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K Skog

Publications and source records attributed to K Skog.

18 recordsLinked to original sources
PubMed1998

Analysis of nonpolar heterocyclic amines in cooked foods and meat extracts using gas chromatography-mass spectrometry.

Heat processing of muscle foods gives rise to the formation of mutagenic and carcinogenic heterocyclic amines, often at ng/g levels. A gas chromatographic-mass spectrometric (GC-MS) technique was introduced for the analysis of nonpolar heterocyclic amines in common cooked meats, pan residues, and meat extracts after solid-phase extraction. The mutagenic heterocyclic amines 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), 2-amino-9H-pyrido[2,3-b]indole (A alpha C) and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeA alpha C) were identified in several samples in amounts up to 8 ng/g. Also the comutagenic substances 1-methyl-9H-pyrido [3,4-b]indole (harman) and 9H-pyrido[3,4-b]indole (norharman) were detected in the samples in amounts up to almost 200 ng/g. The GC-MS method can be applied without derivatisation of the sample. The technique offers high chromatographic efficiency, yielding detection limits for pure references in the range 0.1-2 ng per injection.

Amines↗
PubMed1997

Trigonelline, a naturally occurring constituent of green coffee beans behind the mutagenic activity of roasted coffee?

Trigonelline and amino acids are natural components in green coffee beans. Model systems mimicking coffee roasting were used to produce heated samples of trigonelline, amino acids and glucose. Trigonelline and amino acids were heated separately or in combinations for 20 min at 250 degrees C. The results of bacteria mutation assays (Salmonella typhimurium strains TA 98, YG 1024 and YG 1029) showed that trigonelline, alone or in combination with most of the single amino acids and mixtures of amino acids, yielded potent mutagenic activity. Of the singly heated compounds, the highest mutagenic activity was found for trigonelline. The mutagenic activity detected with metabolic activation of the heated trigonelline samples indicated that the mutagenic compounds might be amines; however, higher mutagenic activity was found for trigonelline and its combinations without metabolic activation, which suggests that other types of mutagens (direct-acting) were predominant. High-performance liquid chromatographic analysis of some of the heated samples did not reveal the presence of any known mutagenic heterocyclic amine.

Alkaloids↗
PubMed1997

Polar and non-polar heterocyclic amines in cooked fish and meat products and their corresponding pan residues.

Fourteen cooked dishes with their corresponding pan residues were analysed for polar and non-polar heterocyclic amines using HPLC. The choice of foods, including beef, pork, poultry, game, fish, egg and sausages, was based on an investigation of an elderly population in Stockholm participating in an analytical epidemiological case-control study on cancer risks after intake of heterocyclic amines. The food items were prepared using normal household cooking practices, and to reflect the wide range of surface browning of the cooked dishes that would be encountered in this population, four cooking temperatures were used in the range 150-225 degrees C. For all food samples, the total amount of heterocyclic amines formed at 150 degrees C was less than 1 ng/g cooked product, and at 175 degrees C less than 2 ng/g. The highest concentrations of heterocyclic amines were detected in fillet of pork, reindeer meat and chicken breast fried at 200 and 225 degrees C and their corresponding pan residues. The total sum of 2-amino-3,8-dimethylimidazo-[4,5-f]quinoxaline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine was about 1 microgram per 100 g portion (including pan residues) for reindeer meat and chicken breast, and between 1.9 and 6.3 micrograms per 100-g portion for fillet of pork. PhIP was the most abundant heterocyclic amine, identified in 73 of 84 samples, and the highest concentration of PhIP, 32.0 ng/g, was found in the pan residue from fillet of pork cooked at 225 degrees C. The non-polar heterocyclic amines 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole and 3-amino-1-methyl-5H-pyrido[4,3-b]indole were detected in the range of 0.5-7.4 ng/g in most foods cooked at 225 degrees C, and also in meat sauce prepared at 200 and 175 degrees C. The other heterocyclic amines tested for: 2-amino-3-methylimidazo-[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-6-methyl-pyrido-[1,2-a:3',2'-d]-imidazole and 2-aminodipyrido-[1,2-a:3',2'-d]imidazole, were present only at very low or non-detectable levels. The low recoveries of the amino-alpha-carbolines 2-amino-9H-pyrido[2,3-b]indole and 2-amino-3-methyl-9H-pyrido[2,3-b]indole made it impossible to quantify them. However, the co-mutagenic substances 1-methyl-9H-pyrido-[3,4-b]indole and 9H-pyrido[3,4-b]indole were detected at levels of about 1-30 ng/g in most of the dishes cooked at 200 and 225 degrees C.

