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Effect of some cooked food mutagens on unscheduled DNA synthesis in cultured precision-cut rat, mouse and human liver slices.

Precision-cut liver slices were prepared from male Fischer 344 rats, female CDF1 mice and humans (both male and female subjects). Liver slices were cultured for 24 hr in medium containing [3H]thymidine and either PhIP, IQ, MeIQ, MeIQx, Glu-P-1 or Trp-P-1, and then processed for auto-radiographic evaluation of unscheduled DNA synthesis (UDS). All six cooked food mutagens examined produced concentration-dependent increases in UDS in human liver slices. PhIP was the most potent compound examined, followed by MeIQx, IQ and then MeIQ, Glu-P-1 and Trp-P-1. Significant increases in UDS were observed with PhIP, IQ and MeIQx at concentrations as low as 5 microM in the culture medium. The same rank order of potency was not apparent in either rat or mouse liver slices. In rat liver slices only MeIQ significantly induced UDS, although positive results were obtained with two other genotoxins, namely 2-acetylaminofluorene and aflatoxin B1. Apart from MeIQx, all the cooked food mutagens produced significant increases in UDS in mouse liver slices. This study demonstrates the usefulness of precision-cut liver slices to evaluate species differences in xenobiotic-induced genotoxicity. Both marked compound and species differences in induction of UDS were observed. The data provide further evidence that dietary cooked food mutagens are potential human carcinogens.

2-Acetylaminofluorene↗

The effect of two methods of cooking and cooling on Clostridium welchii and other bacteria in meat.

A comparison was made of beef cooked in conventional and moist air (Rapidaire) ovens. In both large (ca. 4.5 kg.) and small (ca. 2.7 kg.) joints, spores of Clostridium welchii survived after cooking but vegetative cells, Escherichia coli, and Staphylococcus aureus, did not, regardless of the type of oven used.Cooling at room temperature after cooking permitted growth of Cl. welchii. Although some multiplication also occurred in the centre of large roasts cooled under refrigeration, the viable counts were considered too low to constitute a potential health risk.

Animals↗

Observations on procedures for thawing and spit-roasting frozen dressed chickens, and post-cooking care and storage: with particular reference to food-poisoning bacteria.

A comparison was made of four methods of thawing frozen chickens and an average thaw time for each method was determined.Fully and partially thawed chickens, inoculated with salmonellas, Clostridium welchii and Staphylococcus aureus were cooked in a spit-roasting oven at different temperatures for different lengths of time. The chickens were examined freshly cooked and after storage under various conditions.Spit roasting fully thawed chickens until the outer skin was golden brown was sufficient heat-treatment to kill salmonellas and Staph. aureus but Cl. welchii could survive. Salmonellas could also survive if the chickens were not fully thawed before cooking.Incorrect storage after cooking was shown to encourage the growth of pathogens.The incidence of intestinal pathogens in frozen dressed chickens and environmental hazards in spit-roasting establishments were also studied. Of raw chickens examined 35% contained salmonellas (9 serotypes), 63% contained Cl. welchii and 63% Staph. aureus.

Animals↗

Effect of nixtamalization (Alkaline cooking) on fumonisin-contaminated corn for production of masa and tortillas.

Studies were undertaken to determine the fate of the mycotoxins, fumonisins, during the process of alkaline cooking (nixtamalization), using normal-appearing corn that was naturally contaminated with fumonisin B(1) (FB(1)) at 8.79 ppm. Corn was processed into tortillas, starting with raw corn that was cooked with lime and allowed to steep overnight; the steeped corn (nixtamal) was washed and ground into masa, which was used to make tortillas. Calculations to determine how much of the original fumonisin remained in the finished products took into consideration that FB(1) will be converted to hydrolyzed fumonisin B(1) (HFB(1)) by the process of alkaline cooking. All fractions, including steeping and washing water, were weighed, and percent moisture and fumonisin content were determined. Tortillas contained approximately 0.50 ppm of FB(1), plus 0.36 ppm of HFB(1), which represented 18.5% of the initial FB(1) concentration. Three-fourths of the original amount of fumonisin was present in the liquid fractions, primarily as HFB(1). Nixtamalization significantly reduced the amount of fumonisin in maize.

Carboxylic Acids↗

Effect of cooking temperatures on chemical changes in species of organic arsenic in seafood.

