Malting/germination process Flashcards
three main components to barley structure
husk
endosperm
aleruone layer
role of the husk
protect seed and growing embryo
why is the husk useful in brewing
it acts as a filter during wort separation
role of the endosperm
bulk nutrients
-starch granules
-the source of fermentable sugars and amino acids
role of the aleurone layer
-source of enzymes
-triggered by hormones produced by the growing embryo
steps of malting
steeping: raise moisture content to trigger germination
Germination: controlled sprouting in grian beds with forced air
kiling: reduces moisture content and dries malt
what happens if steeping is either too short or too long
too short: poor consistency
too long: mould and bacteria grow
purpose of germination
control sprouting
release hydrolytic enzymes
modification of endosperm structure
describe the steeping regime
-first immersion 6-16 hrs 32% water content
-air rest 12-24: expose embryo to O2 and removes CO2
-second immersion 10-20 hrs
describe what is happening to the barley grain during steeping
-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
3 examples of diastatic enzymes
alpha glucosidase
alpha amylase
beta amylase
which enzymes are most important
amylase
how does starch exist in the endosperm
as large or small grnaules
what is the difference in gelatinisation of large and small starch granules
small granules require a higher temperature
what is gelatinisation temperature important
reaching the right temp is important during mashing for the conversion to fermentable sugars
describe amylose shape
linear chains
alpha 1,4 linkages
describe amylopectin shap
short chains
alpha 1,6 glucose links between branches
which is the major starch degrading enzyme
alpha amylase
describe how amylase degrades starch
random places in the middle of amylose and amylopectin
what does endo-amylase mean
attacks in the middle of amylose/amylopectin molecules
what does the endoamylase alpha amylase release
maltose and maltotriose
dextrins
optimum conditions for alpha amylase
pH 5.5
70C
describe the behaviour of beta amylase
starts at one end and chops off two glucose units at a time
what does beta amylase release
maltose
optimal conditions for beta-amylase
pH 5.2
60C
which amylase is the most thermostable
alpha
what is the principle sugar in the mash and at what percentage
maltose
45%
what is the principle sugar in the mash and at what percentage
maltose
45%
what is the principle sugar in the mash and at what percentage
maltose
45%
what is the principle sugar in the mash and at what percentage
maltose
45%
what are the two major cell-wall polysaccharides?
beta-glucans
pentosans
structure of beta glucans
glucose straight chain linked by beta-glycosidic linkages
what enzymes are needed for the hydrolysis of beta-glucans
B-glucanase
where are beta-glucans mainly found
cell wall (make up 75% of it)
what are pentosans
sugar polymers
describe pentosans shape
backbone of xylose and side chains of arabinos
what must happen to cell wall polysaccharides during brewing to make a desirable product
must be degraded into soluble products
if the beta glucna is not properly broekn down what happens
increases the viscosity
slows wort sepaeration
reduces beer filtration rate
can cause sediment/haze in beer
when is B-glucasnase produced
germination
why do brewers often start mash at 45-50C
B-glucanase + proteinases are very heat sensitive
what is proteolysis important for
prevention of beer haze
generation of amino acids for yeast growth
role of proteinases
attack hordeins in the middle of protein molecule to release short linear peptides
role of carboxypeptidases
chop AA of the chains one by one
