Standards for grain testing (analysts training)

The standard
Who should adopt these grain testing standards?
Which tests are covered by the standards?
Grain testing best practice
Standard values for grain testing

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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Standard Values for Testing

The standard

This page describes the elements needed for best laboratory practice for grain testing. It gives straightforward guidance on the requirements for equipment, methods and operators. It is not designed to supersede any quality systems already in place and is subject to third party audit and accreditation. However, it provides a framework for those who do not operate to these standards.

In addition to the framework, the targets for testing are described. These are measures of the proficiency of a laboratory and 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 test schemes and limits of variation for use with Internal Quality Control checks. Limits of variation for staff competency are also provided. These values have been derived from a very large pool of actual testing data. An explanation of terminology and derivation of standard value is given, followed by tables of standard values.

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

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
Equipment shall be calibrated according to routines within the method and/or against a defined schedule
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
When all the above (1–3) have been fulfilled, the equipment is ready for use

Method

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
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

All staff must be competent in those tests that they are expected to undertake
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
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

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
Undertake the test according to the documented method. Observe all the critical control points
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

Repeatability – permitted difference between two results on the same sample conducted by the same person on the same instrument (within a short timeframe)
Reproducibility – permitted difference between two results on the same sample from different testing facilities
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
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
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)

Combinable Crops Analyst Training

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
Specific weight	Other	0.5	1.5	0.70	0.25	0.5
Screenings	N/A	See Table 1	See Table 1	See Table 1	N/A	See Table 1
Hagberg falling number	N/A	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	N/A	See Table 1	See Table 1	See Table 1	N/A	See Table 1
Mycotoxins	N/A	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
Specific weight	Other	0.6	1.5	0.70	0.3	0.6
Screenings	N/A	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	N/A	See table 1	See table 1	See table 1	N/A	See table 1
Mycotoxins	N/A	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)	N/A	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
Bulk Density	Other	0.9	1.9	1.0	0.45	0.9
Screenings	N/A	See Table 1	See Table 1	See Table 1	N/A	See Table 1
Admixture	N/A	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
Protein	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
Bulk Density	Other	0.5	1.5	0.70	0.25	0.5
Falling Number	N/A	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	N/A	See Table 1	See Table 1	See Table 1	N/A	See Table 1
Admixture	N/A	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
Moisture	Rapid	0.3	0.8	0.30	0.15	0.3
Waste (and Admixture)	N/A	See Table 3	See Table 3	See Table 3	N/A	See Table 3
Cracked seed coats	N/A	See Table 3	See Table 3	See Table 3	N/A	See Table 3
Soak test	N/A	See Table 3	See Table 3	See Table 3	N/A	See Table 3

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
Moisture	Rapid	0.3	0.8	0.30	0.15	0.3
Admixture	N/A	See Table 3	See Table 3	See Table 3	N/A	See Table 3
Staining and colour	N/A	See Table 7	See Table 7	See Table 7	See Table 7	See Table 7
Insect	N/A	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
Moisture	Rapid	0.3	0.5	0.30	0.15	0.3
Admixture	N/A	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
Oil Content	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
Moisture	Rapid	0.3	0.8	0.3	0.15	0.3
Admixture	N/A	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).

Volume of dispenser	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

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.

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

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 – 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	7	2.7	N/A	8
14	9	7	2.9	N/A	9
≥15	9	7	3.1	N/A	9