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The chemistry & mode of action of acidified sodium chlorite |
C. C. WARF, JR., Alcide Corp., 8561 154th Ave. N.E., Redmond, WA 98052 and G. K. Kemp, Alcide Corporation, 8561 154th Avenue NE, Redmond, WA 98052. Acidified Sodium Chlorite (ASC) is approved by the FDA (21 CFR 173.325) as a ‘secondary direct food additive permitted in food for human consumption’ specifically as an antimicrobial intervention treatment for poultry carcasses, poultry carcass parts, red meat carcasses, red meat parts and organs, seafood, and raw agricultural commodities. ASC is often confused with chlorine dioxide (ClO2), also approved by the FDA (21 CFR 173.300) as a secondary direct food additive largely because solutions ASC can, under certain conditions, generate small quantities of chlorine dioxide. However, by judicious selection of reaction parameters (nature and concentration of activating acid, chlorite concentration, catalysts, total titratable acidity) chlorine dioxide formation is typically minimized in true ASC solutions. ASC is a highly effective, broad spectrum antimicrobial, which is produced by lowering the pH of a solution of sodium chlorite into the 2.5 to 3.2 range with any GRAS acid. ASC chemistry is principally that of chlorous acid (HClO2), which is the metastable oxychlorine species, which forms on acidification of chlorite. Once formed, chlorous acid gradually decomposes to form chlorate ion, chlorine dioxide, and chloride ion. It is hypothesized that the mode of action of ASC derives from the uncharged chlorous acid, which is able to penetrate bacterial cell walls and disrupt protein synthesis by virtue of its reaction with sulfhydryl, sulfide, and disulfide containing amino acids and nucleotides. The undissociated acid is thought to facilitate proton leakage into cells and thereby increase energy output of the cells to maintain their normal internal pH thereby also adversely affecting amino acid transport. Iodometric titration and UV spectroscopic methods must be used to allow an accurate determination of the active concentrations present in an ASC solution and to differentiate them from typical chlorine dioxide generating systems.
Session 91, Acidified sodium chlorite - an antimicrobial intervention for the food industry
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