BS EN ISO 660:2000 2005

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Animal and vegetable fats and oils. Determination of acid value and acidity

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1	BRITISH STANDARD BS EN ISO 660:2000 Incorporating Amendments Nos. 1 (renumbers BS 684-2.10 as BS EN ISO 660) and 2 Animal and vegetable fats and oils – Determination of acid value and acidity The European Standard EN ISO 660:1999, with the incorporation of amendment A1:2005, has the status of a British Standard IMPORTANT NOTE. This standard should be read in conjunction with BS 684-0.1 and BS EN ISO 661 (BS 684-0.2). ICS 67.200.10
2	This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Board, was published under the authority of the Standards Board and comes into effect on15 September 1996 © BSI 14 December 2005 The following BSI references relate to the work on this standard: Committee reference AW/11 Draft for comment 94/505064 DC ISBN 0 580 26317 7 National foreword This British Standard is the English language version of EN ISO 660:1999, including amendment A1:2005. It is identical with ISO 660:1996, including amendment 1:2003. The start and finish of text introduced or altered by ISO amendment is indicated in the text as tags !”. Tags indicating changes to text carry the number of the amendment. For example, text altered by ISO amendment 1 is indicated by !”. The UK participation in its preparation was entrusted to Technical Committee AW/11, Animal and vegetable fats and oils, which has the responsibility to: – present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; – monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references Attention is drawn to the fact that CEN and CENELEC Standards normally include an annex which lists normative references to inte… 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 immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN ISO title page, the EN ISO foreword page, pages 1 to 7 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amd. No. Date Comments 10895 December 2000 Renumbers BS 684-2.10 as BS EN ISO 660 and adds Annex ZA 15853 December 2005 See national foreword
3	Contents Page 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Hot ethanol method using indicator 1 5 Cold solvent method using indicator 2 6 Potentiometric method 3 7 Calculation 4 8 Precision 5 Annex A (informative) Results of interlaboratory tests 6 Annex B (informative) Bibliography 6 Table 1 – Mass of test portion 2 Table A.1 – Results of first interlaboratory tests 7 Table A.2 – Results for Lampante virgin olive oil 6 Table A.3 – Results for olive oil and extra virgin olive oil 6
5	EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN ISO 660 May 1999 + A1 August 2005 ICS 67.200.10 English version Animal and vegetable fats and oils – Determination of acid value and acidity (includes amendment A1:2005) (ISO 660:1996 + A1:2003) Corps gras d’origines animale et végétale – Détermination de l’indice d’acide et de l’acidité (inclut l’amendement A1:2005) (ISO 660:1996 + A1:2003) Tierische und pflanzliche Fette und Öle – Bestimmung der Säurezahl und der Azidität (enthält Änderung A1:2005) (ISO 660:1996 + A1:2003) This European Standard was approved by CEN on 15 April 1999. Amendment A1 was approved by CEN on 28 July 2005. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this Europea… This European Standard exists in three official versions (English, French, German). A version in any other language made by tran… CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © 1999 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 660:1999 + A1:2005 E
6	Foreword The text of the International Standard from Technical Committee ISO/TC 34, Agricultural food products, of the International Orga… 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 November 1999, and conflicting national standards shall be withdrawn at the latest by November 1999. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to … NOTE Normative references to International Standards are listed in Annex ZA (normative). Foreword to amendment A1 The text of ISO 660:1996/A1:2003 has been prepared by Technical Committee ISO/TC 34 ‘‘Agricultural food products’’ of the Intern… 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 February 2006, and conflicting national standards shall be withdrawn at the latest by February 2006. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to … Endorsement notice The text of ISO 660:1996/A1:2003 has been approved by CEN as EN ISO 660:1999/A1:2005 without any modifications.
