§ 172.133 Dimethyl dicarbonate.
Dimethyl dicarbonate （CAS Reg. No. 4525–33–1） may be safely used in food in accordance with the following prescribed conditions:
（a） The additive meets the following specifications:
?。?） The additive has a purity of not less than 99.8 percent as determined by the following titration method:
principles of method
Dimethyl dicarbonate （DMDC） is mixed with excess diisobutylamine with which it reacts quantitatively. The excess amine is backtitrated with acid.
apparatus
250-milliliter （mL） Beaker
100-mL Graduate cylinder
25-mL Pipette
10-mL Burette （automatic, eg., Metrohm burette）
Stirrer
Device for potentiometric titration
Reference electrode
Glass electrode
reagents
Acetone, analytical-grade
Solution of 1 N diisobutylamine in chlorobenzene, distilled
1 N Acetic Acid
procedure
Accurately weigh in about 2 grams of the sample （W） and dissolve in 100 mL acetone. Add accurately 25 mL of the 1 N diisobutylamine solution by pipette and allow to stand for 5 minutes. Subsequently, titrate the reaction mixture potentiometrically with 1 N hydrochloric acid （consumption= a mL） while stirring. For determining the blank consumption, carry out the analysis without a sample （consumption= b mL）.
calculation
Note: For adding the diisobutylamine solution, always use the same pipette and wait for a further three drops to fall when the flow has stopped.
?。?） The additive contains not more than 2,000 ppm （0.2 percent） dimethyl carbonate as determined by a method entitled “Gas Chromatography Method for Dimethyl Carbonate Impurity in Dimethyl Dicarbonate,” which is incorporated by reference in accordance with 5 U.S.C. 552（a）. Copies are available from the Center for Food Safety and Applied Nutrition （HFS–200）, 5100 Paint Branch Pkwy., College Park, MD 20740, or at the National Archives and Records Administration （NARA）. For information on the availability of this material at NARA, call 202–741–6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.
?。╞） The additive is used or intended for use as a microbial control agent in the following beverages under normal circumstances of bottling, canning, or other forms of final packaging, where the viable microbial load has been reduced to 500 microorganisms per milliliter or less by current good manufacturing practices such as heat treatment, filtration, or other technologies prior to the use of dimethyl dicarbonate:
?。?） In wine, dealcoholized wine, and low alcohol wine in an amount not to exceed 200 parts per million.
（2） In ready-to-drink teas in an amount not to exceed 250 parts per million.
?。?） In carbonated or noncarbonated, nonjuice-containing （less than or equal to 1 percent juice）, flavored or unflavored beverages containing added electrolytes （5–20 milliequivalents/liter sodium ion （Na+） and 3–7 milliequivalents/liter potassium ion （K+）） in an amount not to exceed 250 parts per million.
（4） In carbonated, dilute beverages containing juice, fruit flavor, or both, with juice content not to exceed 50 percent, in an amount not to exceed 250 parts per million.
?。╟） To ensure the safe use of the food additive, the label of the package containing the additive shall bear, in addition to other information required by the Federal Food, Drug, and Cosmetic Act:
?。?） The name of the additive “dimethyl dicarbonate.”
（2） The intended use of the additive.
（3） Adequate directions for use to ensure compliance with this section.
[53 FR 41329, Oct. 21, 1988, as amended at 58 FR 6091, Jan. 26, 1993; 59 FR 5319, Feb. 4, 1994; 61 FR 14245, Apr. 1, 1996; 61 FR 26788, May 29, 1996; 66 FR 13653, Mar. 7, 2001]
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