Malting Process Flashcards
1
Q
What is the purpose of steeping in grain processing?
A
To increase the kernel moisture level from the optimum for storage to the optimum for germination.
Steeping is essential for initiating the germination process.
2
Q
What moisture level does steeping increase grain moisture to?
A
Around 45%.
This is an increase from typical storage levels of 10-12%.
3
Q
What is the minimum moisture level required to initiate germination?
A
Above 30%.
Moisture levels of 32-35% are often effective for germination.
4
Q
What moisture levels can negatively affect germination?
A
Exceeding 46%.
High moisture levels can lead to poor germination results.
5
Q
What is a critical goal during the steeping process?
A
To hydrate every grain to the same extent.
Consistency in moisture levels is crucial for successful germination.
6
Q
What can happen if grains are too moist or too dry?
A
Unmalted or under modified grains can result.
This can reduce brewing yields and cause slow filtration.
7
Q
Fill in the blank: Steeping increases grain moisture from _______ to around 45%.
A
10-12%.
8
Q
What happens to a dormant kernel as it germinates?
A
It changes into an actively growing grain and undergoes major changes in metabolism and structure.
9
Q
What is the primary function of respiration in germinating grain?
A
Converting sugar from the endosperm into energy for plant growth.
10
Q
What are the byproducts of respiration in germinating grain?
A
- CO2 (carbon dioxide)
- H2O (water)
- 36 ATP (energy)
- Heat
11
Q
During the steeping process, what does the grain primarily use?
A
The oxygen dissolved in the water.
12
Q
How is most of the oxygen required for grain growth provided?
A
During air rests.
13
Q
What must the maltster do during the steeping process?
A
- Remove CO2
- Remove heat
- Provide oxygen
14
Q
What triggers germination in grains?
A
An increase in moisture.
15
Q
What happens if only a small section of the endosperm is hydrated?
A
Enzymes can only access that section, leading to uneven endosperm modification.
16
Q
What is the ideal moisture level for germination in the whole kernel?
A
Between 43-46%.
17
Q
What principle explains the movement of water into the grain?
A
Osmosis.
Lower osmotic pressure water enters through the semi permeable membrane into the higher osmotic pressure (lower water concentration) area
18
Q
What allows water to flow into the grain while preventing sugar molecules from leaving?
A
The semipermeable membrane covering the embryo.
19
Q
What hydrates faster during germination, the embryo or the surrounding tissue?
A
The embryo.
20
Q
Where does most of the water enter the grain from?
A
The micropyle.
21
Q
How does temperature affect water uptake in barley?
A
Water uptake is faster at higher temperatures.
After six hours, there is not much difference between 10°C and 20°C. After 14 hours, moisture levels reach about 36% at 20°C and around 30% at 10°C.
This indicates that higher temperatures significantly enhance moisture absorption over time.
22
Q
What is the moisture content range for barley after steeping?
A
The moisture content increases from 12% to 25% in the initial phase and can reach about 36% at 20°C after 14 hours.
This shows the importance of time and temperature in the steeping process.
23
Q
What happens to α-amylase production when higher temperature steep water is used?
A
Using higher temperature steep water can limit the production of α-amylase.
This is crucial as α-amylase plays a significant role in starch conversion during malting.
24
Q
How does grain size affect water absorption?
A
Smaller grains absorb water faster than larger grains because they have less material to hydrate and shorter distances for water migration.
This physical property influences the efficiency of the malting process.
25
What distinguishes mealy grains from steely grains in terms of water uptake?
Mealy grains draw water up more quickly than steely grains due to their different protein content and endosperm composition.
## Footnote
The steely endosperm's structure resembles a stone, while mealy endosperm is sponge-like.
26
What challenges arise from grains with both mealy and steely areas?
Grains with both mealy and steely areas are difficult to malt because steeping long enough for the steely area risks overhydrating the mealy area.
## Footnote
This can lead to uneven modification during the malting process.
27
How does husk integrity affect hydration rates in grains?
Grains with split husks hydrate faster than those with intact husks.
## Footnote
Split husks allow for more efficient water absorption, particularly following rain during ear filling.
28
What is the purpose of the germinative capacity (GC) test?
To check whether barley has the ability to germinate
• GE = “How fast will this barley germinate under normal conditions?”
• GC = “What’s the total number of grains that can germinate, even if dormant?”
## Footnote
The GC test is usually undertaken when barley is delivered to the malt plant.
29
How is the germinative capacity (GC) test performed?