7	1 Scope This International Standard specifies three methods (two titrimetric and one potentiometric) for the determination of acidity in… The method described in clause 4 is the reference method. The method described in clause 5 applies to oils and fats which are not strongly coloured. The methods are not applicable to waxes. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International St… ISO 661:1989, Animal and vegetable fats and oils – Preparation of test sample. ISO 3696:1987, Water for analytical laboratory use – Specification and test methods. 3 Definitions For the purposes of this International Standard, the following definitions apply. 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 acid value is expressed in milligrams per gram 3.2 acidity content of free fatty acids determined according to the procedure specified in this International Standard acidity is expressed as a percentage by mass NOTE 1 If the result of the determination is reported as acidity, without further explanation, this is by convention the acidity expressed based on oleic acid. NOTE 2 If the sample contains mineral acids, these are, by convention, determined as fatty acids. 4 Hot ethanol method using indicator 4.1 General This method is the reference method for fats (see clause 1). NOTE 3 Under the conditions specified in this method, short-chain fatty acids, if present, are volatile. 4.2 Principle A test portion is dissolved in hot ethanol and titrated with an aqueous solution of sodium or potassium hydroxide. 4.3 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and water in accordance with grade 3 of ISO 3696. 4.3.1 Ethanol, of minimum purity 95 % (V/V). 4.3.2 Sodium or potassium hydroxide, standard volumetric solution, c(NaOH) or c(KOH) = 0,1 mol/l. 4.3.3 Sodium or potassium hydroxide, standard volumetric solution, c(NaOH) or c(KOH) = 0,5 mol/l. 4.3.4 Phenolphthalein, 10g/l solution in ethanol [95 % (V/V)]. NOTE 4 In determinations of strongly coloured solutions, observation of the endpoint of the titration may be facilitated by adding 1 ml of a 0,1% (m/m) solution of methylene blue to each 100 ml of phenolphthalein indicator solution. 4.3.5 Alkali blue 6B, or (in the case of dark-coloured fats) thymolphthalein, 20g/l solution in ethanol, [95 % (V/V)]. 4.4 Apparatus Usual laboratory apparatus and, in particular, the following. 4.4.1 Microburette, of 10 ml capacity, graduated in 0,02 ml subdivisions. 4.4.2 Analytical balance, capable of weighing to the required accuracy (see Table 1). 4.5 Sampling It is important that the laboratory receive a sample which is truly representative and has not 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. 4.6 Preparation of test sample Prepare the test sample in accordance with ISO 661, except that if the sample contains volatile fatty acids, the test sample shall not be heated and filtered.
8	4.7 Procedure 4.7.1 Test portion Weigh into a flask a sufficient mass of the test sample (4.6) as shown in Table 1, according to the colour and expected acid value. NOTE 5 The mass of the test portion and the concentration of the titrant should be such that the titrate does not exceed 10 ml. Table 1 – Mass of test portion Expected acid value Mass of test portion Accuracy of weighing of the test portion g g < 1 20 0,05 1 to 4 10 0,02 4 to 15 2,5 0,01 15 to 75 0,5 0,001 > 75 0,1 0,000 2 4.7.2 Determination Heat to boiling 50 ml of the ethanol (4.3.1) containing 0,5 ml of the phenolphthalein indicator (4.3.4) in a second flask. Whils… 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. NOTE 6 Larger volumes of ethanol and indicator may be necessary for dark-coloured fats. Add the neutralized ethanol to the test portion in the first flask and mix thoroughly. Bring the contents to the boil and titrat… 5 Cold solvent method using indicator 5.1 General This method is most suited to fats which are not strongly coloured. 5.2 Principle A test portion is dissolved in a mixed solvent and titrated with an ethanolic solution of potassium hydroxide. 5.3 Reagents Use only reagents of recognized analytical grade, and water of grade 3 in accordance with ISO 3696. 