The Research And Application Of The Detection Methods Of Methylimidazoles In Caramel Food

In recent years, the methylimidazole is often detected in Caramel coloring food. The reason may be due to the use of ammonia (ammonium) when caramel producing, with the occurrence of side reactions. Recent scientific research shows,4-methylimidazole has the similar toxicity like pyridine, pyrrole and inhibit of cytochrome P450 isoenzymes, catalytic reaction occurs in the liver, while generating a number of low molecular weight carcinogens.2-methylimidazole and 4-methylimidazole are isomers, can also lead to seizures induced thyroid tumors of animals. Both substances is mainly associated with caramel into the body. GB 8871-2001 and the World Health Organization are prescribed 4-methylimidazole content shall not exceed 0.02% in caramel ammonia (ammonium) method produced, not make provision to 2-methylimidazole content. Today, the food security has become a focus of attention of the world, so the research and application of 2-methylimidazole and 4-methylimidazole is particularly important. This work established a new GC/MS method which simultaneously detected 2-methylimidazole and 4-methylimidazole based on the present determination method of 2-methylimidazole and 4-methylimidazole. The method is simple, sensitive and accurate. And for vinegar, soy sauce, beverages and other foods, we achieved good results. Specific studies and the results are summarized below:1.we compared the determination method of 2-methylimidazole and 4-methylimidazole,found that using UV spectrophotometry directly, there are more interference. Determination after the diazotization, the method was complicated operation and low sensitivity. Using GC, the internal standard is not ideal and had poor separation relatively. Using HPLC, the Samples are complicated. The impurity is difficult to separate with the analyte. Using the derivatized GC/MS, the complexity of the operation was significantly increasing.2.The method of selected ion GC-MS of 2-methylimidazole and 4-methylimidazole by determinated was established in vinegar. The results showed that when we used N-methyl-formanilide as internal standard, the concentration of 2-methylimidazole and 4-methylimidazole in the range of Omg/L ～15.2mg/L had a good linear relationship. Respectively the correlation coefficients were 0.9997 and 0.9996; Respectively the relative standard deviation were 3.0% and 3.1%; The recoveries of 2-methylimidazole and 4-methylimidazole were in the range of 97.3～107% and 95.6～98.4%.2-methylimidazole and 4-methylimidazole were measured by this method commercially in food coloring caramel, and achieved satisfactory results.3. Using the GC/MS established to commercially available 15 kinds of liquid seasoning、liquid beverages and foodstuffs. In which five kinds of beverage samples,2-methylimidazole was not detected in just one kind of beverage. The remaining were all inclusive of 2-methylimidazole and 4-methyl-imidazol. In 5 kinds of vinegar samples,2-methylimidazole and 4-methylimidazole were both detected. In 5 kinds of soy sauce samples, 2-methylimidazole and 4-methylimidazole were both detected. The results show:The foods mainly using caramel as a coloring agent, were containing 2-methylimidazole and 4-methyl-imidazole in different degree.