CEN TR 16875-2015 Cereal and cereal products - Technical report of the interlaboratory study for the determination of impurities content in maize (Zea mays L ) and sorghum (Sorghum.pdf

1、BSI Standards PublicationPD CEN/TR 16875:2015Cereal and cereal products Technical report of theinterlaboratory study for thedetermination of impuritiescontent in maize (Zea mays, L.)and sorghum (Sorghum bicolor,L.)PD CEN/TR 16875:2015 PUBLISHED DOCUMENTNational forewordThis Published Document is the

2、 UK implementation of CEN/TR16875:2015.The UK participation in its preparation was entrusted to TechnicalCommittee AW/4, Cereals and pulses.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryp

3、rovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2015. Published by BSI Standards Limited 2015ISBN 978 0 580 89963 8ICS 67.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This Published Document was publis

4、hed under the authority of theStandards Policy and Strategy Committee on 30 September 2015.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dPD CEN/TR 16875:2015TECHNICAL REPORT RAPPORT TECHNIQUE TECHNISCHER BERICHT CEN/TR 16875 September 2015 ICS 67.060 English Version Cerea

5、l and cereal products - Technical report of the interlaboratory study for the determination of impurities content in maize (Zea mays, L.) and sorghum (Sorghum bicolor, L.) Crales et produits craliers - Rapport technique de ltude interlaboratoires pour la dtermination de la teneur en impurets dans le

6、 mas (Zea mays, L.) et le sorgho (Sorghum bicolor, L.) This Technical Report was approved by CEN on 27 July 2015. It has been drawn up by the Technical Committee CEN/TC 338. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia

7、, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDAR

8、DIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2015 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TR 16875:2015 EPD CEN/TR 16875:2015CEN/TR

9、 16875:2015 (E) 2 Contents Page European foreword . 3 Introduction 4 1 Scope 5 2 Normative references 5 3 Design of the study 6 3.1 Conception and organization 6 3.1.1 Method 6 3.1.2 Participants . 6 3.1.3 Design and schedule of the study 6 3.2 Product 6 3.3 Fabrication 6 3.4 Homogeneity and stabili

10、ty . 6 3.5 Form . 6 4 Statistics . 7 4.1 Methodology . 7 4.2 Statistical treatment. 7 5 Results of the interlaboratory study 7 5.1 Validation of the raw results . 7 5.2 Detection of stragglers and outliers . 7 5.3 Stragglers and outliers detections 9 5.4 Statistics 10 5.5 Results 10 Annex A (informa

11、tive) Raw results . 16 A.1 Broken grains 16 A.2 Grains impurities . 17 A.3 Sprouted grains . 18 A.4 Miscellaneous impurities 19 A.5 Total impurities 20 PD CEN/TR 16875:2015CEN/TR 16875:2015 (E) 3 European foreword This document (CEN/TR 16875:2015) has been prepared by Technical Committee CEN/TC 338

12、“Cereal and cereal products”, the secretariat of which is held by AFNOR. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. PD CEN/TR 168

13、75:2015CEN/TR 16875:2015 (E) 4 Introduction The principle of the determination of impurities is to separate all the groups of impurities from the normal basic cereal grains of unimpaired quality by sieving and manual selection out of a subsample and to quantify them. The amount of impurities and its

14、 constituent groups is important for health, cleaning, milling and further processing aspects. For these reasons impurities content is a part of contracts in grain trade and also of the grain intervention system of the EU. At present a European standard for the determination of impurities in maize a

15、nd sorghum (EN 16378) has been developed. An international interlaboratory trial for the determination of impurities in maize and sorghum was accomplished in order to get information on the intra- and interlaboratory variability of the determination of impurities content. The technical report here d

16、escribes the preparation and evaluation of the results of this interlaboratory test. PD CEN/TR 16875:2015CEN/TR 16875:2015 (E) 5 1 Scope The term impurities applies to all components of a grain sample that differ from the normal basic cereal. It includes the following groups: broken grains, other ce

17、reals, grains damaged by pests, grains overheated during drying, sprouted grains, extraneous seeds, unsound grains, extraneous matter and impurities of animal origin. The principle of the determination of impurities content is to separate all the groups of impurities from the normal basic cereal gra

18、ins of unimpaired quality by sieving and manual selection out of a subsample and to quantify them. There are various problems in the determination of impurities: Firstly, the identification of the different groups of impurities depends strongly on the experience and the knowledge of the investigator

19、. Also experienced investigators can differ in their characterization of grains. Finally, one is faced with the fact that grain, even after mixing, is rarely homogenous. In other words, if a sample was divided by a sample divider into a number of portions, the amount of a specific group of impuritie

20、s in each portion could be different, even if absolutely no human or machine error occurred in each determination. These problems will result in variation of the results of the determination. An international interlaboratory test for the determination of impurities, according to this standard and in

21、volving 14 laboratories in 4 countries, was carried out with 5 maize and 3 sorghum samples. It was asked to participants to make determination in duplicate. Ten laboratories reported results for the complete sample set and two only for corns. The test materials ranged between: 0,0 % and 2,7 % for br

22、oken grains; 0,2 % and 3,5 % for grain impurities; 0,0 % and 0,1 % for sprouted grains; 0,5 % and 3,3 % for miscellaneous impurities; 1,8 % and 8,7 % for total impurities. The aim of the study is to determine the precision, repeatability and reproducibility of the method of determination of impuriti

23、es content in maize and sorghum samples. The analyses were realized in March - April 2011. It occurs according to ISO 5725:1994. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated refer

24、ences, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 16378, Cereals - Determination of impurities content in maize (Zea mays, L.) and sorghum (Sorghum bicolor, L.) PD CEN/TR 16875:2015CEN/TR 16875:2015 (E)

25、 6 3 Design of the study 3.1 Conception and organization 3.1.1 General The interlaboratory comparisons of this test were designed according to the wishes of AFNOR and organized by BIPEA. 3.1.2 Method The participants made a commitment to apply strictly the described method and to prepare the samples

26、 according to the method provided with the commitment letter for participating to the test: the standard EN 16378. 3.1.3 Participants Fourteen laboratories made a commitment to participate to the test. Twelve did answer. 3.1.4 Design and schedule of the study Each laboratory received eight samples:

27、5 samples of corn and 3 samples of sorghums, according to a blind distribution. In order to take into account the sampling of the laboratory into the precision values, the laboratories realized two analytical series on two sub-samples from each sample, leading to sixteen determinations of impurities

28、. Tests were conducted between March, 1st and April, 26th, 2011. In order to be as close as possible to repeatability conditions, the two sub-samples analyses has been realized during a time as short as possible. The repeatability variance is an intra-laboratory variance. However, in order to be eas

29、ier to read, it is called repeatability mean in the report. 3.2 Product In order to cover the scope of the method, the products analysed are maize mixes and sorghum mixes. 3.3 Fabrication The samples are produced according to the following procedure: Each batch is homogenized and divided in samples

30、serials. This operation is made with a carousel. The principle of turning spreading, that involves a progressive filling, ensures the homogeneity of the product between each sample. The samples of maize 1, 2 and 4 and the samples of sorgho 1 and 3 were of 500 g in paper bags. The samples of maize 3

31、and 5 and the samples of sorgho 2 were of 1 kg in paper bags. The weights were increased for some samples in order to integer the division step inside the laboratory. 3.4 Homogeneity and stability On this test, no control was planned. However, homogeneity and stability were considered as sufficient

32、by the working group for the test, during its conception. 3.5 Form In addition to final results, expressed in % of impurities, the weights values were requested to the participants. The form sheet template is in A.2. PD CEN/TR 16875:2015CEN/TR 16875:2015 (E) 7 4 Statistics 4.1 Methodology The precis

33、ion parameters were calculated on the two sub-samples of each impurity category according to the following plan. Figure 1 4.2 Statistical treatment The statistical treatment was carried out according to ISO 5725-2. 5 Results of the interlaboratory study 5.1 Validation of the raw results The project

34、leader realized the checks of the calculations of impurities contents from the weight values. A laboratory seems not to have followed the method; it was excluded from the calculations of the precision parameters (laboratory 7568). A laboratory did not write correctly his results, it has a lack of tr

35、aceability of its samples (laboratory 2190). The results of the corn 3 have been reported on the corn 2 form sheets, those of corn 4 on the form sheet for corn 3 and those of corn 2 on the form sheet of corn 4. The traceability and the results have been corrected. 5.2 Detection of stragglers and out