5.3.1 Diethyl ether and 95 % (V/V) ethanol, 1 + 1 mixture by volume. WARNING – Diethyl ether is very flammable and may form explosive peroxides. Use with great caution. Neutralize, just before use, by adding the potassium hydroxide solution (5.3.2) in the presence of 0,3 ml of the phenolphthalein solution (5.3.3) per 100 ml of solvent mixture (see note 6 in 4.7.2). If it is not possible to use diethyl ether, a mixed solvent may be used, as follows: toluene and 95 % (V/V) ethanol, 1 + 1 mixture by volume, toluene and 99 % (V/V) propan-2-ol, 1 + 1 mixture by volume. The mixed solvent may be replaced by 99 % (V/V) propan-2-ol for both crude and refined vegetable fats. 5.3.2 Potassium hydroxide, standard volumetric solution in ethanol: c(KOH) = 0,1 mol/l (solution A) or, if necessary c(KOH) = 0,5 mol/l (solution B). The ethanolic potassium hydroxide solution may be replaced by an aqueous potassium or sodium hydroxide solution, but only if the volume of water introduced does not lead to phase separation. 5.3.2.1 Dissolve 7 g (for solution A) or 35 g (for solution B) of potassium hydroxide pellets in ethanol (4.3.1) and dilute to 1 000 ml with the ethanol. NOTE 7 Propan-2-ol may be used instead of ethanol. Determine the concentration of the solution, immediately before use, as follows. Weigh, to the nearest 0,000 2 g, either 0,15 g (for solution A) or 0,75 g (for solution B) of benzoic acid of minimum purity 99,9 % (m/m), or another primary standard, in a 150 ml beaker and dissolve in 50 ml of the 4-methylpentan-2-one (6.2.1). Introduce the electrodes of a pH-meter (see 6.3.1), start the stirrer (6.3.2), and titrate with the potassium hydroxide solution (A or B, depending on the expected acidity of the sample) to the equivalence point (see 6.6.2.2). The concentration of the potassium hydroxide solution, expressed in moles per litre, is given by:
9	where m0 is the mass, in grams, of benzoic acid used; V0 is the volume, in millilitres, of potassium hydroxide solution used. NOTE 8 In the above and later mathematical expressions, the symbols represent the numerical values of the quantities. Use solution prepared at least 5 days previously and decanted into a brown glass bottle, fitted with a rubber stopper provided w… 5.3.2.2 A stable colourless solution of potassium hydroxide may also be prepared in the following manner. Boil, under reflux, 1 … 5.3.2.3 The solution may also be prepared without distillation in the following manner. Add 4 ml of aluminium tri-sec-butoxide t… 5.3.3 Phenolphthalein, see 4.3.4. 5.3.4 Alkali blue 6B or thymolphthalein, see 4.3.5. 5.4 Apparatus Usual laboratory equipment and, in particular, the microburette described in 4.4.1. 5.5 Sampling See 4.5. 5.6 Preparation of test sample See 4.6. 5.7 Procedure 5.7.1 Test portion Take a sufficient mass of the test sample (5.6), according to the expected acid value, in accordance with Table 1. Weigh the test portion into a 250 ml conical flask. 5.7.2 Determination 5.7.2.1 Dissolve the test portion (5.7.1) in 50 ml to 150 ml of the previously neutralized solvent mixture (5.3.1). Titrate, whilst swirling the solution, with the potassium hydroxide solution (5.3.2) (see 5.7.2.3) to the endpoint as described in 4.7.2. 5.7.2.2 In the case of very low acid values (< 1), it is preferable to pass a gentle flow of nitrogen through the test solution. 5.7.2.3 If the quantity of potassium hydroxide solution A (0,1 mol/l) required exceeds 10 ml, use solution B (0,5 mol/l). 5.7.2.4 If the solution becomes turbid during titration, add a sufficient quantity of the mixed solvent (5.3.1) to give a clear solution. 6 Potentiometric method 6.1 Principle Potentiometric titration of the three fatty acids in a test portion with a solution of potassium hydroxide and propan-2-ol in a non-aqueous medium. 6.2 Reagents Use only reagents of recognized analytical grade and water in accordance with grade 3 of ISO 3696. 6.2.1 4-Methylpentan-2-one (previously known as methyl isobutyl ketone), neutralized just before use by adding the potassium hydroxide solution (6.2.2), using the pH-meter (6.3.1). 6.2.2 Potassium hydroxide, standard volumetric solution C, c(KOH) = 0,1 mol/l, in propan-2-ol, prepared and standardized as described in 5.3.2 for solution A. 6.2.3 Potassium hydroxide, standard volumetric solution D, c(KOH) = 0,5 mol/l, in propan-2-ol, prepared and standardized as described in 5.3.2 for solution B. 6.3 Apparatus Use laboratory apparatus and, in particular, the following. 6.3.1 pH-meter, equipped with glass and calomel electrodes. Contact between the saturated potassium chloride solution and the test solution shall be made across a sintered glass or porcelain plate at least 3 mm thick. NOTE 9 It is advisable to store the glass electrode for 12 h before titration in the 4-methylpentan-2-one (6.2.1). Dry it very g…
