Sensory Threshold Levels Research Articles

Antioxidant Effect of Ocimum basilicum Essential Oil and Its Effect on Cooking Qualities of Supplemented Chicken Nuggets.

A commonly observed chicken meat issue is its lipid oxidation that leads to deterioration of its organoleptic and nutritional properties and its further-processed products. Basil (Ocimum basilicum L.) is one of the traditional culinary herbs exhibiting food preservation properties. The current study investigated the essential oil composition, antioxidant activity and in vitro cytotoxic capacity of the essential oil of basil indigenous to Pakistan. GC–MS analysis of the essential oil revealed the presence of 59 compounds that constituted 98.6% of the essential oil. O. basilicum essential oil (OB-EO) exhibited excellent antioxidant activity, i.e., IC50 5.92 ± 0.15 µg/mL as assayed by the DPPH assay, 23.4 ± 0.02 µmoL Fe/g by FRAP, and 14.6 ± 0.59% inhibition by H2O2. The brine shrimp lethality assay identified an average mortality of ~18% with OB-EO at 10–1000 µg/mL, while that of the same concentration range of the standard drug (etoposide) was 72%. OB-EO was found to be non-toxic to HeLa and PC-3 cell lines. TBARS contents were significantly decreased with increase of OB-EO in chicken nuggets. The lowest TBARS contents were recorded in nuggets supplemented with 0.3% OB-EO, whereas the highest overall acceptability score was marked to the treatments carrying 0.2% OB-EO. The results suggest OB-EO as a promising carrier of bioactive compounds with a broad range of food preservation properties, and which has a sensory acceptability threshold level for chicken nuggets falling between 0.2-0.3% supplementation. Future research must investigate the antibacterial impact of OB-EO on meat products preserved with natural rather than synthetic preservatives.

The Influence of Whole-Body Vibration on Cardiovascular Parameters and Changes in the Perception of an External Stimulus in Postmenopausal Women

Introduction: Medical science is constantly looking for effective methods to prevent involutional changes. Whole-body vibration training is a promising form of systemic rehabilitation. Aim: The aim of the study was to assess the effect of whole-body vibration on basic cardiovascular parameters (heart rate and blood pressure) and changes in the perception of an external stimulus in postmenopausal women with different body composition. Material and methods: The study was pilot and involved 20 women. Before the procedure, the body composition analysis was performed using the Tanita analyser. All participants underwent a series of vibration massage treatments lasting 30 minutes. Blood pressure, heart rate and sensory threshold levels were measured before and after the vibrotherapy. Results: Diastolic blood pressure before vs. after (median; 74.20 vs. 71.45 mmHg; p=0.047), heart rate before vs. after (median; 67.40 vs. 66.00 bpm; p<0.001). Higher water content positively correlated with a decrease in diastolic blood pressure (R=0.51; p<0.05). The older the woman was, the less the heart rate decreased (R=-0.45; p<0.05). After vibrotherapy, the sensory threshold values in the non-dominant hand decreased slightly (p=0.076). The greater the visceral fat content (R=-0.48; p<0.05) and body weight (R=-0.56; p<0.05), the smaller was the improvement in the threshold. Conclusions: After whole-body vibration, the values of diastolic blood pressure and heart rate in the examined women were lower than those recorded before the procedure. It has been shown that the higher water content in the female body was associated with a greater reduction in diastolic blood pressure. However, the older the woman, the less was the decrease in heart rate. After the whole-body vibrotherapy, only a slight decrease in the sensory threshold was noted. However, it was found that in the studied women the greater the content of visceral fat tissue and the body weight, the smaller the change in sensory sensitivity.

Development and optimization of a quantitative analysis of main odorants causing off flavours in cork stoppers using headspace solid-phase microextraction gas chromatography tandem mass spectrometry.

