Odorous Compounds Research Articles

Olfactory Threshold Concentration of Two Typical Earthy-Musty Odour Compounds in Black Carps and Bighead Carps

2-methylisoboneol (2-MIB) and geosmin are two typical earthy-musty odour compounds in freshwater. In order to investigate the olfactory thresholds of 2-MIB and geosmin in black carp (Mylopharyngodon piceus) and bighead carp (Hypophthalmichthys nobilis), an improved and optimized pre-treatment method of adsorbing the earthy-musty odours combined with the technology of gas chromatography following microwave distillation-headspace solid-phase microextraction was developed. The fish back muscle samples were placed in vials with the 2-MIB/geosmin solution and reached the adsorption equilibrium. Some samples were evaluated by a panel of ten members using Flavour Profile Analysis (FPA) method, the remaining sample was used for instrumental analysis. In fish muscle blocks, it took 90 and 105 min to establish the absorption equilibrium of 2-MIB and geosmin, respectively. The olfactory thresholds of 2-MIB in the bodies of black carps and bighead carps were 0.35 μg/kg and 0.30 μg/kg, respectively, while the geosmin thresholds were 0.59 μg/kg and 0.51 μg/kg, respectively. The concentrations of 2-MIB and geosmin in the bodies of black carps were slightly higher than in bighead carps, which were probably caused by the differences in the body fat content and the volatility of 2-MIB and geosmin.

Effect of storage and field acidification on emissions of NH3, NMVOC, and odour from field applied slurry in winter conditions

Land spreading of liquid animal manure (slurry) is a major source of atmospheric emissions. Ammonia (NH3) emission is of concern, as it is one of the main contributors to ambient air pollution and nitrogen deposition. Storage and field acidification of the slurry prior to application is used to mitigate NH3 emission, but the effect of acidification on emissions of odorous non-methane volatile organic compounds (NMVOC) has not been investigated, and there is a scarcity of data investigating the effect of field acidification. Four field experiments, two with cattle slurry and two with pig slurry, were performed. Ammonia and NMVOC emissions were measured simultaneously in a system of dynamic chambers and online measurements by cavity ring-down spectroscopy (CRDS) and proton-transfer-reaction mass spectrometry (PTR-MS). The system allowed for a high time resolution and low variation. All four experiments were performed under cold conditions (<10°C average temperature). Storage and field acidification significantly lowered the NH3 emission by 79 ± 18% and 30 ± 6% on average, respectively. The NMVOC cumulative emission increased by 202 ± 133% and 17 ± 16% on average after storage and field acidification, respectively, even if the increase was only significant for storage acidification. Storage acidification significantly increased the emissions of odour at most measuring times. The increases of cumulative NMVOC emissions and odour was primarily caused by higher emissions of volatile fatty acids.

Enhanced Catalytic Ozonation for Eliminating CH3SH via Stable and Circular Electronic Metal-Support Interactions of Si-O-Mn Bonds with Low Mn Loading.

Catalytic ozonation of methyl mercaptan (CH3SH) can effectively control this unbearable odorous sulfur-containing volatile organic compound (S-VOC). The construction of an electronic metal-support interaction (EMSI) coordination structure to maximize the number of active sites and increase the intrinsic activity of active sites is an effective means to improve catalytic performance. In this work, the abundant Si-OH groups on PSBA-15 (SBA-15 before calcination) were used to anchor Mn to form a Si-O-Mn-based EMSI coordination structure. Detailed characterizations and theoretical simulations reveal that the strong EMSI effect significantly adjusts and stabilizes the electronic structure of Mn 3d states, resulting in an electron-rich center on the Si-O-Mn bond to promote the specific adsorption/activation of ozone (O3) and an electron-poor center on the (Si-O-)Mn-O bond to adsorb a large amount of CH3SH accompanied by its own oxidative degradation. In situ Raman and in situ Fourier transform infrared (FTIR) analyses identify that catalytic ozonation over 3.0Mn-PSBA generates atomic oxygen species (AOS/*O) and reactive oxygen species (ROS/•O2-) to achieve efficient decomposition of CH3SH into CO2/SO42-. Furthermore, the electrons obtained from CH3SH in electron-poor centers are transferred to maintain the redox cycle of Mn2+/3+ → Mn4+ → Mn2+/3+ through the internal bond bridge, thus accomplishing the efficient and stable degradation of CH3SH prolonged to 180 min. Therefore, the rational design of catalysts with abundant active sites and optimized inherent activity via the EMSI effect can provide significant potential to improve catalytic performance and eliminate odorous gases.

