6) Beer, Wine and Cider

Question 1

define brewing

Answer 1

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

Question 2

define gravity

Answer 2

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

Question 3

how is gravity expressed?

Answer 3

• degrees Plato
• original gravity (OG)
• starting gravity (SG)

Question 4

how is original gravity expressed?

Answer 4

as a ratio of density relative to pure water

Question 5

how is OG related to the final alcohol content?

Answer 5

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)

Question 6

what does ABV stand for? what is it?

Answer 6

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

Question 7

how is gravity measured?

Answer 7

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)

Question 8

describe terminal gravity. What can it be used for?

Answer 8

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

Question 9

what is the ABV equation?

Answer 9

ABV = (OG - T) * 131.25

Question 10

what is color measured by in beer?

Answer 10

lightness/darkness is measured by spectrophotometer

color is assessed by Tristimulus

Question 11

how is bitterness in beer measured?

Answer 11

• in bitterness units (BU) which relates to ppm isomerized alpha acid

Question 12

what is attenuation?

Answer 12

way of measuring how complete a fermentation process is

Question 13

what is the eqn of apparent attenuation?

Answer 13

apparent attenuation = (OG - TG) / OG

Question 14

how can attenuation of a beer be altered?

Answer 14

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

Question 15

high apparent attenuation represents what?

Answer 15

a dry beer

Question 16

low apparent attenuation represents what?

Answer 16

a sweet beer

Question 17

what is malting?

what is the goal of it?

Answer 17

• 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

Question 18

describe the malting process

Answer 18

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

Question 19

what is milling?

Answer 19

process that breaks down the malt into smaller fermentable sizes

Question 20

what are 2 types of milling?

Answer 20

wet and dry milling

Question 21

what is mashing?

what is the result of mashing?

Answer 21

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

results in wort

Question 22

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

Answer 22

aroma
alpha
dual purpose

Question 23

how are hops used in brewing?

Answer 23

• hops are boiled with the wort

- afterwards, yeast is added

Question 24

what sensory properties does hops add?

Answer 24

bitterness, but also floral, fruity or citrusy aromas

Question 25

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

Answer 25

Adding too little = very slow initial fermentation Adding too much = competition between yeast and poor growth

Question 26

why is temperature imp when adding yeast?

Answer 26

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

Question 27

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

Answer 27

so growth of other MO is discouraged

Question 28

what is the composition of wort?

Answer 28

``` maltose (50-60%) dextrins maltotrios glucose fructose (2%) sucrose (2%) ```

Question 29

describe the O2 req needed for yeast growth

Answer 29

can grow anaerobically or aerobically

Question 30

in anaerobic conditions, yeast produes what?

Answer 30

alcohol

Question 31

how does O2 presence affect sugar up take of yeast?

Answer 31

decreases

Question 32

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

Answer 32

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

Question 33

describe the exponential growth phase

Answer 33

- 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

Question 34

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

Answer 34

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

Question 35

what happens to beer post-fermentation? what is it called at this stage?

Answer 35

- once beer has been fermented down to its final desired gravity, it is chilled - called "green beer" - must be conditioned before packaging

Question 36

what are 5 considerations during conditioning of beer after fermentation?

Answer 36

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

Question 37

wort and beer are both prone to _____

Answer 37

spoilage organisms

Question 38

why is wort especially prone to spoilage?

Answer 38

since it provides a nutrient and O2 rich environment

Question 39

how can you prevent spoilage of wort and beer?

Answer 39

use process control to prevent contamination

Question 40

why is beer not a good growth media for bacteria?

Answer 40

since it has low pH and nutrients

Question 41

how does turbidity and ropiness quality occur in beer?

Answer 41

- aerobic beer spoilers (primary AAB) results in oxidation of ethanol to acetic acid - causes raft of surface growth in beer

Question 42

what gives beer a rotten egg smell?

Answer 42

pectinatus and megasphaera

Question 43

what causes "cider sickness"? how?

Answer 43

Zymomonas - causes secondary fermentation with frothing, loss of sweetness and off odors due to H2S and acetaldehyde production

Question 44

vintage vs non-vintage wines?

Answer 44

vintages: superior, can't be blended with other wines non-vintage: blended to have acceptable products even in bad years

Question 45

what are 3 main phases of wine fermentation?

Answer 45

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

Question 46

what is the desirable outcome of wine fermentation?

Answer 46

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

Question 47

what is malolactic fermentation?

Answer 47

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

Question 48

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

Answer 48

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

Question 49

what is the main use of sulfur dioxide in wine? what are other uses?

Answer 49

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

Question 50

describe the chemical rxn of sulfur dioxide in wine

Answer 50

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

Question 51

what is SSU1-R1?

Answer 51

- dominant allele of the sulfite pump | - expressd at higher levels than SSU1

Question 52

what is the function of Campden tablets?

Answer 52

- 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)

Question 53

what is potassium sorbate used for?

Answer 53

to halt the yeast and preserve the wine

Question 54

what is a stuck fermentation?

Answer 54

premature cessation of alcohol production in the fermentation

Question 55

what is a stuck fermentation caused by?

Answer 55

- 1. nutrition deficiency (N, vitamins, minerals) - 2. inhibitory substances (Acetic acid, lactic acid, excessive sulfur dioxide) - 3. killer toxins (produced by yeasts against other yeasts) - 4. pH too low (less than 3) - 5. pesticides remaining on grapes - 6. temperature (too low at beginning or too high during ferment)

Question 56

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

Answer 56

diacetyl positive: "butter" aroma at low conc neg: "nutty" aroma at high conc

Question 57

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

Answer 57

contamination with AAB avoid by adding sulfur dioxide at initial fermentation step

Question 58

describe production of malt vinegar

Answer 58

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

Question 59

describe production of cider vinegar

Answer 59

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

Question 60

describe the production of traditional balsamic vinegar

Answer 60

- sugars are converted to ethanol by yeast - oxidation of acetic acid by AAB - at least 12 years of aging

Question 61

describe the production of rice vinegar

Answer 61

- made from fermented rice wine (sake) - produced via static surface fermentation - AAB

Question 62

what are 3 times of rice wine vinegar?

Answer 62

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