Ethyl carbamate levels in selected fermented foods and beverages

Ethyl carbamate (EC), also known as urethane, is an animal carcinogen and a by-product of fermentation. Because EC has been found in distilled spirits and wines, a variety of fermented foods and beverages were analyzed to assess its occurrence in other products. Previously described methods using a gas chromatograph-thermal energy analyzer with a nitrogen converter were modified for each matrix and gave recoveries of greater than 80%, with a limit of detection in the 1-2 micrograms/kg (ppb) range. A total of 152 test samples were analyzed; EC levels ranged from none found to 3 ppb in 15 cheeses, 6 teas, 12 yogurts, and 8 ciders; from none found to 13 ppb in 30 breads and 69 malt beverages; and from none found to 84 ppb in 12 soy sauces. Gas chromatography/mass spectrometry/mass spectrometry was used to confirm EC identity and to quantitate EC in selected food extracts.     

Acid inputs from the atmosphere in the United Kingdom

Abstract. Inputs of acidity to the ground arise through two distinct routes: wet deposition which includes all acidity deposited in rain and snow and dry deposition, the direct sorption of SO₂, NO₂ or HNO₃ gases by vegetation or soil surfaces. The acidity from dry deposition of SO₂ and NO₂ is created during the oxidation of deposited SO₂ and NO₂ to SO²₄ and NO₃⁻ respectively. The areas of Britain experiencing the largest wet deposition of acidity are the high rainfall areas of the west and north, in particular the west central highlands of Scotland, Galloway and Cumbria where inputs exceed 1 kp H⁺ ha⁻¹ annually. Wet deposited acidity in the east coast regions of Britain is in the range 0.3–0.6 kg H⁺ ha⁻¹ a⁻¹. Monitoring data for rainfall acidity at rural sites throughout northern Britain show a decline in deposited acidity of about 50% during the last six years. Dry deposition is largest in the industrial midlands and southeast England and in the central lowlands of Scotland, where concentrations of SO₂ are largest. In these regions the dry deposition of SO₂ following oxidation may lead to acid inputs approaching 3 kg H⁺ ha⁻¹ a⁻¹ and greatly exceeding wet deposition.     

Chemical conversion of alpha-keto acids in relation to flavor formation in fermented foods

Formation of flavor compounds from branched-chain alpha-keto acids in fermented foods such as cheese is believed to be mainly an enzymatic process, while the conversion of phenyl pyruvic acid, which is derived from phenylalanine, also proceeds chemically. In this research, the chemical conversion of alpha-keto acids to aldehydes with strong flavor characteristics was studied, with the main focus on the conversion of alpha-ketoisocaproic acid to the aldehyde 2-methylpropanal, and a manganese-catalyzed reaction mechanism is proposed for this conversion. The mechanism involves keto-enol tautomerism, enabling molecular oxygen to react with the beta-carbon atom of the alpha-keto acid, resulting in a peroxide. This peroxide can react in several ways, leading to unstable dioxylactone or noncyclic intermediates. These intermediates will break down into an aldehyde and oxalate or carbon oxides (CO and CO(2)). All the alpha-keto acids tested were converted at pH 5.5 and in the presence of manganese, although their conversion rates were rather diverse. This chemical reaction might provide new ways for controlling cheese flavor formation with the aim of acceleration of the ripening process or diversification of the flavor characteristics.     

Trends in wet and dry deposition of sulphur in the United Kingdom

UK data on sulphur deposition trends between the 1960's and 1990's are presented. Long term data sets of sulphur dioxide (SO₂) concentrations at two sites have been analysed and dry deposition determined using a resistance model. Wet deposition has been calculated from non-marine sulphate concentration and rainfall fields for 1978–80 and 1989–93. These maps have been interpolated and corrected for seeder feeder enhancement. The wet deposition of sulphur declined by about 43 % between 1979 and 1993 whereas emissions of sulphur declined by about 32 %. An indication of the trends in sulphur dry deposition is provided by data from Eskdalemuir, a site in southern Scotland where wet deposition and SO₂ concentration have been measured since 1979. Dry deposition at Eskdalemuir has decreased by 70 % and wet deposition by 48 %. Hence, while wet deposition has responded approximately linearly with the decline in UK emissions of sulphur dioxide, dry deposition has declined at twice the rate of decline in UK emissions.     