A novel strategy for discriminating different cultivation and screening odor and taste flavor compounds in Xinhui tangerine peel using E-nose, E-tongue, and chemometrics

A rapid strategy for discriminating Quanzhi (QZ) and Bozhi (BZ) of different cultivation of Xinhui tangerine peel was established by combining electronic nose, electronic tongue and chemometrics, which can be used as tool in the market to identify food fraud. 30 volatiles and 34 low molecular weight compounds of characteristic fingerprints of Xinhui tangerine peel of 108 samples were identified using GC–MS and UHPLC-Q-TOF-MS. Key compounds of BZ and QZ were screened and further compared by chemometrics. We discriminated odor and taste of BZ and QZ using electronic nose and electronic tongue, respectively. Our studies showed that β-myrcene, limonene, β-trans-Ocimene, γ-terpinene and terpinolene, etc, were screened the chief volatile flavor compounds by Spearman’s rank correlation. Hydroxymethyl furfural, hesperitin, nobiletin and tangeretin, etc, were screened the key taste flavor compounds based gray relational analysis and partial least squares regression. Our study provides further insight for quality evaluation of Xinhui tangerine peel.

Production of process flavorings from methionine, thiamine with d-xylose or dextrose by direct extrusion: Physical properties and volatile profiles.

The conventional method to produce process flavoring is non-continuous, time consuming, and generates a high volume of effluent. This research aimed to evaluate the use of methionine, thiamine, and reducing sugars to develop process flavorings by direct extrusion, as a potential alternative to the conventional method. The mixed substrates consisted of methionine: d-xylose (MX), methionine: dextrose (MD), thiamine: d-xylose (TX), and thiamine: dextrose (TD) at 80:20 w/w. Three barrel temperatures of the extruder were controlled at 65, 80, and 50°C, respectively, a screw speed of 30rpm and feed rate at 3 kg/hr. Appearance, pH, odor, and taste description of the product from each mixture were determined. Volatile compounds, possibly occurred from the Maillard reaction during the extrusion were analyzed by gas chromatography-mass spectrometry. The products exhibited different levels of meaty odor and bitter taste. Those obtained from MD showed the highest L* (lightness, 85.37) and frequency for just-about-right in terms of taste (33.33%) and odor (60.00%). Products from MX and MD presented the highest frequency for intense taste, and higher frequency for color compared to TX and TD. More volatile compounds were detected from the use of methionine than from thiamine. The key meaty odor compounds such as dimethyl disulfide, dimethyl trisulfide, methional, and methanethiol were found in the samples from MX and MD, while only dimethyl disulfide was detected in the mixture of TX and TD. Finally, the results demonstrated that direct extrusion reaction from methionine and d-xylose or dextrose is a highly efficient method to produce meaty process flavorings. PRACTICAL APPLICATION: The manuscript describes the production of process flavorings that exhibited meaty flavors by extrusion process. Physical properties, volatile profiles, and sensory evaluation of the products from methionine, thiamine, d-xylose, and glucose were evaluated. The extruded products from methionine and dextrose exhibited acceptable color, taste, and odor and presented many volatiles compounds contributing to meaty flavors. The results revealed the high potential to use a direct extrusion process with very low effluent, compared to the conventional method, to produce meaty flavors for industrial application.

