Use Of Gas Chromatography Research Articles

A critical evaluation of the use of gas chromatography- and high performance liquid chromatography-mass spectrometry techniques for the analysis of microbial metabolites in human urine after consumption of orange juice

The present study compared and validated two analytical methods, HPLC-HRMS, and GC–MS using MSTFA as derivatization agent, for the analysis of microbiota-derived phenolic acids and aromatic compounds accumulating in urine, collected over a 24 h period after the consumption of 500 mL of orange juice. In addition, purification procedures using SDB-L and HLB solid phase cartridges were compared when HPLC-HRMS technique was used. Both HPLC-HRMS and GC–MS methodologies were successfully validated in terms of specificity, sensitivity, limit of detection and quantification, recovery and matrix effects. HPLC-HRMS, unlike GC–MS, does not require sample derivatization prior to analysis. GC–MS was not suitable for the analysis of phenolic sulfate and glucuronide metabolites because of their lack of volatility. These phase II metabolites could, however, be analysed by HPLC-HRMS which, as a consequence, provided more detailed and complete information on the phenolic compounds derived from microbiota-mediated degradation of orange juice (poly)phenols. Furthermore, the use of SDB-L and HLB cartridges for sample purification prior to HPLC-HRMS analysis is suitable for free phenolics and glucuronide metabolites but not sulfate derivatives. These findings highlight that the use of an inappropriate analytical protocol can adversely affect studies on the bioavailability of dietary (poly)phenols in which microbiota-derived phenolic catabolites play an important role.

GCalignR: An R package for aligning gas-chromatography data for ecological and evolutionary studies.

Chemical cues are arguably the most fundamental means of animal communication and play an important role in mate choice and kin recognition. Consequently, there is growing interest in the use of gas chromatography (GC) to investigate the chemical basis of eco-evolutionary interactions. Both GC-MS (mass spectrometry) and FID (flame ionization detection) are commonly used to characterise the chemical composition of biological samples such as skin swabs. The resulting chromatograms comprise peaks that are separated according to their retention times and which represent different substances. Across chromatograms of different samples, homologous substances are expected to elute at similar retention times. However, random and often unavoidable experimental variation introduces noise, making the alignment of homologous peaks challenging, particularly with GC-FID data where mass spectral data are lacking. Here we present GCalignR, a user-friendly R package for aligning GC-FID data based on retention times. The package was developed specifically for ecological and evolutionary studies that seek to investigate similarity patterns across multiple and often highly variable biological samples, for example representing different sexes, age classes or reproductive stages. The package also implements dynamic visualisations to facilitate inspection and fine-tuning of the resulting alignments and can be integrated within a broader workflow in R to facilitate downstream multivariate analyses. We demonstrate an example workflow using empirical data from Antarctic fur seals and explore the impact of user-defined parameter values by calculating alignment error rates for multiple datasets. The resulting alignments had low error rates for most of the explored parameter space and we could also show that GCalignR performed equally well or better than other available software. We hope that GCalignR will help to simplify the processing of chemical datasets and improve the standardization and reproducibility of chemical analyses in studies of animal chemical communication and related fields.

Barrow Culture Textiles and Mats in the Middle Dniester Area

AbstractThe article describes an attempt to identify the raw material of the organic layers - mats identified within the roofs and floors of the graves in the Yampil Barrow Cemetery Complex. The use of gas chromatography and infrared spectroscopy combined with microscopic analysis of the extracted “mat” sections significantly supplements our knowledge in the field of weaving of the studied communities.

