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FOSC202 > Malting/germination process > Flashcards

Malting/germination process Flashcards

1
Q

three main components to barley structure

A

husk
endosperm
aleruone layer

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2
Q

role of the husk

A

protect seed and growing embryo

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3
Q

why is the husk useful in brewing

A

it acts as a filter during wort separation

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4
Q

role of the endosperm

A

bulk nutrients
-starch granules
-the source of fermentable sugars and amino acids

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5
Q

role of the aleurone layer

A

-source of enzymes
-triggered by hormones produced by the growing embryo

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6
Q

steps of malting

A

steeping: raise moisture content to trigger germination
Germination: controlled sprouting in grian beds with forced air
kiling: reduces moisture content and dries malt

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7
Q

what happens if steeping is either too short or too long

A

too short: poor consistency
too long: mould and bacteria grow

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8
Q

purpose of germination

A

control sprouting
release hydrolytic enzymes
modification of endosperm structure

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9
Q

describe the steeping regime

A

-first immersion 6-16 hrs 32% water content
-air rest 12-24: expose embryo to O2 and removes CO2
-second immersion 10-20 hrs

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10
Q

describe what is happening to the barley grain during steeping

A

-water enters through the microphyle and distributes through the starchy endosperm
-water activates the embryo which then produces gibberellic acid that migrates to the aleurone
-enzyme production is stimulated to breakdown the endosperm

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11
Q

3 examples of diastatic enzymes

A

alpha glucosidase
alpha amylase
beta amylase

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12
Q

which enzymes are most important

A

amylase

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13
Q

how does starch exist in the endosperm

A

as large or small grnaules

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14
Q

what is the difference in gelatinisation of large and small starch granules

A

small granules require a higher temperature

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15
Q

what is gelatinisation temperature important

A

reaching the right temp is important during mashing for the conversion to fermentable sugars

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16
Q

describe amylose shape

A

linear chains
alpha 1,4 linkages

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17
Q

describe amylopectin shap

A

short chains
alpha 1,6 glucose links between branches

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18
Q

which is the major starch degrading enzyme

A

alpha amylase

19
Q

describe how amylase degrades starch

A

random places in the middle of amylose and amylopectin

20
Q

what does endo-amylase mean

A

attacks in the middle of amylose/amylopectin molecules

21
Q

what does the endoamylase alpha amylase release

A

maltose and maltotriose
dextrins

22
Q

optimum conditions for alpha amylase

A

pH 5.5
70C

23
Q

describe the behaviour of beta amylase

A

starts at one end and chops off two glucose units at a time

24
Q

what does beta amylase release

A

maltose

25
Q

optimal conditions for beta-amylase

A

pH 5.2
60C

26
Q

which amylase is the most thermostable

A

alpha

27
Q

what is the principle sugar in the mash and at what percentage

A

maltose
45%

28
Q

what is the principle sugar in the mash and at what percentage

A

maltose
45%

29
Q

what is the principle sugar in the mash and at what percentage

A

maltose
45%

29
Q

what is the principle sugar in the mash and at what percentage

A

maltose
45%

30
Q

what are the two major cell-wall polysaccharides?

A

beta-glucans
pentosans

31
Q

structure of beta glucans

A

glucose straight chain linked by beta-glycosidic linkages

32
Q

what enzymes are needed for the hydrolysis of beta-glucans

A

B-glucanase

33
Q

where are beta-glucans mainly found

A

cell wall (make up 75% of it)

34
Q

what are pentosans

A

sugar polymers

35
Q

describe pentosans shape

A

backbone of xylose and side chains of arabinos

36
Q

what must happen to cell wall polysaccharides during brewing to make a desirable product

A

must be degraded into soluble products

37
Q

if the beta glucna is not properly broekn down what happens

A

increases the viscosity
slows wort sepaeration
reduces beer filtration rate
can cause sediment/haze in beer

38
Q

when is B-glucasnase produced

A

germination

39
Q

why do brewers often start mash at 45-50C

A

B-glucanase + proteinases are very heat sensitive

40
Q

what is proteolysis important for

A

prevention of beer haze
generation of amino acids for yeast growth

41
Q

role of proteinases

A

attack hordeins in the middle of protein molecule to release short linear peptides

42
Q

role of carboxypeptidases

A

chop AA of the chains one by one

FOSC202 (28 decks)

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