Amines↗
PubMed1997

Assessment of the human exposure to heterocyclic amines.

Heterocyclic amines are possible human carcinogens and fried meat is an important source of exposure in the Western diet. To study the effect of heterocyclic amines in humans, accurate assessment of individual food consumption is essential. Parameters influencing the intake include the amount and type of meat ingested, frequency of consumption, cooking method, cooking temperature and the duration of cooking. The aim of the present study was to develop a practical method for assessing individual intakes of specific heterocyclic amines in a large sample of people. This has been done by combining information on food consumption and laboratory findings of heterocyclic amines in food products. Diet was assessed using a semi-quantitative food frequency questionnaire including photos of fried meat and, in all, 22 dishes were cooked and chemically analyzed. The method was employed in an elderly population in Stockholm to estimate the daily mean intake of the five heterocyclic amines 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). The total daily intake ranged from none to 1816 ng, with a mean intake of 160 ng, which is well below estimates reported previously. Highest amounts ingested were of PhIP (mean 72, range 0-865 ng/day) and MeIQx (mean 72, range 0-1388 ng/day), followed by DiMeIQx (mean 16, range 0-171 ng/day), while MeIQ and IQ were ingested only in very small amounts (mean <1 ng/day).

Aged↗
PubMed1995

Effect of cooking temperature on the formation of heterocyclic amines in fried meat products and pan residues.

Frequent consumers of meat have an increased risk of colorectal cancer and possibly also of breast, stomach, pancreas and urinary bladder cancer. Bacon, 'Falusausage', ground beef, meatballs, pork belly, pork chops and sliced beef account for more than one-third of the intake of fried meat of the population of Stockholm of age 50-75. These dishes were fried at four temperatures (150, 175, 200 and 225 degrees C) representing normal household cooking practices in Stockholm. Heterocyclic amines in these dishes were analysed using solid-phase extraction and HPLC. The heterocyclic amines 2-amino-3-methylimidazo[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 (DiMeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were recovered. The formation of IQ was favoured by moderate cooking temperatures; IQ was detected in one meat sample cooked at 150 degrees C and in some pan residues. The yield of MeIQx, DiMeIQx and PhIP increased with the temperature. For several of the meat dishes, the content of heterocyclic amines in the pan residue was as large or larger than for corresponding piece of meat. The highest levels of MeIQx were 23.7 ng/g in the meat and 23.3 ng/g in the pan residue. Corresponding data for DiMeIQx were 2.7 and 4.1 ng/g and for PhIP 12.7 and 82.4 ng/g. The study leaves little doubt that mutagenic heterocyclic amines are ingested by the population of Stockholm, and added to previous epidemiological studies from the same area, the combined data are consistent with human carcinogenicity of heterocyclic amines. However, analytical epidemiological studies are needed before any statement on causality can be made.

Aged↗
PubMed1995

Factors affecting the formation and yield of heterocyclic amines.

