Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Food Microbiology > Beer, Wine, Cider > Flashcards

Beer, Wine, Cider Flashcards

(71 cards)

Start Studying
1
Q

What is the composition of beer?

A

Water, alcohol, CO2, various flavor compounds (carbs, proteins, minerals, aromatic compounds)

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

The process of beer production is known as: ___. The main microorganism involved is: ____.

A

brewing

yeast

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

How is density of the developing beer determined? Why is this important?

A

Density = ORIGINAL GRAVITY (specific gravity)
determine with hydrometer or refractometer

determine amount of dissolved sugars -> calculate final alcohol content, see how far fermentation has progressed

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

What is SG?

A

specific gravity: ratio of density in comparison to pure water

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

A wort with SG value of 1.050 is estimated to produce an alcohol content of ____

A

5%

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

What is an alternative measurement of density?

A

degrees Plato

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

What is ABV and how is it calculated?

A

alcohol by volume

(OG - TG) x 131.25

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

What is “TG?”

A

terminal gravity - gravity at end of ferment

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

True/False: a refractometer can determine the alcohol quantity based on its refractive properties

A

false; alcohol distorts readings.

refractometer works with sugar (based on refractive properties)

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

How do you use a hydrometer?

A

put instrument (weighted glass tube) in sample, allow to float -> take reading

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

True/False: the darker the beer, the more alcohol and bitterness

A

False; not related

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

____ is responsible for the bitterness in beer, which is measured in ____.

A

isomerized alpha acid

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

A high attenuation beer will be lower in _____. Why?

A

sugar

fermentation closer to completion

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

How is apparent attenuation calculated?

A

(OG-TG)/OG

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

What are the main steps of beer production? (6)

A
  1. Malting
  2. Milling
  3. Mashing
  4. Addition of Hops
  5. Fermentation
  6. Conditioning
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is achieved by the malting step in making beer?

A

Grains are soaked/drained repeatedly -> allowed to germinate
rootlets form
sugars stored in seed are released (made available)

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

What are the raw ingredients and microbes needed for beer?

A

Grain (barley), hops for flavor, water, yeast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does moisture content of grains change during malting?

A

grains start <20% moisture

soaking -> 42-46% moisture (start germinating)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why must there be drainage periods during malting?

A

allow for CO2 to be dispersed among grains -> promotes germination

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

What occurs during milling? What are the types of mills?

A

grains broken down for easier fermentation (consistent sizes)
wet/dry

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

What does the mashing step consist of? What does it produce?

A

add brewing water to malt -> produces WORT

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

When are hops added in beer production?

A

added to wort (boiled) before yeast addition

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

What are the varieties of hops used, and their purposes?

A 
aroma hops (smell)
alpha hops (taste)
dual purpose hops (both)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What form can hops come in? (4)

