Malting Stages Flashcards
Evaluate and explain the purpose of each stage in the malting process.
1
Q
What is the purpose of each stage in the malting process?
A
To evaluate and explain the purpose of each stage in the malting process
The malting process includes steeping, germination, and kilning stages, each with specific goals.
2
Q
What physical and biochemical changes occur during malting?
A
Changes in metabolism and structure, respiration of grains converting sugar into energy
These changes affect malt quality significantly.
3
Q
How do dormancy and water sensitivity affect the malting process?
A
Dormancy prevents premature germination; water sensitivity impacts moisture absorption
Both factors are crucial for successful malting.
4
Q
What is the effect of vessel design on malting and malt quality?
A
Vessel design influences moisture distribution and oxygen availability during malting
This can significantly affect the efficiency of the malting process.
5
Q
What is the optimal moisture level for grain storage?
A
10-12%
This level prevents spoilage and maintains grain viability until malting.
6
Q
What moisture level initiates germination in grains?
A
Above 30%
Effective moisture levels for germination are typically between 32-35%.
7
Q
What is the ideal moisture level for germination?
A
43-46%
This level ensures uniform hydration and modification of the kernel.
8
Q
How does water enter the grain during steeping?
A
Through the micropyle
Water moves from high to low concentration areas within the grain.
9
Q
What factors influence water uptake in barley grains?
A
Temperature, grain size, protein content, endosperm composition, husk integrity
Each factor plays a role in the efficiency of water absorption.
10
Q
True or False: Smaller grains absorb water faster than larger grains.
A
True
Smaller grains have less material to hydrate and shorter distances for water to migrate.
11
Q
What is the germinative capacity (GC) test?
A
A test that involves cutting 100 grains and staining them to check for viability
Living embryos stain pink, while dead ones remain white or discolored.
12
Q
What does a low germinative capacity (GC) result indicate?
A
A low percentage of viable grains
This suggests insufficient grains for successful malting.
13
Q
What is the purpose of the germinative energy (GE) test?
A
To measure the ability of grains to germinate after being wetted
The GE result indicates the actual germination potential of the grains.
14
Q
What is dormancy in seeds?
A
A natural protective mechanism that prevents premature germination
Dormancy can vary by variety and must be overcome for successful malting.
15
Q
Fill in the blank: Dormancy naturally breaks or declines with _____ or it can be removed by heat introduced during the drying process.
A
time
This allows the barley to be malted effectively post-harvest.
16
Q
What happens if only a small section of the endosperm is hydrated?
A
Uneven endosperm modification occurs
This leads to inconsistent malt quality.
17
Q
What is the significance of husk integrity during malting?
A
It affects the hydration rate of grains
Split husks lead to faster hydration compared to intact husks.
18
Q
What is dormancy in barley?
A
Dormancy is a period where barley seeds do not germinate. It can break naturally over time or be removed more quickly by heat during drying.
19
Q
How long can modern barley varieties remain dormant before being ready for malting?
A
1-2 months post-harvest.
20
Q
What is water sensitivity in grains?
A
Water sensitivity is a phenomenon where grains do not germinate when there is an excess of water due to competition with microorganisms for oxygen.
21
Q
How is water sensitivity tested?
A
By using the GE test with 8 mL of water instead of 4 mL.
22
Q
What is the equation for calculating water sensitivity?
A
Water sensitivity = number of germinated grains in 4 mL test - number of germinated grains in 8 mL test.
23
Q
True or False: Water sensitivity can disappear with grain storage.
A
True.
24
Q
What is gibberellic acid (GA) and its role in barley?
A
GA is a hormone that stimulates enzyme production necessary for nutrient breakdown in the endosperm during germination.
25
List the enzymes synthesized de novo in response to GA.
* α-Amylase - starch
* Limit dextrinase - starch
* Endoproteases - protein
26
List some enzymes that are activated during the malting process.
* Endo β-(1,3)(1,4) glucanase - β-glucans
* Endo β-(1,3) glucanase - β-glucans
* Pentosanase - pentosans
* β-Amylase - starch
* Carboxypeptidases - polypeptides
* Phytase - phosphate containing compounds
* Lipase - lipids
27
What is the moisture increase in barley during steeping?
From ~12% to ~45%.
28
At what kernel moisture does germination start?
Germination starts at kernel moistures > 30%.