A simple and sensitive method was developed and validated to simultaneously separate and determine the 2-Methoxy-3,5-dimethylpyrazine, 2-Isopropyl-3-methoxypyrazine, guaiacol, 2-Isobutyl-3-methoxypyrazine, 2-Methylisoborneol, geosmin, 2,4,6-Trichloroanisole, 2,3,4,6-Tetrachloroanisole, 2,4,6-Tribromoanisole and Pentachloroanisole in cork stoppers via headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography tandem mass spectrometry (GC-MS/MS). The influence of the fibre coating used, the extraction times and temperatures, the sodium chloride additions and the desorption temperatures were investigated. Once done, the optimial HS-SPME conditions established were divinylbenzene/carboxenpolydimethylsiloxane/polydimethylsiloxane (DVB/CAR/PDMS) fibres, a 50°C extraction temperature, 60-min extraction time, an ionic strength of 3-g sodium chlorid and a 290°C desorption temperature. The method showed a good linearity (R2 ≥ 0.994) within the tested range (from 0.1 to 50 ng L-1 ) for all the compounds. Using TCA-d10 and MIB-d3 as internal standards the precision, expressed as repeatability and reproducibility RSD, was <10% in both. Note that the limits of quantifications (LOQs) are below the sensory threshold levels for such compounds in water and wine. Good recoveries were obtained for cork macerates (from 100.4% to 126%) and when compared with other reported methods using HS-SPME in water and cork stopper samples, the present method had more analytes with the lowest limit of detection for most of the targeted compounds, along with good precision and recovery.

GC-Recomposition-Olfactometry (GC-R) and multivariate study of three terpenoid compounds in the aroma profile of Angostura bitters

Foods and beverage aroma results from multicomponent mixtures of volatile compounds present in the food that interact with olfactory receptors and produce a perceptual response in the brain. However, the perceptual interactions that occur when complex odor mixtures are combined are not well understood. Here we used Gas chromatography-Recomposition-Olfactometry (GC-R) to better understand the role that individual compounds have on the perceived sensory aroma of bitters. Bitters are the concentrated alcoholic extract of flavorful plant materials with a wide range of complex sensory and chemical aroma profiles that have not been extensively studied. Previously, we demonstrated that Angostura bitters are characterized by complex aroma attributes described as cola, ginger, orange peel, and black pepper and that the volatile composition of Angostura bitters is predominantly composed of terpenoids. Using GC-R to create in-instrument mixtures of the Angostura headspace extracts, the sensory attributes of Angostura extracts with linalool, α-terpinyl-acetate and caryophyllene omitted were evaluated. The omission experiments demonstrated direct and indirect effects of the individual compounds on the aroma attributes of Angostura bitters, through masking, additive, and synergistic interactions. Caryophyllene in particular, which was present in the headspace extracts at concentration only slightly above sensory threshold levels, had a large and unexpected impact on the sensory properties of the mixtures and may be most responsible for the aromas associated with the whole sample. The GC-R and statistical approaches used here provided valuable tools to reveal relationships among individual compounds and aroma attributes of foods that have not been currently theorized using existing analytical approaches.

Quantitative analysis of mousy off-flavour compound 2-acetyl tetrahydropyridine in wine using liquid chromatography tandem mass spectrometry interfaced with atmospheric chemical ionisation

2-Acetyltetrahydropyridine (ACTPY), tautomers of 2-acetyl-1,4,5,6-tetrahydropyridine and 2-acetyl-3,4,5,6-tetrahydropyridine, is reported as one of the major compounds responsible for mousy off-flavour wine. A simple and rapid method for the quantitation of ACTPY in wine using HPLC-APCI-MS/MS was developed. Only filtration and basification were required for sample preparation prior to analysis. The analytical run time was approximately 17 min for one sample. Precision and accuracy tests confirmed that the method was highly reliable and robust. Limits of quantitation (LOQ) for red and white wines were estimated to be 0.23 μg L−1, which was sufficiently sensitive to allow the quantitation of ACTPY at its odour threshold level in water. The method can be implemented for routine objective screening of wines for mousy off-flavour, to determine sensory threshold levels in wine and to aid further research aiming to reduce the occurrence of this fault in wine.

