sodium hydrogen sulfate, Summaries of Chemistry

Download sodium hydrogen sulfate and more Summaries Chemistry in PDF only on Docsity! Page 1 of 3 SODIUM HYDROGEN SULFATE Chemical and Technical Assessment (CTA) Prepared by Madduri V. Rao, Ph.D. 1. Summary At the seventy-first meeting of JECFA, the Committee evaluated the safety, dietary intake and revision of specifications of sodium hydrogen sulfate (NaHSO4) at the request of the Codex Committee on Food Additives for its use as an acidifier. The Committee, at its sixty-eighth meeting (FAO/WHO, 2007), established specifications for sodium hydrogen sulfate for use in the preparation of acidified sodium chlorite, an antimicrobial washing solution. Sodium hydrogen sulfate, when added to food products containing water, ionizes to sodium ions, hydrogen ions, and sulfate ions. Since Acceptable Daily Intakes (ADIs) have been previously established for these ions, sodium hydrogen sulfate was not evaluated at the sixty-eighth meeting of the Committee. This document summarizes chemical and technical information on sodium hydrogen sulfate, partly based on information submitted by Jones- Hamilton Co.1. 2. Description Sodium hydrogen sulfate (NaHSO4, CAS No. 7681-38-1) is a colourless crystalline compound which is freely soluble in water. Sodium hydrogen sulfate, when added to food products containing water, ionizes to sodium ions, hydrogen ions, and sulfate ions. In addition to its use as an acidifier in foods (including its use in the preparation of acidified sodium chlorite), it also is used as an acidifier in pet foods, for pH control in swimming pools and SPAs, for ammonia control in livestock operations, and as an acid-type cleaner for commercial purposes. 3. Methods of Manufacture Sodium chloride and sulfuric acid are the starting materials in the manufacture of sodium hydrogen sulfate. Sodium chloride is first dissolved in water and then re-crystallized to produce a food- grade salt. Sulfuric acid is obtained from the roasting of natural sulfur-containing ores, resulting in the production of sulfur oxides that are dissolved in water to produce sulfuric acid. The salt and sulfuric acid are combined at elevated temperatures to produce molten sodium hydrogen sulfate according to the following reaction: Once the reaction is complete, the molten sodium hydrogen sulfate is sprayed and cooled in order to form a solid beaded product. The final product is inspected for consistent particle size and packed in appropriate containers. 4. Chemical Characterization 4.1 Composition In commercial products, sodium hydrogen sulfate is present at levels ranging between 85.4 and 95.2%. The purity of sodium hydrogen sulfate is further ensured by limiting the content of water insoluble matter. 1 JONES-HAMILTON CO., 30354, Tracy Rd., Walbridge, OH 43465, United States of America. NaCl + H2SO4 Heat NaHSO 4 + HCl Page 2 of 3 4.2 Possible impurities Levels of lead and selenium occurring in the final product are as a result of their occurrence in the starting materials, obtained from natural sources, and are limited by the specifications parameters which indicate the limits of not more than 2 and 5 mg/kg, respectively. 4.3 Rationale for proposed specifications Three non-consecutive lots of sodium hydrogen sulfate were tested to verify that the manufacturing process produces a consistent product that falls within the limits of the proposed specifications. Results of the analysis are presented in Table 1. The analytical data demonstrates that the manufacturing process consistently produces a uniform final product. Moreover, the proposed specifications for sodium hydrogen sulfate are supported by the results of the analysis of the composition of these lots. The proposed specifications were in harmony with other regional and national specifications and with the limits in the JECFA specifications monograph for sodium hydrogen sulphate prepared at the sixty-eighth meeting of the Committee. Table 1. Analytical results for 3 batches of sodium hydrogen sulfate Test Lot 1 Lot 2 Lot 3 Assay (% as NaHSO4) 93.8 94.0 93.8 Lead (mg/kg) <0.5 <0.5 <0.4 Loss on drying (%) 0.4 0.16 <0.14 Selenium (mg/kg) 0.3 <1.0 <2.0 Water-insoluble substances (%) 0.019 <0.05 <0.05 4.4 Analytical methods The majority of analytical methods used are the standard test methods, published in the Combined Compendium of Food Additive Specifications (FAO JECFA Monographs 1, Volume 4, 2006). Other methods are based on the Food Chemicals Codex (FCC, 2008) and the British Pharmacopoeia (BP, 2007). 5. Functional uses 5.1 Technological functions Sodium hydrogen sulfate, when added to food products containing water, first ionizes to sodium and hydrogen sulfate ions. Hydrogen sulfate ion further dissociates in water to sulfate and hydronium ions. NaHSO4 Na+ + HSO4 - HSO4 - + H2O H3O+ + SO4 -2 Sodium hydrogen sulfate can be used as an acidifier in foods as well as in the preparation of acidified sodium chlorite, an antimicrobial washing solution. The pKa values of various food acids are given below. Compound pKa value Sodium hydrogen sulfate 1.99 Phosphoric Acid (pKa1) 2.16 Lactic Acid 3.08 Citric Acid (pKa1) 3.14 Malic Acid (pKa1) 3.40 Acetic Acid 4.75