Fatty Acid Esters of Hydroxy Fatty Acids (FAHFAs) Are Associated With Diet, BMI, and Age

Background: Fatty acid esters of hydroxy fatty acids (FAHFAs) are a group of fatty acids with potential anti-inflammatory and anti-diabetic effects. The blood levels of FAHFAs and their regulation in humans have hardly been studied.

Objective: We aimed to investigate serum FAHFA levels in well-characterized human cohorts, to evaluate associations with age, sex, BMI, weight loss, diabetic status, and diet.

Methods: We analyzed levels of stearic-acid-9-hydroxy-stearic-acid (9-SAHSA), oleic-acid-9-hydroxy-stearic-acid (9-OAHSA) and palmitic-acid-9-hydroxy-palmitic-acid (9-PAHPA) as well as different palmitic acid-hydroxy-stearic-acids (PAHSAs) by HPLC-MS/MS with the use of an internal standard in various cohorts: A cohort of different age groups (18–25y; 40–65y; 75–85y; Σn = 60); severely obese patients undergoing bariatric surgery and non-obese controls (Σn = 36); obese patients with and without diabetes (Σn = 20); vegetarians/vegans (n = 10) and omnivores (n = 9); and young men before and after acute overfeeding with saturated fatty acids (SFA) (n = 15).

Results: Omnivores had substantially higher FAHFA levels than vegetarians/vegans [median (25th percentile; 75th percentile) tFAHFAs = 12.82 (7.57; 14.86) vs. 5.86 (5.10; 6.71) nmol/L; P < 0.05]. Dietary overfeeding by supplementation of SFAs caused a significant increase within 1 week [median tFAHFAs = 4.31 (3.31; 5.27) vs. 6.96 (6.50; 7.76) nmol/L; P < 0.001]. Moreover, obese patients had lower FAHFA levels than non-obese controls [median tFAHFAs = 3.24 (2.80; 4.30) vs. 5.22 (4.18; 7.46) nmol/L; P < 0.01] and surgery-induced weight loss increased 9-OAHSA level while other FAHFAs were not affected. Furthermore, significant differences in some FAHFA levels were found between adolescents and adults or elderly, while no differences between sexes and between diabetic and non-diabetic individuals were detected.

Conclusions: FAHFA serum levels are strongly affected by high SFA intake and reduced in severe obesity. Age also may influence FAHFA levels, whereas there was no detectable relation with sex and diabetic status. The physiological role of FAHFAs in humans remains to be better elucidated.

Trial Registration: All studies referring to these analyses were registered in the German Clinical Trial Register (https://www.drks.de/drks_web/) with the numbers DRKS00009008, DRKS00010133, DRKS00006211, and DRKS00009797.

A high throughput toolbox for comprehensive flavor compound mapping in mint

Essential oils of the genus Mentha are extensively used as flavor ingredients in the industry. To overcome the time consuming and laborious traditional flavor analysis, a new quick, high-throughput toolbox based on a bead-beater homogenization followed by a UHPLC-MS/MS analysis has been developed and validated. While terpenes could be directly detected using atmospheric pressure chemical ionization (APCI), carbonyl compounds and alcohols required derivatization by 3-nitrophenylhydrazine (3-NPH) and glycidyltrimethylammonium chloride (GTMA) to ensure sufficient sensitivity for analysis of a single leaf. Using this approach, in total, 59 flavor-active metabolites representing the characteristic flavor of mint were quantified in leaves as well as in distilled oils using fast and robust UHPLC-MS/MS methods. The application of this toolbox enables a mapping of key pathways of mint flavor biosynthesis and can therefore support extensive breeding studies and the monitoring of chemosensate changes, depending on factors such as growth stages and environmental conditions.

Comprehensive structure-activity-relationship studies of sensory active compounds in licorice (Glycyrrhiza glabra)

Licorice saponins, the main constituents of Glycyrrhiza glabra L. roots, are highly appreciated by the consumer for their pleasant sweet and long lasting licorice taste. The objective of the present study was to understand the molecular features that contribute to bitter, sweet and licorice sensation of licorice roots, and whether individual compounds elicit more than one of these sensations. Therefore, a sensomics approach was conducted, followed by purification of the compounds with highest sensory impact, and by synthesis as well as full characterization via HRESIMS, ESIMS/MS and 1D/2D-NMR experiments. This led to the discovery and structure determination of 28 sweet, bitter and licorice tasting key phytochemicals, including two unknown compounds. A combination of sensorial, cell-based and computational analysis revealed distinct structural features, such as spatial arrangement of functional groups in the triterpenoid E-ring, driving to different taste sensations and sweet receptor hTAS1R2/R3 stimulation.

Sensomics-Assisted Flavor Decoding of Dairy Model Systems and Flavor Reconstitution Experiments

The whole sensometabolome of a typical dairy milk dessert was decoded to potentially serve as a blueprint for further flavor optimization steps of functional fat-reduced food. By applying the sensomics approach, a wide range of different dairy volatiles, semi and nonvolatiles, were analyzed by ultrahigh-performance liquid chromatography tandem mass spectrometry with or without derivatization presteps. While for volatile sulfur compounds with low odor thresholds, headspace solid-phase microextraction gas chromatography was established, abundant carbohydrates and organic acids were quantified by quantitative ¹H nuclear magnetic resonance spectroscopy. Validated quantitation, sensory reconstitution, and omission studies highlighted eight flavor-active compounds, namely, diacetyl, δ-tetra-, δ-hexa-, and δ-octadecalactone, sucrose, galactose, lactic acid, and citric acid as indispensable for flavor recombination. Furthermore, eight odorants (acetaldehyde, acetic acid, butyric acid, methanethiol, phenylacetic acid, dimethyl sulfide, acetoin, and hexanoic acid), all with odor activity values >1, additionally contributed to the overall flavor blueprint. Within this work, a dairy flavor analytical toolbox covering four different high-throughput methods could successfully be established showing potential for industrial applications.

Impact of exogenous maltogenic α-amylase and maltotetraogenic amylase on sugar release in wheat bread

The use of exogenous maltogenic α-amylases or maltotetraogenic amylases of bacterial origin is common in wheat bread production, mainly as antistaling agents to retard crumb firming. To study the impact of maltogenic α-amylase and maltotetraogenic amylase on straight dough wheat bread, we performed a discovery-driven proteomics approach with commercial enzyme preparations and identified the maltotetraogenic amylase P22963 from Pelomonas saccharophila and the maltogenic α-amylase P19531 from Geobacillus stearothermophilus, respectively, as being responsible for the amylolytic activity. Quantitation of mono-, di- and oligosaccharides and residual amylase activity in bread crumb during storage for up to 96 h clarified the different effects of residual amylase activity on the sugar composition. Compared to the control, the application of maltogenic α-amylase led to an increased content of maltose and especially higher maltooligosaccharides during storage. Residual amylase activity was detectable in the breads containing maltogenic α-amylase, whereas maltotetraogenic amylase only had a very low residual activity. Despite the residual amylase activities and changes in sugar composition detected in bread crumb, our results do not allow a definite evaluation of a potential technological function in the final product. Rather, our study contributes to a fundamental understanding of the relation between the specific amylases applied, their residual activity and the resulting changes in the saccharide composition of wheat bread during storage.

