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Odor Threshold Determinations of 53 Odorant Chemicals
Abstract
In order to assist in assessing potential odor problems arising from chemical manufacturing operations, the odor thresholds of 53 commercially important odorant chemicals have been determined using a standardized and defined procedure. The odor threshold data previously available have shown wide variation reflecting the diversity of procedures and techniques used. Factors that may affect the odor threshold measurement include the mode of presentation of the stimulus to the observer, the influence of extraneous odorants in the presentation system, the type of observer used, the definition of the odor response, the treatment of the data obtained, and the chemical purity of the odorant. The experimental approach used has minimized these variations. The odorants were presented to a trained odor panel in a static air system utilizing a low odor background air as the dilution medium. The odor threshold is defined as the first concentration at which all panel members can recognize the odor. The effect of chemical purity has been determined by measuring the odor threshold of materials representing different modes of manufacture or after purification by gas chromatographic procedures. The threshold concentrations range over six orders of magnitude. Trimethylamine exhibited the lowest threshold (0.00021 ppm volume); methylene chloride was not recognizable below 214 ppm. Of the 53 chemicals, sulfur bearing compounds exhibit low threshold values on the order of parts per billion. Aside from the sulfides, it is not possible to anticipate the odor threshold of a material based on its chemical structure or functionality.
... A step factor greater than three is not recommended as it significantly affects the accuracy of odor measurements (Boeker and Haas, 2007;Boeker et al., 2008). Earlier studies deviated from these specifications, such as Leonardos et al. (1969), who used multiples by ten of 1.0, 2.1, and 4.6 as step factors, or Punter (1983), who used variable step factors between 2.4 and 3.4 within one dilution series. ...
... Solid odorants can be dissolved with a suitable, odorless diluent, and the solution can then be treated as a liquid (Dravnieks, 1975). Another method is to volatilize a weighed amount of the solid odorant through a (hot) air stream (Leonardos et al., 1969). ...
... At an earlier stage of olfactometry, it was thought that a natural breathing situation would result in more realistic ODT (Schneider and Wolf, 1955;Wenzel, 1955). Leonardos and colleagues determined odor thresholds for 53 chemicals in a temperature-and humidity-controlled test room (Leonardos et al., 1969). In this study, the test room itself served as dilution medium. ...
Odor evaluation is an important topic in the field of indoor air quality. Odor detection threshold (ODT) values are used to derive limit values like odor guide values or odor activity value. However, ODT values for the same substance available in compilations or published before 2003 rarely have an accuracy of less than three orders of magnitude. Stimulus preparation, including analytical verification, stimulus presentation, as well as selection and training of test subjects have been identified as major sources of variability. ODT values obtained by validated standardized methods are now considered objective, reliable, and reproducible. They exhibit a variability of one or two orders of magnitude and are lower than traditionally assumed and reported. This review presents the essential criteria for a well-performed ODT determination. It is intended to assist health and safety professionals in assessing whether the methodological approach of a study was appropriate for determining a valid and reliable ODT value.
... The Odour Threshold for ammonia has been documented in different studies as low as 0.04 ppm and as high as 57 ppm. The American Association of Railroads says most people can smell ammonia between 0.04 and 20 ppm and according to OSHA, Odour Threshold is between 5 and 50 ppm (Leonardos et al., 1969). According to the National Institute of Occupational Safety and Health Act (NIOSH), for a potential exposure of over 25 ppm, a NIOSH approved full facepiece must be used and it must contain a cartridge which is specially approved for ammonia. ...
... Air-purifying respirators should also be used to enhance the layer of protectivity. In cases where the exposure exceeds 250 ppm, a supplied-air respirator with a full facepiece and approved by NIOSH must be used and operated in a pressure-demand mode (Leonardos et al., 1969). Concentrations lower than 300 ppm requires respirators but above that, self-containment is mandatory (Cameron, 2009a). ...
This article is a roadmap for researchers in this field to look for an efficient and reliable alternative for fossil fuels in the form of ammonia. We have discussed different storage techniques, with one of them being ‘solid ammonia storage method’ using MOFs and metal ammine complexes as a better option to deal with ammonia toxicity. Besides, we have discussed various approaches of direct and indirect ammonia being used in internal combustion engines as fuel or within fuel cells for creating a sustainable energy source for the onboard vehicular application. To discuss ammonia's feasibility as a commercial fuel, a detailed discussion on ammonia economy is important. So, in the later sections of the article, we have discussed ammonia economy, emerging technologies for ammonia production, cost analysis, investment, the economics of vehicle engines and fuel cells, and opportunities ahead. In the article, apart from just advocating the feasibility of using ammonia as a future fuel, the authors have also talked about its downsides, associated challenges, and how there are alternative pathways to use ammonia indirectly as well. The authors believe that in the literature, very few articles present such a broad discussion on ammonia's feasibility as a future fuel. Thus, we believe this article will help the readers in formulating their own opinion regarding ammonia and work on finding the right fuel for a sustainable future.
... Crude sulfate turpentine (CST) and its distilled fractions usually contain high concentrations (5000 ppm and above) of sulfur compounds (Jennings 1939;Lloyd and Bruce 1994;Leonardos et al. 1969;Ilichev et al. 2014;Rehman et al. 2016). These compounds are transported to the distillate fraction of turpentine and adversely affect the reactions of fractions (Hamby et al. 1972). ...
... The odor problems arising from manufacturing operations of kraft processing, the odor thresholds of the sulfurous odorant chemicals (Leonardos et al. 1969), and final sulphur content (Collins and Brunswick 1946;Prochazka and Foy 1958;Lloyd and Bruce 1994;Hwang et al. 1994;Wang et al. 2011;Tyurmina et al. 2017;Sinhmar and Gogate 2020) are of vital importance (Rehman et al. 2016). They need to be controlled to represent the effect of chemical purity represented in Table 1. ...
Crude sulfate turpentine (CST), a by-product of the kraft process, has commercial value that depends on the removal of sulfur compounds. The current study investigates desulfurization of CST using basic process steps for a paper mill at a pilot scale treatment. In another aspect, the sulfurous compounds in CST were removed by passing to the aqueous phase with terpin hydrate production, followed by α-terpineol conversion with citric acid catalysis. The goal was to design an environmentally friendly, low-cost, zero waste process and thereby refine the CST or byproducts to a quality that can produce chemical raw materials. Refining processes included hypochlorite oxidation, air oxidation, washing with water, and distillation. The sulfur content was decreased to 170, 106, and 29 ppm from respectively by 1260 ppm initial sulphur content of CST. The chlorine amount, due to treatment with hypochlorite oxidation, did not decrease with refining processes, even in distilled fraction. By obtaining α-terpineol from terpin hydrate, the sulfur compounds were completely removed. According to the GS-MS analysis results, distilled sulfate turpentine (DST) as the final product of the refining process of the CST sample increased the ratio with pinenes. On the other hand, with two reaction steps by obtaining terpin hydrate from CST and then α-terpineol, pinenes were converted to α-terpineol.
... Typically, an exposure of twice the t 90 time is required to get a stable reading. ** Toluene (IE = 8.82 eV; OT = 0.33 ppm [46]) is the dominant compound in the mixture of volatile organic compounds (VOCs) in the tested process gases in analyzed waste biogas plants (based on own, yet unpublished, chromatographic analysis); moreover based on [41] toluene can be used with a close relationship (R 2 = 0.95) in conversion from a GC-based VOC concentration to a PID-based VOC concentration; other compounds present in the highest amounts in process gases from the studied biogas plants processing municipal waste are styrene (IE = 8.43 eV; OT = 0.047 ppm [47]) and phenol (IE = 8.51 eV; OT = 0.048 ppm [48]). Mixed waste storage *** 3 ...
... exposure of twice the t90 time is required to get a stable reading. ** Toluene (IE = 8.82 eV; OT = 0.33 ppm [46]) is the dominant compound in the mixture of volatile organic compounds (VOCs) in the tested process gases in analyzed waste biogas plants (based on own, yet unpublished, chromatographic analysis); moreover based on [41] toluene can be used with a close relationship (R 2 = 0.95) in conversion from a GC-based VOC concentration to a PID-based VOC concentration; other compounds present in the highest amounts in process gases from the studied biogas plants processing municipal waste are styrene (IE = 8.43 eV; OT = 0.047 ppm [47]) and phenol (IE = 8.51 eV; OT = 0.048 ppm [48]). ...
Municipal waste treatment plants are an important element of the urban area infrastructure, but also, they are a potential source of odour nuisance. Odour impact from municipal waste processing plants raises social concerns regarding the well-being of employees operating the plants and residents of nearby areas. Chemical methods involve the determination of the quantitative composition of compounds comprising odour. These methods are less costly than olfactometry, and their efficiency is not dependent on human response. The relationship between the concentration of a single odorant and its odour threshold (OT) is determined by the odour activity value (OAV) parameter. The research involved the application of a multi-gas detector, MultiRae Pro. Measurements by means of the device were conducted at three municipal waste biogas plants located in Poland. In this paper we describe the results obtained when using a detector during the technological processes, the unitary procedures conducted at the plants, and the technological regime. The determination of these relationships could be useful in the development of odour nuisance minimization procedures at treatment plants and the adjustment to them. This is of paramount importance from the viewpoint of the safety and hygiene of the employees operating the installations and the comfort of residents in the areas surrounding biogas plants. Monitoring of expressed odorant emissions allows the course of technological processes and conducted unit operations to be controlled.
