Arvid Fromberg

Analysis of chloro- and nitroanilines and -benzenes in soils by headspace solid-phase microextraction

Abstract Quantitative analysis by headspace solid-phase microextraction (HS-SPME) of twenty chloro- and nitrobenzenes and -anilines spiked into soil samples was possible when the calibration was performed with the same matrix. The SPME response increased with addition of water to the air dried soil samples, and by optimisation of extraction conditions such as temperature, extraction time and sample agitation. Distribution constants between the fibre coating materials and water were determined. They showed that polyacrylate, rather than polydimethylsiloxane, should be used in the analysis of polar compounds. Matrix effects, mainly depending on the organic carbon content of the soil, were so large that quantitative analyses of real soil samples would not be reliable with model matrix calibration. This problem would be overcome if a nearly exhaustive extraction could be achieved. Recovery studies showed that this was possible only in the case of extraction of the lightest non-polar analytes from a soil with a very low content of organic carbon. Instead quantification could be performed with calibration by standard addition. By this approach the non-linear calibration curves at concentrations near the detection limits would cause inaccurate results at trace level, whereas it could be applied successfully within the linear ranges. Hence, the potential of HS-SPME in soil analysis is primarily as a rapid screening technique.

Analysis of polycyclic aromatic hydrocarbons in vegetable oils combining gel permeation chromatography with solid-phase extraction clean-up.

A semi-automatic method for the determination of polycyclic aromatic hydrocarbons (PAHs) in edible oils using a combined gel permeation chromatography/solid-phase extraction (GPC/SPE) clean-up is presented. The method takes advantage of automatic injections using a Gilson ASPEC XL sample handling system equipped with a GPC column (S-X3) and pre-packed silica SPE columns for the subsequent clean-up and finally gas chromatography-mass spectrometry (GC-MS) determination. The method was validated for the determination of PAHs in vegetable oils and it can meet the criteria for the official control of benzo[a]pyrene levels in foods laid down by the Commission of the European Communities. A survey of 69 vegetable oils sampled from the Danish market included olive oil as well as other vegetable oils such as rapeseed oil, sunflower oil, grape seed oil and sesame oil. Levels of benzo[a]pyrene in all the oils were low (<0.2–0.8 µg kg−1), except for one sample of sunflower oil containing 11 µg kg−1 benzo[a]pyrene.

Furan occurrence in starchy food model systems processed at high temperatures: effect of ascorbic acid and heating conditions.

Furan, a potential carcinogen, has been detected in highly consumed starchy foods, such as bread and snacks; however, research on furan generation in these food matrixes has not been undertaken, thus far. The present study explored the effect of ascorbic acid addition and cooking methods (frying and baking) over furan occurrence and its relation with the non-enzymatic browning in a wheat flour starchy food model system. Results showed that furan generation significantly increased in the presence of ascorbic acid after 7 min of heating (p < 0.05). The strongest effect was observed for baked products. Additionally, the furan content in fried products increased with the increase of the oil uptake levels. As for Maillard reactions, in general, the furan level in all samples linearly correlated with their degree of non-enzymatic browning, represented by L* and a* color parameters (e.g., wheat flour baked samples showed a R(2) of 0.88 and 0.87 for L* and a*, respectively), when the sample moisture content decreased during heating.

Authenticity and Traceability of Vanilla Flavors by Analysis of Stable Isotopes of Carbon and Hydrogen

Authenticity and traceability of vanilla flavors were investigated using gas chromatography-isotope ratio mass spectrometry (GC-IRMS). Vanilla flavors produced by chemical synthesis (n = 2), fermentation (n = 1), and extracted from two different species of the vanilla orchid (n = 79) were analyzed. The authenticity of the flavor compound vanillin was evaluated on the basis of measurements of ratios of carbon stable isotopes (δ(13)C). It was found that results of δ(13)C for vanillin extracted from Vanilla planifolia and Vanilla tahitensis were significantly different (t test) and that it was possible to differentiate these two groups of natural vanillin from vanillin produced otherwise. Vanilla flavors were also analyzed for ratios of hydrogen stable isotopes (δ(2)H). A graphic representation of δ(13)C versus δ(2)H revealed that vanillin extracted from pods grown in adjacent geographic origins grouped together. Accordingly, values of δ(13)C and δ(2)H can be used for studies of authenticity and traceability of vanilla flavors.

