Unit 1 - Malt - Steeping Flashcards
What is the purpose of steeping in the malting process?
To increase the kernel moisture level from storage to optimum for germination
Steeping increases grain moisture from typically 10-12% to around 45%
At what moisture level does germination start?
Above 30%
Moisture levels of 32-35% are effective for germination
What negative effect can moisture levels exceeding 46% have?
Can negatively affect germination
What are the byproducts of respiration during germination?
- CO2
- Water
- Heat
What is the ideal moisture level for germination?
Between 43-46% in the whole kernel
How does water enter the grain?
Through the micropyle
What effect does temperature have on water uptake in grains?
Water uptake is faster at higher temperatures
Fill in the blank: Smaller grains absorb water ______ than larger grains.
faster
How do steely grains differ from mealy grains in water absorption?
Steely grains draw water up more slowly than mealy grains
What is the germinative capacity (GC) test used for?
To check whether barley is acceptable for intake
What does a pink stain indicate in the GC test?
Living embryos
What is measured in the germinative energy (GE) test?
Rootlet growth in grains
What does dormancy in seeds prevent?
Germinating under false starts
What is water sensitivity in grains?
A condition where grains do not germinate when there is excess water
How is water sensitivity calculated?
Water sensitivity = number of germinated grains in 4 mL test - number of germinated grains in 8 mL test
What hormone stimulates enzyme production during malting?
Gibberellic acid (GA)
List key enzymes synthesized de novo in response to GA.
- α-Amylase
- Limit dextrinase
- Endoproteases
What must barley be free from before malting?
- Stones
- Metal
- Foreign seed
- Other materials (dust, broken grains, husks, stalks)
What is the purpose of a steeping vessel?
- Hydrate the grain
- Remove CO2
- Remove toxic metabolites
- Remove microorganisms
- Remove excess heat
- Provide oxygen
- Enable air rests
True or False: Conical steeps are actually conical in shape.
False
What is the major advantage of conical steep vessels?
Easier emptying due to gravity flow
What is a Giracleur used for in steeping vessels?
To level the barley and prevent dry pockets
In flat-bottom steeps, what type of floor is usually constructed?
Wedge wire
What happens during air rests in steeping vessels?
Barley respires vigorously, producing CO2 that must be removed
What is the role of aeration nozzles in flat-bottom steep vessels?
To ventilate and mix the barley
What can happen if oxygen is not replaced during respiration in steeping?
Respiration slows and eventually stops
What is the purpose of the loading spreader in the steeping process?
To draw up barley and deposit it on the surface
What happens to barley during the air rests?
Barley respires more vigorously, heating up and producing CO2
What must be removed and replaced with fresh air during air rests?
CO2
What is the effect of a lack of oxygen on barley respiration?
Slows respiration and eventually stops it
What happens in an atmosphere containing 80% CO2 for barley?
Chitting occurs but embryo development is severely impaired
How is air introduced in a flat-bottom steep?
Air is blown in from underneath or above
How is air introduced in a conical steep?
An external fan draws air through the grain bed from below
What are the three purposes of adding fresh air during the air rest?
- Removal of CO2
- Removal of heat
- Provision of oxygen
What is the definition of steeping?
Not simply immersing grain in water, but submerging for set periods and draining at intervals
What qualities should water used for steeping have?
- Clean and potable
- Free of pathogens, dissolved organic material, and heavy metals
- Low chlorine levels
What factors influence the steeping programme for grain?
- Variety
- Season
- Time after harvest
What is needed to establish an appropriate steeping programme?
- Varietal purity
- Current moisture level
- Germinative energy
- Germinative capacity
- Water sensitivity
- Total nitrogen
What is the temperature range for the first immersion in the steeping cycle?
12-15°C
What is the typical temperature range during the first air rest?
12-14°C
What should be done for water sensitive barley during the steeping process?
Shorter immersions followed by longer air rests
What moisture level is suitable to initiate germination in barley?
30-33%
What is the maximum grain temperature during an air rest to avoid damage?
23°C
What is the typical temperature range for water and air during barley growth?
9-16°C
What must not exceed 21-23°C to avoid damaging the grain?
Grain temperature
Fill in the blank: Water sensitive grain should have a ______ initial immersion, followed by a longer air rest.
short
