Stable Isotope Dilution Assay Research Articles

Validation of an improved stable isotope dilution assay for folates and its application to Brazilian plants as non‐conventional foods

LebensmittelchemieVolume 76, Issue S2 p. S2-111-S2-111 Analytik (ATW-A) Validation of an improved stable isotope dilution assay for folates and its application to Brazilian plants as non-conventional foods L. Obermaier, L. Obermaier Freising/D Technical University of Munich, Maximus-von-Imhof-Forum 2, 85354 Freising, GermanySearch for more papers by this authorB. Paes Miglioli da Mata, B. Paes Miglioli da Mata Araraquara/BRASearch for more papers by this authorA. Gonzaga dos Santos, A. Gonzaga dos Santos Araraquara/BRASearch for more papers by this authorM. Rychlik, M. Rychlik Freising/DSearch for more papers by this author L. Obermaier, L. Obermaier Freising/D Technical University of Munich, Maximus-von-Imhof-Forum 2, 85354 Freising, GermanySearch for more papers by this authorB. Paes Miglioli da Mata, B. Paes Miglioli da Mata Araraquara/BRASearch for more papers by this authorA. Gonzaga dos Santos, A. Gonzaga dos Santos Araraquara/BRASearch for more papers by this authorM. Rychlik, M. Rychlik Freising/DSearch for more papers by this author First published: 01 September 2022 https://doi.org/10.1002/lemi.202259068AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume76, IssueS2September 2022Pages S2-111-S2-111 RelatedInformation

Absolute and relative quantitation of amylase/trypsin-inhibitors by LC-MS/MS from wheat lines obtained by CRISPR-Cas9 and RNAi

Quantitation of wheat proteins is still a challenge, especially regarding amylase/trypsin-inhibitors (ATIs). A selection of ATIs was silenced in the common wheat cultivar Bobwhite and durum wheat cultivar Svevo by RNAi and gene editing, respectively, in order to reduce the amounts of ATIs. The controls and silenced lines were analyzed after digestion to peptides by LC-MS/MS with different approaches to evaluate changes in composition of ATIs. First, a targeted method with stable isotope dilution assay (SIDA) using labeled peptides as internal standards was applied. Additionally, four different approaches for relative quantitation were conducted, in detail, iTRAQ labeled and label free quantitation (LFQ) combined with data dependent acquisition (DDA) and data independent acquisition (DIA). Quantitation was performed manually (Skyline and MASCOT) and with different proteomics software tools (PLGS, MaxQuant, and PEAKS X Pro). To characterize the wheat proteins on protein level, complementary techniques as high-performance liquid chromatography (HPLC) and gel electrophoresis were performed. The targeted approach with SIDA was able to quantitate all ATIs, even at low levels, but an optimized extraction is necessary. The labeled iTRAQ approach revealed an indistinct performance. LFQ with low resolution equipment (IonTrap) showed similar results for major ATIs, but low abundance ATIs as CM1, were not detectable. DDA measurements with an Orbitrap system and evaluation using MaxQuant showed that the relative quantitation was dependent on the wheat species. The combination of manual curation of the MaxQuant search with Skyline revealed a very good performance. The DIA approach with analytical flow found similar results compared to absolute quantitation except for some minor ATIs, which were not detected. Comparison of applied methods revealed that peptide selection is a crucial step for protein quantitation. Wheat proteomics faces challenges due to the high genetic complexity, the close relationship to other cereals and the incomplete, redundant protein database requiring sensitive, precise and accurate LC-MS/MS methods.

Decoding the Specific Roasty Aroma Wuyi Rock Tea (Camellia sinensis: Dahongpao) by the Sensomics Approach.