... Typically, an exposure of twice the t 90 time is required to get a stable reading. ** Toluene (IE = 8.82 eV; OT = 0.33 ppm [46]) is the dominant compound in the mixture of volatile organic compounds (VOCs) in the tested process gases in analyzed waste biogas plants (based on own, yet unpublished, chromatographic analysis); moreover based on [41] toluene can be used with a close relationship (R 2 = 0.95) in conversion from a GC-based VOC concentration to a PID-based VOC concentration; other compounds present in the highest amounts in process gases from the studied biogas plants processing municipal waste are styrene (IE = 8.43 eV; OT = 0.047 ppm [47]) and phenol (IE = 8.51 eV; OT = 0.048 ppm [48]). Mixed waste storage *** 3 ...
... exposure of twice the t90 time is required to get a stable reading. ** Toluene (IE = 8.82 eV; OT = 0.33 ppm [46]) is the dominant compound in the mixture of volatile organic compounds (VOCs) in the tested process gases in analyzed waste biogas plants (based on own, yet unpublished, chromatographic analysis); moreover based on [41] toluene can be used with a close relationship (R 2 = 0.95) in conversion from a GC-based VOC concentration to a PID-based VOC concentration; other compounds present in the highest amounts in process gases from the studied biogas plants processing municipal waste are styrene (IE = 8.43 eV; OT = 0.047 ppm [47]) and phenol (IE = 8.51 eV; OT = 0.048 ppm [48]). ...
Municipal waste treatment plants are an important element of the urban area infrastruc-ture, but also, they are a potential source of odour nuisance. Odour impact from municipal wasteprocessing plants raises social concerns regarding the well-being of employees operating the plantsand residents of nearby areas. Chemical methods involve the determination of the quantitativecomposition of compounds comprising odour. These methods are less costly than olfactometry, andtheir efficiency is not dependent on human response. The relationship between the concentration ofa single odorant and its odour threshold (OT) is determined by the odour activity value (OAV) pa-rameter. The research involved the application of a multi-gas detector, MultiRae Pro. Measurementsby means of the device were conducted at three municipal waste biogas plants located in Poland. Inthis paper we describe the results obtained when using a detector during the technological processes,the unitary procedures conducted at the plants, and the technological regime. The determination ofthese relationships could be useful in the development of odour nuisance minimization proceduresat treatment plants and the adjustment to them. This is of paramount importance from the viewpointof the safety and hygiene of the employees operating the installations and the comfort of residents inthe areas surrounding biogas plants. Monitoring of expressed odorant emissions allows the course oftechnological processes and conducted unit operations to be controlled.
... nobile) are esters, including 3-methyl-2-butenoic acid, 3methyl-2-alkenyl ester, 3-methyl-2-enoic acid, 2-methyl butyl ester, and 3-methyl-2-butenoic acid allyl ester [21] . These results indicate that the differences in volatile substances also exist among the different species of chamomile. ...
Chrysanthemum is one of the four major cut flowers in the world, with high ornamental and economic value. Fragrance is an important ornamental character of chrysanthemum flowers, especially those consumed as tea and other foods, and the flower fragrance is the major determinant of the commercial value of chrysanthemum cultivars. Currently, however, the research on chrysanthemum flower fragrance is mainly focused on the composition and content of fragrant compounds, and a clear classification of fragrance types is lacking. Here, we divided chrysanthemum fragrance into six categories based on sensory evaluation and determined the identity and content of fragrant compounds of chrysanthemum accessions representative of each fragrance type by GC-MS. In addition, we analyzed the conserved aromatic substances responsible for the fruity fragrance type chrysanthemum with multi-functional development potential, providing a theoretical basis for creating new chrysanthemum germplasm with specific fragrance types. The results of this study can accelerate the breeding process of chrysanthemum accessions with new fragrance types.
... Este trabajo permitió observar la dispersión de los olores que se generaban en el lugar; se encontraron valores de hasta 30,0 µg/m 3 (máximo permitido de 20,0 ppb) de H 2 S dentro de las instalaciones de la planta, los cuales disminuían rápidamente al alejarse de las fuentes. Las concentraciones del H 2 S en los alrededores del pueblo se reportan siempre por debajo del umbral de concentración (0,70 µg/m 3 (0,50 ppb)) (Moreno y Moral, 2008;Leonardos et al., 1969). ...
[Objetivo] Se estudió la variación de las concentraciones del sulfuro de hidrógeno (H2S) y del amoniaco (NH3) en aire, en un sistema de tratamiento de aguas residuales en Costa Rica, para conocer el posible alcance de los olores producidos, con mediciones en el lugar y un modelo de dispersión de sustancias en el aire. [Metodología] Fueron realizados 13 muestreos en periodos de 12 horas y 24 horas, entre octubre del 2016 y febrero del 2017; con las mediciones de campo, se alimentó un modelo de dispersión. Se midieron los parámetros meteorológicos: dirección y velocidad de viento, radiación global, temperatura, porcentaje de humedad relativa, precipitación y presión atmosférica. Mediante el uso de los programas Aermed View y AERMOD, se demostró la dispersión de los gases alrededor de los puntos de emisión seleccionados en la planta de tratamiento. Al Aermet View se le incorporaron los parámetros de rugosidad superficial, la proporción de Bowen y el albedo para una zona rural. Los datos recolectados se incluyeron en AERMOD. [Resultados] La concentración de los gases emitidos por la planta se encuentra por debajo de los valores de percepción de estas sustancias, 0,70 µg/m3 (< 0,50 ppb) para el H2S y 26,6 µg/m3 (< 35,5 ppb) para el NH3. Se determinó que el canal de vertido es la fuente principal de emisión. Los gases generados se dispersaron hacia las comunidades vecinas de La Carpio, María Auxiliadora y Rincón Grande, en dirección noroeste; Carvajal Castro, Rossiter Carballo, Residencial Real Santamaría y Lagunilla, en dirección noreste, y la Comisión Nacional de Emergencia, en dirección sur. Los valores de error se encontraron en un ámbito entre el 5 % y el 48 % para el H2S y entre el 8 % y el 75 % para el NH3. El índice de concordancia (IC) mostró una similitud entre los valores predichos y los valores observados, tanto para el H2S como para el NH3. [Conclusiones] Las emisiones gaseosas de H2S y NH3 provenientes del sistema de tratamiento de aguas residuales no representan un riesgo para la salud ni el medio ambiente, en las poblaciones cercanas.
... Their impact is dependent upon their concentration and odour threshold. The odour threshold is the concentration limit at which the associated aroma can be detected (Leonardos et al., 1969). The contribution of specific VOC to the aromatic profile is known as the Odour Activation Value (OAV) (Buttery, 1999). ...
In recent years, consumer demand for health benefitting, pleasant-tasting rapeseed oil has increased, and so has production. Ireland's climate and agricultural background can support the production of high-quality rapeseed oil. Volatile organic compounds (VOC) can give rise to highly distinctive flavours in rapeseed oils, produced during crop growth and generated during processing. This study performed VOC and sensory evaluation to determine if correlations exist. Samples of Irish rapeseed oils from 6 different producers were analysed. Compounds detected in the oil samples consisted of acids, alcohols, aldehydes, ketones, benzenes, esters, ether, terpenes, and sulphurs. While variations in whole volatile profiles were not considered significant, individual compounds and volatile classes were for hexanal, pentanal, ketones, acids, and sulphurs compounds. Correlations were observed between the VOCs detected and the sensory profile, which indicated the VOC content may influence an oil's sensory profile.
... Detection thresholds are commonly used in flavour chemistry and sensory science as a measure of the potency of flavour compounds. They are defined as the minimum concentration of a flavour compound at which its presence can be detected in a food or beverage, but this concept has also been applied to other research fields, such as air pollution (Leonardos, Kendall, & Barnard, 1969). Flavour compounds can be ranked according to their odour activity by comparing their concentration in a food and their detection threshold. ...