A regulatory insertion-deletion polymorphism in the FADS gene cluster influences PUFA and lipid profiles among Chinese adults: a population-based study

Arachidonic acid (AA) is the major polyunsaturated fatty acid (PUFA) substrate for potent eicosanoid signaling to modulate inflammation and thrombosis and is controlled in part by tissue abundance. Fatty acid desaturase 1 (FADS1) catalyzes synthesis of omega-6 (n-3) AA and n-3 eicosapentaenoic acid (EPA). The rs66698963 polymorphism, a 22-base pair (bp) insertion-deletion 137 bp downstream of a sterol regulatory element in FADS2 intron 1, mediates expression of FADS1 in vitro, as well as exerting positive selection in several human populations. The associations between the polymorphism rs66698963 and plasma PUFAs as well as disease phenotypes are unclear. This study aimed to evaluate the relation between rs66698963 genotypes and plasma PUFA concentrations and blood lipid profiles. Plasma fatty acids were measured from a single sample obtained at baseline in 1504 healthy Chinese adults aged between 35 and 59 y with the use of gas chromatography. Blood lipids were measured at baseline and a second time at the 18-mo follow-up. The rs66698963 genotype was determined by using agarose gel electrophoresis. Linear regression and logistic regression analyses were performed to assess the association between genotype and plasma PUFAs and blood lipids. A shift from the precursors linoleic acid and α-linolenic acid to produce AA and EPA, respectively, was observed, consistent with FADS1 activity increasing in the order of genotypes D/D to I/D to I/I. For I/I compared with D/D carriers, plasma concentrations of n-6 AA and the ratio of AA to n-3 EPA plus docosahexaenoic acid (DHA) were 57% and 32% higher, respectively. Carriers of the deletion (D) allele of rs66698963 tended to have higher triglycerides (β=0.018; SE: 0.009; P=0.05) and lower HDL cholesterol (β=-0.008; SE: 0.004; P=0.02) than carriers of the insertion (I) allele. The rs66698963 genotype is significantly associated with AA concentrations and AA to EPA+DHA ratio, reflecting basal risk of inflammatory and related chronic disease phenotypes, and is correlated with the risk of dyslipidemia. This trial was registered at chictr.org.cn as ChiCTR-EOC-17012759.

Investigation of Haloacetic acids (HAAs) levels in water supply and its correlated HAAs formation

Haloacetic acids (HAAs) are usually found as disinfecting by-products in water supply. This study aims to investigate the concentration of HAA5 levels and to predict the HAA5 formation by multiple linear regression equations. HAA5 in the university water supply and the vicinity were analyzed by the mass detector (GC-MS) method with the use of gas chromatography. It was found that HAAs in 8 of 19 water samples were higher than US.EPA standard of 60 μg/L. The concentration HAA5 were ranged from 60 to 300 μg/L. The residual chlorine in the water samples were found between 1.2 - 1.8 mg/L which was above the standard set of 0.2 - 1.0 mg/L. The HAA5, pH, DOC, Free Cl2 variables were used to predict the correlation formation by multiple linear regression analysis at the 0.05 level of significance. It should be noted that correlation coefficient among target variables was high at the 0.91 level of statistically significant.

Evaluation of multiple alternative instrument platforms for targeted and non-targeted dioxin and furan analysis.

The use of gas chromatography coupled to high-resolution magnetic sector mass spectrometers (GC-HRMS) is well established for dioxin and furan analysis. However, the use of gas chromatography coupled to triple quadrupole (MS/MS) and time of flight (TOF) mass spectrometers with atmospheric pressure ionization (API) and traditional electron ionization (EI) for dioxin and furan analysis is emerging as a viable alternative to GC-HRMS screening. These instruments offer greater versatility in the lab for a wider range of compound identification and quantification as well as improved ease of operation. The instruments utilized in this study included 2 API-MS/MS, 1 traditional EI-MS/MS, an API-quadrupole time of flight mass spectrometer (API-QTOF), and a EI-high-resolution TOF (EI-HRTOF). This study compared these 5 instruments to a GC-HRMS using method detection limit (MDLs) samples for dioxin and furan analysis. Each instrument demonstrated acceptable MDL values for the 17 chlorinated dioxin and furans studied. The API-MS/MS instruments provide the greatest overall improvement in MDL value over the GC-HRMS with a 1.5 to 2-fold improvement. The API-QTOF and EI-TOF demonstrate slight increases in MDL value as compared with the GC-HRMS with a 1.5-fold increase. The 5 instruments studied all demonstrate acceptable MDL values with no MDL for a single congener greater than 5 times that for the GC-HRMS. All 5 instruments offer a viable alternative to GC-HRMS for the analysis of dioxins and furans and should be considered when developing new validated methodologies.