Sensory-Guided Multidimensional Exploration of Antisweet Principles from Gymnema sylvestre (Retz) Schult

We report on activity-guided investigation of the key antisweet principles of Gymnema sylvestre. Orosensory-guided fractionation by means of solid phase extraction, preparative 2D-LC, and semipreparative HPLC followed by accurate MS and 1D/2D NMR experiments revealed six known and three previously unknown gymnemic acids as the key constituents of seven highly sensory-active fractions. Localized via a modified comparative taste dilution analysis (cTDA) and taste modulation probability (TMP) based screening techniques, a strong intrinsic bitterness was also observed for gymnemic acids. In addition, the suppressive effects of the most abundant acids on the response of the human sweet taste receptor to sucrose were verified by means of a functional hTAS1R2/hTAS1R3 sweet taste receptor assay. This in vitro screening revealed large differences in antisweet activity among the isolated compounds, where gymnemic acids XV and XIX showed the highest sweet suppressing activity. This broad-based molecular characterization of the sweet taste inhibiting activity of Gymnema sylvestre will enable further insight into the molecular basis of sweet taste modulation at the receptor level.

Development of a Highly Sensitive Ultra-High-Performance Liquid Chromatography Coupled to Electrospray Ionization Tandem Mass Spectrometry Quantitation Method for Fecal Bile Acids and Application on Crohn's Disease Studies

In addition to their important role in fat digestion, bile acids are increasingly being used as markers for various diseases. The large diversity of bile acids results from the conversion of primary and conjugated bile acids into secondary bile acids by deconjugation and dehydroxylation reactions mediated by the intestinal microbiota. Here, we describe a fast and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for absolute quantitation of 45 bile acids in human or mouse feces in combination with a simple workup and extraction procedure. Method validation outlined excellent limits of detection and quantitation, linearity, selectivity, recovery, extraction loss, and precision. To investigate the connection between microbiome alterations and bile acid metabolism, the method was applied on a Crohn's disease study including patients with histologically documented active disease or remission as well as on a model using humanized mice. As the complex mechanism including genetic and environmental factors leading to the development of Crohn's disease is so far not completely understood, the study investigates the microbial metabolism of bile acids and the potential use of bile acid profiles to predict disease state.

Identification and Quantitation of Reaction Products from Quinic Acid, Quinic Acid Lactone, and Chlorogenic Acid with Strecker Aldehydes in Roasted Coffee

To gain comprehensive insight into the interactions of key coffee odorants, like the Strecker aldehydes, acetaldehyde, propanal, methylpropanal, 2- and 3-methylbutanal, and methional, and the nonvolatile fraction of coffee, an untargeted metabolomics approach was applied. Ultra performance liquid chromatography (UPLC)-time of flight (TOF)-mass spectrometry (ESI^-) profiling followed by statistical data analysis revealed a marker substance for a coffee beverage spiked with acetaldehyde with an accurate mass of 217.0703 [M - H]^-. This compound could be identified as a reaction product of quinic acid (QA) and acetaldehyde linked by acetalization at the cis-diol function of QA. Consequently, the acetalization of aldehydes, QA, 5-O-caffeoyl quinic acid (CQA), and quinic acid γ-lactone (QAL) was investigated by means of model reactions, followed by synthesis, isolation, and structure elucidation via UPLC-TOF-MS and 1D and 2D NMR techniques. UHPLC-MS/MS_MRM screening and the quantification of aldehyde adducts in coffee beverages revealed the presence of QA/acetaldehyde, -/propanal, -/methylpropanal, and -/methional reaction products and CQA/acetaldehyde, -/propanal, -/methylpropanal, -/2- and 3-methylbutanal, and -/methional and QAL/acetaldehyde adducts for the first time, in concentrations of 12-270 μg/L for QA/aldehydes, 5-225 μg/L for CQA/aldehydes, and 62-173 μg/L for QAL/acetaldehyde. The sensory characterization of the identified compounds showed bitter taste recognition thresholds of 48-297 μmol/L for CQA adducts and 658 μmol/L for QAL/acetaldehyde, while the QA adducts showed no bitter taste (<2000 μmol/L).

Supernatants of intestinal luminal contents from mice fed high-fat diet impair intestinal motility by injuring enteric neurons and smooth muscle cells

BACKGROUND

Damage to enteric neurons and impaired gastrointestinal muscle contractions cause motility disorders in 70% of diabetic patients. It is thought that enteric neuropathy and dysmotility occur before overt diabetes, but triggers of these abnormalities are not fully known. We tested the hypothesis that intestinal contents of mice with and without high-fat diet- (HFD-) induced diabetic conditions contain molecules that impair gastrointestinal movements by damaging neurons and disrupting muscle contractions.

METHODS

Small and large intestinal segments were collected from healthy, standard chow diet (SCD) fed mice. Filtrates of ileocecal contents (ileocecal supernatants; ICS) from HFD or SCD mice were perfused through them. Cultured intact intestinal muscularis externa preparations were used to determine whether ICS and their fractions obtained by solid-phase extraction (SPE) and SPE subfractions collected by high-performance liquid chromatography (HPLC) disrupt muscle contractions by injuring neurons and smooth muscle cells.

KEY RESULTS

ICS from HFD mice reduced intestinal motility, but those from SCD mice had no effect. ICS, aqueous SPE fractions and two out of twenty HPLC subfractions of aqueous SPE fractions from HFD mice blocked muscle contractions, caused a loss of nitrergic myenteric neurons through inflammation, and reduced smooth muscle excitability. Lipopolysaccharide and palmitate caused a loss of nitrergic myenteric neurons but did not affect muscle contractions.

CONCLUSIONS & INFERENCES

Unknown molecules in intestinal contents of HFD mice trigger enteric neuropathy and dysmotility. Further studies are required to identify the toxic molecules and their mechanisms of action.

Fast and Sensitive LC-MS/MS Method for the Quantitation of Saponins in Various Sugar Beet Materials

An LC-MS/MS method was developed for the simultaneous quantitative analysis of the following 11 triterpene saponins within different sugar beet materials and plant compartments: betavulgaroside I (1), betavulgaroside II (2), betavulgaroside III (3), betavulgaroside IV (4), betavulgaroside VIII (5), boussingoside A2 (6), 3-O-[β-d-glucopyranosyl-(1 → 2)-(β-d-xylopyranosyl-(1 → 3))-β-d-glucuronopyranosyl]-28-O-β-d-glucopyranosyl-3β-hydroxyolean-12-en-28-oic acid (7), betavulgaroside V (8), chikusetsusaponin IVa (9), calenduloside E (10), and ginsenoside R0 (11). Our results showed highly varying amounts of saponins within different varieties, roots, and leaves as well as different plant compartments. The amounts for sugar beet roots were in the range of 862 mg/kg to 2 452 mg/kg. They were mostly higher for leaves compared to roots of the same variety with amounts ranging from 907 mg/kg to 5 398 mg/kg. Furthermore, the occurrence of sugar beet saponins within different side streams was examined; in this context, sugar beet fiber contained the highest amounts of saponins for all investigated plant constituents and byproduct streams with a total amount of 12.7 g/kg. Finally, this is the first publication about the occurrence of individual saponins in sugar beets.

