Odorant Screening Research Articles

Odour-active compounds in liquid malt extracts for the baking industry

An odorant screening by gas chromatography–olfactometry (GC–O) and a crude aroma extract dilution analysis (AEDA) applied to the volatiles isolated from a light and a dark liquid malt extract (LME) by solvent extraction and solvent-assisted flavour evaporation (SAFE) identified 28 odorants. Fifteen major odorants were subsequently quantitated and odour activity values (OAVs) were calculated as ratio of the concentration to the respective odour threshold value (OTV). Important odorants in the light LME included 3-(methylsulfanyl)propanal (OAV 1500), (E)-β-damascenone (OAV 430), and 4-ethenyl-2-methoxyphenol (OAV 91). In the dark LME, sotolon (OAV 780), 3-(methylsulfanyl)propanal (OAV 550), (E)-β-damascenone (OAV 410), acetic acid (OAV 160), and maltol (OAV 120) were of particular importance. To get an insight into the changes during malt extract production, the quantitations were extended to the malt used as the starting material for both LMEs. Addition of a minor amount of water to malt before volatile extraction was shown to be effective to cover the free as well as the bound malt odorants. Results showed that some LME odorants originated from the starting material whereas others were formed during processing. Important process-induced LME odorants included (E)-β-damascenone and 4-ethenyl-2-methoxyphenol in the light LME as well as maltol, sotolon, (E)-β-damascenone, and 2-methoxyphenol in the dark LME. In summary, the odorant formation during LME production was shown to be more important than the transfer of odorants from the malt.

Gas Chromatography Olfactometry (GC-O) for the (Semi)Quantitative Screening of Wine Aroma.

This review discusses the different approaches developed by researchers in the last 40 years for the qualitative and semi-quantitative screening of odorants, with special emphasis in wine aroma profiling. In the first part, the aims and possibilities of Gas chromatography-olfactometry (GC-O) as odour-screening and aroma profiling technique are discussed. The critical difference between approaches is whether the ranking of odorants is carried out on an extract containing all the odorants present in the product, or on an extract representative of the odorants contained in the vapour phases that cause the odour and flavour. While the second alternative is more direct and can be more efficient, it requires a good understanding of the factors affecting orthonasal olfaction, handling volatiles (purging, trapping, eluting, and separating) and about the sensory assessment of GC effluents. The review also includes an updated list compiling all the odorants detected in wine by GC-O, including retention indexes and odour descriptions with a general guideline for the identification of odorants.

Spheroid Culture of Mammalian Olfactory Receptor Neurons: Potential Applications for a Bioelectronic Nose.

The olfactory system can detect many odorants with high sensitivity and selectivity based on the expression of nearly a thousand types of olfactory receptors (ORs) in olfactory receptor neurons (ORNs). These ORs have a dynamic odorant detection range and contribute to signal encoding processes in the olfactory bulb (OB). To harness the capabilities of the olfactory system and develop a biomimetic sensor, stable culture and maintenance of ORNs are required. However, in vitro monolayer culture models have several key limitations: i) short available period of cultured neurons, ii) low cultural efficiency, and iii) long-term storage challenges. This study aims to develop a technique: i) to support the spheroid culture of primary ORN precursors facilitating stable maintenance and long-term storage, and ii) to demonstrate the viability of ORN spheroid culture in developing an olfactory system mimetic bioelectronic nose. Recombinant protein (REP; TGPG[VGRGD(VGVPG)6]20WPC) was used to form the ORN spheroids. Spheroid formation enabled preservation of primary cultured ORNs without a significant decrease in viability or the expression of stemness markers for ten days. Physiological characteristics of the ORNs were verified by monitoring intracellular calcium concentration upon odorant mixture stimulation; response upon odorant stimulation were observed at least for ten days in these cultivated ORNs differentiated from spheroids. Coupling ORNs with multi electrode array (MEA) enabled the detection and discrimination of odorants by analyzing the electrical signal patterns generated following odorant stimulation. Taken together, the ORN spheroid culture process is a promising technique for the development of a bioelectronic nose and high-throughput odorant screening device.

