1、BRITISH STANDARD BS EN 12147:1997 Method for Determination of titratable acidity of fruit and vegetable juices The European Standard EN 12147:1996 has the status of a British Standard ICS 67.160.20BSEN12147:1997 This British Standard, having been prepared under the directionof the Consumer Products
2、and Services Sector Board, was published under the authority of the Standards Boardand comes into effect on 15 June 1997 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference AW/21 Draft for comment 91/57094 DC ISBN 0 580 27424 1 Committees responsible for
3、 this British Standard The preparation of this British Standard was entrusted to Technical Committee AW/21, Fruit and vegetable juices, upon which the following bodies were represented: British Fruit Juice Importers Association British Retail Consortium British Soft Drinks Association Limited Campde
4、n and Chorleywood Food Research Association Department of Trade and Industry (Laboratory of the Government Chemist) Leatherhead Food Research Association Ministry of Agriculture, Fisheries and Food Royal Society of Chemistry Amendments issued since publication Amd. No. Date CommentsBSEN12147:1997 BS
5、I 09-1999 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN 12147 3 List of references Inside back coverBSEN12147:1997 ii BSI 09-1999 National foreword This British Standard has been prepared by Technical Committee AW/21, and is the English language
6、 version of EN 12147:1996 Fruit and vegetable juices Determination of titratable acidity, published by the European Committee for Standardization (CEN). EN 12147 was produced as a result of international discussions in which the UnitedKingdom took an active part. ISO 5725:1986, to which informative
7、reference is made in the text, has been superseded by ISO5725-1:1994, ISO5725-2:1994, ISO5725-3:1994, ISO5725-4:1994 and ISO5725-6:1994 which are identical with BSISO5725 Accuracy (trueness and precision) of measurement methods and results, BSISO5725-1:1994 General principles and definitions, BSISO5
8、725-2:1994 Basic method for the determination of repealability and reproducibility of a standard measurement method, BSISO 5725-3:1994, Intermediate measures of the precision of a standard measurement method, BSISO5725-4:1994 Basic method for the determination of the trueness of a standard measureme
9、nt method, and BSISO5725-6:1994 Use in practice of accuracy values. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immuni
10、ty from legal obligations. Cross-references Publication referred to Corresponding British Standard EN ISO 3696:1995 BS EN ISO 3696:1995 Specification for water for laboratory use Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, theEN title page, pages 2
11、to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN12147 December 1996 ICS 67.160.20 Des
12、criptors: Food products, beverages, fruit and vegetable juices, chemical analysis, determination, acidity, titration English version Fruit and vegetable juices Determination of titratable acidity Jus de fruits et de lgumes Dtermination de lacidit titrable Frucht- und Gemsesfte Bestimmung der titrier
13、baren Sure This European Standard was approved by CEN on 1996-05-09. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographic
14、al references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN m
15、ember into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, S
16、weden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1996 Copyright reserved to CEN members Ref. No. EN 12147:1996 EEN12147:1996 BSI 09-1999 2 Foreword
17、This European Standard has been prepared by Technical Committee CEN/TC174, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June1997, and conflicting nati
18、onal standards shall be withdrawn at the latest by June1997. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland
19、, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 Definition and symbol 3 4 Principle 3 5 Reagents 3 6 Apparatus 3 7 Procedure 3 8 Calculation 4 9 Precision 4 10 Test report 4 Annex A (
20、informative) Bibliography 5 Annex B (informative) Statistical results oftheinter-laboratory test 5 Table 1 Factors corresponding to different acids 4 Table B.1 5EN12147:1996 BSI 09-1999 3 1 Scope This European Standard specifies a method for the determination of the titratable acidity of fruit and v
21、egetable juices and related products. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated referenc
22、es, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN ISO 3696:1995, Water for analytical laboratory use Specif
23、ication and test methods. ISO 5725:1986, Precision of test methods Determination of repeatability and reproducibility for a standard test method by inter-laboratory tests. 3 Definition and symbol For the purposes of this standard the following definition applies. 3.1 titratable acidity a measure of
24、the content of mineral and organic acids determined by titration, according to this standard 3.2 Symbol For the purposes of this standard the following symbol applies: c substance concentration. 4 Principle Potentiometric titration with standard volumetric sodium hydroxide solution to a pH value of8
25、,1. 5 Reagents Use only reagents of recognized analytical grade and only degassed water in accordance with at least grade3 of EN ISO 3696:1995. 5.1 Sodium hydroxide, standard volumetric solution, c (NaOH) = 0,25 mol/l. 5.2 Buffer solutions, of suitable pH. 6 Apparatus Usual laboratory apparatus and,
26、 in particular, the following: 6.1 pH meter, accurate to at least 0,01 pH units. 6.2 pH glass electrode 6.3 Reference electrode, e.g. calomel electrode. 6.4 Combination glass electrode, alternatively to6.2 and 6.3. 6.5 Magnetic stirrer 6.6 Burette, 25 ml capacity, graduated in0,05 ml divisions. 6.7
27、Low form beaker (typically 50 ml). 6.8 One-mark pipette, 25 ml capacity. 7 Procedure 7.1 Preparation of the test sample Normally products shall not be pre-treated and their analysis by this method shall be on a volumetric basis, results being expressed per litre of sample. Analysis of concentrated p
28、roducts may also be carried out on a volumetric basis, after dilution to a known relative density. In this case, the relative density shall be indicated. Based on a weighed sample and taking the dilution factor for analysis into account, the results may also be expressed per kilogram of product. In