The concentrations of arsenobetaine (AB), tetramethylarsonium ion (TMA(+)), and trimethylarsine oxide (TMAO) were determined in samples of sole, dory, hake, and sardine, raw and after being subjected to cooking processes--baking, frying, and grilling--at various temperatures. In all cases, the temperature attained inside the product during the cooking process was measured. The arsenic species extracted from the samples with methanol/water were separated by means of a column switching technique between a PRP-X100 column and a PRP-X200 column. AB was detected by hydride generation atomic absorption spectrometry, whereas TMA(+) and TMAO were detected by hydride generation atomic fluorescence spectrometry. The results obtained showed that, in all of the types of seafood studied, TMA(+) appeared after cooking, possibly because heating facilitates decarboxylation of AB to TMA(+).

Animals↗

Aroma components of cooked tail meat of American lobster (Homarus americanus).

Key aroma components of cooked tail meat of American lobster (Homarus americanus) were studied by gas chromatography-olfactometry (GCO) techniques. Components of low and intermediate volatility were evaluated by aroma extract dilution analysis of solvent extracts prepared by direct solvent extraction-high vacuum distillation and vacuum steam distillation-solvent extraction, whereas headspace volatile components were assessed by GCO of decreasing headspace (static and dynamic modes) samples. Forty-seven odorants were detected by all techniques. 3-Methylbutanal (chocolate, malty), 2,3-butanedione (buttery), 3-(methylthio)propanal (cooked potato), 1-octen-3-one (mushroom), 2-acetyl-1-pyrroline (popcorn), and (E,Z)-2,6-nonadienal (cucumber), were identified as predominant odorants by all four isolation methods. The highly volatile compounds methanethiol (rotten, sulfurous) and dimethyl sulfide (canned corn) were detected by headspace methods only. These eight odorants along with three unknown compounds with crabby, amine, fishy odors were found to predominate in the overall aroma of cooked lobster tail meat.

Animals↗

Nutritional and sensory evaluation of akara made from blends of cowpea and hard-to-cook mottled brown dry beans.

The effect of replacing cowpea with hard-to-cook beans on the nutritional and sensory properties of akara were evaluated. Cowpea (Vigna unguiculata), traditionally used for making akara, was substituted 0%, 25%, 50%, 75%, and 100% with hard-to-cook (HTC) mottled brown beans (Phaseolus vulgaris). Cowpea (CP) soaked for 60 min HTC beans soaked for 18 h were separately decorticated, ground to a paste, and mixed in the following CP:MBB ratios: 0:100, 25:75, 50:50, 75:25, and 100:0. The paste mixtures were each whipped and fried into akara. The samples were analyzed for bulk density, nutritional composition, carbohydrate and protein digestibility, alpha-amylase inhibitor and trypsin inhibitor activity, and sensory attributes. The bulk density of paste as well as of akara increased with the increasing content of HTC bean. Akara made from composite paste had a relatively better amino acid profile. Frying beyond 5 min destroyed the alpha-amylase inhibitors as well as the trypsin inhibitor activity. No significant difference was observed in the overall acceptability of akara made from cowpea substituted up to 50% with HTC beans. Hence, this approach permits the utilization of hard-to-cook beans.

Amino Acids↗

Identification of fish species after cooking by SDS-PAGE and urea IEF: a collaborative study.

A collaborative study, to validate the use of SDS-PAGE and urea IEF, for the identification of fish species after cooking has been performed by nine laboratories. By following optimized standard operation procedures, 10 commercially important species (Atlantic salmon, sea trout, rainbow trout, turbot, Alaska pollock, pollack, pink salmon, Arctic char, chum salmon, and New Zealand hake) had to be identified by comparison with 22 reference samples. Some differences in the recoveries of proteins from cooked fish flesh were noted between the urea and the SDS extraction procedures used. Generally, the urea extraction procedure appears to be less efficient than the SDS extraction for protein solubilization. Except for some species belonging to the Salmonidae family (Salmo, Oncorhynchus), both of the analytical techniques tested (urea IEF, SDS-PAGE) enabled identification of the species of the samples to be established. With urea IEF, two laboratories could not differentiate Salmo salar from Salmo trutta. The same difficulties were noted for differentiation between Oncorhynchus gorbuscha and Oncorhynchus keta samples. With SDS-PAGE, three laboratories had some difficulties in identifying the S. trutta samples. However, in the contrast with the previous technique, SDS-PAGE allows the characterization of most of the Oncorhynchus species tested. Only Oncorhynchus mykiss was not clearly recognized by one laboratory. Therefore, SDS-PAGE (Excel gel homogeneous 15%) appears to be better for the identification, after cooking, of fish such as the tuna and salmon species which are characterized by neutral and basic protein bands, and urea IEF (CleanGel) is better for the gadoid species, which are characterized by acid protein bands (parvalbumins). Nevertheless, in contentious cases it is preferable to use both analytical methods.

