Low Odor Threshold Research Articles

Structure-Odor Activity Studies on Monoterpenoid Mercaptans Synthesized by Changing the Structural Motifs of the Key Food Odorant 1-p-Menthene-8-thiol.

1-p-Menthene-8-thiol (1) has been discovered as the key odorant in grapefruit juice several decades ago and contributes to the overall odor of the fruit with an extremely low odor threshold of 0.000034 ng/L in air. This value is among the lowest odor thresholds ever reported for a food odorant. To check whether modifications in the structure of 1 would lead to changes in odor threshold and odor quality, 34 mercapto-containing p-menthane and 1-p-menthene derivatives as well as several aromatic and open-chain mercapto monoterpenoids were synthesized. Eighteen of them are reported for the first time in the literature, and their odor thresholds and odor qualities as well as analytical data are supplied. A comparison of the sensory data with those of 1 showed that hydrogenation of the double bond led to a clear increase in the odor threshold. Furthermore, moving the mercapto group into the ring always resulted in higher odor thresholds compared to thiols with a mercapto group in the side chains. Although all tertiary thiols always exhibited low odor thresholds, none of the 31 compounds reached the extremely low threshold of 1. Also, none of the synthesized mercapto monoterpenoids showed a similar odor quality resembling grapefruit. Although the saturated and aromatic analogues exhibited similar scents as 1, the aromas of the majority of the other compounds were described as sulfury, rubber-like, burned, soapy, or even mushroom-like. NMR and MS data as well as retention indices of the 23 newly reported sulfur-containing compounds might aid in future research to identify terpene-derived mercaptans possibly present in trace levels in foods.

Subtleties of human exposure and response to chemical mixtures from spills

Worldwide, chemical spills degrade drinking water quality and threaten human health through ingestion and inhalation. Spills are often mixtures of chemicals; thus, understanding the interaction of chemical and biological properties of the major and minor components is critical to assessing human exposure. The crude (4-methylcyclohexyl)methanol (MCHM) spill provides an opportunity to assess such subtleties. This research determined the relative amounts, volatilization, and biological odor properties of minor components cis- and trans-methyl-4-methylcyclohexanecarboxylate (MMCHC) isomers and major components cis- and trans-4-MCHM, then compared properties and human exposure differences among them. 1H nuclear magnetic resonance and chromatography revealed that the minor MMCHC isomers were about 1% of the major MCHM isomers. At typical showering temperature of 40 °C, Henry's law constants were 1.50 × 10−2 and 2.23 × 10−2 for cis- and trans-MMCHC, respectively, which is 20–50 fold higher than for 4-MCHM isomers. The odor thresholds were 1.83 and 0.02 ppb-v air for cis- and trans-MMCHC, which were both described as predominantly sweet. These data are compared to the higher 120 ppb-v air and 0.06 ppb-v odor thresholds for cis- and trans-4-MCHM, for which the trans-isomer had a dominant licorice descriptor. Application of a shower model demonstrated that while MMCHC isomers are only about 1% of the MCHM isomers, during showering, the MMCHC isomers are 13.8% by volume (16.3% by mass) because of their higher volatility. Trans-4-MCHM contributed about 82% of the odor because of higher volatility and lower odor threshold, trans-MMCHC, which represents 0.3% of the mass, contributed 18% of the odor. This study, with its unique human sensory component to assess exposure, reaffirmed that hazard assessment must not be based solely on relative concentration, but also consider the chemical fate, transport, and biological properties to determine the actual levels of exposure across different media.

Fragrant Sesquiterpene Ketones as Trace Constituents in Frankincense Volatile Oil of Boswellia sacra

In a previous study, two highly potent yet unidentified odorants were detected that were present at trace levels in the volatile fraction of Boswellia sacra gum resin. These two compounds were isolated semipreparatively from the volatile oil by a sensory-guided fractionation process involving microscale bulb-to-bulb distillation, countercurrent chromatography, and preparative gas chromatography. In this manner, the two oxygenated sesquiterpenes could be identified as rotundone (1) and mustakone (2). Compound 2 is described for the first time as a potent odorant with a very low odor threshold.