Photoinduced release of odorous volatile organic compounds from aqueous pollutants: The role of reactive oxygen species in increasing risk during cross-media transformation

Photoinduced volatile organic compounds (VOCs) release from fatty alcohols at the air-water interface, has attracted considerable attention. This paper comprehensively explores the release of odorous VOCs from aqueous micropollutants under photoirradiation, especially in terms of the important role of the reactive oxygen species (ROS) in increased risk by cross-media transformation. The formation and distribution of photoinduced VOCs produced by aqueous benzyl alcohol (BzOH), a common ingredient in personal care products, were monitored in situ by online gas chromatography equipped with mass spectrometry and flame ionization detector (GC–MS/FID). The photoreaction of BzOH followed first-order kinetics with a rate constant of 0.0158/min under air. After 180 min of ultraviolet irradiation, the accumulated output of the gas-phase products benzene and benzaldehyde (BA) reached 3.8 μmol and 2.6 μmol respectively, being approximately 10 times that under nitrogen. According to electron paramagnetic resonance measurements, singlet oxygen mainly promoted the oxidation of BzOH to BA, which was an important intermediate producing benzene via photocleavage. Odorous alicyclic hydrocarbons were also generated through photorearrangement under nitrogen. On the other hand, the Henry's law constants of the main products were much lower than those of BzOH, indicating that the photoproducts would volatilize from the aqueous phase into the gas phase. The odor threshold of gas-phase products decreased to varying degrees after photoirradiation. Especially for BA, one of the main products, its odor threshold decreased 130 times compared with BzOH. This study shows that the risk of cross-media pollution could significantly increase due to the transformation of aqueous pollutants into odorous VOCs under photoirradiation and provides new insight into its risk prevention.

Emission, dispersion, and potential risk of volatile organic and odorous compounds in the exhaust gas from two sludge thermal drying processes

Emissions of odorous and volatile organic compounds (VOCs) were investigated between two sludge drying methods. A total of 37 chemical compounds were identified and quantified from the off-gases from sludge drying by indirect drying method. The total number of VOCs detected ranged from 3.45 × 10-3 to 4.53 mg/m3, which includes benzene series, volatile organic sulfur, and nitrogenous organic compounds. High emissions were found in the exhaust gas released from drying workshop that used direct drying method. Sulfur dioxide, aromatics, and chlorinated compounds were dominant. Based on the olfactory effect analysis and cancer risk assessment, the main odor-causing gaseous pollutants were methyl mercaptan and methyl sulfide (for indirect sludge drying process) and SO2 (for direct sludge drying process), while the dominant carcinogens were benzene, carbon tetrachloride, chloroform, and methylene. This study provides new insights into the emission characteristics, olfactory effects, and cancer risks of VOCs and odorous compounds in the exhaust gas from thermal sludge drying processes.

The challenges and perspectives for anaerobic digestion of animal waste and fertilizer application of the digestate

The increase in livestock production creates a serious problem of managing animal waste and by-products. Among the wide range of waste valorization methods available, anaerobic digestion is very promising. It is a form of material recycling that also produces renewable energy in the form of biogas, which is reminiscent of energy recycling. The effluent and digestate from the anaerobic digestion process need to be processed further. These materials are widely used in agriculture due to their composition. Both the liquid and solid fractions of digestate are high in nitrogen, making them a valuable source for plants. Before soil or foliar application, conditioning (e.g., with inorganic acids) and neutralization (e.g., with potassium hydroxide) is required to eliminate odorous compounds and microorganisms. Various methods of conducting the process by anaerobic digestion (use of additives increasing activity of microorganisms, co-digestion, multiple techniques of substrate preparation) and the possibility of controlling process parameters such as optimal C/N ratio (15–30), optimal temperature (psychrophilic (<20 °C), mesophilic (35–37 °C) and thermophilic (55 °C) for microorganism activity ensure high efficiency of the process. Literature data describing tests of various digestates on different plants prove high efficiency, determined by yield increase (even by 28%), nitrogen uptake (by 20%) or phosphorus recovery rate (by 43%) or increase of biometric parameters (e.g., leaf area).

Artificial neural network (ANN) modeling for the prediction of odor emission rates from landfill working surface.

