1、BS EN ISO660:2009ICS 67.200.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDAnimal and vegetablefats and oils Determination of acidvalue and acidity (ISO660:2009)This British Standardwas published under theauthority of the StandardsPolicy and StrategyCommittee
2、 on 31 July2009. BSI 2009ISBN 978 0 580 62712 5Amendments/corrigenda issued since publicationDate CommentsBS EN ISO 660:2009National forewordThis British Standard is the UK implementation of EN ISO 660:2009. It supersedes BS EN ISO660:2000 which is withdrawn.The UK participation in its preparation w
3、as entrusted to TechnicalCommittee AW/307, Oil seeds, animal and vegetable fats and oils andtheir by products.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users
4、 are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 660June 2009ICS 67.200.10 Supersedes EN ISO 660:1999 English VersionAnimal and vegetable fats and oils - Determination of
5、 acid valueand acidity (ISO 660:2009)Corps gras dorigines animale et vgtale - Dterminationde lindice dacide et de lacidit (ISO 660:2009)Tierische und pflanzliche Fette und le - Bestimmung derSurezahl und der Aziditt (ISO 660:2009)This European Standard was approved by CEN on 20 May 2009.CEN members
6、are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to
7、the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same
8、status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania
9、, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: Avenue Marnix 17, B-1000 Brussels 2009 CEN All rights of exploitation in any form and by any means reservedworldwid
10、e for CEN national Members.Ref. No. EN ISO 660:2009: EBS EN ISO 660:2009EN ISO 660:2009 (E) 3 Foreword This document (EN ISO 660:2009) has been prepared by Technical Committee ISO/TC 34 “Food products“ in collaboration with Technical Committee CEN/TC 307 “Oilseeds, vegetable and animal fats and oils
11、 and their by-products - Methods of sampling and analysis“, 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 December 2009, and conflicting national stand
12、ards shall be withdrawn at the latest by December 2009. 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. This document supersedes EN IS
13、O 660:1999. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Irel
14、and, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 660:2009 has been approved by CEN as a EN ISO 660:2009 without any modification. BS EN ISO 660:2
15、009ISO 660:2009(E) ISO 2009 All rights reserved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Eac
16、h member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the Internation
17、al Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standard
18、s adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject o
19、f patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 660 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 11, Animal and vegetable fats and oils. This third edition cancels and replaces the second edition (ISO 660:1996), w
20、hich has been technically revised. It also incorporates the Amendment ISO 660:1996/Amd.1:2003. BS EN ISO 660:2009BS EN ISO 660:2009INTERNATIONAL STANDARD ISO 660:2009(E) ISO 2009 All rights reserved 1Animal and vegetable fats and oils Determination of acid value and acidity 1 Scope This Internationa
21、l Standard specifies three methods (two titrimetric and one potentiometric) for the determination of the acidity in animal and vegetable fats and oils, hereinafter referred to as fats. The acidity is expressed preferably as acid value, or alternatively as acidity calculated conventionally. This Inte
22、rnational Standard is applicable to refined and crude vegetable or animal fats and oils, soap stock fatty acids or technical fatty acids. The methods are not applicable to waxes. Since the methods are completely non-specific, they cannot be used to differentiate between mineral acids, free fatty aci
23、ds, and other organic acids. The acid value, therefore, also includes any mineral acids that may be present. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references,
24、 the latest edition of the referenced document applies. ISO 661, Animal and vegetable fats and oils Preparation of test sample ISO 3696, Water for analytical laboratory use Specification and test methods 3 Terms and definitions For the purposes of this document, the following terms and definitions a
25、pply. 3.1 acid value number of milligrams of potassium hydroxide required to neutralize the free fatty acids present in 1 g of fat, when determined in accordance with the procedure specified in this International Standard NOTE The acid value is expressed in milligrams per gram. 3.2 acidity content o
26、f free fatty acids determined according to the procedure specified in this International Standard NOTE The acidity is expressed as a percentage by mass. If the result of the determination is reported as acidity without further explanation, this is, by convention, the acidity based on the oleic acid
27、content. BS EN ISO 660:2009ISO 660:2009(E) 2 ISO 2009 All rights reserved4 Principle The sample is dissolved in a suitable solvent mixture, and the acids present are titrated with an ethanolic or methanolic solution of potassium or sodium hydroxide. The methods specified in 9.1 and 9.2 are reference
28、 methods. 5 Reagents WARNING Attention is drawn to the regulations which specify the handling of hazardous substances. Technical, organizational and personal safety measures shall be followed. Use only reagents of recognized analytical grade, unless otherwise specified. 5.1 Solvent A for solvent mix
29、ture (5.3): ethanol, volume fraction, 96 %. As a replacement, propan-2-ol, volume fraction, 99 %, can be used. 5.2 Solvent B for solvent mixture (5.3): diethyl ether, peroxide-free. As a replacement, tert-butyl methyl ether, light petroleum (boiling range 40 C to 60 C) or toluene can be used. WARNIN