10	NOTE 10 If the electrode does not function satisfactorily, try to regenerate it by keeping it for 14 h in a 1 mol/l solution of … NOTE 11 The use of porcelain or thick glass plates to ensure contact between the saturated potassium chloride solution and the test solution prevents diffusion currents and accidental potential differences. 6.3.2 Stirrer, preferably a magnetic stirrer. 6.3.3 Analytical balance, as in 4.4.2. 6.4 Sampling See 4.5. 6.5 Preparation of sample See 4.6. 6.6 Procedure 6.6.1 Test portion Weigh, to the nearest 0,01 g, 5 g to 10 g of the test sample (6.5) into a tall-form 150 ml beaker. 6.6.2 Determination 6.6.2.1 Dissolve the test portion (6.6.1) in 50 ml of the 4-methylpentan-2-one (6.2.1). Introduce the electrodes of the pH-meter (6.3.1), start the stirrer (6.3.2) and titrate with the potassium hydroxide solution (6.2.2 or 6.2.3, depending on the expected acidity of the sample) to the equivalence point. NOTE 12 The equivalence point is generally near to the value on the pH scale, and can be determined graphically by observing the… 6.6.2.2 It is not possible to determine the inflection point in the case of crude cottonseed oils rich in gossypol. In this case… Dissolve approximately 0,282 g of oleic acid in 50 ml of the 4-methylpentan-2-one (6.2.1). Plot the neutralization curve of the … 7 Calculation 7.1 Acid value The acid value is equal to where V is the volume, in millilitres, of standard volumetric sodium or potassium hydroxide solution used; c is the exact concentration, in moles per litre, of the standard volumetric sodium or potassium hydroxide solution used; m is the mass, in grams, of the test portion. NOTE 13 The concentration of the ethanolic sodium or potassium hydroxide solution varies with temperature and it may be useful to use the following correction: where is the corrected volume, in millilitres, of the standard sodium or potassium hydroxide solution; Vt is the volume, in millilitres, of the standard sodium or potassium hydroxide solution measured at temperature t; t is the temperature at which the determination was carried out, in degrees Celsius; t0 is the temperature, in degrees Celsius, at which the concentration of the standard sodium or potassium hydroxide solution was determined. 7.2 Acidity The acidity, expressed as a percentage by mass, and according to fat type (see Table 2), is equal to where V is the volume, in millilitres, of the standard volumetric sodium or potassium hydroxide solution used (see note 13 in 7.1); c is the exact concentration, in moles per litre, of the standard volumetric sodium or potassium hydroxide solution used; M is the molar mass, in grams per mole, of the acid chosen for expression of the result (see Table 2); m is the mass, in grams, of the test portion.
11	Table 2 – Choice of fatty acid for expression of acidity Type of fat Expressed as Molar mass g/mol Coconut oil, palm kernel oil and similar oils Lauric acid 200 Palm oil Palmitic acid 256 Oils from certain Cruciferaea Erucic acid 338 All other fats Oleic acid 282 a In the case of rapeseed oil having a maximum erucic acid content of 5 % (m/m), the acidity shall be expressed as oleic acid. NOTE 14 If the result is reported simply as “acidity”, without further definition, this is, by convention, expressed as oleic acid. NOTE 15 If the sample contains mineral acids, these are, by convention, determined as fatty acids. 8 Precision Details of interlaboratory tests are given in annex A. The values derived from these tests may not be applicable to concentration ranges and matrices other than those given. 8.1 Repeatability The absolute difference between two independent single test results, obtained using the same method on identical test material i… 3 % of the mean of the two results when the acidity is 3 % or less; 1 % of the mean of the two results when the acidity is greater than 3 %. 8.2 Reproducibility The absolute difference between two single test results, obtained using the same method on identical test material in different laboratories with different operators using different equipment, should not be greater than 15 % of the mean of the two results when the acidity is 3 % or less; 5 % of the mean of the two results when the acidity is greater than 3 %. 9 Test report The test report shall specify: – the method in accordance with which sampling was carried out, if known, – the method used, – the result obtained, indicating clearly the method of expression used and, – if the repeatability has been checked, the final quoted result obtained. It shall also mention any operating conditions not specified in this International Standard, or regarded as optional, as well as any incidents that may have influenced the result. The test report shall include all the information necessary for the complete identification of the sample.
