BS 684-2 12-1984 Methods of analysis of fats and fatty oils - Other methods - Determination of oxidized fatty acids《脂肪和油分析方法 第2部分 其他方法 第12节 氧化脂肪酸测定》.pdf

1、BRITISH STANDARD CONFIRMED SEPTEMBER1989 BS 684-2.12: 1984 Methods of analysis of Fats and fatty oils Part 2: Other methods Section 2.12 Determination of oxidized fatty acids IMPORTANT NOTE. It is essential that BS 684-0, which is published separately, be read in conjunction with this Section. UDC 6

2、65.1.014:543.21:547.29BS684-2.12:1984 This British Standard, having been prepared under the directionof the Food and Agriculture Standards Committee,was published underthe authority of the BoardofBSI and comes into effecton 28September1984 BSI 08-1999 The following BSI references relate to the work

3、on this standard: Committee reference FAC/18 Draft for comment 84/50703 DC ISBN 0 580 14005 9 Foreword This Section of BS 684 was prepared under the direction of the Food and Agriculture Standards Committee. With the publication of this Section, the revision of BS 684:1958 has been completed and tha

4、t standard is withdrawn. 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

5、 This document comprises a front cover, an inside front cover, pagesi andii, pages1 and2, 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. Amen

6、dments issued since publication Amd. No. Date of issue CommentsBS684-2.12:1984 BSI 08-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Definition 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling 1 7 Procedure 1 8 Expression of results 2 9 Test report 2 Publications referred to Insid

7、e back coverii blankBS684-2.12:1984 BSI 08-1999 1 1 Scope This Section describes a method for the determination of oxidized fatty acids in animal and vegetable fats and oils. NOTEThe title of the publication referred to in this Section is given on the inside back cover. 2 Definition For the purposes

8、 of this Section of BS 684 the following definition applies. oxidized fatty acids those acids insoluble in light petroleum under the conditions described 3 Principle A test portion is saponified and ethanol is evaporated. The residue is dissolved in water, acidified and light petroleum is added. The

9、 insoluble oxidized fatty acids are recovered and dissolved in ethanol, the ethanol is evaporated and the residue is weighed. 4 Reagents All reagents shall be of recognized analytical quality. The water used shall be distilled water or water of at least equivalent purity. 4.1 Potassium hydroxide sol

10、ution, c(KOH) = 0.5mol/L in95% ethanol (V/V). 4.2 Hydrochloric acid solution, c(HCI) = 1.0 mol/L. 4.3 Light petroleum, boiling range 40 C to 60 C. 4.4 Ethanol, 95% (V/V). 5 Apparatus The usual laboratory apparatus is required. 6 Sampling The sample shall be taken in accordance with BS627. 7 Procedur

11、e 7.1 Preparation of test sample Prepare the test sample in accordance with BS 684-0. 7.2 Saponification From the test sample (7.1), weigh a test portion of5 0.2g to the nearest milligram into a250mL flat-bottomed flask. Add 50mL potassium hydroxide solution (4.1), attach a condenser and reflux gent

12、ly for1h with swirling at intervals. 7.3 Separating the oxidized acids Remove the flask from the condenser and evaporate the contents to a syrupy paste. Add 10mL water and evaporate almost to dryness to remove ethanol. Dissolve the residue in100mL hot water. Transfer the solution to a500mL separatin

13、g funnel, washing in with about 10mL hot water. Acidify with30mL hydrochloric acid solution (4.2). Cool to room temperature, shaking well to ensure liberation of fatty acids. Add200mL light petroleum (4.3), shake well to dissolve fatty acids and allow to stand overnight or for at least5h to allow th

14、e insoluble oxidized acids to precipitate. Run off completely and discard the lower aqueous layer, which should not contain insoluble material. Pour the light petroleum from the top of the separating funnel through a fast filter paper. Wash the separating funnel with 2 25mL light petroleum, pouring

15、the washings through the filter paper. Wash the outlet tube, the rim of the top of the separating funnel, the filter paper and the filter funnel with light petroleum using 3 10mL in total, ensuring that the top of the filter paper is adequately washed. 7.4 Recovering and weighing the oxidized acids

16、Dissolve the oxidized acids in the separating funnel in25mL hot ethanol (4.4), pass the hot solution through the filter paper which contains oxidized acids and collect in a weighed150mL beaker. Repeat, using50mL hot ethanol, running the ethanol on to the rim of the paper. Ensure that all the oxidize

17、d acids are collected in the beaker by washing the apparatus with successive5mL quantities of hot ethanol. Evaporate the ethanol. Dry the beaker and residue at103 2 C for30min, cool and weigh. Repeat the30min drying, cooling and weighing until successive weighings do not differ by more than1mg. 7.5

18、Number of determinations Carry out two determinations on the same test sample.BS684-2.12:1984 2 BSI 08-1999 8 Expression of results Calculate the content of oxidized fatty acids, A, as a percentage by mass from the following equation. Take as the result the mean of two determinations. 9 Test report

19、The test report shall show the method used and the results obtained. It shall also mention any operating conditions not specified in this Section as well as any circumstances that may have influenced the results. The test report shall include all details required for complete identification of the s

20、ample. where m 0 is the mass (in g) of the test portion; m 1 is the mass (in g) of the empty beaker; m 2 is the mass (in g) of the beaker and acids. A 100m 2 m 1 () m 0 - =BS684-2.12:1984 BSI 08-1999 Publications referred to BS 627, Methods for sampling animal and vegetable fats and oils. BS 684, Me

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