Chemical analysis and significance of heterocyclic aromatic amines

 Levels of known heterocyclic amines vary from undetectable in many meats sold in fast food restaurants, to over 10 ng/g for meats prepared in restaurants that cook food to order, to hundreds of nanograms per gram for some meats cooked under certain home or laboratory conditions. To simulate the dry reactions that seem to occur at the meat surface we developed a model system to mimic these processes. Mixtures of free amino acids, creatinine and glucose, simulating the composition of beef or chicken, heated at 200  °C, form eight heterocyclic amines. Besides the commonly found 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-1,6-dimethylimidazo[4,5-b]pyridine, 2-amino-1,5,6-trimethylimidazo[4,5-b]pyridine and 2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine were also found. The calculated risk of consumption of heterocyclic amines is determined by the dietary dose, the extrapolation of carcinogenic potencies from rodents to humans, and the extrapolation of high rodent doses to low human exposures. Results suggest that DNA binding is linear with dose, but that the human DNA forms more adducts per unit dose than that of the rat. Altogether, the risk appears to be equivalent to that for many carcinogens that are regulated. Received: 23 April 1998     

Chemical analysis of heterocyclic aromatic amines: the results of two European projects compared

 This report describes two studies which compared the results of the analyses of four heterocyclic aromatic amines (HAAs): 2-amino-3-methylinidazo[4,5-f]quinoline (IQ); 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx); 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), first as pure methanolic solutions and, in a second step, in a food matrice (beef extract) spiked with known amounts of these four HAAs. Details are given for the preparation of the methanolic solutions of the four HAAs and for the homogeneity and stability studies. The results of different statistical treatments revealed no significant heterogeneity within or between ampoules. The results of the stability studies clearly indicated that, except for PhIP, no effect of storage period (up to 6 months) or storage temperature (up to 25  °C), existed for the five HAAs methanolic solutions. Each of the eight European participating laboratories, which has leading experience in the analysis of HAAs, received sealed ampoules containing the pure reference solutions of the four HAAs together with a mixture of unknown identity and concentration. For the analysis of the unknwon sample, participants followed, a common work programme, but used different columns, solvent gradients and detection systems (UV, fluorescence, mass spectrometry and electrochemical detection. The analysis of the results of this first comparison revealed a good correlation between the results provided by the participants and high precision regarding the target values, independent of the experimental conditions used. For the second comparison, a common batch of commercial beef extract was prepared and spiked with known amounts of the four HAAs. The long-term stability study at –18  °C, 4  °C, 25  °C, 40  °C and 60  °C revealed high stability of these four HAAs, during up to 6 months of storage. At 40  °C and 60  °C, however, a significant loss was observed, in particular for PhIP. On the other hand, the 1-year stability study revealed that the HAAs content did not change when beef extract was stored at –18  °C. Details of these homogeneity and stability studies are provided. The sealed ampoules containing beef extract, together with the reference methanolic solutions were sent to the participants in refrigerated container. The eight European laboratories, which participated in the first comparision, adopted the work programme of this exercise. They generally followed a previously agreed upon solid-phase extraction procedure, very similar to that described by Gross [8], with analysis by HPLC. Column conditions, solvent elution and detection by UV, fluorescence, mass spectrometry and electrochemical detection varied between laboratories. The objectives of this second phase of the project were to compare and improve usual routine laboratory methods for the determination of IQ, MeIQx, 4,8-DiMeIQx and PhIP in the range of 1–30 ng/g, in a commercial beef extract. The comparision of the results revealed, however, large variations, not only beween but also within laboratories. Major difficulties were encountered by the participants, mainly for the determination of PhIP. Acceptable recovery levels were agreed between participants and different sources of variability in the extraction procedures were identified. In conclusion, whereas the analytical determination of HAAs in beef extract appeared to be satisfactory, the procedures of isolation and purification require further improvement. Received: 23 April 1998     

Chemical analysis of heterocyclic aromatic amines: the results of two European projects compared

