T/CQYX 001-2023 The determination of iodine in flavouring salt

Scope

Main technical content: The detection method described in this document involves pretreating flavor edible salt samples. During the pretreatment process, sodium hydroxide is added as an iodine protection reagent. The samples are subjected to low-temperature carbonization and high-temperature ashification to convert organic matter in the samples into inorganic matter, eliminating the influence of organic matter on the determination of iodine content in the samples. Then, the titration detection of the samples is carried out according to the oxidation-reduction titration method in GB 5009.42 "Food Safety National Standard - Determination of Indicators for Edible Salt". The key steps of the detection method are as follows: 1. The main component of flavor edible salt is NaCl. To ensure that no other cations interfere with the detection during the experiment, sodium hydroxide, an alkaline reagent with Na+ as the cation, is selected as the iodine protection reagent to protect iodine from volatilizing at high temperatures. 2. High-temperature ashification is used to convert organic matter in the samples into inorganic matter, eliminating the interference of organic active substances in the detection. 3. For samples with a large amount of additives, there will be more insoluble substances after ashification. To eliminate the influence of color judgment on the titration endpoint, filtering operations are required during the sample preparation process. 4. Under acidic conditions, iodine ions in the samples are oxidized to iodate by sodium hypochlorite. Oxalic acid removes excess sodium hypochlorite, and iodate oxidizes potassium iodide to release elemental iodine. Starch solution is used as an indicator, and the iodine content is calculated by titrating with sodium thiosulfate standard solution.

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