Odor Components Research Articles

Ti-Catalyzed Regiodivergent Openings of Unbiased Epoxides

The first titanium-catalyzed regio­divergent ring opening of sterically and electronically unbiased epoxides, which emcompasses the popular desymmetrization of meso-epoxides, is described. For racemic epoxides, regioselectivities and ee values are modest except if a chelating group is present on one substituent. Enantio­enriched epoxides provide high selectivities and ee values due to a double asymmetric process. The hydroxyester products are useful precursors for the synthesis of γ- and δ-lactones such as (R)-4-dodecanolide (in beetle secretions) and (R)-5-dodecanolide (component of cheddar odor).

Scent marking behavior in male C57BL/6J mice: Sexual and developmental determination

The present study investigated urinary scent marking behavior in male C57BL/6J (C57) mice as olfactory social signaling. In Experiment 1, when compared scent marking toward adult males, C57 males showed substantial scent marking toward CD-1 males and even toward the odor alone of CD-1 males, but not toward C57 males. Experiment 2 explored scent marking in C57 males of different ages to males and females, and juveniles and adults of the same strain. C57 males deposited more marks than control conditions only toward an adult C57 female when tested at 100 days of age, but not at 60 days of age. Development of urine marking behavior was investigated in C57 males at the ages of 30, 60, 90, and 120 days in Experiment 3. When tested alone (control) or confronted with a C57 male, C57 males showed diminished scent marks throughout development. Compared to controls, marking toward a CD-1 male increased after the age of 60 days, while marks toward an adult female showed significant increases after the age of 90 days. This difference in scent marking depending on the sex of the stimulus animal is likely to be associated with development of sexual behavior, in which males need to set up territories against other males prior to advertising to females. Although highly inbred strains have similar odor components, C57 males are able to detect and deposit urine marks after puberty as social communication depending on age, sex, and genetic differences in the opponents.

Study of odor recorder based on preconcentrator with variable temperature

A new prototype of odor recorder with higher-order sensing capability was proposed. This system was developed using a preconcentrator with variable temperature so that higher-order sensing based upon the different desorption property of each odor component can be achieved. The enriched data were used for odor recording process using a five-level quantization method to estimate recipes of the target odors. In order to investigate the fundamental capability of this system, recipe estimations of the target odors were performed using four odor components even including the two with high similarities in sensor response patterns. The recipes of target odors were appropriately estimated using the proposed odor recorder while the previous method without a preconcentrator was not successful. This proposed system is useful to enhance the robustness of recipe estimation against collinearity.

The Major Histocompatibility Complex and Perfumers' Descriptions of Human Body Odors

The MHC (major histocompatibility complex) is a group of genes that play a crucial role in immune recognition and in tolerance of tissue grafting. The MHC has also been found to influence body odors, body odor preferences, and mate choice in mice and humans. Here we test whether verbal descriptions of human body odors can be linked to the MHC. We asked 45 male students to live as odor neutral as possible for two consecutive days and to wear a T-shirt during the nights. The odors of these T-shirts were then described by five evaluators: two professional perfumers and three laymen. One of the perfumers was able to describe the T-shirt odors in such a way that some of the allelic specificity of the MHC was significantly revealed (after Bonferroni correction for multiple testing). This shows that, although difficult, some people are able to describe MHC-correlated body odor components.

Component Information Is Preserved in Glomerular Responses to Binary Odor Mixtures in the Moth Spodoptera littoralis

Natural odors are often complex mixtures of different compounds. These mixtures can be perceived to have qualities that are different from their components. Moreover, components can be difficult to distinguish within a blend, even if those components are identifiable when presented individually. Thus, odor components can interact along the olfactory pathway in a nonlinear fashion such that the mixture is not perceived simply as the sum of its components. Here we investigated odor-evoked changes in Ca2+ concentration to binary blends of plant-related substances in individually identified glomeruli in the moth Spodoptera littoralis. We used a wide range of blend ratios and a range of concentrations below the level at which glomerular responses become saturated. We found no statistically significant cases where the mixture response was greater than both component responses at the same total concentration (synergistic interactions) and no statistically significant cases where the mixture response was less than either component presented individually (suppressive interactions). Therefore, we conclude that, for the plant mixtures studied, information of their components is preserved in the neural representations encoded at the first stage of olfactory processing in this moth species.