Effects of galvanic vestibular stimulation with white and pink noise on upright standing sway for healthy adults

It has been reported that the noisy galvanic vestibular stimulation (n-GVS) could improve upright body sway in healthy subjects. It is unclear which sort of noise is appropriate for n-GVS. Our study aimed to investigate the effects of n-GVS with white and pink noise for upright standing sway in healthy adults. Seventeen healthy adults (11 men; age = 21.9 ± 1.6 years) were instructed to stand on a force plate with foamed rubber and wore an eye-mask and ear-muffs. Center of pressure (CoP) displacement was measured for 60-s with 1000 Hz sampling. We generated the 30-s white and pink noise and added this to the galvanic vestibular stimulation. We applied the n-GVS to the participants and stimulus intensities were 30, 50, 70, 90, and 110% of each participant's electric sensory threshold level (10 conditions: 2 noise × 5 intensities). Right side anode n-GVS was applied via both mastoids 30-s after the measurement was started. We used the anteroposterior (AP) and mediolateral (ML) direction of standard deviations (SD) and total length (LNG) of CoP displacement as measurement variables. Each condition's variable was represented as a percentage value based on the initial 30-s measurement data (pre-n-GVS). We compared these variables with two-way repeated measures Anovas and t -test as post-hoc test (significance level was 5%). In the AP- and ML-LNG, significant intensity effects were observed with ANOVAs (both of P < 0.05). Conversely, there were no main effects and interactions in the AP- and ML-SD. In the AP-LNG, the 90% intensity condition showed significantly smaller values compared to 50, 70, and 110% in the pink noise. We found that the n-GVS improved the CoP displacement length but not the width and the optimal stimulus intensity was at around 90% of the sensory threshold level with pink noise.

A SOD2 Polymorphism is Associated with Abnormal Quantitative Sensory Testing in Type 2 Diabetic Patients.

Diabetes mellitus (DM) affects peripheral nerves inducing diabetic polyneuropathy (DPN). Mitochondrial dysfunction and oxidative stress are potential causes of DPN. Nerve conduction studies were performed in 20 type 2 DM patients (11 with DPN) and 15 healthy controls. Perception threshold values of cold, warm and vibration were measured by quantitative sensory testing. Variants of a superoxide dismutase 2 (SOD2) gene single nucleotide polymorphism (SNP) (rs5746136) were determined by polymerase chain reaction (PCR) and following NexteraXT DNA Library. DPN patients showed significantly increased threshold values. DM patients without DPN and healthy controls showed comparable values. TT variant of the SOD2 SNP was more prevalent in DM and DPN patients. DM patients with the TT variant displayed increased perception threshold values. Quantitative sensory testing is not superior to standard nerve conduction studies in DPN. Carriers of SOD2 SNP manifested increased sensory threshold levels which is important in further corroborating the link between oxidative stress and DPN.

Headspace solid-phase microextraction coupled to gas chromatography-tandem mass spectrometry for the determination of haloanisoles in sparkling (cava and cider) and non-sparkling (wine) alcoholic beverages

ABSTRACTA highly sensitive analytical method was developed to determine 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), 2,4,6-tribromoanisole (TBA) and 2,3,4,5,6-pentachloroanisole (PCA) in sparkling alcoholic beverages. The method was based on the use of headspace solid-phase microextraction (HS-SPME) using a polydimethylsiloxane (PDMS) fibre. It was coupled to gas chromatography-triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) for the detection and quantification of the target haloanisoles. The method was fully automated and no sample preparation was needed. The method was validated for alcoholic beverages. The influence of CO2 on the extraction efficiency was also evaluated for the studied sparkling drinks (cava and cider). All the calibration curves showed good linearity (R2 > 0.98) within the tested range (1–50 ng l−1). Recoveries were evaluated at three different levels (1, 5 and 50 ng l−1) and were always between 71% and 119%. Precision was expressed as relative standard deviation (RSD), and was evaluated as intra- and inter-day precisions, with values ≤ 22% in both cases. Limits of quantitation (LOQs) were ≤ 0.91 ng l−1, which are below the sensory threshold levels for such compounds in humans. The validated method was applied to commercial samples, 10 cavas and 10 ciders, but it was also used for the analysis of nine red wines and four white wines, demonstrating the further applicability of the proposed method to non-sparkling beverages. TCA was detected in most samples at up to 0.45 ng l−1.