 This report describes two studies which compared the results of the analyses of four heterocyclic aromatic amines (HAAs): 2-amino-3-methylinidazo[4,5-f]quinoline (IQ); 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx); 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), first as pure methanolic solutions and, in a second step, in a food matrice (beef extract) spiked with known amounts of these four HAAs. Details are given for the preparation of the methanolic solutions of the four HAAs and for the homogeneity and stability studies. The results of different statistical treatments revealed no significant heterogeneity within or between ampoules. The results of the stability studies clearly indicated that, except for PhIP, no effect of storage period (up to 6 months) or storage temperature (up to 25  °C), existed for the five HAAs methanolic solutions. Each of the eight European participating laboratories, which has leading experience in the analysis of HAAs, received sealed ampoules containing the pure reference solutions of the four HAAs together with a mixture of unknown identity and concentration. For the analysis of the unknwon sample, participants followed, a common work programme, but used different columns, solvent gradients and detection systems (UV, fluorescence, mass spectrometry and electrochemical detection. The analysis of the results of this first comparison revealed a good correlation between the results provided by the participants and high precision regarding the target values, independent of the experimental conditions used. For the second comparison, a common batch of commercial beef extract was prepared and spiked with known amounts of the four HAAs. The long-term stability study at –18  °C, 4  °C, 25  °C, 40  °C and 60  °C revealed high stability of these four HAAs, during up to 6 months of storage. At 40  °C and 60  °C, however, a significant loss was observed, in particular for PhIP. On the other hand, the 1-year stability study revealed that the HAAs content did not change when beef extract was stored at –18  °C. Details of these homogeneity and stability studies are provided. The sealed ampoules containing beef extract, together with the reference methanolic solutions were sent to the participants in refrigerated container. The eight European laboratories, which participated in the first comparision, adopted the work programme of this exercise. They generally followed a previously agreed upon solid-phase extraction procedure, very similar to that described by Gross [8], with analysis by HPLC. Column conditions, solvent elution and detection by UV, fluorescence, mass spectrometry and electrochemical detection varied between laboratories. The objectives of this second phase of the project were to compare and improve usual routine laboratory methods for the determination of IQ, MeIQx, 4,8-DiMeIQx and PhIP in the range of 1–30 ng/g, in a commercial beef extract. The comparision of the results revealed, however, large variations, not only beween but also within laboratories. Major difficulties were encountered by the participants, mainly for the determination of PhIP. Acceptable recovery levels were agreed between participants and different sources of variability in the extraction procedures were identified. In conclusion, whereas the analytical determination of HAAs in beef extract appeared to be satisfactory, the procedures of isolation and purification require further improvement. Received: 23 April 1998     

Antioxidant spices reduce the formation of heterocyclic amines in fried meat

 Heterocyclic aromatic amines (HAs) are mutagenic compounds that are formed during heating of meat and fish. These substances are reaction products of creatine with amino acids and carbohydrates. It is recommended that exposure to these probable human carcinogens should be minimised. Five heterocyclic aromatic amines which occur in beef were investigated: 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethyl-imidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethyl-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx), and 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP). Clean-up was done by acid-base partition followed by SPE using blue cotton. HPLC analysis was carried out by using electrochemical detection for IQ- and IQx-type compounds and fluorescence detection for PhIP. The concentrations of the aromatic amines were as follows: IQ, 10.2 μg/kg; MeIQ, 2.46 μg/kg; MeIQx, 13.2 μg/kg; 4,8-DiMeIQx, 2.26 μg/kg; and PhIP, 5.48 μg/kg. The application of spices (rosemary, thyme sage, garlic, brine) reduced the content of the HAs below 60% of the amount found in the control. Received: 23 April 1998     

The inherent genotoxic potency of food mutagens and other heterocyclic and carbocyclic aromatic amines and corresponding azides

 Relationships between the chemical structure of aromatic amines (including heterocyclic food mutagens) and genotoxic potency were originally established on the basis of Salmonella mutagenicity data. These relationships are reviewed. We report here that also quite different genotoxic effects, namely the binding to deoxyguanosine-3′-phosphate (dGp), hypoxanthine phosphoribosyl-transferase (HPRT) mutations, and sister chromatid exchange in Chinese hamster cells follow essentially the same structure-activity relationships. The heterocyclic amines of the aminoimidazoquinoline, aminoimidazoquinoxaline and aminoimidazopyiridine types unite a number of structural characteristics which endow these compounds, or rather their reactive species, presumed to be nitrenium ions, with an extremely high inherent genotoxic potency. This conclusion is supported by experimental work and by calculations of electronic properties of these compounds and their nitrenium ions. Received: 23 April 1998     