Impact of exogenous α-amylases on sugar formation in straight dough wheat bread

The use of bacterial or fungal α-amylases is common in wheat bread production to improve several quality-related parameters such as loaf volume, crust color or staling behavior. To study the impact of exogenous α-amylases on straight dough wheat bread, we quantitated mono-, di- and oligosaccharides and residual α-amylase activity in bread crumb during storage for up to 96 h. Discovery-driven proteomics of the five α-amylase preparations studied showed that only a few different amylases per preparation were responsible for the hydrolytic effect. Compared to the control, the supplementation with α-amylase from Bacillus amyloliquefaciens in wheat dough preparation led to major changes in the sugar composition of bread crumb during storage with the formation of oligosaccharides like maltopentaose, maltohexaose, maltoheptaose, and maltooctaose. A residual activity corresponding to 4.0% of the applied activity was determined in the breads prepared with α-amylase from B. amyloliquefaciens, but no residual activity was detected for any of the other fungal or bacterial α-amylases from Aspergillus oryzae or Thermoactinomyces vulgaris. Whether the detected residual activity is related to the characteristics of bread staling or bread crumb properties must be clarified in further studies.

A new phytoecdysteroid from the stem bark of Vitex cienkowskii

To investigate differences in the metabolome of the stem bark of Vitex cienkowskii harvested at three different locations and three different seasons, their extracts were analyzed by means of UPLC–ESI–IMS–TOF MSe. One marker metabolite was isolated and chemically characterized, which was identified as the new compound 20,24-dihydroxy,24-hydroxymethylecdysone (1). IMS showed two drift time species for 1 which could be used as new and additional characteristic compound parameters in compound identification to reduce dereplication and false positives.

The Role of Endogenous Enzymes during Malting of Barley and Wheat Varieties in the Mitigation of Styrene in Wheat Beer

Knowledge of the biochemical processes responsible for the release of phenolic acids (precursors of vinyl aromatics) during malting is important to find mitigation strategies for the toxicologically relevant styrene (formed from cinnamic acid) in wheat beer. Therefore, grain and malts of four barley and three wheat varieties were screened for the activities of various enzymes and the amounts of nonstarch polysaccharides (to which the phenolic acids are bound to a certain extent). During malting, a very strong degradation of β-glucan, synonymous to a depletion of the cell walls, was found, suggesting that a partial degradation of cell walls cannot have an effect on the release of phenolic acids. In barley malts, water-extractable arabinoxylan contents were between 0.59 and 0.79 g/100 g dm and in wheat malts between 0.93 and 1.51 g/100 g dm. Additionally, higher soluble ferulic acid contents in wheat wort compared to barley wort indicated that the degradation of nonstarch polysaccharides has an impact on the release of phenolic acids. For the feruloyl esterase, higher activities were found in malts of the barley varieties. However, this fact was not reflected by the free phenolic acid contents in those malts. Correlation coefficients between the protease activity and the feruloyl esterase, α- and β-amylase, and β-glucanase activities were proven to be insignificant, highlighting that the protease activity had no effect on the activities of these other enzymes.

Studies on the Impact of Malting and Mashing on the Free, Soluble Ester-Bound, and Insoluble Ester-Bound Forms of Desired and Undesired Phenolic Acids Aiming at Styrene Mitigation during Wheat Beer Brewing

Mitigation studies on styrene in wheat beer found no correlation between the free phenolic acid contents in the processing steps and the final concentrations of the toxicologically relevant styrene and the desired aroma-active vinyl aromatics in beer, which can be explained by the presence of phenolic acid releasing enzymes that are still active after kiln-drying and by the yeast's own feruloyl esterase activity. The present study contributed to a better understanding of the coherence between the free, soluble ester-bound, and insoluble ester-bound forms of cinnamic, p-coumaric, and ferulic acid during malting and mashing of barley and wheat varieties. Concentration differences in malt by factors of up to 1700 were found between the total cinnamic acid contents (an undesired precursor of the toxicologically relevant styrene) and the total contents of p-coumaric and ferulic acid (both desired precursors of the aroma-active compounds 4-vinylphenol and 2-methoxy-4-vinylphenol). In grain and malt, cinnamic acid occurred predominantly in a soluble form, whereas the desired precursors were mainly insoluble ester-bound. This had a direct effect on the transfer rates from malt into wort, which were found to be >100% for cinnamic acid, revealing that a complete transfer was accompanied by an additional biosynthesis, but only <8% for the desired phenolic acids. Interestingly, in the wort, cinnamic and p-coumaric acid contents were dominated by the free form, while ferulic acid was mostly still soluble ester-bound. Overall, the use of barley malts led to an introduction of cinnamic, p-coumaric, and ferulic acid into the wort in a ratio of 2:14:84, and the use of wheat malt in a ratio of 1:2:97.

A Phenotyping Platform to Characterize Healthy Individuals Across Four Stages of Life - The Enable Study

Introduction: Nutritional habits and requirements are changing over the lifespan, but the dynamics of nutritional issues and the diet-health relationship in the major stages of the human life cycle are not sufficiently understood. A human phenotyping research platform for nutrition studies was established to recruit and phenotype selected population groups across different stages of life. The project is the backbone of the highly interdisciplinary enable competence cluster of nutrition research aiming to identify dietary determinants of a healthy life throughout the lifespan and to develop healthier and tasty convenience foods with high consumer acceptance.

Methods: The phenotyping program included anthropometry, body composition analysis, assessment of energy metabolism, health and functional status, multisensory perception, metabolic phenotyping, lifestyle, sociodemography, chronobiology, and assessment of dietary intake including food preferences and aversions.

Results: In total, 503 healthy volunteers at four defined phases of life including 3–5-year old children (n = 44), young adults aged 18–25 years (n = 94), adults aged 40–65 years (“middle agers,” n = 205), and older adults aged 75–85 years (n = 160) were recruited and comprehensively phenotyped. Plasma, serum, buffy coat, urine, feces and saliva samples were collected and stored at −80°C. Significant differences in anthropometric and metabolic parameters between the four groups were found. A major finding was the decrease in fat-free mass and the concomitant increase in % body fat in both sexes across the adult lifespan.

Conclusions: The dataset will provide novel information on differences in diet-related parameters over the lifespan and is available for targeted analyses. We expect that this novel platform approach will have implications for the development of innovative food products tailored to promote healthy eating throughout life.