The interest of consumers towards alcohol-free beer (AFB) has increased over the last few years due to several motivations. However, some of them, such as those brewed by cold contact fermentation (CCF) show a characteristic aroma reminiscent of wort or malt, lacking the appreciated fruity flavour of their alcoholic counterparts. From the current literature, the Strecker aldehydes methional, 2- and 3-methylbutanal are responsible for this aroma. The aim of this PhD project was to identify the role of odour-active compounds in AFB and their contribution to the worty character, as well as to study the formation kinetics of them during malt kilning. By means of the sensomic approach, five key aroma compounds were identified, among 27 odour-active compounds. These were methional (boiled potato-like aroma), 3-methylbutanal (cocoa-like), (E)-β-damascenone (apple, jam-like), 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone (curry, spicy-like), and phenylacetaldehyde (floral, honey-like).As a part of the sensomic method, perception thresholds of the odour-active compounds were determined in an AFB-like matrix. Differences were observed between our threshold values, both ortho- and retronasal, and the values from the literature in water and ethanol/water mixtures. Moreover, the calculation method employed (best estimate threshold BET or logistic regression) and the presence of false positives had a significant impact on the final results.In the next part of the project, the formation of (E)-β-damascenone and Strecker aldehydes during malt kilning (isothermal curing stage at 65, 78 or 90 °C) was investigated. The former increased over time in malts kilned at 78 and 90 °C, whilst at 65 °C the trend was not very clear. During mashing and wort boiling, the amount of (E)-β-damascenone was affected by a compromise between formation and degradation/evaporation.The formation of five Strecker aldehydes (the four mentioned above and 2-methylpropanal) was monitored during the curing stage of malt kilning too. These compounds are formed during thermal processes by the Maillard reaction between reducing sugars and amino acids. Multi-response kinetic modelling was used to fit the analytical results to a mechanistic mathematical model. The model developed showed the importance of the formation of two intermediate compounds in the reaction of glucose and amino acids. The first group of intermediates was Amadori rearrangement products (ARP), whereas the second was a pool of short chain dicarbonyls, such as glyoxal and methylglyoxal, that were not determined analytically. The results from the kinetic parameters demonstrated the high sensitivity of the degradation of ARP to changes in temperature because of its high activation energy.The outcomes from this PhD may have a great importance for brewers and brewing scientists. The understanding of the role of flavour compounds in AFB is the starting point to design mitigation strategies for the formation of worty off-flavours and thus improve the beer’s organoleptic characteristics and consumer acceptability.
... According to the serial two-fold dilution used in the present study and because IDTs are known to be particularly low for trimethylamine 51,52 , 50 dilutions were needed for this odorant. ...
Odor hedonic perception (pleasant/unpleasant character) is considered as the first and one of the most prominent dimensions in olfaction and is known to depend on several parameters. Among them, the relation between the odorant concentration and the hedonic estimation has been widely studied. However, few studies have considered odor hedonic ratings (OHR) in relation to individual detection thresholds (IDT). Thus, the aim of this study was to determine olfactory detection thresholds and to describe hedonic rating variations from individual thresholds to higher concentrations. IDT were performed for two pleasant (apple and jasmine) and two unpleasant (durian and trimethylamine) odorant stimuli. The experimenter presented one by one in a randomized order, the different odorant concentrations above IDT. Participants rated odor hedonic valence of these stimuli on a visual analog scale. Results showed, except for trimethylamine, the same relationship between hedonic ratings and stimulus concentration, i.e., an increase of pleasantness (apple and jasmine)/unpleasantness (durian) ratings at low and middle concentrations followed by a plateau at high concentrations. Correlations between OHR and concentrations as well as between OHR and threshold steps were always significant. Moreover, comparisons between both conditions showed that the correlation coefficient was significantly higher for trimethylamine (and a trend for apple) when IDTs were considered, while no difference was found for jasmine and durian. Overall, results suggested that the relationship between OHR and IDT is odor specific. These findings contribute to explain the large variability of the hedonic tone (i.e., weakly vs. very pleasant, weakly vs. very unpleasant) at specific concentration in the general population and could serve future research in this field (e.g., olfactory preferences in nutrition studies, anhedonia in psychiatric disorders…).
... As a result, the olfactory threshold for CH3SH is extremely low, and it may be detected at only 0.00002 ppm in air [9]. However, higher odor thresholds from 0.001 to 0.002 ppm have also been reported [57,58]. The permissible exposure limit (PEL) for CH3SH set by the Occupational Safety and Health Administration (OSHA) is 10 parts per million, and the threshold limit value-time weighted average (TLV-TWA) set by the American Conference of Governmental Industrial Hygienists (ACGIH) is 0.5 parts per million [59]. ...
The present research was focused on the determination and removal of sulfur-containing
compounds in industrial emissions of liquefied petroleum gas purification processes in petrochem�ical plants located in the USA, Brazil, Colombia, Spain, and Italy. For the analysis of volatile sulfur
compounds (VSCs), an improved analytical methodology was implemented. The performance of
the method was evaluated for eight VSCs in a linear dynamic range between 0.1 and 50 ppm. The
concentrations of the eight VSCs in the deethanizer affluents ranged from 11 to 49 ppm for all the
studied plants, which exceed the limits specified by institutions and administrations in occupational
health and safety. The concentrations of the eight VSCs in the splitter affluents were lower than 4
ppm for all the considered plants. The emissions from each column depended upon its operating
rate, with the highest concentrations estimated at 45 TM kg−1 and the lowest ones at 25 TM kg−1. A
zeolite-packed prototype column was fitted at the outlet of the splitter and deethanizer columns to
reduce the environmental effect of the examined VSCs. This technique was verified and put into
practice on an industrial scale, obtaining VSC removal percentages of between 85 and 91%.
... The value of p was set at 0.4 (in a range from 0 to 1, depending on the compound) and was based on observations of the percentage of people who are able to identify the existence of H 2 S in a concentration range (Latos et al., 2011) apud (Amoore, 1985). The threshold concentration was set at 4.7 ppb (Leonardos et al., 1969). In a similar way, another relationship has been put forward to assess the annoyance caused by odors (Nicell, 2003) as detailed in Eq. 3. ...
A flare stack is an indispensable device in the oil and gas industry for allowing the safe combustion of gases into the atmosphere, especially during emergencies. However, it is not ideal for the routine disposal of gaseous waste, as it is subject to meteorological influences and poor operational control. In addition, it can be affected by toxic currents and thus pose a potential risk of odors; in view of this, an assessment must be made of the implications of burning on the environment and health. Atmospheric dispersion modelling has proved to be a very useful tool for this purpose. In light of this, an attempt has been made in this work to evaluate the impact of H2S on the well-being (odor perception) of the community in the surrounding area of an oil refinery, where the temporary burning of rich gas in H2S occurs in a chemical flare, and operational factors have an influence on atmospheric dispersion. The odor assessment was carried out with the aid of AERMOD which was adapted to estimate the maximum odor concentration for very short periods by means of peak-to-mean ratios. The results showed that H2S detection can reach a probability rate of 42% at 3.5 km distance from the flare (in a time interval of 5 s) with a relatively high degree of annoyance (3.0 AU). However, some operational procedures can reduce the probability of odor detection to 29% and the degree of annoyance to 2.6 AU.
... Trimethylamine (TMA) is a highly volatile small tertiary amine produced in patients with chronic kidney disease (CKD) (discussed earlier in Chapter 1). TMA has a distinctive "fishy" odour, and can be detected by the human nose down to 0.21 ppb (92), therefore in theory one has the means to detect CKD without a sensor. However, in practice, this would not be an objective measure and could not be used for the diagnosis of CKD. ...
There is an unmet medical need for the effective detection of early-stage kidney disease as many current techniques lack the accuracy to detect it early on. Therefore, most patients are diagnosed at a later phase when irreversible kidney damage has already been done. Blood tests typically detect serum creatinine however this can be unreliable and require laboratory and trained personnel. Within this thesis a metal oxide gas sensor has been developed to detect the volatile organic compound (VOC) trimethylamine (TMA), known to be elevated in early disease stages, via patients expired breath. Aerosol assisted chemical vapour deposition (AACVD) was chosen for its simplicity and ability to produce thin reproducible films without vacuum. Consequently molybdenum oxide (MoO3) thin films were successfully deposited by AACVD and used for the sensing of TMA. Films were further modified with cerium and gold to increase the sensitivity and performance of the sensors, and a variety of characterisation techniques were used such as scanning electron microscopy with coupled energy dispersive spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy to explore the crystallinity and properties of the optimised sensor films. The sensor was then evaluated successfully using simulated kidney disease patient breath in order to test its feasibility in practice. Finally, initial studies into the use of silicon carbide-tungsten core fibres were investigated as a potential for a next generation self-heating integrated substrate for molybdenum oxide sensors and the detection of TMA gas.
... Odours have been defined as sensations which occur when chemical substances, referred to as odorants, are inhaled through the nose (Brancher, et al., 2016). These include sulfur compounds, nitrogen compounds and volatile organic compounds (Leonardos et al., 1969). Exposure to odourous emissions can result in negative effects on public and individual health (Brancher et (Brancher, et al., 2016). ...