Landfills release significant odorous compounds from the working surface, and their emission rates are crucial for odor and health risk assessment. A total of 99 valid datasets of odor emissions from a landfill working surface were obtained from in situ monitoring for 9months. Meteorological parameters (temperature, humidity, atmospheric pressure) and waste properties (contents of protein, lipid, carbohydrate, ash, and moisture) were used to construct artificial neural network (ANN) models for the emission rate prediction of typical compounds. The optimal structures and performance of the ANN models were determined by comparing and training with different structural configurations. The ANN models with genetic algorithm (GA) optimization show better performance than those without GA. With the data distribution of input parameters, the ranges of the emission rates of typical compounds were predicted by combining the established ANN models and the Monte Carlo approach. The sensitivity and uncertainty analyses revealed that temperature, atmospheric pressure, protein and lipid contents are parameters sensitive to emission rates, and meteorological parameters have significant impacts on the uncertainty. The established ANN models for the prediction of emission rates can provide scientific evidence and an approach to assess and control the odor and health risk in waste sectors.

Improving the Nutritional, Structural, and Sensory Properties of Gluten-Free Bread with Different Species of Microalgae.

Microalgae are an enormous source of nutrients that can be utilized to enrich common food of inherently low nutritional value, such as gluten-free (GF) bread. Addition of the algae species: Tetraselmis chuii (Tc), Chlorella vulgaris (Cv), and Nannochloropsis gaditana (Ng) biomass led to a significant increase in proteins, lipids, minerals (Ca, Mg, K, P, S, Fe, Cu, Zn, Mn), and antioxidant activity. Although, a compromise on dough rheology and consequential sensory properties was observed. To address this, ethanol treatment of the biomass was necessary to eliminate pigments and odor compounds, which resulted in the bread receiving a similar score as the control during sensory trials. Ethanol treatment also resulted in increased dough strength depicted by creep/recovery tests. Due to the stronger dough structure, more air bubbles were trapped in the dough resulting in softer breads (23–65%) of high volume (12–27%) vs. the native algae biomass bread. Breads baked with Ng and Cv resulted in higher protein-enrichment than the Tc, while Tc enrichment led to an elevated mineral content, especially the Ca, which was six times higher than the other algae species. Overall, Ng, in combination with ethanol treatment, yielded a highly nutritious bread of improved technological and sensory properties, indicating that this species might be a candidate for functional GF bread development.

Identification of Olfactory Nuisance of Floor Products Containing Bitumens with the TD-GC-MS/O Method.

The adopted TD–GC–MS/O method helps determine the correlation between the odour signals and compounds separated on the chromatographic column, from the analysed gas mixture. It is possible to compare the retention times at which the odour signals were identified with the retention time of eluting compounds, when the test system and matrix are known. The presented study describes the details of representative samples obtained from (1) indoor air samples from a room where floor materials containing bitumen are present, (2) wooden floor staves placed in an emission chamber, and (3) fragments (chips) of the materials mentioned above, placed in glass tubes, exposed to an elevated desorption temperature. The results, presented in the paper, describe the identified odours and their intensity and assign chemical compounds to each odour, indicating their likely source of origin. The results presented in the manuscript are intended to show what methodology can be adopted to obtain intense odours from the tested samples, without losing the sensitivity derived from GC–MS. The manuscript presents representative results—case studies. The results for various types of samples were not very reproducible, related to the complex matrix of bituminous products. The enormity of compounds present in tar adhesives makes it possible to indicate only the groups of compounds that emit from these systems. They include, primarily, aliphatic, aromatic and heteroaromatic hydrocarbons, particularly Naphthalene and Phenol derivatives.