Trial registration: DRKS, DRKS00009797. Registered on 20 January 2016, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&_ID=DRKS00009797.

Characterization of Bitter and Astringent Off-Taste Compounds in Potato Fibers

Applying the sensomics approach, a combination of activity-guided fractionation and taste dilution analysis (TDA) followed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), ultrahigh-performance liquid chromatography time-of-flight mass spectrometry (UHPLC-TOF-MS), and one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy (1D/2D NMR) allowed the elucidation of key off-taste compounds in potato dietary fiber isolates. Previously already having been described as off-taste compounds in potato tubers, saponins α-chaconine and α-solanine were shown to be also major contributors to overall off-taste in potato fiber isolates. Moreover, fatty acids as well as fatty acid oxidation products, namely, E-9,10,13-trihydroxy-octadec-11-enoic acid as well as newly identified compounds hexadecyl(E/Z)-ferulate and octadecyl(E/Z)-ferulate, were shown to be key inducers to off-taste in the isolates, exhibiting taste recognition thresholds between 18 and 981 μmol/L. This paper demonstrates the isolation, structure determination, quantitation as well as sensory attributes of these key off-taste compounds.

A novel electrochemical anodization cell for the synthesis of mesoporous silicon

A novel design of an electrochemical anodization cell dedicated to the synthesis of mesoporous, single-crystalline silicon is presented. First and foremost, the design principle follows user safety since electrochemical etching of silicon requires highly hazardous electrolytes based on hydrofluoric (HF) acid. The novel cell design allows for safe electrolyte handling prior, during, and post-etching. A peristaltic pump with HF-resistant fluoroelastomer tubing transfers electrolytes between dedicated reservoirs and the anodization cell. Due to the flexibility of the cell operation, different processing conditions can be realized providing a large parameter range for the attainable sample thickness, its porosity, and the mean pore size. Rapid etching on the order of several minutes to synthesize micrometer-thick porous silicon epilayers on bulk silicon is possible as well as long-time etching with continuous, controlled electrolyte flow for several days to prepare up to 1000 μm thick self-supporting porous silicon membranes. A highly adaptable, LabVIEW^™-based control software allows for user-defined etching profiles.

Molecularization of Foam-Active Saponins from Sugar Beet Side Streams (Beta vulgaris ssp. vulgaris var. altissima)

This work focuses on the isolation and characterization of saponins with a very low bitter intensity originating from sustainable plant materials, in particular the sugar beet pulp by-product stream. Via a concise foam activity screening of saponin-containing materials, which gives indications for their emulsifying ability, sugar beet root extract was selected and examined for low bitter saponins by means of activity guided fractionation. Individual saponins were isolated from sugar beet pulp, which was identified as the most convenient sugar beet saponin source. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy led to the unequivocal identification of the major, slightly bitter tasting compounds as a series of eight saponins. The complete assignment of ¹H and ¹³C NMR signals for several saponins was carried out for the first time. A small-scale foam activity assay was established and applied to a broad spectrum of the isolated and commercially available saponins. Additionally, orosensory recognition thresholds were determined. Not only high recognition thresholds were determined (thresholds >1000 μmol/L) but also fundamental information about the foaming behavior of mono- and bidesmosidic saponins was collected. The obtained results are relevant to the utilization of saponins from other plant materials or by-product streams and for the use of sugar beet saponins as food additives.

In Silico Investigation of Bitter Hop-Derived Compounds and Their Cognate Bitter Taste Receptors

The typical bitter taste of beer is caused by adding hops (Humulus lupulus L.) during the wort boiling process. The bitter taste of hop-derived compounds was found to be mediated by three bitter taste receptors: TAS2R1, TAS2R14, and TAS2R40. In this work, structural bioinformatics analyses were used to characterize the binding modes of trans-isocohumulone, trans-isohumulone, trans-isoadhumulone, cis-isocohumulone, cis-isohumulone, cis-isoadhumulone, cohumulone, humulone, adhumulone, and 8-prenylnaringenin into the orthosteric binding site of their cognate receptors. A conserved asparagine in transmembrane 3 was found to be essential for the recognition of hop-derived compounds, whereas the surrounding residues in the binding site of the three receptors encode the ligand specificity. Hop-derived compounds are renowned bioactive molecules and are considered as potential hit molecules for drug discovery to treat metabolic diseases. A chemoinformatics analysis revealed that hop-derived compounds cluster in a different region of the chemical space compared to known bitter food-derived compounds, pinpointing hop-derived compounds as a very peculiar class of bitter compounds.

Mapping Taste-Relevant Food Peptidomes by Means of Sequential Window Acquisition of All Theoretical Fragment Ion-Mass Spectrometry

During the last few years, key taste-active compounds have been isolated and identified by means of a combination of a time- and lab-consuming successive fractionation and sensory characterization. Because the peptidome of fermented, protein-rich food is very complex, new strategies are necessary to accelerate the identification of taste-active peptides. In this study, two advanced mass spectrometric approaches were developed to comprehensively map the bitter tasting peptidome of fermented foods by data-independent acquisition (DIA) using sequential window acquisition of all theoretical fragment ion-mass spectrometry (SWATH-MS) and an in silico-assisted triple quadrupole (QQQ)-based targeted proteomics approach, separately. Application of both techniques on two fresh cheese samples as well as on crude medium-pressure liquid chromatography fractions exhibiting intense bitter taste, followed by filtering the hydrophobic target peptides (Q value of ≥1200 cal/mol) showing a signal-to-noise ratio of ≥10 and a fold change of ≥3 when comparing the less bitter to the more bitter cheese sample, revealed the candidate bitter peptides, which were then validated by means of synthetic reference peptides and human sensory evaluation. The bitter peptides were then quantitated in the fresh cheese samples as well as in a series of dairy products by means of QQQ-MS and SWATH-MS, separately. Although the QQQ-MS method showed 2-80-fold lower limits of quantitation (LOQ), the SWATH-MS method could be shown for the first time to enable the comprehensive quantitation of all sensorially relevant key bitter peptides with LOQs far below the bitter taste recognition concentration of each peptide.

Molecularization of Bitter Off-Taste Compounds in Pea-Protein Isolates (Pisum sativum L.)

Activity-guided fractionations, combined with taste dilution analyses (TDA), were performed to locate the key compounds contributing to the bitter off-taste of pea-protein isolates (Pisum sativum L.). Purification of the compounds perceived with the highest sensory impact, followed by 1D/2D-NMR, (LC-)MS/MS, LC-TOF-MS, and MSE experiments, led to the identification of 14 lipids and lipid oxidation products, namely, 9,10,13-trihydroxyoctadec-12-enoic acid, 9,12,13-trihydroxyoctadec-10-enoic acid, 9,10,11-trihydroxyoctadec-12-enoic, 11,12,13-trihydroxyoctadec-9-enoic acid, (10E,12E)-9-hydroxyoctadeca-10,12-dienoic acid, (9Z,11E)-13-hydroxyoctadeca-9,11-dienoic acid, (9E,11E)-13-hydroxyoctadeca-9,11-dienoic acid, 1-linoleoyl glycerol, α-linolenic acid, 2-hydroxypalmitic acid, 2-hydroxyoleic acid, linoleic acid, (9Z,11E)-13-oxooctadeca-9,11-dienoic acid, and octacosa-6,9,19,22-tetraen. Herein, we present the isolation, structure determination, and sensory activity of these molecules. Depending on their structure, the isolated compounds showed human bitter recognition thresholds between 0.06 and 0.99 mmol/L in water.