The main food mutagens found in cooked meat products are heterocyclic amines. The formation of these heterocyclic amines has been shown to require three classes of precursors: (i) creatine/creatinine, (ii) free amino acids or dipeptides, and (iii) sugar. The mutagen forming reactions were investigated in model systems and several heterocyclic amines (IQx, MeIQx, DiMeIQx, TriMeIQx and PhIP) were identified and quantified. A number of mutagenic fractions produced in the model system are not yet identified, among them one having a mass number of 217. A participation of the Maillard reaction in the formation of the heterocyclic amines was proposed ten years ago. Since then, the support for this route has increased, especially in a recent study in which carbon atoms from 14C-labelled glucose were shown to be incorporated into MeIQx and DiMeIQx. Other studies have shown sugar to either enhance or inhibit the yield of mutagenic activity depending on its molar ratio relative to the other reactants. Thus, the Maillard reaction can be utilized both to enhance and inhibit the formation of the heterocyclic amines. Olive oil and corn oil were found to almost double the yield of MeIQx in the model system after heating for 30 minutes at 180 degrees C. When adding deep-fat frying oil of different oxidation status in the model system, the yield of MeIQx was not affected by oxidation status or presence of vitamin E, but the lipids enhanced the formation of MeIQx by 30% after heating at 180 degrees C for 30 minutes. Artificial production of free radical reactions by adding FeSO4, hydrogen peroxide and oxygen to the model system doubled the yield of MeIQx.

Carcinogens↗
PubMed1993

Cooking procedures and food mutagens: a literature review.

Commonly eaten meat products prepared from beef, pork, mutton and chicken show some level of mutagenic activity following normal frying. Food preparation methods have a significant influence on the formation of the mutagenic activity. The main food mutagens found in cooked meat products are heterocyclic amines. Several of them have been tested in long-term animal studies and shown to be carcinogenic in rodents. From a health point of view, it is desirable to reduce or prevent the formation of food mutagens. Therefore, a deeper understanding of the precursors and reaction conditions for mutagen formation during normal domestic cooking is very important. Modelling experiments are useful tools for studying the influence of different physical parameters and various precursors on the mutagenic activity. The identification of several thermic mutagens from the modelling experiments support the theory that creatine or creatinine, amino acids and sugars are precursors in the formation of thermic mutagens. Creatine is generally accepted to be a precursor of the mutagens and, interestingly, the conversion of creatine to creatinine has been shown to be blocked by an excess of sugars, which also caused the mutagenic activity to decrease. The mutagenic activity differed for different amino acids used in the model systems, and various thermic mutagens were produced from the amino acids. The incorporation of carbon atoms originating from glucose into food mutagen molecules has shown glucose to be a precursor. Sugar has also been shown to either enhance or inhibit the yield of mutagenic activity, depending on its molar ratio versus the other reactants, which suggests that the Maillard reaction may be used to control the formation of mutagens.

Animals↗
PubMed1993

Effects of edible oils and fatty acids on the formation of mutagenic heterocyclic amines in a model system.

The effects of glycerol, fatty acids and oils on the yield and species of mutagenic heterocyclic amines were studied in a model system. The addition of lipids to the model system did not affect the species of food mutagens formed, but did affect the yield of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). When heating creatinine, glycine and glucose dissolved in water, at 180 degrees C for 10 and 30 min, 9 and 18 nmol MeIQx/mmol creatinine were formed respectively. Corresponding figures of MeIQx formed, after addition of various fatty acids or edible oils to the model system, were as follows: oleic acid (9 and 11 nmol MeIQx/mmol creatinine), stearic acid (16 and 19 nmol), linoleic acid (8 and 16 nmol), linolenic acid (5 and 20 nmol), corn oil (10 and 33 nmol) and olive oil (10 and 28 nmol) after heating at 180 degrees C for 10 and 30 min respectively. Addition of corn or olive oil in a model system heated at 180 degrees C for 30 min, almost doubled the yield of MeIQx formed, compared with the amount formed in a model system without fat. This increase was not observed if glycerol or a fatty acid was added to the model system.