Straightforward strategy for quantifying rotundone in wine at ng L−1 level using solid-phase extraction and gas chromatography-quadrupole mass spectrometry. Occurrence in different varieties of spicy wines

This paper presents a straightforward methodology to quantify rotundone in wine at ngL−1 level. This compound, responsible for the black pepper aromatic note, may have sensorial relevance in some wines due to its low odor threshold, estimated at only 16ngL−1 in red wines. The proposed strategy is based on solid phase extraction and analysis by GC–MS.The detection limit value was 0.6ngL−1, which is more than one order of magnitude below its odor threshold in wine. Matrix effects have not been found and a synthetic wine calibration was proposed. The precision of the method was evaluated in reproducibility terms, obtaining a very acceptable value (RSD 4%).The optimized and validated strategy was applied to quantify this molecule in thirty wines belonging to different varieties as Graciano, Maturana tinta, Schioppettino, Shiraz, Duras and Gamay. Two of these wines exhibited levels higher than 100ngL−1.

Volatile thiols in coffee: A review on their formation, degradation, assessment and influence on coffee sensory quality

Thiols are among the compounds that have the greatest impact on the flavor of coffee. Due to their extremely low odor thresholds, they have a significant sensory impact even at very low concentrations. Thiols are formed during coffee roasting and are described as the key odorants responsible for the typical “coffee” and “roasty” odor notes, greatly influencing the sensory characteristics of coffee. They are particularly reactive and prone to oxidation; their rapid depletion after preparation of a coffee brew and during storage of roasted coffee has been associated with sensory quality decrease and coffee going stale. For these reasons, their determination and insight into their formation and degradation mechanisms could help us to preserve the sensory quality of coffee and to modulate its sensory features. Coffee aroma has been widely studied in recent decades, and it has become evident that the role of certain volatile thiols is paramount. Nevertheless, a limited number of studies have specifically addressed this class of compounds, and several aspects have not yet been satisfactorily elucidated. The aim of this review is to provide an overview of the current state on knowledge about coffee thiols, focusing on their occurrence, determination, sensory impact, formation and evolution in roasted and brewed coffee.

Characterizing the biotransformation of sulfur-containing wastes in simulated landfill reactors

Landfills that accept municipal solid waste (MSW) in the U.S. may also accept a number of sulfur-containing wastes including residues from coal or MSW combustion, and construction and demolition (C&D) waste. Under anaerobic conditions that dominate landfills, microbially mediated processes can convert sulfate to hydrogen sulfide (H2S). The presence of H2S in landfill gas is problematic for several reasons including its low odor threshold, human toxicity, and corrosive nature. The objective of this study was to develop and demonstrate a laboratory-scale reactor method to measure the H2S production potential of a range of sulfur-containing wastes. The H2S production potential was measured in 8-L reactors that were filled with a mixture of the target waste, newsprint as a source of organic carbon required for microbial sulfate reduction, and leachate from decomposed residential MSW as an inoculum. Reactors were operated with and without N2 sparging through the reactors, which was designed to reduce H2S accumulation and toxicity. Both H2S and CH4 yields were consistently higher in reactors that were sparged with N2 although the magnitude of the effect varied. The laboratory-measured first order decay rate constants for H2S and CH4 production were used to estimate constants that were applicable in landfills. The estimated constants ranged from 0.11yr−1 for C&D fines to 0.38yr−1 for a mixed fly ash and bottom ash from MSW combustion.