A single nucleotide polymorphism in the CYP2E1 gene promoter affects skatole content in backfat of boars of two commercial Duroc-sired crossbred populations

The prevention of unpleasant boar taint is the main reason for castration of male piglets. This study aimed to investigate how the malodorous compound skatole is affected by a single nucleotide polymorphism (g.2412 C>T at −586 ATG) in the porcine cytochrome p450 II E1 (CYP2E1) gene. 119 boars of two commercial Duroc-sired crossbred populations raised at different farms were investigated. Skatole and androstenone in backfat averaged 114±125ng/g and 1206±895ng/g melted fat, respectively. The frequency of the genotypes CC, CT, and TT was 25, 52, and 23%, respectively. CC boars had the highest average skatole levels (175ng/g) compared to CT (92ng/g) and TT (93ng/g). Applying suggested sensory threshold levels for skatole (>150ng/g) and androstenone (>2000ng/g), 30% of the carcasses may be unacceptably tainted while the proportion of tainted carcasses is significantly higher within genotype CC (56.7%) compared to genotypes CT (24.3%) and TT (14.8%). Effective reduction of tainted carcasses appears feasible applying marker assisted selection.

High-Throughput, Sub ng/L Analysis of Haloanisoles in Wines Using HS-SPME with GC-Triple Quadrupole MS

Haloanisole contamination causes development of “cork taint,” a musty off-aroma in affected wines. Cork taint results in significant economic loss for the wine and allied industries every year, therefore extensive quality-control procedures have been established at wineries and cork production facilities to monitor levels of haloanisoles in cork products. Because of the extremely low human sensory thresholds for these compounds (~1 to 4 ng/L for 2,4,6-trichloroanisole in wine), highly sensitive analytical methods are needed to detect the haloanisoles at threshold concentrations or lower. We present a method for the simultaneous analysis of four haloanisoles in wine—2,4,6-trichloroanisole (TCA); 2,3,4,6-tetrachloroanisole (TeCA); 2,3,4,5,6-pentachloroanisole (PCA); and 2,4,6-tribromoanisole (TBA)—that have been frequently associated with cork taint aromas in wines. Headspace solid-phase microextraction (HS-SPME) coupled to a GC-triple quadrupole MS was used to obtain limits of quantification that were ≤1.0 ng/L and below sensory threshold levels. The method is fully automated, requires no sample preparation other than the addition of internal standards, and is high throughput, with a 10-min extraction time and a 5-min incubation prior to extraction. This method can be readily adapted to screen for haloanisoles in cork extracts.

Sickle cell disease and pain: potential dysfunction in A delta fiber transmission

Although sickle cell disease is generally characterized by varying degrees and patterns of clinical manifestations, its major features usually include severe episodes of pain. As part of a comprehensive pain assessment protocol on mechanisms of sickle cell pain, we are investigating how pain and inflammatory processes may be triggered in part by the disruption of normal NO pathways. Qualitative sensory testing (QST) procedures were conducted on subjects seen at the National Institutes of Health (NIH) Clinical Center, Bethesda, Md. Average age of subjects is 44.6 years (range: 31 to 52); 60% female; 30% male; 100% of the subjects reported experiencing chronic daily or almost daily pain. QST was used to assess experimental sensory and pain threshold levels, quantify presence of hyperalgesia, and compare pain threshold, detection threshold, and the degree of temporal summation of any second pain in response to thermal stimulation. All subjects reported heat thresholds within normal limits (48.7oC + or - 1.73 oC); while none of the sickle cell subjects reported cold thresholds within normal limits (2.3oC + or - 2.0o C). One subject did not report any perception of cold pain and the procedure was stopped to avoid tissue damage. This novel observation may have implications for understanding pain perception in people with sickle cell disease.