Charcoal-Adsorption, Water-Washing, and Air-Dilution Systems to Reduce Diesel Emissions With Special Emphasis on Odor Reduction

Direct injection (DI) diesel engines emit a far more disagreeable exhaust odor than gasoline engines, especially at low temperatures and at idling. There is no proper system of odor reduction in these conditions in DI diesel engines. This study investigated a charcoal-adsorption system to reduce exhaust emissions including odor in a DI diesel engine at idling under no load operations, where exhaust temperatures are low. Low temperature exhaust gas is passed through a charcoal adsorber. Charcoal has the property of adsorbing odorous gas components. Here odor is reduced more than 0.5 points, a significant odor reduction depending on the engine and adsorber conditions. Exhaust noise, nitrogen oxides (NOx), and eye irritation are also significantly reduced with the system. This study further investigated water-washing system for odor reduction in DI diesel engines at low exhaust temperature conditions. Exhaust gas is passed through the water in the water tank of the system. Aldehydes, organic acids, and other oxygenated components, which are the main odorous components in exhaust gases, are dissolved in water reducing exhaust odor significantly. Eye irritation of exhaust gases is also significantly reduced. The water-washing system not only reduces the odor and eye irritation but also carbon dioxide (CO2), carbon monoxide (CO), NOx, and smoke are reduced more than 20–30%. The sound level of exhaust gases is also reduced 10–15dB with this system. Air dilution is also attempted in this study for odor reduction where a large amount of fresh air is mixed with exhaust gases. Here dilution ratio of 5 is used. Air dilution alone can reduce odor about 0.5 points. However, odor about 1.5–1.6 points (about 60–65%) can be reduced when air dilution is used in combination with charcoal-adsorber and water-washing system, and odor level is lowered below level 2, which is acceptable for all human beings.

Realization of recording a wide range of odor by utilizing both of transient and steady-state sensor responses in recording process

An odor recorder is a system to record and reproduce odors. In order to record wide a range of odors, a number of available odor components are required in an odor recorder. Although many odor components were available in a previously developed odor recorder using an automatic sampler, there is still a collinearity problem caused by the lack of pattern separation among odor components. Then, we propose a new odor recorder with a wider recording range based on both transient and steady-state sensor responses in recording process. In this system, time constants are extracted from QCM sensor responses using the auto regressive (AR) model and are used together with conventional steady-state frequency shifts as variables to discriminate among odor components. Based on this proposed method, the pattern separation among odor components can be improved and up to 13 odor components can be used with a minimized collinearity problem. Recipes of five target odors with different impressions were successfully estimated based on the same set of these 13 odor components and sufficient similarities of impressions between all approximated odors and their target ones were confirmed by a human panel.

Characteristic component odors emerge from mixtures after selective adaptation

Humans cannot reliably identify the distinctive characteristic odors of components in mixtures containing more than three compounds. In the present study, we demonstrate that selective adaptation can improve component identification. Characteristic component odors, lost in mixtures, were identifiable after presenting other mixture constituents for a few seconds. In mixtures of vanillin, isopropyl alcohol, l-menthol and phenethyl alcohol, this rapid selective adaptation unmasked each component. We suggest that these findings relate directly to how olfactory qualities are coded: olfactory receptors do not act as detectors of isolated molecular features, but likely recognize entire molecules closely associated with perceived olfactory qualities or “notes”. Rapid and focused activation of a few distinct receptor types may dominate most odor percepts, emphasizing the importance of many dynamic and specific neural signals. An interaction between two fundamental coding strategies, mixture suppression and selective adaptation, with hundreds of potential olfactory notes, explains humans experiencing the appearance and disappearance of identifiable odors against ambient mixture backgrounds.

Deodorisation of off-odour during sweet potato juice production by employing physical and chemical deodorants

The mechanism and efficiency of three types of deodorants, namely activated carbon (AC), maltosyl cyclodextrin (MCD) and apple polyphenol (AP), in reducing the “boiled heavy odour” of saccharified sweet potato juice was investigated. The highest deodorising efficiency of AC, followed by MCD and AP, was confirmed by using the electronic nose and sensory analysis. Furthermore, flavour compounds in the sweet potato juice were identified by GC–MS analysis. While AC decreased the peak intensities of all the compounds to below the minimum detection limit, MCD, which eliminated the odour components by the formation of enclosure compounds, did not reduce the peak intensities to a similar extent. The mechanisms of adsorption with AC and envelopment with MCD for the identified odour components of sweet potato juice was also clarified.