The Antioxidant Content and Protective Effect of Argan Oil and Syzygium aromaticum Essential Oil in Hydrogen Peroxide-Induced Biochemical and Histological Changes.

Oxidative stress is an important etiology of chronic diseases and many studies have shown that natural products might alleviate oxidative stress-induced pathogenesis. The study aims to evaluate the effect of Argan oil and Syzygium aromaticum essential oil on hydrogen peroxide (H2O2)-induced liver, brain and kidney tissue toxicity as well as biochemical changes in wistar rats. The antioxidant content of Argan oil and Syzygium aromaticum essential oil was studied with the use of gas chromatography. The animals received daily by gavage, for 21 days, either distilled water, Syzygium aromaticum essential oil, Argan oil, H2O2 alone, H2O2 and Syzygium aromaticum essential oil, or H2O2 and Argan oil. Blood samples were withdrawn on day 21 for the biochemical blood tests, and the kidney, liver and brain tissue samples were prepared for histopathology examination. The results showed that the content of antioxidant compounds in Syzygium aromaticum essential oil is higher than that found in Argan oil. H2O2 increased level of blood urea, liver enzymes, total cholesterol, Low Density Lipoprotein (LDL-C), Triglycerides (TG) and Very Low Density Lipoprotein (VLDL), and decreased the total protein, albumin and High Density Lipoprotein-cholesterol (HDL-C). There was no significant effect on blood electrolyte or serum creatinine. The histopathology examination demonstrated that H2O2 induces dilatation in the central vein, inflammation and binucleation in the liver, congestion and hemorrhage in the brain, and congestion in the kidney. The H2O2-induced histopathological and biochemical changes have been significantly alleviated by Syzygium aromaticum essential oil or Argan oil. It is concluded that the Argan oil and especially the mixture of Argan oil with Syzygium aromaticum essential oil can reduce the oxidative damage caused by H2O2, and this will pave the way to investigate the protective effects of these natural substances in the diseases attributed to the high oxidative stress.

Perfumer, chemist, machine: gas chromatography and the industrial search to “improve” flavor

Drawing from published accounts of the use of gas chromatography (GC) in the food industry, found in industry-specific journals, this article examines the role of GC in changing how perfumers and flavorists think about and shape the sense-able world. It shows that the development of a novel twist on GC – the use of an expert’s nose as a detecting device directly connected to the exit gasses of the gas chromatograph, rather than an instrumental detector – opened the door to a new way of categorizing aromatic molecules that changed the purpose of expert practices of smelling within the industrial context. The marriage of human and machine not only offered those tasked with developing the perfect flavor the tools for gaining information about what aspects of a flavor they wished to keep, it also helped identify what aspects they ought to discard or obfuscate in their search to improve the natural world of tastes and smells.

The chemical toxicological investigation of gamma-hydroxybutyric acid in biological objects and the interpretation of the results of the analysis

The authors propose a method for the quantitative determination of gamma-hydroxybutyric acid (GHBA) in biological objects including biological fluids (blood, urine) and tissues with the use of gas chromatography with mass-selective detector. The samples for the analysis were prepared by liquid-liquid extraction by butyl acetate with subsequent derivatization using a N,O-Bis(trimethylsilyl)trifluoroacetamide/Trimethylchlorosilane mixture (BSTFA + 1%TMCS). The graded graphs were linear in the range of GHBA concentrations from 26.4 to 1321.6 mg/l. Coefficients of correlation for all the graphs were higher than 0.999. The threshold of detectability for GHBA in blood, urine, and internal organs was 10 mg/l, the quantification limit concentration 26 mg/l.