Public spaces of planned residential neighbourhoods in Nairobi are characterized with odour associated with rotting garbage, blocked storm water drains, poor surface drainage and broken-down sewerage systems. Whereas urban management agencies are responsible for the delivery of desirable public space environments, this has not been successful. This study was designed to find out whether there could be public space characteristics influencing this problem. Space syntax and structured observation were used in data collection. Multiple regression analysis established that relative depth of axial space, adjacency and permeability; proportion of buildings with setbacks; percentage of space that is tarmacked; plot ratio; frequency of informal businesses; and tree canopy height significantly explain odour in public space. These characteristics should be considered in residential neighbourhood layout to counter the problem of odour and promote public space environmental sustainability.
... The types and dynamic ranges of smells detected by animals is vast. For example, it is estimated that the human nose can detect up to 1 trillion different scents [1], some of them at concentrations of less than one part per billion [2]. This range of detection is accomplished by a relatively small number (~350) of distinct olfactory receptors on olfactory sensory neurons (OSNs) that trigger ion channels and act as signal transducers [3]. ...
The sense of smell (olfaction) is one of the most important senses for animals including humans. Despite significant advances in the understanding mechanism of olfaction, currently, there are no objective non-invasive methods that can identify loss of smell. Covid-19-related loss of smell has highlighted the need to develop methods that can identify loss of olfaction. Voltage-gated sodium channel 1.7 (NaV1.7) plays a critical role in olfaction by aiding the signal propagation to the olfactory bulb. We have identified several conditions such as chronic inflammation and viral infections such as Covid-19 that lead to loss of smell correlate with downregulation of NaV1.7 expression at transcript and protein levels in the olfactory epithelium. Leveraging this knowledge, we have developed a novel fluorescent probe Tsp1a-IR800 that targets NaV1.7. Using fluorescence imaging we can objectively measure the loss of sense of smell in live animals non-invasively. We also demonstrate that our non-invasive method is semiquantitative because the loss of fluorescence intensity correlates with the level of smell loss. Our results indicate, that our probe Tsp1a-IR800, can objectively diagnose anosmia in animal and human subjects using infrared fluorescence. We believe this method to non-invasively diagnose loss of smell objectively is a significant advancement in relation to current methods that rely on highly subjective behavioral studies and can aid in studying olfaction loss and the development of therapeutic interventions.
... The situation is much more difficult to interpret in the case of VOCs, which cover a wide range of compounds having carbon in their structure. In the case of studies carried out in biogas plants processing municipal waste, during which besides olfactometry and detector also gas chromatography was used [20], the dominating VOCs were the compounds styrene (OT = 0.047 ppm [75]), phenol (OT = 0.048 ppm [76]) and toluene (OT = 0.33 ppm [77]), which, apart from unpleasant odour, are also characterized by a dangerous effect on human health and life. Analyzing the results presented and the characteristics of the compounds, it can be concluded that the recultivation activities carried out on the site do not comply with the decision issued by the state authority or with the definition of recultivation. ...
Mineral excavation is a common process throughout the world. The open pits remaining after the closure of a mine require well-considered and meticulous reclamation activities aimed at restoring the environmental properties of a given area. The inspections carried out in Poland indicate numerous irregularities in implementing the reclamation process. The research in this study was conducted in six measurement series and includes both chemical and olfactometry determinations by devices: multisensor portable gas detector and field olfactometer. Statistical analysis of the results obtained show high concentrations in ambient air of both chemical compounds (NH3, VOCs, H2S, CH3SH) and odour, excluding the possibility of occurrence in the pit of only waste types contained in the administrative decision on reclamation. In addition to the unpleasant odour, the listed compounds can have dangerous effects on the health and life of living organisms. This paper presents a suitable method of control and detection of irregularities in the conducted processes. The main advantage is the relatively low cost of purchasing sensors and field olfactometers compared to other devices, and the possibility to test the polluted air in situ, without the risk of chemical processes occurring during transport of gas samples to the laboratory.
... Odor detection threshold (ODT) is a notion that describes the concentration of a stimulus above which it can be positively identified and below which it becomes unnoticeable (Leonardos et al., 1969). The measured ODTs of volatile constituents demonstrate their intensity/potency. ...
Wine aroma, which stems from complex perceptual and cognitive processes, is initially driven by a multitude of naturally occurring volatile constituents. Its interpretation depends on the characterization of relevant volatile constituents. With large numbers of volatile constituents already identified, the search for unknown volatiles in wine has become increasingly challenging. However, the opportunities to discover unknown volatile compounds contributing to the wine volatilome are still of great interest, as demonstrated by the recent identification of highly odorous trace (µg/L) to ultra‐trace (ng/L) volatile compounds in wine. This review provides an overview of both existing strategies and future directions on identifying unknown volatile constituents in wine. Chemical identification, including sample extraction, fractionation, gas chromatography, olfactometry, and mass spectrometry, is comprehensively covered. In addition, this review also focuses on aspects related to sensory‐guided wine selection, authentic reference standards, artifacts and interferences, and the evaluation of the sensory significance of discovered wine volatiles. Powerful key volatile odorants present at ultra‐trace levels, for which these analytical approaches have been successfully applied, are discussed. Research areas where novel wine volatiles are likely to be identified are pointed out. The importance of perceptual interaction phenomena is emphasized. Finally, future avenues for the exploration of yet unknown wine volatiles by coupling analytical approaches and sensory evaluation are suggested.
... Totally, there are more than one hundred molecules, of which the most representatives in sweet basil are considered linalool, estragole, eugenol and eucalyptol (1,8-cineole) [7,10]. The content of these molecules could give a preliminary evaluation of different basil flavour profiles, while a more accurate evaluation of the final aroma will also consider the concentrations of other minor components, mainly the molecules that have a low odour threshold [11,12]. The odour threshold is defined as the lowest concentration of a molecule that could be perceived by olfaction. ...
Basil is a plant known worldwide for its culinary and health attributes. It counts more than a hundred and fifty species and many more chemo-types due to its easy cross-breeds. Each species and each chemo-type have a typical aroma pattern and selecting the proper one is crucial for the food industry. Twelve basil varieties have been studied over three years (2018–2020), as have four different cuts. To characterize the aroma profile, nine typical basil flavour molecules have been selected using a gas chromatography–mass spectrometry coupled with an olfactometer (GC–MS/O). The concentrations of the nine selected molecules were measured by an ultra-fast CG e-nose and Principal Component Analysis (PCA) was applied to detect possible differences among the samples. The PCA results highlighted differences between harvesting years, mainly for 2018, whereas no observable clusters were found concerning varieties and cuts, probably due to the combined effects of the investigated factors. For this reason, the ANOVA Simultaneous Component Analysis (ASCA) methodology was applied on a balanced a posteriori designed dataset. All the considered factors and interactions were statistically significant (p < 0.05) in explaining differences between the basil aroma profiles, with more relevant effects of variety and year.
... The experimental evaluation of the OT is strictly correlated with several factors, such as the presentation mode of the stimulus to the observer, the influence of extraneous odorants, the type of observer used, the definition of the odor response and the chemical purity of the odorant. [74] As a result, for a single molecule, several different values of OT can be found in the literature and technical databases, or it is even more common to find a range of OT concentration values rather than a single value. Indeed, the research and selection of proper OT values has been a complex issue of this work. ...
The scope of this work is the evaluation of the non-carcinogenic occupational risk related to foundry emissions, focusing on the category of workers involved in olfactometric assessments. Odor pollution from industrial activities such as foundries is a serious environmental concern. Sensorial techniques (e.g. dynamic olfactometry, EN13725:2003) currently represent the preferred method for odor emission characterization. During olfactometric analyses, human assessors are directly exposed to the odor at increasing concentrations, thus requiring the assessment of the associated exposure risk to guarantee workers’ safety. This paper presents an investigation aiming to produce an inventory of compounds emitted from foundries together with their odor thresholds and toxicological limits (TLVs), with the final objective to propose a procedure for ensuring workers’ safety during olfactometric analyses. Looking at the database resulting from this study, among the >100 compounds emitted by foundries, 8 have a maximum concentration above their TLV. Among those, ammonia, H2S, phenol, toluene and trimethylamine, produce an odor stimulus before they reach a toxic concentration, thus not representing a risk for olfactometric workers. Benzene, formaldehyde and SO2 are identified as the most critical compounds because they may reach toxic concentrations in foundry emissions, and they start being perceived by humans above their TLV. The proposed procedure entails a minimum dilution factor of 27’000 to be applied to odor samples analyzed by olfactometry, which however might result inapplicable in practical cases, thus pointing out the necessity to adopt chemical measurements to investigate specifically the concentration of the most critical compounds identified in this study.
... Beany flavor/odor was detected from the non-dairy creamer analogs/mimics at 0 month of storage, but disappeared after 3 months of storage probably due to the decrease in aldehydes during the storage (Table 6). Ketones were the major volatiles at 0-month storage, but they had no effect on the odor of the non-dairy creamer analogs/mimics because of they have high thresholds [42]. Takahashi et al [43] reported that aldehydes (hexanal and pentanal) are responsible for the beany flavor. ...