Cut 100 grains longitudinally and stain with tetrazolium dye
## Footnote
Living embryos stain pink, while dead embryos remain white or discolored.
30
What does a GC test result indicate?
It indicates how much of the barley is alive
## Footnote
However, being alive does not guarantee that grain will germinate.
31
What is the minimum acceptable percentage of grains that should germinate in the GC peroxide test?
> 98%, preferably 100%
## Footnote
Two sets of 200 grains are soaked in a 0.75% hydrogen peroxide solution.
32
What does the germinative energy (GE) test measure?
The ability of the grain to germinate
## Footnote
The GE test is conducted after confirming viability through the GC test.
33
How is the germinative energy (GE) test conducted?
Wetting 100 grains and checking for rootlet growth each day for three days
## Footnote
4 mL of water is used in the standard GE test.
34
What does the difference between GC and GE results indicate?
It measures dormancy
## Footnote
Dormancy varies from variety to variety and affects germination timing.
35
What is dormancy in seeds?
A natural protective mechanism that prevents premature germination
## Footnote
This mechanism helps seeds avoid germinating under false conditions, such as sporadic rainfall.
36
How does barley dormancy change over time?
It declines gradually, increasing GE until it approaches GC
## Footnote
Newly harvested barley typically has built-in dormancy.
37
What is water sensitivity in grains?
A phenomenon where grains do not germinate when there is excess water
## Footnote
It is thought to be due to microorganisms competing with the embryo for oxygen.
38
How is water sensitivity tested?
Using the same method as the GE test with 8 mL of water instead of 4 mL
## Footnote
Water sensitivity is calculated by comparing germination results from both tests.
39
What equation is used to calculate water sensitivity?
Water sensitivity = number of germinated grains in 4 mL test - number of germinated grains in 8 mL test
## Footnote
It highlights the impact of excess water on germination.
40
Why is it important to test for water sensitivity before steeping?
To avoid poor germination due to excess water in the steep
## Footnote
Water sensitivity can decline with grain storage in most varieties.
41
What happens to water sensitivity in certain barley varieties after storage?
Some remain water sensitive even after storage
## Footnote
These varieties may require a modified steeping process.
42
What is the next step after checking and testing the grain?
Preparing the grain for steeping
## Footnote
The steeping process involves specific changes in the grain.
43
What is the hormone that acts as a chemical message for enzyme activation in barley?
Gibberellic acid (GA)
## Footnote
GA is crucial for the malting process as it stimulates enzyme production.
44
What happens to the embryo's energy stores during growth?
It uses up its energy stores and must obtain nutrients from the endosperm.
45
Which layer does gibberellic acid (GA) flow to stimulate enzyme production?
Aleurone layer
46
What is the first root that appears after 24 hours of germination called?
Chit
47
List the enzymes synthesized de novo in response to gibberellic acid (GA).
* α-Amylase – starch
* Limit dextrinase – starch
* Endoproteases – protein
48
What is the moisture percentage increase during steeping?
From ~ 12% to ~ 45%
49
At what kernel moisture percentage does germination start?
Greater than 30%
50
Fill in the blank: GA is produced by the _______ from a stored precursor.
embryo
51
What is the purpose of cleaning barley before steeping?
To remove foreign material such as stones, metal, foreign seed, dust, broken grains, husks, and stalks.
## Footnote
Cleaning is crucial to prevent damage to equipment and ensure quality.
52
What are the methods for mixing barley with water?
* Dry grain transferred to steep vessel, water pumped in afterwards
* Water/barley mixing vessels
* Barley washers that clean and hydrate the grain
53
What are the main functions of a steeping vessel?
* Hydrate the grain
* Remove CO2
* Remove toxic metabolites
* Remove competitive microorganisms
* Remove excess heat
* Provide oxygen
* Enable air rests
54
What types of duties can flat-bottom steeps be designed for?
* Steeping only
* Combined steeping and germination (SGV)
* Combined steeping, germination, and kilning (SGKV)
55
What are the drawbacks of SGVs and SGKVs?
They require a high volume of water and are prone to structural stresses that can lead to cracking, necessitating frequent repairs.
## Footnote
This is due to the cycling between low and high temperatures.
56
What is the function of the wedge wire floor in flat-bottom steeps?
Allows water to flow through while holding back barley.
57
How is barley transferred into the steeping vessel?
Barley can be transferred dry or pre-wetted using a barley washer or mixer.
