Formation of heterocyclic amine–amino acid adducts by heating in a model system

Although mutagenic and carcinogenic heterocyclic amines (HCAs) are known to be formed in cooked meat and fish, human HCA exposure and carcinogenic risk have not been elucidated in sufficient detail. In this work, we investigated the formations of HCA–amino acid adducts in a model system by using a liquid chromatography–mass spectrometry to elucidate another source of human HCA exposure. The 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) adduct with glycine was formed easily by heating at 200 °C within 5 min, which is probably based on the dehydration condensation of the amino group of PhIP and carboxyl group of glycine. PhIP and other HCAs such as 2-amino-3-methyl-3H-imidazo[4,5-f]quinolone, 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline and 3-amino-1,4-dimethyl-5H-pyrido[3,4-b]indole, also bound with various amino acids by heating. Among these amino acids, proline tends to form adducts with HCAs, but serine, cysteine and lysine hardly bound with HCAs. These results provided a basic understanding of the formation of HCA adducts with amino acids during cooking.     

Inhibition of 2‐Amino‐1‐methyl‐6‐phenylimidazo [4,5‐b]pyridine (PhIP) Formation by Alkoxy Radical Scavenging of Flavonoids and Their Quantitative Structure–Activity Relationship in a Model System

The inhibitory effect of 10 flavonoids on the formation of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in a creatinine–phenylalanine model system was investigated through electronic spin resonance and a quantitative structure–activity relationship. Alkoxy radicals were observed during the heating process, providing evidence for a radical pathway in the formation of PhIP. The alkoxy radical scavenging capability of the flavonoids was proportional to their inhibition of PhIP formation (IC₅₀). We deduced that flavonoid inhibition of PhIP generation occurs via scavenging of alkoxy radicals during the heating process. Multiple linear regression and partial least squares models were used to elucidate the relationship between PhIP inhibition activity and structure characteristics of the flavonoids. The lipo–hydro partition coefficient and molecular fractional polar surface area of the flavonoids were found to be predictive of the inhibition effect.     

Chemical,biological and sensory evaluation of pasta products supplemented with α‐galactoside‐free lupin flours

α‐Galactoside‐free lupin flour has been used to supplement durum wheat semolina flour in order to increase the nutritive value of pasta products. Supplemented pasta products had a shorter cooking time, higher cooking water absorption, cooking loss and protein loss in water than control pasta prepared with only semolina. Sensory evaluation of cooked pastas showed that products supplemented with 80 g kg^?1 of α‐galactoside‐free Lupinus angustifolius var. Emir flour or with 100 g kg^?1 of α‐galactoside‐free Lupinus angustifolius var. Troll flour showed the same acceptability by panellists as the semolina pasta. These levels of supplementation were selected for further studies. The cooked α‐galactoside‐free lupin/semolina pastas showed higher amounts of protein, dietary fibre, calcium, phosphorus, magnesium, zinc and antioxidant capacity than control pasta and a reasonable level of vitamin B₁, vitamin B₂ and vitamin E. Biological assessment of cooked pastas indicated that the true protein digestibility did not change after the fortification of semolina but protein efficiency ratio increased sharply in the pasta supplemented with α‐galactoside‐free lupin flours (2.07 and 1.92 for Emir and Troll lupin varieties, respectively) in comparison with the control pasta (1.11). It is concluded that the α‐galactoside‐free lupin flours are an adequate ingredient to improve the nutritional quality of pasta products without adding flatulent oligosaccharides. Copyright © 2006 Society of Chemical Industry     

Influence of food condiments on the formation of carcinogenic heterocyclic amines in cooked chicken and determination by LC-MS/MS