Aroma extract dilution analysis was performed on volatile fractions extracted from a freshly prepared Dahongpao (DHP) tea infusion using solvent-assisted flavor evaporation, yielding 65 odor-active domains with flavor dilution factors ranging between 32 and 32,768. In addition, six aromatic substances were captured by headspace analysis. Quantitation of 54 compounds by an internal standard method and stable isotope dilution assays revealed that the concentrations of 32 odorants exceeded their respective orthonasal odor threshold values in tea infusion. The results of odor activity values (OAVs) suggested that 2-metylbutanal (malty) and γ-hexalactone (coconut-like) had the highest OAVs (248 and 154). Eight odorants including γ-hexalactone (OAV 154), methyl 2-methylbutanoate (59), phenylacetic acid (7.2), acetylpyrazine (5.7), 2-methoxyphenol (3.4), p-cresol (2.7), 2,6-diethylpyrazine (2.7), and vanillin (1.8) were newly identified as key odorants in DHP tea infusion. An aroma recombination model in a non-volatile matrix extracted from tea infusion satisfactorily mimicked the overall aroma of DHP tea infusion, thereby confirming the identification and quantitative experiments. Omission experiments verified the obvious significance of 6-methyl-5-hepten-2-one (OAV 91), 2-ethyl-3,5-dimethylpyrazine (19), 4-hydroxy-2,5-dimethylfuran-3(2H)-one (13), and acetylpyrazine (5.7) as key odorants for the special roasty and caramel-like aroma of DHP tea.

Characterization of Odorants in Southern Mountain Mint, Pycnanthemum pycnanthemoides.

Southern mountain mint, Pycnanthemum pycnanthemoides (Leavenw.) Fernald, is a mountain mint species endemic to the southeastern United States. The odorants responsible for the plant's odor have not been previously characterized. In this study, 28 odorants were identified in a high-vacuum distillate of P. pycnanthemoides employing gas chromatography-olfactometry and gas chromatography-mass spectrometry. Flavor dilution (FD) factors were determined by aroma extract dilution analysis. Ten odorants with FD factors ≥16 were quantitated by stable isotope dilution assays, odor activity values (OAVs) were calculated, and the stereochemistry of chiral odorants was determined. Odorants with OAV ≥1 included β-ionone (floral, violet; OAV 310), piperitenone (mint; OAV 100), piperitone (mint; OAV 87), linalool (floral, citrus; OAV 45), myrcene (terpeny; OAV 35), (R)-(+)-pulegone (mint, medicinal; OAV 18), (2S,5R)-(-)-menthone (mint, fresh; OAV 6.6), and 1,8-cineole (eucalyptus; OAV 4.0). An odor simulation model based on the quantitative analysis was a close match to the sensory attributes of an aqueous infusion of dried P. pycnanthemoides. The study's results establish insights into the complex odor profile of P. pycnanthemoides and provide a foundation for future studies on the odor variability within P. pycnanthemoides and other species of the Pycnanthemum genus.

A prospective study of total urinary deoxynivalenol in adolescents in Shanghai, China

There is growing interest in deoxynivalenol (DON) exposure during puberty because experimental evidence shows that DON-exposed to adolescents are more sensitive to DON and have limited detoxification ability. Nevertheless, there have been few surveys of DON exposure for adolescents in China. Furthermore, little is known about the effects of collection times on risk exposure. In the study, we estimated the risk of DON exposure for adolescents in Shanghai and explore the effects of collection time, areas, sex and BMI on intake estimates. A total of 315 adolescents aged 14–16 years, including 161 boys and 154 girls, were recruited. Urine samples were collected for three consecutive days and digested with β-glucuronidase and then purified using a DON-immunoaffinity column (IAC). Total deoxynivalenol levels were measured using liquid chromatography-tandem mass spectrometry (LC–MS/MS) in combination with a stable isotope dilution assay (SIDA). DON was detected in 945 morning urine samples taken from 315 individuals for three consecutive days. The mean estimated dietary intake of DON did not exceed the tolerable daily intake (TDI) of l μg/kg·bw/day, showing that exposure of adolescents in Shanghai is not of concern. However, 10–20% of probable daily intake (PDI) values exceed the TDI, indicating potential adverse effects. In addition, the DON concentration at the population level did not differ for urine samples collected at different times except for those of overweight adolescents. Therefore, assessment of exposure to DON by monitoring the morning urine of a healthy adolescent, except for overweight people, provides an appropriate estimate of exposure and related risk at the population level, but intake estimates for individuals are uncertain; these could be used to assess exposure of adolescents to DON rapidly and effectively for epidemiological investigations.