29
What is the chit in barley germination?
The chit is the first root that appears after 24 hours, indicating that germination has commenced.
30
What is the purpose of steeping vessels?
* Hydrate the grain
* Remove CO2
* Remove toxic metabolites
* Remove competitive microorganisms
* Remove excess heat
* Provide oxygen
* Enable air rests
31
What is a conical steep?
A conical steep is a cylindroconical vessel designed for barley steeping, allowing easier emptying due to gravity.
32
True or False: Flat-bottom steeps can be designed for combined steeping and germination.
True.
33
What is the main disadvantage of combined steeping and germination vessels?
They have to compromise between the requirements of different stages.
34
What material is typically used to construct steeping vessels?
Stainless steel or concrete with a stainless steel lining.
35
Describe the filling process of steeping vessels.
Barley is transferred into the steeping vessel from above, either dry or pre-wetted, to minimize dust production.
36
What is the purpose of ventilation in steeping vessels?
To aerate the barley in both immersion (wet) and drained (dry) stands.
37
What is the function of the support screen in steeping vessels?
It holds the barley while water fills or empties from the vessel.
38
Fill in the blank: The first root that appears after 24 hours of germination is called the _______.
[chit]
39
What do steep vessels have for aeration?
Aeration nozzles beneath the perforated floor and on the vessel sides
40
How is aeration achieved in conical steeps?
Through nozzles or an aeration ring in the cone of the vessel
41
What is the function of the mixing tube in conical steeps?
It extends from the top to the cone and helps to mix the contents by drawing in the water/grain slurry
42
During air rests, what happens to barley?
It respires more vigorously, heating up and producing CO2
43
What must be done with CO2 produced during respiration?
It must be removed and replaced with fresh air
44
What are the three purposes of adding fresh air during the air rest?
* Removal of CO2
* Removal of heat
* Provision of oxygen
45
What is the definition of steeping?
Not simply immersing grain in water; involves submerged for set periods and drained for set periods
46
What quality must water used for steeping meet?
It must be clean, potable, free of pathogens, dissolved organic material, heavy metals, and low in chlorine
47
What factors vary the appropriate steeping programme?
* Variety
* Season
* Time after harvest
48
What must be known to establish the appropriate steeping programme?
* Varietal purity
* Current moisture level
* Germinative energy
* Germinative capacity
* Water sensitivity
* Total nitrogen
49
What is the typical temperature range for the 1st immersion in steeping?
12-15°C
50
What is the typical duration for the 1st air rest in steeping?
12-14 hours
51
What happens if water-sensitive barley is steeped too long?
It can fail to germinate
52
What moisture level is suitable to initiate germination?
30-33%
53
What temperature must not exceed during air rest to avoid damage to grain?
23°C
54
What happens if the grain temperature exceeds 21-23°C?
It can cause damage to the grain
55
What is the main role of enzymes during germination?
To break down structures of the endosperm
56
What are the two forms of starch in barley?
* Amylose
* Amylopectin
57
Which enzyme breaks down the protein matrix surrounding starch granules?
Proteases
58
What is the first malt enzyme activated on Day 1 of germination?
Carboxypeptidase
59
What promotes protease formation during germination?
* Higher moisture content
* Lower germination temperatures
60
What is the consequence of too little protein breakdown during germination?
Incomplete modification and hard ends
61
What is the consequence of too much protein breakdown during germination?
Destruction of proteins needed for beer foam
62
What are the key enzymes involved in starch breakdown during germination?
* α-amylase
* β-amylase
* Limit dextrinase
63
True or False: The enzymes required for modification during germination are all present at the start.
False
64
What must happen to the pentosan layer before β-glucanases can degrade the cell walls?
It must be broken down by several enzymes including xylanases
65
What is the role of β-glucan solubilase during germination?
It attacks the protein links that keep the β-glucan chains rigid
66
What happens if there is too little modification during grain processing?
Results in incomplete modification and hard ends (areas of unmodified endosperm at the tip of the grain)
67
What occurs if there is too much modification during grain processing?
Destroys the proteins needed for beer foam
68
What is required for starch breakdown during germination?
Balance in degradation of small and large starch granules
69
What happens to small starch granules if they are not degraded?
They form unfilterable beer haze
70
What is the role of large starch granules in the mash?