Determination of dimethyl selenide and dimethyl sulphide compounds causing off-flavours in bottled mineral waters

Sales of bottled drinking water have shown a large growth during the last two decades due to the general belief that this kind of water is healthier, its flavour is better and its consumption risk is lower than that of tap water. Due to the previous points, consumers are more demanding with bottled mineral water, especially when dealing with its organoleptic properties, like taste and odour. This work studies the compounds that can generate obnoxious smells, and that consumers have described like swampy, rotten eggs, sulphurous, cooked vegetable or cabbage. Closed loop stripping analysis (CLSA) has been used as a pre-concentration method for the analysis of off-flavour compounds in water followed by identification and quantification by means of GC-MS. Several bottled water with the aforementioned smells showed the presence of volatile dimethyl selenides and dimethyl sulphides, whose concentrations ranged, respectively, from 4 to 20 ng/L and from 1 to 63 ng/L. The low odour threshold concentrations (OTCs) of both organic selenide and sulphide derivatives prove that several objectionable odours in bottled waters arise from them. Microbial loads inherent to water sources, along with some critical conditions in water processing, could contribute to the formation of these compounds. There are few studies about volatile organic compounds in bottled drinking water and, at the best of our knowledge, this is the first study reporting the presence of dimethyl selenides and dimethyl sulphides causing odour problems in bottled waters.

Optimization of Removal of 2-methylisoborneol from Drinking Water using UV/H2O2

Abstract2-methylisoborneol (2-MIB) is a common odor-causing compound in drinking water with a low odor threshold (10 ng/L). Since conventional treatment processes cannot effectively remove it, this study investigated an advanced oxidation technology: UV/H

Treatment technologies and mechanisms for three odorants at trace level: IPMP, IBMP, and TCA

Odour episodes caused by algal metabolites are gaining more and more attention in recent years. Besides geosmin and 2-methylisoborneol (MIB), 2-isopropyl-3-methoxypyrazine (IPMP), 2-isobutyl-3-methoxypyrazine (IBMP), and 2,4,6-trichloroanisole (TCA) have emerged to be important off-flavour sources. Their low odour threshold concentrations (several ng ·L−1), which are even lower than those of MIB and geosmin, pose challenges for treatment strategies. Hence, a practical and efficient mitigation technology is needed. The possible practical technologies, including powdered activated carbon (PAC) adsorption and oxidation by chlorine and potassium permanganate, were investigated. The results indicated that chlorine and potassium permanganate oxidation of the three odorants were unfeasible while PAC adsorption was effective. As for adsorption, TCA, followed by IBMP and IPMP, was most easily removed by PAC. The Freundlich model could well describe the adsorption isotherm data. The adsorption capacities for IPMP, IBMP, and TCA were described as follows: , , and . For five earthy/musty odorants including geosmin and MIB, octanol/water partition coefficient, molecular weight, and polarizability all promoted adsorption while aqueous solubility showed a negative influence. The hydrophobic interaction was believed to be the dominant force in the adsorption mechanism while the π-electron interaction enhanced adsorption when a benzene ring was present. This result could be used to predict the adsorption performance of emerging odorants.

Determination of 2-aminoacetophenone in white wines using ultrasound assisted SPME coupled with GC-MS

The unpleasant odor of an off-flavor is mostly caused by only one or, sometimes, several volatile compounds with very low odor threshold values giving the typical unpleasant odor taint of the spoiled food product. 2-Aminoacetophenone is an aroma compound which causes the untypical aging off-flavor in Vitis vinifera white wines. Ultrasound assisted headspace solid phase microextraction (UA-HS-SPME) and direct immersion solid phase microextraction (DI-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) were tested and optimized for determination of 2-aminoacetophenone in Riesling wines fermented by different yeast strains.

Characterization of Aromatics at Working Surface of a Municipal Solid Waste Landfill

With the rapid urbanization and economic growth in China especially near 2 decades, the vast amount of municipal solid waste (MSW) were produced annually. Landfills are the predominant disposal sites for MSW in China, receiving more than 75% of the collected MSW every year. While the volume concentration is usually less than 1%, NMOCs are generally considered as the main source of the odorous problem at MSW landfills, because they include many compounds with very low odor thresholds. What’s more, aromatics is vital part of NMOCs for its toxic effect, which contains Benzene. The main objective of this study was to understand the comprehensive behavior of aromatics of landfill gas. In this work we present an integrated evaluation of working surface concentration distribution and emission rate of a municipal solid waste landfill. And in order to understand the transportation of aromatic, a new parameter was introduced to analyze this process. Thus, result shows, the fugitive emission of aromatics in the operating surface may need pay more attention. The highest average concentration for aromatics was found in autumn. Aromatic’s emission rate in winter was larger than autumn, the highest emission rate of aromatics toluene, 0.011g/m2/h. The B:T ratio in winter was significant higher that of other seasons.