Impact of nonsurgical periodontal therapy on oral malodor and microbial load of saliva

Breath malodor affects a large proportion of population and may be the cause of a significant social and psychological problem1). It can be caused by a number of factors, both of intraand extra-oral origins. Among oral etiological factors, breath malodor may result from periodontal diseases, poor salivary flow, improper dental restorations, excessive microbial colonization of the tongue, and unclean denture2,3). Extraoral etiological factors include upper and lower respiratory tract abnormal conditions, gastrointestinal and neurologic disorders, various systemic diseases and certain drugs4). In several studies, however, about 90% of breath malodor have an intraoral origin, mostly gingivitis, periodontitis and/or tongue coating5-7).1) The principal components of breath malodor are volatile sulphide compounds (VSCs), especially hydrogen sulphide (H2S), methyl mercaptan (CH3SH) and dimethyl sulphide [(CH3)2S] or compounds such as butyric acid, propionic acid, putrescine, and cadaverine2). These are made from the proteolytic degradation predominantly by anaerobic gram-negative bacteria on plaque, tongue coatings, saliva, blood and epithelial cells8). There are various methods to assess breath malodor. The main approaches are organoleptic ratings, gas chromatography, and sulphide monitoring. Organoleptic ratings assessed by human judges still are the golden standard9). But, this method raises several problems including low intraor inter-examiner reproducibility (reliability) and lack of official standards6). Although, gas chromatography allowing detection of all possible odorous component

Binary mixture perception is affected by concentration of odor components.

Some controversy still exists as to how binary odorant mixtures are behaviorally perceived, despite many studies aimed at understanding this phenomenon. Binary mixture perception by rodents is a first step in elucidating how more complex odor blends may be perceived. Research thus far has examined how the degree of component similarity, olfactory receptor overlap, relative concentration of components, and even olfactory enrichment affect the behavioral perception of binary mixtures. These studies have aimed to categorize binary mixtures into 1 of 3 rigid categories, but often the results conflict as to which category a particular mixture belongs. In the present article, the authors used a habituation/discrimination paradigm to determine whether rats' perception of one component of a binary mixture of either perceptually similar or dissimilar components changed when the concentration of both components was varied together. The authors found that perception of a binary mixture changed with changing component concentration, such that one binary mixture could be categorized differently depending on component intensity.

Odor approximation of fruit flavors using a QCM odor sensing system

Odor approximations of orange and melon flavors were performed using an array of quartz crystal microbalance (QCM) odor sensors coated with different materials, such as lipids and stationary phase materials of gas chromatography (GC). The steady state sensor responses to single flavor components were measured and the data were used to estimate the important odor components by means of a computational two-level quantization method. From these results, the experimental approximations using the steady state sensor responses and principal component analysis (PCA) were performed. In both cases, orange and melon flavors, it was possible to approximate the recipes with only three odor components. Moreover, the similarities between the approximated odors and the original ones were evaluated by a human sensory test. It was found that these similarities were high, especially in the case of orange flavor.

Chemical Identification of MHC-influenced Volatile Compounds in Mouse Urine. I: Quantitative Proportions of Major Chemosignals

The genes of the major histocompatibility complex (MHC) are highly polymorphic loci that encode cell surface proteins, class I and II molecules. They present peptide antigens to T cells and thereby control immunological self/nonself recognition. Increasing evidence indicates that MHC genes also influence odor and mating preferences; however, it is unclear how. Here we report the results of chemical analyses of male mouse urinary odors collected from a variety of mouse strains, including MHC-congenics, recombinants, mutants, and transgenics (i.e., beta2 microglobulin "knockouts," which lack class I expression, and transporters associated with antigen processing (TAP) knock-outs). After the identification of volatile odor components by gas chromatography/mass spectrometry, the odor profiles of urine samples were analyzed quantitatively by using stir bar sorptive extraction and gas chromatography/atomic emission detection. Results showed that MHC genes influenced the amounts of testosterone-mediated pheromones, sulfur-containing compounds, and several carbonyl metabolites. This is the first report to quantitatively link known mouse pheromones to classical, antigen-binding MHC loci. Surprisingly, these compounds were not influenced by TAP genes, even though these loci are MHC-linked and play a role in peptide presentation. Whereas identification of MHC-determined odorants does not reveal their metabolic origin, some constituents were also present in blood serum, and their levels were not altered by antibiotics.