29、products with a high viscosity and/or a very high content of cells (for example pulp), a determination on the basis of a weighed test sample is the usual procedure. If the sample contains appreciable quantities of carbon dioxide, degas it by shaking in a stoppered conical flask and removing the stop
30、per from time to time, or by using vacuum or ultrasound treatment until no more gas evolves. 7.2 Calibration Perform two-point calibration of the pH meter at20 C using the buffer solution(5.2) with agitation and following the instrument manufacturers instructions. If the pH meter is equipped with a
31、temperature compensation facility, the calibration can be carried out at a temperature other than20 C, but in any case between10 C and30 C.EN12147:1996 4 BSI 09-1999 7.3 Determination Transfer at 20 C, by means of the pipette(6.8),25ml of the test sample (V 0 ) into the beaker(6.7). Start the stirre
32、r(6.5) and titrate by means of the burette(6.6) with sodium hydroxide solution(5.1) until a pH of8,1 is obtained. Record the amount of solution (V 1 ) used. If the pH meter is equipped with a temperature compensation facility, the determination can be carried out at a temperature other than20 C, but
33、 in any case between10 C and30 C. 8 Calculation 8.1 Calculation as titratable acidity The titratable acidity C H+ , expressed in millimoles of H +per litre of product, is given by the formula: where If V 0is 25 ml and c is0,25mol/l, as specified in this European Standard, the titratable acidity C H+
34、 , expressed in millimoles of H +per litre of product, is given by the formula: Report the result without a decimal place. 8.2 Calculation as acid content It is also possible to calculate the titratable acidity conventionally as acid content expressed in grams per litre of product, by multiplying th
35、e formula(8.1) by a factor corresponding to the acid given in Table 1. Table 1 Factors corresponding to different acids Take into account the dilution and the relation of the values to mass or volume. If a concentrated product has been diluted to single strength, report the relative density of the s
36、ingle strength sample. Report the results as tartaric, malic, or anhydrous citric acid, in accordance with the regulations in force in the country concerned, to one decimal place. 9 Precision Details of the inter-laboratory test on the precision of the method are given inAnnex B. The values derived
37、from the inter-laboratory test may not be applicable to analyte concentration ranges and matrices other than those given inAnnex B. 9.1 Repeatability The absolute difference between two single test results found on identical test material by one operator using the same apparatus within the shortest
38、feasible time interval will exceed the repeatability limit r in not more than5% of the cases. The value is: r = 1,03 mmol H + /l 9.2 Reproducibility The absolute difference between two single test results on identical test material reported by two laboratories will exceed the reproducibility limit R
39、 in not more than5% of the cases. The value is: R = 2,28 mmol H + /l 10 Test report The test report shall contain the following data: all information necessary for the identification of the sample (kind of sample, origin of sample, designation); a reference to this European Standard; the date and ty
40、pe of sampling procedure (if known); the date of receipt; the date of test; the test results and units in which they have been expressed; whether the repeatability of the method has been verified; any particular points observed in the course of the test; any operation not specified in the method or
41、regarded as optional, which might have affected the results. (1) V 0 is the volume, in millilitres, of the test portion (see7.3) (as a rule25ml); V 1 is the volume, in millilitres, of the sodium hydroxide solution (see7.3) used for the determination; c is the exact concentration, in moles per litre,
42、 of the sodium hydroxide solution (5.1). C H+= V 1 10 (2) Acid Factor Tartaric acid 0,075 Malic acid 0,067 Citric acid, anhydrous 0,064 C H+ 1000V 1 c V 0 - =EN12147:1996 BSI 09-1999 5 Annex A (informative) Bibliography Determination of titratable acidity: No. 3, 1991. In: The Collected Analyses of
43、the International Federation of Fruit Juice Producers. Loose-leaf edition, as of 1991. Zug: Swiss Fruit Union. Annex B (informative) Statistical results of the inter-laboratory test In accordance with ISO 5725:1986, the following parameters have been defined in an inter-laboratory test (for literatu
44、re pertaining to the method seeAnnex A). The test was conduced by the Max von Pettenkofer Institute of the Federal Health Office, Food Chemistry Department, Berlin, BRD. Table B.1 Sample types: Year of interlaboratory test: 1993; Number of laboratories: 14; Number of samples: 5. Sample A B C D E Num
45、ber of laboratories retained after eliminating outliers 13 12 13 14 13 Number of outliers (laboratories) 1 2 1 1 Number of accepted results 39 35 39 41 51 Mean value () (mmol H + /l) 72 82 118 153 222 Repeatability standard deviation (s r ) (mmol H + /l) 0,256 0,356 0,231 0,444 0,535 Repeatability r
46、elative standard deviation (RSD r ) (%) 0,4 0,4 0,2 0,3 0,2 Repeatability limit (r) (mmol H + /l) 0,7 1,0 0,7 1,1 1,5 Reproducibility standard deviation (s R ) (mmol H + /l) 0,606 0,838 0,650 0,815 1,162 Reproducibility relative standard deviation (RSD R ) (%) 0,8 1,0 0,6 0,5 0,5 Reproducibility lim
47、it (R) (mmol H + /l) 1,7 2,3 1,8 2,3 3,3 A: apple juice; B: apricot nectar; C: grape juice; D: orange juice; E: grapefruit juice. x6 blankBSEN12147:1997 BSI 09-1999 List of references See national foreword.BS EN 12147:1997 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI i
48、s the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions BritishStandards are updated by amendment or revision. Users of BritishStandards should make sure
49、that they possess the latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this BritishStandard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover. Tel:02089969000. Fax:02089967400. BSI offers members an individual updating service called PLUS which ensures that subs