Sublethal Concentrations of Antibiotics Cause Shift to Anaerobic Metabolism in Listeria monocytogenes and Induce Phenotypes Linked to Antibiotic Tolerance

The human pathogenic bacterium Listeria monocytogenes is exposed to antibiotics both during clinical treatment and in its saprophytic lifestyle. As one of the keys to successful treatment is continued antibiotic sensitivity, the purpose of this study was to determine if exposure to sublethal antibiotic concentrations would affect the bacterial physiology and induce antibiotic tolerance. Transcriptomic analyses demonstrated that each of the four antibiotics tested caused an antibiotic-specific gene expression pattern related to mode-of-action of the particular antibiotic. All four antibiotics caused the same changes in expression of several metabolic genes indicating a shift from aerobic to anaerobic metabolism and higher ethanol production. A mutant in the bifunctional acetaldehyde-CoA/alcohol dehydrogenase encoded by lmo1634 did not have altered antibiotic tolerance. However, a mutant in lmo1179 (eutE) encoding an aldehyde oxidoreductase where rerouting caused increased ethanol production was tolerant to three of four antibiotics tested. This shift in metabolism could be a survival strategy in response to antibiotics to avoid generation of ROS production from respiration by oxidation of NADH through ethanol production. The monocin locus encoding a cryptic prophage was induced by co-trimoxazole and repressed by ampicillin and gentamicin, and this correlated with an observed antibiotic-dependent biofilm formation. A monocin mutant (ΔlmaDCBA) had increased biofilm formation when exposed to increasing concentration of co-trimoxazole similar to the wild type, but was more tolerant to killing by co-trimoxazole and ampicillin. Thus, sublethal concentrations of antibiotics caused metabolic and physiological changes indicating that the organism is preparing to withstand lethal antibiotic concentrations.

Furan and Alkylated Furans in Heat Processed Food, Including Home Cooked Products

The occurrence of furan in home cooked food was studied. Cooking was found to reduce the level of furan in ready-to-eat foods, however on average around 50% of furan remain in the foods. The analysis of furan occurrence revealed that it is most commonly formed in foods with high levels of carbohydrates. Interestingly, breakfast cereals, dry bread products, and dried fruit products including raisins, plums and bananas contained furan at levels up to 387 µg/kg. Furan was also found in the dry ingredients of cookies and bread, and in snacks such as crisps and popcorn. The 2-alkylfurans, 2-methylfuran, 2,5-dimethyl furan, 2-ethylfuran, and 2-pentylfuran were present at levels in the same range as furan (885 µg/kg) and the level of 2-methylfuran (1328 µg/kg) exceeded this level in coffee.

Are Chileans exposed to dietary furan

Chilean consumer preferences include foods that may contain considerable amounts of furan, a potential human carcinogen. However, there is no information regarding dietary exposure to furan in Chile. Thus, the objective of this work was to determine the Chilean exposure to dietary furan. To accomplish this objective, the furan concentration of 14 types of commercial foods processed at high temperature were analysed based on a modified headspace-GC/MS (HS-GC/MS) method in which the limits of detection for different food matrices ranged from 0.01 to 0.6 ng g−1. In addition, a risk assessment was made with exposure estimates based on dietary data from national studies on different age groups (9-month-old babies, school children, adults and elderly people). Of the food items surveyed “American”-type coffee (espresso coffee plus hot water) obtained from automatic coffee machine (936 ng g−1) and low moisture starchy products like crisps and “soda”-type crackers showed the highest furan concentrations (259 and 91 ng g−1, respectively). Furthermore, furan was also found in samples of breakfast cereals (approximately 20 ng g−1), jarred fruit baby foods (8.5 ng g−1) and orange juice (7.0 ng g−1). School children (aged 9–13 years) represented the highest intake of furan (about 500 ng kg−1bw day−1), with margins of exposure of 2479 and 2411, respectively, which points to a possible public health risk.

