Regarding the problem of adding whitening agent (benzoyl peroxide) to flour on the market, which harms consumers, some people have discussed the method of determining the whitening agent of flour benzoyl peroxide. Here we introduce the sample pretreatment process.
1. Introduction of Benzoyl Peroxide Benzoyl peroxide is a modifier and whitening agent of wheat flour widely used at home and abroad. Its use can increase the whiteness of flour by one grade, and can improve flour gluten and color, which brings obvious economic benefits, so benzoyl peroxide is a food additive commonly used by many wheat flour production enterprises. But adding too much benzoyl peroxide can cause damage to human health.
China stipulates that the maximum allowable addition amount of benzoyl peroxide is 0.06g / kg. In the standard of "Determination of Benzoyl Peroxide in Wheat Flour", two methods using gas chromatography to detect benzoyl peroxide are mentioned. The sample preparation method of the second method is simple and suitable for the determination of small batch samples. Introduce below.
Second, the test instrument
1. Vertical Oscillator
2. Constant temperature water bath shaker
3. Filter
4. Vacuum pump 3. Sample preparation process
(1) Principle The carbamoyl peroxide in wheat flour is reduced to benzoic acid under the condition of acid petroleum ether (500ml petroleum ether with 15ml glacial acetic acid, this condition is close to stomach acid), then extracted with a solvent to constant volume and then used gas chromatography Perform qualitative and quantitative determination.
(2) Processing steps Weigh 5.00g of the sample in a stoppered triangular flask, add 30ml of acidic petroleum ether and stirring block, vigorously oscillate in a vertical shaker to disperse the sample, put it in a 30 ℃ constant temperature water bath shaker, every Shake once every 15 minutes. After 4 hours, the sample solution was quickly filtered with a filter, the filtrate was filtered into a 50ml volumetric flask, the residual sample in the triangular flask was washed with acid petroleum ether, and the filtrate was collected in the volumetric flask. Finally, use acidic petroleum ether to make volume. This is the measurement solution for chromatographic analysis.
This method only occupies a certain advantage in the pretreatment process, but it is known through experiments that its accuracy and repeatability have certain errors, and it is greatly affected by the solvent, so it is not recommended. In addition, when using the second method, a peak of glacial acetic acid appears during the peak period of benzoic acid, which seriously affects the accuracy of the measurement results.
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