Heterocyclic amines (HCAs) are known to be suspected human carcinogens produced by high-temperature cooking of protein-rich foods such as meat and fish. In the present study, the influence of numerous food condiments on the formation of HCAs in cooked chicken was investigated. Chicken samples were subjected to pan-frying under controlled temperature. The levels of HCAs DMIP, MeIQx, 4,8-DiMeIQx, PhIP, harman and norharman were found to be between 0.93 and 27.52 ng g^?1, whereas IQ, MeIQ, AαC, MeAαC, Trp-P-1 and Trp-P-2 were found either below the limit of quantification or not detected in the control sample. Nevertheless, for samples cooked using food condiments, the amounts of HCAs (DMIP, MeIQx, 4,8-DiMeIQx and PhIP) were between 0.14 and 19.57 ng g^?1; harman and norharman were detected at higher concentrations up to 17.77 ng g^?1 while IQ and MeIQ were at levels below the limit of quantification; and AαC, MeAαC, Trp-P-1 and Trp-P-2 were not detected in any of the samples. The outcomes revealed that the formation of HCAs (except harman and norharman) diminished after the addition of food condiments. Edible oil contributed to the highest levels of HCA formation, followed by garlic, paprika, pepper and tomato.     

Effects of cooking methods and levels on formation of heterocyclic aromatic amines in chicken and fish with Oasis extraction method

Heterocyclic aromatic amines (HCAs) are potent mutagenic and carcinogenic compounds formed during heat processing of proteinaceous food such as beef, poultry, and fish. The objective of this study was to measure nine HCAs in chicken chops and fish fillets cooked by various methods (microwave, oven, hot plate, pan-frying, and barbecuing) to different degrees of doneness (rare, medium, well done, and very well done). Total HCA amount in chicken changed between 0.24 and 8.21 ng/g, and not only the highest total amount but also the lowest total HCA amount was found in microwave cooked chicken samples. The highest total HCA amount found in fish for microwave, oven, hot plate, pan-frying, and barbecuing were 18.09, 4.28, 3.12, 6.98, and 5.22 ng/g, respectively. The results show that microwave cooking alone is found to possess the highest total HCA amount, followed by pan-frying, and barbecuing of meat samples, and the total HCA amount in cooked samples is low if cooked to rare and medium degrees of doneness. 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP), 2-amino-9H-pyrido[2,3-b]indole (AαC), and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAαC) were not detected in any samples.     

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).     

Detection and Quantification of 4(5)‐Methylimidazole in Cooked Meat

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.     

Heterocyclic amine content in commercial ready to eat meat products

Heterocyclic amines (HCAs) are produced in meats cooked at high temperature, which are potent mutagens and a risk factor for human cancers. The aim of this study was to estimate the amount of HCAs in some commonly consumed ready-to-eat (RTE) meat products. The RTE products were purchased from a local grocery store, and HCA were analyzed using an analytical method based on solid-phase extraction followed by HPLC. The primary HCAs in these samples were PhIP (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine) (not detected-7.9 ng/g) and MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline) (not detected-3.6 ng/g). Products ranked in order of increasing total HCA content: pepperoni (0.05 ng/g)相似文献   

Determination of Heterocyclic Amines in Meat Matrices Using Enhanced Matrix Removal‐Lipid Extraction and Liquid Chromatography–Tandem Mass Spectrometry

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.     

Amino acid profiles and protein quality of cooked cassava leaves or ‘saka‐saka’

Cassava (Manihot esculenta Crantz) leaves form the main source of protein in a diet consisting of processed cassava roots as sole staple food in konzo‐affected areas of the Democratic Republic of Congo. Pounded cassava leaves were hydrolysed and analysed by HPLC before and after cooking to assess amino acid profiles and protein quality. An average of about 58% loss of total protein content was observed in five different cooked samples. The protein content in cassava leaves was high, an average of 285.9 g kg^?1 dry weight in the raw and 119.2 g kg^?1 dry weight in the cooked samples, but of poor quality, with sulphur amino acids as the most limiting amino acids. Lysine and leucine were also limiting amino acids in some of the raw samples. Lysine, histidine, leucine and isoleucine were limiting amino acids in the cooked samples besides the sulphur amino acids. The consumption of cassava leaves does not compensate the dietary deficiency of sulphur amino acids in the roots that are the staple food in konzo‐affected areas. Sulphur amino acids are essential for detoxification of the residual cyanogens remaining in insufficiently processed cassava roots. Cereals and legumes, as sources of sulphur amino acids and lysine respectively, should be promoted as part of the diet in those areas to prevent the paralytic neuro‐toxico‐nutritional disease konzo among the poor population. Copyright © 2003 Society of Chemical Industry     

