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GB 5009.168-2016 PDF English

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GB 5009.168-2016: National food safety standard - Determination of fatty acids in foods
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GB 5009.168: Historical versions

Standard IDUSDBUY PDFDeliveryStandard Title (Description)Status
GB 5009.168-2016125 Add to Cart Auto, 9 seconds. National food safety standard - Determination of fatty acids in foods Valid
GB/T 5009.168-2003239 Add to Cart 3 days Determination of eicosapentaenoic acid and docosahexaenoic acid in foods Obsolete

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GB 5009.168-2016: National food safety standard - Determination of fatty acids in foods

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GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA National food safety standard Determination of fatty acids in foods Issued on. DECEMBER 23, 2016 Implemented on. JUNE 23, 2017 Issued by. National Health and Family Planning Commission of the People’s Republic of China; China Food and Drug Administration.

Table of Contents

Foreword... 4 1 Scope... 5 2 Principle... 5 3 Reagents and materials... 6 4 Apparatus and equipment... 7 5 Analysis procedure... 8 6 Expression of analysis results... 11 7 Principle... 14 8 Reagents and materials... 15 9 Apparatus and equipment... 17 10 Analysis procedure... 17 11 Expression of analysis results... 19 12 Principle... 20 13 Reagents and materials... 20 14 Apparatus and equipment... 20 15 Analysis procedure... 21 16 Expression of analysis results... 21 17 Precision... 22 18 Quantitation limits... 22 Annex A Molecular formula and CAS number of single fatty acid methyl ester standards... 23 Annex B Typical reference chromatogram of 37 kinds of fatty acid methyl ester standard solutions... 25 Annex C Retention time and relative retention time reference for fatty acid methyl esters... 26 Annex D Coefficients for conversion between fatty acid methyl esters, fatty acids and fatty acid triglycerides... 28 Annex E Quantitation limits for fatty acids... 30

1 Scope

This Standard specifies the determination method for the content of fatty acids in foods. This Standard applies to the determination of total fats, saturated fats (fatty acids) and unsaturated fats (fatty acids) in foods. In this Standard, the hydrolysis-extraction method applies to the determination of the content of fatty acids in foods; the transesterification method applies to the determination of the content of fatty acids in fat samples with free fatty acid content of not more than 2 %; the acetyl chloride-methanol method applies to the determination of the content of fatty acids in milk powder and anhydrous cream samples with water content less than 5 %. Method I Internal standard method

2 Principle

2.1 Hydrolysis-extraction method. after the fats in the sample that has added with internal standard are extracted with hydrolysis-ether solution, saponify and methyl- esterify the sample under alkaline conditions to produce fatty acid methyl esters. After analyzed by capillary column gas chromatography, use internal standard method to quantitatively determine the content of fatty acid methyl esters. According to the content and conversion coefficients of various fatty acid methyl esters, calculate the content of total fats, saturated fats (fatty acids), monounsaturated fats (fatty acids) and polyunsaturated fats (fatty acids). Animal and vegetable fat samples are directly saponified and fatty-acid-methyl esterified after adding with internal standard, without fat extraction. 2.2 Transesterification method (applies to fats with free fatty acid content of not more than 2 %). DISSOLVE fats in isooctane; after adding internal standard, ADD potassium hydroxide methanol solution to make the sample methyl-esterified through transesterification. After the reaction is complete, USE sodium sulfate to neutralize the residual potassium hydroxide to avoid saponification of methyl esters.