Orographic enhancement of wet deposition in the United Kingdom: Continuous monitoring

Continuous monitoring of cloud and rain samples at three mountain sites in the UK has allowed consideration of the long term impact of the enhancement of the wet deposition of pollutants by orographie effects, specifically the scavenging of cap cloud droplets by rain falling from above (the seeder-feeder effects). The concentration of the major pollutant ions in the cloud water is related to the relative proximity of each site to marine and anthropogenic sources of aerosol. In general, the concentrations of major ions in precipitation at summit sites exceed those in precipitation to low ground nearby by 20% to 50%. Concentrations in orographie cloud exceed those in upwind rain by between a factor of five and ten. The results are consistent with seeder-feeder scavenging of hill cloud by falling precipitation in which the average concentration of ions in scavenged hill cloud exceed those in precipitation upwind by a factor of 1.7 to 2.3 for sulphate and nitrate respectively at Dunslair Heights and 1.5 to 1.8 for sulphate and nitrate at Holme Moss. The results suggest that the parameterisation of this relationship with scavenged feeder cloud water concentrations assumed to exceed those in seeder rain by a factor of two for the production of predictive maps of wet deposition in mountainous regions of the U.K. is satisfactory.     

Analysis of ethyl carbamate in wines using solid-phase extraction and multidimensional gas chromatography/mass spectrometry

The method describes a rapid and accurate procedure for the analysis of ethyl carbamate in wines. The separation of the ethyl carbamate (EC), the target analyte, from alcohol and the sample matrix is a challenge to many analytical chemists. After alcohol removal from the sample, EC was extracted and concentrated by solid-phase extraction. For analysis of EC, large-volume injection on a programmable temperature vaporization (PTV) inlet was used followed by multidimensional gas chromatography/mass spectrometry (MDGC/MS) using electron-impact ionization (EI). For quantitation, the ratio of ions produced during EI at m/z 62 (EC) and 64 (isotopically labeled EC) was monitored. The use of solid-phase extraction and MDGC/MS removes the majority of the matrix interference encountered in other methods. A linear dynamic range was established from 0.387 to 1160 ng/mL, with a limit of detection at 0.1 ng/mL and limit of quantitation at 1 ng/mL.     

Lipophilic and hydrophilic antioxidant capacities of common foods in the United States

Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORAC(FL)) assay with fluorescein as the fluorescent probe and 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin-Ciocalteu reagent. Hydrophilic ORAC(FL) values (H-ORAC(FL)) ranged from 0.87 to 2641 micromol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORAC(FL) values (L-ORAC(FL)) ranged from 0.07 to 1611 micromol of TE/g. Generally, L-ORAC(FL) values were <10% of the H-ORAC(FL) values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORAC(FL) and H-ORAC(FL). Differences of ORAC(FL) values in fruits and vegetables from different seasons and regions were relatively large for some foods but could not be analyzed in detail because of the sampling scheme. Two different processing methods, cooking and peeling, were used on selected foods to evaluate the impact of processing on ORAC(FL). The data demonstrated that processing can have significant effects on ORAC(FL). Considering all of the foods analyzed, the relationship between TP and H-ORAC(FL) showed a very weak correlation. Total hydrophilic and lipophilic antioxidant capacity intakes were calculated to be 5558 and 166 micromol of TE/day, respectively, on the basis of data from the USDA Continuing Survey of Food Intakes by Individuals (1994-1996).     