30、G Diethyl ether is very flammable and may form explosive peroxides. Use with great caution. 5.3 Solvent mixture, mix equal volumes of solvent A and B, (e.g. A= 50 ml/100 ml and B= 50 ml/100 ml). For hard or animal fats, a solvent mixture of one volume of solvent A (e.g. 25 ml) and three volumes of t
31、ert-butyl methyl ether or toluene (e.g. 75 ml) is recommended. Neutralize, just before use, by adding potassium hydroxide solution in the presence of 0,3 ml of the phenolphthalein solution per 100 ml of solvent mixture. For the titration with aqueous KOH, the solvent propan-2-ol can be used. 5.4 Eth
32、anol or methanol, of minimum volume fraction, = 95 %. 5.5 Sodium hydroxide or potassium hydroxide, ethanolic or methanolic standard volumetric solutions, amount of substance concentration c(NaOH) or c(KOH) = 0,1 mol/l and 0,5 mol/l. The concentration shall be checked with a standard volumetric HCl s
33、olution. NOTE The ethanolic/methanolic sodium/potassium hydroxide solution may be replaced by an aqueous sodium/potassium hydroxide solution, but only if the volume of water introduced does not lead to phase separation. 5.6 Phenolphthalein, solution in ethanol, mass concentration, = 1 g/100 ml. 5.7
34、Thymolphthalein, solution in ethanol, mass concentration, = 2 g/100 ml. 5.8 Alkali blue 6B, solution in ethanol, mass concentration, = 2 g/100 ml. For dark-coloured fats, alkali blue or thymolphthalein shall be used. 5.9 Water in accordance with ISO 3696, grade 3. BS EN ISO 660:2009ISO 660:2009(E) I
35、SO 2009 All rights reserved 36 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 Burette, capacity 10 ml, graduated in 0,02 ml, ISO 3851class A. 6.2 Burette, capacity 25 ml, graduated in 0,05 ml, ISO 3851class A. 6.3 Analytical balance, capable of being read to the nearest
36、0,001 g. 6.4 Automatic titration apparatus (based on potentiometric electrode) or potentiometer. 6.5 Combined pH electrode for non-aqueous acid/base titrations. 6.6 Graduated volumetric flasks, volume 1 000 ml, ISO 10422class A. 7 Sampling A representative sample should have been sent to the laborat
37、ory. It should not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in ISO 5555 3. 8 Preparation of test sample Prepare the test sample in accordance with ISO 661, except that
38、 if the sample contains volatile fatty acids, the test sample shall not be heated and filtered. 9 Procedure 9.1 Cold solvent method using indicator (Reference method) 9.1.1 Depending on the expected magnitude of the acid value, select the test portion mass and alkali concentration from Table 1. 9.1.
39、2 According to Table 1 weigh the test portion into a 250 ml conical flask. 9.1.3 Add 50 ml to 100 ml of the neutralized solvent mixture (5.3) and dissolve the test portion if necessary with gentle warming. For high melting point samples, use an ethanol-toluene mixture. 9.1.4 After the addition of an
40、 indicator (5.6, 5.7 or 5.8), titrate with constant swirling using standard potassium hydroxide solution (5.5). The endpoint of the titration is reached when the addition of a single drop of alkali produces a slight but definite colour change persisting for at least 15 s. BS EN ISO 660:2009ISO 660:2
41、009(E) 4 ISO 2009 All rights reservedTable 1 Test portion masses and alkali concentrations Product group (examples) Acid value approx. Mass of test portion Concentration of KOH Accuracy of weighing of the test portion g mol/l g Refined vegetable oils Animal fats 0 to 1 20 0,1 0,05 Crude vegetable oi
42、ls Technical grade animal fats 1 to 4 4 to 15 10 2,5 0,1 0,1 0,02 0,01 Soap stock fatty acids 15 to 75 0,5 3,0 0,1 0,5 0,001 Technical fatty acids 75 0,2 1,0 0,1 0,5 0,001 9.2 Cold solvent method using potentiometric titration (Reference method) 9.2.1 According to Table 1, weigh the test portion int
43、o a 150 ml beaker. 9.2.2 Add 50 ml to 100 ml of the neutralized solvent mixture (5.3) and dissolve the sample, if necessary with gentle warming. For high melting point samples, use an ethanol-toluene mixture. 9.2.3 Introduce the combined electrode in the solvent mixture and connect it with the autom
44、atic titration apparatus. 9.2.4 Start the stirrer for at least 30 s and then titrate with constant swirling using standard potassium hydroxide solution (5.5). 9.2.5 As soon as the equivalence point is reached, record the amount of standard solution used. 9.3 Hot ethanol method using indicator 9.3.1
45、Under the conditions specified in this method, short-chain fatty acids, if present, are volatile. 9.3.2 Weigh into a flask a sufficient mass of the test sample as shown in Table 1, according to the colour and expected acid value. 9.3.3 Heat to boiling 50 ml of the ethanol containing 0,5 ml of the ph
46、enolphthalein indicator in a second flask. While the temperature of the ethanol is still above 70 C, neutralize it carefully with a solution of 0,1 mol/l sodium or potassium hydroxide. The endpoint of the titration is reached when the addition of a single drop of alkali produces a slight but definit
47、e colour change persisting for at least 15 s. Larger volumes of ethanol and indicator may be necessary for dark-coloured fats. Moreover, for dark-coloured fats, alkali blue or thymolphthalein shall be used. 9.3.4 Add the neutralized ethanol to the test portion in the first flask and mix thoroughly.
48、Bring the contents to the boil and titrate with the sodium or potassium hydroxide solution, agitating the flask contents vigorously during the titration. BS EN ISO 660:2009ISO 660:2009(E) ISO 2009 All rights reserved 510 Calculation The acid value, wAV, or the free fatty acid content, wFFA, is repor
49、ted as follows: a) to two decimal places for values between 0 up to and including 1; b) to one decimal place for values between 1 up to and including 100; c) as a whole number for values 100. In addition to the following calculations, the approximate free fatty acid content (acidity) is calculated from: wFFA= 0,5 wAV10.1 Acid value The acid value, wAV, expressed as a mass fraction, is equal to AV56,1 cVwm= where c is the exact concentration, in moles per litre, of the standard volumetric sodium or potas
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