3 Reagents and materials

Unless otherwise stated, the reagents used in this method are analytical regents and the water is the Grade 1 water specified in GB/T 6682. 3.1 Reagents 3.1.1 Hydrochloric acid (HCl). 3.1.2 Ammonia (NH3 · H2O). 3.1.3 Pyrogallic acid (C6H6O3). 3.1.4 Ether (C4H10O). 3.1.5 Petroleum ether. with a boiling range of 30 °C ~ 60 °C. 3.1.6 Ethanol (C2H6O) (95 %). 3.1.7 Methanol (CH3OH). chromatographically pure. 3.1.8 Sodium hydroxide (NaOH). 3.1.9 N-heptane [CH3(CH2)5CH3]. chromatographically pure. 3.2 Preparation of reagents 3.2.1 Hydrochloric acid solution (8.3 mol/L). WEIGH 250 mL of hydrochloric acid; DILUTE with 110 mL of water; MIX well. It can be placed for 2 months at room temperature. 3.2.2 Ether-petroleum ether mixture (1 + 1). TAKE the same volume of ether and petroleum ether; MIX well for further use. 3.3 Standards 3.4 Preparation of standard solutions 3.4.1 Triundecanoin internal standard solution (5.00 mg/mL). accurately WEIGH 2.5 g (accurate to 0.1 mg) of triundecanoin to a flask; ADD methanol to dissolve; TRANSFER into a 500-mL volumetric flask; DILUTE with methanol to constant volume. It can be stored for 1 month when refrigerated in the refrigerator. 3.4.2 Mixed fatty acid methyl ester standard solution. TAKE the appropriate amount of fatty acid methyl ester to mix with standard; TRANSFER to a 10-mL volumetric flask; DILUTE with n-heptane to constant volume; STORE in the refrigerator of -10 °C below; VALID for 3 months.

4 Apparatus and equipment

4.1 Homogenizer or laboratory tissue pulverizer or grinder. 4.2 Gas chromatograph. with a hydrogen flame ion detector (FID). 4.3 Capillary chromatographic column. with polydipyldiphenyl siloxane strong polar stationary phase, a column length of 100 m, an inner diameter of 0.25 mm and a film thickness of 0.2 μm. 4.4 Constant temperature water bath. with a temperature range of 40 °C ~ 100 °C, temperature control ± 1 °C. 4.5 Analytical balance. with a division of 0.1 mg. 4.6 Rotary evaporator.

5 Analysis procedure

5.1 Preparation of samples During sampling and preparation, it shall avoid sample contamination. Solid or semi- solid samples are pulverized using a tissue pulverizer or grinder. Liquid samples are homogenized using a homogenizer, stored at -18 °C or below, and used for analysis after thawed. 5.2 Pretreatment of samples 5.2.1 Hydrolysis-extraction method 5.2.1.1 Weighing of samples WEIGH 0.1 g ~ 10 g (accurate to 0.1 mg, containing about 100 mg ~ 200 mg of fats) of uniform sample into a 250-mL flat-bottom flask; accurately ADD 2.0 mL of triundecanoin internal standard solution. ADD about 100 mg of pyrogallic acid; ADD several zeolites; 5.2.1.2 Hydrolysis of samples Acid hydrolysis method. foods (except dairy products and cheeses). ADD 10 mL of hydrochloric acid solution, MIX well. PLACE the flask in a water bath at 70 °C to 80 °C to hydrolyze for 40 min. SHAKE the flask once every 10 min so that the particles adhering to the walls of the flask are mixed into the solution. After the hydrolysis is complete, REMOVE the flask and COOL to room temperature. 5.2.1.3 Fat extraction ADD 10 mL of 95 % ethanol to the hydrolyzed sample, MIX well. TRANSFER the hydrolyzate in the flask to a separatory funnel; USE 50 mL of ether petroleum ether mixture to rinse the flask and stopper; ADD the rinsing solution to the separatory funnel; COVER the cap. SHAKE for 5 min, STAND for 10 min. 5.2.1.4 Saponification of fats and methyl esterification of fatty acids ADD 8 mL of 2 % sodium hydroxide methanol solution in the fat extract; CONNECT to the reflux condenser; REFLUX in 80 °C ± 1 °C water bath until the oil droplets disappear. 5.2.2 Transesterification method Applies to fat samples with free fatty acid content of not more than 2 %. 5.3 Determination 5.3.1 Chromatographic reference conditions INJECT the single fatty acid methyl ester standard solution and the fatty acid methyl ester mixed standard solution INTO the gas chromatograph respectively, and QUALIFY the chromatographic peaks. The gas chromatogram of the fatty acid methyl ester mixed standard solution is shown in Annex B. 5.3.2 Determination of samples