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     

Analysis of heterocyclic amines and β-carbolines by liquid chromatography–mass spectrometry in cooked meats commonly consumed in Korea

Heterocyclic amines (HAs), which form in meats during heating and cooking, are recognized as mutagenic and carcinogenic compounds. In this study, 13 HAs and 2 β-carbolines (BCs) were analyzed in cooked Korean meat products, including griddled bacon, griddled pork loin, boiled pork loin, boiled chicken meat, chicken meat stock, chicken breast for salad and chicken patty. The samples were either cooked in the laboratory or purchased from local fast-food restaurants. The HAs and BCs in the samples were separated using solid-phase extraction and were analyzed by high performance liquid chromatography–mass spectrometry (HPLC–MS). The most frequently detected HAs and BCs in the cooked meats were harman (1-methyl-9H pyrido[4,3-b]indole; 990.9 ng g^?1), norharman (9H-pyrido[4,3-b]indole; 412.7 ng g^?1) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine; 258.2 ng g^?1). The griddled pork loin and bacon contained higher levels of norharman, harman and PhIP than the other cooked meats. PhIP, which is classified as a Group 2B carcinogen by the International Agency for Research on Cancer, had levels of 258.2 and 168.2 ng g^?1 in the griddled pork loin and griddled bacon, respectively. The griddled bacon was the only sample containing TriMeIQx (2-amino-3,4,7,8-tetramethylimidazo[4,5-f]quinoxaline; 79.9 ng g^?1). IQ (2-amino-3-methyl imidazo[4,5-f]quinoline), 7,8-DiMeIQx (2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline), 4,8-DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline) and AαC (2-amino-9H-pyrido[2,3-b]indole) were detected at trace levels in all samples.     

Influence of extra virgin olive oil on the formation of heterocyclic amines in roasted beef steak

In this study, heterocyclic anime (HCA) contents were monitored in commonly consumed pan-fried beefsteak based on the highest level of human exposure. Effect of addition of extra virgin olive oil (EVOO) on HCAs formation in fried beef steaks was evaluated. After EVOO was spread on the meat surface, the raw beef was cooked at 200°C for 5 min on each side. The HCAs were extracted from the meat samples and purified using a solid-phase extraction method and then analyzed by liquid chromatography-mass spectrometry (LC-MS). Among the 15 HCAs, 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido [4,3-b]indole (Trp-P-2), 9H-pyrido [3,4-b]indole (Norharman), 1-methyl-9H-pyrido [3, 4-b]indole (Harman), 2-amino-9H-pyrido [2,3-b]indole (AαC), 2-amino-3-methyl-9H-pyrido [2,3-b]indole (MeAαC), 2-amino-3,8-dimethylimidazo [4,5-f]-quinoxaline (MeIQx), and 2-amino-1-methyl-6-phenylimidazo [4,5-b]-pyridine (PhIP) were detected in all of the cooked beefsteaks. HCAs formation was significantly reduced (p<0.05) when the EVOO was added to the beef prior to cooking. The addition of 2 and 4 g of EVOO considerably inhibited HCAs formation in the fried beefsteak. However, adding excess amounts of EVOO promoted some HCAs formation.     