Use of Gas Chromatography to Quantify Short Chain Fatty Acids in the Serum, Colonic Luminal Content and Feces of mice.

Short-Chain Fatty Acids (SCFAs) are a product of the fermentation of resistant starches and dietary fibers by the gut microbiota. The most important SCFA are acetate (C2), propionate (C3) and butyrate (C4). These metabolites are formed and absorbed in the colon and then transported through the hepatic vein to the liver. SCFAs are more concentrated in the intestinal lumen than in the serum. Butyrate is largely consumed in the gut epithelium, propionate in the liver and acetate in the periphery. SCFAs act on many cells including components of the immune system and epithelial cells by two main mechanisms: activation of G-protein coupled receptors (GPCRs) and inhibition of histone deacetylase. Considering the association between changes in SCFA concentrations and the development of diseases, methods to quantify these acids in different biological samples are important. In this study, we describe a protocol using gas chromatography to quantify SCFAs in the serum, feces and colonic luminal content. Separation of compounds was performed using a DB-23 column (60 m x 0.25 mm internal diameter [i.d.]) coated with a 0.15 µm thick layer of 80.2% 1-methylnaphatalene. This method has a good linear range (15-10,000 µg/ml). The precision (relative standard deviation [RSD]) is less than 15.0% and the accuracy (error relative [ER]) is within ± 15.0%. The extraction efficiency was higher than 97.0%. Therefore, this is cost effective and reproducible method for SCFA measurement in feces and serum.

Detection of Organophosphate Residues in Selected Crops in Benguet and Mt. Province, Philippines

High input agricultural systems refer to food production systems that use inorganic chemicals such as pesticides and fertilizer inputs intensively, with the aim of significantly increasing yield levels. This leads to the accumulation of pesticide residues and heavy metals in the crops and in the environment. This study was undertaken to determine the presence and concentration of toxic pesticide residues in cabbage, potato, and sweet peas in selected farms in Pactil, Mt. Data, Mountain Province and Loo, Buguias, Benguet. Through the use of gas chromatography (GC), findings show that about 18 pesticide residues (organophosphates) were detected in the crop samples. Furthermore, concentrations of toxic organophosphate residues were generally elevated and higher than MRL. A general default MRL of 0.01 mg kg-1applies where a pesticide is not specifically mentioned, which means that there is no established MRL. If the default level of 0.01mg kg-1 is applied for those without MRL then almost all samples would be unsafe for consumption. Other vegetables crops, soil and water in the study area may also be analyzed for the presence of active compounds and other toxic chemicals.

Comparison of GC-VUV, GC-FID, and comprehensive two-dimensional GC–MS for the characterization of weathered and unweathered diesel fuels

Characterization of diesel fuels and degraded diesel fuels in the environment is a common issue nowadays. Providing definitive information for litigation regarding determination and distinguishing the origins or sources of fuel spill contamination has been a significant need among the environmental forensics community. Diesel fuels contain more complex chemicals and isomers compared to gasoline. Here, we compare the use of gas chromatography – vacuum ultraviolet spectroscopy (GC-VUV), gas chromatography – flame ionization detection (GC-FID), and comprehensive two-dimensional gas chromatography – mass spectrometry (GC × GC–MS) for diesel fuel and weathered diesel fuel analysis in fingerprinting biomarkers. GC-VUV is a relatively new technique that can rapidly acquire full absorption spectra from 120 to 240 nm. Class information about individual components is readily obtained based on reference to a library of matched spectra. Direct comparison of GC-VUV, GC-FID, and GC × GC–MS was undertaken to identify different classes of compounds and biomarkers. Using GC-VUV, numerous peaks representing minor and major components were classified into different classes by applying spectral filters and, in some cases, spectral deconvolution. Isoprenoid biomarkers, such as pristane and phytane, and their ratios with n-alkanes, C17 and C18, respectively, were determined The biomarker ratio results from GC-VUV matched well with both GC-FID and GC × GC–MS. About 5%–20% difference in measured biomarker ratios were obtained for a series of commercial weathered diesel standard samples, which is good enough to allow the discrimination of different weathered diesel samples, according to prior literature.