... [41] Of those, sulfur compounds are the ones with very low threshold levels. [42] Consequently, although sulfur compounds are found only in trace quantities in hop oil, their impact on hop and beer aroma is considerable. They are undesirable in brewing as they can have a detrimental effect on beer aroma. ...
Hop cones (Humulus lupulus L.), or more specifically the lupulin glands, hold the reason for the specific, pleasant aroma of hops – its essential oil. The hops themselves, or the extracted oil, are used almost exclusively in beer production. The essential oil is an indispensable part of beer and is responsible for its characteristic aroma. However, hop essential oil (HEO) also has a broad range of positive effects on human health and is a potential natural pesticide that has no harmful impacts on humans. This review summarizes basic information about HEO, including its chemical composition and methods for extraction and analysis, while also providing a comprehensive overview of the contribution to beer aroma, health, and insecticide applications for this versatile essential oil.
... These compounds usually have a low detection threshold (e.g. 0.001 ppb for ethanethiol in humans (Leonardos et al., 1969)), that was largely trespassed in the measurements. Altogether, these odorous molecules could act as an aposematic signal to predators, advertising the toad's toxicity caused by co-secreted bioactive peptides. ...
1. Chemical sensing in vertebrates is crucial in their lives, and efforts are undertaken towards deciphering their chemical language. Volatile organic compounds (VOCs) is a group of chemicals believed to play an essential role in a wide variety of animal interactions. Therefore, understanding what animals sense themselves and untangling the ecological role of their volatile cues can be accomplished by analysing VOC emissions. A Proton-Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-TOF-MS) is an instrument that measures VOCs in real-time in an air sample. Since this technique acts as a hyper-sensitive ‘nose’ it has a similar potential in deciphering the chemical language of vertebrates.
2. Here, we validate the use of PTR-TOF-MS as a tool to measure VOCs from vertebrates, which in turn will help resolve vertebrate interactions through VOCs. The instrument monitors and records the full spectrum of VOCs emitted by an individual with a high accuracy and low detection limit, including transient VOC emissions. We propose and test diverse measuring configurations that allow for measurement of VOC emissions from different vertebrates and their exudates: full body, specific parts of the body, urine and femoral pores. In addition, we test configurations for sudden and short-lasting processes as VOCs emitted during adder skin shedding as well as the emissions of skin secretions upon mechanical and physiological stimulation in amphibia. Our configurations work in tandem with Gas Chromatography Mass Spectrometry (GC-MS) to allow compound structure verification.
3. We discuss the configurations and methodologies used and conclude with recommendations for further studies, such as the choice of chamber size and flow. We also report the results of the measurements on vertebrates —that are novel to science— and discuss their ecological meaning.
4. We argue that PTR-TOF-MS has a high potential to resolve important unanswered questions in vertebrate chemical ecology with great adaptability to a wide range of experimental setups. If combined with a structure verification tool, such as GC-MS, the creative deployment of PTR-TOF-MS in various future study designs will lead to the identification of ecologically relevant VOCs.
... Odor thresholds in the water of compounds were taken from the literature. [18,19] ...
Volatile compounds in fresh and dried eels were investigated. Electronic nose (E-nose), headspace solid-phase microextraction combined with gas chromatography–mass spectrometry (HS–SPME–GC–MS), and relative odor activity value (ROAV) were applied to distinguish odors between fresh and dried eels. Results showed that E-nose could effectively distinguish the aroma among fresh eels, eels dried under 35°C and 12°C, and different drying methods had a significant influence on nitrogen oxides and methane in volatile compounds of dried eels. Total 37 and 28 volatile compounds detected in dried and fresh eel, respectively, were remarkably different. Relative odor activity values (ROAV) identified hexanal, nonanal, benzaldehyde, octanal, and 1-octen-3-ol as key flavor compounds in both fresh and dried eels. However, a serial of compounds, including 2-ethylfuran, 2,3-octanedione, (E, Z)-2,6-nonadienal, D-limonene, and 2-Zn-pentylfuran, added the sweet and meaty flavor of dried eel and neutralized the original strong grassy and fishy taste of fresh eel, primarily led to the difference in their odors.
... A further significant impact related to VOCs is odor emission, which often causes a strong and persistent annoyance for the population [12]. In more detail, odor is the property of a substance, or rather of a mixture of substances, capable of triggering the sensation of smell [13][14][15][16]. This aspect is the subject of increasing attention for the public administration and could be translated into consent decrease and economic loss for the companies responsible. ...
The construction and building field represents a key sector for the recent Circular Economy Action Plan (March 2020). Therefore, the production of low impact materials represents an essential step towards the implementation of a sustainable market. In this regard, the present paper focused on the production of painting wooden products for interior design. These industrial processes include an essential phase consisting of the reduction of odor emissions, which produce negative impacts on the environment and a persistent annoyance for the population close to the facilities. The main cause of the odor emissions in wood painting manufacturing is the production of volatile organic compounds (VOCs). In this context, the present research aimed to develop an innovative process able to combine the use of lower impact paints with a more efficient UV system for the abatement of the emissions.
... The cutting of the glass foams prepared in this study does not release any odour. The human olfactory organs are very sensitive to H 2 S, and the limit of recognising the odour of H 2 S is 0.0047 ppm volume (μg/m 3 ) [65]. Hence, the glass foams prepared in this work contain undetectable amount of H 2 S. ...
Cathode ray tube (CRT) panel glass is processed into glass foams by using carbon and Mn3O4 as foaming agents. We investigate the foaming ability and foaming mechanism of the mixture by varying the composition and the temperature. Carbon load of 5 wt% inhibits the sintering of the glass powder, while 2 wt% carbon promotes the coalescence of pores during foaming. Carbon load of ≤0.4 wt% is suitable for achieving low density foams (0.15–0.23 g cm⁻³) with closed pores (75–100%). Foaming is initiated by the reaction between carbon and Mn3O4 and this is the main source of melt expansion. Reduction of cations in the glass melt, including Mn³⁺ dissolved from Mn3O4, makes an important contribution to the melt foaming at >800 °C. The main gaseous product is CO2 (67–95 vol%). CO appears above 800 °C and the concentration increases with temperature.
... Calculating the DoT values based on the reported concentrations (Macatangay & Bruce, 2010) and their associated odor thresholds (as reported in Nagata, 2003), the DoTs range from 2 for acrolein to 117 for acetaldehyde (spanning propanal, butanal, pentanal, hexanal, and heptanal); by comparison, the derived DoT value for n-butanol is 1.5, that is, with a concentration only slightly above the odor threshold. In this context, two important aspects should be noted: first that odor threshold values reported in the literature vary widely (see, e.g., Leonardos, Kendall, & Barnard, 1969) whereby taking alternative literature values delivers DoT values below 1; and second, odor thresholds are not equivalent to perception thresholds, that is, the threshold at which an odor can be perceived (identified), which can be several factors higher. Nevertheless, based on these calculated DoT values derived from the data available, it can be concluded that a background odor is present onboard the ISS and some constituents of the background odor are potentially detectable by astronauts. ...
The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to Mars would take 30 to 36 months to complete, there is concern that a calorie deficit over this period may lead to adverse effects in crew members. The key question is why astronauts undereat when they have a supply of food designed to fully deliver their nutritional needs. This review focuses on evidence from astronauts that foods taste different in space, compared to on Earth. The underlying hypothesis is that conditions in space may change the perceived flavor of the food, and this flavor change may, in turn, lead to underconsumption by astronauts. The key areas investigated in this review for their potential impact on food intake are the effects of food shelf life, physiological changes, noise, air and water quality on the perception of food flavor, as well as the link between food flavor and food intake.
... Calculating the DoT values based on the reported concentrations (Macatangay & Bruce, 2010) and their associated odor thresholds (as reported in Nagata, 2003), the DoTs range from 2 for acrolein to 117 for acetaldehyde (spanning propanal, butanal, pentanal, hexanal, and heptanal); by comparison, the derived DoT value for n-butanol is 1.5, that is, with a concentration only slightly above the odor threshold. In this context, two important aspects should be noted: first that odor threshold values reported in the literature vary widely (see, e.g., Leonardos, Kendall, & Barnard, 1969) whereby taking alternative literature values delivers DoT values below 1; and second, odor thresholds are not equivalent to perception thresholds, that is, the threshold at which an odor can be perceived (identified), which can be several factors higher. Nevertheless, based on these calculated DoT values derived from the data available, it can be concluded that a background odor is present onboard the ISS and some constituents of the background odor are potentially detectable by astronauts. ...
The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to Mars would take 30 to 36 months to complete, there is concern that a calorie deficit over this period may lead to adverse effects in crew members. The key question is why astronauts undereat when they have a supply of food designed to fully deliver their nutritional needs. This review focuses on evidence from astronauts that foods taste different in space, compared to on Earth. The underlying hypothesis is that conditions in space may change the perceived flavor of the food, and this flavor change may, in turn, lead to underconsumption by astronauts. The key areas investigated in this review for their potential impact on food intake are the effects of food shelf life, physiological changes, noise, air and water quality on the perception of food flavor, as well as the link between food flavor and food intake.