Benthic cyanobacteria: A utility-centred field study

Although there is growing evidence that benthic cyanobacteria represent a significant source of toxins and taste and odour (T&O) compounds in water bodies globally, water utilities rarely monitor for them. Benthic cyanobacteria grow in an array of matrices such as sediments, biofilms, and floating mats, and they can detach and colonize treatment plants. The occurrence of compounds produced by benthic species across matrix and climate types has not been systematically investigated. Consequently, there is a lack of guidance available to utilities to monitor for and mitigate the risk associated with benthic cyanobacteria. To assess toxin and T&O risk across climatic zones and provide guidance to water utilities for the monitoring of benthic mats, two field surveys were conducted across three continents. The surveys examined the occurrence of six secondary metabolites and associated genes, namely, geosmin, 2-methylisoborneol (MIB), anatoxin-a, saxitoxin, microcystin, and cylindrospermopsin, in benthic environmental samples collected across three climates (i.e., temperate, sub-tropical, and tropical) and a range of matrix types. Existing enzyme-linked immunosorbent assays (ELISAs) and qPCR assays and were used to measure compound concentrations and their associated genes in samples. A novel qPCR assay was designed to differentiate the production of MIB by actinobacteria from that of cyanobacteria. MIB occurrence was higher in warmer climates than temperate climates. Cyanobacteria in benthic mats were the major producers of taste and odour compounds. Floating mats contained significantly higher concentrations of geosmin and saxitoxins compared to other matrix types. Samples collected in warmer areas contained significantly more saxitoxin and cylindrospermopsin than samples collected in temperate climates. While these trends were mainly indicative, they can be used to establish monitoring practices.These surveys demonstrate that benthic mats are significant contributors of secondary metabolites in source water and should be monitored accordingly. Benthic cyanobacteria were the sole producers of T&O in up to 17% of the collected samples compared to actinobacteria, which were sole producers in only 1% of the samples. The surveys also provided a platform of choice for the transfer of methodologies and specific knowledge to participating utilities to assist with the establishment of monitoring practices for benthic cyanobacteria and associated secondary metabolites.

VOCs and Odor Episodes near the German-Czech Border: Social Participation, Chemical Analyses and Health Risk Assessment.

People living on both sides of the German–Czech border are subject to episodes of odor air pollution. A joint German–Czech air sampling and risk assessment project was established to identify the substances responsible and their sources. Twenty-four volunteer study participants, 14 from the NW Czech Republic and 10 from Germany (Saxony) reported odors and collected canister samples during sampling periods in winter 2017 and 2018 and autumn 2018. Canister samples and passive samplers were analyzed for volatile organic compounds (VOCs) and passive samplers were analyzed for VOCs and carbonyls. OAVs (Odor Activity Values) and back trajectories were calculated with the aim of identifying the odor sources. Calculated OAVs were in excellent agreement with perceived smells close to an oil processing plant. Odorants identified in fifty canister samples during odor episodes and carbonyl measurements close to the edible oil processing plant were used for health evaluation. Odors reported by participants in Saxony frequently differed from those reported by participants in the Czech Republic. This suggests that certain sources of odor lying on either side of the border only affect that side and not the other with similar considerations regarding health effects. VOCs, including carbonyls, were also sampled at two relatively remote locations during winters of 2017 and 2018; two main sources of odorous compounds were identified at these sites. Analysis of samples taken at sampling sites shows that VOC air pollution and, to a lesser extent carbonyl pollution, originate from both industrial and local sources. Even though levels of sampled substances were not associated with acute effects at any site, long-term exposures to selected compounds could be cause for concern for carcinogenicity at some sites. Odors in Seiffen were associated with carcinogenic compounds in can samples. Although not necessarily representative of long-term exposures to the compounds studied, results such as these suggest that further study is needed to better quantify long-term exposure to potentially harmful compounds, and to either confirm or deny the existence of substantive health risk.

A comprehensive study for taste and odor compounds using electronic tongue and nose in broccoli stem with different thermal processing.

This study analyzed taste and odor profiles in broccoli stems with different methods of thermal processing using electronic tongue and electronic nose. In electronic tongue analysis, umami and bitterness were obviously changed upon thermal processing, however, saltiness, sweetness, and sourness showed slight variations. Between raw and thermally processed broccolis, microwaved broccoli showed the highest changes of tastes based on raw broccoli, however, blanched broccoli showed similar tastes to raw broccoli compared with the others. In electronic nose analysis, a total of 21 volatiles in broccolis were analyzed. Sulfur-containing volatiles were changed via thermal steps, and the generation and reduction of sulfur-containing compounds have occurred (i.e. methnaethiol, 2,4,5-trimethylthiazole). In addition, some of the thermal steps (oven-heating, microwave heating, air-frying) have occurred Maillard reaction, and thus pyridine was generated. Therefore, this study can provide flavor data in broccoli, and contribute to further research for flavor characteristics in broccoli using electronic sensors.