Selected Odor Compounds in Soymilk As Affected by Chemical Composition and Lipoxygenases in Five Soybean Materials

Protein, fat content, and beany odor affect consumers' choice of soy foods. Our objective was to characterize protein, lipid, and lipoxygenase activities and fatty acid compositions in food soybeans and to determine how chemical composition and enzyme activities related to the generation of beany odor components, including hexanal, hexanol, trans-2-nonenal, 1-octen-3-ol, and trans-2,trans-4-decadienal in soymilk. Protein, lipid, and fatty acid compositions and lipoxygenase activities of five soybean materials, including Proto, IA2032, IA 2064, IA3017, and L-Star varieties, were analyzed. Soymilk was prepared by a traditional method involving soaking, grinding, and cooking processes. Selected odor compounds in raw and cooked soymilk were analyzed by solid-phase microextraction and gas chromatography. Results showed that soybeans differed in crude protein and lipid content, lipoxygenase activities, and fatty acid compositions. L-Star had the highest and Proto the lowest lipid content among the five soybean cultivars. Protein content, lipoxygenases, and linoleic acid were positively correlated with beany odor content in soymilk made from the selected soybean materials. After boiling for 20 min, the soymilk made from L-Star and IA2032 retained the lowest odor profiles among the soymilk products made from the five selected materials.

Static headspace analysis-olfactometry (SHA-O) of odor impact components in salted-dried white herring ( Ilisha elongata)

The odorous components of salted-dried white herrings from different treatment conditions were determined by static headspace analysis-olfactometry (SHA-O). Fish samples were purchased from two locations, manufactured by two methods, purchased for two consecutive years, and investigated at two conditions (raw and steamed). Twenty-seven odorous compounds were found among the fish products including alcohols (3), aldehydes (7), miscellaneous compounds (2), ketones (3), other N-containing compounds (4), other O-containing compounds (1), and S-containing compounds (7). Seven potent components including 3-methylbutanal (almond-like), methanethiol (decay vegetable-like), dimethyl trisulfide (fried garlic, onion-like), hydrogen sulfide (rotten egg-like), trimethylamine (fishy, fish oil-like) bis(methylthio)methane (fried garlic/onion-like), and ( Z)-4-heptenal (fatty, grease-like) were identified. The majority of them did not have significant difference among the different treatments ( p > 0.05). Other less potent components may contribute to the odor of a fish due to their differences in distribution and potency. Statistically, only location and method × period interaction have major impacts on the magnitude of the odorants found in salted-dried white herrings ( p < 0.05).

The trial-spacing effect in olfactory patterning discriminations in honeybees

Harnessed bees conditioned to associate odors and sucrose reward learn to discriminate between olfactory mixtures and their odor components in negative (NP: A+, B+, AB−) and positive (PP: A−, B−, AB+) patterning experiments. They thus extend the proboscis to the reinforced (CS+) but not to the non-reinforced (CS−) stimuli. Using the same protocol, we studied whether or not trials, which are spaced in time, are more effective in supporting patterning discrimination than massed trials which succeed fast to each other (‘trial-spacing effect’). Training followed a NP (4 A+, 4 B+, 8 AB−) or a PP (4 A−, 4 B−, 8 AB+) schedule, with a 1:1 ratio between CS+ and CS− trials (8 CS+ and 8 CS− trials). ITIs of 1, 3, 5 and 8 min were used in both tasks. Increasing ITI resulted in better differentiation between reinforced and non-reinforced CSs in both NP and PP tasks. However, whereas only the longest ITI of 8 min allowed discrimination in NP, PP could already be solved with an ITI of 5 min. This difference might be due to the fact that NP, but not PP, would require the formation of a unique cue and thus longer processing times. We thus show that the trial-spacing effect, previously demonstrated for single stimulus conditioning, also determines performance in patterning tasks in which three different stimuli (A, B, AB) alternate so that elements have to be discriminated from their compound.

Movie with Scents Generated by Olfactory Display Using Solenoid Valves

We developed an olfactory display to blend 8 component odors at any composition. The solenoid valves controlled by an algorithm with delta sigma modulation showed the sufficient capability. Then, we developed a system for presenting a movie together with scents. We actually made a movie with scents and evaluated it using questionnaire survey. It was found that the scene with smell attracted the experimental subjects' attention and, moreover, the contrast of the pleasant smell with the offensive one emphasized their attention. Furthermore, we established several guidelines for producing movies with scents.

