The Malting Process

Question 1

What are the main stages of the malting process?

Answer 1

Cereal Delivery
Cereal storage
steeping
germination
kilning

Question 2

How long does the germination process take?

Answer 2

About 4 days or 3-6 days

Question 3

Describe the steeping process

Answer 3

Consists of wet periods and air rests.
Grain is submerged into the water in a steeping vessel
The grain starts to take up water and grow
Most of the water enters the grain by the micropyle
As the grain grows it consumes dissolved oxygen from the steep water and a small amount of starch from the endosperm. This produces energy, CO2 and heat - called respiration.

Question 4

What happens after the wet period?

Answer 4

The steep water is drained away from the vessel, leaving the grain behind. This is the start of the first air rest. During an air rest, the grain will continue to germinate, producing carbon dioxide and heat.
fresh air is drawn through the steeped grain.

Question 5

How long does the steeping process last?

Answer 5

A typical steeping process usually consists of 2-3 wet periods and 2-3 air rests over a period of approximately 48 hours.
First wet period lasts between 4-8 hrs

Question 6

How much does the moisture content increase by after steeping?

Answer 6

The moisture content of the grain increases from about 12% to between 42% and 45%. At this moisture content, the grain starts to grow. The grain is then transferred to a germination vessel.

Question 7

What is the first sign of germination?

Answer 7

The first sign of germination is a small rootlet, known as a chit, appearing at the embryo (proximal end) of the grain.

Question 8

How are vessels typically designed?

Answer 8

conical or flat bottomed

Question 9

Describe the filling & emptying facilities of a steeping vessel

Answer 9

Grain is added via the top of a steeping vessel.

water sprays are used to supress dust which is released when cereals are transported.

The grain in the SV must be relatively flat to ensure it’s all under water & during an air rest ensure the air is evenly drawn through the grain bed.

Question 10

How is grain spread in a conical tank vs a flat bottom tank

Answer 10

Conical - achieved by spreading the grain entering the tank over a cone.

Flat bottom tank - the grain is spread out using rotating arms with blades called giracleur

Question 11

Where is the water inlet in the steeping vessel & how is the water controlled?

Answer 11

water inlet is typically at the bottom of a steeping vessel and the level of water is controlled using sensors inside the steep tank and valves at the inlet.

Question 12

What do the perforated screens at the bottom of a steeping tank do?

Answer 12

allow water to be drained away, leaving the grain behind.

Question 13

Describe a perforated screen in a conical vessel

Answer 13

Perforated screen is small & so is the plenum

Question 14

Describe a perforated screen in a flat bottomed vessel

Answer 14

the entire floor is perforated
The plenum area is quite large & must be filled with water before the water reaches the grain.

Question 15

Which uses more water out of fat bottom vessels vs conical vessels

Answer 15

Flat bottom vessels use more water per tonne of malt than conical vessels

Question 16

In a conical vessel, how is compressed air blown into the steep water?

Answer 16

aeration ring or nozzles in the vessel wall.

Question 17

In a flat bottom vessel, how is compressed air blown into the steep water?

Answer 17

pipes, under the vessel floor.

Question 18

Why do flat bottom vessels have better air flow?

Answer 18

as it has a large area of perforated floor which holds the whole batch. In conical vessels the perforated floor area is smaller than the cross sectional area of grain at the top of the vessel.

Question 19

How do conical and flat bottom vessels draw air through the grain to remove CO2?

Answer 19

Both use fans

Question 20

how is the germination process controlled?

Answer 20

by controlling the temperature of the grain bed and controlling the moisture content of the grain during germination.

Question 21

when the barely starts to grow, what does the embryo produce?

Answer 21

a hormone called gibberellic acid which stimulates the aleurone layer to produce enzymes

Question 22

What are the most important enzymes produced during germination called?

Answer 22

α-amylase – produced by AL. Responsible for the breakdown of starch into glucose chains of various types

β-amylase – present in the endosperm & activated during germination. Responsible for the breakdown of long glucose chains into maltose

Limit dextrinase - responsible for the breakdown of branch points in glucose chains

β-glucanases and pentosanases - responsible for the breakdown of B glucan and pentosan in endosperm cell walls

Proteases - Responsible for the breakdown of the protein matrix in endosperm cell walls

Question 23

Describe heat exchangers in kiling

Answer 23

Heat exchangers are usually made from glass or stainless steel.

To capture the energy - we pass the exhaust air from kilning through a heat exchanger to heat the ambient air.

Question 24

What is peat?

Answer 24

peat is decayed plant material or organic matter which forms over thousands of years

Question 25

What are flavour and aroma compounds from peat called?

Answer 25

Phenols, cresol, eugenol and guaiacol

Question 26

What are the malt quality parameters of importance to the distiller?

Answer 26

Moisture Extract Friability and homogeneity fermentability and predicted spirit yield enzyme potential Soluble nitrogen and FAN Phenol Glycosidic nitrile and ethyl carbamate NDMA Physical characteristics

Question 27

What happens if the moisture content of the malt is too high?

