Acute poisonings treated in hospitals in Oslo: a one-year prospective study (I): pattern of poisoning.

OBJECTIVES: Prospective design is mandatory to study pattern of poisoning and suicidal intention of patients. MATERIAL AND METHODS: Prospective cross-sectional multi-center study of all patients contacting health care services because of acute poisoning during one year in Oslo, irrespective of intention. Data on the adult hospitalized patients (> or = 16 years) are presented here. RESULTS: Of a total of 3,775 such adult contacts (3,025 episodes), there were 947 (31 %) hospitalizations; annual incidence 1.9 (per 1,000) in males and 2.1 in females. Median age was 36 years (range 16-89); 54% females. Benzodiazepines (18%), ethanol (17%), paracetamol (12%), opioids (7%), and gamma hydroxybutyric acid (GHB) (7%) were most frequently taken. Patients stated suicidal intention in 29% of the admissions; physicians in 10%. CONCLUSION: Benzodiazepines and ethanol were the most common agents, but newer illicit drugs were frequent, especially GHB. Males often took ethanol and drugs of abuse; females often used prescription drugs with suicidal intention.

Liquid chromatography-tandem mass spectrometry analysis of 2-amino-1-methyl-6-(4-hydroxyphenyl)imidazo[4,5-b]pyridine in cooked meats.

Several cooked meats such as beef (fried, coated-fried), pork (fried, coated-fried), and chicken (fried, griddled, coated-fried, roasted) were analyzed for the heterocyclic amine 2-amino-1-methyl-6-(4-hydroxyphenyl)imidazo[4,5- b]pyridine (4'-OH-PhIP) not commonly determined in food and 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP). The highest content of 4'-OH-PhIP was found in fried and griddled chicken breast, the concentration being 43.7 and 13.4 ng/g, respectively, whereas the corresponding PhIP concentrations were 19.2 and 5.8 ng/g. The estimated concentration of both pyridines in fried pork loin, in fried pork sausages, and in coated-fried chicken was below 2.5 ng/g. In the rest of the samples, 4'-OH-PhIP was not detected. The analyses were performed by solid-phase extraction and LC-MS/MS. The fragmentation of 4'-OH-PhIP in an ion trap mass analyzer was studied in order to provide information for the identification of 4'-OH-PhIP. Additionally, the effect of red wine marinades on the formation of 4'-OH-PhIP in fried chicken was examined, finding a notable reduction (69%) in the amine's occurrence.

Canavanine content in sword beans (Canavalia gladiata): analysis and effect of processing.

The amino acid canavanine is a potentially toxic constituent of leguminous seeds. The aim of the present study was to determine the ability of different processing methods to reduce canavanine in sword beans (Canavalia gladiata). For this purpose a method for the detection and quantification of canavanine was developed using reversed-phase high-performance liquid chromatography of the dabsylated derivatives. The recovery of canavanine using this method was 88-91%. Optimum extraction of canavanine from raw and processed beans was obtained by addition of hot water prior to overnight soaking. The results obtained with this method agree well with previously published values for raw seeds. The method is sensitive, specific and can successfully be applied to the detection of canavanine in legumes. Overnight soaking and boiling in excess water followed by decanting gave the most pronounced reduction in canavanine content (around 50%), followed by boiling and decanting excess water (34%). Roasting as used in this study and autoclaving were less effective in reducing the canavanine content.

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.

Exposure to beta-carbolines norharman and harman.

The aromatic beta-carbolines norharman and harman have been implicated in a number of human diseases including Parkinson's disease, tremor, addiction and cancer. It has been shown that these compounds are normal body constituents formed endogenously but external sources have been identified. Here, we summarise literature data on levels of norharman and harman in fried meat and fish, meat extracts, alcoholic drinks, and coffee brews. Other sources include edible and medicinal plants but tobacco smoke has been identified as a major source. Exposure levels from these different dietary sources are estimated to a maximum of 4 microg norharman per kg body weight (bw) per day and 1 microg harman per kg bw per day. Exposure via tobacco smoke depends on smoking habits and type of cigarettes but can be estimated to 1.1 microg/kg bw for norharman and 0.6 microg/kg bw for harman per package of cigarettes smoked. Studies on toxicokinetics indicate that inhalative exposure leads to a rapid increase in plasma levels and high bioavailability of norharman and harman. Oral bioavailability is lower but there are indications that sublingual absorption may increase dietary uptake of beta-carbolines. Endogenous formation can be estimated to be 50-100 ng/kg bw per day for norharman and about 20 ng/kg bw per day for harman but these rates may increase with high intake of precursors. Biomarker studies on plasma levels of beta-carbolines reported on elevated levels of norharman, harman or both in diseased patients, alcoholics and following tobacco smoking or consumption of beta-carboline-containing food. Cigarette smoking has been identified as major influence but dietary exposure may contribute to exposure.