Heterocyclic aromatic amines in fried poultry meat

 Heterocyclic aromatic amines are mutagenic compounds that are formed during heating of meat and fish. These substances are products of the reaction of creatine with amino acids and carbohydrates. It is recommended that exposure to these probable human carcinogens should be minimised. In fried boneless lean turkey breast meat five heterocyclic aromatic amines {2-amino-1-methyl-imidazo[4,5-f]quinoline (IQ), 2-amino-3,8-dimethyl-imidazo-[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethyl-imidazo[4,5-f]quinoxaline (4,8-DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)} were found. The temperature regime which was applied for frying resulted in a surface temperature of about 140°C. Clean-up was done by acid-base partition followed by solid-phase extraction (SPE) using blue cotton. HPLC analysis was carried out using electrochemical detection for IQ- and IQx-type compounds and fluorescence detection for PhIP. The low temperatures used during frying yielded comparably lower amounts of heterocyclic aromatic amines. The concentrations of the aromatic amines were as follows: IQ 1.1 μg/kg, MeIQ 0.9 μg/kg, MeIQx μg/kg, 4,8-DiMeIQx 0.4 μg/kg, and PhIP 3.8 μg/kg. Received: 19 February 1997 / Revised version: 21 April 1997     

Metabolically competent yeast strains as a tool to study the genotoxicity of heterocyclic aromatic amines: simultaneous expression of three human cDNAs in Saccharomyces cerevisiae

 Heterocyclic aromatic amines (HAs) are found at considerable levels in fried or broiled fish and meat. These substances are potent mutagens in the Ames assay and are also carcinogens in animals. We were interested in the genotoxic consequences of exposing cells to HAs and used Saccharomyces cerevisiae as a model. In this study we used different genotoxicity tester strains, YHE2 and YB110, to monitor HA-induced gene conversion and chromosomal translocation events, respectively. The diploid strain YHE2 monitors gene conversion between two trp5 alleles, whereas strain YB110 detects recombination between two truncated his3 alleles located on non-homologous chromosomes resulting in translocations. However, HAs require metabolic activation catalyzed by cytochrome P450 (CYP1A2) and N-acetyltransferase (NAT2), two enzymes which are not present in standard yeast strains. In order to activate HA compounds to their genotoxic product in intact yeast strains, expression vector pGP100 has been constructed, which directs simultaneous expression of three human cDNAs coding for CYP1A2, cytochrome P450 oxidoreductase and NAT2. Crude extracts of respective yeast transformants exhibited substantial NAT activity which was detected using sulfamethazine as a specific substrate for NAT2. Moreover, when yeast transformants were exposed for 4 h to various HAs a dose-related increase in mitotic recombination was observed, which depended on the presence of NAT2 in the majority of cases. Thus, if appropriately metabolized by CYP1A2 and NAT2, various aromatic amines induce mitotic recombination in yeast cells and it may be speculated that they behave similarly in rodent and human cells, thereby contributing to loss of heterozygosity, an important step in carcinogenesis. Received: 23 April 1998     

Interspecies metabolism of heterocyclic aromatic amines and the uncertainties in extrapolation of animal toxicity data for human risk assessment

Heterocyclic aromatic amines (HAAs) are potent bacterial mutagens that are formed in cooked meats, tobacco smokes condensate, and diesel exhaust. Many HAAs are carcinogenic in experimental animal models. Because of their wide-spread occurrence in the diet and environment, HAAs may contribute to some common types of human cancers. The extrapolation of animal toxicity data on HAAs to asses human health risk has many uncertainties, which can lead to tenuous risk assessment estimates. Perhaps the most critical and variable parameters in interspecies extrapolation are the effects of dose, species differences in catalytic activities of xenobiotic metabolism enzymes (XMEs), human XME polymorphisms that lead to interindividual differences in carcinogen metabolism and dietary constituents that may either augment or diminish the carcinogenic potency of these genotoxins. The impact of these parameters on the metabolism and toxicological properties of HAAS and uncertainties in extrapolation of animal toxicity data for human risk assessment are presented in this article.     

Analysis of heterocyclic aromatic amines by high resolution gas chromatography-mass spectrometry: a suitable technique for the routine control of food and process flavours