Analysis of ochratoxin A, aflatoxin B1 and its biosynthetic precursors in cheese – Method development and market sample screening

The presence of Penicillium and Aspergillus fungi during cheese production may lead to the formation of ochratoxin A, aflatoxins, as well as their partly mutagenic biosynthetic precursors. However, data about the presence of these toxins in final cheese is scarce. In the present study, a quantification method for the toxicologically highly relevant compounds ochratoxin A (OTA), aflatoxin B1 (AFB1), sterigmatocystin (STC), and versicolorin A (VerA) was developed and applied for a market screening of hard, semi-hard, and soft cheese samples. The developed method was based on a QuEChERs approach with dimethylsulfoxide as keeper reagent. This stable isotope dilution assay for OTA, AFB1 and STC achieves high sensitivity (limits of detection: 0.02 μg/kg for AFB1, 0.01 μg/kg for STC and 0.37 μg/kg for OTA). However, in certain hard cheese types, the toxins showed matrix binding effects, leading to reduced recovery rates. When applying the method to market samples, detectable amount of STC in eight out of ten grated hard cheese samples up to 4.99 μg/kg and OTA in three of these samples up to 26.56 μg/kg were revealed. Only three out of the 53 further samples contained detectable amounts of mycotoxin. Thus, it can be assumed that the state of maturation and the process of grating favours the presence of OTA and STC in cheese, based on the market screening of 62 market samples. More comprehensive data are required to draw more detailed conclusions of the parameters determining the susceptibility of certain cheese types for mycotoxin contamination.

Elucidation of the interaction between fructose and key aroma compounds in watermelon juice via Raman spectroscopy and nuclear magnetic resonance

Food matrix composition is an important factor affecting the release of aroma compounds. In the present study, four key aroma compounds (namely, hexanal, nonanal, (E)-2-nonenal, and acetophenone) were quantified in watermelon juice by stable isotope dilution assay. Using Raman spectroscopy and 1H NMR, it was found that hexanal, nonanal, and (E)-2-nonenal combine with fructose via hydrogen bonds, whereas acetophenone interact with fructose via π-π interaction. Entropy compensation at higher temperatures may explain the decrease in the contents of hexanal, nonanal, and (E)-2-nonenal released from the system. In contrast, the decrease in the contents of these aroma compounds by H2O2 might be due to the formation of a greater number of hydrogen bonds with carboxyl groups oxidized by aldehydes. This study contributes to further the understanding on the interaction between aroma compounds and fructose, thus offering practical insights on the regulation and control of flavor development in watermelon juice.

1H NMR spectrometry for methanol quantification in apple wines and ciders as optimised by comparison to SIDA-HS-GC-MS

Methanol, a hepato- and neurotoxic compound, is present in apple-based beverages as a by-product of the enzymatic degradation of pectin. Stable isotope dilution assay (SIDA) employing gas chromatography-mass spectrometry (GC–MS) is the state-of-the-art method for methanol determination in beverages. Despite higher initial investment costs, quantitative 1H NMR spectroscopy (qNMR) is a simpler and faster analytical technique to quantify numerous analytes in liquid foods. Beyond targeted analyses, qNMR spectral fingerprints in the product might be used for non-targeted analytical goals, such as adulteration and contamination detections. Here, an existing 1H-qNMR method used for wine profiling was optimised for methanol quantification in apple-based products, including cross-validation against a SIDA-HS-GC–MS method and reference values from interlaboratory trials. The optimisation involved a pivotally important estimation of a correction factor by an external calibration approach, making qNMR results comparable to SIDA-HS-GC–MS. The optimised qNMR method is suggested to be an alternative for methanol quantification in beverages.

Concise Syntheses of Alternariol, Alternariol-9-monomethyl Ether and Their D3-Isotopologues

AbstractAlternariol (AOH) and alternariol-9-monomethyl ether (AME) are two secondary metabolites of Alternaria fungi which can be found in various foodstuffs like tomatoes, nuts, and grains. Due to their toxicity and potential mutagenic activity the need for the development of high-throughput methods for the supervision of AOH and AME levels is of increasing interest. As the availability of both native and labeled AOH and AME analytical standards is very limited, we herein present a novel and concise approach towards their synthesis by employing a ruthenium-catalyzed ortho-arylation as the key step. Finally, we demonstrate their suitability as internal standards in stable-isotope dilution assay (SIDA)-HPLC-MS/MS analysis, a technique commonly used for the quantification of natural products in food and feed.