Amines↗
PubMed1993

Incorporation of carbon atoms from glucose into the food mutagens MeIQx and 4,8-DiMeIQx using 14C-labelled glucose in a model system.

Mixtures of creatinine, glucose and threonine with the addition of a small amount, 250 microCi, of [U-14C]glucose, [1-14C]glucose or [6-14C]glucose were heated at 180 degrees C for 30 min in an aqueous model system. The mixtures were purified and analysed using HPLC, scintillation and Ames tests. 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) were detected as the main radioactive mutagens. The amount of MeIQx and 4,8-DiMeIQx produced from threonine was estimated at 18 and 60 nmol/mmol glucose respectively. Radioactive carbon atoms originating from glucose were also shown to be incorporated into 2-amino-3-methylimidazo[4,5-f]quinoxaline (IQx). The specific activity was calculated to be 0.6, 0.3 and 0.1-0.3 mCi/mmol for MeIQx, 4,8-DiMeIQx and IQx respectively for all three labelled forms of glucose. By the incorporation of carbon atoms originating from glucose into the imidazoquinoxaline mutagens it was clearly demonstrated that glucose is a precursor in the formation of these food mutagens.

Carbon↗
PubMed1992

Formation of new heterocyclic amine mutagens by heating creatinine, alanine, threonine and glucose.

A mixture of alanine, threonine, creatinine and glucose was heated in diethylene glycol and water (5:1, v/v) for 15 min at 200 degrees C. The mutagens formed were purified by high-performance liquid chromatography using the Ames/Salmonella mutagenic activity to guide the purification. The structures of the purified mutagens were determined using UV absorption, mass and NMR spectrometry. A new mutagenic compound with a mass number of 217 was found and its mass spectrum did not correspond to any known mutagen derived from food. This new compound accounted for 4% of the total mutagenic activity. Other mutagenic compounds were identified as MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline), 4,8-DiMeIQx (2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline), and a new mutagen 4,7,8-TriMeIQx (2-amino-3,4,7,8-tetramethylimidazo[4,5-f]quinoxaline) with a mutagenic activity of 73,000 TA98 revertants per microgram. The percentage of the mutagenic activity attributable to MeIQx, 4,8-DiMeIQx and 4,7,8-TriMeIQx was 10%, 70% and 3%, respectively. The yield of MeIQx, 4,8-DiMeIQx and 4,7,8-TriMeIQx was 10, 36 and 6 nmole/mmole creatinine. The formation of TriMeIQx from natural meat components suggests that this new quinoxaline mutagen may be present in cooked foods.

Alanine↗
PubMed1992

Inhibitory effect of carbohydrates on the formation of mutagens in fried beef patties.

Beef patties were prepared by mixing minced meat with water and either glucose (1, 2 or 4%), lactose (1, 2 or 4%) or powdered milk (2, 4 or 8%) before frying. In another experiment, minced meat was mixed with starch from golden bread crumbs (3%) or potatoes (4%), with and without glucose (1, 2 or 4%). The patties (100 g) were fried for 3 min at 150 or 180 degrees C in a double-sided fryer. The mutagenic activity in the crust was determined using the Ames test. With the addition of glucose or lactose (1-4%), the mutagenic activity was inhibited by 34-76%. A similar inhibition of the mutagenic activity was obtained with powdered milk. However, starch from golden bread crumbs or potatoes caused only a slight (not significant) decrease in mutagenic activity whereas adding both starch and glucose to the beef patties inhibited mutagenic activity by up to 54%.

Animals↗
PubMed1991

Formation of meat mutagens.

