GB 5009.227-2016

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GB 5009.227-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard -
Determination of Peroxide Value in Foods
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 
Method I Titration ... 4 
2 Principle ... 4 
3 Reagents and Materials ... 4 
4 Instruments and Equipment ... 6 
5 Analytical Procedures ... 6 
6 Expression of Analysis Results ... 8 
7 Precision ... 9 
Method II Potentiometric titration ... 9 
8 Principle ... 9 
9 Reagents and Materials ... 9 
10 Instruments and Equipment ... 10 
11 Analytical Procedures ... 10 
12 Expression of Analysis Results ... 11 
13 Precision ... 13 
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.
Method I -- Titration
2 Principle
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 6682.
3.1 Reagents
3.1.1 Glacial acetic acid (CH3COOH).
3.1.2 Chloroform (CHCl3).
3.1.3 Potassium iodide (KI).
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.
5.1.3 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.
5.1.4 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 0.001 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 0.002 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 V0 of 0.01 mol/L sodium thiosulfate solution consumed in the blank
test shall be ≤ 0.1 mL.
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.
Method II -- Potentiometric titration
8 Principle
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 6682.
9.1 Reagents
9.1.1 Glacial acetic acid (CH3COOH).
9.1.2 Isooctane (C8H18).
9.1.3 Potassium iodide (KI).
9.1.4 Sodium thiosulfate (Na2S2O3.5H2O).
9.1.5 Potassium dichromate (K2Cr2O7). working reference reagent.
9.2 Preparation of Reagents
Weigh-take 5 g (accurate to 0.001 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 0.005 mL/drop. After reaching the
terminal of titration, record the volume V0 of consumed standard solution at the
terminal. The volume V0 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).