Long-chain alkyl-substituted heterocyclic compounds

Interest in the influence of lipids on pyrazine formation has recently been generated by the identification of long-chain alkyl-substituted heterocyclic compounds in foods and in model systems. Pyrazines in this category include 2-heptylpyrazine isolated from french fried potato flavor (7), and 2-methyl-3(or 6)-pentylpyrazine and 2,5-dimethyl-3-pentylpyrazine, isolated from extruded zein/corn amylopectin/corn oil systems (8, 9). Only the involvement of lipids or lipid-decomposition products in the formation of these compounds could account for the long-chain alkyl substitution on the pyrazine ring. 

A considerably large number of long-chain alkyl-substituted heterocyclic compounds were detected in this interaction system. 

Heterocyclic compounds, especially those which contain nitrogen and sulfur atoms, possess potent sensory qualities at low concentrations. They are formed in foods by thermal decomposition and interaction of food components. The identification of many long-chain alkyl-substituted heterocyclic compounds suggests that their formation mechanisms directly involve lipids or lipid decomposition products. 

Heterocyclic compounds are primarily formed through non-enzymatic browning reactions. Recent studies of deep-fat fried food flavors led to the identification of pyrazines, pyridines, thiazole, oxazoles and cyclic polysulfides which had long-chain alkyl substitutions on the heterocyclic ring. The involvement of lipid or lipid decomposition products in the formation of these compounds could account for the long-chain alkyl substitutions. Model systems were used to study the participation of lipids in the formation of pyrazines, pyridines, thiophenes and cyclic polysulfides. 

Tocopherols Tocopherols are heterocyclic compounds with a phenolic group and a substituted side chain of branched hydrocarbon. Their high solubility in oil is caused by a long alkyl side chain. The Codex Alimentarius (Codex-Stan 210-1999) indicates levels of tocopherols and tocotrienols in crude regular sunflower oil (mg/kg), compiled in Table 5. 

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