Investigation of Kokumi Substances and Bacteria in Thai Fermented Freshwater Fish (Pla-ra)

A 16S rRNA next-generation sequencing technique was applied to investigate the microbial diversity and liquid chromatography-tandem mass spectrometry was used to identify glutamyl peptide profiles of 10 Thai fermented freshwater fish (Pla-ra) samples. A total of 12 genera of bacteria were able to be detected, with Tetragenococcus spp., Staphylococcus spp., and Lactobacillus spp. dominating. Of the 18 glutamyl peptides analyzed, 17 were found, even though the amounts detected were lower than the taste threshold. Despite this, an increase in mouthfulness sensation, reflecting kokumi activity, was clearly identified in most of the samples, which might be because of a synergistic effect of different sub-threshold compounds present in the samples. In principle component analysis, the relationship between microorganisms and glutamyl peptide generation was observed, especially between Tetragenococcus spp. and Lentibacillus spp. and the generation of γ-Glu-Val-Gly. Correlations between microbial diversity and the generation of taste enhancers were identified in this study.

Characterization of Bitter-Tasting Oxylipins in Poppy Seeds (Papaver somniferum L.)

Activity-guided fractionation of poppy seed (Papaver somniferum L.) extracts and analysis of fatty acid oxidation model experiments, followed by liquid chromatography time-of-flight mass spectrometry, tandem mass spectrometry, and one-/two-dimensional nuclear magnetic resonance experiments, revealed the chemical structures of five bitter-tasting fatty acids (1-5), three monoglycerides (6-8), six C₁₈-lipidoxidation products (9-14), and four lipid oxidation degradation products (15 and 17-19) as well as two previously unreported monoglyceride oxidation degradation products, namely, 9-(2',3'-dihydroxypropyloxy)-9-oxononaic acid (1-azeloyl-rac-glycerol, 16) and 1-(2',3'-dihydroxypropyl)-8-(5″-oxo-2″,5″-dihydrofruan-2″-yl)-octonoate (1-ODFO-rac-glycerol, 20). Sensory studies exhibited low bitter taste threshold concentrations between 0.08 and 0.29 mmol/L, particularly for the higher oxidated C₁₈-fatty acids trihydroxyoctadecenoic acid (THOE, 12), 12,13-dihydroxy-9-oxo-10-octadecenoic acid (12,13-diOH-9-oxo, 13), and 9,10-dihydroxy-13-oxo-11-octadecenoic acid (9,10-diOH-13-oxo, 14) as well as for the lipidoxidation degradation products 4-hydroxy-2-noneic acid (4-HNA, 17), 4-hydroxy-2-docecendienoic acid (HDdiA, 18), and 8-(5'-oxo-2',5'-dihydrofuran-2'-yl)-octanoic acid (ODFO, 20).

Highlights of the 12th Wartburg Symposium on Flavor Chemistry & Biology

The 12th Wartburg Symposium on Flavor Chemistry & Biology was held at the hotel "Auf der Wartburg" in Eisenach, Germany, from May 21 to 24, 2019. It offered a unique venue for global exchange on cutting-edge research progress in chemistry and biology of odor and taste. The focus areas were (1) chemosensory perception and signal processing, (2) flavor systems: molecular decoding, interactions, and perception, (3) new computational approaches in flavor chemistry, (4) functional flavor genomics and biotechnology, (5) food-borne bioactives: molecular decoding, interactions, and perception, and (6) next-generation technologies in flavor molecule and precursor discovery. Selected from more than 250 applicants, 160 distinguished scientists and early career researches from industry and academia from 24 countries and 4 continents participated in this inspiring and multidisciplinary event. This special issue comprises a selection of 20 papers from oral presentations and poster contributions and is prefaced by this introduction paper.

[Laparoscopic versus open gastrectomy for advanced gastric cancer : Operative and postoperative results]

BACKGROUND

Minimally invasive gastrectomy is increasingly becoming established worldwide as an alternative to open gastrectomy (OG); however, the majority of available articles in the literature refer to Asian populations and early stages of gastric cancer. This makes an international comparison difficult due to a discrepancy in patient populations and tumor biology as well as Asian and western treatment approaches. Little is known, therefore, whether laparoscopic gastrectomy (LG) can be performed in advanced cancer, in particular with respect to laparoscopic D2 lymphadenectomy, with sufficient radicality and safety in this country.

MATERIAL AND METHODS

All gastrectomies performed for the treatment of advanced gastric cancer with clinical UICC stages 2 and 3 between 2005 and 2017 were analyzed. A case match by age, gender and UICC stage was performed to compare the operative and early postoperative results of LG and OG.

RESULTS

A total of 243 patients with advanced gastric cancer were analyzed. Of these 81 patients (33.3%) underwent LG. The operative time for LG was around 74 min longer (279.2 min vs. 353.4 min, OG vs. LG; p < 0.001), the hospital stay after LG was around 4 days shorter (22.9 days vs. 18.4 days, OG vs. LG; p < 0.001). Significantly more lymph nodes were resected by LG (24.1 lymph nodes vs. 28.8 lymph nodes, OG vs. LG; p < 0.001). In terms of morbidity and mortality there were no differences between the groups.

CONCLUSION

The present study showed that minimally invasive gastrectomy can be performed safely and with comparable histopathological results to open surgery, even in advanced gastric cancer in western populations; however, larger case series and evidence from high-quality studies are urgently needed especially to compare short-term and long-term survival.

Quantitation and Taste Contribution of Sensory Active Molecules in Oat (Avena sativa L.)

A total of 59 taste-active molecules were quantitated and then rated for their individual taste impact on the basis of dose-over-threshold factors in oat flour (Avena sativa L.). A sensitive high-performance liquid chromatography-tandem mass spectrometry method was developed to quantitate bitter-tasting steroidal and furostanol saponins as well as avenanthramides. Four monoglycerides, five free fatty acids and four saponins were confirmed for the first time to be major contributors to the bitter off-taste of oats, among them 1-linoleoyl-rac-glycerol, 1-stearoyl-rac-glycerol, 1-oleoyl-rac-glycerol, 1-palmitoyl-rac-glycerol, linoleic acid, linolenic acid, oleic acid, palmitic acid, and stearic acid as well as avenacosides A and B and the recently identified furostanosides 3-(O-α-l-rhamnopyranosyl(1→2)-[β-d-glucopyranosyl(1→3)-β-d-glucopyranosyl(1→4)]-β-d-glucopyranosid)-26-O-β-d-glucopyranosyl-(25R)-furost-5-ene-3β,22,26-triol and 3-(O-α-l-rhamnopyranosyl(1→2)-[β-d-glucopyranosyl(1→4)]-β-d-glucopyranosid)-26-O-β-d-glucopyranosyl-(25R)-furost-5-ene-3β,22,26-triol. By means of a stable isotope dilution assay, quantitated avenanthramides 2c, 2p, 2f, 1p, 1c, 1f, and 3f were found in concentrations below their thresholds and, therefore, did not contribute to the bitter sensation of the tested oat flour.