Effects of breeds on the formation of heterocyclic aromatic amines in smoked lamb

Heterocyclic aromatic amines (HAAs) are mutagenic and carcinogenic compounds, which are commonly detectable in cooked meat products. The objective of this study was to evaluate the effect of sheep breeds on the formation of HAAs in smoking cooked lamb. The results showed that HAAs in smoked lamb meat products were generally low (2.74–5.42 ng g^?1), with most being Harman and Norharman. IQ, MeIQx, 4,8‐DiMeIQx, Trp‐p‐2, PhIP and MeAaC were not detected in smoked lamb meat products in the present study. The total content of HAAs differed between meat products of different sheep breeds, but no difference in the order of magnitude was determined. Smoking altered the content of protein, fat, moisture and free amino acids in lamb meat products, which was probably mostly contributed by the reduction in meat moisture. Free tryptophan decreased in all breeds after smoking, which was probably used to synthesise HAAs. In summary, HAAs were low in smoked lamb meat products of all sheep breeds; thus, consumption of smoked lamb meat products should contribute very limited intake of HAAs.     

Inhibition of Heterocyclic Amine Formation in Beef Patties by Ethanolic Extracts of Rosemary

ABSTRACT: Heterocyclic amines (HCAs) are mutagenic compounds formed during cooking muscle foods at high temperature. Inhibition of HCAs by rosemary extracts were evaluated with beef patties cooked at 191 °C (375 °F) for 6 min each side and 204 °C (400 °F) for 5 min each side. Five rosemary extracts extracted with different solvents were used in this study: extract 100W (100% water), 10E (10% ethanol), 20E (20% ethanol), 30E (30% ethanol), and 40E (40% ethanol). The 5 extracts were directly added to beef patties at 3 levels (0.05%, 0.2%, and 0.5%) before cooking and HCA contents were extracted and quantified. All of the patties contained 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), and 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP). There was no statistical difference in the inhibition of HCAs in the 0.05%, 0.2%, and 0.5% rosemary extracts. All rosemary extracts significantly decreased the levels of MeIQx and PhIP at both cooking conditions. When cooking at 204 °C (400 °F) for 5 min each side, rosemary extracts 10E and 20E were superior to rosemary extracts 100W, 30E, and 40E in inhibiting HCA formation. Rosemary extract 20E showed the greatest inhibition of MeIQx (up to 91.7%) and PhIP (up to 85.3%). The inhibiting effect of rosemary extracts on HCA formation corresponded to their antioxidant activity based on a DPPH scavenging assay. Rosemary extract 10E and 20E contain a mixture of rosmarinic acid, carnosol, and carnosic acid. It is possible that these compounds might act synergistically in inhibiting the formation of HCAs.     

Formation of heterocyclic aromatic amines in doner kebab cooked with different methods at varying degrees of doneness

This study was designed to determine the formation of heterocyclic aromatic amines (HCAs) in two different types of doner kebab (yaprak doner-YD or mix doner-MD) cooked with different cooking methods (gas or electric) at varying degrees of doneness (rare, medium, well-done). In doner samples, nine common HCAs (IQ, IQx, MeIQ, MeIQx, PhIP, 4,8-DiMeIQx, 7,8-DiMeIQx, AαC, MeAαC) were detected. Additionally, the changes in the HCA precursors were evaluated. The initial concentration of precursors gradually decreased with the increase in doneness degree due to degradation or possible contribution in the Maillard reaction to form HCA compounds as a result of heat treatment (p < 0.05). Creatine content decreased, while creatinine content increased because of the conversion reaction. The two most abundant HCA in doner samples were 4,8-DiMeIQx and IQ, which measured in the range of 0.020–2.865 ng g^?1 and 0.052–0.513 ng g^?1, respectively. Other detected HCAs were determined in especially well-done samples. In conclusion, the diversity and the amount of each HCA compound in doner kebab samples showed variation depending on the effect of doneness degree, doner kebab type or cooking methods (p < 0.05).     

Amino Acids Inhibitory Effects and Mechanism on 2‐Amino‐1‐Methyl‐6‐Phenylimidazo [4,5‐b]Pyridine (PhIP) Formation in the Maillard Reaction Model Systems

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.     

