Abstract
The effect of the incorporation of different levels of NaCl at 10.7, 21.4, 46 and 66 g kg -1 , and the combinations of NaCl (10 or 20 g kg -1 ) and Fe(II) or Cu(II) (25 or 50gg -1 ) in model systems of water dispersion in butter fat (WDIBFS) during storage was investigated by measuring peroxide value, p-anisidine index and TOTOX. The results indicated that NaCl at 10.7, 21.4 and 46 g kg -1 levels had a significant retarding effect against fat oxidation during 6 months of storage, while the higher concentration of 66 g kg -1 salt showed a significant prooxidant effect. NaCl significantly (p 0.05) increased the prooxidant effect of Cu(II) in all combinations, whereby the increase was directly proportional to the salt concentration. On the other hand, the addition of NaCl significantly increased the prooxidant effect of Fe(II) ions with no significant differences between the two salt levels (10 and 20 gkg -1 ). Ferrous ions were more effective as prooxidant than Cu(II) ions in the salt free WDIBFS. However, the addition of salt almost canceled the observed differences of the prooxidant influence of Fe(II) and Cu(II) ions.
Highlights
The (NaCl, Fe(II)) and (NaCl, Cu(II)) combinations that were prepared to evaluate the effect of NaCl on fat oxidation and the prooxidant activity of ferrous and copper ions
Sodium chloride at 10.7, 21.4 and 46 g kg-1 produced a protective effect on fat oxidation, while 6.6 g kg-1 showed prooxidant effect during long-term storage
NaCl significantly increased the prooxidant effect of Cu(II) and Fe(II)
Summary
The oxidative alteration of fats and oils and fatty foods is of great importance since it affects the quality of foods due to the development of rancidity (Frankel, 1985; Grosch. 1987), loss of nutritional value and formation of toxic compounds (Eriksson, 1987; Kubow, 1992; Esterbauer, 1993).Lipid oxidation is affected by many factors including elements such as iron and copper and NaCl. Ellis et al (1970) demonstrated that the addition of salt at different levels produced a protective effect against the oxidation of fat in a hydrated gel and a prooxidant effect in the freeze-dried gel. Mabrouk and Dungan (1960) studied the influence of oxygen absorption of NaCl in emulsions of methyl linoleate in water, and they observed progressive inhibition related to salt concentration. Tichivangana and Morrissey (1985) reported that ferrous ions induced a higher level of lipid oxidation than cupric ions in cooked meat. Salih et al (1989) found that (salt, Fe(II)) and (salt, Cu(II)) combinations showed higher levels of lipid oxidation in turkey meat than Fe(II) or Cu(II) alone. Farouk et al (1991) reported that the addition of ferrous ions and /or salt resulted in a marked increase in lipid oxidation in both uncooked and cooked ground beef during storage at 8-9oC. Tichivangana and Morrissey (1985) reported that ferrous ions induced a higher level of lipid oxidation than cupric ions in cooked meat. Salih et al (1989) found that (salt, Fe(II)) and (salt, Cu(II)) combinations showed higher levels of lipid oxidation in turkey meat than Fe(II) or Cu(II) alone. Farouk et al (1991) reported that the addition of ferrous ions and /or salt resulted in a marked increase in lipid oxidation in both uncooked and cooked ground beef during storage at 8-9oC. It has been reported that the addition of NaCl showed an increase in lipid oxidation in poultry meat (King and Earl, 1988). On the other hand, Salih (1986) reported that metal impurities, and not the salt, increased lipid oxidation
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