Malt Flashcards
Describe the components of a barley kernel. And the role they play in the malting/ brewing process
Husk, Pericarp and testa, Scutellum, Aleurone layer, Embryo, Endosperm
Husk
Dry outer shell (cellulose and lignin, as well as silica, and polyphenols)
- protects embryo inside
- forms a filter bed during wort separation.
Pericarp and testa
Layer below husk
- pericarp restricts water uptake
- testa has a waxy coating that limits water uptake and prevents nutrients leaving the grain.
In the beer it contributed to mouthfeel, can form haze when combined with proteins, and can reduce the rate at which beer goes stale.
Gibberellic acid
Plant hormone produced by the embryo
- increases enzymes that break down the compounds to nutrients that feed the barley embryo
Scutellum
“Shield”
- enables nutrients to move between the endosperm and embryo
Aleurone layer
Layer below pericarp and testa
- responds to gibberellic acid (plant hormone) by secreting enzymes into starchy endosperm.
- breakdown compounds into nutrients, fed to embryo by scutellum.
Embryo
Precursor to new barley plant
- nutrients (lipids, sucrose, proteins) stored here.
- at the base of the kernel and would become a new barley plant it or germinated and was allowed to grow.
Starchy Endosperm
Main food storage: starch cells contained in cell walls made up of carbohydrates and proteins.
- during malting, enzymes break down starch call walls & starch into nutrients for the embryo
- malting controlled so enzymes are available for saccharification & B-glucan breakdown
Two row barley
-plumper grain
- higher starch:protein ratio
- more commonly used
- contains sufficient enzymes, protein and husk material and has higher extract potential.
Six row barley
- higher malt enzyme content, more effective saccharification
- higher protein content
- more husk = better filter bed
- more enzymes that help convert starch into sugar
Malting process
Steeping, Germination, kilning
Steeping
Ensures that all kernels reach the ideal moisture level to start germination.
- wet stand @20*C
- dry sand to prevent o2 loss
- repeat till 43-46% moisture
Chitting
Term used to describe the appearance of the tip of the first root at the end of the grain
Germination
Grain allowed to grow under controlled conditions
- 16-21*, 42-47% moisture
- enzymes released, cell walls & B-glucans dissolved, proteins broken down
- aims to achieve a complete and uniform modification
- takes 3-5 days
Modification
The breakdown of the endosperm cell walls, protein matrix and small starch granules. Modification of the term we fine the changes in the barley kernel that occur as it is turned into malt.
Kilning
Stops germination
- 50* dries malt
- up to 90* to develop colour and flavour
- heat converts SSM (formed during germination) into DMS
Moisture content
Barley-<18%
Steeping- 42-46%
Germination- 42-47%
Kilning -3-5%
Phyisical changed to the barley kernel during malting
- an increase in moisture lever triggers growth of the embryo, which starts to grow chits and rootlets
Biochemical changes during malting
- the level of sugar in the embryo drops which causes the embryo to secrete gibberellic acid (GA)
-GA is released by the embryo and moved to the Aleurone layer where it stimulates enzyme production. - enzymes are secreted by the aleurone layer into the endosperm
-Enzymes help break down both the endosperm cell walls and the protein matrix meaning that the starch granules are exposed. The proteins are broken down into amino acids - enzymes help break down the small starch granules, producing sugar
- the sugars and amino acids are transported to the embryo to use as it grows.
Malt storage
Can be stored in bags or bulk silos
-bagged malt is sealed to reduce uptake of moisture and prevent insects and birds getting in.
- should be kept inside to avoid birds, moisture, insects, and temp fluctuations.
- best stored below 30*C
-silos can be used to store bull malt, must be cleaned before they are filled, once filled should be completely emptied before re-filling.
High protein levels mean malt has lower extract, may not malt consistently,
Barley grains contain
65% starch, 7-12% protein, 2-3% lipids and a range of minerals, enzymes and vitamins
Malt provided enough lipids for our yeast but not so much that the quality of beer is effected
Steeping is usually 40-56 hours
Biochemical changes
Dimethyl sulphide (DMS) smells of cooked sweetcorn and can be produced during the malting process. It is an off-flavour if present in most beers. DMS is formed when S-methyl methionine (SMM) is heated. SMM is produced by the embryo during germination. DMS is volatile so evaporates when it is heated. The maltster must ensure that as much SMM as possible is converted into DMS and evaporates during kilning. If not, there is a risk that DMS will form when the wort is boiled in the brewhouse. Levels of SMM and DMS are usually measured after the malting process and we can specify the level we want in our malt.
Malt modification
Malt used to brew lager traditionally had more enzyme potential (diastatic power), but was under modified. In under modified malts, the protein matrix and endosperm cell walls are not completely broken down. This means that the starch is still locked inside. Under-modified malt can also lead to high β-glucan levels in the wort, which leads to slow wort separation and beer filtration. β-glucans can also form haze in the beer. Undegraded proteins can cause similar problems. When brewing with under modified malt we need to use different temperature stands when mashing to breakdown the β-glucans and proteins which are keeping the starch locked inside the endosperm cell walls. We will describe the different mashing methods in more detail in the Mashing lesson.
Dinethyl suphate is produced
From SMM when heat is applied, suck a kilning