Animals↗

Effect of cooking on cowpea protein fractions.

Nine cowpea cultivars obtained from Wad Medani Research Station were used in this study. The variation in protein fraction was: albumins 4.0-12.0, globulins 65.6-79.7, prolamins 1.4-2.2, G1-glutelins 0.9-3.0, G2-glutelins 1.4-2.9, G3-glutenins 9.1-14.0 and insoluble protein 0.5-3.0%. Two cowpea cultivars, H8-14 and CB-46, selected for their high albumin content, were cooked in 150 ml of boiling distilled water under reflux for 45 minutes. The protein fractions in the cooked seeds were determined. Results indicated that albumin and globulin fractions decreased significantly (p < or = 0.05) for both cultivars after cooking. This decrease was accompanied by a significant increase in G3-glutelin fractions.

Analysis of Variance↗

Animal food intake and cooking methods in relation to endometrial cancer risk in Shanghai.

We evaluated animal food intake and cooking methods in relation to endometrial cancer risk in a population-based case-control study in Shanghai, China. A validated food frequency questionnaire was used to collect the usual dietary habits of 1204 cases and 1212 controls aged 30-69 years between 1997 and 2003. Statistical analyses were based on an unconditional logistic regression model adjusting for potential confounders. High intake of meat and fish was associated with an increased risk of endometrial cancer, with adjusted odds ratios for the highest vs the lowest quartile groups being 1.7 (95% confidence interval: 1.3-2.2) and 2.4 (1.8-3.1), respectively. The elevated risk was observed for all types of meat and fish intake. Intake of eggs and milk was not related to risk. Cooking methods and doneness levels for meat and fish were not associated with risk, nor did they modify the association with meat and fish consumption. Our study suggests that animal food consumption may play an important role in the aetiology of endometrial cancer, but cooking methods have minimal influence on risk among Chinese women.

Adult↗

The potential use of lithium as a marker for the assessment of the sources of dietary salt: cooking studies and physiological experiments in men.

Lithium was investigated for its possible use as a marker for identifying the various sources of NaCl in the diet. Micromolar concentrations of lithium can be detected in various vegetables, tap water and also in urine specimens of adult volunteers. The lithium content of vegetables varied from 6.1 to 24.5 mumol of lithium/kg dry weight, with the exception of spinach and aubergines which had much higher concentrations. The excretion of the element in 24 h urine specimens ranged from 2 to 4 mumol of lithium/day. Experiments were performed to assess whether both lithium and sodium would penetrate foods at the same rate during cooking. The rates of penetration into food for both elements were proportional to their concentration in the cooking water despite a sodium/lithium ratio of 50:1. Physiological experiments were conducted to investigate the handling of small doses of lithium by the body. A dose of 250 mumol of lithium was chosen as optimal and given orally to healthy volunteers in either single or continuous aqueous doses of lithium carbonate. The recoveries of oral lithium in urine were 92 +/- 5% (SD) and 97 +/- 4 (SD) (n = 5) for single and continuous doses respectively. The daily addition of 100 mmol of oral NaCl to the diet of volunteers receiving a standard dose of lithium did not affect urinary lithium excretion rates nor the final recovery of the administered lithium. These studies suggest that lithium carbonate may be a useful marker for the uptake of NaCl into cooked food; after eating lithium-enriched food the monitoring of urinary lithium output may then be used to quantify the amount of sodium derived from the specific foods.

Cooking↗

Changes in the mineral composition of food as a result of cooking in "hard" and "soft" waters.

During the last decade many epidemiologists have found an inverse relationship between water hardness and cardiovascular mortality. It seems unlikely that this relationship can only be attributed to a deficiency of calcium and mangnesium in drinking water, because only 10-20% of the total daily intake of calcium and magnesium is derived from drinking water. The purpose of this study was to investigate changes in the mineral composition of food to investigate changes in the mineral composition of food when cooking with waters of different hardness. The most significant differences were found for calcium; the concentration of this element in potatoes and vegetables usually increased when cooking with hard-water types, while a decrease was noted when soft water was used for cooking.

