Formation of genotoxic 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) and its kinetics in a model system

Simultaneous kinetics formation of heterocyclic amines and polycyclic aromatic hydrocarbons in phenylalanine model system

A combination of chemical model system with kinetics study was used to investigate the simultaneous formation of heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Heating a mixture of phenylalanine, creatinine, and glucose at a commonly practiced household cooking time and temperature successfully differentiated the rate formation (k) of HCAs and PAHs. The good fit suggested that the simultaneous formation was an endothermic bimolecular reaction, and followed the first-order model. The rate formation (k) of HCAs and PAHs significantly increased with increasing heating time and temperature. Only 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) showed degradation rate (k) at higher heating temperatures of 210 °C and 240 °C respectively. Increasing phenylalanine concentration increased the possibility of higher HCAs and PAHs formation. The activation energy (Ea) showed that heating phenylalanine mixture resulted in higher rate of formation of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and benzo[b]fluoranthen (BbF).

Formation and Prediction of PhIP, Harman, and Norharman in Chemical Model Systems Containing Epicatechin under Various Reaction Conditions

The aim of this study was to investigate the formation rules of 1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), 1-methyl-9H-pyrido[3,4-b]-indole (Harman), and 9H-pyrido[3,4-b]-indole (Norharman) in chemical model systems containing epicatechin under various reaction conditions and establish their prediction models. The results indicated that at 100-200 °C and pH 5.5-7.5 for 10-90 min, epicatechin inhibited the formation of PhIP, Harman, and Norharman by 32-100, 1-93, and 5-98%, respectively. The exponential growth equation in the growth model with R² of 0.986-0.997, the second-order equation in the polynomial model with R² of 0.900-0.949, and the trigonometric function equation in the Fourier model with R² of 0.513-0.926 were well fitted for the formation of PhIP, Harman, and Norharman at various temperatures, times, and pHs, respectively. The calibration set (R²c) and the prediction set (R²p) of the optimal partial least squares regression prediction model was 0.74 and 0.70 for PhIP, 0.75 and 0.70 for Harman, and 0.90 and 0.91 for Norharman, respectively. The results provide theoretical support to develop technologies or equipment for the real-time synchronous monitoring of PhIP, Harman, and Norharman during meat processing.

Evaluating the effects of temperature and time on heterocyclic aromatic amine profiles in roasted pork using combined UHPLC-MS/MS and multivariate analysis

In this study, ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) combined with principal component analysis (PCA) were used to investigate the effects of process conditions on the profiles of carcinogenic and mutagenic heterocyclic aromatic amine (HAA) in the pork roasted at 175 °C, 200 °C, 225 °C and 250 °C for 10, 15, 20, 25, 30, 35 and 40 min. Twelve HAAs from four categories, including carboline (Norharman, Harman, and Phe-p-1), imidazopyridine (PhIP, 4'-OH-PhIP, DMIP, and 1,5,6-TMIP), imidazoquinoline (IQ, IQ [4,5-b], and MeIQ), and imidazoquinoxaline (MeIQx and 4,8-DiMeIQx), were detected, quantified and used to compose the HAA profiles in roasted pork. After being Analyzed by PCA, the distributions of HAA profiles from different temperature on the PCA score plot demonstrated that there are significant differences among the HAA profiles from different temperatures. The loading plot also showed that PhIP, 4'-OH-PhIP, IQ[4,5-b], and MeIQ were mainly responsible for the difference. The profiles from higher temperature distribute more scattered than the lower ones, illustrating that the time effects on the HAA profiles from higher temperature are stronger than the lower ones. Comparing the score and loading plots of different heating times, the diversities of the HAA profiles at different temperatures increased under prolonged heating because of the changingpyridines levels. The results of PCA that comparing the HAA from different categories displayed that the formation features of four categories HAAs were significantly differed because of their formation discrepancy under low temperatures and short-term roasting. Using HAA profiles as an entirety, these findings obtained in this study are more close to the real process of HAA formation in roasted pork, and make the complex effects of temperature and time on multiple HAA formations more simply to be concluded.

Effect of Different Amino Acids and Heating Conditions on the Formation of 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and Its Kinetics Formation Using Chemical Model System

The formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated using a kinetic study approach as described by first-order, Arrhenius, and Eyring equations. Chemical model systems with different amino acid precursors (proline, phenylalanine, and glycine) were examined at different times (4, 8, 12, and 16 min) and temperatures (150, 180, 210, 240, and 270 °C). PhIP was detected using high-performance liquid chromatography equipped with fluorescence detector (HPLC-FLD). The good fit in first-order suggested that PhIP formation was influenced by the types of amino acids and PhIP concentration significantly increased with time and temperature (up to 240 °C). PhIP was detected in proline and phenylalanine model systems but not in the glycine model system. The phenylalanine model system demonstrated low activation energy (Ea) of 95.36 kJ/mol that resulted in a high rate of PhIP formation (great amount of PhIP formed). Based on the ∆S‡ values both proline and phenylalanine demonstrated bimolecular rate-limiting steps for PhIP formation. Altogether these kinetic results could provide valuable information in predicting the PhIP formation pathway.