12	Annex A (informative) Results of interlaboratory tests A series of interlaboratory tests, carried out at the international level using the reference method described in clause 4, with… ! Table A.1 – Results of first interlaboratory tests” Oil Palm kernel Sunflower Coconut Palm oil Palm oil Palm kernel Palm kernel Number of laboratories 23 23 25 12 27 41 41 Number of acceptable results 22 22 25 10/11 27 39 40 Mean acidity values, % 7,26 0,83 1,49 3,11 4,09 6,46 1,72 Repeatability, r 0,07 0,025 0,025 0,03 0,06 0,07 0,06 Reproducibility, R 0,24 0,075 0,075 0,45 0,18 0,23 0,20 !A further series of interlaboratory tests, carried out by laboratories from 12 countries, using the reference method described … Table A.2 – Results for Lampante virgin olive oil No. of laboratories 28 28 No. of laboratories after eliminating outliers 26 24 Overall mean value, % 3,80 19,55 Standard deviation of repeatability, sr 0,03 0,09 Standard deviation of reproducibility, sR 0,12 0,60 Repeatability limit, r 0,07 0,26 Reproducibility limit, R 0,33 1,67 A further series of interlaboratory tests, using the reference method described in Clause 4, was carried out by the International Olive Oil Council, Madrid. The results (analysed in accordance with ISO 5725) are given in Table A.3. Table A.3 – Results for olive oil and extra virgin olive oil No. of laboratories after eliminating outliers 37 39 Number of outlying laboratories removed 0 2 Overall mean value, % 0,604 0,343 Standard deviation of repeatability, sr 0,012 0,007 Coefficient of variation of repeatability, % 1,92 1,92 Repeatability limit, r (2,8 × sr ) 0,033 0,018 Standard deviation of reproducibility, sR 0,035 0,019 Coefficient of variation of reproducibility, % 5,81 5,50 Reproducibility limit, R (2,8 × sR) 0,098 0,053 Sample A: olive oil (90 % extra virgin olive oil + 10 % refined olive oil), 1999 analysis. Sample B: extra virgin olive oil, 2001 analysis. ”
13	Annex B (informative) Bibliography [1] ISO 5555:1991, Animal and vegetable fats and oils – Sampling. [2] ISO 5725:1986, Precision of test methods – Determination of repeatability and reproducibility for a standard test method by interlaboratory tests (now withdrawn), was used to obtain the precision data. Annex ZA (normative) Normative references to international publications with their relevant European publications This European Standard incorporates by dated or undated reference, provisions from other publications. These normative reference… ISO 661 1989 Animal and vegetable fats and oils – Preparation of test sample EN ISO 661 1995 ISO 3696 1987 Water for analytical laboratory use – Specification and test methods EN ISO 3696 1995
14	BS EN ISO 660:2000 BSI 389 Chiswick High Road London W4 4AL BSI – British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure 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 ina… BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services. Tel: 020 8996 9001. Fax: 020 8996 7001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested. Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical… Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase pri… Copyright Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of the publications of the international st… This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size,… If permission is granted, the terms may include royalty payments or a licensing agreement. Details and advice can be obtained from the Copyright Manager. Tel: 020 8996 7070.

Additional information

Publication Date	2005-12-14
Amends	BS EN ISO 660:2000
Descriptors	Solvent extraction methods, Potentiometric methods, Vegetable oils, Acidimetry, Colorimetry, Precision, Acidity, Fats, Acid number, Test specimens, Animal fats, Animal oils, Food testing, Volumetric analysis, Vegetable fats, Fatty acids, Chemical analysis and testing, Reproducibility
Identical National Standard Of	ISO 660:1996/AMD 1:2003, EN ISO 660:1999/A1:2005
Standard Number	BS EN ISO 660:2000
ISBN	0 580 26317 7
Replaced By	BS EN ISO 660:2009
Withdrawn Date	2009-07-31
Pages	14
Committee	AW/307
Publisher	BSI
Replaces	BS 684-2-2.10:1988
Title	Animal and vegetable fats and oils. Determination of acid value and acidity
Status	Withdrawn
ICS Codes	67.200.10 - Animal and vegetable fats and oils

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