58
What is the role of aeration in steep vessels?
To ventilate barley during immersion and drained states, removing CO2 and providing oxygen.
59
What happens during the air rests in steeping?
Barley respires, producing CO2, which must be removed and replaced with fresh air to prevent oxygen deficiency.
60
Fill in the blank: A lack of oxygen slows _______ enzyme production dramatically.
α-amylase
61
What can happen to barley in an atmosphere containing 80% CO2?
Chitting occurs, but embryo development is severely impaired.
62
What is steeping in the context of grain processing?
Steeping is not simply immersing grain in water. The grain is submerged for set periods and the steeping vessel is left drained for set periods.
63
What qualities must the water used for steeping be free of?
Pathogens, dissolved organic material, heavy metals, and low chlorine levels.
64
What factors influence the appropriate steeping programme for grain?
Variety, season, and time after harvest.
65
What is required to establish the appropriate steeping programme?
Varietal purity, current moisture level, germinative energy, germinative capacity, water sensitivity, total nitrogen.
66
What is the temperature range for the first immersion in steeping?
12-15°C.
67
What is the optimal moisture level to initiate germination in grain?
30-33%.
68
What is the maximum temperature that must not be exceeded during an air rest?
23°C.
69
What is used to ensure that the grain does not lose moisture during the air rest?
Humidified air (> 95% relative humidity).
70
What is the typical temperature range for water and air during steeping?
9-16°C.
71
What components strengthen the cell walls of barley endosperm?
β-glucan, pentosan, and a protein layer
## Footnote
The protein layer acts as a shield protecting the starch granules.
72
What must happen to the protein layer to access the starch granules?
The protein must be degraded
## Footnote
Degrading the protein layer exposes the starch granules for enzymatic hydrolysis.
73
What are the two forms of starch found in the granules?
* Amylose
* Amylopectin
## Footnote
Amylopectin has a branched structure that requires specific enzymes for conversion to sugars.
74
What enzyme is needed to convert amylopectin to sugars?
Limit dextrinase
## Footnote
This enzyme is essential for the complete breakdown of branched amylopectin.
75
What is the purpose of cleaning barley before steeping?
To remove foreign material such as stones, metal, dust, broken grains, husks, and stalks
## Footnote
Metal objects and stones can damage equipment, hence they are removed using screens and destoners.
76
What are the key functions of a steeping vessel?
* Hydrate the grain
* Remove CO2
* Remove toxic metabolites
* Remove competitive microorganisms
* Remove excess heat
* Provide oxygen
* Enable air rests
77
What is the function of a barley mixer?
To combine dry barley with water, enabling a slurry to be pumped wet to the steeping vessel
78
What is the role of the supporting screen in steep vessels?
To hold the barley while water fills or empties from it
79
What ventilation methods are used in flat-bottom steep vessels?
Aeration nozzles beneath the perforated floor and on the vessel sides
80
During air rests, what happens to the barley?
It respires more vigorously, heating up and producing CO2
81
What are the three purposes of adding fresh air during the air rest?
* Removal of CO2
* Removal of heat
* Provision of oxygen
82
What are the requirements for water quality used in steeping?
Water used for steeping should be clean and potable, free of pathogens, dissolved organic material, heavy metals, and have low chlorine levels.
83
What factors influence the appropriate steeping programme for grain?
Factors include varietal purity, current moisture level, germinative energy, germinative capacity, water sensitivity, and total nitrogen.
84
What is the temperature range for the first immersion in the steeping process?
12-15°C.
85
What is the typical duration of the first air rest in the steeping process?
1-16 hours starting; 17-18 hours finishing.
86
What moisture level is suitable for initiating germination in grain?
30-33%.
87
Fill in the blank: Each barley variety has an optimum temperature, but the typical range for water and air temperatures is between ______.
9-16˚C.
88
What is the consequence of giving too much water too quickly to the grain?
The grain becomes saturated and is slower to progress to chitting.
89
What is the importance of humidified air during the air rest periods?
Humidified air (> 95% relative humidity) is used to ensure that the grain does not lose moisture.
90
What is the temperature range for grain during steeping to avoid damage?
21-23°C.
91
What happens if the temperature of the grain exceeds 23°C during an air rest?
It can cause damage to the embryo and impair the enzyme systems needed for germination.
92
What are the main enzymes involved in the modification of barley endosperm during germination?
Key enzymes include β-glucan solubilase, endo-β-glucanases, pentosanases, endo and exoproteases, α-amylase, and β-amylase.
