Lesson 7 - Malt Quality SAQ
This lesson provides the opportunity for you to test yourself on the material covered in Lesson 6 (Malt Quality) and determine the level to which you have attained the expected outcomes.
Suggested Response - Q9
***You receive additional information on Malt B. It is a blend of two pieces, and the results of their analysis using EBC methods are shown in the CoA below. Please answer the following questions:
|
Parameter |
Unit of measure |
Specification |
Malt |
Results |
||
|
IOB |
EBC |
B |
Piece 1 |
Piece 2 |
||
|
Moisture |
% |
4.5-5.5 |
4.5-5.5 |
4.2 |
3.9 |
4.5 |
|
Extract yield (dry wt) |
l°/kg or % |
>305 l˚/kg |
>80.5% |
79.80% |
80.8 |
78.8 |
|
Corn size >2.5mm |
% |
95 |
95 |
96.8 |
96.4 |
97.2 |
|
Colour |
EBC |
2-4 |
2-4 |
4.15 |
4.4 |
3.9 |
|
Total nitrogen |
% |
1.6-1.8 |
1.6-1.8 |
1.64 |
1.62 |
1.66 |
|
Total soluble nitrogen |
% |
0.57-0.66 |
0.65-0.75 |
0.70 |
0.7 |
0.69 |
|
FAN |
mg/l |
>160 |
>160 |
173 |
180 |
166 |
|
SNR |
% |
34-40 |
38-44 |
41 |
44 |
38 |
|
Friability meter reading |
% |
>85 |
>85 |
86.5 |
88 |
85 |
|
Homogeneity |
% |
>96 |
>96 |
96 |
98 |
94 |
|
Diastatic power |
WK |
>65˚ IOB |
>222 WK |
375 |
430 |
320 |
|
Wort viscosity |
mPas @ 20˚C |
1.55-1.65 |
1.55-1.65 |
1.52 |
1.48 |
1.56 |
|
DMS-p |
mg/kg |
2-8 |
2-8 |
2.65 |
2.65 |
2.65 |
|
Beta glucan |
mg/l |
<200 |
<250 |
150 |
100 |
200 |
|
Additional information |
|
|
|
|
|
|
|
Acrospire 0-1/4 |
% |
|
|
1 |
1 |
1 |
|
Acrospire 1/4-1/2 |
% |
|
|
5 |
0 |
10 |
|
Acrospire 1/2-3/4 |
% |
|
|
4 |
4 |
4 |
|
Acrospire 3/4-1 |
% |
|
|
86 |
91 |
81 |
|
Acrospire >1 |
% |
|
|
4 |
4 |
4 |
|
NDMA ppb |
ppb |
|
|
0.5 |
0.5 |
0.5 |
|
*Aflatoxin B1, B2, G1 & G2, ppb |
ppb |
|
|
0 |
0 |
0 |
|
Foreign Seeds |
% |
|
|
0 |
0 |
0 |
(a) Critically evaluate Piece 2.
(b) Would you purchase Malt B for your brewery? Explain why.
Response
(a)
To critically evaluate piece 2, we can use the CoA to help us.
Parameters determined by barley:
Nitrogen - It is within specification, but on the low side. This may produce lower amylase levels during malting. A check of the DP, however, shows this to be sufficient.
Extract yield - this is also determined by genetics. Unless over-modified, the malt blend and its pieces will typically be below 80% on a dry basis. The extract yield is lower compared to Malt A, showing that some of the extract is not available for conversion.
Kernel size - the environment will influence kernel size during growth. A kernel size greater than 95% indicates symmetrical kernels.
Physical tests
Moisture is within specification, but higher than Malt A.
The colour is within specification.
There is no turbidity on this CoA.
Modification
Soluble nitrogen ratio – In the EBC analysis this is KI; a result of 38 is near to the lower limit.
The ratio is within specification, but near to the lower limit. This indicates that less modification has taken place than with Piece 1.
Friability
Low, but within specification. The result suggests that some of the kernels did not modify either evenly or completely.
Homogeneity
A low, out of specification homogeneity result leads to high PUGs (partially under-modified grains) and WUGs (wholly under-modified grains). This result again shows that some of the kernels were under-modified.
β-Glucan levels
Although the β-glucan result is higher compared to Piece 1, it is well within specification for the EBC, < 250 mg/L. However, it is under-modified; there will be residual cell wall material present in the malt. There is a risk of haze formation later in the process.
Wort viscosity
The wort viscosity result is higher than with Piece 1 and Malt A. This is because of the high β-glucan level. This can significantly increase the run-off time during wort separation.
Acrospires
One percent of the blend is between 0-1/4. The grains are either slow to grow, or dead. 10% of the bed is between 1/4 and 1/2. In total, 11% of the bed is slow, or dead, in terms of modification. One percent of the bed is > 1, indicating there is also a difference in terms of the barley’s growing capacity. This part of the bed will be over-modified.
Protein and Enzyme activity
Soluble nitrogen - the total nitrogen will not change, but the soluble nitrogen increases as modification progresses. The soluble nitrogen is within specification.
FAN - the FAN result is within specification, but on the lower side. This also indicates under-modified malt.
DP - 320 WK is lower than Piece 1, but this level is still acceptable.
Other tests including visual assessment
SMM - SMM is the main precursor to DMS in malt. The results here show no potential issues.
Viscosity - The viscosity results should not create problems within the brewhouse.
Food safety elements
There are no food safety concerns, as the Aflatoxin and the poisonous seed level is zero. NDMA is also within safe limits.
(b)
When purchasing malt, it needs to satisfy the following requirements:
- High extract recovery
- Ease of milling
- Ease of extract recovery
- Low viscosity wort
- The required balance of nitrogenous compounds
- Wort clarity
- Wort of the desired colour
- Ideal malty taste and no off-flavours
The only parameter that is out of specification is the colour. This can lead to brewhouse colour control issues. On paper, Malt B looks like a good malt to purchase. Looking at the piece results, nothing relating to Piece 2 is out of specification, but it is under-modified. Due to this, there will likely be extract loss. This is because some of the starch granules are still inside the cell wall material and protein matrix. However, overall it would still be a good malt to purchase.
This sample is a typical example of how two pieces are blended together to ensure that the malt blend meets specification.