GB 1886.7-2015
Food additive – Sodium metabisulfite (Sodium Metabisulfite Food Grade)
1. Scope
This standard is applicable to the food additive sodium metabisulfite.
2. Molecular formula and relative molecular weight
2.1 Molecular formula
Na2S2O5
2.2 Relative molecular weight
190.12 (based on the international relative atomic mass of 2017)
3. Technical Requirements
3.1 Sensory requirements
The sensory requirements should comply with the provisions of Table 1.
Table 1 Sensory Requirements
| Item | Requirements | Inspection method |
| Color | White or slightly yellow | Take an appropriate amount of sample and place it in a clean and dry white porcelain plate, and observe its color and state under natural light |
| Form | Crystalline powder |
3.2 Physical and chemical indicators
The physical and chemical indicators should comply with the provisions of Table 2.
Table 2 Physical and Chemical Indicators
| Item | Requirements | Inspection method |
| Content of Sodium Metabisulfite (Na2S2O5), ω/% ≥ | 96.5 | A.4 in Appendix A |
| Fe, ω/% ≤ | 0.003 | A.5 in Appendix A |
| Clarity | Passed testing | A.6 in Appendix A |
| As/(mg/kg) ≤ | 1.0 | GB 5009.76 |
| Heavy metal (Pb) /(mg/kg) ≤ | 5.0 | GB 5009.74 |
Inspection method
A.1 Safety Tips
Some strong acids need to be used in this standard test operation, and caution should be exercised to avoid splashing onto the skin. When using volatile acids, it is necessary to do so in a fume hood.
A.2 General provisions
When no other requirements are specified, the reagents and water used in this standard refer to analytical pure reagents and Grade III water specified in GB/T6682. The standard solutions, impurity standard solutions, formulations, and products required for the experiment shall be prepared in accordance with the provisions of GB/T601, GB/T602, and GB/T603 unless otherwise specified. The solution used in the experiment refers to aqueous solution when no specific solvent is specified for preparation.
A.3 Identification test
A.3.1 Reagents and materials
A.3.1.1 Hydrochloric acid.
A.3.1.2 Dished potassium solution: 360g/L.
A.3.1.3 Hydrochloric acid solution: 1+3.
A.3.1.4 Dish solution: Take 1.4g of the dish and place it in a 10 mL dish of potassium hydroxide solution. Add two drops of hydrochloric acid, dissolve in water, dilute to 100 mL, and store in brown bottle away from light.
A.3.1.5 Nitric acid extraction solution: Take 15g of nitric acid extraction, dissolve it in 90mL of water and 10mL of nitric acid solution (1+9), add one drop of extraction, seal and store in a dark place for future use.
A.3.1.6 Lead wire.
A.3.2 Identification method
A.3.2.1 This product exhibits a sulfite specific reaction
After adding the aqueous solution of the sample to the dish solution, the yellow color fades.
After dripping the aqueous solution of the sample into the hydrochloric acid solution, sulfur dioxide gas escapes. When tested with a test paper soaked in nitric acid solution, it appears black.
A.3.2.2 Sodium salt specific reaction of this product
The lead wire soaked in hydrochloric acid is first burned on a bright flame until bright. Take a small amount of the sample solution and burn it on a bright flame. The flame is bright yellow color.
A.4 Determination of sodium metabisulfite content (calculated as Na2S2O5)
A.4.1 Method Summary
In a weakly acidic solution, sulfite is oxidized to sulfate using a dish. Using starch as an indicator, titrate the excess dish with a sodium thiosulfate standard titration solution.
A.4.2 Reagents and materials
A.4.2.1 Dish standard titration solution:
A.4.2.2 Ice acetic acid solution: 1+3.
A.4.2.3 Sodium thiosulfate standard titration solution: c (Na2S2O3)=0.1 mol/L.
A.4.2.4 Soluble starch solution: 5g/L.
A.4.3 Analysis steps
Transfer 50mL of standard titration solution from a dish and place it in a volumetric flask. Weigh approximately 0.2g of the sample to the nearest 0.0002g, add it to the dish solution, stopper it, seal it with water, and place it in a dark place for 5 minutes. Add 5mL of glacial acetic acid solution and titrate with sodium thiosulfate standard titration solution. Near the endpoint, add 2mL of soluble starch solution and continue titrating until the blue color of the solution disappears.
