NITRITES

Nitrite salts (KNO2 and NaNO2) have been used in meat curing for many centuries. Meat curing utilizes salt, sugar, spices, and ascorbate or erythorbate in addition to nitrite. The reported contributions of nitrite to meat curing include characteristic color development, flavor production, texture improvement, and antimicrobial effects (IFT, 1987). The specific contribution of nitrite to the antimicrobial effects of curing salt was not recognized until the late 1920s (NAS/NRC, 1981), and evidence that nitrite was an effective antimicrobial agent came even later (Steinke and Foster, 1951). Nitrites are white to pale yellow hygroscopic crystals that are quite soluble in water and liquid ammonia but much less so in alcohol and other solvents.

The primary use for sodium nitrite as an antimicrobial is to inhibit the growth and toxin production of Clostridium botulinum in cured meats. In association with other components in the curing mix—such as salt, ascorbate, and erythorbate—and pH, nitrite exerts a concentration-dependent antimicrobial effect on the outgrowth of spores from C. botulinum and other clostridia.

The effectiveness of nitrite is dependent upon several environmental factors. Nitrite is most inhibitory to bacteria at an acidic pH. A tenfold increase in the inhibitory effect of nitrite against C. botulinum was found when the pH was reduced from 7.0 to 6.0 (Roberts and Ingram, 1966). Nitrite is more inhibitory under anaerobic conditions (Castellani and Niven, 1955; Lechowich et al., 1956; Buchanan and Solberg, 1972). Temperature, salt concentration, and initial inoculum size also significantly influence the antimicrobial role of nitrite (Riemann et al., 1972; Roberts, 1975; Roberts et al., 1966, 1976; Genigeorgis and Riemann, 1979). Ascorbate and isoascorbate enhance the antibotulinal action of nitrite most likely by acting as reducing agents (Roberts et al., 1991).

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