GB Translated English of Chinese Standard: GB NATIONAL STANDARD OF THE

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1 Translated English of Chinese Standard: GB Buy True-PDF Auto-delivery. GB NATIONAL STANDARD OF THE PEOPLE S REPUBLIC OF CHINA GB National Food Safety Standard - Determination of Peroxide Value in Foods 食品安全国家标准食品中过氧化值的测定 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 Buy True-PDF Auto-delivery. Page 1 of 13

2 Table of Contents Foreword Scope... 4 Method I Titration Principle Reagents and Materials Instruments and Equipment Analytical Procedures Expression of Analysis Results Precision... 9 Method II Potentiometric titration Principle Reagents and Materials Instruments and Equipment Analytical Procedures Expression of Analysis Results Precision Buy True-PDF Auto-delivery. Page 2 of 13

3 National Food Safety Standard - Determination of Peroxide Value in Foods 1 Scope This Standard specifies two methods of determining peroxide value in foods: titration and potentiometric titration. In this Standard, Method I is applicable to edible animal and vegetable fats and oils, and edible oil products, as well as food processed through deep-frying, puffing, baking, modulating and frying from plant-based food as the raw material, such as wheat flour, cereal and nut, etc.; food processed through quick freezing, dry-cure and pickling from animal-based food as the raw material. Method II is applicable to animal and vegetable fats, and margarine, and the range of measurement is 0 g/100 g ~ 0.38 g/100 g. This Standard is not applicable to the determination of embedded oil and fat products, for example, non-dairy creamer. 2 Principle Method I -- Titration The prepared oil and fat sample dissolves in chloroform and glacial acetic acid, the contained peroxide reacts with potassium iodide and generates iodine. Use sodium thiosulfate standard solution to titrate the precipitated iodine. Use an equivalent mass fraction of iodine in peroxide or the mmol number of reactive oxygen in 1 kg of sample to represent the peroxide value. 3 Reagents and Materials Unless otherwise indicated, the reagents adopted under this method are of analytical purity. The water is third-grade water as specified in GB/T Reagents Glacial acetic acid (CH 3 COOH) Chloroform (CHCl 3 ) Potassium iodide (KI). Buy True-PDF Auto-delivery. Page 4 of 13

4 and layering. Use quick qualitative filter paper to filter the oil layer to beaker. The filtrate in the beaker is the sample to be tested. The prepared sample shall be clarified for testing. Immediately take the sample and determine it while the sample is still liquid Food processed through deep-frying, puffing, baking, modulating and frying from plant-based food as the raw material, such as wheat flour, cereal and nut Take edible part of representative sample from all the samples, grind it in a glass mortar; place the grinded sample in a wide-mouth bottle, add petroleum ether (3.2.4) at two to three times the volume of the sample; shake it and mix it up thoroughly, place it evenly; start extraction for over 12 h. Use a funnel that holds anhydrous sodium sulfate to filter it, and take the filtrate. Adopt rotary evaporator to decompress and dry petroleum ether in water bath at below 40 C. The remaining becomes the sample to be tested Food processed through quick freezing, dry-cure and pickling from animal-based food as the raw material Take edible part of representative sample from all the samples, grind it and thoroughly mix it up; place the grinded sample in a wide-mouth bottle, add petroleum ether (3.2.4) at two to three times the volume of the sample; shake it and mix it up thoroughly, place it evenly; start extraction for over 12 h. Use a funnel that holds anhydrous sodium sulfate to filter it, and take the filtrate. Adopt rotary evaporator to decompress and dry petroleum ether in water bath at below 40 C. The remaining becomes the sample to be tested. 5.2 Determination of Samples The determination of samples shall avoid direct sunlight. Weigh-take 2 g~3 g (accurate to g) of the sample prepared in 5.1.1~5.1.4, place it in 250 ml iodine volumetric flask, add 30 ml of trichloroethane-glacial acetic acid mixed solution; slightly shake it to thoroughly dissolve the sample. Accurately add 1.00 ml of saturated potassium iodide solution and tightly plug it, then, slightly shake it for 0.5 min; place it in the dark for 3 min. Take it out and add 100 ml of water, shake it up; immediately use sodium thiosulfate standard solution (when the estimated peroxide value is 0.15 g/100 g, use mol/l standard solution; when the estimated peroxide value is >0.15 g/100 g, use 0.01 mol/l standard solution) to titrate the precipitated iodine, till it turns yellowish; add 1 ml of starch indicator, continue the titration and strongly shake the solution till blue vanishes. Meanwhile, conduct a blank test. The volume V 0 of 0.01 mol/l sodium thiosulfate solution consumed in the blank test shall be 0.1 ml. Buy True-PDF Auto-delivery. Page 7 of 13