Rapid gas chromatographic method for determining ethyl carbamate in alcoholic beverages with thermal energy analyzer detection

A rapid column elution method has been developed for the determination of ethyl carbamate (EC) in alcoholic beverages. The beverage is mixed with Celite and packed in a column containing deactivated alumina capped with a layer of sodium sulfate. EC is then eluted with methylene chloride. The method, using a gas chromatograph-thermal energy analyzer with a nitrogen converter for detection and quantitation of EC, has been applied to a variety of alcoholic beverages. Recoveries +/- standard deviations of EC in wine and whisky fortified at the 20 and 133 micrograms/kg (ppb) levels averaged 87.3 +/- 5.3 and 88.7 +/- 3.6%, respectively. The method has a limit of detection of 1.5 ppb. Gas chromatography/mass spectrometry/mass spectrometry was used to confirm the identity and quantitation of EC in selected beverage extracts.     

Survey of infant foods for Clostridium botulinum spores

A total of 236 samples of infant foods, including honey, dry cereal, nonfat dry milk, evaporated milk, canned formula, and canned baby food, were collected in the New York City area and tested for the presence of Clostridium botulinum spores. Methods for recovery of spores were validated using foods spiked with 4 spores/mL or g. None of the products contained C. botulinum spores, indicating that their incidence in these commercial foods is not widespread. This limited study did not identify any food types that could be suspected of being involved in the transmission of infant botulism.     

Copper(II) catalysis in cyanide conversion into ethyl carbamate in spirits and relevant reactions.

The role of copper(II) species in the oxidation of inorganic cyanide to cyanate and in the conversion of cyanate or urea into ethyl carbamate was investigated. The oxidation process has been shown to be independent from the dissolved oxygen. Elemental analysis and infrared spectroscopy have shown the formation of a mixed copper carbonate/hydroxide in the process of oxidation of cyanide to cyanate in water/ethanol. The complexation to Cu(II) of cyanate formed upon cyanide oxidation makes the former more susceptible to nucleophilic attack from ethanol, with conversion into ethyl carbamate. Comparatively, urea has a minor role with respect to cyanide in the formation of ethyl carbamate. Therefore, the urea present in some samples of Brazilian sugar cane spirit (cacha?a) has been shown to have almost no influence on the ethyl carbamate content of cacha?as, which comes essentially from cyanide. Fe(II,III) affords results similar to those found with Cu(II). Some suggestions are presented to avoid ethyl carbamate formation in spirits during distillation.     

A soil carbon and land use database for the United Kingdom

Abstract. The compilation of a database of soil carbon and land use is described, from which models of soil carbon dioxide emissions across the United Kingdom (UK) can be run. The database gives soil organic carbon, sand, silt and clay contents and bulk densities weighted to reference layers from 0 to 30 cm and from 30 to 100 cm depths. The data are interpolated from information on soil types and land use on a 1 km grid across the UK and are used to estimate soil carbon stocks. For 1990, the baseline year for the Kyoto Protocol on carbon emissions, the estimate is 4562 Tg soil organic carbon in the top 1 m of soil across the UK, with an average density of 18 kg m⁻². The data can be reported by layer (e.g. 54% in topsoils) and country (e.g. 48% in Scotland) as well as by soil and land type.     

Determination of ethyl carbamate in distilled alcoholic beverages by gas chromatography with flame ionization or mass spectrometric detection

Quantitative methods are detailed for determination of ethyl carbamate in distilled alcoholic beverages by capillary gas chromatography with flame ionization detection (GC/FID) and by packed-column gas chromatography/mass spectrometry (GC/MS) using selected ion monitoring. Five g samples of distillate of known ethanol concentration are diluted with water to 25% ethanol (v/v), washed with petroleum ether, and extracted with dichloromethane prior to GC/FID or GC/MS analysis. As necessary, sample extracts that exhibit GC/FID interference are passed through alumina for additional cleanup. When internal standards (tert-butyl carbamate and n-butyl carbamate for GC/FID, or ethyl 13C-15N-carbamate for GC/MS) were used for quantitation, the limit of detection for ethyl carbamate was in the range of 5-25 ppb. Coefficients of variation ranged from 3.5 to 6.0% for GC/FID determinations, and from 1.4 to 3.2% for GC/MS. Correlation between methods for 22 random distillate samples ranging in concentration from approximately 40 to 800 ppb gave a correlation coefficient (r) of 0.996.     