Calcium↗

The effect of cooking on veterinary drug residues in food: 1. Clenbuterol.

The heat stability of clenbuterol was investigated. The drug was shown to be stable in boiling water at 100 degrees C. In cooking oil at 260 degrees C, losses were observed, indicating a half-life of about 5 min. The effect of a range of cooking processes (boiling, roasting, frying, microwaving) on clenbuterol residues in fortified and incurred tissue was studied. No net change in the amount of clenbuterol was observed in any of the cooking processes investigated except for deep frying using extreme conditions. There was little observed migration from the tissue into the surrounding liquid or meat juices. Clenbuterol residues were found not to be evenly distributed in the incurred raw tissue used for the investigation. The findings of this investigation show that data obtained from measurements on raw tissue are applicable for use in consumer exposure estimates and dietary intake calculations.

Animals↗

A study on degradation kinetics of ascorbic acid in amla (Phyllanthus emblica L.) during cooking.

The kinetics of ascorbic acid degradation in amla (Phyllanthus emblica L.) as well as in pure ascorbic acid solutions at initial concentrations present in amla over a temperature range of 50-120 degrees C (steady-state temperature) has been studied. The ascorbic acid degradation followed first-order reaction kinetics where the rate constant increased with an increase in temperature. The temperature dependence of degradation was adequately modeled by the Arrhenius equation. The activation energies were found to be 4.09 kcal/mole for amla and 4.49 kcal/mole for pure vitamin solution. The degradation kinetics of ascorbic acid was also evaluated in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient EcoCooker (unsteady state heating process). A mathematical model was developed using the steady-state kinetic parameters obtained to predict the losses of ascorbic acid from the time-temperature data of the unsteady state heating processing method. The results obtained indicate the ascorbic acid degradation is of a similar order of magnitude in all the methods of cooking.

Ascorbic Acid↗

Degradation kinetics of folic acid in cowpea (Vigna catjang L.) during cooking.

Kinetics of folic acid degradation in cowpea (Vigna catjang L.) as well as in pure folic acid solutions at initial concentrations present in cowpea over a temperature range of 50-120 degrees C (isothermal conditions) followed first order reaction kinetics, where the rate constant increased with an increase in temperature. The temperature dependence of degradation was adequately modeled by Arrhenius equation. The degradation was also evaluated in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient Eco Cooker (non-isothermal heating process). A mathematical model was developed using the isothermal kinetic parameters obtained to predict the losses of folic acid from the time-temperature data of the non-isothermal heat processing method. The results obtained indicate the folic acid degradation is of a similar order of magnitude in all the methods of cooking.

Cooking↗

Aluminium in antacids and cooking pots and the risk of hip fractures in elderly people.

The relationship between hip fractures and aluminium in antacids and cooking pots was examined in an epidemiological study in Sydney, Australia. A population-based case-control study was conducted and 416 men and women aged 65 years and over were recruited (209 cases and 207 controls). There was a significantly (p < 0.05) increased risk of hip fracture associated with use of aluminium cooking pots at age 20 years: the age- and sex-adjusted odds ratio was 1.9 [95% confidence interval (CI) 1.1-3.2]. No association was detected between risk of hip fracture and current use of aluminium cooking pots or use at age 50. There was some suggestion that long-term use of aluminium-containing antacids might increase the risk of hip fracture: the adjusted odds ratio comparing those who had used aluminium-containing antacids for more than 10 years with those who had never used them was 1.8 (95% CI 0.8-4.1). The findings of this study support the need for further research on the association between oral ingestion of aluminium and risk of hip fracture.

Aged↗

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↗

Trp-P-2 is not detectable in cooked meat and fish.

A gas chromatographic-mass spectrometric assay has been developed for the measurement of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in cooked meat and fish. The method employs capillary column gas chromatography, electron capture negative ion chemical ionisation mass spectrometry, a deuterated analogue of Trp-P-2 as internal standard and has a limit of detection of 0.1 ng Trp-P-2/g food. Four different meats and three types of fish, cooked either by frying on an electric hotplate or by charcoal broiling, were analysed for Trp-P-2. No Trp-P-2 was detected in any of the samples. The assay was modified to give an improved limit of detection of 25 pg Trp-P-2/g food and fried ground beef was re-examined. Once again, no Trp-P-2 was detected in this cooked meat.

Animals↗