 Ten heterocyclic aromatic amines (HAA; [2-amino-3-methyl-3H-imidazo[4,5-f]quinoline (1); 2-amino-3,4-dimethyl-3H-imidazo[4,5-f]quinoline (2); 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline (3); 2-amino-3,8-dimethyl-3H-imidazo[4,5-f]quinoline (4); 2-amino-3,4,8-trimethyl-3H-imidazo[4,5-f]quinoline (5); 2-amino-3,7,8-trimethyl-3H-imidazo[4,5-f]quinoline (6); 2amino-3,4,7,8-tetramethyl-3H-imidazo[4,5-f]quinoline (7); 2-amino-1-methyl-6-phenyl-imidazo[4,5-f]quinoline (8); 2-amino-6-methyldipyrido[1,2-α : 3′,2′-d]imidazole (9); 2-aminodipyrido[1,2-α : 3′,2′-d]imidazole (10)]) were analysed in commercially available meat products and process flavours. After sample preparation by Extrelut treatment, subsequent solid phase extraction applying propylsulphonic and C₁₈ silica cartridges, as well as derivatization with 3,5-bis-trifluoromethylbenzyl bromide, HRGC-electron-impact-ionization-MS (HRGC-EIMS) analysis in the selected ion monitoring mode was performed. Isotope dilution analysis with 2amino-8-methyl-3-(trideuteromethyl)-3H-imidazo[4,5- f]quinoxaline and 2-amino-1-(trideuteromethyl)-6-phenyl-imidazo[4,5-b]pyridine was used to quantify 4 and 8; for 1–3, 5–7, 9 and 10, standard addition was employed as the determination method. The detection limit of 1 ng/g evaluated for 3–6 and 9 was sufficient for routine analysis, i.e. to obtain an initial insight into the grade of a potential HAA contamination of food or process flavours. To obtain more detailed information, the previously developed, more sensitive technique of HPLC-electrospray-tandem-MS (HPLC-ESI-MS/MS) has to be used, as shown by the comparison of the data obtained by HRGC-MS and HPLC-ESI-MS/MS analyses. Received: 4 March 1999     

A new quick solid-phase extraction method for the quantification of heterocyclic aromatic amines

A new solid-phase extraction (SPE) method using only one SPE cartridge is described as a clean-up procedure for the determination of heterocyclic aromatic amines (HAAs). In particular, the polar HAAs imidazoquinolines and imidazoquinoxalines, which are well-known toxic compounds in thermally treated food, can be determined by this quick and simple method. For validation of the method meat extracts were analyzed. For determination of the percentage recovery and standard deviation the beef extract was spiked (40 ng/g of each HAA) and analyzed 10 times. The polar HAAs were determined in this meat extract with a recoveries of 62 % to 95% and standard deviations of 3% to 5%. The recovery rates of the less polar HAAs Harman and Norharman were much lower (25±5% to 32±5%). The limit of detection for polar and less polar HAAs was between 3 ng/g and 9 ng/g in the meat extract matrix. The method comprises extraction with methanolic NaOH, centrifugation and SPE using a commercially available polystyrene copolymer cartridge. After different washing steps the eluate was analyzed by high-performance liquid chromatography with diode-array detection. The advantages of this new method are the reduced amounts of time and organic solvents required. Received: 29 November 1999 / Revised version: 21 February 2000     

天然抗氧化物质对肉制品中杂环胺生成的影响

杂环胺常见于如禽肉、鱼肉等富含蛋白质的热加工肉制品中,是一类杂环芳香族化合物。杂环胺具有极强的致癌致突变性,通常在肉制品于100℃及以上的高温烹制过程中产生。长期摄入具有高含量杂环胺的肉制品,会增加消费者患肿瘤患癌的风险。天然抗氧化物质具有抗氧化活性,且毒性小,安全性高,现已普遍应用于肉制品加工领域。通过添加天然抗氧化物质抑制肉制品中杂环胺的生成是当前研究热点。本文简要介绍了杂环胺的分类、形成等,并重点综述了近10年天然抗氧化物质对肉制品杂环胺形成的影响研究进展,其中,重点围绕多酚类化合物、黄酮类化合物、香辛料3类具有代表性的天然抗氧化物质对肉制品中杂环胺形成的影响进行了详尽的阐述。最后对未来的研究提出了展望。     

Mitigation strategies to reduce the impact of heterocyclic aromatic amines in proteinaceous foods

BackgroundMeat and fish are currently the main sources of proteins necessary for a healthy diet. Cooking proteinaceous food helps reduce biological risks and produce odor-active compounds, but it also generates heat-induced toxicants, of which heterocyclic aromatic amines (HAAs) are probably the most problematic as they are strongly mutagenic and carcinogenic.Scope and approachThis review highlights the most promising strategies for mitigating the impacts of HAAs on human health. These strategies revolve around reducing HAA formation by impacting HAA precursors, controlling the process, adjusting formulations or adapting diets to limit HAA assimilation and metabolism.Key findings and conclusionsIdentifying the different mechanisms of HAA formation and metabolism has made it possible to propose mitigation strategies to limit the risks related to HAA consumption. Various kinds of levers exist. While cooking methods for industrial processed foods can be regulated, it is far more difficult to influence household practices. Mitigation strategies involving other food ingredients are probably more promising from a consumer point of view if pushed by health education campaigns. Efforts to reduce the health risk from HAA consumption should now turn to ingredients like carvacrol that present different concomitant modes of action.     