Synthesis of d6-deuterated analogues of aroma molecules-β-damascenone, β-damascone and safranal

β-Damascenone, a C13-norisoprenoid, is an important aroma compound not only in wine but also in the perfume and flavouring industries. Its key contribution to the floral aromas of many wine varieties, and impact on the overall wine aroma profile, make its quantification in various matrices of increasing interest and demand. The stable isotope dilution assay (SIDA) is one of the most precise analytical methods based on using isotopically labelled standards. Herein, we describe the synthesis of d6-β-damascenone, d6-β-damascone, and d6-safranal, other aroma compounds in nature, starting from the readily available deuterated starting material d6-acetone.

Chemo-sensory characterization of aroma active compounds of native oak wood in relation to their geographical origins

Oak wood contains aroma-active compounds that contribute significantly to the chemical structure, olfactory and gustatory qualities of alcoholic beverages and vinegars as by-products that have been either fermented and/or aged in oak barrels. The chemical composition of cooperage oak is highly variable, depending on the degree of toasting and natural seasoning. However, it is unclear whether the odor of oak varies according to different geographical regions and pedoclimatic conditions. Especially in view of the actual challenges in forestry in relation to climate change, the present study aimed at elucidating the odorous constituents of nine natural oak samples from Germany, Austria and Hungary with respect to these influencing parameters. The odor profiles of the oaks were compared, the potent odorants were determined, and selected odorants were quantified using stable isotope dilution assays (SIDA). The majority of the identified odorants in all samples were fatty acid degradation products, followed by a series of odorants with terpenoic structure and others resulting from the degradation of lignin. Several different odorants including 2-propenoic acid and cinnamaldehyde are reported here for the first time in oaks from different growth regions. Odor activity values (OAVs), calculated based on odor thresholds (OTs) in water, revealed hexanal, (E)-2-nonenal, (Z)-3-hexenal, eugenol, vanillin, and whiskey lactone as potent odorants for the oak odor. Principal component analysis of the data obtained from sensory evaluation, comparative aroma extract dilution analysis (cAEDA) and their corresponding quantified odorants showed that the highest separation rate was obtained for Hungarian oak, whereas Austrian and Bavarian oak samples were more similar. Recombination experiments by mixing the dominant odorants in their naturally occurring concentrations revealed a good agreement of the smell properties of the model mixture with the smell of the respective original sample. These findings aimat evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.

Analysis of the Ability to Produce Pleasant Aromas on Sour Whey and Buttermilk By-Products by Mold Galactomyces geotrichum: Identification of Key Odorants.

Currently, there is a growing demand for flavorings, especially of natural origin. It is worth paying attention to the biotechnological processes of flavor production, characterized by simplicity, high efficiency and relatively low cost. In this study, we analyzed the ability of the Galac tomyces geotrichum mold to transform by-products of the dairy industry: sour whey and buttermilk to complex flavour mixtures with pleasant, honey-rose aroma. Furthermore, the aroma complexity of the fermentation product has been carefully identified applying a sensomic approach involving the use of gas chromatography-olfactometry (GC-O), gas chromatography-mass spectrometry (GC-MS) and stable isotope dilution assay (SIDA) to identify and quantify aroma compounds. Based on the calculation of odor activity value (OAV), 13 key aroma compounds were present in both tested variants. The highest OAVs were found for phenylacetaldehyde (honey-like) in the buttermilk variant (912) and 2-phenylethanol (rose-like) in the sour whey variant (524). High values of this indicator were also recorded for phenylacetaldehyde (319) and 3-methyl-1-butanol with a fruity aroma (149) in the sour whey culture. The other compounds identified are 3-methylbutanal (malty), 2,3-butanedione (cheesy), isovaleric acid (cheesy), 3-(methylthio)-propanal (boiled potato), butanoic acid (vinegar), (E)-2-nonenal (fatty), ethyl furaneol (burnt sugar), dimethyl trisulfide (cabbage), and acetic acid (vinegar).