The formation of meat mutagens has been studied the last 10 years by carrying out modeling and meat cooking experiments in parallel. During this time, the list of meat mutagens has been growing, and continues to grow. The meat mutagens are usually produced in the crust of animal foods during frying, broiling, and baking. Another important source is meat extracts, consumed as gravies and meat bouillons. The formation of meat mutagens has been shown to depend physically on time, temperature, and water. Three major precursors have been identified: creatine or creatinine, certain amino acids, and monosaccharides or disaccharides. A requirement of sugar assumes a participation of the Maillard reaction, which also forms the basis for one of the major reaction mechanisms suggested. However, the meat mutagens are produced also in the absence of sugars, which means that other routes might be possible as well. Although the major precursors have been identified, more work needs to be done on the reaction mechanisms, the kinetics, and on the food constituents that might enhance or inhibit the formation of the meat mutagens. The results obtained to date point to several possibilities to control the formation of meat mutagens.

Animals↗
PubMed1991

Effects of glucose on the formation of PhIP in a model system.

The effect of glucose on the formation of the food mutagen PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) was studied in a model system. When a mixture of creatine (0.9 mmol), phenylalanine (0.9 mmol) and glucose (0.45 mmol) was heated in diethylene glycol and water (3 ml, 5:1) for 10 min at 180 or 225 degrees C several mutagens were produced. Identification by HPLC, UV absorption spectroscopy and mass spectrometry revealed the presence of PhIP as well as 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and minor amounts of 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline. Heating the system without glucose produced PhIP as a single mutagen, but in considerably lower amount. An inhibiting effect of glucose in high concentrations was demonstrated. When glucose was added in more than or equimolar amounts of the other two reactants, the formation of mutagens was markedly reduced. Tyrosine heated under the same conditions, with creatine and glucose, showed mutagenic activity. However, no PhIP nor any other known food mutagen was identified from the tyrosine mixture.

Creatine↗
PubMed1990

Effects of monosaccharides and disaccharides on the formation of food mutagens in model systems.

The formation of the mutagenic imidazoquinoxalines (MeIQx, DiMeIQx) was studied using a modification of a previous model system. Creatine or creatinine (0.9 mmole) was heated together with glycine (0.9 mmole) and various sugars (0.45 mmole) dissolved in diethylene glycol and water (3 ml, 5:1) for up to 15 min at 180 degrees C. This system produced the same amount of mutagenicity after 10 min at 180 degrees C as a previous one during 2 h of reflux boiling at 128 degrees C. MeIQx (4 nmole/mmole creatin(in)e) was the major mutagen produced together with minor amounts of DiMeIQx, both 4,8- and 7,8-DiMeIQx according to HPLC-MS. A few other mutagenic peaks were also separated on HPLC, but they were not identified. Varying the concentration (0-2.4 mmole) and type of monosaccharides and disaccharides greatly affected the yields of all the mutagenic compounds. Sugar in molar amounts lower than the creatin(in)e concentration increased the yield until an optimum was reached. In higher concentrations the formation of all the mutagens was markedly reduced. The same was found for glucose, fructose, sucrose, and lactose, though the monosaccharides showed the most pronounced inhibitory effects. The inhibition of the formation of the mutagenic compounds by an excess of sugars is proposed to be an effect of Maillard reaction products, which may block the formation of imidazoquinoxalines by attacking creatine. Support for this mechanism is given by data showing a lower recovery of unreacted creatine with increasing concentration of glucose and also by an inhibitory effect on the formation of these mutagens after adding a typical Maillard reaction product, 5-hydroxymethyl-2-furfural.

Chromatography, High Pressure Liquid↗
PubMed1987

Effects of creatine and creatinine content on the mutagenic activity of meat extracts, bouillons and gravies from different sources.