Production of heterocyclic aromatic amines in meat: Chemistry,health risks and inhibition. A review

Heterocyclic aromatic amines are compounds produced in meat subjected to high temperature cooking. Formation of these substances is highly influenced by cooking method, cooking time, cooking temperature, and type of meat. Heterocyclic amines contain heterocyclic rings and nitrogen containing groups within their structure. Risks of colon, pancreas, gastrointestinal tract, lung, liver, prostate, skin and breast cancers are decidedly associated with the consumption of heterocyclic amines. These mutagenic compounds can be attenuated by addition of different fruits and vegetable extracts. Several spices and antioxidants can also be used for the reduction of these heterocyclic amines. The level of heterocyclic amines can be reduced by cooking at low temperature and by decreasing the cooking time. Formation of heterocyclic amines can also be prevented by marinating the meat before frying or grilling and by microwave pre-treatments. Objectives of this review are to create awareness about health risks, and to stimulate further research on other suitable ways to reduce the cancer risks associated with the consumption of cooked meat products.     

Effect of green tea marinades on the formation of heterocyclic aromatic amines and sensory quality of pan-fried beef

The effect of a green tea marinade on the formation of heterocyclic aromatic amines (HAs) was examined in pan-fried beef cooked at 180–200 °C for 4 min each side. Different marinating times were assayed and unmarinated samples cooked in similar conditions provided reference HAs levels. A green tea marinade catechin rich was prepared taking 1 g of green tea and infusing with 125 ml of boiling tap water during 10 min. Four HAs were quantified in unmarinated and marinated meat samples during 1, 2, 4 and 6 h at 5 °C. Compared with the unmarinated samples, marinating in green tea resulted in a significant decrease (p < 0.05) of levels of PhIP and AαC. Person correlation indicated that the reduction of the levels of these HAs in meat marinated with the increase of marinating time was significant (respectively, r = −0.799, p < 0.0001; r = −0.631, p < 0.05). No reduction was observed for 4,8-DiMeIQx and MeIQx.     

Effect of cooking methods on the formation of heterocyclic aromatic amines in chicken and duck breast

Heterocyclic aromatic amines (HAAs), potent mutagens/carcinogens, are pyrolysis formed during the cooking of meat and fish. In the present study, the effects of various cooking methods, pan-frying, deep-frying, charcoal grilling and roasting on the formation of HAAs in chicken breast and duck breast were studied. The various HAAs formed during cooking were isolated by solid-phase extraction and analyzed by high-performance liquid chromatography (HPLC). Results showed that chicken breast cooked by charcoal grilling contained the highest content of total HAAs, as high as 112 ng/g, followed by pan-fried duck breast (53.3 ng/g), charcoal grilled duck breast (32 ng/g), pan-fried chicken breast (27.4 ng/g), deep-fried chicken breast (21.3 ng/g), deep-fried duck breast (14 ng/g), roasted duck breast (7 ng/g) and roasted chicken breast (4 ng/g). For individual HAA, the most abundant HAA was 9H-pyrido-[4,3-b]indole (Norharman), which was detected in charcoal grilled chicken breast at content as high as 32.2 ng/g, followed by 1-methyl-9H-pyrido[4,3-b] indole (Harman) and 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine(PhIP) at 32 and 31.1 ng/g in charcoal grilled chicken breast, respectively. The content of PhIP in pan-fried duck and chicken breast were 22 and 18.3 ng/g, respectively. Generally, the type and content of HAAs in cooked poultry meat varies with cooking method and cooking conditions.     

Exposure to heterocyclic aromatic amines from the consumption of cooked red meat and its effect on human cancer risk: A review

This review covers the bibliographic data from the last 10 years on the possible carcinogenicity of heterocyclic aromatic amines (HAAs) in humans. Aspects such as red meat intake, cooking methods applied to red meat, and doneness of cooking are discussed from an epidemiological point of view. The role in the carcinogenicity of the HAAs has been assigned to two main factors: first, the very high frequency of consumption of red meat; and, second, very darkly browned meats from cooking. However, there are some uncertainties associated with epidemiological results such as the presence of other carcinogens, co-carcinogens and anti-carcinogens in the diet, analytical results on the content of HAAs in foods, food frequency questionnaires, and mainly genetic susceptibility to HAAs. It is concluded that there is not sufficient scientific evidence to support the hypothesis that human cancer risk is due specifically to the intake of HAAs in the diet.     