Integrated microbiota and metabolite profiles link Crohn's disease to sulfur metabolism

Gut microbial and metabolite alterations have been linked to the pathogenesis of inflammatory bowel diseases. Here we perform a multi-omics microbiome and metabolite analysis of a longitudinal cohort of Crohn's disease patients undergoing autologous hematopoietic stem cell transplantation, and investigational therapy that induces drug free remission in a subset of patients. Via comparison of patients who responded and maintained remission, responded but experienced disease relapse and patients who did not respond to therapy, we identify shared functional signatures that correlate with disease activity despite the variability of gut microbiota profiles at taxonomic level. These signatures reflect the disease state when transferred to gnotobiotic mice. Taken together, the integration of microbiome and metabolite profiles from human cohort and mice improves the predictive modelling of disease outcome, and allows the identification of a network of bacteria-metabolite interactions involving sulfur metabolism as a key mechanism linked to disease activity in Crohn's disease.

Hop-induced formation of ethyl esters in dry-hopped beer

Abstract

Fruity smelling esters play an important role for the aroma of hops and beer and they have been characterized as key aroma compounds in different hop varieties. Studies on the transfer of hop-derived compounds into beer during dry-hopping showed calculated transfer rates of different ethyl esters far above 100%, leading to the assumption that these esters must be newly formed. To investigate this formation, dry-hopping was imitated in water to eliminate the influence of the beer matrix on the formation of these odorants. Thereby, the formation of ethyl esters of 2-methylbutanoic acid, 3-methylbutanoic acid, and methylpropanoic acid, induced by the addition of hops, was shown. Different approaches inhibiting enzyme activities and experiments with different hop extracts might lead to the assumption that enzymes are involved in the formation of these esters, beside possible transesterification.

Graphical abstract

Dry-Hopping to Modify the Aroma of Alcohol-Free Beer on a Molecular Level-Loss and Transfer of Odor-Active Compounds

There are mainly two options for the dealcoholization of beer: evaporation of ethanol by heat treatment, whereby desired aroma-active compounds are also removed, and stopped fermentation that leads to beers still containing high amounts of unfermented sugar in parallel with lower amounts of aroma-active fermentation products. Thus, dry-hopping could be an opportunity to compensate for these aroma deficiencies. Therefore, following the sensomics approach, odorants were characterized in dry-hopped (Hallertauer Mandarina Bavaria, Hallertauer Cascade, or Hallertauer Mittelfrüh) top- and bottom-fermented alcohol-free beers either after thermal dealcoholization or stopped fermentation. Twenty-three odorants were quantitated via stable isotope dilution analysis, and odor activity values (OAVs; ratio of concentration to odor threshold) were calculated. Thermally dealcoholized samples showed high losses (up to 100%) of key odorants like 3-methyl-1-butanol or 3-methylbutyl acetate. During stopped fermentation, aroma compounds like ethyl butanoate or 2-phenylethanol were formed in relevant concentrations, leading to OAVs ≥ 1, but the amounts were significantly lower compared to beers with normal alcohol contents. For hop-derived odorants (linalool, geraniol, myrcene, and esters), transfer rates between 20 and 90% were found, leading to OAVs ≥ 1 in beer. Furthermore, hop addition apparently induced the formation of ethyl esters of hop-derived monocarboxylic acids.

Numerous Compounds Orchestrate Coffee's Bitterness

Coffee is one of the most consumed hot beverages worldwide and is highly regarded because of its stimulating effect despite having a pronounced bitterness. Even though numerous bitter ingredients have been identified, the detailed molecular basis for coffee's bitterness is not well understood except for caffeine, which activates five human bitter taste receptors. We elucidated the contribution of other bitter coffee constituents in addition to caffeine with functional calcium imaging experiments using mammalian cells expressing the cDNAs of human bitter taste receptors, sensory experiments, and in silico modeling approaches. We identified two human bitter taste receptors, TAS2R43 and TAS2R46, that responded to the bitter substance mozambioside with much higher sensitivity than to caffeine. Further, the structurally related bitter substances bengalensol, cafestol, and kahweol also activated the same pair of bitter taste receptors much more potently than the prototypical coffee bitter substance caffeine. However, for kahweol, a potent but weak activator of TAS2R43 and TAS2R46, we observed an inhibitory effect when simultaneously applied together with mozambioside to TAS2R43 expressing cells. Molecular modeling experiments showed overlapping binding sites in the receptor's ligand binding cavity that suggest that the partial agonist kahweol might be useful to reduce the overall bitterness of coffee-containing beverages. Taken together, we found that the bitterness of coffee is determined by a complex interaction of multiple bitter compounds with several human bitter taste receptors.

Quantitative Determination of Thiamine-Derived Taste Enhancers in Aqueous Model Systems, Natural Deep Eutectic Solvents, and Thermally Processed Foods

To obtain high-kokumi-active building blocks, which can be used to produce savory process flavors, it is essential to obtain a better understanding on the formation rate of kokumi-active compounds, such as 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one or 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine. The present work showed quantitative studies in several model reaction systems on the recently discovered kokumi-active thiamine derivates. It was possible to show that the thiamine conversion in aqueous model reactions could be directed toward the taste-modulating compounds by adjusting the pH value (6.5), the heating time (120 min), and the heating temperature (120 °C). With the development of a new natural deep eutectic solvents (NADES) system consisting of thiamine, cysteine, ribose, and sodium hydroxide, it was possible to obtain high yields of the targeted taste-modulating analytes, such as 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one and 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine. Furthermore, the current study showed that kokumi-active thiamine derivates, such as S-((4-amino-2-methylpyrimidin-5-yl)methyl)-l-cysteine, 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one, 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine, and 5-(((furan-2-ylmethyl)thio)methyl)-2-methylpyrimidin-4-amine, can be classified as natural "food-borne" taste enhancers and occur in thiamine-rich, thermally treated foodstuff.

