GB 5009.227-2023 National food safety standard-Determination of peroxide value in foods
1 Scope
This standard specifies the determination methods of peroxide value in foods.
Method I is applicable to the determination of peroxide value in foods.
Method II is applicable to the determination of peroxide value in edible animal and vegetable fats and oils as well as margarine.
Method I Indicator titration method
2 Principle
The fat and oil specimen prepared will be dissolved in trichloromethane-glacial acetic acid mixed solution, during which the peroxide will react with potassium iodide to produce iodine that will be titrated by sodium thiosulfate standard titration solution. The amount of peroxide value shall be expressed by the mass fraction of the peroxide equivalent to iodine or the mill mole quantity of the active oxygen in 1kg of the sample.
3 Reagents and materials
Unless otherwise specified, only analytically-pure reagents and Class III water (defined in GB/T 6682) are adopted for the purpose of this method.
3.1 Reagents
3.1.1 Glacial acetic acid (CH3COOH).
3.1.2 Trichloromethane (CHCl3).
3.1.3 Potassium iodide (KI).
3.1.4 Petroleum ether: with a boiling range of 30℃ to 60℃.
Determination of petroleum ether: take 100mL of petroleum ether into a rotary distillation flask, then evaporate it to dryness with a rotary evaporator under reduced pressure in the water bath with the temperature not higher than 40℃. Wash the rotary distillation flask with 30mL of trichloromethane-glacial acetic acid mixed solution by several times and merge the washing solutions into a 250mL iodine flask. Put in exact 1.00mL of saturated potassium iodide solution, plug up the bottle cover, gently shake for 0.5min and place it in the dark for 3min, after which add into 1.0mL of the starch indicator and mix well. If it doesn't turn blue, the petroleum ether can be used for specimen preparation; and if blue appears after it is mixed well with 1.0mL of the starch indicator, the reagent shall be replaced.
3.1.5 Anhydrous sodium sulfate (Na2SO4).
3.1.6 Soluble starch.
3.1.7 Acetone (CH3COCH3).
3.1.8 Amylase (CAS No.: 9000-92-4): enzyme activity ≥ 2,000U/g.
3.1.9 Papain (CAS No.: 9001-73-4): enzyme activity ≥ 6,000U/mg.
3.1.10 Sodium thiosulfate (Na2S2O3·5H2O).
3.2 Preparation of reagents
3.2.1 Trichloromethane-glacial acetic acid mixed solution (2+3): mix trichloromethane and glacial acetic acid according to a volume ratio of 2:3.
3.2.2 Starch indicator (10 g/L): weigh 1g of the soluble starch, add about 5mL of water to make it into paste, pour into 95mL of boiling water while stirring, then boil for 1min to 2min, and then cool it down. Prepare it immediately before use.
3.2.3 Potassium iodide saturated solution: weigh about 16g of potassium iodide, put in 10mL of cooled water which is newly boiled, shake up and store in the brown bottle which shall be kept in a dark place for standby. Ensure that saturated potassium iodide crystallization exists in the solution. If exceeding the blank volume requirements in 5.2, re-prepare the solution.
3.3 Preparation of standard solutions
Foreword i
1 Scope
2 Principle
3 Reagents and materials
4 Instruments and apparatus
5 Analysis steps
6 Expression of analysis results
7 Accuracy
8 Principle
9 Reagents and materials
10 Instruments and apparatuses
11 Analysis steps
12 Expression of analysis results
13 Accuracy