Simultaneously remove 50mL of the standard titration solution from the dish and perform a blank test under the same conditions.
A.4.4 Result calculation
The mass fraction of sodium metabisulfite content (calculated as Na2S2O5) is calculated according to equation (A.1):
In the equation:
c – concentration of sodium thiosulfate standard titration solution, in moles per liter (mol/L);
V0– The volume of sodium thiosulfate standard titration solution consumed in the blank test, in milliliters (mL);
V1– The volume of sodium thiosulfate standard titration solution consumed in the titration test solution, in milliliters (mL);
M-Molar mass of sodium metabisulfite, unit: g/mol, 
m – Mass of the sample, in grams (g);
1 000- Conversion coefficient.
The test results shall be subject to the arithmetic mean of the parallel measurement results. Absolute difference between two independent measurements obtained under repeatability conditions not more than 0.2%.
A.5 Determination of iron content
A.5.1 Method Summary
Same as the 3rd edition of GB/T3049-2006,
A.5.2 Reagents and Solutions
Same as the 4th edition of GB/T3049-2006.
A.5.3 Instrument and equipment
Same as the 5th edition of GB/T3049-2006.
A.5.4 Analysis steps
A.5.4 .1 Draw the working curve.
According to the regulations in GB/T3049-2006, use a colorimetric dish with an optical path of 1cm and the corresponding amount of iron standard solution to draw the work curve.
A.5.4 .2 Preparation of test solution
Weigh approximately 5g of the sample to the nearest 0.01g. Place in a 250mL tall beaker, dissolve with a small amount of water, add 25mL of hydrochloric acid solution, and steam and dry in a boiling water bath. Dissolve the residue with water, transfer all into a 250 mL volumetric flask, dilute with water to the scale, and shake up.
A.5.4.3 Preparation of blank test solution
In a 250mL high beaker, add a small amount of water, then add 25mL of hydrochloric acid, evaporate to dryness in a boiling water bath, dissolve the residue in water, and transfer it all in dilute with water to the scale in a 250mL volumetric flask and shake well.
A.5.4.4 Determination
Use a pipette to take 50mL of test solution and blank test solution and put them into a 100mL volumetric flask respectively, according to GB/T3049-2006, the operation should start from “adding water to 60mL when necessary”.
A.5.5 Result calculation
The mass fraction of iron (Fe) ω2 is calculated according to equation (A.2):
In the equation:
m2- The mass of iron in the test solution obtained from the working curve, in milligrams (mg);
m3- The mass of iron in the blank test solution obtained from the working curve, in milligrams (mg);
m1- Mass of the sample, in grams (g);
50- Volume of the test solution taken, in milliliters (mL);
250- Total volume of the test solution, in milliliters (mL);
1000- Conversion coefficient.
The test results shall be subject to the arithmetic mean of the parallel measurement results. The absolute difference between the two independent measurement results obtained under repeatability conditions is not more than 0.0005%.
1.6 Determination of clarity
A.6.1 Reagents and materials
A.6.1.1 Hydrochloric acid standard solution: H (HCl)=0.1mol/L.
A.6.1.2 Nitric acid solution: 1+3.
A.6.1.3 Silver nitrate solution: 20g/L.
A.6.1.4 Soluble starch solution: 20g/L.
A.6.1.5 Standard stock solution for turbidity measurement: 1mL of solution contains 1mg of chlorine (Cl).
Take 14.1mL of hydrochloric acid standard solution, put it into a thousand 50mL volumetric flask, dilute it to the scale, and shake it well.
A.6.1.6 Standard solution for turbidity measurement: 1mL of solution contains 0.01mg of chlorine (Cl).
Take 1mL of standard stock solution for turbidity measurement, place it in a 10mL volumetric flask, dilute it to the scale, and shake it well.
A.6.2 Analysis steps
Weigh 0.50g ± 0.001g of the sample, place it in a 25mL colorimetric tube, and dissolve it in 10mL of water. The turbidity of the test solution should be lower than the standard ratio turbid solution.
Standard turbidimetric solution: Take 1.2mL of the standard solution for turbidity measurement, place it in a 25mL colorimetric tube, add water to 20mL, add 1mL of nitric acid solution, 0.2mL of soluble starch solution, and 1mL of silver nitrate solution, shake well, and let it stand for 15 min.
For more information, pls view:
Sodium Metabisulfite Technical Grade TDS
