Physical and Chemical Changes During Germination Flashcards
(18 cards)
What happens during germination to the structures of the endosperm?
Enzymes break down the structures of the endosperm in a sequential manner due to the physical structure of the endosperm cells.
What is the pentosan layer and what must happen to it during germination?
The pentosan layer is a porous layer containing organic acids that must be broken down by several enzymes including xylanases before β-glucanases can degrade the cell walls containing β-glucan.
What role does β-glucan solubilase play in the germination process?
β-glucan solubilase attacks the protein links that keep the β-glucan chains rigid and insoluble, resulting in soluble but viscous long chains of β-glucan.
What do endo-β-glucanases do during germination?
Endo-β-glucanases degrade long, viscous chains of β-glucan to form short, non-viscous chains.
What is the function of proteases in the germination process?
Proteases degrade the protein matrix that surrounds and protects starch granules, breaking down larger proteins into polypeptides and then into smaller peptides and free amino nitrogen (FAN).
What process parameters promote protease formation?
- Higher moisture content
- Lower germination temperatures
What is the balance that must be found in protein breakdown during germination?
Too little proteolysis results in incomplete modification and hard ends, while too much destroys proteins needed for beer foam.
What is required for starch breakdown during germination?
The small starch granules must be degraded to prevent unfilterable beer haze, while large starch granules need to remain mostly intact for sugar conversion.
How do α-amylase and β-amylase differ in their action on starch?
α-Amylase randomly breaks glucose links within starch, while β-Amylase is more selective and produces maltose from the chain ends.
What factors affect the levels of α- and β-amylases?
- Barley variety
- Kernel size
- Moisture in green malt
- Germination temperatures
What is the role of phytase in barley germination?
Phytase produces phosphate from phytic acid, which is used in cellular functions such as energy release.
What do lipases and phospholipases do during germination?
They break down lipids in the grain to produce fatty acids, which are a vital energy source for the developing embryo.
What is the consequence of lipoxygenase (LOX) activity during beer aging?
LOX can oxidize fatty acids, forming E-2-nonenal, which imparts a cardboard aroma/flavor to stale beer.
What does the degree of modification in malt endosperm depend on?
It depends on the density of the protein matrix.
How does excess fertilizer affect the grains?
Excess fertilizer leads to a high protein matrix density, making grains hard and resistant to protein-degrading enzymes.
What is gibberellic acid (GA) and its role in germination?
GA is produced by the embryo and stimulates enzyme production, improving the malting process.
What are the properties increased by gibberellic acid (GA) in the malting process?
- Extract
- Soluble proteins
- α-Amylase
What are the properties decreased by gibberellic acid (GA) in the malting process?
- Germination time
- Colour