Orographic enhancement of wet deposition in the United Kingdom: case studies and modelling

Two field experiments to observe the detailed response of wet deposition to orography in a polluted environment are reported. Rain events were classed as frontal, convective or mixed on the basis of meteorological data. Analysis of the deposition enhancement and cap cloud composition confirmed that for the frontal events the seeder-feeder effect (scavenging of cap cloud by rain drops) dominates. The greater concentration of ions in the water scavenged from the cap cloud than in the rain means that deposition is enhanced for all ions. For marine ions the scavenged water was found to be between five and six times as concentrated as the rain and for anthropogenically produced ions it was about twice as concentrated.A computational model of rainfall incorporating the seeder-feeder effect has been broadly successful in predicting enhancement although some details of the observed pattern remain to be explained.     

Concentrations of anthocyanins in common foods in the United States and estimation of normal consumption

Anthocyanins (ACNs) are water-soluble plant pigments that have important functions in plant physiology as well as possible health effects. Over 100 common foods were screened for ACNs, and 24 of them were found to contain ACNs. Concentrations of total ACNs varied considerably from 0.7 to 1480 mg/100 g of fresh weight in gooseberry ('Careless' variety) and chokeberry, respectively. Not only does the concentration vary, but the specific anthocyanins present in foods are also quite different. Only six common aglycones, delphinidin, cyanidin, petunidin, pelargonidin, peonidin, and malvidin, were found in all of these foods. However, their sugar moieties and acylation patterns varied from food to food. Results from this study will add to the available data for the USDA Nutrient Database of flavonoids. On the basis of the concentration data and updated food intake data from NHANES 2001-2002, the daily intake of ACNs is estimated to be 12.5 mg/day/person in the United States. Of the different aglycones, cyanidin, delphinidin, and malvidin were estimated to contribute 45, 21, and 15%, respectively, of the total ACN intake. Nonacylated contributed 77% compared to 23% from acylated ACNs.     

Radionuclides in domestic and imported foods in the United States, 1983-1986

Findings in the Food and Drug Administration's Radionuclides in Foods program are summarized for samples collected between October 1, 1982, and September 30, 1986. All radionuclide findings for Total Diet and reactor samples were either in Action Range I or low in Range II of the surveillance and control recommendations given by the Federal Radiation Council. The only long-range trend noted was a continuation of the general decline in dietary intake of 90Sr since 1961. Imported food samples were analyzed for contamination after the Chernobyl nuclear accident. The findings for imported foods indicate that the surveillance efforts successfully targeted contaminated foods, and that contamination levels were below levels of concern for all but one oregano and 3 cheese samples.     

Volatile N-nitrosamines in infant pacifiers sold in the United States as determined by gas chromatography/thermal energy analysis

Volatile N-nitrosamines in infant latex rubber pacifiers were determined using a modification of a previously described dichloromethane extraction procedure, followed by gas chromatography/thermal energy analysis. Under an interagency agreement between the National Center for Toxicological Research and the Consumer Product Safety Commission (CPSC), data were obtained on the baseline and compliance concentrations of volatile N-nitrosamines in infant pacifiers sold in the United States. Pacifiers made by 18 different manufacturers before and after the January 1, 1984 action level of 60 ppb was set by the CPSC were analyzed for volatile N-nitrosamines. N-Nitrosodibutylamine was the principal N-nitrosamine found, along with trace amounts of N-nitrosodimethylamine, N-nitrosodiethylamine, and N-nitrosopiperidine. Mean total volatile N-nitrosamine levels for baseline and compliance samples were 63.9 and 21.2 ppb, respectively. The pacifier lots sampled after January 1, 1984 showed a significant decrease in contamination levels, indicating that at least 98% of the market share is in compliance with the CPSC enforcement policy for N-nitrosamines in infant pacifiers sold in the United States.