1 Scope
This standard specifies the methods for determination of fatty acid in foods.
This standard is applicable to the determination of total fat, saturated fat and unsaturated fat in foods.
In this standard, hydrolysis-extraction method is applicable to the determination of fatty acid content in foods; trans-esterification method is applicable to the determination of fatty acid content of grease fat sample with free fatty acid content not greater than 2%; acetyl chloride-methanol method is applicable to the determination of fatty acid content of milk powder and anhydrous butter sample with moisture content less than 5%.
Method I Internal Standard Method
2 Theory
2.1 Hydrolysis-extraction method: after hydrolysis of test sample with internal standard, fat in the sample is extracted by diethyl ether solution, and then saponification of fat and esterification of fatty acid can be carried out under alkaline conditions to produce fatty acid methyl ester; after gas chromatography with capillary column, the quantitative determination of fatty acid methyl ester content can be carried out by internal standard method. The content of total fat, saturated fat (acid), monounsaturated fat (acid) and polyunsaturated fat (acid) can be calculated according to the content of all kinds of fatty acid methyl ester and conversion factor.
Fat extraction may be omitted for test sample of animal and vegetable fats and oils, directly carry out saponification of fat and esterification of fatty acid.
2.2 Trans-esterification method (applicable to grease with free fatty acid content not greater than 2%): dissolve grease in isooctane, add internal standard; add potassium hydroxide and methanol solution for trans-esterification; for the purpose of avoid saponification of methyl ester, neutralize the residual potassium hydroxide with sodium hydrogen sulfate after reacted entirely.
3 Reagents and Materials
1 Scope
This standard specifies the methods for determination of fatty acid in foods.
This standard is applicable to the determination of total fat, saturated fat and unsaturated fat in foods.
In this standard, hydrolysis-extraction method is applicable to the determination of fatty acid content in foods; trans-esterification method is applicable to the determination of fatty acid content of grease fat sample with free fatty acid content not greater than 2%; acetyl chloride-methanol method is applicable to the determination of fatty acid content of milk powder and anhydrous butter sample with moisture content less than 5%.
Method I Internal Standard Method
2 Theory
2.1 Hydrolysis-extraction method: after hydrolysis of test sample with internal standard, fat in the sample is extracted by diethyl ether solution, and then saponification of fat and esterification of fatty acid can be carried out under alkaline conditions to produce fatty acid methyl ester; after gas chromatography with capillary column, the quantitative determination of fatty acid methyl ester content can be carried out by internal standard method. The content of total fat, saturated fat (acid), monounsaturated fat (acid) and polyunsaturated fat (acid) can be calculated according to the content of all kinds of fatty acid methyl ester and conversion factor.
Fat extraction may be omitted for test sample of animal and vegetable fats and oils, directly carry out saponification of fat and esterification of fatty acid.
2.2 Trans-esterification method (applicable to grease with free fatty acid content not greater than 2%): dissolve grease in isooctane, add internal standard; add potassium hydroxide and methanol solution for trans-esterification; for the purpose of avoid saponification of methyl ester, neutralize the residual potassium hydroxide with sodium hydrogen sulfate after reacted entirely.
3 Reagents and Materials