Optimization of Ultrasound-Assisted Extraction of Oil from Canola Seeds with the Use of Response Surface Methodology

In the current study, response surface optimization of canola oil extraction assisted by 35 kHz, 800 W ultrasound waves and with the use of hexane and 3:2 hexane–isopropanol at the proportion of 3/2 as solvents was conducted. The influence of extraction temperature (35, 45, and 55°C), ultrasound treatment time (30, 60, and 90 min), and solvent-to-canola (sample) ratio (5, 10, and 15 (% v/w)) on the percentage of the extracted oil and oxidative stability of the extracted oil was analyzed through Box-Behnken design. The achieved results revealed that the optimized conditions for canola oil extraction (22.39% efficiency) by hexane was 87 min ultrasound treatment at 55°C and solvent-to-canola proportion of 6.39 (% v/w). On the other hand, the optimized conditions for canola oil extraction (30.66% efficiency) by hexane–isopropanol mixture were 69.5 min ultrasound treatment at 55°C and solvent-to-canola ratio of 9.12 (% v/w). The obtained outcomes revealed that ultrasound waves significantly improved the extraction efficiency compared to Soxhlet extraction. The extraction efficiency was improved when hexane–isopropanol mixture was applied. In optimized condition, oxidative stability of the extracted oil has been achieved at 12.55 and 40.9 h, respectively, once hexane and hexane–isopropanol were used as solvents for extraction. Oxidative stability presented considerable enhancement with an increase in ultrasound treatment. Extracted oil with the use of mixed solvent (hexane–isopropanol) presented higher value for oxidative stability compared to the extracted oil with the use of hexane as a solvent. Comparison between the ultrasound-assisted and Soxhlet extracted oils with the use of gas chromatography presented no significant difference in their fatty acid profiles.

Use of gas chromatography–mass spectrometry–olfactometry and a conventional flask test to identify off-flavor compounds generated from phenylalanine during chlorination of drinking water

Off-flavor in drinking water can be caused by transformation products (TPs) generated from organic compounds, such as amino acids, present during chlorination. However, the contributions of many of these TPs to overall off-flavor have not been quantified, mainly because the lack of appropriate chemical standards prevents sensory evaluation by means of a conventional flask test. In the present study, we used gas chromatography–mass spectrometry–olfactometry (GC-MS-O) to identify compounds responsible for the off-flavor generated by chlorination of an aqueous solution of the amino acid phenylalanine, and we propose a sensory evaluation procedure for quantification of the contributions of the identified TPs to the overall off-flavor, regardless of the availability of chemical standards of the TPs. GC-MS-O revealed that two TPs, N-chlorophenylacetaldimine and 2-chloro-2-phenylacetaldehyde, for which chemical standards are not commercially available, were the main components responsible for the off-flavor of the chlorinated solution. By using a sensory evaluation procedure involving a combination of GC-MS-O and a conventional flask test, we quantified the contributions of TPs to the overall off-flavor of the chlorinated solution. Approximately 60% of the off-flavor was attributable to free chlorine (13%), 2-chloro-2-phenylacetaldehyde (13%), trichloramine (12%) phenylacetaldehyde (11%) phenylacetonitrile (8%), and N-chlorophenylacetaldimine (2%). Treatment with powdered activated carbon (PAC) removed the off-flavor. Experiments with chlorination of 15N-labeled phenylalanine suggested that PAC reductively decomposed trichloramine into N2 gas and adsorbed all of the other identified TPs. Superfine PAC (median diameter, 0.7 μm) removed the off-flavor more rapidly than normal-size PAC (median diameter, 8.0 μm).

