Quantification Of Odorants Research Articles

Development of a rapid and accurate method for the determination of key compounds of pig odor

Sampling of odor substances in the emissions from swine production facilities is still the limiting step for routine odor quantification. Solid sorption techniques based on cartridges were developed for three categories of substances (indoles, volatile fatty acids and methylthiol) and were standardized to a sampling time of 15 min. These cartridges also trap dust particles which transport odor substances. Quantification was performed by RP-HPLC or GC. Reliability criteria revealed excellent values for sensitivity (lower ppb level) and repeatability (R.S.D.<10%), thus they are comparable to fiber solid-phase micro extraction sorption techniques. Parallel determinations in feces and air revealed high correlations ( r=0.99, P<0.01), so that microbial processes during digestion determine odor quality and hence provide a possibility to reduce odor via feeding.

EVALUATION OF THERMAL DESORPTION FOR THE MEASUREMENT OF ARTIFICIAL SWINE ODORANTS IN THE VAPOR PHASE

Quantification of odorants from animal production facilities is difficult. The current technique is to collect air samples in Tedlar bags and quantify odor using a trained olfactory panel. In this approach, relative differences between samples can be determined, but further quantification of odorants is limited. An alternative approach is to quantify odorants in air emissions using sorbent tubes. A sorbent tube is a glass tube packed with a specific adsorbent material (Tenax TA, Carboxen 1000, Carbosieve SIII, etc.) and has been used to collect volatiles and quantify emissions from various industrial sources. Each adsorbent has a limited range of chemical selectivity. Limited applications of sorbent tubes with single or dual adsorbents have been used to measure odorant emissions from animal production facilities. In this study, tri–packed sorbent tubes and Tedlar bags were compared in characterizing 19 major odorants found in artificial swine odor. The sorbent tubes were packed with Tenax TA, Carboxen 1000, and Carbosieve SIII. The artificial swine odor was directly desorbed onto the tri–packed sorbent tube. For comparison, a 10–L Tedlar bag was filled with nitrogen gas and artificial swine odor. The Tedlar bag was then desorbed onto the tri–packed sorbent tube. The sorbent tube was then thermally desorbed into a gas chromatography (GC) system with a flame ionization detector (FID) for quantification. The tri–packed sorbent tube demonstrated recoveries greater than 74% and detection limits less than 0.4 ng for all 19 odorants. Thus, a tri–packed sorbent tube may provide an analytical method to measure low concentrations of major odorants found in air emissions from swine production facilities. Tedlar bags showed limited recoveries of some odorants, less than 12% for indole and skatole. In addition, Tedlar bags immediately sampled after three flushings with nitrogen emitted 3.50 ng L–1 hr–1 of acetic acid (~35% above background levels) and 2.13 ng L–1 hr–1 phenol (~27% above background levels). These results suggest that air samples collected in Tedlar bags may bias olfactory analysis.

Quantification of odors and odorants from swine operations in North Carolina

A total of 331 different VOCs and fixed gases from swine facilities in North Carolina were identified by gas chromatography and mass spectrometry (GC/MS). Of these, 203 were found in air samples adsorbed onto Tenax ®, 112 were found in air samples adsorbed onto cotton material, and 167 different compounds were identified in the lagoon samples. The compounds identified were diverse, and included many acids, alcohols, aldehydes, amides, amines, aromatics, esters, ethers, fixed gases, halogenated hydrocarbons, hydrocarbons, ketones, nitriles, other nitrogen-containing compounds, phenols, sulfur-containing compounds, steroids, and other compounds. The vast majority of these compounds were present at concentrations below published odor and irritation thresholds. Yet human assessments indicated that odors (and irritant sensations) in the immediate vicinity of the swine houses (and even at distances beyond 1000 ft) were strong. Comparison of the findings from chemical and human assessments points to the importance of the cumulative effects of hundreds of compounds in producing odor and irritation downwind of swine operations. Many GC peaks from the samples were too small to allow identification of the compounds, but their presence may also contribute significantly to the odor and irritation. Several methodological difficulties were associated with the human odor assessments. Odorous air evaluated in the field was simultaneously collected in Tedlar ® bags for evaluation in the laboratory; however, intensity ratings in the field were higher than those in the laboratory. This is due to the fact that organic dust (dried fecal material and feed) adheres to Tedlar ® bags and the tubing of collection/delivery systems; therefore, only VOCs from the vapor phase (but not the dust) reach the nose of the panelists in sniffing air samples obtained in Tedlar ® bags. Future collection and measurement techniques need to be developed that can evaluate odors from dust and vapor phases simultaneously in the laboratory. Dispersion models also need to be developed that account accurately for odor intensities downwind of animal operations. Finally, safety standards for odor exposures need to be determined that consider the risk of simultaneous exposure to hundreds of low level compounds.