93
What is the target for the action of the enzymes of modification?
Barley endosperm cells containing barley starch
## Footnote
The endosperm cells act as a protective barrier for starch granules.
94
What is the role of β-glucan solubilase?
Breakdown of protein in cell walls
## Footnote
It aids in the degradation of the cell wall to access starch granules.
95
What is the function of α-amylase in the endosperm?
Breakdown of small starch granules to produce sugars for embryo growth
## Footnote
It is crucial for providing energy to the growing embryo.
96
True or False: The enzymes required for modification during germination are all present at the start.
False
## Footnote
The enzymes become available in a specific sequence during the germination process.
97
What is the role of endo and exoproteases in the endosperm?
Breakdown of protein matrix surrounding starch granules to make FAN and polypeptides
## Footnote
FAN refers to free amino nitrogen, which is important for yeast nutrition.
98
What is the role of endo-β-glucanases in the breakdown of β-glucan?
They degrade long, viscous chains of β-glucan to form short, non-viscous chains.
99
What initiates the degradation of the protein matrix surrounding starch granules?
Once the β-glucan cell wall has been opened, proteases begin to degrade the protein matrix.
100
What can result from an imbalance in protein breakdown during germination?
Too little proteolysis results in incomplete modification and hard ends, while too much destroys proteins needed for beer foam.
101
What happens to small starch granules if not adequately degraded during germination?
They can form unfilterable beer haze.
102
What are the products of starch breakdown by α-amylase and β-amylase?
* Short chain sugars (for embryo growth)
* Longer chain dextrins
103
How does α-amylase degrade starch?
It randomly breaks glucose links within the starch molecule.
104
What is the role of limit dextrinase in starch degradation?
It breaks the branch points, creating shorter chains.
105
What factors influence the level of α- and β-amylases?
* Barley variety
* Climatic conditions
* Kernel size
* Moisture content in green malt
* Germination temperatures
106
What is the function of lipase during germination?
It breaks down lipids in the grain to produce fatty acids, which are vital for the developing embryo and yeast nutrition.
107
What is the significance of lipoxygenase enzymes (LOX) in beer?
They can oxidize fatty acids, leading to the formation of E-2-nonenal, which contributes to stale beer flavor.
108
What factors can affect the degree of modification in malt endosperm?
The density of the protein matrix, which can be influenced by fertilizer use and total nitrogen content.
109
What are the two parameters that can be adjusted to control germination?
1. Bed temperature 2. Moisture in the bed
110
What is the optimal grain bed temperature range for germination?
16-21˚C
111
How is moisture in the bed achieved?
By controlling relative air humidity and spraying the bed
112
What is the ideal relative air humidity for germination?
> 95% or 100% is better
113
What is the air-on temperature?
The temperature of the humidified air
114
How is the air-on temperature controlled?
By spraying chilled water through nozzles
115
What is the maximum percentage of recirculated air that can be used?
80%
116
What happens to the grain’s moisture due to respiration?
It decreases
117
How much moisture can grain lose per day?
Roughly 0.5%
118
What is the vital moisture content range to maintain during high respiration?
43-46%
119
What is one quality check that can be carried out during germination?
Moisture content analysis
## Footnote
Other quality checks include acrospire growth and visual analysis.
120
What does visual analysis involve in the context of germination?
Rubbing grains between your thumb and forefinger
## Footnote
This checks for the modification of the starchy endosperm.
121
What does it indicate if the starchy endosperm looks like chalk on your fingers?
The green malt is correctly modified
## Footnote
This means the germination process has been successful.
122
What happens if there is still cell wall material present in the malt?
It forms little balls when rubbed between fingers
## Footnote
This indicates the malt is under modified.
123
What is a consequence of over modification in germination?
It can reduce extract levels
## Footnote
Over modification leads to loss of starch to embryo growth.
124
What problems can the friable nature of over modified grain cause?
Problems during milling
## Footnote
It can lead to shattering, dust losses, and finer grist than required.
125
What issues can under modified grain cause in the brewhouse?
Problems during filtration due to undegraded β-glucans
## Footnote
This affects the brewing process negatively.
126
How long does kilning typically take to achieve the required moisture level?
24 to 48 hours.
127
What is the ideal bed depth during kilning?
Around 0.75 m.
128
What are some reasons for kilning green malt?
To reduce moisture content, so that the malted barley can be safely transported and stored.