Dietary long-chain fatty acids and carbohydrate biomarker evaluation in a controlled feeding study in participants from the Women’s Health Initiative cohort ,

Background: Biomarkers of macronutrient intake are lacking. Controlled human feeding studies that preserve the normal variation in nutrient and food consumption are necessary for the development and validation of robust nutritional biomarkers.Objective: We aimed to assess the utility of serum phospholipid fatty acids (PLFAs) as biomarkers of dietary intakes of fatty acids, total fat, and carbohydrate.Design: We used an individualized controlled feeding study in which 153 postmenopausal women from the Women's Health Initiative (WHI) were provided with a 2-wk controlled diet that mimicked each individual's habitual food intake. A total of 41 PLFAs were measured with the use of gas chromatography in end-of-feeding-period fasting serum samples and expressed in both relative and absolute concentrations. R2 values (percentages of variation explained) from linear regressions of (ln-transformed) consumed fatty acids (individual, groups, and broad categories) on (ln-transformed) corresponding measures of serum PLFAs alone and together with selected participant-related variables (age, race/ethnicity, body mass index, season of study participation, education level, and estimated energy intake from doubly labeled water) were used for evaluation against established urinary recovery biomarkers of energy and protein intake as benchmarks. Models to predict intakes of other nutrients were also explored.Results: Intakes of eicosapentaenoic acid and docosahexaenoic acid achieved the benchmark of R2 > 36% with or without covariates. When all 41 serum PLFAs and participant-related covariates were initially included in the model for selection, cross-validated R2 achieved >36% for consumed total carbohydrate (grams per day), total saturated fatty acids (SFAs), percentage of energy from SFAs, and total trans fatty acids with serum PLFAs in both relative and absolute concentrations.Conclusions: Serum PLFA biomarkers perform similarly to established energy and protein urinary recovery biomarkers in describing intake variations for several nutrients and, thus, appear suitable for application in this population of postmenopausal women. This approach represents an important methodologic contribution toward the utilization of nutritional biomarkers to assess macronutrient intake. This trial was registered at clinicaltrials.gov as NCT00000611.

Determining Insulation Condition of 110kV Instrument Transformers Using Gas Chromatography

The paper dwells on determining insulation condition of high voltage instrument transformers and contains both theoretical contributions and measurements (performed on electrical equipment in 110/20kV substations in Sibiu county, Romania) regarding, namely, the partial discharge phenomena, highlighted using gas chromatography. Measurements have shown the negative effects of these internal possible mechanisms, such as arcing, corona discharges, spark discharges (local penetrations of insulation, possessing a high density of ionization or appearance of low energy arcing, sometimes described – not as an absolute rule – as partial discharge), on the solid insulation of high voltage instrument transformers. These conditions occurring singly or as several simultaneous events can result in decomposition of the insulating materials and the formation of various combustible and noncombustible gases. The technique used by the authors proved itself to be up to date, extremely advantageous, with extraordinary precision, speed and handling flexibility. Very reproductive results recommend the use of gas chromatography.

The use of gas chromatography in determining the sorption capacity of the adsorbent

The study specifies the characteristics of adsorbents for their subsequent use in adsorbers that are intended to trap aromatics from the juice vapour at the temperature and vacuum concentration of juices and extracts of plant materials. The paper presents our findings on the specific sorption capacities for aromatics of activated carbon BAC-A and porous polymers, such as polisorb-1, polisorb-10 and GC tenax. The experimental studies employed the dynamic method of gas chromatography with the use of the flame ionization detector. The trace curve of the adsorbate substance in the chromatogram allowed plotting adsorption isotherms and, consequently, calculating the specific capacities of adsorbents for camphor and isoamylol, as well as revealing that polysorb-1 is selective to isoamylol, whereas tenax and BAC-A – to camphor. The experiment findings have proved the applicability of this method for different adsorbents intended for adsorption of substances in the gas phase. The obtained data on the sorption capacities of the selected adsorbents are essential to calculate adsorption systems for trapping aromatics during the concentration of juices and extracts.