Ion-Mobility-Based Liquid Chromatography-Mass Spectrometry Quantitation of Taste-Enhancing Octadecadien-12-ynoic Acids in Mushrooms

For the accurate quantitation of kokumi-enhancing and bitter-tasting octadecadien-12-ynoic and octadecadienoic acids in chanterelles (Cantharellus cibarius Fr.), a sensitive ultra-high-performance liquid chromatography-differential ion mobility spectrometry-tandem mass spectrometry method was developed. On the basis of these quantitative data and the taste thresholds, dose-over-threshold factors were calculated to determine the contribution of these sensometabolites to the kokumi and bitter taste of chanterelles; e.g., 14,15-dehydrocrepenynic acid (3) and (9Z,15E)-14-oxooctadeca-9,15-dien-12-ynoic acid (7) were identified as key kokumi substances in raw chanterelles. Quantitative profiling of these compounds in various mushroom species demonstrated a unique accumulation of octadecadien-12-ynoic acids in Cantharellus. Furthermore, storage experiments highlighted dynamic processes, including the biosynthesis of these substances as a result of lipid peroxidation mechanisms.

MG-HCr, the Methylglyoxal-Derived Hydroimidazolone of Creatine, a Biomarker for the Dietary Intake of Animal Source Food

In the course of the Maillard reaction in vivo or in food, creatine reacts with the 1,2-dicarbonyl compound methylglyoxal to N-(4-methyl-5-oxo-1-imidazolin-2-yl)sarcosine (MG-HCr). We studied whether the urinary excretion of MG-HCr is affected by its intake with meat or by the intake of creatine and subsequent in vivo formation of MG-HCr. Therefore, 24 h urine of 30 subjects with different dietary habits was analyzed with HPLC-MS/MS. The daily MG-HCr excretion via urine varied between omnivores (0.39-9.67 μmol/day, n = 24), vegetarians (0.18-0.97 μmol/day, n = 19), and vegans (0.10-0.27 μmol/day, n = 8). An intervention study with 18 subjects demonstrated the bioavailability of MG-HCr (ca. 54%) from 200 g of heated meat and its quick excretion with urine. A creatine intervention of 0.44 g did not increase MG-HCr excretion. Thus, the differences in MG-HCr excretion between different diets are mainly caused by the dietary uptake of MG-HCr. We additionally found MG-HCr in milk and egg products, where it is formed during heat treatment. This partly explains differences in MG-HCr excretion of vegetarians and vegans. Hence, MG-HCr in urine is a short-term marker for the intake of heat-processed animal source food.

Terahertz-frequency dielectric anisotropy in three-dimensional polymethacrylates fabricated by stereolithography

The anisotropic optical dielectric functions of slanted columnar layers fabricated using polymethacrylate based stereolithography are reported for the terahertz-frequency domain using generalized spectroscopic ellipsometry. The slanted columnar layers are composed of spatially coherent columnar structures with a diameter of 100 µm and a length of 700 µm that are tilted by 45° with respect to the surface normal of the substrates. A simple biaxial (orthorhombic) layer homogenization approach is used to analyze the terahertz ellipsometric data obtained at three different sample azimuthal orientations. The permittivity along the major polarizability directions varies by almost 25%. Our results demonstrate that stereolithography allows tailoring of the polarizability and anisotropy of the host material, and provides a flexible alternative metamaterials fabrication method for the terahertz spectral range.

Simple Generation of Suspensible Secondary Microplastic Reference Particles via Ultrasound Treatment

In the environment the weathering of plastic debris is one of the main sources of secondary microplastic (MP). It is distinct from primary MP, as it is not intentionally engineered, and presents a highly heterogeneous analyte composed of plastic fragments in the size range of 1 μm-1 mm. To detect secondary MP, methods must be developed with appropriate reference materials. These should share the characteristics of environmental MP which are a broad size range, multitude of shapes (fragments, spheres, films, fibers), suspensibility in water, and modified particle surfaces through aging (additional OH, C=O, and COOH). To produce such a material, we bring forward a rapid sonication-based fragmentation method for polystyrene (PS), polyethylene terephthalate (PET), and polylactic acid (PLA), which yields up to 105/15 mL dispersible, high purity MP particles in aqueous media. To satisfy the claim of a reference material, the key properties-composition and size distribution to ensure the homogeneity of the samples, as well as shape, suspensibility, and aging -were analyzed in replicates (N = 3) to ensure a robust production procedure. The procedure yields fragments in the range of 100 nm-1 mm (<20 μm, 54.5 ± 11.3% of all particles). Fragments in the size range 10 μm-1 mm were quantitatively characterized via Raman microspectroscopy (particles = 500-1,000) and reflectance micro Fourier transform infrared analysis (particles = 10). Smaller particles 100 nm-20 μm were qualitatively characterized by scanning electron microcopy (SEM). The optical microscopy and SEM analysis showed that fragments are the predominant shape for all polymers, but fibers are also present. Furthermore, the suspensibility and sedimentation in pure MilliQ water was investigated using ultraviolet-visible spectroscopy and revealed that the produced fragments sediment according to their density and that the attachment to glass is avoided. Finally, a comparison of the infrared spectra from the fragments produced through sonication and naturally aged MP shows the addition of polar groups to the surface of the particles in the OH, C=O, and COOH region, making these particles suitable reference materials for secondary MP.

Key Odorants in Japanese Roasted Barley Tea (Mugi-Cha)-Differences between Roasted Barley Tea Prepared from Naked Barley and Roasted Barley Tea Prepared from Hulled Barley

The volatiles isolated by solvent extraction and solvent-assisted flavor evaporation (SAFE) from roasted barley tea, prepared from either hulled barley or naked barley, were subjected to a comparative aroma extract dilution analysis, which resulted in 27 odor-active compounds with flavor dilution factors (FD factors) of 64-1024. An additional 5 odorants were detected by static headspace analysis. Quantitation of these 32 compounds revealed 22 and 23 odorants in the naked barley tea and in the hulled barley tea, respectively, that exceeded their odor-threshold values. On the basis of these data, the aromas of both barley tea variants were successfully reconstituted with reference compounds. The calculation of odor-activity values (OAVs = concentration/odor-threshold value) and omission tests suggested 2-methoxyphenol (OAVs 69 and 160) and trans-isoeugenol (OAVs 1.4 and 31) as key compounds responsible for the stronger smoky note in the hulled barley tea. Further important odorants in the naked and hulled barley teas included 2-acetylpyrazine (OAVs 23 and 16), 2-acetyl-1-pyrroline (OAVs 19 and 16), and 3-methylbutanal (OAVs 12 and 15).

Targeted metabolomics of pellicle and saliva in children with different caries activity

Pellicle is the initial proteinaceous layer that is formed almost instantaneously on all solid surfaces in the oral cavity. It is of essential relevance for any interactions and metabolism on the tooth surface. Up to now, there is no information on the metabolome of this structure. Accordingly, the present study aims to characterise the metabolomic profile of in-situ pellicle in children with different caries activity for the first time in comparison to saliva. Small molecules such as carbohydrates, amino acids, organic acids, and fatty acids, putatively involved in the formation of caries were quantified using mass spectrometry (MS)-based techniques, such as (stable isotope dilution analysis)-ultra-performance liquid chromatography-tandem MS and gas chromatography/electron ionisation-MS. Pellicle and corresponding saliva samples were collected from caries-active, caries-free and caries-rehabilitated 4- to 6-year-old children. The most abundant analytes in pellicle were acetic acid (1.2-10.5 nmol/cm2), propionic acid (0.1-8.5 nmol/cm2), glycine (0.7-3.5 nmol/cm2), serine (0.08-2.3 nmol/cm2), galactose (galactose + mannose; 0.035-0.078 nmol/cm2), lactose (0.002-0.086 nmol/cm2), glucose (0.018-0.953 nmol/cm2), palmitic acid (0.26-2.03 nmol/cm2), and stearic acid (0.34-1.81 nmol/cm2). Significant differences depending on caries activity were detected neither in saliva nor in the corresponding pellicle samples.