Cold atmospheric pressure plasma treatment of ready-to-eat meat: Inactivation of Listeria innocua and changes in product quality

The application of cold atmospheric pressure plasma for decontamination of a sliced ready-to-eat (RTE) meat product (bresaola) inoculated with Listeria innocua was investigated. Inoculated samples were treated at 15.5, 31, and 62 W for 2–60 s inside sealed linear-low-density-polyethylene bags containing 30% oxygen and 70% argon. Treatments resulted in a reduction of L. innocua ranging from 0.8 ± 0.4 to 1.6 ± 0.5 log cfu/g with no significant effects of time and intensity while multiple treatments at 15.5 and 62 W of 20 s with a 10 min interval increased reduction of L. innocua with increasing number of treatments. Concentrations of thiobarbituric acid reactive substances (TBARS) increased with power, treatments and storage time and were significantly higher than those of control samples after 1 and 14 days of storage at 5 °C. However, the levels were low (from 0.1 to 0.4 mg/kg) and beneath the sensory threshold level. Surface colour changes included loss of redness of ∼40% and 70% after 1 and 14 days of storage, respectively, regardless of plasma treatment. The results indicate that plasma may be applicable in surface decontamination of pre-packed RTE food products. However, oxidation may constitute an issue in some products.

Analysis of Volatile Organic Sulfur Compounds in Wine Using Headspace Solid-Phase Microextraction Gas Chromatography with Sulfur Chemiluminescence Detection

A procedure to quantify volatile, organic sulfur compounds in wines was developed using solid-phase microextraction to preconcentrate the analytes followed by gas chromatography and detection with a sulfur chemiluminescence detector. The compounds studied (hydrogen sulfide, carbon disulfide, methanethiol, ethanethiol, dimethyl sulfide, diethyl sulfide, dimethyl disulfide, and diethyl disulfide) have low sensory thresholds and contribute aromas ranging from rotten egg to cabbagelike in wines. These compounds, particularly the thiols, are very sensitive to oxidation. In the developed method, several steps were taken to minimize effects of oxidation and artifact formation, including the use of internal standards and air exclusion during sample preparation. However, oxidation could not be completely prevented, making it difficult to obtain acceptable calibration curves in model wines. Therefore, to correct for these effects, the method of standard addition was used to measure the concentrations of sulfur compounds in wines. The developed method was shown to be reproducible ( 97%) and limits of detection similar to or below sensory threshold levels. Using the developed method, a range of sulfur compounds were identified in wines associated with sensory descriptors characteristic of the S-containing compounds.

Evaluation of geosmin and 2-methylisoborneol off-flavour in smoked rainbow trout fillets using instrumental and sensory analyses

Secondary metabolites produced by cyanobacteria and other microorganisms include odorous compounds that can taint aquaculture products, rendering them unsalable. Many wild and cultured fish species are affected by off-flavour. Herein, we describe off-flavour occurrence in rainbow trout raised in a recirculation trout production system in Denmark. Smoked fish from two facilities contained MIB concentrations as much as 100X sensory threshold levels.

OPTIMIZATION OF THE SENSORY ACCEPTABILITY OF A REDUCED SALT MODEL READY MEAL

ABSTRACT The aim of this study was to examine the effect of salt levels on the sensory acceptability of a model frozen chicken curry ready meal. A sample product with typical commercial salt levels (0.6%, control) and a low‐salt chicken curry ready meal (0.2%) were prepared using a recipe supplied by an industrial partner. Salt was then added to the low‐salt meal at levels ranging from 0 to 1.3%, giving a range of meals with final salt concentrations between 0.2 and 1.5%. Sensory trials incorporating paired comparison, triangle, preference and ranking tests indicated that salt levels in a chicken curry ready meal could be reduced to a level of 0.4% without detecting a difference in saltiness when compared to a typical commercial added salt level of 0.6%. Results indicated that the sensory threshold level for salt in this meal was 0.2%. Incorporation of a number of different commercial salt substitutes allowed a further reduction in salt levels of 0.2% and to a final concentration of 0.2% without panelists detecting a noticeable difference in saltiness. PRACTICAL APPLICATIONSHigh dietary salt intake is now recognized as an important casual factor in the rise in blood pressure with age in industrialized countries such as Ireland. Irish consumers are increasingly purchasing ready meals because of lifestyle demands leaving less time available to prepare meals from fresh ingredients. Health agencies throughout the world are growing increasingly concerned with the high intake of nondiscretionary sodium from salt and sodium containing additives used in these meals. The Food Safety Authority of Ireland (FSAI) has set a long‐term goal to reduce the average population intake of salt from 10 to 6 g a day by 2010 through a partnership approach with the food industry (FSAI). This project aims to produce a low‐salt chicken curry ready meal that will aid the FSAI in achieving this national health strategy goal and provide technical data on reformulation strategies and sensory properties for ready‐meal producers.

