The function and detection method of sodium metabisulfite in other fields

The role of sodium metabisulfite in other fields

This product is used as a raw material in perfumes, pigments and industrial products. It is used as a dissolving agent for leather tannin (same as sodium sulfite), an additive for washing image fixing solution (to prevent the decomposition of sea wave), and a stabilizer for washing image developing solution ( Prevent air oxidation) etc.

In the Chinese food industry, sodium metabisulfite is a widely used food additive. The key to the role of this substance is to form sulfurous acid. Sulfurous acid is a strong reducing agent. When it is oxidized, it can reduce the coloring material and reduce its color. Food maintains a bright color and can inhibit oxidase in food to prevent food from spoiling; in addition, due to its reducing effect, it can block the normal physiological oxidation process of microorganisms and inhibit the reproduction of microorganisms, thereby playing a preservative role. Therefore, sodium metabisulfite is a commonly used bleaching agent and preservative in the processing of agricultural products.

Detection method

The detection methods of sodium metabisulfite currently mainly include the para-nitroaniline hydrochloride method, distillation method, ion chromatography and iodometric method. A large number of toxic reagents are needed for the paraben aniline hydrochloride method; the detection process of the distillation method is complicated and takes a long time; the ion chromatography method has high technical requirements for detection equipment and detection personnel, and the detection period is long and the detection cost is high. The above three detection methods are not suitable for the rapid detection of the agricultural products wholesale market at this stage, so this station is now using on-site rapid detection kit for sulfur dioxide (iodometric method).

The rapid test box is developed according to the national standard GB/T5009.3-2003 ((Determination of sulfite in food). Its principle is that sulfite and sulfur dioxide in food can quickly react with this reagent to generate a purple product. The darker the color, the higher the content of sulfur dioxide or sulfite in the sample. Using a visual colorimetric analysis method, compared with the standard color scale, you can get a semi-quantitative result of the sulfite in the sample. It is convenient to use and can be carried around. Carrying, real-time on-site detection, fast detection speed (10 ~ 15 min), low sample and reagent consumption, no pollution, etc., broad application prospects. The detection steps are as follows:

(1) Weigh 1 g of sample with a balance and cut it into small pieces as much as possible, and put it in the sample cup; add 10 ml of distilled water or purified water with a plastic graduated pipette and place it for more than 10 min. Stir or shake with a pipette. Accelerated extraction, the supernatant is the sample solution.

(2) Add 2 drops of test solution A and 1 drop of test solution B to the wells of the porous colorimetric tube, mix well; then add 0.5 mI of sample solution with a 3 mI pipette, mix by stirring or shaking. Place it for 2 minutes to observe the color change and compare it with the color chart. Judgment of the results: Observe the depth of the color in the well after 2 minutes. If the color of the sample liquid shows obvious purple or purple red, the content of sulfur dioxide in the sample can be known from the value indicated on the control color card.