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1、 Reference number ISO 3961:2009(E) ISO 2009 INTERNATIONAL STANDARD ISO 3961 Fourth edition 2009-04-01 Animal and vegetable fats and oils Determination of iodine value Corps gras dorigines animale et vgtale Dtermination de lindice diode Copyright International Organization for Standardization Provide
2、d by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 3961:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, th
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6、n may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20
7、Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2009 All rights reserved Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 0
8、3:07:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 3961:2009(E) ISO 2009 All rights reserved iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Inte
9、rnational Standards is normally carried out through ISO technical committees. Each 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 wi
10、th ISO, also take part in the work. ISO collaborates closely with the International 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 technic
11、al committees is to prepare International Standards. Draft International Standards 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 t
12、o the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 3961 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 11, Animal and vegetable fats and
13、oils. This fourth edition cancels and replaces the third edition (ISO 3961:1996), which has been technically revised. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo reproducti
14、on or networking permitted without license from IHS -,-,- Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo reproduction or networking permitted without license from IHS -,-,- IN
15、TERNATIONAL STANDARD ISO 3961:2009(E) ISO 2009 All rights reserved 1 Animal and vegetable fats and oils Determination of iodine value 1 Scope This International Standard specifies a reference method for the determination of the iodine value (IV) of animal and vegetable fats and oils, hereinafter ref
16、erred to as fats. Annex A describes a method for the calculation of the IV from fatty acid compositional data. This method is not applicable to fish oils. NOTE The method in Annex A is based upon the AOCS Recommended Practice Cd 1c-854. 2 Normative references The following referenced documents are i
17、ndispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 661, Animal and vegetable fats and oils Preparation of test sample ISO 3696, Water fo
18、r analytical laboratory use Specification and test methods 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 iodine value IV wI mass of halogen, expressed as iodine, absorbed by the test portion following the specified procedure, divided by the
19、 mass of the test portion NOTE The IV is expressed as grams per 100 g of fat. 4 Principle Dissolution of a test portion in solvent and addition of Wijs reagent. After a specified time, addition of potassium iodide and water, and titration of the liberated iodine with sodium thiosulfate solution. NOT
20、E Annex A describes a method for the calculation of the IV from fatty acid compositional data. However, this is not intended to be a rapid method. The method gives two results from one analytical procedure. The volumetric method is the reference method. Copyright International Organization for Stand
21、ardization Provided by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 3961:2009(E) 2 ISO 2009 All rights reserved 5 Reagents Use only reagents of recognized analytical grad
22、e, and water in accordance with ISO 3696, grade 3. WARNING Attention is drawn to the regulations which specify the handling of hazardous substances. Technical, organizational and personal safety measures shall be followed. 5.1 Potassium iodide, solution, mass concentration, (KI) = 100 g/l, not conta
23、ining iodate or free iodine. 5.2 Starch solution: Mix 5 g of soluble starch in 30 ml of water and add to 1 000 ml of boiling water. Boil for 3 min and allow to cool. Prepare fresh starch solution every day. 5.3 Sodium thiosulfate, standard volumetric solution, amount of substance concentration c(Na2
24、S2O35H2O) = 0,1 mol/l, standardized not more than 7 days before use. 5.4 Solvent, prepared by mixing one volume of cyclohexane and one volume of glacial acetic acid (50 ml + 50 ml). 5.5 Wijs reagent, containing iodine monochloride in acetic acid. The I/Cl ratio of the Wijs reagent shall be within th
25、e limits 1,10 0,1. Commercially available Wijs reagent shall be used. Any shelf-life limitation of the reagent shall be observed. 6 Apparatus Usual laboratory apparatus and, in particular, the following. 6.1 Glass weighing scoops, suitable for the test portion and for insertion into the flasks (6.2)
26、. 6.2 Conical flasks, capacity 500 ml, fitted with ground glass stoppers and showing no evidence of the presence of moisture. 6.3 Analytical balance, capable of weighing to an accuracy of 0,001 g. 6.4 Volumetric flask, capacity 1 000 ml, ISO 10422 class A. 6.5 Pipette, capacity 25 ml, automatic or I
27、SO 6481 class A, fitted with an aspiration bulb. 7 Sampling A representative sample should have been sent to the laboratory. 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 met
28、hod is given in ISO 55553. 8 Preparation of test sample Prepare the sample in accordance with the method given in ISO 661. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo repro