... Calculating the DoT values based on the reported concentrations (Macatangay & Bruce, 2010) and their associated odor thresholds (as reported in Nagata, 2003), the DoTs range from 2 for acrolein to 117 for acetaldehyde (spanning propanal, butanal, pentanal, hexanal, and heptanal); by comparison, the derived DoT value for n-butanol is 1.5, that is, with a concentration only slightly above the odor threshold. In this context, two important aspects should be noted: first that odor threshold values reported in the literature vary widely (see, e.g., Leonardos, Kendall, & Barnard, 1969) whereby taking alternative literature values delivers DoT values below 1; and second, odor thresholds are not equivalent to perception thresholds, that is, the threshold at which an odor can be perceived (identified), which can be several factors higher. Nevertheless, based on these calculated DoT values derived from the data available, it can be concluded that a background odor is present onboard the ISS and some constituents of the background odor are potentially detectable by astronauts. ...
Andrew Taylor, Jonathan Beauchamp, Loic Briand, Victor Demaria Pesce, Martina Heer, Thomas Hummel, Scott McGrane, Christian Margot, Serge Pieters, Paola Pittia and Charles Spence consider the role of food flavour in combatting under-consumption of nutrients by astronauts on the Mars expedition.
Several billion pounds of ketones are produced annually for industrial use in the United States and worldwide. Those with the highest production volumes include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4‐hydroxy‐4‐methyl‐2‐pentanone, isophorone, mesityl oxide, and acetophenone. Common methods used to manufacture ketones include aliphatic hydrocarbon oxidation, alcohol dehydration with subsequent oxidation, dehydrogenation of phenol, alkyl aromatic hydrocarbon oxidation, and condensation reactions. Ketones are commonly used in industry as solvents, extractants, chemical intermediates, and, to a lesser extent, flavor and fragrance ingredients. Although a common effect of excessive ketone exposure is CNS depression some ketones have pulmonary effects that are well below levels that cause acute CNS effects. For example, ketones such as diacetyl and chemically similar chemicals used for flavoring foods, coffee, and e‐cigarettes provide opportunities for widespread exposure and very debilitating pulmonary disease including bronchiolitis obliterans.
Ketones of carbon number 6–13 are important commercial and industrial materials. Their primary use is as solvents that find use in numerous products and industrial applications. Due to their volatility, environmental regulations have been directed at restricting emissions, particularly to the atmosphere. A number of the ketones discussed in this chapter not only can undergo photochemical transformations that contribute to their abiotic degradation but may also contribute to the formation of smog. Regulations limiting or prohibiting release of materials that may contribute to smog formation are leading to reductions in the use of some of these materials. The ketones covered in this chapter are mainly of concern due to inhalation and dermal exposure routes. Acute exposure to high vapor concentrations of these materials may result in narcosis; however, such exposures are rare except in cases of accidents. Repeated exposure to certain of these ketones may result in peripheral neuropathy or hepatic effects.
Disposal of sewage sludge, a by-product of wastewater treatment, is one of the most intractable problems for environmental protection industry. The odorous gases discharged from sludge drying has seriously affected the life quality of residents, causing growing public concern of its odor pollution. The previous studies mainly focused on municipal sludge. In this research, samples of distillery sludge, municipal sludge and pharmaceutical sludge were collected and dried under identical conditions to compare the pollutant release characteristics of municipal sludge and industrial sludge. Throughout the drying process, the amounts of emitted ammonia, hydrogen sulfide and benzene series were detected every 10 min, and the odor pollution of different drying exhaust was quantitatively evaluated using odor threshold. The results of the drying experiments showed that the odor problem of municipal sludge was significantly worse compared to industrial sludge. The maximum odor index during thermal drying of municipal sludge was 15,332, which was 3 times that of distillery sludge and 24 times that of pharmaceutical sludge. The odor pollution caused by benzene series was negligible for any type of sludge, but drying process should be ceased before the moisture content falls to 10% to reduce their carcinogenic risk to exposed individuals.
The technical instructions on air quality serve to protect the general public and the neighbourhood against harmful effects on the environment caused by air pollution and to take precautions against harmful effects on the environment caused by air pollution in order to achieve a high level of protection for the environment as a whole. General principles of microbial exhaust air purification are: Biofilter, bioscrubbers, trickling filter scrubbers, and membrane reactors.
Odor pollution has become a global environmental issue of increasing concern in recent years. Odor measurements are the basis of assessing and solving odor problems. Olfactory and chemical analysis can be used for odor and odorant measurements. Olfactory analysis reflects the subjective perception of human, and chemical analysis reveals the chemical composition of odors. As an alternative to olfactory analysis, odor prediction methods have been developed based on chemical and olfactory analysis results. The combination of olfactory and chemical analysis is the best way to control odor pollution, evaluate the performances of the technologies, and predict odor. However, there are still some limitations and obstacles for each method, their combination, and the prediction. Here, we present an overview of odor measurement and prediction. Different olfactory analysis methods (namely, the dynamic olfactometry method and the triangle odor bag method) are compared in detail, the latest revisions of the standard olfactometry methods are summarized, and the uncertainties of olfactory measurement results (i.e., the odor thresholds) are analyzed. The researches, applications, and limitations of chemical analysis and odor prediction are introduced and discussed. Finally, the development and application of odor databases and algorithms for optimizing odor measurement and prediction methods are prospected, and a preliminary framework for an odor database is proposed. This review is expected to provide insights into odor measurement and prediction.
We hereby present the fabrication of simple and efficient humidity and ammonia sensors based on a chemiresistor design employing a differential measurement technique. Interdigitated electrodes are connected via PEDOT:PSS or P3HT polymers and a reproducible and scalable fabrication procedure is presented. This procedure utilizes pneumatic nozzle printing instead of drop or spin‐based processes and includes an optimized encapsulation procedure and material for sealing the reference electrodes. The suitability of the NH3 sensor for quantifying ammonia in a range of 2 to 100 ppm within a period of several months is furthermore presented. The developed humidity sensor is operational for several months in a humidity range between 10 and 60% RH. Once this range is exceeded, a sensor decay by irreversible saturation can be observed. Based on the low fabrication costs of the sensors (~0.5 $ when ordering 1000 pcs of the platform + printing work), they provide a very attractive tool for industrial humidity and ammonia sensing applications. We hereby present the fabrication of simple and efficient humidity and ammonia sensors based on a chemiresistor chip. The combination of PEDOT:PSS and P3HT as classical conductive polymers with pneumatic nozzle printing and simple chemiresistors was optimized to yield highly reproducible, stable and functional sensors. The parallel detailed optimization of all system parameters finally yielded an attractive and economic sensing platform for ammonia and humidity sensing purposes.
Although several microalgae species have been used for industrial purposes, it is generally difficult to visually observe their growth conditions during cultivation. Our group has attempted to develop a way to control algae cultivation, using a method we refer to as “Odor Sensing Cultivation” (OSC). This is a new and simple observation method that is based on the odors produced by algae. In this study, as a representative microalgal species, Scenedesmus sp. was employed. Odors produced from its culture were investigated by olfactory evaluation, chemical identification, and “e-nose” analysis. As a result of olfactory evaluation, “green tea”, “sweet”, and “fishy” were the characteristic odors identified from this species. In the chemical analysis, the odors from this species were identified as 1-nonanal, α-ionone, β-ionone, and tentatively identified as 2-undecenal and acetic acid. Based on the QCM-type e-nose analysis, the odors from this alga and the control medium could be separated. These results suggest that the OSC is applicable as a practical technique for production of this species.
The “stored off-flavor” is one of the unfavorable flavors released by several citrus species when stored at low temperature. The degradation in quality due to the stored off-flavor has been a problem with satsuma mandarins (Citrus unshiu Marc.), a major citrus species in Japan. However, information about this problem is fragmented. To develop a method for determining which satsuma mandarins are suffering from stored off-flavors, our group attempted to define the odor characteristics of stored off-flavors through olfactory evaluation and to identify the compounds responsible for off-flavors using samples of satsuma mandarins stored at low temperature. We found that the odor characteristic “grass-like” was stronger in samples stored at a lower temperature (4 °C) than those stored at room temperature (25 °C). The grass-like odor was defined as the stored off-flavor of satsuma mandarins. Following a chemical analysis using gas chromatogram-olfactometry (GC-O) and GC-MS, the stored off-flavor, grass-like, was identified as p-cymenene.
Due to the fact that only a human can judge the objectionability of an odor, organoleptic examination (sniffing and scoring oral odor) was used as a reference standard of oral halitosis measurement. However, there are several problems that make the diagnostic value of organoleptic examination questionable.
