Meat curing ascorbate effects

In our search for nitrite alternatives, as far as flavor and oxidative stability Is concerned, we examined the effect of commonly used adjuncts In meat curing, as well as a large ntimber of antloxldant/sequesterant systems (40-42). In particular, the effect of sodium ascorbate (SA) and sodium tripolyphosphate (STFF) on the oxidative state of cooked meats was studied. These additives lowered the TEA numbers by a factor of about 2 and 4, respectively (Table IV). When used In combination, a strong synergism was observed. Furthermore, an Increase In the concentration of SA and/or STFF resulted In a decrease In the TEA values as depicted In Figure 6 (43). Addition of 30 ppm of butylated hydroxyanlsole (EHA) or tert-butylhydroqulnone (TEHQ) further reduced the TEA numbers and In fact the latter values were even lower than those obtained for meats treated with sodium nitrite (Table IV) (41). 

The rate of /V-nitrosation increases with the pKa of the amine and depends on the pH — it is highest at a pH range of 2-4. The reaction can be inhibited by compounds capable of binding the nitrosating agents — in meat curing, sodium ascorbate is very effective. Foods low in amines and nitrites generally contain about 1-10 ppb, while cured and heavy smoked meat and fish contain up to several hundred ppb of /V-nitroso compounds. 

Muscle tissues contain a multi-component antioxidant system consisting of lipid-soluble compounds (a-tocopherol, ubiquinone), water-soluble compounds (ascorbate, histidine-dipeptides) and enzymes (superoxide dismutase, catalase, glutathione peroxidase). Lipid oxidation in meats can be effectively controlled by the use of various phenolic compounds derived from spice extracts, by vitamin E supplementation of animal diets, and by processing of cured meat with sodium nitrite. Various natural antioxidant formulations containing mixtures of tocopherols, ascorbyl palmitate and citric acid show synergistic effects in stabilizing cooked and frozen meat. Synthetic antioxidants, BHA, TBHQ, propyl gallate (see Chapter 9) and combinations with citric acid, ascorbic acid or phosphates are also effective formulations used to retard lipid oxidation in... 

Thus, antioxidant effects of nitrite in cured meats appear to be due to the formation of NO. Kanner et al. (1991) also demonstrated antioxidant effects of NO in systems where reactive hydroxyl radicals ( OH) are produced by the iron-catalyzed decomposition of hydrogen peroxide (Fenton reaction). Hydroxyl radical formation was measured as the rate of benzoate hydtoxylation to salicylic acid. Benzoate hydtoxylation catalyzed by cysteine-Fe +, ascorbate - EDTA-Fe, or Fe was significantly decreased by flushing of the reaction mixture with NO. They proposed that NO liganded to ferrous complexes reacted with H2O2 to form nitrous acid, hydroxyl ion, and ferric iron complexes, preventing generation of hydroxyl radicals. 

Iron bioavailability may be increased in the presence of meat (Politz and Clydesdale 1988). This is the so-called meat factor. The exact mechanism of this effect is not known, but it has been suggested that amino acids or polypeptides that result from digestion are able to chelate nonheme iron. These complexes would facilitate the absorption of iron. In nitrite-cured meats some factors promote iron bioavailability (the meat factor), particularly heme iron and ascorbic acid or erythor-bic acid. Negative factors may in-clude nitrite and nitrosated heme (Lee and Greger 1983). 

Several ascorbic acid derivatives were examined by Pensabene et al. (570) for their ability to inhibit nitrosation of pyrrolidine in a model system developed to simulate the lipid-aqueous-protein composition of bacon. While sodium ascorbate was quite effective in the aqueous phase, a combination of an ascorbyl ester with sodium ascorbate gave a better effect in the lipid phase (Table XX). The use of ascorbates and tocopherol as inhibitors of nitrosamine formation and oxidation in foods of the aqueous and lipid type has been reviewed by Newmark and Mergens (326). These compounds in combination could be markedly useful in preventing food contamination with nitrosamines and/or nitros-amides in cured meats such as bacon. 

Several vitamins have some desirable additional effects. Ascorbic acid is a dough improver, but can play a role similar to tocopherol as an antioxidant. Carotenoids and riboflavin are used as coloring pigments, while niacin improves the color stability of fresh and cured and pickled meat. 

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