Three different methods for determining nonheme iron content of meat extracts which differed in final pH and either in heating or not heating of the samples, were compared. The final pH of meat extracts had little effect on the level of nonheme iron but heating gave higher values. Both final temperature and rate of heating influenced release of nonheme iron from meat pigment extracts, with the optimum temperature being 63-70°C. Slow heating resulted in release of more noneheme iron than fast heating. Nitrite was shown to prevent release of heme iron, apparently through stabilizing the porphyrin ring. Sources of nonheme iron and their relationship to oxidation in cooked meat are discussed.

No abstract

The formation of N-substituted amides was investigated by using both model systems and bacon. Fatty acids were shown to react readily with selected -amino acids in model systems at 200 °C to give N-substituted amides. However, formation of primary amines via the decarboxylation of -amino acids appears to be unlikely at temperatures normally encountered in pan frying of bacon due to insufficient energy for the decarboxylation step. Under these conditions, only amines would react readily with fatty acids to yield secondary amides. N-substituted amides were shown to be nitrosated readily under acid conditions in a model system. It was also demonstrated that N-nitrosamides are very unstable under conditions commonly encountered in cooking bacon and thus are unlikely to be present in heat-processed foods.N-Nitrosamides which arise from the reaction of secondary amides with nitrite (Mirvish, 1977) usually have one alkyl residue and an acyl residue. They are chemically reactive compounds and are relatively easily hydrolyzed to alkylating diazoalkanes (Preussmann, 1974). They are considered to exert both local and systemic activity in the carcinogenesis of experimental animals (Preussmann, 1974). Although their powerful carcinogenic responses are well-known, there has been only a limited number of studies on the occurrence of nonvolatile IV-nitroso compounds in food systems, due in part to their instability under neutral and alkaline conditions (Mirvish, 1971). However, the precursors of N-nitrosamides have been reported in certain foods. Such compounds include uridine and ureas which have been isolated from fish by Mirvish (1975). High concentrations of agmatine, a decarboxylation product of arginine, have been reported in fresh abalone (Kawabata et al., 1978), and citrulline has been reported by Wada (1930) in watermelon.Recently, Sims and Fioriti (1975) reported that heating fatty acids (or esters) and triglycerides with -amino acids at temperatures above 150 °C resulted in the formation of N-substituted amides. These results were confirmed by Kakuda and Gray (1980a) using a model system con-

The contribution of some compounds previously identified in the flavor volatiles from cooked beef was estimated by surface response methodology. In most cases, predicted maximum scores for mixtures were higher than scores predicted for single compounds tested alone. Synergistic and/or synosmic effects were often indicated since mixtures frequently gave much higher scores. Predicted scores for four out of eight compounds tested were not significantly different from actual mean scores. This indicated the usefulness of the method for predicting optimal combinations of meat flavor components. The best three-component mixture consisted of 2,5dimethylpyrazine, furfural, and 1-butanol, which gave a score of 7.54, moderately resembling meat aroma.