Investigations into the Structure-Function Relationship of the Naturally-Derived Surfactant Glycyrrhizin: Emulsion Stability

This study describes the emulsion stabilizing properties of the licorice root (Glycyrrhiza glabra L.) derived saponin glycyrrhizin and its corresponding aglycone 18β-glycyrrhetinic acid to further increase the understanding between structure and functional behavior. For this, we prepared 10% oil-in-water emulsions and investigated the emulsion stabilizing properties regarding environmental stresses including extreme pH, ionic strength, and temperature. Glycyrrhizin and its aglycone formed nano-sized emulsion droplets at neutral pH that were stable across a broad range of pH-values (pH 5–9), ionic strength (0–200 mM NaCl), and temperature (up to 60 °C). In contrast, emulsions were unstable at low pH (pH <5), as well as high ionic strength (>200 mM NaCl, >5 mM CaCl2) and temperature as well as after a freeze-thaw cycle. Thereby, the observed instability was mainly attributed to the reduction of electrostatic forces caused by the protonation of free carboxylic acid groups at low pH, screening of electrostatic forces at high ionic strengths, and thin interfaces causing coalescence during a freeze-thaw cycle. Overall, both molecules yielded remarkably stable emulsions at very low molecule-to-oil ratios, and therefore our results are relevant for ‘all-natural’ emulsion-based foods and beverages, as well as pharmaceutical and cosmetic products.

Novel Taste-Enhancing 4-Amino-2-methyl-5-heteroalkypyrimidines Formed from Thiamine by Maillard-Type Reactions

Increasing the thiamine concentration in a respective process flavor yields a product with a significant higher kokumi activity. S-plot analysis of the mass spectrometric data revealed beside thiamine itself, 4-methyl-5-thiazoleethanol, (S)-((4-amino-2-methylpyrimidin-5-yl)methyl)-l-cysteine, N-((4-amino-2-methylpyrimidin-5-yl)methyl)formamide, 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one, and 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine as marker molecules for a process flavor with higher thiamine concentration. Sensory-based targeted isolation revealed that (S)-((4-amino-2-methylpyrimidin-5-yl)methyl)-l-cysteine, 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one, and 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine showed an influence on the kokumi taste activity with taste threshold concentrations between 35 and 120 μmol/L. An adapted mass spectrometric-based carbon module labeling experiment as well as quantitative studies clearly demonstrated thiamine as the only precursor and an intermolecular formation pathway for the compounds (S)-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one and 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine. On the basis of the knowledge that several thiamine derivatives showed taste-modulating activity, selected thiamine-based binary model reactions and synthesis were carried out. This resulted in the isolation of further thiamine-derived taste modulators like (S)-((4-amino-2-methylpyrimidin-5-yl)methyl)-l-cysteinylglycine, (S)-3-((((4-amino-2-methylpyrimidin-5-yl)methyl)thio)methyl)piperazine-2,5-dione, 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)pentan-2-one, 5-(((furan-2-ylmethyl)thio)methyl)-2-methylpyrimidin-4-amine, and (4-amino-2-methylpyrimidin-5-yl)methanethiol, 2-methyl-5-((methylthio)methyl)pyrimidin-4-amine with taste thresholds ranging from 35 to 880 μmol/L.

Characterization of Key Aroma Compounds in Pellets of Different Hop Varieties (Humulus lupulus L.) by Means of the Sensomics Approach

The use of hops in beer brewing is mainly based on its content of bitter acids and aroma compounds. Due to the loss of volatile odorants during wort boiling, the so-called dry hopping is a possibility to intensify the hoppy aroma in the final beer. To clarify the potential of different hop varieties for aroma modulation of beer via dry hopping, key aroma compounds of three different hop varieties were characterized using the sensomics approach. Aroma extract dilution analysis revealed 41 aroma-active compounds, of which 39 were identified via gas chromatography-olfactometry and gas chromatography-mass spectrometry. The highest flavor dilution factor was determined for myrcene with a geranium-like odor. Fourteen substances were quantitated by stable isotope dilution analysis and further two odorants via the internal standard method; all of them revealed odor activity values (OAVs; ratio of concentration to odor threshold) ≥1. Linalool, 3-methylbutanoic acid, myrcene, and dimethyl trisulfide showed the highest OAVs (>1000) in all analyzed hop varieties. For validation of the analytical data, reconstitution models were prepared by adding all quantitated aroma compounds with OAVs ≥ 1 in their naturally occurring concentrations to cellulose as matrix. All three recombinates showed a very high similarity to the aroma profile of the respective hop sample, confirming the correct identification and quantitation of all key aroma compounds.

CIGuide: in situ augmented reality laser guidance

PURPOSE : A robotic intraoperative laser guidance system with hybrid optic-magnetic tracking for skull base surgery is presented. It provides in situ augmented reality guidance for microscopic interventions at the lateral skull base with minimal mental and workload overhead on surgeons working without a monitor and dedicated pointing tools. METHODS : Three components were developed: a registration tool (Rhinospider), a hybrid magneto-optic-tracked robotic feedback control scheme and a modified robotic end-effector. Rhinospider optimizes registration of patient and preoperative CT data by excluding user errors in fiducial localization with magnetic tracking. The hybrid controller uses an integrated microscope HD camera for robotic control with a guidance beam shining on a dual plate setup avoiding magnetic field distortions. A robotic needle insertion platform (iSYS Medizintechnik GmbH, Austria) was modified to position a laser beam with high precision in a surgical scene compatible to microscopic surgery. RESULTS : System accuracy was evaluated quantitatively at various target positions on a phantom. The accuracy found is 1.2 mm ± 0.5 mm. Errors are primarily due to magnetic tracking. This application accuracy seems suitable for most surgical procedures in the lateral skull base. The system was evaluated quantitatively during a mastoidectomy of an anatomic head specimen and was judged useful by the surgeon. CONCLUSION : A hybrid robotic laser guidance system with direct visual feedback is proposed for navigated drilling and intraoperative structure localization. The system provides visual cues directly on/in the patient anatomy, reducing the standard limitations of AR visualizations like depth perception. The custom- built end-effector for the iSYS robot is transparent to using surgical microscopes and compatible with magnetic tracking. The cadaver experiment showed that guidance was accurate and that the end-effector is unobtrusive. This laser guidance has potential to aid the surgeon in finding the optimal mastoidectomy trajectory in more difficult interventions.