Answer 27

It can not be milled (higher than 7%)

Question 28

Describe the extract quality parameter

Answer 28

The extract of distilling malt is the measure of the total material available from the malt for the yeast during fermentation. The higher the extract from the malt, the higher the specific gravity of the wort produced in the procedure. The malt distiller wants the extract to be as high as possible to maximise the yield in the distillery

Question 29

Describe the friability and homogeneity quality parameters

Answer 29

They're physical measurements that indicate how easily the malt will mill. They also show how evenly the malt has been modified during the malting process.

Question 30

What are the percentages that mean friability and homogeneity are good for whisky production?

Answer 30

Friability greater than 86% and homogeneity greater than 98% indicated the malt is suitable for whisky production. Grain distillers - friability not so critical. 80% is a typical specification for a grain distilling malt

Question 31

Describe fermentability and predicted spirit yield (PSY) quality parameters

Answer 31

A fermentability test determines the percentage of extract that can be fermented by yeast. This is used to calculate the PSY of the malt.

Question 32

What is fermentability?

Answer 32

The percentage of the extract that is fermentable. Extract x fermentability = fermentable extract

Question 33

How do you work out the alcohol yield?

Answer 33

fermentable extract x 6.06 = PSY (LA/t)

Question 34

Describe enzyme potential for quality parameters

Answer 34

The enzyme potential of malt is of great importance to both malt and grain distilleries. Diastatic power (DP), which is a measure of the malts ability to degrade starch. This is a guide to the α-amylase and β-amylase content. Dextrinising units (DU), which is a measure of the α-amylase content of the malt.

Question 35

What are the two main enzymes involved in mashing?

Answer 35

α-amylase and β-amylase

Question 36

Describe soluble nitrogen and FAN

Answer 36

Soluble nitrogen and FAN are both measures of the protein made soluble during the malting process.

Question 37

Describe Phenol quality parameters?

Answer 37

If the malt distillery is producing a peated whisk(e)y, they must be certain the malt they are purchasing is of the correct phenol level. This is an indication of the level of monkey aromas that will carry forwards into the finished spirit.

Question 38

Describe ethyl carbamate

Answer 38

Ethyl carbamate (EC) has been identified as a trace compound in a variety of foods and alcoholic beverages. EC is carcinogenic (cancer causing) so is a major food safety concern for distiller. To control levels of EC in their products, the distilling industry purchases malt made from barley varieties that have a low or null (effectively no) potential to produce these precursors.

Question 39

Describe Glycosidic nitrile

Answer 39

Glycosidic nitrile (GN) is one of the precursors to EC produced by some malting barley varieties. Distillers often specify that non-GN producing varieties are used to make their malt. In addition, they set strict limits on the levels of GN. Below 0.2 g/t is typical.

Question 40

Describe NDMA

Answer 40

NDMA (N-Nitrosodimethylamine) is formed during the kilning of green malt due to the presence of nitrogen oxides. where the nitrogen oxides react with nitrogen-containing compounds in the malt NDMA is a potential carcinogen; therefore, its presence in malt is controlled.

Question 41

describe the physical characteristics quality parameters

Answer 41

Malt distilling - they must be evenly sized so it can be crushed consistently in roller mills. also prefer malt that is delivered with well formed intact husks. Concern - levels of dust and fine material in the malt.

Question 42

Describe a-amylase

Answer 42

Is produced by the aleurone layer - responsible for the breakdown of starch into glucose chains of various sizes

Question 43

Describe B-amylase

Answer 43

Found in the endosperm & activated during germination. Responsible for the breakdown of long glucose chains into maltose.

Question 44

Describe Limit dextrinase

Answer 44

Responsible for the breakdown of branch points in glucose chains

Question 45

Describe B glucanases and pentosanases

Answer 45

Responsible of the breakdown of B-glucan and pentosan in endosperm cell walls

Question 46

Describe proteases

Answer 46

Responsible for the breakdown of the protein matrix in endosperm cell walls

Question 47

Describe the filling facilities for the Saladin box

Answer 47

A conveyor moves steeped grain along the length of the box & spreads stepped grain evenly into multiple piles. The turning machine travels up & out the piles of steeped grain Important that there's an even airflow for the grain bed

Question 48

Describe the emptying facilities on a Saladin box

Answer 48

A horizontal screw on the turning machine transports green malt to a conveyor in the floor of the Saladin box to an elevator on the turning machines that lifts the green malt to a conveyor above the malt bed

Question 49

Describe the filling facilities on a circular vessel

Answer 49

The steeped grain comes down a chute at the centre of the vessel & directed to a horizontal screw attached to the turning machine. This spreads the grain from the centre of the vessel across the floor. The screw then starts to rotate around the germination vessel, spreading more steeped grain as it travels. This continues until the vessels is full.

Question 50

Describe the emptying facilities on a circular vessel

Answer 50

The horizontal screw used to fill the vessel is reversed & used to pull green malt towards the middle of the vessel, where it falls down a chute.

Question 51

What does the perforated floor help with in germination?

Answer 51

Allows air to be forced through the grain as it germinates. This keeps the grain cool and prevents overheating.

Question 52

What are recirculation boxes used for in germination?

Answer 52

to control the proportion of the air that is recirculated

Question 53

Describe turning machines in germination

Answer 53

The turning machine sits across the entire malt bed and consists of multiple vertical helical screws. These rotate pulling the germinating grain from the bottom of the grain bed to the top. moves through the batch every 8-12 hours.