They need to be left largely intact to be converted into sugar
71
What do α-amylase and β-amylase produce during starch degradation?
A mixture of short chain sugars and longer chain dextrins
72
How does α-amylase break down starch?
Randomly breaks glucose links within the starch molecule
73
What does β-amylase produce from starch?
Two glucose units (called maltose) from the chain ends
74
What is the function of limit dextrinase?
Breaks the branch points in starch, creating shorter chains
75
What factors influence the level of α- and β-amylases?
* Barley variety
* Climatic conditions
* Size of kernels
* Moisture levels in green malt
* Germination temperatures
76
What is phytase?
An enzyme that produces phosphate from phytic acid in barley
77
What is the role of phosphate produced by phytase?
Used in cellular functions such as energy release
78
What do lipases and phospholipases do during germination?
Break down lipids (fats) in the grain to produce fatty acids
79
What is the significance of fatty acids produced during germination?
They are a vital source of energy for the developing embryo and are important for yeast nutrition
80
What compound is formed from the oxidation of linoleic acid by lipoxygenase enzymes?
E-2-nonenal
81
What flavor does E-2-nonenal impart to beer?
A cardboard aroma/flavour, significant in stale beer
82
What is the impact of excess fertilizer on the density of the protein matrix in grains?
It leaves the grains hard and steely, resistant to protein-degrading enzymes
83
What does gibberellic acid (GA) stimulate during germination?
Enzyme production
84
What is the structure of commercially produced GA3 made by?
Fungi, Fusarium moniliforme or Gibberella fujikuroi
85
What properties are increased by gibberellic acid during malting?
* Extract
* Soluble proteins
* Colour
* α-Amylase
86
What properties are decreased by gibberellic acid during malting?
Germination time
87
What is the traditional method of germination called?
Floor maltings
88
What are the key features of modern germination systems?
* Stainless steel wedge-wire or perforated floor
* Means of turning the grain bed
* Pressure fan with air humidification unit
* Means of blowing cool, moist air through the grain bed
89
What is the purpose of turning the grain bed in germination vessels?
To prevent overheating and drying out too quickly
90
What is the operation mechanism of Saladin boxes?
A beam moves along the length of the box with helical screws that turn the bed
91
What is the Wanderhaufen system in germination?
The germinating malt is moved in steps along an extended box or 'street'
92
What two parameters can be adjusted to control germination?
* Bed temperature
* Moisture in the bed
93
What is the ideal grain bed temperature range during germination?
16-21˚C
94
What is the purpose of controlling air-on temperature during germination?
To cool the grain bed and maintain germination temperature
95
True or False: Air-on temperature is higher than germination temperature.
False
96
What is the purpose of monitoring air-on temperature during germination?
To control air-on temperatures due to high CO2 levels that can reduce the rate of germination.
## Footnote
Air-on temperature is monitored with temperature probes.
97
What is the significance of maintaining a specific difference between air-on and air-off temperatures?
It helps control the germination process effectively.
## Footnote
This is crucial for optimizing germination conditions.
98
How does respiration affect grain moisture during germination?
Respiration increases the bed's temperature, reducing the grain's moisture content.
## Footnote
Grain can lose roughly 0.5% moisture per day.
99
What is the optimal moisture content to maintain during the highest respiration rate?
43-46%
## Footnote
This level is essential to support active growth and respiration.
100
What role do water spray nozzles on the turner arm play during germination?
They maintain bed moisture by spraying water on the kernels.
## Footnote
The helical screws turn the grain while water is applied.
101
What are the key factors to consider regarding moisture and temperature during germination?
* The effect of moisture on modification
* The effect of temperature on modification
* The effect of temperature on enzymes
* The effect of temperature on the rate of modification
102
True or False: Increasing moisture or temperature decreases the rate of modification.
False
## Footnote
Higher moisture or temperature generally increases the rate of modification.
103
What is the acrospire growth test used for?
To determine if the grain is modifying at the required rate.
## Footnote
It involves boiling kernels in copper sulphate solution to visualize acrospires.
104
What indicates over-modification in acrospires?
Acrospires longer than the kernel (> 1) are considered over-modified.
## Footnote
Uniform length of acrospires is critical for consistent malt quality.
105
List some quality checks that can be carried out during germination.
* Moisture content analysis
* Acrospire growth
* Visual analysis
106
What does visual analysis involve during germination quality checks?