Authenticity of raspberry flavor in food products using SPME‐chiral‐GC‐MS

Abstract A fast and simple method for authenticating raspberry flavors from food products was developed. The two enantiomers of the compound (E)‐α‐ionone from raspberry flavor were separated on a chiral gas chromatographic column. Based on the ratio of these two enantiomers, the naturalness of a raspberry flavor can be evaluated due to the fact that a natural flavor will consist almost exclusively of the R enantiomer, while a chemical synthesis of the same compound will result in a racemic mixture. Twenty‐seven food products containing raspberry flavors where investigated using SPME‐chiral‐GC‐MS. We found raspberry jam, dried raspberries, and sodas declared to contain natural aroma all contained almost only R‐(E)‐α‐ionone supporting the content of natural raspberry aroma. Six out of eight sweets tested did not indicate a content of natural aroma on the labeling which was in agreement with the almost equal distribution of the R and S isomer. Two products were labeled to contain natural raspberry flavors but were found to contain almost equal amounts of both enantiomers indicating a presence of synthetic raspberry flavors only. Additionally, two products that were labeled to contain both raspberry juice and flavor showed equal amounts of both enantiomers, indicating the presence of synthetic flavor.

Rebuttal to Comment on Authenticity and traceability of vanilla flavors by analysis of stable isotopes of carbon and hydrogen.

Flavors by Analysis of Stable Isotopes of Carbon and Hydrogen I Hansen et al., we have published data on δC values and δH values of vanillin extracted from 79 vanilla pods collected from many countries around the world and concluded that “The combined use of results of δC and δH analyses for vanillin, extracted from vanilla pods, shows a relatively close clustering pending upon species as well as geographical location of growth. Analysis of δ values of carbon and hydrogen by compound-specific IRMS is a useful tool in the verification of the authenticity and traceability of vanilla pods”. The goal of previous work by Greule et al. was development of an analytical method to identify vanilla extracted from pods versus vanilla produced synthetically or from a biotechnological process and reported the δC and δH values of both bulk and methoxyl group of vanillin extracted from five vanilla pods. Their δC values for bulk vanillin are very similar to our values for the two different species. The reported values for δH in bulk vanillin show very little variation and are in the range from −47 to −58‰, indicating close geographical origin. We acknowledge that analysis of δC and δH values of both bulk and methoxyl group of vanillin may provide additional information useful in authenticity and traceability studies. We were interested in the use of δ values of carbon and hydrogen measured on bulk vanilla for authenticity and traceability studies. The δ values for hydrogen differ around the world primarily as a result of logitudinal and continental effects, and the δ values for hydrogen can therefore differ between countries and even within a single country. Plants take up water from the surroundings, and the ratio of stable hydrogen isotopes in the plant constituents will resemble the ratio of their specific geographical location. Having only information regarding from which country a plant constituent originates, the δ values for hydrogen are expected to show some variation, and also overlap between countries can be expected. We have reported δ values for hydrogen in vanillin together with information on from which country the vanilla pods originate. Information on the specific origin of the vanilla pods was not available. However, information on the δ values for hydrogen is useful in traceability studies as, for example, vanillin with δ values outside the range of −68 to −60‰ is unlikely to originate from Indonesia. Screening of samples against reference datasest enables the possibility to exclude origin possibilities in the verification of label claims. Therefore, we are convinced that our data and results support our discussion and conclusions. Anne-Mette S. Hansen Arvid Fromberg Henrik L. Frandsen* Division of Food Chemistry, National Food Institute, Technical University of Denmark, Mørkhøj bygade 19, DK-2860 Søborg, Denmark ■ AUTHOR INFORMATION Notes The authors declare no competing financial interest.