There is no universally accepted, precise definition, standardization and calibration in organoleptic examination, including scoring, scaling or safety protocols. Standardization, calibration, reproducibility, reliability, objectivity, specificity, accuracy, sensitivity of organoleptic measurement are doubtful. It is extremely subjective, emotional, instinctive, intuitive, speculative, hedonic or highly flexible. Also it is found repulsive, primitive and moreover even shame is experienced by patients or examiners. Nonstandard protocols on pre-measurement, scoring, scaling, and training processes may cause misinterpretation or misdiagnose since it depends on examiner’s emotional mood, gender, ethnicity, odor detection spectrum, threshold, and even climate conditions. It is not gold standard, even not standard.
It is difficult to recognize, identify or focus on a particular gas among thousands in the breath. Organoleptic examination may not be necessary due to not being a good diagnostic tool for halitosis. There may be infection risk for sniffer or patient. Moreover, female examiners may have disadvantages in olfactory accuracy during organoleptic examination, since menstruation, pregnancy, menopause may alter their odor sensation. Also, the age, limits reliability of examiners due to age-related smell loss. According to the psychophysics laws, the human nose can recognize odors logarithmically.
There is no reason to think that scoring the oral malodor by sniffing the mouth of the patients obtains sufficient evidence for the diagnosis of halitosis. Portable multi-gas detectors, electronic noses can be suggested as alternative instead of sniffing patients.
This is the first paper in the literature to criticize organoleptic examination, revalues health risks, inconsistencies in assesment protocols.
Water is a critical commodity and a strategic compound for health and economic prosperity. Its availability is key for sustainable industrial activities. This paper presents a novel energy efficient Forward Osmosis-Freeze Concentration (FO-FC) hybrid process able to recover water as ice. In this process, FO operating with a soluble inorganic draw solution, can reduce the volume of aqueous streams by spontaneous osmotic dewatering. Water is in turn recovered as ice by FC, while simultaneously concentrating and regenerating the draw solution. Water recovery by freezing is up to 7 times more energy efficient thermodynamically than by distillation. The water recovered in FO-FC is not intended for drinking purposes, but rather for reuse in industrial operations, in an effort to minimize industrial fresh water intakes. We tested both DI water and a hydrometallurgical effluent as the feed solution in FO-FC. Our FO results, suggest an increase in membrane selectivity as the operating temperature decreases, using MgCl2 as the draw solution and DI water as the feed solution in FO. Further, a significant rejection, namely >90%, of the elements dissolved in the hydrometallurgical effluent used as the feed solution was achieved. Our FC results indicate >66% water recovery as ice with 80–96% recovery efficiency and 0.12 ± 0.05 mol/kg impurities in the ice. Finally, the regenerated concentrated draw solution concentration is 2.8-4× higher compared to the dilute draw solution and is therefore suitable to be reused in the FO step.
This study reports the efficiency of sepiolite in reducing odorous volatile organic compounds (VOCs) from natural rubber. Natural rubber latex (NRL) films with various content of sepiolite were prepared, ranging from 0 to 2.0 parts per hundred rubbers. The presence of odous VOCs in neat NRL films and NRL/sepiolite films has been confirmed by using gas chromatography‐mass spectrometry. Most of odorous VOCs with odor detection threshold (ODT) of less than 0.1 ppm were significantly reduced in the presence of sepiolite. The result of dynamic olfactometry analysis also shows a negative correlation between odor concentration and the sepiolite content. The addition of 2.0 phr sepiolite in NRL/sepiolite‐T and NRL/sepiolite‐C reduced the odor concentration of NRL films by 69.1% and 59.4%, respectively. This proves that the mesoporous sepiolite‐T adsorbed more odorous VOCs in the NRL films, as compared to macroporous sepiolite‐C. Thus sepiolite‐T is a promising deodoriz er for NRL films due to its higher odorous VOCs adsorption potentials.
The potato-rot nematode Ditylenchus destructor (Tylenchida: Anguinidae) causes severe damage to garlic production in Japan. Since nematode-infested garlic is difficult to discriminate from healthy ones, it has been required to find a novel technique to identified nematode-infested garlic. To be able to identify nematode-infested garlic in a non-destructive way, here this study has introduced an analytical system of gas chromatography–olfactometry (GC-O) and GC-MS with heart-cut enrichment technique. The objective of this research was to identify the subjectively perceptible odors that derive from nematode-infested garlic and to evaluate the effectiveness of the novel analytical system. Several odor-activities associated with nematode-infested garlic were detected and were identified by the system. Allyl methyl sulfide, diallyl sulfide, allyl methyl disulfide, and eugenol were identified as major odor compounds in infested garlic. This result suggests that these distinctive odor compounds might be used as indicators to detect nematode-infested garlic in a non-destructive way.
Up to now, a large number of odorants could be identified in food or other natural or synthetical matrices, at times even as (undesired) by-products. Two prominent natural sources of odorous substances are fat and polyphenolic substances such as lignin, bringing about structurally diverse, yet potent and characteristic odorants, namely saturated and unsaturated aldehydes and ketones, as well as phenolic substances such as guaiacols. Despite decades of smell research, odor researchers are still in the process of unveiling potent odorants that await discovery both in nature as well as in modern products. However, this endeavor is nowadays more challenging than ever, as compounds with extraordinarily potent smell predominantly remain unknown as they mostly are present at ultra-trace level. To identify and characterize such unknown odor-active compounds, researchers nowadays commonly utilize a strategy of systematic structural design, considering characteristic smell features, formation pathways, and structural cues obtained from trace odorant analysis. Synthesizing a range of structurally modified targets together with determination of absolute odor thresholds in air and odor qualities then supports discovery of characteristic molecular features related to smell. This approach has been used in the present study for the investigation of different homologues series of fatty acid oxidation products as well as guaiacol derivatives. Besides the consideration of structure-odor correlations within this investigation, inter-individual differences in odor perception were taken into account. All analyses of odor thresholds in air and odor qualities were conducted by means of gas chromatography-olfactometry. The first part of the thesis addresses the investigation of odor properties of different homologues series of fatty acid oxidation products, which are partly already known (naturally occurring) odorants. Homologues series of alka-1,5-dien-3-ones, alk-1-en-3-ones, alka-1,5-dien-3-ols, and alk-1-en-3-ols were synthesized, and a total of 47 compounds has been investigated with regard to their odor properties. Thereby showing the successive odor quality change for the series of the alk-1-en-3-ols and alk-1-en-3-ones from pungent via metallic, vegetable-like over mushroom-like to citrus-like, soapy, or herb-like with increasing chain length. Two odor threshold minima were found for the six-carbon and for the eight- and nine-carbon odorants, both for the alkenols as well as the alkenals. For the alkadien-3-ols and their corresponding ketones the odor qualities did not change significantly. They elicit geranium-like, metallic odor impressions with an increasing tendency to a mushroom-like odor with increasing chain length. The lowest thresholds were found for the eight- and nine-carbon (Z)-compounds. 36 compounds of the 48 analyzed (E)- and (Z)-3-unsaturated volatile acids, alcohols, and aldehydes have been synthesized. In the series of (E)- and (Z)-3-alkenoic acids the odor quality changed successively from sweaty via plastic-like to sweaty and waxy. On the other hand, the odor qualities in the series of (E)- and (Z)-3-alken-1-ols, and (E)- and (Z)-3- alkenals changed from grassy, green to an overall citrus-like, fresh, soapy, and coriander-like odor with increasing chain length. Regarding their odor potencies, the lowest thresholds in air were found for (E)-3-heptenoic acid, (E)-3-hexenoic acid, and (E)-3-hexenal, and for (Z)-3-hexenal, (Z)-3-octenoic acid, and (Z)-3-octenal. Overall, the (Z)-3-compounds showed lower odor thresholds in air than the corresponding saturated compounds, which have been analyzed additionally, followed by the (E)-3- compounds. The second part of this thesis deals with the analysis and determination of odor thresholds and odor qualities of different guaiacol derivatives. Guaiacol and its derivatives are found in nature and are known for their typical smells: smoky, clovelike and vanilla-like. All investigated compounds, guaiacol and its alkylated, alkenylated, and methoxylated derivatives (26 compounds in total, 12 synthesized), elicited characteristic smoky/smoked ham-like, vanilla-like/sweet and/or clove-like smell impressions. The odor thresholds of the compounds were generally very low, ranging from 0.00018 to 111 ng/Lair. The lowest thresholds were determined for 5- methoxyguaiacol and guaiacol. Moreover, it could be shown that halogenated guaiacol derivatives likewise exhibit the typical guaiacol-like smells. They are not naturally occurring like their halogen-free companions, but formed during the processing of pulp, for instance, as undesired byproducts. 14 halogenated guaiacol derivatives have been analyzed, with five of them having been synthesized within this study. Overall, the investigated compounds elicited the already mentioned characteristic guaiacol-like smells, namely smoky, sweet, vanilla-like, but also medicinal and plaster-like. Their odor thresholds in air were also very low, ranging from 0.00072 to 23 ng/Lair. The lowest thresholds were found for 5- chloro- and 5-bromoguaiacol. The data collected within this study is intended to support future discovery of these compounds, both in nature as well as modern day-products. Further, the results are important for our general understanding of structure-odor correlations, but also reveal the at times high extent of inter-individual variation in smell perception in humans.