Characterization of Odorants in Chardonnay Marc Skins.

Chardonnay marc, consisting of grape skins, seeds, and stems, is a coproduct of grape juice production for Chardonnay wine making. The discovery that marc contains a rich source of health-promoting molecules has led to its growing popularity as a flavorful healthy food ingredient. However, the odorants responsible for its pleasant fruity aroma remain unknown. In this study, 35 odorants were identified in Chardonnay marc skins using solvent-assisted flavor evaporation (SAFE) and aroma extract dilution analysis (AEDA). Thirteen odorants were quantitated employing stable isotope dilution assays (SIDAs), and odor activity values (OAVs) were calculated. Odorants with OAVs >1 included 3-methylnonane-2,4-dione (hay, OAV 5800), β-ionone (floral, violets, OAV 2900), (2E,4E)-nona-2,4-dienal (fatty, OAV 1200), β-damascenone (cooked apple, OAV 370), hexanal (green, OAV 260), oct-1-en-3-one (mushroom, OAV 200), linalool (floral, citrus, OAV 61), (2E,4E)-deca-2,4-dienal (fatty, OAV 60), 2-phenylethanol (floral, rose, OAV 16), 3-(methylsulfanyl)propanal (potato, OAV 3.7), HDMF (caramel, OAV 2.0), and ethyl octanoate (fruity, OAV 1.1). An odor simulation model prepared using odorants with OAVs >1 sensorially matched the aroma of the Chardonnay marc skins. This investigation establishes a foundation for future studies aimed at determining the contribution of individual Chardonnay marc components (skins, seeds, and stems) to the aroma profile of Chardonnay marc powder and aiding producers in delivering optimal and consistent aroma profiles by region.

Characterization of Odorants in a 10-Year-Old Riesling Wine.

Riesling wines are mostly enjoyed as young wines, usually consumed within the first few years after bottling. Throughout several years of aging, Riesling wines begin to develop more robust flavor profiles, often displaying less fruity and floral notes and more pronounced maple, honey, and caramel notes. A body of scientific literature has been conducted on the aroma chemistry of young Riesling wines; however, comparatively less scientific reports have been published on the aroma chemistry of aged Riesling wines, and a comprehensive aroma analysis of a 10-year-old Riesling wine has not been previously completed. In this study, a total of 36 odorants were identified in a 10-year-old aged Riesling wine using solvent-assisted flavor evaporation and aroma extract dilution analysis. A total of 26 odorants were quantitated by employing stable isotope dilution assays. Odorants with high odor activity values (OAV) included wine lactone (coconut, OAV 460), ethyl octanoate (fruity, OAV 240), ethyl hexanoate (fruity, OAV 97), β-damascenone (cooked apple, OAV 60), 5-ethyl-3-hydroxy-4-methyl-(5H)-furan-2-one (maple, OAV 33), (S)-ethyl 2-methylbutanoate (fruity, OAV 22), 3-(methylsulfanyl) propanal (cooked potato, OAV 20), ethyl 2-methylpropanoate (fruity, OAV 9.5), ethyl butanoate (fruity, 7.1 OAV), and 1,1,6-trimethyl-1,2-dihydronapthalene (petrol, OAV 6.4). An odor simulation model prepared from all the odorants with an OAV greater than 1 closely matched the sensory profile of the authentic wine. The results of this study provide insight about odorants present in a 10-year-old bottle aged Riesling wine, and this knowledge may be useful for future studies aimed at probing the influence of aging on the aroma chemistry of Riesling wines and other white wines.

Development of Stable Isotope Dilution Assays for the Analysis of Natural Forms of Vitamin B12 in Meat.