Synthesis of CoNi-layered double hydroxide on graphene oxide as adsorbent and construction of detection method for taste and odor compounds in smelling water

Taste and odor (T&O) compounds are important water pollutant, some of which are toxic. The relevant studies are all expand upon the well-known T&O compounds but for the unknown odors in smelling water. In this work, a method combining purge and trap with gas chromatograph-mass spectrometer (PT-GC/MS) and disperse solid-phase extraction with gas chromatograph (GC) was first proposed to detect T&O compounds in unknown odorous water accurately. Firstly, PT-GC/MS was used for a qualitative test on unknown odors in smelling water and determine the analytes. The hollow CoNi-layered double hydroxide (LDH) on graphene oxide (GO) was then used as a composite adsorbent to pretreat the water, in which the GO provided large specific surface, and the LDH worked as a confinement cavity to enhance capture and retention capacity for volatile organic compounds (VOCs). According to the properties of T&O compounds determined by PT-GC/MS in water, a corresponding GC method was established for accurately quantitative analysis. In this paper, five T&O compounds were detected simultaneously, including dimethyl sulfide, meistylene, N, N-dimethylbenzylamine, 2, 4-dimethylbenzaldehyde and 2, 4-di-tert-butylphenol. Extraction parameters were optimized, including ratio of desorption solvent, amount of adsorbent, pH value, etc. Under the optimal conditions, the detection limits for analysis were 1.14 μg/L to 3.07 mg/L. The satisfactory recoveries were 94–98%. Furthermore, two optimal determination outcomes of odor waters from different places support the practicability of the method, which is expected to be widely used in the detection of unknown odors in smelling water.

Sers Substrate Based on Ag Nanoparticles @ Layered Double Hydroxide@Graphene Oxide and Au@Ag Core-Shell Nanoparticles for Detection of Two Taste and Odor Compounds

Sers Substrate Based on Ag Nanoparticles @ Layered Double Hydroxide@Graphene Oxide and Au@Ag Core-Shell Nanoparticles for Detection of Two Taste and Odor Compounds

Statistical evaluation to validate matrix-matched calibration for standardized beany odor compound quantitation in yellow pea flour using HS-SPME-GC-MS.

Accurate and precise quantitation of beany odor compounds is important in developing yellow pea (Pisum sativum L., YP) flour-based foods. Aiming at establishing standardized external calibration using an internal standard (ECIS) quantitation method, the effect of solvent extraction on matrix deodorization and systematic statistical analysis on quantitation was evaluated. Initially, accelerated dichloromethane extraction on YP flour and starch produced two clearest deodorized matrix-matched matrices. Secondly, due to the heteroskedasticity, weighted least squares regression (WLSR) was introduced to build calibration curves. The curve linearity and regression parameters were further confirmed via a t-test. Lastly, methodology indicators including LOD/LOQ, accuracy and precision, and the matrix effect (ME) were assessed. Results showed that there were no significant differences in the quantity of beany odor compounds interpolated from two deodorized matrices. This study demonstrated for the first time that despite the unignorable ME, deodorized starch is a feasible and affordable alternative to deodorized YP flour in the quantitation of beany odor compounds to achieve a reliable result.

Behavior of musty odor compounds caused by cyanobacteria in drinking-water-supply watershed

Behavior of musty odor compounds caused by cyanobacteria in drinking-water-supply watershed

Rapid Determination of 14 Odorous Compounds in Drinking Water Using Gas Chromatography-Mass Spectrometry Coupled with Headspace Solid Phase Microextraction Pretreatment

Rapid Determination of 14 Odorous Compounds in Drinking Water Using Gas Chromatography-Mass Spectrometry Coupled with Headspace Solid Phase Microextraction Pretreatment

Enhanced Removal of Typical Odor Compounds in Constructed Wetlands Integrated with Iron Carbon and Tidal Flow

Enhanced Removal of Typical Odor Compounds in Constructed Wetlands Integrated with Iron Carbon and Tidal Flow