Effects of Pasteurization on Volatile Compounds and Sensory Properties of Coconut (Cocos nucifera L.) Water: Thermal vs. High-Pressure Carbon Dioxide Pasteurization

Coconut water is a tropical beverage with a distinctive odor and flavor that has until now not been adequately characterized. In the present paper, the volatile compound composition of coconut water was investigated using head space solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Analyses were made of fresh untreated (FU) samples and samples pasteurized using two different technologies: conventional thermal treatment (thermal pasteurization (TP)) and high-pressure carbon dioxide (HPCD) pasteurization, which has recently attracted great interest as an innovative nonthermal preservation treatment. Seventy-three volatile compounds were identified; 27 of them reported for the first time in coconut water. The results showed that HPCD treatment depletes short- and medium-chain alcohols, while TP treatment triggers an increase in aldehydes, ketones, and 2-acetyl-1-pyrroline, an aroma compound active at low odor thresholds and characterized by “popcorn” and “toasted” odor descriptors. Sensory discrimination analysis (triangle test) showed there to be no significant differences between HPCD and FU samples, while TP and FU samples were perceived significantly differently. Descriptive sensory analyses evidenced more intense “cooked,” “toasted bread,” and “hazelnut” characteristics in TP-treated coconut water, consistent with HS-SPME-GC-MS data. In conclusion, instrumentally measurable changes in volatile compounds were more moderate with HPCD than with TP treatment and were not sensorially perceivable compared with the FU product.

Constituent Compounds of Floral Scent in Rhyncholaeliocattleya Ports of Paradise “Gleneyrie's Green Giant”: a Cultivar of Genus Cattleya

A large body of research dealing with floral odors in many seed plants, including 90 families and 38 orders [1], has been conducted. Among them, Orchidaceae is by far the most investigated family. However, research into orchid fragrance has focused mainly on other genera instead of Cattleya [2, 3]. Although Cattleya is an intensively employed genus in the orchid family [4], the scent from this genus is rarely studied and thus poorly understood. In this study, we selected Rhyncholaeliocattleya Ports of Paradise “Gleneyrie s Green Giant” as the subject, one cultivar of Cattleya, collected the floral scent from naturally growing flowers through dynamic headspace adsorption, and identified the floral scent compounds by means of thermal-desorption cold trap/gas chromatography/mass spectrometry. In the experiment, volatiles were collected using an improved dynamic headspace aircirculation method, and the volatiles were trapped in 6 mm Dynatherm Centerless Ground SS sample tubes. After that, the tubes were desorbed using a PerkinElmer Turbo Matrix 650 automatic thermal desorber (ATD). Finally, analyses were carried out using a PerkinElmer Clarus 600 gas chromatograph (GC) coupled to a PerkinElmer Clarus 600 T mass spectrometer. As shown in Table 1, the number of the scent volatile compounds from the flower of Rhyncholaeliocattleya Ports of Paradise “Gleneyrie s Green Giant” was 23, 32, 45, 28, and 32 at the corresponding time points 8:00 AM, 10:00 AM, 12:00 AM, 2:00 PM, and 4:00 PM, respectively. Thus, the Cattleya cultivar emitted the most volatile compounds at noon. A list of 71 chemical compounds identified from headspace samples of floral scent is presented in Table 1. The floral scent constituents are divided into six major compound classes based on inspection of their structures and knowledge of the major pathways of plant secondary metabolism. These classes were alcohols, alkenes, aldehydes, ketones, esters, and alkanes. Being important components, the percentages of 3,7-dimethyl-1,6-octadien-3-ol, 6-octen-1-ol,3,7-dimethyl, and phenylethyl alcohol dramatically changed within a day. 3,7-Dimethyl-1,6-octadien-3-ol increased to its maximum, which was as much as 30.8% in terms of percentage of relative contents at 2:30 PM, and sharply declined to less than 1% by 4:30 PM. Similarly, phenylethyl alcohol reached a summit at 10:30 AM, then fell to 1%. As for 6-octen-1-ol,3,7-dimethyl, it increased slowly after noon. In summary, there were fluctuations in the amounts of different volatile components from Rhyncholaeliocattleya Ports of Paradise “Gleneyrie s Green Giant” in the daytime. Among them, the amounts of linalool, phenylethyl alcohol, nonanal, 1,3,6-octatriene,3,7-dimethyl, and acetophenone changed markedly. Moreover, the amounts of linalool and 1,3,6-octatriene,3,7-dimethyl changed most. 1,3,6-Octatriene,3,7-dimethyl, linalool, -pinene, and phenylethyl alcohol are the most significant odor-active volatiles, with low odor thresholds in air [5]. Because the volatile compound s odor activity value (OAV) is the ratio of the aroma concentration to its odor threshold in air [6], 3,7-dimethyl-1,3,6-octatriene could be regarded as an important compound representing the aroma characteristics of Rhyncholaeliocattleya Ports of Paradise ”Gleneyrie s Green Giant” given that its relative content is as high as 11.120% at the full blooming stage. Likewise, linalool is a naturally occurring terpene alcohol found in many flowers and spice plants with many commercial applications, the majority of which are based on its pleasant scent. Numerous aroma extract dilution analysis show that linalool has a high OAV and a high FD (flavor dilution) factor, which is the ratio of the concentration of the odorant in the initial volatile oil to its threshold [7].