Concentration of Umami Compounds in Pork Meat and Cooking Juice with Different Cooking Times and Temperatures

This study examined the concentrations of umami compounds in pork loins cooked at 3 different temperatures and 3 different lengths of cooking times. The pork loins were cooked with the sous vide technique. The free amino acids (FAAs), glutamic acid and aspartic acid; the 5′‐nucleotides, inosine‐5′‐monophosphate (IMP) and adenosine‐5′‐monophosphate (AMP); and corresponding nucleoside inosine of the cooked meat and its released juice were determined by high‐performance liquid chromatography. Under the experimental conditions used, the cooking temperature played a more important role than the cooking time in the concentration of the analyzed compounds. The amino acid concentrations in the meat did not remain constant under these experimental conditions. The most notable effect observed was that of the cooking temperature and the higher amino acid concentrations in the released juice of meat cooked at 80 °C compared with 60 and 70 °C. This is most likely due to the heat induced hydrolysis of proteins and peptides releasing water soluble FAAs from the meat into the cooking juice. In this experiment, the cooking time and temperature had no influence on the IMP concentrations observed. However, the AMP concentrations increased with the increasing temperature and time. This suggests that the choice of time and temperature in sous vide cooking affects the nucleotide concentration of pork meat. The Sous vide technique proved to be a good technique to preserve the cooking juice and the results presented here show that cooking juice is rich in umami compounds, which can be used to provide a savory or brothy taste.     

Content,causes and analysis of heterocyclic amines in Chinese traditional braised chicken

ABSTRACT

Braised chicken is a popular traditional chicken product in China with a special and complicated culinary method. However, there has been little research focused on the food safety problems caused by hazardous compounds in braised chicken. In this study, the contents of heterocyclic amines (HCAs) in representative braised chicken samples were determined. Total HCAs in braised chicken were relatively high (6.20–27.7 ng g^?1), and aminoimidazoazaarenes (AIAs) took a large proportion (54.0–86.4%). 2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) was found in all samples with a high level (2.72–13.5 ng g^?1), whilst 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was low (0.14–0.41 ng g^?1). 9H-pyrido[3,4-b]indole (Norharman) and 1-methyl-9H-pyrido[3,4-b]indole (Harman) were main components in aminocarbolines (ACs). So the potential safety risk in braised chicken caused by high HCAs content should be paid attention. Principal component analysis (PCA) was used to analyse and visualise the differences of HCAs levels among braised chicken samples. The result indicated that the differences among these samples were significant, but there were no obvious similarities between samples produced in the same regions. Moreover, there were rare significant positive correlations between chemical components (including moisture, fat, protein, creatine and free amino acids) and hazardous compounds. Considering PCA and correlation analysis results, these parameters may play a major role in the HCAs levels in Chinese traditional braised chicken.     

Concentration-dependent inhibition of Escherichia coli O157:H7 and heterocyclic amines in heated ground beef patties by apple and olive extracts,onion powder and clove bud oil

The effects of plant compounds on Escherichia coli O157:H7 and two major heat-induced heterocyclic amines (HCAs) MeIQx and PhIP in grilled ground beef patties were determined. Ground beef with added apple and olive extracts, onion powder, and clove bud oil was inoculated with E. coli O157:H7 (10⁷ CFU/g) and cooked to reach 45 °C at the geometric center, flipped and then cooked for another 5 min. Cooled samples were taken for microbiological and HCA analyses. Olive extract at 3% reduced E. coli O157:H7 to below detection. Reductions of up to 1 log were achieved with apple extract. Olive and apple extracts reduced MeIQx by up to 49.1 and 50.9% and PhIP by up to 50.6 and 65.2%, respectively. Onion powder reduced MeIQx and PhIP by 47 and 80.7%, respectively. Inactivation of E. coli O157:H7 and suppression of HCAs in grilled meat were achieved by optimized amounts of selected plant compounds.