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1、INTERNATIONAL STANDARD FmT INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXAYHAPOflHAR OPrAHM3AMfl l-l0 CTAHflAPTM3AMkl Animal and vegetable fats and oils - Determination of polyunsaturated fatty acids with a ckck 1,4=diene structure c Corps gras dorigi
2、nes animale et vdgt!tale - Dosage des acides gras polyinsaturt% ayant une con Figura tion cis-cis dihigue- 1,4 ISO 7847 First edition 1987-12-15 Reference number Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/997254
3、5001 Not for Resale, 04/26/2007 20:56:51 MDTNo reproduction or networking permitted without license from IHS -,-,- Foreword ISO (the International Organization for Standardization) is a worldwide federation of national Standards bodies (ISO member bodies). The work of preparing International Standar
4、ds is normally carried out through ISO technical committees. Esch 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, govern- mental and non-governmental, in Iiaison with ISO, also ta
5、ke patt in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISO Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the m
6、ember bodies voting. International Standard ISO 7847 was prepared by Technical Committee ISO/TC 34, Agricultural food products. Users should note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard implies its lat
7、est edition, unless otherwise stated. 0 International Organkation for Standardization, 1987 0 Printed in Switzerland Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 20:56:51 MDTN
8、o reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISO 7847 : 1987 (E) Animal and vegetable fats and oils - Determination of polyunsaturated fatty acids with a cis,cis 1,4=diene . structure 1 Scope and field of application This International Standard specifi
9、es an enzymic method for the determination in animal and vegetable fats and oils of polyunsaturated fatty acids with a cis,cis 1 ,It-diene structure, in practice those of the linoleic (9,12-octadecadienoic) and linolenic (9,12,15-octadecatrienoic) acid series having 03 and 06 Unsaturation. The struc
10、ture is H -c 4 C ,HH, /H CH2/ c=c cisC - 1 lt is not applicable to fats and oils containing polyunsaturated fatty acids of the 08 and o9 series or containing branched chain fatty acids. 2 References ISO 661, Animal and vegetable fats and oils - Preparation of test Sample. ISO 5555, Animal and vegeta
11、ble fats and ois - Sampling. 3 Definition For the purposes of this International Standard, the following definition applies. cis,cis l this straight line shall pass through the origin. 9.7 Determination 9.7.1 Enzymic Oxidation Transfer, by means of a 1 ml graduated pipette (6.31, 0,l ml of dilute li
12、poxidase Solution (5.6) to a test-tube (6.4) (sec note 1 to 9.6.2). Then add 3 ml of the test solution (9.4) from flask B to the test-tube and Shake gently to ensure that the solution is mixed (sec note 2 to 9.6.2). Allow the tube to stand for 20 to 30 min. 9.7.2 Spectrometric measurements Transfer
13、the contents of the tube to a silica cell (sec 6.8). Using the spectrometer (6.81, measure the absorbance of the test Solution at the wavelength of maximum absorbance (approxi- mately 235 nm), using the Sample compensation Solution (See 9.5) for zero adjustment of the instrument. Take the mean of tw
14、o absorbance readings and read the mass of fatty acids from the calibration graph (9.6.4). NOTE - The zero adjustment using the Sample compensation Solution compensates for the absorbance due to any dienoic conjugated acids initially present in the Sample. The absorbance value of the Sample compensa
15、tion Solution should be checked against water because if it is too high compared with the test Solution, precision will be reduced. 9.8 Number of determinations Carry out two determinations on the same test Sample. Copyright International Organization for Standardization Provided by IHS under licens
16、e with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 20:56:51 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 7847 : 1987 (El 10 Expression of results 10.1 Method of calculation The polyunsaturated fatty acids content, expressed as a perc
17、entage by mass, is equal to m, x 100 vmO where mO 10.2 Repeatability The differente between the results of two determinations car- ried out in rapid succession by the same analyst, under the same conditions on the same test Sample, shall not exceed 3,5 % (mlm) (absolute value) of polyunsaturated fat
18、ty acids in the range 10 to 70 % (mlm). 11 Test report is the mass, in milligrams, of the test Portion; m, is the mass, in milligrams, of polyu acids read from the calibration graph; V is the numerical value of the volume, in Solution taken from the flask A (usually 1 ml). NOTE - The result obtained
19、 in this way is expressed on the whole fat or oil basis and not on the to tal of the fatty acids in the fat or Oil. fatty millilitres, of The test report shall show the method used and the result obtained, indicating clearly the method of expression used. lt shall also mention any operating details
20、not specified in this International Standard, or regarded as optional, together with details of any incidents likely to have influenced the result. The test report shall include all the information the complete identification of the Sample. necessary for 4 Copyright International Organization for St
21、andardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 20:56:51 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 7047 : 1987 (EI Annex Alternative procedure for saponification (This annex forms an in
22、tegral part of the Standard.) Dissolve the test portion (9.2) in a few millilitres of n-hexane (5.11, then dilute to the mark with the same solvent and mix. Transfer, by means of a pipette (6.21, 1,0 ml of the Solution to a 100 ml one-mark volumetric flask (6.1) labelled B, previously flushed with n
23、itrogen. When the Sample is expected to contain very low amounts of polyunsaturated fatty acids, transfer 2 to 4 ml rather than 1,0 ml to flask B. Completely evaporate the solvent under a gentle stream of nitrogen. To the solvent-free Sample in flask B add 2 ml of ethanolic potassium hydroxide Solut
24、ion (5.3) and stopper the flask. Leave the flask in the dark and allow saponification to take place for at least 4 h. Proceed as in 9.7. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/2
25、6/2007 20:56:51 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 7847 : 1987 (EI UDC 665.2/.3 : 543.852 Descriptors: agricultural products, animal fats, vegetable fats, animal oils, vegetable oils, Chemical analysis, determination of content, fatty acids. Price based on 5 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 20:56:51 MDTNo reproduction or networking permitted without license from IHS -,-,-