The first multiple stable isotope dilution assay method was developed for the simultaneous determination of four cobalamins, namely, hydroxocobalamin (OHCbl), adenosylcobalamin (AdoCbl), methylcobalamin (MeCbl), and cyanocobalamin (CNCbl), in their native forms. The sample preparation was optimized with enzyme treatment and immunoaffinity purification. The analysis was performed by LC-MS/MS using respective 15N-labeled cobalamins as internal standards. Method validation resulted in limits of detection ranging from 0.19 to 0.58 ng/g and limits of quantification ranging from 0.68 to 1.73 ng/g. Recoveries at three levels were between 82 and 121%. Intra-day and inter-day precisions were below 6% and 11% RSD, respectively. The analysis of a reference material resulted in a variance of <1% from the certified value. The newly developed method demonstrated excellent sensitivity, recovery, accuracy, and reproducibility and was further applied to quantitate the four cobalamins in various meats.

Production of Four 15N-Labelled Cobalamins via Biosynthesis Using Propionibacterium freudenreichii.

Cobalamins (vitamin B12) are required by humans for their essential roles as enzyme cofactors in diverse metabolic processes. The four most common cobalamin vitamers are hydroxocobalamin (OHCbl), adenosylcobalamin (AdoCbl), methylcobalamin (MeCbl), and cyanocobalamin (CNCbl). Humans are not able to synthesise cobalamins de novo and thus must acquire them from external sources. Therefore, a reliable and robust analytical method to determine the cobalamins in dietary sources is highly required. For such a purpose, stable isotope dilution assays (SIDAs) with LC-MS/MS are most suited due to their superior sensitivity, specificity, and ability to compensate for matrix effects and analyte loss during sample work-up. However, a critical bottleneck for developing a SIDA method for cobalamins is the availability of stable isotope-labelled internal standards. In the present study, we harnessed the potential of Propionibacterium (P.) freudenreichii for the biosynthesis of 15N-labelled cobalamins. First, we developed a chemically defined medium (CDM) containing ammonium sulphate as a single nitrogen source except three essential vitamins that supported long-term stable growth of P. freudenreichii throughout continuous transfers. The CDM was further optimised for cobalamin production under different incubation schemes. With the optimised CDM and incubation scheme, fully 15N-labelled cobalamins were obtained in P. freudenreichii with a final yield of 312 ± 29 μg/L and 635 ± 102 μg/L, respectively, for [15N]-OHCbl and [15N]-AdoCbl. Additionally, an optimised incubation process under anaerobic conditions was successfully employed to produce specifically labelled [15N, 14N2]-cobalamins, with a yield of 96 ± 18 μg/L and 990 ± 210 μg/L, respectively, for [15N, 14N2]-OHCbl and [15N, 14N2]-AdoCbl. The labelled substances were isolated and purified by solid phase extraction and semi-preparative HPLC. Chemical modifications were carried out to produce [15N]-CNCbl and [15N]-MeCbl. Eventually, 15N-labelled compounds were obtained for the four cobalamin vitamers in high chromatographic and isotopic purity with desired 15N-enrichment and labelling patterns, which are perfectly suited for future use in SIDAs or other applications that require isotopologues.

Contribution of S. xylosus and L. sakei ssp. carnosus Fermentation to the Aroma of Lupin Protein Isolates.

Aroma-active compounds of lupin protein isolate and lupin protein isolate fermented with Staphylococcus xylosus and Lactobacillus sakei ssp. carnosus were investigated. The changes in aroma-active compounds were determined by application of aroma extract dilution analysis in combination with gas chromatography-mass spectrometry/olfactometry for identification, and by stable isotope dilution assays for quantification. A total of 30 aroma-active compounds for non-fermented and fermented samples were identified. The aroma profile of LPI fermented with Lactobacillus sakei ssp. carnosus was characterized as roasty and popcorn-like. Staphylococcus xylosus generated cheesy impressions, being in line with the fact that the main aroma compounds acetic acid, butanoic acid, and 2/3-methylbutanoic acid could be identified. Quantification of butanoic acid further confirmed these findings with the highest concentration of 140 mg/kg for LPI fermented with Staphylococcus xylosus. Our study provides insights into how fermentation utilizing different fermentative microbial strains, namely Staphylococcus xylosus and Lactobacillus sakei ssp. carnosus alters the aroma profile of lupin protein isolates. This demonstrates the potential of shaping fermented protein-based foods via targeted microbiological refinement.