Investigations on the Impact of the Special Flavor Hop Variety Huell Melon on the Odor-Active Compounds in Late Hopped and Dry Hopped Beers.

Bottom-fermented and top-fermented beers, both either late or dry hopped with Huell Melon hops, and respective reference beers without late or dry hopping were subjected to a comparative odorant screening by aroma extract dilution analyses. On the basis of differences in the FD factors, 14 odorants were identified as hop-derived. Among them were ethyl 2-methylpropanoate, methyl 2-methylbutanoate, ethyl 2-methylbutanoate, propyl 2-methylbutanoate, myrcene, linalool, and geraniol. Differences between late hopped, dry hopped, and reference beers were substantiated by quantitation. Results showed minimal transfer of myrcene from hops into beer. Moderate transfer was observed for propyl 2-methylbutanoate, geraniol, and linalool. Process-induced changes of ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, and methyl 2-methylbutanoate were beyond a direct transfer from hops into beer, suggesting a formation from the corresponding hop-derived carboxylic acids by yeast. Spiking experiments revealed that linalool and propyl 2-methylbutanoate contributed particularly to the characteristic aroma of beers flavored with Huell Melon hops.

A method for psychophysical screening of odorants for use in city gas based on olfactory adaptation tolerance

In many developed nations, natural gas (so-called city gas) is supplied as a utility for cooking, heating, and hot-water supply. Because natural gas is odorless, city gas must be odorized so that it can be detected in the event of a leak. Although high adaptation tolerance is an important criterion for city gas odorants, there is yet no standard method of evaluating the psychophysical suitability of new candidate odorants in terms of olfactory adaptation. In order to address this situation, we developed a method for psychophysical screening of new candidate odorants for use in city gas based on adaptation tolerance. We used the main component of the conventional city gas odor (tertbutylmercaptan, TBM) and six new candidate odorants: cyclohexene (CH), ethyl isobutyrate (EI), isovaleric acid (IVA), 2-hexene (HEX), 1,5-cyclooctadiene (COD), and 1-methylpyrrolidine (MEP). Participants evaluated the perceived intensity of a continuously presented odor at a fixed concentration. After the time-intensity curves were quantitatively classified into fast or slow adaptation patterns, we compared the number of intensity curves classified into each pattern between TBM and each new odorant. Our results revealed that HEX has a significantly higher adaptation tolerance than TBM, and that the other five new candidate odorants were almost equivalent to TBM in terms of adaptation tolerance. We concluded that all of the new candidate odorants used in this study passed the psychophysical screen based on adaptation tolerance, and are therefore suitable for use in city gas.

Odorant Screening and Quantitation of Thiols in Carmenere Red Wine by Gas Chromatography-Olfactometry and Stable Isotope Dilution Assays.

The sensory impact of thiols in Vitis vinifera 'Carmenere' red wines was evaluated. For this purpose, aroma extract dilution analysis was applied to the thiols isolated from a Carmenere red wine by affinity chromatography with a mercurated agarose gel. Results revealed the presence of four odorants, identified as 2-furanylmethanethiol, 3-sulfanylhexyl acetate, 3-sulfanyl-1-hexanol, and 2-methyl-3-sulfanyl-1-butanol, with the latter being described here for the first time in Carmenere red wines. Quantitation of the four thiols in the Carmenere wine screened by aroma extract dilution analysis and in three additional Carmenere wines by stable isotope dilution assays resulted in concentrations above the respective orthonasal odor detection threshold values. Triangle tests applied to wine model solutions with and without the addition of the four thiols showed significant differences, thus suggesting that the compounds do have the potential to influence the overall aroma of red wine.

