Industrial Microbiology > Unit 3: Brewing > Flashcards

Unit 3: Brewing Flashcards

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1
Q

why is barley the most commonly used starch

A

-low temp for starch gelatinization
-high enzymes (amylase and amylopectin)
-low protein (good)
-robust husk
-genetically stable

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2
Q

Louis Pasteur’s contribution

A

laid foundation for brewing microbiology by establishing the role of yeast in alcoholic fermentations (aerobic and anaerobic metabolism)

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3
Q

Emile Hansen

A

developed pure yeast culture brewing

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4
Q

definition of beer

A

-carb source
-herbs and spices
-microbes- yeast and other organisms
-flavouring
-residual sugar

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5
Q

what is malt and its contribution

A

grain that has been germinated then dried

-source of carb and protein, enzymes (amylase and protease), and colour, flavour, and body

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6
Q

types of grain used

A

barley: most common
corn: adjunct flavour (DMS)
oats: complex carbs, smooth body
wheat: high protein
rice: dry profile
rye: flavour, lacks husk

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7
Q

role of barley kernel components

A

-embryo- baby plant
-starch endosperm- food reserve for embryo and source of fermentable sugars for brewing
-aleurone layer- generates the enzymes that degrade the starchy endosperm
-husk- protective layer

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8
Q

2 row vs 6 row of kernels

A

2 rows: lower yield, plumper/even kernels, higher extract, lower protein and enzymatic power

6 rows: higher yield, uneven kernels, lower extract, higher protein, higher enzymatic power

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9
Q

dimethyl sulphide (DMS)

A

derived from barley and can be derived from yeast itself

-adds a characteristic flavour in beers
-produced during grain germination

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10
Q

what is germination

A

-pre-germination soak hydrates grains for 5-6 days
-induction of enzymes (amylase-fermentable sugars and protease- amino acids)
because yeast cannot degrade the starch in barley

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11
Q

malting steps

A
  1. steeping
  2. germination
  3. kilning- dry germinated grains without denaturing enzymes
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12
Q

diastatic power (DP)

A

term to describe the ability of the malt to hydrolyze starches into fermentable sugars (measure of the enzyme’s power)
-measured in degrees Lintner
-DP= result of the alpha and beta amylase activity

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13
Q

what are hops and components

A

a flower with lupulin with bitter substances and aromatic oils

-alpha acids (90% of bitterness)
-beta acids
-oils

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14
Q

hops- production

A

pellets used (more stable than entire cones)
extracted with liquid, can be separated into hop resin and hop oil

amount of hops determines style of beer

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15
Q

adjuncts

A

source of carbohydrate

corn, rice, syrup

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16
Q

water’s role in beer

A

-is at least 90% of beer’s composition
-salts in water impact the enzymatic and chemical processes

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17
Q

considerations of water

A

water hardness
pH (must bring down from 7 to 5.1-5.6, need acidity for enzymes)
salts that impact flavour

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18
Q

malts as pH regulators

A

-dark malts and grains
-high in phosphate bound to phytic acid
-phosphate combines with Ca, forms insoluble salts, has a pH drop
-with Mg, it forms soluble salts, so less of a pH drop

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19
Q

gypsum as pH regulator

A

-CaSO4
-formation of calcium carbonate
-decrease buffering capacity: acidification of mash

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20
Q

issues of basic (alkali) pH

A

-inefficient or inhibited mashing process
-extracts phenolics and tannins from grains
-extracts harsh flavour notes from hops

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21
Q

minerals in water

A

sulphur, chloride, potassium, sodium

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22
Q

how is yeast selected

A

-normal to select yeast strains for brewing that are already in commercial use
-some breweries isolate, select, and maintain their own strains

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23
Q

yeast qualities

A

-rapid initiation of fermentation
-high fermentation efficiency
-high ethanol tolerance
-desired flavour characteristics
-high genetic stability
-range of alcohol production

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24
Q

ale yeast vs lager yeast

A

ale yeast: top fermenter, yeast rises to top of fermenter, cannot ferment melibiose (MEL)