A

extract, pellets, fresh, dried

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What are the main sugars in wort? (6)
``` maltose dextrins maltotriose glucose fructose sucrose ```
26
What are the effects of adding too much vs too little yeast?
too little: slow ferment, other microbes may grow | too much: competition between yeast, poor growth
27
What are the effects of temperature on beer ferment?
``` too low (<5C): cold shock -> longer lag period, slower too high: could kill yeast ```
28
a normal lag phase is: ____
6-15 hrs
29
Why is it important to encourage yeast to start growing rapidly at the beginning of beer making?
quickly outcompete other microbes, prevent spoilage/pathogens
30
What conditions are necessary to make yeast produce ethanol? Why?
``` presence of sugar (need substrate) anaerobic conditions (less sugar uptake in aerobic conditions) ```
31
Even with unlimited hexoses and anaerobic conditions, why does yeast growth eventually stop? (3)
cannot perform cell wall synthesis in anaerobic conditions levels of ethanol become toxic cells floculate (clump) and sink
32
During what phase of growth is the most ethanol produced? How long is this period? What else is produced?
``` exponential phase (last 3-4 days) CO2, heat ```
33
Why is cooling needed during the exponential growth phase?
heat produced; if temp rises too much, other alcohols (propanol, isobutyl alcohol, etc) are produced -> off flavor
34
what is "green beer?"
beer that has just completed fermentation
35
What is conditioning?
chill to 9-11C, store in tanks for period of time
36
What are the 5 purposes of conditioning?
1. flavor maturation (allow yeast to PURGE/remove bad compounds) 2. clarification (let yeast cells settle, so can remove) 3. stabilization (add stabilizer to prevent chem rxn forming precipitates) 4. carbonation (add CO2 in headspace, dissolves in at low temp) 5. minimize oxygen (keep in anaerobic tanks, add antioxidants)
37
What compounds can be removed by purging with yeast?
H2S, acetaldehyde, diacetyl
38
Is there danger if bacterial spores are present in the final beer product?
Not likely; beer is low in nutrients so unlikely to germinate
39
True/False: pathogen contamination of beer is not a concern
true
40
Why is wort prone to spoilage?
nutrient rich, oxygenated
41
A low alcohol beer stored anaerobically has a strong rotten egg smell. What occurred?
contaminated with Megasphaera (anaerobic, grow at low ABV)
42
What microbe infects cask-conditioned beers? what does it cause?
zymomonas | cause "cider sickness" - secondary ferment -> frothing, less sweet, off odors
43
What microbe contaminates beer and produces propionic acid, other organic acids, and H sulfide?
pectinatus
44
What do LAB cause in beer?
spoilage: turbidity, acid, off flavor and odor
45
What microbes may contaminate exposed beer (aerobic)?
AAB
46
A beer stored without a lid is cloudy and has a slimy layer. what has occurred?
AAB contamination (converts ethanol to acetic acid)
47
What is the base ingredient for wine?
grapes | can use other fruit, but need to add water/sugar
48
Why are wines from certain years (vintages) considered higher quality?
climate affects grape crop quality -> affect final wine composition
49
What are the 2 main sugars present in grape must?
glucose, fructose
50
How does the process for red wine differ from white wine?
maceration and partial ferment (to extract tannins, color) before skins are removed
51
What are the 3 phases of wine fermentation, and their durations?
1. lag phase (few hours) 2. growth phase (24-36 hours) 3. stationary phase (long period)
52
True/False: in the stationary phase, yeast activity stops
False; activity slows, but remains active until 90% sugars depleted
53
What is the purpose of CO2 as a substrate in wine?
used to make metabolites/aroma compounds
54
What is different about the process of making Chardonnay wine?
secondary ferment step to develop taste | MALOLACTIC FERMENTATION
55
What organisms are used for malolactic fermentation? What process occurs?
``` Oenococcus onesie (some other LAB can also do it) convert L-MALIC ACID -> L-LACTIC ACID + CO2 ```
56
What organisms are initially present on grapes? Why must they be removed?
wild yeasts | remove so S. cerevisiae can dominate, prevent spoilage
57
What is important to prevent spoilage in winemaking?
1. sulfiting (kill wild yeast) 2. anaerobic conditions (prevent spoilage aerobes) 3. grow yeast quickly to exhaust sugars
58
True/false: the sulfiting process removes all yeast except S. cerevisiae
False; certain other species also resistant, will survive and participate in ferment
59
What is "sulfiting?"
addition of sulfur dioxide as an antimicrobial (or antioxidant)
60
What property makes sulfur dioxide lethal to most microbes? (2)
sulfur dioxide bound to water will easily enter cell -> pH driven dissociation -> bisulfite, sulfite (affect gradient) react with cell molecules: rupture disulfide bridges, react with cofactors, deaminate cytosine (fatal mutations)
61
What mutation (unique to wine yeast) gives it sulfite resistance?
chromosomal mutation | SSU1-R1 and SSU1-R2 (sulfite efflux pumps) expressed at high levels
62
How do SSU1-R1 and SSU1-R2 differ?
SSU1-R2 has increased expression in first few hours of wine ferment
63
What do campden tablets consist of? What are they used for? (3)
Na metabisulfute | Sterilize, remove free Cl, act as antioxidant
64
What is used to stabilize wine by halting yeast? When is it added?
K sorbate | add at end
65
What should you do if you somehow add ALL your campden tablets in?
THROW THAT SHIT OUT MF
66
What is a "stuck fermentation?" | What are some possible causes? (6)
fermentation stops prematurely ``` nutrient deficiency inhibitory substances (acid, too much sulfur dioxide) killer toxins (from competing yeasts) low pH (<3) pesticides temperature ```
67
True/False: LAB growth in wine should always be avoided
False | usually considered spoilage, but LAB can also be used for malolactic ferment in some wine types
68
What is the notable compound produced by LAB in wine? What is the resulting profile?
diacetyl small amount -> nutty aroma (good) higher amount -> spoilage
69
What has occurred if your wine tastes more acidic than alcoholic?
spoilage caused by AAB
70
How is balsamic vinegar of modena produced? (4)
cook grape must yeast convert sugar -> ethanol oxidize to acetic acid by AAB 12 yrs aging (becomes concentrated and complex)
71
What can beer, cider, and wine be further fermented into?
vinegar (with AAB) | malt, cider, and wine vinegars

Food Microbiology (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions