DIN ISO 9622-2017 Milk and liquid milk products - Guidelines for the application of mid-infrared spectrometry (ISO 9622 2013)《奶和奶制品 中红外光谱应用指南(ISO 9622-2013)》.pdf

1、April 2017 English price group 12No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 67.100.10!%cO(“2644405www.din.deDI

2、N ISO 9622Milk and liquid milk products Guidelines for the application of midinfrared spectrometry (ISO 9622:2013),English translation of DIN ISO 9622:2017-04Milch und flssige Milcherzeugnisse Leitfaden fr die Anwendung der MittelInfrarotSpektroskopie (ISO 9622:2013),Englische bersetzung von DIN ISO

3、 9622:2017-04Lait et produits laitiers liquides Lignes directrices pour lapplication de la spectromtrie dans le moyen infrarouge (ISO 9622:2013),Traduction anglaise de DIN ISO 9622:2017-04SupersedesDIN ISO 9622:200012, withdrawn 201601www.beuth.deDocument comprises 19 pagesDTranslation by DIN-Sprach

4、endienst.In case of doubt, the German-language original shall be considered authoritative.04.17 A comma is used as the decimal marker. Contents PageForeword .41 Scope . 62 Normative references 63 Terms and definitions . 64 Principle 75 Principal characteristics of infrared instruments . 76 Factors a

5、ffecting the measurements 76.1 Instrument factors .76.2 Physico-chemical and biological factors . 107 Calibration of the instrument . 137.1 Objective . 137.2 Spectrum calibration models 137.3 Core settings 147.4 Checking the slope and intercept 148 Sampling .159 Determination 1510 Checking daily sho

6、rt-term stability of the instrument 1510.1 General 1510.2 Preparation and storage of control samples 1510.3 Analysis of control samples. 1610.4 Monitoring the analytical procedure 1610.5 Re-adjustment of instrument settings . 1611 Precision 1711.1 Repeatability 1711.2 Intra-laboratory reproducibilit

7、y .1711.3 Reproducibility 1712 Test report 18Bibliography .19National Annex NA (informative) Bibliography 5DIN ISO 9622:2017-04 2 DIN ISO 9622:2017-04 3 National foreword This standard (DIN ISO 9622:2013) has been prepared by Technical Committee ISO/TC 34 “Food products” (Secretariat: AFNOR, France)

8、, Subcommittee SC 5 “Milk and milk products” (Secretariat: NEN, Netherlands), in collaboration with the International Dairy Federation (IDF). AT the IDF, the international standard has been published under the name IDF 141. The responsible German body involved in its preparation was DIN-Normenaussch

9、uss Lebensmittel und landwirtschaftliche Produkte (DIN Standards Committee Food and Agricultural Products), Working Committee NA 057-05-13 AA “Milk and milk products Methods of sampling and analysis”. Attention is drawn to the possibility that some of the elements of this document may be the subject

10、 of patent rights. DIN and/or DKE shall not be held responsible for identifying any or all such patent rights. The DIN Standards corresponding to the International Standards referred to in this document are as follows: ISO 707 DIN EN ISO 707 ISO 1211 DIN EN ISO 1211 ISO 5725 (all parts) DIN ISO 5725

11、 (all parts) ISO 5764 DIN EN ISO 5764 ISO 8968-1 DIN EN ISO 8968-1 ISO 8968-2 DIN EN ISO 8968-1 ISO 8968-4 DIN EN ISO 8968-4 ISO 8968-5 DIN EN ISO 8968-4 ISO 14637 DIN EN ISO 14637 Note: Since ISO 9622:2013 was published, ISO 8968-1 and ISO 8968-2 have been replaced by a new edition of ISO 8968-1, a

12、nd ISO 8968-4 and ISO 8968-5 have been replaced by a new edition of ISO 8968-4. DIN ISO 9622:2017-04 4 Amendments This standard differs from DIN ISO 9622:2000-12 (withdrawn 2016-01) as follows: a) the text of the standard has been technically revised; b) Clause 1 “Scope” has been rendered more preci

13、se; c) Clause 3 “Terms and definitions” has been revised; d) Clauses 4 and 5 have been presented in more general; e) the measurement of repeatability and zero stability (Subclauses 6.1.1 and 6.1.2) have been included; f) procedures have been partly rendered more precise; g) in Subclause 6.2 “Physio-

