Chemical Inhibition Free Radical Effect

When the antioxidants were used in the cooked/stored samples, data indicated that they were very effective in inhibiting lipid oxidation and MFD. The chemical and off-flavor indicators were reduced and the on-flavor notes were increased. Thus, phenolic-type primary antioxidants that function as free radical scavengers are very effective tools for preventing lipid oxidation and MFD in ground beef. It should also be noted that the intensity of the desirable flavor notes remained at very high levels, which meant that the patties retained their beefy tastes. Therefore, for an antioxidant to be highly effective, it should not only prevent lipid oxidation, but it should also retain the desirable flavor properties of the food commodity. 

It has been apparent for some time that the inhibition of sulfite autoxidation by organic compounds is due to their reactions with free radical intermediates. Further, it seems likely that the chemical effects associated with S02 autoxidation are due to these radicals or, possibly, peroxymonosulfate. Now that the reactivities of the likely free radical intermediates are known, the mechanism of these effects can be begun to be understood. For many organic compounds, like hydroquinone and other phenolic species, reaction with S03 and SO " is possible. Indeed, they prove to be the most efficient inhibitors of S02 autoxidation and the order of... 

Inhibition [77]. An inhibitor is itself being consumed as it traps free radicals. To be effective, it must therefore be present in an excess over the initiator. In practice, this limits effective inhibition to chain reactions apt to be set off by small amounts of an initiator other than the bulk reactant. The most common application of inhibition is for protection of sensitive chemicals whose decomposition or polymerization by chain mechanisms may easily be triggered. 

In addition to the chemical mechanisms of fire retardants, thermal or barrier-type mechanisms may be operative. Coatings may prevent oxygen from reaching the wood surface. Dilution of combustible gases by noncombustible gases and inhibition of flaming by free radicals can also be in effect. Therefore, fire retardancy of wood involves many complex reactions. The effectiveness of a particular fire retardant depends on the overall summation of these competitive and sequential reactions and the thermal and physical environment of the material. 

The influence of molecular structures and substituents on the antiozonant properties of a series of related aromatic diamine compounds was studied. The relative effectiveness of the compounds was determined by viscometric techniques and by comparison of the rate of degradation of protected vuicanizates. Results indicate that unsymmetrical p-phenylenediamine derivatives are less effective than analogous symmetrical compounds as antiozonants. The protective capacity of the antiozonants decreases as the size or number of the N-hydrogen substituents, or the distance between the amine groups, increases. The comparative stability of the free radicals of aryl diamines, in terms of the theory of resonance, is utilized to explain the relative inhibiting properties of the chemicals examined. 

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