Analysis of heterocyclic amines in food products: interlaboratory studies.

A feasibility study and two interlaboratory exercises on the determination of selected heterocyclic amines (HAs) in beef extract, organised in the framework of a European project, are presented. The aim of these exercises was to improve the quality of the laboratories and to evaluate the performance of a standardised analytical method and also the methods currently used by each of the participants for the analysis of these compounds. Three lyophilised portions of a commercial beef material previously spiked with HAs at different concentration levels ranging from 10 to 75 ng g(-1) were used as laboratory reference materials (lot A, B and C). Firstly, a feasibility study was carried out using a test standard solution and the beef extract (lot A), which contained only five HAs. Then, two interlaboratory exercises were carried out using the laboratory reference materials lot B and lot C, containing 10 selected HAs at two different concentration levels, 75 and 10 ng/g, respectively. The results obtained by all participant laboratories using the proposed method showed satisfactory agreement and the CV(%) between-laboratories obtained were from 8.3 to 24.1% for lot B and from 8.7 to 44.5% for lot C. The standardised method evaluated in these collaborative studies is therefore proposed for the analysis of HAs in food material. Moreover, LC-MS is recommended as the most suitable technique for the analysis of a large number of HAs in food samples.

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.

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.

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.

Inhibitory effect of threo-9,10-dichlorostearic acid on the mutagenic activity of MeIQx, 2-AF and B[a]P in the Ames/Salmonella test.

The mutagenic activity of threo-9,10-dichlorostearic acid, one of the chlorinated fatty acids identified in fish lipids, was examined in the Ames/Salmonella test. No mutagenic activity was found on any of the Salmonella typhimurium strains TA 98, TA 100 and TA 102, either with or without S9 activation. On the other hand, dichlorostearic acid showed an inhibitory effect on the mutagenic activity of the indirectly-acting mutagens 2-amino-3, 8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-aminofluorene (2-AF) and benzo[a]pyrene (B[a]P) using strain TA 98 in the presence of S9. However, no inhibition was observed when mixing MeIQx and S9 before the addition of dichlorostearic acid. Furthermore, dichlorostearic acid did not show any inhibitory effect on the mutagenic activity of the directly-acting mutagen 4-nitroquinoline-N-oxide (4NQO) using the tester strains TA 98 and TA 100. We, therefore, suggest that dichlorostearic acid interacts with the enzymes of the S9 mix, thereby dose-dependently inhibiting the transformation of MeIQx, 2-AF and B[a]P into their active forms.

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.

Characterization of phenolic compounds in virgin olive oil and their effect on the formation of carcinogenic/mutagenic heterocyclic amines in a model system.

Mutagenic heterocyclic amines (HAs) are formed at low levels during cooking of meat and fish, and some of them are considered to be possible human carcinogens. The formation of HAs may be affected by the presence of synthetic or naturally occurring antioxidants. In the present study the effect of virgin olive oil (VOO) phenolic compounds, identified and quantified by LC-MS, on the formation of HAs in a model system was evaluated. An aqueous solution of creatinine, glucose, and glycine was heated in the presence of two samples of VOO differing only in the composition of phenolic compounds. The addition of VOO to the model system inhibited the formation of 2-amino-3-methylimidazo[4,5-f]quinoxaline (IQx), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) by between 30 and 50% compared with the control. Fresh-made olive oil, which contained a high amount of dihydroxyphenylethanol derivatives, inhibited HA formation more than a 1-year-old oil did. The inhibition of HA formation was also verified using phenolic compounds extracted from VOO.

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.

Problems associated with the determination of heterocyclic amines in cooked foods and human exposure.