Plantar tactile sensory thresholds in healthy men and women

Objective The purpose of this study was to determine tactile sensory threshold levels on the plantar surface of the feet in healthy subjects as well as assessing if differences existed based on gender or between extremities. Method Forty subjects, 20 men and 20 women, consented to participate in the study. Tactile sensory thresholds were determined over the heel, lateral midfoot, medial midfoot, lateral forefoot, medial forefoot, and hallux on the plantar surface of the foot using Semmes–Weinstein monofilaments. A multiple-step algorithm was used for testing and the subject determined the tactile threshold for a region verbally. Results The results indicate that plantar tactile sensation does not differ between the left and right feet, but differences do exist between men and women in all regions except the hallux. The heel region tactile threshold was found to be significantly higher than all other regions. The mean tactile sensitivity for both the right and left feet was the 3.61 monofilament. Conclusions This is one of few investigations that have attempted to assess plantar sensory thresholds in a healthy group of men and women. The findings of this study may prove useful for further investigation into the assessment of the effect of foot orthoses and insoles on the cutaneous tactile sensory system.

Effects of Surface Electrical Stimulation Both at Rest and During Swallowing in Chronic Pharyngeal Dysphagia

We tested two hypotheses using surface electrical stimulation in chronic pharyngeal dysphagia: that stimulation (1) lowered the hyoid bone and/or larynx when applied at rest, and (2) increased aspiration, penetration, or pharyngeal pooling during swallowing. Bipolar surface electrodes were placed on the skin overlying the submandibular and laryngeal regions. Maximum tolerated levels of stimulation were applied while patients held their mouth closed at rest. Videofluoroscopic recordings were used to measure hyoid movements in the superior-inferior and anterior-posterior dimensions and the subglottic air column position while stimulation was on or off. Patients swallowed 5 ml liquid when stimulation was off, at low sensory stimulation levels, and at maximum tolerated levels (motor). Speech pathologists, blinded to condition, tallied the frequency of aspiration, penetration, pooling, and esophageal entry from videofluorographic recordings of swallows. Only significant (p = 0.0175) hyoid depression occurred during stimulation at rest. Aspiration and pooling were significantly reduced only with low sensory threshold levels of stimulation (p = 0.025) and not during maximum levels of surface electrical stimulation. Those patients who had reduced aspiration and penetration during swallowing with stimulation had greater hyoid depression during stimulation at rest (p = 0.006). Stimulation may have acted to resist patients' hyoid elevation during swallowing.

Inhaled formaldehyde: Evaluation of sensory irritation in relation to carcinogenicity

Objectives The critical health effects of formaldehyde exposure include sensory irritation and the potential to induce tumours in the upper respiratory tract. In literature, a concentration as low as 0.24 ppm has been reported to be irritating to the respiratory tract in humans. Nasal tumour-inducing levels in experimental animals seem to be 1–2 orders of magnitude larger. In this paper, the subjectively measured sensory irritation threshold levels in humans are discussed in line with findings obtained in animal experiments. In addition, a Benchmark dose (BMD) analysis of sensory irritation was used to estimate response incidences at different formaldehyde concentrations. Methods Data on respiratory irritation and carcinogenicity of formaldehyde were retrieved from public literature and discussed. BMD analysis was carried out on human volunteer studies using the US-EPA BMD software. Results Subjective measures of irritation were the major data found in humans to examine sensory (eye and nasal) irritation; only one study reported objectively measured eye irritation. On a normalized scale, mild/slight eye irritation was observed at levels ⩾1 ppm, and mild/slight respiratory tract irritation at levels ⩾2 ppm. With the BMD software, it was estimated that at a level of 1 ppm, only 9.5% of healthy volunteers experience ‘moderate’ (i.e., annoying) eye irritation (95% upper confidence limit). An important factor modulating the reported levels of irritation and health symptoms most probably includes the perception of odour intensity. In several studies, the 0-ppm control condition was missing. From the results of the long-term inhalation toxicity studies in experimental animals, a level of 1 ppm formaldehyde has been considered a NOAEL for nasal injury. Conclusions Sensory irritation is first observed at levels of 1 ppm and higher. From both human and animal studies, it was concluded that at airborne levels for which the prevalence of sensory irritation is minimal both in incidence and degree (i.e., <1 ppm), risks of respiratory tract cancer are considered to be negligibly low.