14、chemical and biological factors”, Subclauses 6.2.7 “pH” and 6.2.9 “Product-matrix effects” have been included; h) Clause 7 “Calibration of the instrument” has been completely revised; i) the statistical control of the procedures in Subclauses 10.3 and 10.4 (former 11.3 and 11.4) is now described in

15、considerably greater brevity (as it is meanwhile good laboratory practice); j) information on reproducibility (Subclause 11.3) has been included; k) Annex A has been deleted and partly transferred to the normative references; l) the standard has been editorially revised. Previous editions DIN ISO 96

16、22: 2000-12 DIN ISO 9622:2017-04 5 National Annex NA (informative) Bibliography DIN EN ISO 707, Milk and milk products Guidance on sampling DIN EN ISO 1211, Milk Determination of fat content Gravimetric method (Reference method) DIN ISO 5725 (all parts), Accuracy (trueness and precision) of measurem

17、ent methods and results DIN EN ISO 5764, Milk Determination of freezing point Thermistor cryoscope method (Reference method) DIN EN ISO 8968-1, Milk and milk products Determination of nitrogen content Part 1: Kjeldahl principle and crude protein calculation DIN EN ISO 8968-4, Milk and milk products

18、Determination of nitrogen content Part 4: Determination of protein and non-protein nitrogen content and true protein content calculation (Reference method) DIN EN ISO 14637, Milk Determination of urea content Enzymatic method using difference in pH (Reference method) Milk and liquid milk products Gu

19、idelines for the application of mid-infrared spectrometry1 ScopeThis International Standard gives guidelines for the quantitative compositional analysis of milk and liquid milk products, such as raw milk, processed milk, cream and whey, by measurement of the absorption of mid-infrared radiation.Addi

20、tional built-in instrument features, such as a conductivity sensor, can improve the performance in the determination of compositional parameters and allow for the estimation of other parameters.The guidelines specified are applicable to the analysis of cows milk. The guidelines are also applicable t

21、o the analysis of milk of other species (goat, ewe, buffalo, etc.) and derived liquid milk products, provided adequate calibrations are generated for each application and adequate control procedures are in place.The application is limited to lower viscosity products that can be pumped through the fl

22、ow system of the analyser and to analytes that do not result in optical saturation at the specific wavelengths being utilized.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable to its application. For dated references

23、, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 8196|IDF 128 (all parts), Milk Definition and evaluation of the overall accuracy of indirect methods of milk analysisISO 8968-1|IDF 20-1, Milk Determination

24、of nitrogen content Part 1: Kjeldahl methodISO 8968-2|IDF 20-2, Milk Determination of nitrogen content Part 2: Block-digestion method (Macro method)ISO 8968-5|IDF 20-5, Milk Determination of nitrogen content Part 5: Determination of protein-nitrogen contentNOTE Other normative documents can apply de

25、pending on the specific application or calibration of the automated analyser.3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 8196|IDF 128 (all parts), and the following apply.3.1spectral calibrationspectrum calibration modelcalibration based on combin

26、ation of absorbance signals at several (2) wavelengths in the mid-infrared region or signals from other sensors, mathematically optimized to arrive at the best estimate for the parameter of interest3.2slope and intercept calibrationsimple linear regression coefficients as established from a least-sq

27、uares regression of optimized instrument readings against results as obtained with physico-chemical reference methodsDIN ISO 9622:2017-04 6 4 PrincipleAfter pretreatment and homogenization, where required, the sample is measured with an infrared spectrometer that records the quantity of radiation ab

28、sorbed in transmittance at specific wavelengths in the mid-infrared region. The spectral data are transformed into estimates of constituent concentrations or other physico-chemical parameters through calibration models developed on representative samples from the population to be tested. For some pa

29、rameters, i.e. freezing point equivalents, signals from additional installed sensors may be fed to the calibration model.5 Principal characteristics of infrared instrumentsThe signals at the relevant wavelengths may be produced using either a Fourier-transformed interferogram or by using optical fil

30、ters. Instruments and applied calibration models may differ with respect to the number of specific wavelengths used in estimating the parameters of interest.An infrared instrument is a proprietary apparatus which, when used under the conditions defined in this International Standard, provides estima

31、tes of compositional and other parameters in milk and liquid milk products.6 Factors affecting the measurements6.1 Instrument factors6.1.1 RepeatabilityTo check instrument repeatability, analyse a uniform representative sample a minimum of 12 times in succession. The first two replicate results are

