GB 5009.257-2016 PDF in English
GB 5009.257-2016 (GB5009.257-2016) PDF English
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Determination of trans fatty acids in foods -- Gas chromatographic method
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Standards related to (historical): GB 5009.257-2016
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GB 5009.257-2016: PDF in English GB 5009.257-2016
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard - Determination of
Trans-fatty Acids in Foodstuffs
ISSUED ON: AUGUST 31, 2016
IMPLEMENTED ON: MARCH 1, 2017
Issued by: National Health and Family Planning Commission of the
People’s Republic of China
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle ... 4
3 Reagents and Materials ... 4
4 Instruments and Equipment ... 5
5 Analytical Procedures ... 6
6 Expression of Analytical Result ... 9
7 Precision ... 11
8 Others ... 11
Appendix A Information of Standard Substance ... 12
Appendix B Chromatogram of Standard Substance ... 14
Appendix C Calculation of FID Response Factor and FID Calibration Factor 16
Appendix D FID Response Factor and FID Calibration Factor ... 17
National Food Safety Standard - Determination of
Trans-fatty Acids in Foodstuffs
1 Scope
This Standard specifies the gas chromatographic method for the determination of
trans-fatty acids and isomer in foods.
This Standard is applicable to the determination of trans-fatty acids in animal and
vegetable fats and oils, hydrogenated vegetable oil, refined vegetable oil and frying oil,
as well as foods that contain animal and vegetable fats and oils, hydrogenated
vegetable oil, refined vegetable oil and frying oil.
This Standard is not applicable to the determination of food samples, in which, free
fatty acid (FFA) content in fats and oils is more than 2%.
2 Principle
Animal and vegetable fats and oils samples, or fats in food samples extracted through
acid hydrolysis method, under alkaline condition, go through transesterification with
methanol; generate fatty acid methyl ester. Furthermore, on strong polarity stationary
phase capillary chromatographic column, separate it. Use gas chromatograph, which
is equipped with hydrogen flame ionization detector, for determination. Use area
normalization method to quantify it.
3 Reagents and Materials
Unless it is otherwise stipulated, all reagents used in this method shall be analytically
pure. Water shall be Grade-2 water stipulated in GB/T 6682.
3.1 Reagents
3.1.1 Hydrochloric acid (HCl, 20 = 1.19): content 36% ~ 38%.
3.1.2 Ether (C4H10O).
3.1.3 Petroleum ether: boiling range: 30 °C ~ 60 °C.
3.1.4 Absolute ethanol (CHOO): chromatographic purity.
3.1.5 Anhydrous sodium sulfate: before usage, at 650 °C, burn it for 4 h; store it in a
dryer for later usage.
considered as the sample test solution.
5.2.2 Foods containing fats and oils (except from animal and vegetable fats and
oils)
5.2.2.1 Determination of fats in foods
Solid and semi-solid lipid sample: weigh-take 2.0 g (accurate to 0.01 g; the weighing
amount of different foods may be properly adjusted, so as to guarantee that fat mass
in foods is not less than 0.125 g) of homogeneous sample. Place it in a 50 mL test
tube. Add 8 mL of water to thoroughly mix it up. Then, add 10 mL of hydrochloric acid
to evenly mix it up. Liquid sample: weigh-take 10.00 g of homogeneous sample, then,
place it in a 50 mL test tube. Add 10 mL of hydrochloric acid to evenly mix it up. Place
the above-mentioned test tube into 60 °C ~ 70 °C water bath. In every 5 min ~ 10 min,
oscillate it once. Last for around 40 min ~ 50 min, till the sample is completely
hydrolyzed. Take out the test tube. Add 10 mL of ethanol to thoroughly mix it up, then,
cool it down to room temperature.
Transfer the mixture into 125 mL separating funnel. Take 25 mL of ether, divide it into
two parts, then, respectively use them to rinse the test tube. Pour the rinsing liquid
together into the separating funnel. After ether is completely poured into the funnel, put
on a stopper; start to shake it for 1 min. Then, carefully open the stopper, release the
gas. In addition, use an appropriate amount of petroleum ether - ether solution (1 + 1)
to rinse the stopper and fats attached to the mouth of the funnel. Place it still for 10
min ~ 20 min, till the upper ether solution becomes limpid. Place the lower aqueous
phase into 100 mL beaker. Place the upper organic phase into another clean
separating funnel. Use a little petroleum ether - ether solution (1 + 1) to rinse the
separating funnel for extraction; collect the organic phase, then, combine it in the
separating funnel. Pour the aqueous phase in the beaker back to the separating funnel.
Then, take 25 mL of ether, divide it into two parts, then, respectively use them to rinse
the beaker. Pour the rinsing liquid together into the separating funnel. In accordance
with the above-mentioned steps of extraction, repeatedly extract it twice. Combine the
organic phase in the separating funnel. Let all the organic phase pass through a proper
amount of anhydrous sodium sulfate column. Use a little petroleum ether - ether
solution (1 + 1) to rinse the column. Gather all the effluent in a 100 mL measuring
cylinder with a stopper. Use ether to reach a constant volume; evenly mix it up.
Accurately transfer-take 50 mL of organic phase, then, place it into round-bottomed
flask, which already reaches a constant weight. In 50 °C water bath, rotate it and boil
off the solvent. Then, place it at 100 °C ± 5 °C; reach a constant weight, then, calculate
the content of fats in the foods. Place another 50 mL of organic phase in 50 °C water
bath, rotate it and boil off the solvent; it shall be used for the determination of trans-
fatty acid methyl ester.
5.2.2.2 Preparation of fatty acid methyl ester
m1---mass of the round-bottomed flask and fats, expressed in (g);
m0---mass of the round-bottomed flask, expressed in (g);
m2---mass of the sample, expressed in (g).
6.2 Calculation of Relative Mass Fraction
The relative mass fraction of the various components shall be calculated in accordance
with Formula (2):
Where,
wX---relative mass fraction of trans-fatty acid component X fatty acid methyl ester
calculated through normalization method, expressed in (%);
Ax---peak area of component X fatty acid methyl ester;
fx---calibration factor of component X fatty acid methyl ester; please refer to Table D.1
for the correction factor of chemical compounds;
At---the total of calibration area of all the peaks, except from solvent peak.
6.3 Calculation of Trans-fatty Acids Content in Fats
The mass fraction of trans-fatty acids in fats shall be calculated in accordance with
Formula (3):
Where,
wt---mass fraction of trans-fatty acids in fats, expressed in (%);
wX---relative mass fraction of component X fatty acid methyl ester calculated through
normalization method, expressed in (%).
6.4 Calculation of Trans-fatty Acids Content in Foods
Mass fraction of trans-fatty acids content in foods shall be calculated in accordance
with Formula (4):
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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