Coupling of olfactory receptor and ion channel for rapid and sensitive visualization of odorant response

In the human smell sensing system, there are about 390 kinds of olfactory receptors (ORs) which bind to various odorants with different affinities and specificities. Characterization and odorant binding pattern analysis of the ORs are essential for understanding of human olfaction and to mimic the olfactory system in various applications. Although various cell-based odorant screening systems have been developed for this purpose, many human ORs (hORs) still remain orphan because of the time-consuming and labor-intensive experimental procedures of the available screening methods. In this study, we constructed an ion channel-coupled hOR for simple odorant detection by rapidly visualizing the odorant response to overcome the limitations of conventional screening systems. The hORs were coupled to the Kir6.2 potassium channel and the fusion proteins were expressed in HEK293 cells. In this system, when an odorant binds to the hORs coupled to the ion channel, a conformational change in the OR occurs, which consequently opens the ion channel to result in ion influx into the cell. This ion influx was then visualized using a membrane potential dye. Cells expressing ion channel-coupled hORs showed high sensitivity and selectivity to their specific odorants, and the odorant-hOR binding pattern was visualized to identify the response of individual hORs to various odorants, as well as the response of various hORs to various odorants. These results indicate that the ion channel-coupled hOR system can be effectively used not only for simple and fast high-throughput odorant screening, but also to visualize the odorant-hOR response pattern.

Odorant screening and possible origin analysis of odor episodes in one reservoir in northern China

Research Article| November 29 2015 Odorant screening and possible origin analysis of odor episodes in one reservoir in northern China Xin Li; Xin Li 1Tsinghua-Veolia Joint Research Center for Advanced Environmental Technology, School of Environment, Tsinghua University, Beijing 100084, China Search for other works by this author on: This Site PubMed Google Scholar Jun Wang; Jun Wang 1Tsinghua-Veolia Joint Research Center for Advanced Environmental Technology, School of Environment, Tsinghua University, Beijing 100084, China Search for other works by this author on: This Site PubMed Google Scholar Yuanyuan Liu; Yuanyuan Liu 1Tsinghua-Veolia Joint Research Center for Advanced Environmental Technology, School of Environment, Tsinghua University, Beijing 100084, China Search for other works by this author on: This Site PubMed Google Scholar Jian Shi; Jian Shi 2Shanghai Municipal Control & Monitor Centre of Water Supply, Shanghai 200002, China Search for other works by this author on: This Site PubMed Google Scholar Xiaojian Zhang; Xiaojian Zhang 1Tsinghua-Veolia Joint Research Center for Advanced Environmental Technology, School of Environment, Tsinghua University, Beijing 100084, China Search for other works by this author on: This Site PubMed Google Scholar Chao Chen Chao Chen 1Tsinghua-Veolia Joint Research Center for Advanced Environmental Technology, School of Environment, Tsinghua University, Beijing 100084, China E-mail: chen_water@tsinghua.edu.cn Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2015) 64 (7): 847–856. https://doi.org/10.2166/aqua.2014.069 Article history Received: March 18 2014 Accepted: October 21 2014 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation Xin Li, Jun Wang, Yuanyuan Liu, Jian Shi, Xiaojian Zhang, Chao Chen; Odorant screening and possible origin analysis of odor episodes in one reservoir in northern China. Journal of Water Supply: Research and Technology-Aqua 11 November 2015; 64 (7): 847–856. doi: https://doi.org/10.2166/aqua.2014.069 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Odorous drinking water problem occurred repeatedly in one city in northern China in recent years. The uniqueness of this odor episode lay in two aspects: (1) the odorous chemicals were quite different from common odorants, such as geosmin and 2-MIB; and (2) it occurred repeatedly in different seasons during a time span of more than 2 years. The screening of odorants was the first and one of the most important steps to address this problem. The field study eliminated the possibility of external pollution and targeted on odorous algal excretion. Odorous water samples were taken at different locations. Headspace solid phase microextraction combined with gas chromatography/mass spectrometry (GC/MS) was employed to identify possible odorants. Algal species were observed under a microscope. The GC/MS results indicated that pyrazines and aldehydes, rather than geosmin and 2-MIB, were the most possible peace breakers. Other odorants, such as ketones and thiols, were also detected at trace level. The planktonic algae were detected in high populations in the reservoir. Diatom was regarded as the most possible source of the odor. Guidelines for odorants removal in water treatment process were made to help the local water company address future odor problem. algae, drinking water, odor, screening © IWA Publishing 2015 You do not currently have access to this content.