Rubbing grains between thumb and forefinger to check for modification.
## Footnote
Properly modified grains appear chalky, while under-modified grains form balls.
107
How long does barley typically spend in the germination vessel?
Four to six days.
## Footnote
Over-modification can reduce extract levels due to starch loss.
108
What is kilning in the malting process?
The final and most energy-intensive stage of malting.
## Footnote
It typically takes 24 to 48 hours to achieve the desired moisture level.
109
What is the ideal bed depth during kilning?
Around 0.75 m.
## Footnote
This reduces differences in malt produced at various bed heights.
110
List the reasons for kilning green malt.
* To reduce moisture content for safe transport and storage
* To stop embryo growth at optimal modification
* To produce unique flavours and colours
* To drive off dimethyl sulphide (DMS)
* To create a product that can be easily milled
111
What percentage of energy does kilning typically consume in the malting process?
75-85%.
## Footnote
High air-on temperatures are used to evaporate moisture during kilning.
112
What is the final moisture level of grain after kilning?
Between 3-6%.
## Footnote
Lower moisture levels can lead to brittle malt.
113
What changes occur to enzymes during kilning?
Some enzymes are lost due to prolonged exposure to high temperatures.
## Footnote
Low temperatures during initial kilning stages help preserve enzymes.
114
What reaction occurs when sugars and amino acids are exposed to heat during kilning?
The Maillard reaction.
## Footnote
This reaction contributes to the colour and flavour of malt.
115
What undesirable flavour does dimethyl sulphide (DMS) impart to beer?
A vegetable-, cabbage-, or sweetcorn-like flavour.
## Footnote
DMS is formed from S-methylmethionine (SMM) during kilning.
116
What is nitrosodimethylamine (NDMA)?
A toxic, water-soluble compound that can cause cancer.
## Footnote
Historically, direct-fired kilns increased the risk of NDMA formation.
117
What is Nitrosodimethylamine (NDMA)?
Water soluble, toxic to human organs, causes cancer
## Footnote
NDMA is a hazardous compound that can be formed during the malting process.
118
What historical practice increased the risk of NDMA formation?
Using direct-fired kilns
## Footnote
The nitrogen oxides from the fuel passed through the bed, producing NDMA.
119
What is the allowed level of NDMA in malt according to industry standards?
Below 1 μg/kg
## Footnote
Some textbooks report a level of 2.5 μg/kg.
120
What is the precursor of NDMA found in malt?
Hordenine
## Footnote
Hordenine reacts with NOx-rich air at high temperatures to form NDMA.
121
What enzyme in malt is associated with stale flavors in beer?
Lipoxygenase (LOX)
## Footnote
LOX can give beers a stale cardboard-like flavor as they age.
122
How can LOX be controlled during brewing?
By higher temperatures in kilning
## Footnote
Some malt specifications require LOX to be present only below a specific level.
123
What design feature is common in modern kilns?
Designed to produce high quality malt using minimum energy
## Footnote
Modern kilns focus on efficiency and quality.
124
What was a common early design of kilns?
Rectangular boxes in a double-deck arrangement
## Footnote
The exhaust from the first layer was directed to the second layer.
125
What is the typical bed depth in a kiln?
0.75 m
## Footnote
This allows for even air passage through the malt bed.
126
What is the purpose of large centrifugal fans in kilns?
To force air into a pressure chamber below the floor
## Footnote
This air is then passed through the malt bed.
127
What are the three phases of the kilning process?
Free drying, forced drying, curing
## Footnote
Each phase plays a crucial role in achieving the desired malt characteristics.
128
What parameters are measured to control the kilning process?
* Air-on temperature
* Air-off temperature
* Relative humidity (RH)
## Footnote
These measurements help in adjusting the conditions during kilning.
129
What happens during the free drying phase?
Moisture on the kernel surface is easily removed by airflow
## Footnote
This phase uses warm, dry air at lower temperatures.
130
What is the break point in the forced drying phase?
When the bottom of the free-drying zone reaches or breaks through the top of the malt bed
## Footnote
This causes a sudden increase in air-off temperature.
131
True or False: Enzymes are more resistant to heat when the malt is dry.
True
## Footnote
This property allows for controlled drying at lower temperatures initially.
132
What is latent heat in the context of kilning?
The energy required to evaporate water from the grain surface
## Footnote
It is necessary to break the links between water molecules.
