4(5)-Methylimidazole (4-MeI) is a nitrogen-containing heterocyclic compound found in class III and IV ammoniated caramel colors, a group of additives widely used in the food industry. A suspected carcinogen and neurotoxin and efforts are underway to limit its presence in foods. Several methods have been developed to detect and quantitate 4-MeI in different food matrices, including roasted coffee, beer, soft drinks, and soy sauce; however, no methods are available to measure 4-MeI in cooked meat and meat products containing lipids and high levels of interfering nitrogen compounds, such as amino acids and peptides. A rapid method using 0.1 M sodium acetate buffer (pH 5) as an extraction solvent followed by derivatization with isobutylchloroformate and gas chromatograph mass-spectrometry was developed to quantify 4-MeI in cooked meat products with added caramel colors containing 4-MeI. Selected ion monitoring mode was used to monitor 4-MeI ions fragments. In the 8 commercial meat products tested, 4-MeI levels ranged from 0.041 to 1.015 mg/kg, with recovery of 94.76% to 103.94%. In addition, a matrix-matched calibration performed by analyzing a spiked cooked meat sample indicated no significant difference (P > 0.05), which means the meat matrix had no effect on the developed method. This method proved useful in analyzing 4-MeI in meat products with added caramel color containing 4-MeI.

This study was to investigate the inhibitory effects of amino acids (AAs) on the formation of 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) and to evaluate the inhibition mechanism of PhIP in Maillard model systems. Different AAs were individually added into model systems heat-treated at 180 °C/1 h. The PhIP, phenylacetaldehyde (PheAce), and pyrazines derivatives were determined using HPLC and GC-MS. AAs significantly reduced (P < 0.05) PhIP levels in a dose-dependent response, ranking as: Trp = Lys > Pro > Leu > Met > Val > Ile > Thr > Phe > Asp, at the highest molar ratio. The PheAce content was gradually reduced with increasing AAs levels, suggesting that AAs may inhibit PhIP formation through scavenging the available PheAce. A correlation between PhIP inhibition and PheAce-scavenging activity of AAs was observed when PheAce and AAs were heated. The variety and quantity of pyrazines formed are highly depending on the type of AAs.

The effects of surface application of amino acids on the formation of heterocyclic amines (HCAs) and meat quality properties were evaluated in pan-fried beef patties (230°C/15 min). Tryptophan, lysine, leucine, and proline at three concentrations, 0.05%, 0.20%, and 0.50% (w/w), were tested. The meat crusts were analyzed for HCA content using liquid chromatography-tandem mass spectrometry. Results showed that surface application of all tested amino acids significantly reduced total HCA content (P < 0.05), and the interaction of amino acid type and concentration significantly affected (P < 0.05) both individual and total HCA formation. Tryptophan at 0.50% reduced total HCAs the most (0.92 ng/g, 93% inhibition), followed by 0.50% lysine (1.94 ng/g, 84% inhibition), while leucine (3.95 ng/g, 64% inhibition) and proline (4.71 ng/g, 56% inhibition) were less effective at 0.50%. In addition, applying amino acids to meat surface significantly influenced (P < 0.05) pH and surface color change of beef crusts; particularly, lysine at 0.20% and 0.50% increased pH and a * (redness) but reduced b * (yellowness), while tryptophan and leucine at 0.50% increased L * (whiteness). No significant effect was observed on cooking loss. Adding amino acids at 0.50% affected (P < 0.05) formation of aldehydes and pyrazines (as the key flavor compounds of fried beef). Overall, the results of this study suggested that adding amino acids to ground beef patties could effectively mitigate mutagenic HCA formation during cooking.

A simple, fast, and efficient method, “enhanced matrix removal of lipids” (EMR‐lipid), was proposed, optimized, and validated for identifying five polar heterocyclic amines (HCAs) in meat samples that ranged from high‐protein (beef and chicken) to high‐fat (pork bacon) matrices. The protocol involves an initial solid–liquid phase extraction followed by a rapid dispersive solid‐phase extraction using EMR‐lipid sorbents and salting‐out partitioning. Acetonitrile containing formic acid at two levels (1% and 2%) efficiently extracted HCAs from different meat matrices. Liquid chromatography–tandem mass spectrometry (MS/MS) with selective reaction monitoring mode was developed for qualitative and quantitative analysis. The highest MS/MS responses and better peak separation of analytes were achieved by adjusting mobile phases to pH 3.0 with instrumental detection limits between 0.01 and 0.05 ng/mL. Good linearity of standard curves was obtained in both pure solvents and postspiked meat extracts between 0.5 and 50.0 ng/mL. The validation results showed good precision, accuracy, and sensitivity for detecting HCAs in spiked meat samples. Satisfactory recoveries of four HCAs were achieved: 65% to 111% in beef, 71% to 106% in bacon, and 42% to 77% in chicken. Matrix effects were also assessed and showed less than –20% of ion suppression in bacon extract, while a medium to high signal suppression was observed in beef (–37% to –55%) and chicken (–28% to –52%). This optimized EMR‐lipid method provides acceptable results and advantages for determining trace level HCAs in complex meat matrices.

Heterocyclic amines (HCAs), highly mutagenic and potentially carcinogenic by-products, form during Maillard browning reactions, specifically in muscle-rich foods. Chemical model systems allow examination of in vitro formation of HCAs while eliminating complex matrices of meat. Limited research has evaluated the effects of Maillard reaction parameters on HCA formation. Therefore, 4 essential Maillard variables (precursors molar concentrations, water amount, sugar type, and sugar amounts) were evaluated to optimize a model system for the study of 4 HCAs: 2-amino-3-methylimidazo-[4,5-f]quinoline, 2-amino-3-methylimidazo[4,5-f]quinoxaline, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, and 2-amino-3,4,8-trimethyl-imidazo[4,5-f]quinoxaline. Model systems were dissolved in diethylene glycol, heated at 175 °C for 40 min, and separated using reversed-phase liquid chromatography. To define the model system, precursor amounts (threonine and creatinine) were adjusted in molar increments (0.2/0.2, 0.4/0.4, 0.6/0.6, and 0.8/0.8 mmol) and water amounts by percentage (0%, 5%, 10%, and 15%). Sugars (lactose, glucose, galactose, and fructose) were evaluated in several molar amounts proportional to threonine and creatinine (quarter, half, equi, and double). The precursor levels and amounts of sugar were significantly different (P < 0.05) in regards to total HCA formation, with 0.6/0.6/1.2 mmol producing higher levels. Water concentration and sugar type also had a significant effect (P < 0.05), with 5% water and lactose producing higher total HCA amounts. A model system containing threonine (0.6 mmol), creatinine (0.6 mmol), and glucose (1.2 mmol), with 15% water was determined to be the optimal model system with glucose and 15% water being a better representation of meat systems.