DIN 10483-2-2002 Determination of lactoperoxidase activity in milk - Part 2 Reflectometric method《牛奶乳过氧化物酶活性测定 第2部分 反射计法》.pdf
《DIN 10483-2-2002 Determination of lactoperoxidase activity in milk - Part 2 Reflectometric method《牛奶乳过氧化物酶活性测定 第2部分 反射计法》.pdf》由会员分享,可在线阅读,更多相关《DIN 10483-2-2002 Determination of lactoperoxidase activity in milk - Part 2 Reflectometric method《牛奶乳过氧化物酶活性测定 第2部分 反射计法》.pdf(3页珍藏版)》请在麦多课文档分享上搜索。
1、Ref. No. DIN 10483-2 : 2002-08English price group 06 Sales No. 010610.03DEUTSCHE NORM August 200210483-2Continued on pages 2 and 3. No part of this translation may be reproduced without the prior permission ofDIN Deutsches Institut fr Normung e.V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,ha
2、s the exclusive right of sale for German Standards (DIN-Normen).Determining the lactoperoxidase activity in milkby reflectance spectroscopyTranslation by DIN-Sprachendienst.In case of doubt, the German-language original should be consulted as the authoritative text.ICS 67.100.10Bestimmung der Laktop
3、eroxidase-Aktivitt in Milch Teil 2: Reflektometrisches VerfahrenForewordThis standard has been prepared by Technical Committee Chemische und physikalische Milchuntersuchungof the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Foodstuffs and Agricultural Prod-ucts Standards Committee)
4、.1 ScopeThe method specified in this standard serves to determine the lactoperoxidase activity in raw milk, milk forretail and reconstituted milk by reflectance spectroscopy using test strips. On the basis of the reproducibilitystandard deviation in the low-activity range, the limit of detection can
5、 be put at 6 units per litre.2 Normative referencesThis standard incorporates, by dated or undated reference, provisions from other publications. These nor-mative references are cited at the appropriate places in the text, and the titles of the publications are listedbelow. For dated references, sub
6、sequent amendments to or revisions of any of these publications apply tothis standard only when incorporated in it by amendment or revision. For undated references, the latestedition of the publication referred to applies.DIN 10483-1 Determining the lactoperoxidase activity in milk by photometry (re
7、ference method)DIN 12690 Class A and Class B one-mark bulb pipettes for laboratory useDIN EN ISO 707 Milk and milk products Guidance on sampling (ISO 707 : 1997)ISO 5725-1 : 1994 Accuracy (trueness and precision) of measurement methods and results Part 1: Gen-eral principles and definitionsISO 5725-
8、2 : 1994 Accuracy (trueness and precision) of measurement methods and results Part 2: Basicmethod for the determination of repeatability and reproducibility of a standard measure-ment method3 ConceptSee DIN 10483-1.4 PrincipleA test strip containing 3,3,5,5-tetramethylbenzidine (TMB) as substrate is
9、 immersed in milk diluted withwater. In the presence of hydrogen peroxide, the catalytic action of the lactoperoxidase converts thesubstrate into a coloured compound, the reaction being as follows:Page 2DIN 10483-2 : 2002-082TMB + H2O2+ 2H+ idaselactoperox2TMB+ 2 H2O (1)The amount of oxidized substr
10、ate liberated is proportional to the lactoperoxidase activity and can be measuredreflectometrically at a suitable wavelength (e.g. in the 650 nm to 660 nm range).NOTE: The hue may also be established visually using a colour index.5 Reagents5.1 GeneralAnalytical grade reagents shall be used and the w
11、ater used shall be distilled or at least of equivalent purity.The following reagents shall be used.5.2 Test strips, consisting of an elongated plastic base layer to which absorbent material (e.g. paper) con-taining the TMB substrate has been attached in a suitable way (e.g. by gluing).NOTE: Test str
12、ips with TMB as substrate are commercially available.1)5.3 Hydrogen peroxide solution, prepared by pipetting 1 ml of 30 % (m/m) hydrogen peroxide into a 100 mlvolumetric flask and making up to the mark with water.CAUTION. Hydrogen peroxide is caustic and contact with metals or readily flammable orga
13、nic sub-stances shall be avoided since explosive mixtures may be produced.5.4 Peroxidase-free UHT2) milk, for use as a diluent in preparing calibration samples as specified in theappendix of DIN 10483-1, August 2002 edition.6 ApparatusIn addition to standard laboratory equipment, the following shall
14、 be used.6.1 Reflectometer, for measuring diffuse reflection at a suitable wavelength (e.g. in the 650 nm to 660 nmrange), equipped with a device for analysing test strips.1)6.2 Pipettes, of nominal capacities 5 ml and 20 ml (e.g. pipettes as in DIN 12690).7 SamplingSee DIN EN ISO 707.8 ProcedureNOT
15、E: The calibration specified in subclause 8.2 will generally not be necessary in the case of commerciallyavailable test systems and, in addition, their use simplifies the evaluation as in clause 9.8.1 Sample dilutionMilk samples that have been refrigerated shall be heated to ambient temperature and
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