Cell-based high-throughput odorant screening system through visualization on a microwell array

The development of a cell-based high-throughput screening system has attracted much attention from researchers who study drug screening mechanisms and characterization of G-protein coupled receptors (GPCRs). Although olfactory receptors (ORs) constitute the largest group of GPCRs that play a critical role recognizing and discriminating odorants, only a few ORs have been characterized, and most remain orphan. The conventional cell-based assay system for characterizing GPCRs, including ORs, is very laborious, time consuming, and requires an expensive assay system. In this study, we developed a simple, low-cost miniaturized odorant screening method by combining Micro-Electro-Mechanical system (MEMs) technique and visualization technique for detecting an odorant response. We fabricated PEG microwell from a photocrosslinkable polyethylene glycol diacrylate (PEGDA) solution and applied it to cell culture and a reverse transfection platform for cell-based high-throughput screening. For the first time, the olfactory receptors were expressed on the microwell platform using reverse transfection technique. The various olfactory receptors can be expressed simultaneously using this technique and the microwell spotted with olfactory receptor genes can be used as a high-throughput screening platform. The odorant response was detected via fluorescence analysis on the microwell using a cAMP response element (CRE) reporter assay. We tested this platform using four de-orphaned ORs. This new cell-based screening method not only reduced numerous time-consuming steps but also allowed for simple, efficient, and quantitative screening and patterning of large numbers of GPCRs including ORs, which can help to visualize the OR response to odorants on a microwell.

Functional Characterization of Two Human Olfactory Receptors Expressed in the Baculovirus Sf9 Insect Cell System

Olfactory receptors (ORs) are the largest member of the G-protein-coupled receptors which mediate early olfactory perception in discriminating among thousands of odorant molecules. Assigning odorous ligands to ORs is a prerequisite to gaining an understanding of the mechanisms of odorant recognition. The functional expression of ORs represents a critical step in addressing this issue. Due to limitations in heterologous expression, very few mammal ORs have been characterized, and so far only one is from human origin. Consequently, OR function still remains poorly understood, especially in humans, whose genome encodes a restricted chemosensory repertoire compared with most mammal species. In this study, we have designed cassette baculovirus vectors to coexpress human OR 17-209 or OR 17-210 with either G(alpha olf) or G(alpha16) proteins in Sf9 cells. Each OR was found to be expressed at the cell surface and colocalized with both G(alpha) proteins. Using Ca2+ imaging, we showed that OR 17-209 and OR 17-210 proteins are activated by esters and ketones respectively. Odorant-induced calcium response was increased when ORs were coexpressed with G(alpha16) protein, whereas coexpression with G(alpha olf) abolished calcium signaling. This strategy has been found to overcome most of the limitations encountered when expressing an OR protein and has permitted odorant screening of functional ORs. Our approach could thus be of interest for further expression and ligand assignment of other orphan receptor proteins.

Functional expression of olfactory receptors in yeast and development of a bioassay for odorant screening

The functional expression of olfactory receptors (ORs) is a primary requirement to examine the molecular mechanisms of odorant perception and coding. Functional expression of the rat I7 OR and its trafficking to the plasma membrane was achieved under optimized experimental conditions in the budding yeast Saccharomyces cerevisiae. The membrane expression of the receptor was shown by Western blotting and immunolocalization methods. Moreover, we took advantage of the functional similarities between signal transduction cascades of G protein-coupled receptor in mammalian cells and the pheromone response pathway in yeast to develop a novel biosensor for odorant screening using luciferase as a functional reporter. Yeasts were engineered to coexpress I7 OR and mammalian G(alpha) subunit, to compensate for the lack of endogenous Gpa1 subunit, so that stimulation of the receptor by its ligands activates a MAP kinase signaling pathway and induces luciferase synthesis. The sensitivity of the bioassay was significantly enhanced using mammalian G(olf) compared to the G(alpha15) subunit, resulting in dose-dependent responses of the system. The biosensor was probed with an array of odorants to demonstrate that the yeast-borne I7 OR retains its specificity and selectivity towards ligands. The results are confirmed by functional expression and bioluminescence response of human OR17-40 to its specific ligand, helional. Based on these findings, the bioassay using the luciferase reporter should be amenable to simple, rapid and inexpensive odorant screening of hundreds of ORs to provide insight into olfactory coding mechanisms.