133
What is the drying front in the kilning process?
The progression of drying from the bottom to the top of the malt bed
## Footnote
The driest layer is at the bottom, reaching the forced-drying phase first.
134
What is the purpose of forced drying in the malting process?
To remove moisture from the grain's surface and control air temperature by reducing airflow and increasing air recirculation.
## Footnote
The RH of air leaving the bed in forced drying is low enough to be blended with fresh air for drying the grain, which helps save energy.
135
What is curing in the malting process?
The period where malt moisture approaches 5-8% and air-on temperature is increased to its highest point, typically 78-85˚C for lager malts and 90-100˚C for ale malts.
## Footnote
Darker-coloured malts may reach up to 105˚C.
136
What compounds are formed during the curing phase?
Characteristic colour and flavour compounds, including DMS formed from its precursor SMM.
## Footnote
This phase typically lasts between two and four hours.
137
What is the cooling phase in the malting process?
The phase where malt is cooled down to around 30˚C by passing ambient temperature air through the bed.
## Footnote
Quick and sufficient cooling prevents additional colour pick-up and excessive moisture removal.
138
What happens after cooling in the malting process?
The malt is discharged from the kiln, undergoes the deculming process to remove dried rootlets, and then a final cleaning stage to remove dust and foreign material.
## Footnote
Conveyors transfer the cleaned malt to silos.
139
What is free drying also known as?
Pre-break.
## Footnote
It refers to the stage where moisture on the surface of the grain is removed.
140
What occurs during the break point in the malting process?
Drying enters the forced-drying phase where moisture bound in the grain kernel is driven to the surface and removed.
141
What are the effects of the free-drying stage on grain?
Embryo growth, modification, and enzyme synthesis continue.
142
What happens to enzymatic activity during forced drying?
Enzymatic activity declines and some enzymes are denatured.
143
What is the main focus of the lesson on the malting process?
The investigation of each stage of the malting process and the required physical and biochemical changes involved in the conversion of barley to malt.
144
What should learners be able to evaluate regarding the malting process?
The purpose of each stage in the malting process.
145
How do dormancy and water sensitivity affect the malting process?
They influence the malting process and the quality of the resulting malt.
146
What is the importance of vessel design in the malting process?
It affects the malting process and malt quality.
147
What is the purpose of the germinative capacity (GC) test?
To check if barley can germinate before steeping
## Footnote
The GC test involves cutting 100 grains and staining them with tetrazolium dye.
148
What indicates a living embryo in the germinative capacity test?
Stains pink
## Footnote
Dead embryos remain white or discolored.
149
What is the GC peroxide test?
A test where 200 grains are soaked in 0.75% hydrogen peroxide solution to check germination
## Footnote
The percentage of germinated grains should be > 98%.
150
What does the germinative energy (GE) test measure?
The ability of grains to germinate
## Footnote
It assesses rootlet growth in wetted grains over three days.
151
What does a low GC result imply about the GE test?
Insufficient grains are alive, making GE measurement pointless
## Footnote
Dead grains do not germinate.
152
What is dormancy in seeds?
A natural protective mechanism preventing premature germination
## Footnote
Dormancy varies by variety and can decline over time.
153
How does dormancy affect newly harvested barley?
It prevents germination after rainfall on the mature plant
## Footnote
High dormancy barley requires more storage time until it can be malted.
154
What is the effect of heat during the drying process on dormancy?
It can break or decline dormancy more quickly
## Footnote
Modern barley varieties typically have shorter dormancy periods.
155
What is water sensitivity in barley grains?
A condition where grains do not germinate with excess water
## Footnote
It is caused by microorganisms competing with the embryo for oxygen.
156
How is water sensitivity tested?
By comparing germination rates between 4 mL and 8 mL water tests
## Footnote
Water sensitivity = number of germinated grains in 4 mL test - number of germinated grains in 8 mL test.
157
Why is it important to test for water sensitivity before steeping?
To avoid poor germination due to excess water
## Footnote
Water sensitivity declines with grain storage in most varieties.
158
What happens to water sensitivity in certain barley varieties after storage?
It can remain even after storage
## Footnote
Modified steeping processes may be required for these varieties.
159
What is the next step after checking and testing the grain?
The grain is ready for steeping
## Footnote
Further changes in the grain occur during the steeping process.