5 c - The concentration of sodium thiosulfate standard solution, expressed in (mol/l); m - The mass of sample, expressed in (g); 1,000 - Conversion factor. The calculation result shall be expressed as the arithmetic mean value of the result of two independent determinations obtained under repeatability conditions. The result shall retain two significant figures. 7 Precision The absolute difference between the two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean value. 8 Principle Method II -- Potentiometric titration The prepared oil and fat sample dissolves in isooctane and glacial acetic acid, the contained peroxide reacts with potassium iodide and generates iodine. Use sodium thiosulfate standard solution to titrate the precipitated iodine; use potentiometric titrator to determine the terminal of titration. Use an equivalent mass fraction of iodine in peroxide or the mmol number of reactive oxygen in 1 kg of sample to represent the peroxide value. 9 Reagents and Materials Unless otherwise indicated, the reagents adopted under this method are of analytical purity. The water is third-grade water as specified in GB/T Reagents Glacial acetic acid (CH 3 COOH) Isooctane (C 8 H 18 ) Potassium iodide (KI) Sodium thiosulfate (Na 2 S 2 O 3. 5H 2 O) Potassium dichromate (K 2 Cr 2 O 7 ): working reference reagent. 9.2 Preparation of Reagents Buy True-PDF Auto-delivery. Page 9 of 13

6 Weigh-take 5 g (accurate to g) of oil and fat sample that s prepared in 5.1.1~5.1.2 and place it in a titration cup of potentiometric titrator; add 50 ml of isooctane-glacial acetic acid mixed solution, slightly shake the sample to thoroughly dissolve it. If the sample manifests relatively poor solubility (for example, stearin or animal fat), add 20 ml of isooctane to the titration cup first; slightly shake the sample to dissolve it; add 30 ml of glacial acetic acid, then, mix it up. Accurately add 0.5 ml of saturated potassium iodide solution to the titration cup, then, activate magnetic stirrer; react for 60 s ± 1 s at an appropriate stirring speed. Immediately add 30 ml~100 ml of water to the titration cup, insert electrode and titration head, set titration parameter, start the procedure of titration; adopt the mode of dynamic titration to titrate, and observe titration curve and potential change; the amount of added sodium thiosulfate standard solution shall be controlled between 0.05 ml/drop~0.2 ml/drop. After reaching the terminal of titration, record the volume V of consumed standard solution at the terminal. After completing the titration of a sample, soak the stirrer or stirring magnet, titration head and electrode in isooctane to rinse grease on the surface. Meanwhile, conduct a blank test. Adopt the mode of monotonic titration for titration, and observe titration curve and potential change; the amount of added sodium thiosulfate standard solution shall be controlled at ml/drop. After reaching the terminal of titration, record the volume V 0 of consumed standard solution at the terminal. The volume V 0 of 0.01 mol/l sodium thiosulfate standard solution consumed in the blank test shall not exceed 0.1 ml. Note 1: guarantee that the sample is thoroughly mixed and no bubble is generated to affect electrode response. Select an appropriate stirring speed in accordance with the guidance by instrument manual. Note 2: adjust the amount of added water in accordance with the instrument; this amount will affect starting potential, but will not affect the result of determination. The titrated phase is on the bottom layer, and a great deal of water is conducive to phase conversion. More added water signifies a more significant potential difference between the starting titration point and terminal titration point, and more obvious inflection point on the titration curve. Note 3: sample determination shall avoid direct sunlight. 12 Expression of Analysis Results 12.1 When an equivalent mass fraction of iodine in peroxide is adopted to signify peroxide value, it shall be calculated in accordance with Formula (3): Buy True-PDF Auto-delivery. Page 11 of 13