32、discarded to minimize carry-over effects. The calculated repeatability should meet with the repeatability limits for the concerned parameter and sample matrix.6.1.2 Zero stabilityTo monitor zero stability, a blank sample (water or zero solution) is analysed periodically during routine use of the ins

33、trument. Drift should be relatively small and random with respect to direction (), such that cumulative drift is minimal. A plot of the zero drift vs time is an effective way to track instrument stability.NOTE Certain instruments are factory set to auto-correct the zero at regular intervals. It is i

34、ntended that operators review these automatic corrections to ensure that cumulative drift is not excessive.6.1.3 HomogenizationTo check the efficiency of the homogenizer, make two consecutive analyses, firstly with an unhomogenized whole milk sample, and secondly with the same whole milk sample afte

35、r it has been homogenized through the instruments homogenizer. When the average of five replicate fat readings is found, the difference among these five replicate fat readings shall not exceed 0,04 % for a milk sample containing a mass fraction of 4,0 % of milk fat. To calculate the appropriate pass

36、/fail criteria for milk fat concentrations other than 4,0 %, multiply the actual fat content by 0,01 to obtain the new criteria.NOTE 1 This procedure is only applicable to instruments in which the homogenized discharge can be isolated and collected.NOTE 2 For applications involving sample matrices w

37、ith higher levels of fat (i.e. raw cream), it is advisable to check homogenization efficiency with a representative high fat sample. Specific parameters for homogenizer performance depend upon the matrix.DIN ISO 9622:2017-04 7 NOTE 3 Instrument readings for every milk fat component (e.g. individual

38、fatty acids or groups of fatty acids) is dependent on the effectiveness of homogenization. Different wavelengths used in calibration models result in unequal sensitivity to homogenizer efficiency and possibly larger relative effects than for fat. When measuring such milk fat components, it is intend

39、ed that the homogenizer efficiency test be performed for these components, and the difference is not intended to exceed the limit of repeatability for the component.CAUTION The results of this test can be misleading, as an instrument in which the homogenizer does not work at all gives very little di

40、fference between the first and the second run.An alternative procedure is to obtain an unhomogenized as well as a homogenized portion of the same milk, either by collecting raw and processed milk from the same tank at a dairy plant or by producing smaller volumes by means of a bench-top or pilot-pla

41、nt homogenizer. Then measure both the unhomogenized and the same homogenized milk and compare the difference in results to the above-mentioned pass/fail criterion.The assumption is that the homogenization efficiency of the external homogenizer is good. That can be verified by particle size analysis

42、of the homogenized milk. A reasonable fat globule size distribution is characterized by a d (0,9) of 1,4 m to 1,5 m d (0,9) means that 90 % of the milk fat globules has a diameter of less than d.17Some instruments allow the user to monitor a homogenization index value to track the performance of the

43、 homogenizer. The manufacturers guidelines should be followed.Monitoring of instrument repeatability can also provide valuable information with respect to the state of the homogenizer. If repeatability on homogenized milk is satisfactory, whereas the repeatability on raw milk is poor (more than twic

44、e the variation), the homogenizer is likely not performing at an acceptable level.6.1.4 LinearityNOTE 1 The linearity check described in this subclause applies only to the measurement of major components in milk. Linearity checks for other applications, particularly for higher fat products or for pa

45、rameters other than the major constituents, will differ. It is intended that the manufacturers guidelines be followed in these cases.NOTE 2 Linearity can be assessed on either a mass/mass basis or a mass/volume basis. Since the instrument cuvette holds a specific volume of sample, it is most ideal t

46、o assess linearity on a mass/volume basis. In either case, linearity solutions are prepared by accurately weighing fractions. To assess linearity on a volume basis, it is intended that accurate density measurements be conducted and appropriate conversions be calculated.NOTE 3 It is critical, prior t

47、o assessing linearity, to confirm that the instrument homogenizer is functioning appropriately (see 6.1.3).To check the linearity for each of the major components, make up at least 10 solutions of known concentration, which cover the typical range for the specific component. The following solutions

48、are recommended.a) Homogenized cream with a mass fraction of fat of 8 %, diluted with skimmed milk or zero solution to check the linearity for the determination of the fat content. If homogenized cream at this fat level is unavailable, unhomogenized cream may also be used providing the instrument homogenizer is functioning at an acceptable level (see 6.1.3).b) UF skimmed milk retentate diluted with ultrafiltrate to check the linearity for the determination of the protein content. Alternatively, whey protein