To stop growth of the embryo at a point when the malt is well modified and will provide a high yield of starch and protein extract.
To produce unique flavours and colours.
To drive off dimethyl sulphide (DMS)
To create a product that can be easily milled
129
What unique qualities does kilning produce in malt?
Unique flavours and colours.
130
What compound is driven off during kilning?
Dimethyl sulphide (DMS).
131
What is a benefit of kilning in terms of milling?
To create a product that can be easily milled.
132
What is the range of grain moisture received in the kiln?
43-46%.
133
What is the final moisture level to which grain is dried during kilning?
Between 3-6%.
134
What happens if the moisture level is lower than 3%?
It is a waste of energy and the malt produced can be too brittle.
135
What happens to enzymes when green malt is exposed to high temperatures for too long?
More enzymes are lost.
136
What is the effect of kilning on barley enzymes?
Kilning kills the embryo but can preserve barley enzymes to varying degrees with the correct application of heat
## Footnote
Preserving enzymes is essential for the mashing process in the brewery, where protein and starch breakdown are completed.
137
How can low temperatures during the initial stages of kilning affect enzymes?
They help preserve enzymes
## Footnote
This is crucial for maintaining enzyme activity for the mashing process.
138
What is the Maillard reaction?
A reaction where sugars from starch modification and amino acids from protein modification react to form browning products
## Footnote
These reactions contribute to the color and flavor of malt.
139
What do Maillard reaction products contribute to malt?
They give malt its color and characteristic flavour
## Footnote
Ale malts have more intense kilning regimes than lager malts, resulting in more color and flavor.
140
What happens to S-methylmethionine (SMM) during kilning?
It converts to dimethyl sulphide (DMS), which imparts undesirable flavors to beer
## Footnote
DMS can give a vegetable, cabbage, or sweetcorn-like flavor.
141
How is DMS removed during kilning?
DMS evaporates easily and is removed in the exhaust air
## Footnote
Not all SMM is converted by the end of kilning, leading to varying levels in malt.
142
What influences the levels of SMM in malt?
Higher germination temperatures, use of GA, and higher protein levels
## Footnote
Higher kilning temperatures and longer kilning times reduce SMM levels.
143
What role does lipoxygenase (LOX) play in malt?
LOX can cause stale, cardboard-like flavors in aged beers
## Footnote
Higher temperatures in kilning can remove LOX.
144
What is the primary goal of modern kilns in malt production?
To produce high quality malt using the minimum amount of energy
## Footnote
Modern kilns focus on efficiency and energy conservation while ensuring high-quality output.
145
What is the purpose of a beam in the kiln design?
To load the green malt in an even layer on a perforated floor
## Footnote
This ensures uniform air passage through the malt bed.
146
What is the typical kiln bed depth?
0.75 m
## Footnote
In comparison, the bed depth of a germinating vessel is approximately 1 m.
147
What happens to the bed's permeability as the grain dries out?
The bed becomes more permeable to air
## Footnote
This change aids in the drying process as the grain loses moisture.
148
What are the three distinct phases of kilning control?
* Free drying
* Forced drying
* Curing
149
What parameters can be measured to control the kilning process?
* Air-on temperature
* Air-off temperature
* Relative humidity (RH)
## Footnote
RH is sometimes not measured due to inaccuracies from dust.
150
What is the air-on temperature range typically used during free drying?
50-60˚C, as low as 40˚C for highly enzymatic malt
## Footnote
Higher temperatures can damage malt enzymes.
151
What happens at the break point during the forced drying phase?
All moisture on the surface of the grain has been evaporated, causing a rise in air-off temperature.
## Footnote
The break point marks the transition from free drying to forced drying.
152
What happens to the moisture level inside the grain after the break point?
It falls below 12-18%.
## Footnote
This allows for the moisture to be forced from the center of the grain.
153
What temperature range is typically used for air-on during the curing phase for lager malts?
78-85˚C
## Footnote
Higher temperatures are used for ale and darker malts.
154
What compounds are formed during the curing phase?
Characteristic colour and flavour compounds, including DMS from its precursor SMM.
## Footnote
This phase lasts between two and four hours.
155
What is the purpose of cooling the malt after curing?
To prevent additional colour pick up and excessive moisture removal.
## Footnote
Cooling is done by passing ambient air through the bed.
156
What is the difference between free drying and forced drying?
Free drying removes moisture from the surface, while forced drying drives moisture from the grain kernel to the surface.
## Footnote
Enzymatic activity declines during forced drying.