Volatile odour components and sensory quality of fresh and processed mandarin juices

AbstractTwelve volatile compounds were quantified by gas chromatography/mass spectrometry in juices from two Spanish mandarin varieties, Fortuna and Clemenules. Fresh Clemenules juice contained a higher amount of total volatile compounds (61.1 ± 1.1 mg L−1) than fresh Fortuna juice (48.8 ± 2.5 mg L−1), with D‐limonene (97.1%), myrcene (1.7%), sabinene (0.5%), α‐pinene (0.3%) and linalool (0.3%) being the predominant compounds. Pasteurisation of the mandarin juices (20 s at 98 °C) caused a significant reduction (∼12%) in vitamin C concentration. On the other hand, vitamin C was stable during storage of the juices for 60 days in aseptic tanks at 2 °C. Volatile compounds, however, were more affected by storage in aseptic refrigerated tanks (2 °C) than by heat treatment. Pasteurisation caused a mean decrease in the total concentration of volatile compounds of about 18%, while, after a storage time of 60 days, 36% of total volatiles present in the juices after pasteurisation were lost from both Fortuna and Clemenules juices. Significant reductions in the concentrations of D‐limonene, myrcene, sabinene, α‐pinene and linalool were found, while those of α‐terpineol and terpinen‐4‐ol increased. Copyright © 2006 Society of Chemical Industry

Attraction of Spodoptera frugiperda Larvae to Volatiles from Herbivore-Damaged Maize Seedlings

Plants respond to insect attack with the induction of volatiles that function as indirect plant defenses through the attraction of natural enemies to the herbivores. Despite the fact that volatiles are induced in response to caterpillar attack, their reciprocal effects on the host location behaviors of the same foraging herbivores are poorly understood. We examined orientation responses of sixth instar fall armyworm [FAW; Spodoptera frugiperda (Smith)] to odors from herbivore-damaged and undamaged maize seedlings (Zea mays var. Golden Queen) in y-tube olfactometer bioassays. While both damaged and undamaged maize seedlings were attractive compared with air, sixth instars preferred odors from damaged maize seedlings over odors from undamaged maize seedlings. Gas chromatography-mass spectrometry analysis of plant volatiles revealed that linalool and 4,8-dimethyl-1,3,7-nonatriene were the major volatiles induced by FAW herbivory 6 hr after initial damage. Given its prominence in induced plants and established attractiveness to adult FAW, linalool was evaluated both as an individual attractant and as a supplemental component of whole plant odors. Volatile linalool was more attractive than air to sixth instar FAW over a broad range of release rates. FAW also responded selectively to different amounts of linalool, preferring the higher amount. The orientation preferences of FAW were readily manipulated through capillary release of linalool into the airstream of whole plant odors. FAW preferred linalool over undamaged plant odors, and linalool-supplemented plant odors over unsupplemented plant odors, indicating that olfactory preferences could be changed by alteration of a single volatile component. These results suggest that although many induced volatiles attract natural enemies of herbivores, these defenses may also inadvertently recruit more larval herbivores to an attacked plant or neighboring conspecifics.

Geographic Variation in Attraction to Human Odor Compounds by Aedes aegypti Mosquitoes (Diptera: Culicidae): A Laboratory Study

Previous investigations of Aedes aegypti response to human odor components have revealed a number of compounds that attract host-seeking females. However, such studies have utilized only a small number of long-term laboratory Ae. aegypti colonies. Using laboratory y-olfactometers, we studied the attraction of four different Ae. aegypti populations (North Queensland, Australia; Florida, USA; Singapore; and Minas Gerais, Brazil) to a key attractant compound from human skin, lactic acid. Combinations of lactic acid with ammonia and a fatty acid (caproic acid) were also investigated. The aims were to determine the extent of variation in lactic acid dose response among populations and to see whether all four populations responded equally to combinations of human odor components. Although all Ae. aegypti populations were attracted to lactic acid, there were differences in the threshold dose: Florida 0.03 microg/min, Singapore 0.17 microg/min, North Queensland 1.92 microg/min, and Brazil 10.27 microg/min. Attraction to lactic acid alone (maximum <40%) was significantly lower than for human odor (>87% for all populations). Significant increases in attraction were observed when lactic acid was combined with ammonia or caproic acid, although not for all populations. In addition, the highest doses of caproic acid tested decreased attraction when combined with lactic acid. The divergent responses to host kairomones seen here may be evidence of adaptation to locally available hosts in different parts of the geographic range of Ae. aegypti.