In this work was evaluated the effect of sequential inoculum of Hanseniaspora uvarum AS27 strain and a commercial Saccharomyces cerevisiae yeast on the physical–chemical and organoleptic features of Aglianico, a traditional red wine of Southern Italy. Four fermentation treatments on a pilot scale were performed. In fermentation treatment A, the alcoholic fermentation was spontaneously conducted by the indigenous yeasts present in grape must. In the fermentation treatments B and C were inoculated respectively S. cerevisiae FE and H. uvarum AS27 strains, as a single starter. The fermentation treatment D was initially inoculated with H. uvarum AS27, and S. cerevisiae strain was added after 72 h (sequential inoculation). Microbiological, physical–chemical parameters and sensory profiles of the wines have been defined. The results showed that the use of H. uvarum AS27, in sequential inoculum with S. cerevisiae FE, influenced the wine composition, enriching it in polyphenolic and volatile compounds. Further, the sensory evaluation showed that the use of H. uvarum AS27 strain, in co-culture with S. cerevisiae, gives the wine more pleasant characteristics. Therefore, the results have highlighted how the use of particular non-Saccharomyces yeasts can represent a biotechnological resource in red wine production.
In the current work, we investigate the mechanism of protonation of a Meisenheimer complex derived from picric acid and N,N′‐dicyclohexylcarbodiimide to provide the correct structure of the protonated Meisenheimer complex with the proper mechanism. A substituted picramide derivative has also been synthesised and characterised using various spectroscopic techniques to rule out the previously suggested protonated Meisenheimer complexes and support our proposed protonated structure. Various other investigations, including the interactions of the Meisenheimer complex with bulky electrophile Lawesson's reagent and bulky Lewis acid Eu(fod)3, were also carried out to support the mechanism of protonation. Various bulky bases as well as bases of different strengths were treated with the protonated Meisenheimer complex to support our proposed structure. Based on the protonation of the Meisenheimer complex, a general colorimetric volatile acid sensor has been designed, where a distinct colour change from orange to colourless was found to take place after protonation. The sensor can detect volatile acids both in the solid and in the solution state. The sensor was also applied to detect hydrogen chloride vapour in an automated manner using a smartphone, where information regarding the leakage position can be obtained through wireless communication. The detection limit of hydrogen chloride vapour was found to be 43.5 ppm.
The growing concerns on the sustainability of our planet have been leading the way to the development of alternative and renewable forms of energy. One example is the use of waste (e.g. sewage sludge, forest residues, agroindustry and food processing) to produce biogas. Comprised mostly of methane and carbon dioxide, it can be used as fuel in cogeneration systems, automotive mobility and domestic heating, among other applications. The increasing interest in the use of biogas has raised some questions regarding its quality for energy valorization. To start, the carbon dioxide content must be adjusted to upgrade the calorific power and economic value and then common potentially hazardous and even toxic impurities such as carbon monoxide, hydrogen sulfur, halogens, or ammonia should be removed to ensure a correct operation. Recently, a close attention was drawn to the presence of siloxanes. These widespread emerging pollutants compromise the use of biogas for energy production due to the formation of abrasive silicon oxides after combustion that deposit on and damage several engine parts. In addition, some of them are potentially toxic and persistent, involving a threat to humans and the environment, which increased drastically the literature devoted to them in the last years. This review provides a comprehensive assessment of the literature available on biogas impurities, presenting their main effects, sampling and analytical strategies, and concentrations. A summary of removal methodologies is also presented to address the technological challenges to cope with these unwanted compounds.
Acids are traditionally used in the production of environmentally-friendly cationic waterborne polyurethane dispersions. However, the effect of their conjugate bases on the final properties of waterborne polyurethanes has been rarely explored. In this study, the effect of different acids in tailoring the performance of bio-based cationic waterborne polyurethanes has been reported. Polyurethane films ranging from flexible elastomers to tough plastics can be obtained, and their properties can be simply controlled by the selection of the acids. The tunability of the hydrogen bonding strength confers the resulting polyurethane films enhanced multi-function, such as UV absorption, anticorrosion properties, and long-term antibacterial performance. These results represent a significant advancement over traditional techniques, providing a simple strategy to tailor the performance of cationic waterborne polyurethanes, and offering environmentally-friendly amino acid substitutes for commonly used acids, such as acetic acid, HCl, or glycolic acid. The methodology described here eliminates long-standing issues of PUs, such as irritating odor, corrosiveness, and air pollution.
The marine archaeological collection at the Mary Rose Museum contains wooden and metal artefacts displayed inside the same environment. This project investigated acidic emissions from archaeological wood to evaluate if they could cause chemical damage to the metal artefacts displayed alongside. Thermogravimetric analysis (TGA) was used to quantify biopolymers within sound and archaeological wood from the Mary Rose Museum. In addition to good relative agreement with traditional methods, TGA detailed chemical changes of the biopolymers and interactions with PEG, which could be used to evaluate future treatments. Solid phase micro extraction-gas chromatography-mass spectrometry identified PEG treatment of sound wood near eliminated emissions by acting as an impenetrable barrier. In contrast, PEG treated wooden artefacts from the Mary Rose Museum emitted a greater array of compounds compared to sound oak, including acetic acid and sulfur compounds, which corroded pure lead and silver, highlighting that emissions from archaeological wood can accelerate metal corrosion. However, environmental monitoring inside display cases at the Mary Rose Museum identified no relationship between the presence of archaeological wood and accelerated lead corrosion. Rather, smaller cases had higher acidic concentrations despite the cases being modern and having sodium hydroxide impregnated activated carbon charcoal filters to remove acidic vapours. The causes of corrosion are complex and depend on other factors, such as case materials, filtration systems and surface area. To enable quick risk assessments of display environments, a real-time acetic acid sensor was developed. This self-contained, affordable device used lead oxide coated quartz crystal microbalances, which quickly reacted to acetic acid vapour at ppm concentrations. Moreover, the rate of signal change correlated with volume of acetic acid injected into the test chamber. Therefore, this sensor design has potential to monitor acetic acid build up inside cases and further development is recommended to increase the repeatability of this sensor.
Enzyme-based conversion of marine biomass to high-quality peptide ingredients leaves a distinct smell of “fish” caused by the presence of trimethylamine, which limits their economic potential. We suggest an enzymatic solution for converting trimethylamine to the odorless trimethylamine N -oxide as a novel strategy to improve the smell quality of marine protein hydrolysates. Following a systematic investigation of 45 putative bacterial trimethylamine monooxygenases from several phyla, we expand the repertoire of known active trimethylamine monooxygenases. As a proof-of-concept, we demonstrate that three of these enzymes oxidized trimethylamine in an industry-relevant salmon protein hydrolysate. Our results add new oxidoreductases to the industrial biocatalytic toolbox and provide a new point of departure for enzyme process developments in marine biorefineries.
Halitosis is a common ailment concerning 15% to 60% of the human population. Halitosis can be divided into extra-oral halitosis (EOH) and intra-oral halitosis (IOH). The IOH is formed by volatile compounds, which are produced mainly by anaerobic bacteria. To these odorous substances belong volatile sulfur compounds (VSCs), aromatic compounds, amines, short-chain fatty or organic acids, alcohols, aliphatic compounds, aldehydes, and ketones. The most important VSCs are hydrogen sulfide, dimethyl sulfide, dimethyl disulfide, and methyl mercaptan. VSCs can be toxic for human cells even at low concentrations. The oral bacteria most related to halitosis are Actinomyces spp., Bacteroides spp., Dialister spp., Eubacterium spp., Fusobacterium spp., Leptotrichia spp., Peptostreptococcus spp., Porphyromonas spp., Prevotella spp., Selenomonas spp., Solobacterium spp., Tannerella forsythia, and Veillonella spp. Most bacteria that cause halitosis are responsible for periodontitis, but they can also affect the development of oral and digestive tract cancers. Malodorous agents responsible for carcinogenesis are hydrogen sulfide and acetaldehyde.
Air Pollution Abate-ment Manual—Physiological Effects Gosline
- E M Adams
Adams, E. M., "Air Pollution Abate-ment Manual—Physiological Effects," Gosline, ed., 22-26, Ch. 5, Manual Sheet p. 6, Manufacturing Chemists' Assoc, Washington (1951)
Methodology of the flavor profile
- L B Sjostrom
- S E Cairncross
- J F Caul
Sjostrom, L. B., Cairncross, S. E., and Caul, J. F., "Methodology of the flavor profile," Food Tech. XI, 20, (1957)
The design, construction, and use of an odor test room
- N Deininger
- R W Mckinley
Deininger, N., and McKinley, R. W., "The design, construction, and use of an odor test room," ASTM, Sp. Tech. Publ. No. 164 (1954)'; February 1969 Volume 19, No. 2