6 Expression of analysis results

6.1 Content of single fatty acid methyl ester in the sample The content of single fatty acid methyl ester in the sample is calculated according to equation (1). 6.2 Content of saturated fats (fatty acids) in the sample The content of saturated fats (fatty acids) in the sample is calculated according to equation (3), and the content of single saturated fatty acids in the sample is calculated according to equation (4). 6.4 Content of polyunsaturated fats (fatty acids) in the sample The content of polyunsaturated fats (fatty acids) in the sample (XPoly-Unsaturated Fat) is calculated according to equation (8), and the content of single polyunsaturated fatty acid is calculated according to equation (9).

7 Principle

7.1 Hydrolysis-extraction method. after the fats in the sample are extracted with hydrolysis-ether solution, saponify and methyl-esterify the sample under alkaline conditions to produce fatty acid methyl esters. After analyzed by capillary column gas chromatography, use external standard method to quantitatively determine the content of fatty acids. 7.2 Acetyl chloride-methanol method (applies to milk powder and anhydrous cream samples with water content of less than 5 %). acetyl chloride reacts with methanol to produce hydrochloric acid-methanol and make the fats and free fatty acids methyl esterified. After extracted with toluene, separately tested with gas chromatography, and quantify with external standard method. 7.3 Transesterification method (applies to fats with free fatty acid content of not more than 2 %). DISSOLVE the fat sample in isooctane; ADD potassium hydroxide methanol solution to make the sample methyl-esterified through transesterification. After the reaction is complete, NEUTRALIZE the residual potassium hydroxide with sodium sulfate, and USE external standard method to quantitatively determine the content of fatty acids.

8 Reagents and materials

Unless otherwise stated, the reagents used in this method are analytical regents and the water is the Grade 1 water specified in GB/T 6682. 8.1 Reagents 8.1.1 Hydrochloric acid (HCl). 8.1.2 Ammonia (NH3 · H2O). 8.1.3 Pyrogallic acid (C6H6O3). 8.1.4 Ethyl ether (C4H10O). 8.1.5 Petroleum ether. with a boiling range of 30 °C ~ 60 °C. 8.1.6 Ethanol (C2H6O) (95 %). 8.1.7 Methanol (CH3OH). chromatographically pure. 8.1.8 Sodium hydroxide (NaOH). 8.1.14 Toluene (C7H8). chromatographically pure. 8.1.15 Acetyl chloride (C2H3ClO). 8.1.16 Isooctane [(CH3)2CHCH2C(CH3)3]. chromatographically pure. 8.1.17 Sodium bisulfate (NaHSO4). 8.1.18 Potassium hydroxide (KOH). 8.2 Preparation of reagents 8.2.1 Hydrochloric acid solution (8.3 mol/L). the same as 3.2.1. 8.2.2 Ether-petroleum ether mixture (1 + 1). the same as 3.2.2. 8.2.6 Sodium carbonate solution (6 %). WEIGH 6 g of anhydrous sodium carbonate in a 100-mL flask; ADD water to dissolve; TRANSFER to a 100-mL volumetric flask and DILUTE with water to constant weight. 8.2.7 Potassium hydroxide methanol solution (2 mol/L). the same as 3.2.5. 8.3 Standards 8.4 Preparation of standard solutions 8.4.1 Single fatty acid methyl ester standard solution. the same as 3.4.3.

9 Apparatus and equipment

9.1 Homogenizer or laboratory tissue pulverizer or grinder. 9.2 Gas chromatograph. with a hydrogen flame ion detector (FID). 9.4 Constant temperature water bath. with a temperature range of 40 °C ~ 100 °C, temperature control ± 1 °C. 9.5 Analytical balance. with a division of 0.1 mg. 9.6 Centrifuge. with a speed ≥ 5000r/min. 9.7 Rotary evaporator. 9.8 Screw glass tube (with a screw cap with inner lining made of PTFE). 15 mL. 9.9 Centrifuge tube. 50 mL. ......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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