Application of PTR-MS for measuring odorant emissions from soil application of manure slurry.

Odorous volatile organic compounds (VOC) and hydrogen sulfide (H2S) are emitted together with ammonia (NH3) from manure slurry applied as a fertilizer, but little is known about the composition and temporal variation of the emissions. In this work, a laboratory method based on dynamic flux chambers packed with soil has been used to measure emissions from untreated pig slurry and slurry treated by solid-liquid separation and ozonation. Proton-transfer-reaction mass spectrometry (PTR-MS) was used to provide time resolved data for a range of VOC, NH3 and H2S. VOC included organic sulfur compounds, carboxylic acids, phenols, indoles, alcohols, ketones and aldehydes. H2S emission was remarkably observed to take place only in the initial minutes after slurry application, which is explained by its high partitioning into the air phase. Long-term odor effects are therefore assessed to be mainly due to other volatile compounds with low odor threshold values, such as 4-methylphenol. PTR-MS signal assignment was verified by comparison to a photo-acoustic analyzer (NH3) and to thermal desorption GC/MS (VOC). Due to initial rapid changes in odorant emissions and low concentrations of odorants, PTR-MS is assessed to be a very useful method for assessing odor following field application of slurry. The effects of treatments on odorant emissions are discussed.

Measurement of chemical leaching potential of sulfate from landfill disposed sulfate containing wastes

A number of sulfate-containing wastes are disposed in municipal solid wastes (MSW) landfills including residues from coal, wood, and MSW combustion, and construction and demolition (C&D) waste. Under anaerobic conditions that dominate landfills, the sulfate can be reduced to hydrogen sulfide which is problematic for several reasons including its low odor threshold, toxicity, and corrosive nature. The overall objective of this study was to evaluate existing protocols for the quantification of total leachable sulfate from solid samples and to compare their effectiveness and efficiency with a new protocol described in this study. Methods compared include two existing acid extraction protocols commonly used in the U.S., a pH neutral protocol that requires multiple changes of the leaching solution, and a new acid extraction method. The new acid extraction method was shown to be simple and effective to measure the leaching potential of sulfate from a range of landfill disposed sulfate-containing wastes. However, the acid extraction methods do not distinguish between sulfate and other forms of sulfur and are thus most useful when sulfate is the only form of sulfur present.