Evaluation of gas chromatography for the separation of a broad range of isotopic compounds

The separation of deuterated compounds from their protiated counterparts is essential in areas of drug discovery and development, investigating kinetic isotope effects and quantitative methods of non-mass spectrometry-based stable isotope dilution assay (non-MS SIDA). The separations of 47 isotopologue pairs of common compounds and drugs were achieved by gas-liquid chromatography, employing twelve different stationary phases. Polydimethylsiloxane phase, phenyl substituted polydimethylsiloxane phases, wax phases, ionic liquid phases, and chiral stationary phases were selected to encompass a wide polarity range and diverse chemical interactions. The best-performing stationary phases are presented for separation of protic-polar, aprotic-dipolar, nonpolar analytes. Overall, the IL111i, SPB-20, and PAG stationary phases were remarkable in their ability to separate the isotopologues. The isotope effect was also evaluated. It was observed that nonpolar stationary phases often exhibit an inverse isotope effect in which heavier isotopic compounds elute earlier than their lighter counterparts. Conversely, polar stationary phases often show a normal isotope effect, while those of intermediate polarities can show both effects depending on the isotopologues. The location of deuterium atoms, however, affects isotopologue retention times. Deuterium substituted aliphatic groups appear to have a greater inverse isotope effect on retention than aromatic substituents.

Exploring the Lipids Involved in the Formation of Characteristic Lactones in Japanese Black Cattle.

The meat from Japanese Black cattle (Japanese Wagyu) is finely marbled and exhibits a rich and sweet aroma known as Wagyu beef aroma. To clarify the key metabolites involved in the aroma, we analyzed the correlation between lactone and lipid composition in Japanese Black cattle. Using gas chromatography-olfactometry, we identified 39 characteristic odorants of the intermuscular fat. Seven characteristic lactones considered to be involved in Wagyu beef aroma were quantified and compared in the marbled area and intermuscular fat using a stable isotope dilution assay. Among them, γ-hexalactone was the only lactone whose level was significantly higher in the marbled area. To explore the lipid species involved in lactone formation, we analyzed samples with different aroma characteristics. Liquid chromatography-mass spectrometry revealed eight lipid classes and showed significant differences in triacylglycerides (TAGs). To determine the molecular species of TAGs, we performed high-performance liquid chromatography analysis and identified 14 TAG species. However, these analyses showed that seven lactones had a low correlation with the TAGs. However, γ-hexalactone showed a positive correlation with linoleic acid. This study suggests that lipid composition affects the characteristic lactone profile involved in the Wagyu beef aroma.

Characterization of the key aroma compounds in three types of bagels by means of the sensomics approach

BackgroundTo evaluate the impact of cold fermentation time on bagel rolls, the key aroma-active compounds in the volatile fractions obtained from three different bagel rolls through solvent assisted flavor evaporation (SAFE) were sequentially characterized by an aroma extract dilution analysis (AEDA), quantified by stable isotope dilution and analyzed by odor activity values (OAVs) respectively.ResultsFindings revealed 40 aroma-active compounds with flavor dilution (FD) factor ranges of 2–1024. Of these, 22 compounds (FD ≥ 16) were quantified by stable isotope dilution assays (SIDA). Subsequent analysis of the 22 compounds by odor activity values (OAVs) revealed 14 compounds with OAVs ≥ 1 and the highest concentrations were obtained for 2,3-butanedione, 2-phenylethanol, 3-methylbutanal and acetoin respectively. Two recombination models of the bagels (i.e. 24 h and 48 h bagels) showed similarity to the corresponding bagels. Omission tests confirmed that 2,3-butanedione (buttery), acetoin (buttery), 2-acetyl-1-pyrroline (roasty), 5-methyl-2-furanmethanol (bread-like), (Z)-4-heptenal (biscuit-like) and 4-hydroxy-2,5-dimethyl-3(2H)-furanone, were the key aroma compounds. Additionally, acetic acid, butanoic acid, 2-phenylethanol (honey-like), 3-methylbutanoic acid, 2/3-methylbutanal, vanillin, 3-methylbutanol, methional were also important odorants of the bagel.ConclusionWhilst the long, cold fermented bagels exhibited roasty, malty, buttery, baked potato-like, smoky and biscuit-like notes, the control bagels produced similar but less intense odor notes.