Exposure to heterocyclic aromatic amines from the consumption of cooked red meat and its effect on human cancer risk: A review

This review covers the bibliographic data from the last 10 years on the possible carcinogenicity of heterocyclic aromatic amines (HAAs) in humans. Aspects such as red meat intake, cooking methods applied to red meat, and doneness of cooking are discussed from an epidemiological point of view. The role in the carcinogenicity of the HAAs has been assigned to two main factors: first, the very high frequency of consumption of red meat; and, second, very darkly browned meats from cooking. However, there are some uncertainties associated with epidemiological results such as the presence of other carcinogens, co-carcinogens and anti-carcinogens in the diet, analytical results on the content of HAAs in foods, food frequency questionnaires, and mainly genetic susceptibility to HAAs. It is concluded that there is not sufficient scientific evidence to support the hypothesis that human cancer risk is due specifically to the intake of HAAs in the diet.     

Occurrence of heterocyclic amines in cooked meat products

Heterocyclic amines (HCAs), potent mutagens and a risk factor for human cancers, are produced in meats cooked at high temperature. The aim of this study was to determine the HCA content in cooked meat products (beef, chicken, pork, fish) prepared by various cooking methods (pan frying, oven broiling, and oven baking at 170 to 230 °C) that are preferred by U.S. meat consumers. The primary HCAs in these samples were PhIP (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine) (1.49-10.89 ng/g), MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline) (not detected-4.0 ng/g), and DiMeIQx (2-amino-3,4,8-trimethyl-imidazo [4,5-f]quinoxaline) (not detected-3.57 ng/g). Type and content of HCAs in cooked meat samples were highly dependent on cooking conditions. The total HCA content in well-done meat was 3.5 times higher than that of medium-rare meat. Fried pork (13.91 ng/g) had higher levels of total HCAs than fried beef (8.92 ng/g) and fried chicken (7.00 ng/g). Among the samples, fried bacon contained the highest total HCA content (17.59 ng/g).     

烹调食品中杂环胺检测的分析方法

杂环胺是富含蛋白质的食品在热加工过程中产生的一类多环芳香族化合物,具有致癌、致突变性。本文系统地对杂环胺的检测方法进行了综述。介绍了高效液相色谱法、气相色谱法、气相色谱-质谱法、液相色谱-质谱法、毛细管电泳法、ELISA方法和高效薄层色谱法等杂环胺定性定量的分析方法,重点讨论了检测方法的优势和特点。      

Enhancement of colon and stomach carcinogenesis in 1,2-dimethylhydrazine-treated rats fed a diet high in heterocyclic amines

 Epidemiological studies have linked the consumption of red meat and the consumption of highly browned meats containing high levels of heterocyclic aromatic amines (HCAs) to increased risk of colorectal cancer or polyps. We have examined the effects of long-term feeding of beef-containing diets with low and high levels of HCAs (in the context of a low- or high-beef tallow diet) on a standard 1,2-dimethylhydrazine (DMH)-induced colon tumorigenesis protocol. Feeding of a beef diet high in HCAs resulted in more DMH-induced colon adenocarcinomas, but only in the context of a low fat diet. The high HCA diets increased stomach tumors in all DMH-treated rats. An apparent interaction of high HCA levels with a high fat level reduced the colon tumor incidence and tumor numbers in those rats on diets containing both these factors. These results support the epidemiological data linking well-cooked meat to increased risk for colon and stomach cancer, but the role of the dietary fat level remains puzzling. Additionally, we examined the DNA of liver, colon, and stomach from control rats (not treated with DMH) fed a high level of HCAs for 27 weeks. The genomic DNA was analyzed for the presence of 2-amino-1-methyl-6-phenylimidazo[4,5-f]pyridine (PhIP) adducts by ³²P-postlabeling analysis and was also used in PCR to amplify the rat p53 and Apc genes, followed by direct dye-terminator DNA sequencing. Results showed that no PhIP adducts were present in any tissue. In addition, there were no signature p53 or Apc gene mutations seen in the colon or stomach DNA. These results indicate that the high level of HCAs present in a diet of well-cooked meat does not cause (1) persistent PhIP adducts similar to those produced by feeding pure PhIP at high doses or (2) p53 and Apc gene mutations in nontumor tissue. Received: 23 April 1998