
  1. SD is dissolved in H2O and enters the cell
  2. SO2.H2O undergoes rapid pH driven dissociation to bisulfite and sulfite
  3. SO2 inhibits growth of microbes which ruptures disulfide bridges in proteins, then reacts with cofactors
  4. deaminates cytosine to uracil which increases possibility of fatal mutations
51
Q

what is SSU1-R1?

A
  • dominant allele of the sulfite pump

- expressd at higher levels than SSU1

52
Q

what is the function of Campden tablets?

A
  • to sterilize wine, cider and beer by amateur brewers since it allows easy measurement of small quantities of sodium metabisulfite. Tablets are not used in the industry since they would measure out specific amounts of Na metabisulfite
  • eliminates free chlorine from water solutions (ie. when using water from a municipal source)
  • antioxidizing agent when transferring wine between containers (since the sodium metabisulfite traps the O2 entering the wine)
53
Q

what is potassium sorbate used for?

A

to halt the yeast and preserve the wine

54
Q

what is a stuck fermentation?

A

premature cessation of alcohol production in the fermentation

55
Q

what is a stuck fermentation caused by?

A
    1. nutrition deficiency (N, vitamins, minerals)
    1. inhibitory substances (Acetic acid, lactic acid, excessive sulfur dioxide)
    1. killer toxins (produced by yeasts against other yeasts)
    1. pH too low (less than 3)
    1. pesticides remaining on grapes
    1. temperature (too low at beginning or too high during ferment)
56
Q

what is an odor compounds produced by LAB in wine? when is the production of this compound positive or negative?

A

diacetyl

positive: “butter” aroma at low conc
neg: “nutty” aroma at high conc

57
Q

what is cider particularly prone to? how can you avoid this?

A

contamination with AAB

avoid by adding sulfur dioxide at initial fermentation step

58
Q

describe production of malt vinegar

A
  1. malting barley: starch is converted to maltose
  2. maltose converts to ale
  3. ale turns to vinegar
  4. vinegar is aged
59
Q

describe production of cider vinegar

A

apple juice is double fermented with alcohol and acetic acid fermentation by yeasts and AAB

60
Q

describe the production of traditional balsamic vinegar

A
  • sugars are converted to ethanol by yeast
  • oxidation of acetic acid by AAB
  • at least 12 years of aging
61
Q

describe the production of rice vinegar

A
  • made from fermented rice wine (sake)
  • produced via static surface fermentation
  • AAB
62
Q

what are 3 times of rice wine vinegar?

A
  1. Komesu: produced from polished rice grains; pale amber color; used for sushi and seaweed salad
  2. Kurosu: produced from unpolished rice grains; dar black color; used as a table condiment or healthy drink
  3. Kasuzu: produced from sake lees; 210 different AAB isolated from a traditional fermentation

5) Food Microbiology (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions