Standards for grain testing (analysts training)

This page hosts guidance and training modules that aim to help improve the standard of grain testing across the UK. It covers equipment, methods and operator standards, as well as targets for testing.

Note: This information is not designed to supersede any appropriate quality systems already in place and is subject to third party audit and accreditation.

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Who should adopt these grain testing standards?

These standards are for all UK laboratories that test grain for trading purposes. Registers of participating laboratories (along with their testing protocols) can be found on the relevant trade association websites.

UK Flour Millers

AIC Trade Assurance Scheme for Combinable Crops (TASCC)

Malting Barley Committee (MBC)

The United Kingdom Accreditation Service (UKAS)

Which tests are covered by the standards?

Ideally, the following tests should be included within proficiency (ring) testing schemes. Laboratories that do not undertake the full range of tests will have a reduced scope.

Test

Wheat

Barley

OSR

Oats

Rye

Peas

Beans

Linseed

Maize

Moisture

X

X

X

X

X

X

X

X

X

Specific weight

X

X

 

X

X

 

 

 

 

Screenings

X

X

 

X

X

 

 

 

 

Admixture

X

X

X

X

X

X

X

X

X

Protein

X

 

 

X

X

 

 

 

 

Nitrogen

 

X

 

 

 

 

 

 

 

Oil

 

 

X

 

 

 

 

X

 

Hagberg falling number

X

 

 

 

X

 

 

 

 

Gluten

X

 

 

 

 

 

 

 

 

Hardness

X

 

 

 

 

 

 

 

 

Germination

 

X

 

 

 

 

 

 

 

Mycotoxins

X

X

 

 

 

 

 

 

 

Erucic acid

 

 

X

 

 

 

 

 

 

Grain testing best practice

Equipment

  1. All testing equipment must be fit for purpose, serviced and maintained in compliance with the laboratory’s quality system and manufacturer’s instructions. Requirements for equipment (e.g. balance accuracy) are given in the test method
  2. Equipment shall be calibrated according to routines within the method and/or against a defined schedule
  3. Performance checks must be done before use. These checks should be performed daily for contractual testing or weekly, as a minimum, for non-contractual testing
  4. When all the above (1–3) have been fulfilled, the equipment is ready for use

Method

  1. The method shall be documented – this can be an official method or an in-house procedure. If the latter is used, the relationship to the official method must be known. Procedures must be in place to ensure that only current methods are used
  2. Is the method accepted by the grain industry? Ensure you only use methods that give results that others recognise, for example the SKCS scale for wheat hardness

Operator

  1. All staff must be competent in those tests that they are expected to undertake
  2. All staff (full-time and temporary) shall be trained in the methods they are required to perform. A record of competence will be held by the laboratory manager and reviewed regularly. Preferably, staff will have undertaken the necessary laboratory training modules
  3. All staff must ensure that any instrument of test performance checks are completed before routine testing starts. These checks should be performed daily for contractual testing or weekly, as a minimum, for non-contractual testing

Sample, testing and reporting

  1. Only when all the above elements have been fulfilled can the testing start. Ensure that the test sample is representative of the sample provided to the laboratory (either in bag or from the laboratory-taken sample). Rules about sub-sampling, grinding and mixing must be followed
  2. Undertake the test according to the documented method. Observe all the critical control points
  3. Results shall be reported in a format agreed with the customer. All results shall be reported with units of measurement recognised by the grain industry

Standard values for grain testing

The measures of the proficiency of a laboratory are given as the limits of variation that are acceptable for repeat testing by the laboratory. They are also given as limits of deviation from defined mean/median values or reference values, when participating in proficiency (ring) test (PT) schemes and limits of variation for use with Internal Quality Control (IQC) checks. Limits of variation for staff competency are also provided. These values have been derived from a large pool of actual testing data.

Standard values: terminology and derivation

  1. Repeatability – permitted difference between two results on the same sample conducted by the same person on the same instrument (within a short timeframe)
  2. Reproducibility – permitted difference between two results on the same sample from different testing facilities
  3. Standard Deviation (SD) for Proficiency Testing Schemes (PT) – maximum permitted value to be used to calculate z-scores. Providers are encouraged to use lower values for SD, if participants are regularly achieving better performance than the standard set by these values
  4. Standard Deviation (SD) for Internal Quality Control (IQC) – maximum suggested value to be used to calculate monitoring (±1SD), warning (±2SD) and action limits (±3SD) for IQC sample
  5. Staff competency – dependent on methodology, a combination of repeatability (‘r’ – column 1) and reproducibility (‘R’ column 2) values for the test are used. Reproducibility can be checked by labs being members of a proficiency (ring) check scheme. There are two main steps for checking staff competency:
    1. Repeatability – repeat-testing one sample a minimum of five times, ensuring all results fall within the repeatability value
    2. Competency – testing a minimum of five samples, representing a range of values, and comparing the results obtained with those of a trained operator/established value for the sample. Difference between results should not exceed the competency figure (column 5)

How to calculate and interpret the z-score

z-score =          (lab value – mean value)

                            standard deviation

Regardless of the sign (+/-):

  • |Z| ≤ 2: performance is satisfactory
  • 2 < |Z| ≤ 3: is a warning (occurs 1 in 20) and suggests attention to equipment or procedures may be required
  • |Z| > 3: requires immediate action and attention to equipment, procedure or operator

Standard values for commodities

Figures for a variety of tests across a wide range of commodities are presented in the tables. These are based on proficiency testing schemes data provided by end-users where significant amounts of data, often a year’s worth, was available. Reference has also been made to standard deviation data published in IOB, EBC, CCAT, BSI and ISO standards. For some tests, compromises have had to be made. These are based on the knowledge and experience of members of the Grain Sampling and Analysis Laboratory Working Party. This reflects the fact that the data available from different sources covered different ranges of test results.

Wheat

 

Test (wheat)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.20

0.36

0.20

N/A

0.36

NIR

0.2

0.4

0.20

0.1

0.2

Meter

0.3

0.5

0.30

0.15

0.3

Specific weight

 

 

 

 

 

Kern

0.40

0.90

0.40

0.20

0.70

Other

0.5

1.5

0.70

0.25

0.5

Screenings

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Hagberg falling number

See Table 4

See Table 4

See Table 4

See Table 4

See Table 4

Gluten

1.1

2.8

1.0

0.5

2.0

Hardness

 

 

 

 

 

SKCS

3.1

6.7

2.4

1.6

3.1

Protein

 

 

 

 

 

Dumas

0.25

0.40

0.14

0.125

0.35

NIR (Transmission)

0.25

0.48

0.20

0.125

0.25

NIR (Reflectance)

0.30

0.60

0.20

0.15

0.50

Admixture

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Mycotoxins

No current data available

Barley

 

Test (barley)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.20

0.45

0.20

N/A

0.45

NIR

0.2

0.4

0.20

0.1

0.2

Meter

0.3

0.5

0.30

0.15

0.3

Specific weight

 

 

 

 

 

Kern

0.40

0.90

0.40

0.20

0.70

Other

0.6

1.5

0.70

0.3

0.6

Screenings

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Nitrogen

 

 

 

 

 

Dumas

0.05

0.09

0.03

0.025

0.07

NIR (Transmission)

0.05

0.09

0.05

0.025

0.05

NIR (Reflectance)

0.05

0.11

0.05

0.025

0.09

Germination capacity

 

 

 

 

 

Rapid

See Table 5

See Table 5

See Table 5

N/A

See Table 5

Peroxide

See Table 5

See Table 5

See Table 5

N/A

See Table 5

Energy (BRF)

See Table 6

See Table 6

See Table 6

N/A

See Table 6

Admixture

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Mycotoxins

No current data available

Oilseed rape

 

Test (oilseed rape)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.20

0.40

0.20

N/A

0.40

NIR

0.3

0.5

0.30

0.15

0.3

Meter

0.3

0.5

0.30

0.15

0.3

Admixture

 

 

 

 

 

Reference method

See Table 2

See Table 2

See Table 2

N/A

See Table 2

Mechanical method

See Table 2

See Table 2

See Table 2

N/A

See Table 2

Manual method

See Table 2

See Table 2

See Table 2

N/A

See Table 2

Oil content

 

 

 

 

 

Extraction

0.27

1.54

0.54

N/A

1.54

NMR

0.6

1.5

0.53

0.3

0.6

NIR

0.6

1.2

0.50

0.3

0.6

 Erucic acid (NIR)

See Table 8

See Table 8

See Table 8

See Table 8

See Table 8

Oats

 

Test (oats)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.32

0.54

0.20

N/A

0.54

NIR

0.2

0.4

0.20

0.15

0.2

Meter

0.3

0.5

0.30

0.15

0.3

Bulk Density

 

 

 

 

 

Kern

0.50

1.80

1.0

0.25

1.10

Other

0.9

1.9

1.0

0.45

0.9

Screenings

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Admixture

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Protein

 

 

 

 

 

Dumas

0.35

0.71

0.25

0.15

0.54

NIR (Transmission)

0.51

0.57

0.25

0.25

0.51

Rye

 

Test (rye)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.20

0.36

0.20

N/A

0.36

NIR

0.2

0.4

0.20

0.1

0.2

Meter

0.3

0.5

0.30

0.15

0.3

Bulk Density

 

 

 

 

 

Kern

0.40

0.90

0.40

0.20

0.70

Other

0.5

1.5

0.70

0.25

0.5

Falling number

See Table 4

See Table 4

See Table 4

See Table 4

See Table 4

Protein

 

 

 

 

 

Dumas

0.25

0.40

0.14

0.125

0.35

NIR (Transmission)

0.25

0.48

0.20

0.125

0.25

NIR (Reflectance)

0.30

0.60

0.20

0.15

0.50

Screenings

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Admixture

See Table 1

See Table 1

See Table 1

N/A

See Table 1

Peas

 

Test (peas)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.30

0.50

0.20

N/A

0.50

Rapid

0.3

0.8

0.30

0.15

0.3

Waste (and Admixture)

See Table 3

See Table 3

See Table 3

N/A

See Table 3

Cracked seed coats

See Table 3

See Table 3

See Table 3

N/A

See Table 3

Soak test

See Table 5

See Table 5

See Table 5

N/A

See Table 5

Beans

 

Test (beans)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.30

0.50

0.20

N/A

0.50

Rapid

0.3

0.8

0.30

0.15

0.3

Admixture

See Table 3

See Table 3

See Table 3

N/A

See Table 3

Staining and Colour

See Table 7

See Table 7

See Table 7

See Table 7

See Table 7

Insect

See Table 7

See Table 7

See Table 7

See Table 7

See Table 7

Linseed

 

Test (linseed)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.20

0.40

0.20

N/A

0.40

Rapid

0.3

0.5

0.30

0.15

0.3

Admixture

See Table 2

See Table 2

See Table 2

N/A

See Table 2

Oil content

 

 

 

 

 

Extraction

0.27

1.54

0.54

N/A

1.54

Other

0.6

1.5

0.54

0.3

0.6

Maize

 

Test (maize)

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

Moisture

 

 

 

 

 

Oven

0.30

0.60

0.20

N/A

0.60

Rapid

0.3

0.8

0.3

0.15

0.3

Admixture

See Table 3

See Table 3

See Table 3

N/A

See Table 3

Balance checks

Balances are checked with known value weights in the critical range, upper and lower action lines are set using the figures in the table below.

 

Number of decimal places (dp) of balance

 

Maximum tolerance for the check weight

1 dp (0.1g)

+/- 0.3g

2 dp (0.01g)

+/- 0.03g

3 dp (0.001g)

+/- 0.003g

4 dp (0.0001g)

+/- 0.0003g

Dispenser checks

Dispensers are checked by weighing the volume of dispensed water (based on 1ml = 1g).

 

Number of decimal places of balance (dp)

 

Below weights are based on a tolerance of 5%

100 µl

0.1g +/- 0.005g

200 µl

0.2g +/-0.01g

300 µl

0.3g +/- 0.015g

400 µl

0.4g +/- 0.02g

500 µl

0.5g +/-0.025g

600 µl

0.6g +/-0.03g

700 µl

0.7g +/- 0.035g

1 ml

1g +/-0.05g

For dispensers used with 70% methanol

10 ml (70% Methanol)

8.72g +/-0.44g

For dispensers used with Hagberg falling number apparatus

25 ml

25g +/- 0.20g

Table 1. Wheat, barley, oats, rye screenings and admixture

Includes skinned barley and broken grains.

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

0.0 to 1.0

99.0 to 100

0.4

0.7

0.25

N/A

0.7

1.1 to 2.0

98.0 to 98.9

0.7

1.4

0.50

N/A

1.4

2.1 to 5.0

95.0 to 97.9

1.1

2.1

0.75

N/A

2.1

5.1 to 10.0

90.0 to 94.9

1.4

2.8

1.0

N/A

2.8

10.1 to 20.0

80.0 to 89.9

2.1

4.2

1.5

N/A

4.2

20.1 to 30.0

70.0 to 79.9

3.5

7.1

2.5

N/A

7.1

30.1 to 50.0

50.0 to 69.9

7.1

14.2

5.0

N/A

14.2

Table 2. Oilseeds admixture

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

0.0 to 0.5

0.2

0.4

0.14

N/A

0.4

0.6 to 1.0

0.4

0.8

0.28

N/A

0.8

1.1 to 2.0

0.6

1.8

0.64

N/A

1.8

2.1 to 3.0

0.8

2.4

0.85

N/A

2.4

3.1 to 4.0

1.0

3.0

1.06

N/A

3.0

4.1 to 5.0

1.2

3.6

1.27

N/A

3.6

5.1 to 6.0

1.4

4.2

1.48

N/A

4.2

Over 6.0

1.6

4.8

1.70

N/A

4.8

Table 3. Pea, bean and maize admixture

Includes pea insect damage and cracked seed coats.

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

0.0 to 1.0

99.0 to 100

0.4

1.4

0.50

N/A

1.4

1.1 to 2.0

98.0 to 98.9

0.7

2.1

0.75

N/A

2.1

2.1 to 3.5

96.5 to 97.9

1.1

3.5

1.25

N/A

3.5

3.6 to 5.0

95.0 to 96.4

1.4

4.2

1.50

N/A

4.2

5.1 to 10.0

90.0 to 94.9

2.1

5.0

1.75

N/A

5.0

10.1 to 20.0

80.0 to 89.9

3.5

7.1

2.50

N/A

7.1

20.1 to 30.0

70.0 to 79.9

5.3

10.6

3.75

N/A

10.6

30.1 to 50.0

50.0 to 69.9

7.1

14.2

5.00

N/A

14.2

Table 4. Hagberg falling number

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

60 to 79

10

10

3.5

5

10

80 to 109

13

21

7.4

7

17

110 to 139

15

30

10.6

8

23

140 to 169

17

38

13.4

9

28

170 to 199

19

46

16.3

10

33

200 to 229

21

54

19.1

11

38

230 to 259

23

62

21.9

12

43

260 to 289

25

70

24.7

13

48

290 to 319

27

78

27.6

14

53

320 to 349

30

86

30.4

15

58

350 to 379

32

94

33.2

16

63

Over 379

40

100

35.3

20

70

Table 5. Barley germinative capacity – peroxide and rapid

Includes pea soak test

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

100

1

2

0.6

N/A

2

99

1

2

0.8

N/A

2

98

2

3

1.0

N/A

3

97

2

3

1.1

N/A

3

96

3

4

1.3

N/A

4

95

3

4

1.5

N/A

4

94

4

5

1.7

N/A

5

93

5

5

1.9

N/A

5

92

5

6

2.0

N/A

6

91

6

6

2.2

N/A

6

90

7

7

2.4

N/A

7

89

7

7

2.6

N/A

7

88

8

8

2.7

N/A

8

87

9

9

2.9

N/A

9

86

9

9

3.1

N/A

9

Table 6. Barley germinative energy – BRF

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

100

3

3

1.1

N/A

3

99

3

3

1.1

N/A

3

98

4

4

1.4

N/A

4

97

4

5

1.8

N/A

5

96

5

6

2.1

N/A

6

95

5

7

2.5

N/A

7

94

6

7

2.5

N/A

7

93

6

8

2.8

N/A

8

92

6

8

2.8

N/A

8

91

7

9

3.2

N/A

9

90

7

9

3.2

N/A

9

89

7

10

3.5

N/A

10

88

8

10

3.5

N/A

10

87

8

11

3.9

N/A

11

86

8

11

3.9

N/A

11

Table 7. Beans – Staining/colour and insect test

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

1

1

2

0.6

N/A

2

2

1

2

0.8

N/A

2

3

2

3

1.0

N/A

3

4

2

3

1.1

N/A

3

5

3

4

1.3

N/A

4

6

3

4

1.5

N/A

4

7

4

5

1.7

N/A

5

8

5

5

1.9

N/A

5

9

5

6

2.0

N/A

6

10

6

6

2.2

N/A

6

11

7

7

2.4

N/A

7

12

7

 7

2.6

N/A

7

13

8

 8

2.7

N/A

8

14

9

 9

2.9

N/A

9

≥15

9

 9

3.1

N/A

9

Table 8. Oilseed rape – Erucic acid (NIR)

 

Result range

1

Repeatability (r)

2

Reproducibility (R)

3

SD for PT

4

SD for IQC

5

Competency

0.00 - 1.00

1.0

2.0

0.7

0.4

1.0

1.01 - 3.00

1.5

2.5

0.9

0.5

1.5

3.01 - 6.00

2.0

3.0

1.2

0.7

2.0

>6.01

3.0

4.5

1.6

1.0

3.0

×