Local effects in the respiratory tract: relevance of subjectively measured irritation for setting occupational exposure limits

Chemosensory effects of stimulation by a chemical can either be irritating (trigeminal stimulation) or odorous (olfactory stimulation) or both. For odorous irritants, a clear-cut distinction between odour and irritation is difficult to make. The differences in the lowest concentration found to be irritating to the respiratory tract in humans when compared to experimental animals has brought much debate in the process of setting occupational exposure limits (OELs) for such chemicals. In this paper it will be discussed as to how far subjectively measured sensory irritation threshold levels can be used to establish OELs. Data on respiratory irritation of four odorous irritants were retrieved from public literature and discussed, viz. acetone, formaldehyde, furfural and sulphur dioxide. Objective measures of irritation yielded results that differed from subjective evaluations. Important factors modulating the reported levels of irritation and health symptoms include the perception of odour intensity, exposure history and the individual's bias to report irritation on the basis of his/her prejudice or knowledge of the compound. Subjective measures alone are less appropriate for establishing sensory irritation thresholds of odorous irritants and are, therefore, less suitable to establish OELs without supporting evidence. Objectively measured irritation in humans, the Alarie assay (an experimental animal test assessing the concentration that results in a 50% reduction of the breathing frequency) and repeated exposure studies in animals may be of help to study objective irritation. If subjective measurements are used to study sensory irritation, the study design should at least include: measurement of both incidence and severity determined at several concentrations, an appropriate (0 ppm) control condition, preferably a non-irritant odorant control exposure, validated questionnaires and correct concentration measurements.

Registering the Response of Tissues Exposed to an Interferential Electric Current Stimulation

Electrotherapy is a treatment method in which an electric stimulus is used to achieve physiological changes in the body. When increasing the level of the electric stimulus, three sensory, three motor and a pain response can be found. In this paper the three sensory threshold levels (1st just noticeable weak tingling sensation, 2nd a very fine but definite tingling and 3rd moderate strong tingling) were studied with an interferential electric current stimulus. The interferential electric current can be achieved by summing two alternating currents with little different frequencies with each other. As a current source, the study used a value intended for interferential electric current therapy. The threshold value measurements were performed on 5 days to 6 volunteers. The method of limits is a frequently used technique for determining sensory thresholds where ascending or descending stimuli is used and the observer reports of the appearance or disappearance of the sensation, respectively. A Bekesy's algorithm is a threshold tracking method with a variable stimulus. They were used for controlling the interferential electric current stimulus, and hence, for studying the,thresholds. By using the method of limits, the measurements were done at three sensory threshold levels at interferential frequencies deltaf of 10 Hz, 30 Hz, 50 Hz, and 100 Hz caused by two sine waves, one with a frequency between 2490 Hz and 2400 Hz, and the other constant 2500 Hz. In the method based on Bekésy's algorithm the interferential frequency deltaf was increased from 1 Hz to 100 Hz by changing the first frequency from 2499 Hz to 2400 Hz and the measurement was repeated for all three sensory thresholds. The sensory thresholds for interferential current stimuli seem to be quite unaffected by the interferential electric current frequency among the healthy test persons, and no distinct interferential electric current frequencies at which the threshold values should be measured were found in this study.