Epidemiological studies have shown diet to be an important factor in the global variation of human cancer rates. The presence of mutagenic/carcinogenic heterocyclic aromatic amines (HAs) in cooked foods has attracted a great deal of interest for more than 20 years. Accurate assessment of the human exposure to HAs requires food questionnaires that address cooking methods and reliable methods for the analysis of HAs in cooked foods, and of biomarkers of exposure. The complex food matrix, the low amounts of HAs present (ng/g), and the need for several isolation steps make accurate quantification difficult. Food composition, for example the concentrations and relative amounts of naturally occurring precursors, such as creatine, free amino acids and sugars and also the presence of enhancing or inhibiting compounds are known to greatly influence the formation of HAs. Cooking temperature and time are other important factors that affect the yield of HAs. One of the most abundant HAs, PhIP (2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine), is found typically in amounts up to around 35 ng/g, but there are some reports on much higher levels of PhIP. The levels of other HAs such as MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline) and IFP (2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine) generally range from not detectable up to 10 ng/g, and AalphaC (2-amino-9H-pyrido[2,3-b]indole) up to 20 ng/g. Among the factors that influence human exposure to HAs are the type of food, cooking method, portion size and intake frequency. The estimated daily intake of HAs in different studies ranges from 0 to around 15 microg per person per day.

Heterocyclic amines in poultry products: a literature review.

Health risks associated with heterocyclic amines in cooked foods have been discussed and analysed since the presence of these food mutagens was first detected. Intake, metabolism, carcinogenicity and epidemiology are important parameters in the risk assessment of heterocyclic amines. It is very difficult to determine the human intake of heterocyclic amines, as the content in cooked meat is highly dependent on the type of meat and how it has been prepared. This review summarises data on estimates of the content of heterocyclic amines in heat-treated poultry products.

Screening for heterocyclic amines in chicken cooked in various ways.

Chicken cooked under well-controlled conditions and commercial chicken products were screened for heterocyclic amines (HAs). Chicken samples were boiled, deep-fried, pan-fried, oven-roasted, cooked in an unglazed clay pot or in a roasting bag in the oven, and oven broiled. 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 1-methyl-9H-pyrido[3,4-b]indole (harman) and 9H-pyrido[3,4-b]indole (norharman) were identified in several samples. Chicken cooked at low temperatures contained low amounts of HAs. In pan-fried chicken breasts, MeIQx was detected in amounts below 2 ng/g, 4,8-DiMeIQx below 0.6 ng/g, and PhIP in amounts up to 38 ng/g. Harman and norharman were detected in almost all samples (below 15 ng/g). In skin from a commercially barbecued chicken, MeIQx, 4,8-DiMeIQx and PhIP were detected, while only traces of MeIQx were detected in the meat. MeIQx was detected in a commercial chicken flavour, 0.1 ng/ml. No HAs were detected in pan-fried chicken liver. The results show that the content of HAs in chicken cooked in various ways is low if prepared at low temperatures, and increases with increasing cooking temperature. PhIP formation seems to start accelerating at cooking temperatures around or above 200 degrees C. Colour development increases with cooking temperature, but no correlation with HA content was observed.

Heterocyclic amines in process flavours, process flavour ingredients, bouillon concentrates and a pan residue.

Seven process flavours, five process flavour ingredients, four bouillon concentrates and a pan residue were analysed for mutagenic/carcinogenic heterocyclic amines. To improve chromatographic efficiency for samples with complex matrixes (process flavours, pan residues, etc.), a new additional purification method was designed. The following polar heterocyclic amines were detected: 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in one sample (3.4 ng/g), 2-amino-3-methylimidazo[4,5-f]quinoxaline (IQx) in two samples (0.7-2.0 ng/g), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in four samples (1.0-13.8 ng/g), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) in three samples (1.3-2.9 ng/g), 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx) in one sample (0.3 ng/g), and traces of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in two samples. 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) was not identified in any of the samples. The following non-polar heterocyclic amines were detected: 2-amino-9H-pyrido[2,3-b]indole (AalphaC) in one sample (0.4 ng/g), 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) in one sample (20.3 ng/g), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) in two samples (1.4-1.7 ng/g), and traces of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in two samples. Of the co-mutagenic heterocyclic amines, 1-methyl-9H-pyrido[3,4-b]indole (harman) was identified in 15 of 17 samples (3.3-755 ng/g), and 9H-pyrido[3,4-b]indole (norharman) in 16 of 17 samples (1.2-176 ng/g). The polar heterocyclic amines were detected only in the samples of animal and mixed animal plus vegetable origin, while the non-polar heterocyclic amines were identified in samples of animal, mixed animal plus vegetable and pure vegetable origin.

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.

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.

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%.