Emission Characteristics of Odors and Odorants Released from Grilling Mackerel and Pork Belly by Different Cooking Tools

It is known that mackerel and pork belly release a strong odor in the process of roasting. We evaluated a dilution factor of odor arising during roasting mackerel or pork belly and the relative odor strength using several cooking tools and analyzed compounds causing odors with gas chromatograph / mass detector.Roasting pans used were grill with lid, electric grill without lid and general roasting pan, and a grill with lid can attach the activated carbon charcoal deodorant at the inside of lid. And all electric grills have a drip tray under the heater. We investigated characteristics of odor emission depending on the presence of water and deodorants in these cooking tools. Study has shown that roasting mackerel produces approximately 36 time more odors than roasting pork belly, and the reduced odor emission when roast with water. And it shows the reduced deodorant effect when cooked with water after attaching activated carbon charcoal in the cooking pan. Major odor causing compounds arising when cooking mackerel and pork belly were aldehydes with high boiling point such as octyl aldehyde with a low odor threshold value.

A comparative study of mass transfer coefficients of reduced volatile sulfur compounds for biotrickling filter packing materials

Abstract Biofiltration is a cost-effective technology for reduction of odor emissions from intensive pig production, but removal of volatile sulfur compounds may be limited by low mass transfer. Among these volatile sulfur compounds, hydrogen sulfide and methanethiol are essential odorants emitted from animal houses according to the low odor threshold values. In order to get a better understanding of the limitations for optimization and further development of biofiltration for odor control, a study of overall mass transfer coefficients of volatile sulfur compounds for packing materials potentially used for biotrickling filters is presented. Mass transfer coefficients were obtained by taking advantage of online PTR-MS experiments of breakthrough curves, combined with a developed mass transfer model. The experiments were performed at different air and liquid velocities for selected packing materials. The results demonstrate that the overall mass transfer coefficients of volatile sulfur compounds depend on the velocity of both air and liquid. When the mass transfer coefficients are normalized to (divided by) the corresponding pressure drop, the results indicate that the filter packed with ceramic saddles or cellulose pads have higher normalized mass transfer coefficients, compared to the other materials investigated in this study. Correlating the mass transfer coefficients to characteristics of different packing materials did not succeed and as an alternative empirical relationship between mass transfer coefficients and the gas and liquid velocities were established.

Sila‐α‐galbanone and Analogues: Synthesis and Olfactory Characterization of Silicon‐Containing Derivatives of the Galbanum Odorant α‐Galbanone

AbstractSilicon compounds 1b–3b are sila‐analogues of the galbanum odorants α‐galbanone (1a), α‐spirogalbanone (2a), and nor‐α‐galbanone (3a), respectively. Sila‐α‐galbanone (1b), sila‐α‐spirogalbanone (2b), and sila‐nor‐α‐galbanone (3b) were synthesized in multistep syntheses in isomerically pure form, starting from Me2SiCl2, (CH2=CH)2SiCl2, and Me2(CH2=CH)SiCl, respectively. Hydroformylation of vinylsilanes, followed by either ring‐closing aldol condensation or ring‐closing alkene metathesis, were the key steps in these syntheses. The C/Si pairs 1a/1b, 2a/2b, and 3a/3b were studied for their olfactory properties. All compounds possess green‐fruity galbanum‐type odors with pineapple aspects and thus are olfactorily related. However, sila‐analogues 1b–3b were found to be weaker than the corresponding parent carbon compounds 1a–3a. This effect is most pronounced for the C/Si pair 2a/2b as indicated by the odor thresholds of 0.023 ng L–1 air (2a) and 3.8 ng L–1 air (2b). However, due to their higher molecular mass, the silicon compounds are less volatile and thus more substantive in functional applications. In contrast to the stable 5‐silacyclohex‐1‐enes 1b and 2b, the 4‐silacyclopent‐1‐ene 3b shows a limited chemical stability. For compound 3a an extremely low odor threshold of 0.0087 ng L–1 air was measured, and the silicon analogue 3b with an odor threshold of 0.085 ng L–1 air is the sila‐odorant with the lowest odor threshold measured so far.