Determination of polycyclic aromatic hydrocarbon levels of groundwater in Ife north local government area of Osun state, Nigeria.

This study determined the presence and levels of Polycyclic Aromatic Hydrocarbons (PAHs) of groundwater in Moro, Edun-Abon, Yakoyo and Ipetumodu communities in Ife-North Local Government Area of Osun State. This was with a view to create public awareness about the safety of groundwater as a source for domestic purposes (e.g., drinking, cooking etc.) in non-industrial area. Water samples were collected on seasonal basis, comprising of three months (August–October) in the wet season and three months (December–February) in the dry season. The PAHs in the water samples were extracted with n-hexane using liquid–liquid extraction method, while their qualitative identifications and quantitative estimations were carried out with the use of gas chromatography. Levels of PAHs detected showed predominance of light PAHs (less than four fused rings) for both wet and the dry seasons. Higher concentrations of PAHs were recorded during the wet season than the dry season. The study concluded that the groundwater in the communities was contaminated with light PAHs and the total PAHs in this area exceeded the maximum permissible limit of 10 μg L−1 recommended by World Health Organization (WHO) for safety of groundwater.

Influence of Sucrose, Glucose, Stevia Leaf and Stevioside on the Growth and Lactic Acid Production by Lactobacillus plantarum, Lactobacillus brevis and Lactobacillus casei

Probiotics are beneficial bacteria that exert beneficial health effects on the host. These bacteria produce lactic acid as a product of fermentation. The aim of this study was to optimize growth and production of lactic acid by three strains of probiotic bacteria at different concentrations of sucrose, glucose, stevia leaf and stevioside. These three strains were Lactobacillus casei, Lactobacillus brevis and Lactobacillus plantarum. Lactic acid production and bacterial growth were, respectively, estimated by use of gas chromatography and colony-forming units (CFU) assay. The highest bacterial growth and lactic acid production in these three strains were obtained by high concentration of sucrose. Among these three bacteria, Lact. casei and Lact. brevis can produce more lactic acid compared to Lact. plantarum. All strains could produce lactic acid in the presence of sucrose, glucose and stevia leaf extract in a dose dependent manner. The effect of stevioside on lactic acid production in these strains at high and low concentrations was almost same. In conclusion, data indicate that sucrose is the best carbon source for lactic acid production and bacterial growth. Stevioside and stevia leaf also have a good potential to increase lactic acid production in these three strains.

Dietary intake and adipose tissue content of α-linolenic acid and risk of myocardial infarction: a Danish cohort study1–3

Background: Intake of the plant-derived ω-3 (n–3) fatty acid α-linolenic acid (ALA, 18:3; n–3) may reduce coronary heart disease (CHD) risk, but the results of previous studies have been inconsistent.Objective: We aimed to investigate the association between dietary intake of ALA, adipose tissue content of ALA, and risk of incident myocardial infarction (MI).Design: A total of 57,053 participants, aged 50–64 y, were enrolled in the prospective Danish cohort study Diet, Cancer and Health between 1993 and 1997. Dietary intake of ALA was assessed with the use of a validated semiquantitative food-frequency questionnaire in the full cohort, whereas the adipose tissue content of ALA was determined with the use of gas chromatography in all incident MI cases and in a random sex-stratified sample of the total cohort (n = 3500).Results: During a median of 17 y of follow-up, we identified 2177 male and 912 female cases of MI. After appropriate exclusions, we included 2124 men and 854 women for analyses of dietary intake of ALA, whereas 1994 men and 770 women were included in the analysis of the adipose tissue content of ALA. In multivariate analyses that were conducted with the use of restricted cubic splines and adjusted for established CHD risk factors, weak positive associations in men and weak U-shaped associations in women were shown between both dietary intake and the adipose tissue content of ALA and risk of MI, but these associations were not statistically significant. Additional adjustments for dietary factors did not influence the observed associations numerically.Conclusion: This study suggests that ALA has no appreciable association with risk of incident MI in either men or women.