lager yeast: bottom fermenter, yeast sinks to bottom

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25
yeast health (viability and vitality)
viability: measure of alive yeast and microscopic techniques vitality: measure of how healthy yeast is, acidification power (how metabolically active it is), oxygen consumption, sterol measurement
26
overview of the brewing process
milling mashing: stimulate enzymes to break down starch into fermentable sugars lautering: extraction of sugars boiling: pasteurization inactivates enzymes fermentation: remediation storage packaging
27
milling
-grain is processed through the roller mill -designed to leave the husk intact
28
mashing
-crushed grain is mixed with water in the mash tun -involves protein to simpler amino acids (proteinase and peptidase) -starch degradation to fermentable sugars (alpha and beta amylase)
29
mashing- stages of starch degradation
-gelatinization: formation of long chain aq starch -liquefaction: reduction of long starch chains to shorter molecules -saccharification: reduction to fermentable sugars
30
mashing- factors that affect it
-rise in temp controls amount of fermentable extract -time influences yield and fermentability -mash pH (optimum= 5.1-5.6) -mash water -mash thickness (thin is optimal)
31
lautering (wort separation)
separation of wort from the converted mash (wort= the liquid) -separation device= the lauter turn -mash is pumped to lauter turn, mash is pumped on the bottom, rakes help to level the grain bed and help filtration process -first separated wart is returned to the lauter turn until the clear wort is produced and transferred to the kettle
32
kettle (wort boiling)
functions: sterilization, protein precipitation, isomerization additions: hops, salts, syrups hot wort tank: whirlpool, protein precipitate (trub) spun into centre of tank, clear wort is sent to the wort cooler
33
wort cooling
wort cooler: reduces wort temp to initial fermentation temp (10 to 15 degrees) addition oxygen added for yeast fermenting
34
fermentation
dependent on 3 parameters -wort composition (nutrients, FAN, oxygenation level) -yeast (proper pitch rate, viability) -process conditions, temperature
35
fermentation- yeast pitching
in each fermentation, the cell density increases 3-4 fold, so 1/3-1/4 of the yeast crop of each fermentation is used for inoculation of the next batch 4 pitches then introduce fresh yeast prop end of fermentation: diacetyl rest -high fermentation temp: diacetyl formation -diacetyl rest: fermenter held at end temp to allow yeast to reduce the diacetyl (byproduct that gives buttery flavour)
36
what is plato?
plato= grams of extractable sugar per 100 mL wort at 20 degrees C 1 plato= 0.4% ethanol specific gravity= density solute/density water
37
yeast washing
improves yeast quality by reducing contaminating bacteria methods: sterile water wash, acid wash (most common)
38
storage
-temp lowered to 0 degrees -residual yeast and solids removed by centrifugation
39
packaging- filtration
-temp remains at 0 degrees -aged beer goes to filtration on the transfer to the Bright Beer Tanks -chillproofing agents added beforehand
40
packaging- diff processes
-pasteurization -sterile filtration -bottle filtration warehouse to customer
41
quality
sampling plans and specifications based on brewing requirements, customer expectations, and legislations
42
what are sampling plans and specifications based for
microbio sensory analytical packagin
43
brewing science: microbio
-metabolic pathways -diacetyl -esters, aldehydes -basic testing
44
diacetyl
produced by bacteria and is a yeast byproduct -butterscotch flavour -increase of primary fermentation temp + insufficient oxygen and FAN increases diacetyl -reabsorbed at end of fermentation (increase temp) decreases diacetyl
45
acetic acid production
derived from oxidation of ethanol -intermediate in acetate formation or incomplete ethanol fermentation caused by introduction of oxygen, or contamination by mutant yeast or acetic acid bacteria, fixed by yeast purity and avoiding oxygenation during bottling
46
esters
produced from their equivalent alcohol through catalysis by enzyme alcohol acetyl transferase and acetyl coenzyme A
47
labratory testing with microbiology
-pour plate, spread plate, mebrane filtration -media: universal beer agar, cycloheximide to inhibit yeast growth
48
brewing science: quality
49
brewing science: analytical
-laboratory testing (alcohol, colour, pH)
50
brewing science: packagin
51
brewing science: 5 steps of sanitation
1. dry-clean 2. pre-rinse 3. apply detergent 4. post-rinse 5. sanitize
52
brewing science: pros and cons of chlorine as a sanitizer
pros: cheap, broad range, easy to apply cons: pH dependent, corrosive
53
brewing science: pros and cons of chlorine dioxide as a sanitizer
pros: broad range, minimal formation of disinfection byproducts cons: expensive, degraded in high temps
54
brewing science: pros and cons of ozone as a sanitizer
55
brewing science: pros and cons of iodine compounds as a sanitizer
56
brewing science: pros and cons of QAS as a sanitizer
57
brewing science: pros and cons of peroxyacetic acid as a sanitizer
58
brewing science: pros and cons of anionic acids as a sanitizer
59
types of testing
validation: quantitative evidence of safety verification: observations and tests investigation
60
sanitation testing: rapid culture-free and culture based methods
rapid culture free: indirect measure of the presence of organic material and microbes, rapid, poor sensitivity and selectivity culture-based: direct microbial counts, swabs, selective, sensitive,
61
culture-free methods
-visual inspection -ATP tests -water testing -protein swabs
62
culture based methods
-environmental monitoring procedure- surface sampling (sponges and swabs) -rinse sampling -brewery testing
Industrial Microbiology
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