Characterizing reduced sulfur compounds emissions from a swine concentrated animal feeding operation

Reduced sulfur compounds (RSCs) emissions from concentrated animal feeding operations (CAFOs) have become a potential environmental and human health concern, as a result of changes in livestock production methods. RSC emissions were determined from a swine CAFO in North Carolina. RSC measurements were made over a period of ≈1 week from both the barn and lagoon during each of the four seasonal periods from June 2007 to April 2008. During sampling, meteorological and other environmental parameters were measured continuously. Seasonal hydrogen sulfide (H2S) barn concentrations ranged from 72 to 631 ppb. Seasonal dimethyl sulfide (DMS; CH3SCH3) and dimethyl disulfide (DMDS; CH3S2CH3) concentrations were 2–3 orders of magnitude lower, ranging from 0.18 to 0.89 ppb and 0.47 to 1.02 ppb, respectively. The overall average barn emission rate was 3.3 g day−1 AU−1 (AU (animal unit) = 500 kg of live animal weight) for H2S, which was approximately two orders of magnitude higher than the DMS and DMDS overall average emissions rates, determined as 0.017 g day−1 AU−1 and 0.036 g day−1 AU−1, respectively. The overall average lagoon flux was 1.33 μg m−2 min−1 for H2S, which was approximately an order of magnitude higher than the overall average DMS (0.12 μg m−2 min−1) and DMDS (0.09 μg m−2 min−1) lagoon fluxes. The overall average lagoon emission for H2S (0.038 g day−1 AU−1) was also approximately an order of magnitude higher than the overall average DMS (0.0034 g day−1 AU−1) and DMDS (0.0028 g day−1 AU−1) emissions. H2S, DMS and DMDS have offensive odors and low odor thresholds. Over all four sampling seasons, 77% of 15 min averaged H2S barn concentrations were an order of magnitude above the average odor threshold. During these sampling periods, however, DMS and DMDS concentrations did not exceed their odor thresholds. The overall average barn and lagoon emissions from this study were used to help estimate barn, lagoon and total (barn + lagoon) RSC emissions from swine CAFOs in North Carolina. Total (barn + lagoon) H2S emissions from swine CAFOs in North Carolina were estimated to be 1.22*106 kg yr−1. The barns had significantly higher H2S emissions than the lagoons, contributing ≈98% of total North Carolina H2S swine CAFO emissions. Total (barn + lagoon) emissions for DMS and DMDS were 1–2 orders of magnitude lower, with barns contributing ≈86% and ≈93% of total emissions, respectively. H2S swine CAFO emissions were estimated to contribute ≈18% of North Carolina H2S emissions.

Fast and solvent-free quantitation of boar taint odorants in pig fat by stable isotope dilution analysis–dynamic headspace-thermal desorption–gas chromatography/time-of-flight mass spectrometry

Boar taint is a specific off-odour of boar meat products, known to be caused by at least three unpleasant odorants, with very low odour thresholds. Androstenone is a boar pheromone produced in the testes, whereas skatole and indole originate from the microbial breakdown of tryptophan in the intestinal tract. A new procedure, applying stable isotope dilution analysis (SIDA) and dynamic headspace-thermal desorption–gas chromatography/time-of-flight mass spectrometry (dynHS-TD–GC/TOFMS) for the simultaneous quantitation of these boar taint compounds in pig fat was elaborated and validated in this paper. The new method is characterised by a simple and solvent-free dynamic headspace sampling. The deuterated compounds d3-androstenone, d3-skatole and d6-indole were used as internal standards to eliminate matrix effects. The method validation performed revealed low limits of detection (LOD) and quantitation (LOQ) with high accuracy and precision, thus confirming the feasibility of the new dynHS-TD–GC/TOFMS approach for routine analysis.