Thirteen commercial meat-flavour samples were analysed for creatine and creatinine content and tested for mutagenicity in the Ames Salmonella/microsome test. In most samples, more than 50% of the creatine had been converted to creatinine. Mutagenicity was related to the creatinine content: 150 mumol creatinine/g dry matter (gdm) gave upwards of 2500 revertants/gdm, concentrations of 15-40 mumol/gdm gave about 100 revertants/gdm and concentrations of 1-10 mumol/gdm gave only low or no significant mutagenicity. No relationship was apparent between coloration and mutagenicity. Beef steaks (initial weight c. 500 g) baked at oven temperatures between 115 and 245 degrees C only showed significant mutagenicity--135 revertants/100 gE (initial raw weight)--in the crust when baked at the highest temperature (245 degrees C). The gravies (meat-juice drip) collected during baking showed a linear increase in mutagenicity with baking temperatures up to 180 degrees C (48-828 revertants/100 gE) and a very sharp increase in mutagenicity for the gravy collected from beef steak baked at 245 degrees C (28,300 revertants/gdm or 19,800 revertants/100 gE). At this high temperature, the brown coloration and the proportion of creatinine to total creatine and creatinine were also dramatically increased, because this gravy dried up completely during the baking procedure.

Animals↗
PubMed1987

Mutagenicity of pan-fried bovine tissues in relation to their content of creatine, creatinine, monosaccharides and free amino acids.

The mutagenicity of pan-fried patties of five bovine tissues (meat, heart, tongue, liver and kidney) containing various concentrations of creatine, monosaccharides and free amino acids were studied. Two experiments were performed, one on single tissues fried at 150, 175 or 200 degrees C for 3 min and the other on mixtures of meat and one of the other four tissues in various proportions, fried at 200 degrees C for 3 min. For both experiments, a double-sided Teflon-coated plate was used. Frying at 150 degrees C induced mutagenicity to Salmonella typhimurium strain TA98 only in the heart sample-6000 revertants/100 gE (grams initial raw weight). Meat, heart and tongue fried at 175 or 200 degrees C showed mutagenicity values between 6000 and 19,600 revertants/100 gE. A linear relationship between mutagenicity and temperature was obtained for each of the three muscles and creatine was converted to creatinine with increasing temperature. Liver or kidney samples fried alone showed insignificant mutagenicity at all three temperatures. The creatine plus creatinine levels of raw meat, heart and tongue samples were between 19 and 33 mumol/g wet tissue. Liver and kidney both showed very low amounts of creatine plus creatinine (about 2 mumol/g wet tissue) in the raw tissue, while free amino acids were high. Glucose levels were high in liver but low in kidney samples. In meat/heart and meat/tongue mixtures the mutagenicity varied between 10,800 and 17,300 revertants/100 gE. The meat/liver and meat/kidney mixtures showed linear relationships between mutagenicity and the proportions of the mixture. The values for the slopes and intercepts of the two lines were almost equal. Among the three groups of precursors (creatine plus creatinine, monosaccharides and free amino acids) the creatine plus creatine in raw tissue seems to be the most important for producing mutagenicity. However, in crusts, the creatinine concentration was the variable with which most of the mutagenicity was associated.

Amino Acids↗
PubMedDate not supplied

Formation of heterocyclic amines using model systems.

Initially, modeling was used to identify the mutagenic heterocyclic amines and their precursors. Major precursors have been shown to be single amino acids or amino acids together with creatine or creatinine. There is also evidence that Maillard reactions are involved since heating sugar and amino acids together with creatine or creatinine has been shown to produce several of the mutagenic heterocyclic amines, especially the aminoimidazoazaarenes (AIA compounds), e.g., IQ, MeIQ, MeIQx, DiMeIQx and PhIP. Due to a low yield in the model systems, the mechanisms behind the formation of the mutagenic heterocyclic amines are still unclear and need further substantiation. The fact that some AIA compounds are also produced in the absence of sugar casts some doubts on an obligatory participation of the Maillard reaction; alternative routes might exist. Further work using isotopically labeled precursors needs to be done and so far such work has only been performed for PhiP. The formation of mutagenic heterocyclic amines is dependent on time, temperature, pH, concentration of the precursors, type of amino acid, and the presence of certain divalent ions. Water may have an impact both as a temperature regulator and as a solvent medium for the reactants.

Amines↗