Biosensor for Detecting Odorous Compounds

The odor quantification of any environmental sample by use of either panel decisions or analytical instruments is difficult. This study employed a sensor system to detect different odorants. The system consisted of an individual sensor or an array of multisensors in which different synthesized protein analogs were coated onto the surface of piezoelectric electrodes. By monitoring the change in the resonant frequency, the concentration of the specific gas was quantified. The targeted odor pollutants included volatile compounds of ammonia, mercaptoethanol, methyl amine, acetic acid, and chlorobenzene as well as gaseous compounds of ammonia and methyl amine. The results indicate that there is a linear relationship between sensor responses and compound concentrations. These sensors can detect compound concentrations in the low ppmv ranges. The response time is rapid. However, the system is not completely reversible—i.e., sensor response did not revert to its original value because of incomplete desorption with odorless air. Nevertheless, the response of the module forms a unique fingerprint for each individual compound and for mixed compounds. But reliability, stability, durability, and implementation of the system await further investigation.

A piezoelectric biosensor as an olfactory receptor for odour detection: electronic nose

Humans can detect and differentiate the presence of different odours even at trace levels of these odorous compounds. The odour quantification of any particular samples is normally based on conventional panel decisions. Other analytical instruments could be used to detect trace levels of odorous molecules. This study presents the results of a biological sensor system subject to different odorants. The system consists of a sensor in which the isolated olfactory receptor proteins (ORPs) from bullfrogs ( Rana spp. ) were coated onto the surface of a piezoelectric (PZ) electrode, similar to the mechanism of human olfaction. The PZ crystal served as a signal transducer. The results indicate rapid (about 400 s), reversible, and longterm (up to 3 months) stable responses to different volatile compounds such as n-caproic acid, isoamyl acetate, n-decyl alcohol, β-ionone, linalool, and ethyl caporate. The sensitivity of the sensor ranges from 10 −6~10 −7 g, fully correlated with the olfactory threshold values of human noses. An array of six sensors consisting of five fractionated ORPs and one referenced phospholipid probe is able to respond to different odorants and form a typical fingerprint for each odorant.

Practical Odour Nuisance Gauging: Two Case Studies of Objective Odour Quantification in Agriculture and Industry

The quantification of odour problems associated with liquid and solid agricultural and industrial wastes has long been a controversial subject because of the generally subjective nature of the methods used in evaluating odour related complaints. To overcome this problem, a scheme was devised which included three separate quantification techniques, researched both locally and abroad. The collective scheme was introduced as the “Practical Odour Nuisance Gauging” method. This technique has been applied in a number of local odour related investigations and updated throughout so as to render it more practical and acceptable. Two case studies are included to serve as examples of the application of this scheme. It is shown that odour nuisances were indeed present or were likely to occur at the sites investigated.

The effect of pH indicators chlorphenol red and bromocresol purple on the in vitro production of lepidopteran nuclear polyhedrosis viruses

The colorimetric sensor array technology simulates human olfaction to analyze, identify and examine complex gas and volatility based on chem-responsive dyes. Unlike human olfaction and electronic noses, colorimetric sensor array is more objective and not susceptible to interference. In additional, with the visualization, rapidity and non-destruction of analysis, colorimetric sensor array has been increasingly applied in food science and industry.This review focuses on the colorimetric sensor array technology and its major applications in food industry. Technical considerations associated with the chemo-responsive dyes, substrate materials, and data processing methods are discussed. In application, any type of food samples including solid, liquid food samples could be directly analyzed using colorimetric sensor array. Additionally, the recent development, and future research trends are also involved.The colorimetric sensor array technology offers an exciting method to establish the correlation between the output of a colorimetric sensor array and the odor components, thereby enabling visual quantification of odors. It provides a potential odor-image-based monitoring tool for the rapid, reliable and in-line assessment of food safety and quality.

Olfactory Quantification of Sewage Odors

Procedures for measuring sewage odor are examined and a standard odor unit is recommended for odor quantification of a mixture of odorous gases. Field experiments involving simultaneous measurements of odor and hydrogen sulfide levels at two wastewater sites handling significantly different types of wastes were carried out. Odor level was measured with a dynamic olfactometer, while hydrogen sulfide concentration was determined with a paper‐tape densitometer. Results reveal that the odor concentration (Cs) of sewage air can be correlated with the hydrogen sulfide concentration [H2S] by an equation of the form Cs=m[H2S]n, in which m and n are empirical parameters. Different values of m and n are obtained for the two sites investigated. The odor levels exerted by sewage air were also compared against that exerted by a commercially prepared hydrogen sulfide gas standard. These results reveal a natural masking effect of hydrogen sulfide odor in sewage air.