29、duction or networking permitted without license from IHS -,-,- ISO 3961:2009(E) ISO 2009 All rights reserved 3 9 Procedure 9.1 Test portion and preparation of blank solution 9.1.1 According to the IV expected for the sample, weigh, to the nearest 0,001 g, in a glass weighing scoop (6.1), the mass of
30、 test portion indicated in Table 1. Table 1 Mass of test portion Expected IV wI g/100 g Mass of test portion m g Volume of solvent V ml wI 1,5 1,5 u wI 2,5 2,5 u wI 5 5 u wI 20 20 u wI 50 50 u wI 100 100 u wI 150 150 u wI 200 15,00 10,00 3,00 1,00 0,40 0,20 0,13 0,10 25 25 20 20 20 20 20 20 NOTE The
31、 mass of the sample shall be such that there will be an excess of Wijs reagent of between 50 % and 60 % of the amount added, i.e. 100 % to 150 % of the amount absorbed. 9.2 Determination 9.2.1 Place the glass scoop containing the test portion in a 500 ml conical flask (6.2) and add the volume of sol
32、vent (5.4) indicated in Table 1. Add 25,00 ml of the Wijs reagent (5.5) by pipette (6.5). Insert the stopper, swirl the contents and place the flask in the dark. NOTE The scoop remains in the flask. CAUTION Do not use a mouth pipette for the Wijs reagent. 9.2.2 Prepare a blank with solvent and reage
33、nt as in 9.2.1 but omitting the test portion. 9.2.3 For samples having an IV below 150, leave the flasks in the dark for 1 h. For samples with IVs above 150, and for polymerized products and oils containing conjugated fatty acids (such as tung oil, dehydrated castor oil) and any oils containing keto
34、 fatty acids (such as some grades of hydrogenated castor oil) and products oxidized to a considerable extent, leave the flasks in the dark for 2 h. 9.2.4 At the end of the reaction time (9.2.3), add 20 ml of potassium iodide (5.1) and 150 ml of water. Titrate against standard sodium thiosulfate solu
35、tion (5.3) until the yellow colour due to iodine has almost disappeared. Add a few drops of the starch solution (5.2) and continue the titration until the blue colour just disappears after very vigorous shaking. Record the volume, V2, of sodium thiosulfate solution required to reach the endpoint. No
36、te that potentiometric determination of the endpoint is permissible. 9.2.5 Carry out the determination using the blank solution (9.2.2) concurrently. In the blank determination, in 9.2.4, record the volume of sodium thiosulfate solution required to reach the endpoint as V1. Copyright International O
37、rganization for Standardization Provided by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 3961:2009(E) 4 ISO 2009 All rights reserved 10 Calculation The IV, wI, expressed
38、in grams per 100 g of fat, is given by the equation: 12 I 12,69()c VV w m = where c is the concentration, in moles per litre, of the sodium thiosulfate solution (5.3); V1 is the volume, in millilitres, of sodium thiosulfate solution used for the blank test; V2 is the volume, in millilitres, of sodiu
39、m thiosulfate solution used for the determination; m is the mass, in grams, of the test portion. Round off the result as indicated in Table 2. Table 2 Rounding off of results IV wI g/100 g Round off to wI 20 20 u wI 60 wI W 60 0,1 0,5 1 11 Precision 11.1 General The values given may not be applicabl
40、e to concentration ranges and matrices other than those given. 11.2 Repeatability The absolute difference between two independent test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment within a short interval of ti
41、me, should not be greater than the value of r indicated in Table 3. 11.3 Reproducibility The absolute difference between two independent test results, obtained using the same method on identical test material in different laboratories with different operators using different equipment, should not be
42、 greater than the value of R indicated in Table 3. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=HP Monitoring/1111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 3961:
43、2009(E) ISO 2009 All rights reserved 5 Table 3 Repeatability and reproducibility limits IV wI g/100 g Repeatability limit r Reproducibility limit R wI 20 20 u wI 50 50 u wI 100 100 u wI 135 0,2 1,3 2,0 3,5 0,7 3,0 3,0 5,0 12 Test report The test report shall contain at least the following informatio
44、n: a) all information necessary for the complete identification of the sample; b) the sampling method used, if known; c) the test method used, with reference to this International Standard; d) all operating details not specified in this International Standard, or regarded as optional, together with
45、details of any incidents which may have influenced the test result(s); e) the test result(s) obtained, or, if the repeatability has been checked, the final quoted result obtained. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=HP Monitoring/1
46、111111164 Not for Resale, 04/08/2009 03:07:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 3961:2009(E) 6 ISO 2009 All rights reserved Annex A (informative) Calculated iodine value A.1 General This annex describes a method for calculating the IV of edible oils direct
47、ly from fatty acid compositions determined by gas chromatography of methyl esters of fatty acids. It is applicable to triglycerides and free fatty acids and their hydrogenated products. For oils with an unsaponifiable content greater than 0,5 % (e.g. fish oils), the calculation tends to produce unde
48、restimates, and hence is not applicable. IMPORTANT While this procedure provides an IV, it is not intended to be a rapid method. The method gives two results from one analysis. A.2 Procedure A.2.1 Determine the fatty acid composition of the oil or fatty acid mixture. A.2.2 Calculate the IVs for groups of components as described in A.2.2.1 and A.2.2.2. NOTE The calculation tends to produce underestimates for materials