Degradation of heterocyclic aromatic amines in oil under storage and frying conditions and reduction of their mutagenic potential.

Heterocyclic aromatic amines (HAA) were systematically studied concerning their partition behavior in water/oil-systems and their thermostability in different animal derived fats and vegetable oils. Partitioning of IQx-compounds and PhIP in water/oil systems was found to depend on the polarity defined by the molecular structure and on the pH-value of the aqueous phase. In particular, beta-carbolines norharman and harman showed a significant strong lipophilic character at alkaline pH. After heating in frying fats at 130 degrees C, contents of IQx compounds and PhIP were reduced by more than 40% and after heating at 180 degrees C less than 10% of the HAA initial concentration was recovered. By contrast, norharman and harman were much more stable under equivalent conditions. The present study leads for the first time to the conclusion that degradation of HAA in frying fats strongly correlates to the type of frying fat and is promoted by lipid oxidation products. Firstly, addition of hydroperoxides to model oils lead to a decrease of HAA during storage at 40 degrees C. Secondly, stability of HAA correlated with the content of unsaturated fatty acids in the oil, which is indicative for the oxidative stability of the medium. Degradation of HAA by heat treatment was associated with a reduction of their mutagenic potential towards strain TA98 of Salmonella typhimurium.