36、liers Stragglers and outliers detection have been realized with statistical tests on the provided results except for the excluded laboratory above: Cochrans test: outliers and stragglers for variances (at 5 % and 1 %); PD CEN/TR 16875:2015CEN/TR 16875:2015 (E) 8 Grubbs test: outliers and stragglers

37、for means (at 5% and 1 %). The principles of the tests and the decision rules are described in ISO 5725-2. The results of those tests are presented in Table A.9 and Table A.10, in A.5. As abstract: For the corn 1: the variance of the laboratory 8577 for miscellaneous impurities has been detected as

38、outlier; the variance of the laboratory 8577 for total impurities has been detected as straggler; the mean of the laboratory 7489 for broken grains has been detected as outlier; the mean of the laboratory 6723 for total impurities has been detected as straggler. For the corn 2: the variance of the l

39、aboratory 5909 for broken grains has been detected as outlier; the mean of the laboratory 7489 for broken grains has been detected as outlier; the mean of the laboratories 6723 and 8577 for miscellaneous impurities has been detected as straggler; For the corn 3: the variance of the laboratories 5909

40、 for miscellaneous impurities and 6723 for total impurities has been detected as outlier; the variance of the laboratory 6637 for sprouted grains has been detected as straggler; the mean of the laboratory 8577 for miscellaneous impurities and for total impurities has been detected as straggler. For

41、the corn 4: the variance of the laboratory 8577 for sprouted grains and for grain impurities has been detected as outlier; the variance of the laboratory 8577 for broken grains and for total impurities has been detected as straggler; the mean of the laboratory 8577 for miscellaneous impurities has b

42、een detected as straggler. For the corn 5: the variance of the laboratory 8577 for broken grains and for miscellaneous impurities has been detected as outlier; the variance of the laboratory 8577 for grain impurities and for total impurities has been detected as straggler; the mean of the laboratory

43、 6723 for grain impurities, for miscellaneous impurities and for total impurities; PD CEN/TR 16875:2015CEN/TR 16875:2015 (E) 9 the mean of laboratory 8577 for miscellaneous impurities has been detected as straggler. For the sorgho 1: the variance of the laboratory 5703 for grain impurities has been

44、detected as outlier; the mean of the laboratory 6723 for grain impurities has been detected as straggler. For the sorgho 2: the variance of the laboratory 7489 for total impurities has been detected as outlie; the variance of the laboratory 7489 for miscellaneous impurities has been detected as stra

45、ggle; the mean of the laboratory 6723 for grain impurities has been detected as straggler. For the sorgho 3: the variance of the laboratory 7489 for miscellaneous impurities and for total impurities has been detected as straggler. The values for which the means are judged as stragglers have been exc

46、luded from the precision parameters calculation for the concerned corns and the sorghum. The values for which the variances are judged as stragglers have been excluded from the precision parameters calculation for the concerned corns and the sorghum. 5.3 Stragglers and outliers detections Table 1 Co

47、chrans test: stragglers (in bold) and outliers for variances Lab numbers Maize 1 Maize 2 Maize 3 Maize 4 Maize 5 Sorghum 1 Sorghum 2 Sorghum 3 Broken grains - 5909 - 8577 8577 - - - Grain impurities - - - 8577 8577 5703 - - Sprouted grains - - 6637 8577 - - - - Miscellaneous impurities 8577 - 5909 -

48、 8577 - 7489 7489 Total impurities 8577 - - 8577 8577 - 7489 7489 Table 2 Grubbs test: stragglers (in bold) and outliers for means Lab numbers Maize 1 Maize 2 Maize 3 Maize 4 Maize 5 Sorghum 1 Sorghum 2 Sorghum 3 Broken grains 7489 7489 Grain impurities 6723 6723 6723 Sprouted grains Miscellaneous i

49、mpurities 6723 8577 8577 8577 6723 8577 Total impurities 6723 6723 8577 6723 PD CEN/TR 16875:2015CEN/TR 16875:2015 (E) 10 5.4 Statistics Analyses of variance (ANOVA) were realized on each sample in order to determine the intra-laboratory (repeatability) and interlaboratory (reproducibility) variabilities. For each sample, from the results the following have been calculated: the mean; repeatability and reproducibility standard deviations; repeatability and reprodu