ODOR PERCEPTION OVER LIQUID EMULSIONS CONTAINING SINGLE AROMA COMPOUNDS: EFFECTS OF AROMA CONCENTRATION AND OIL VOLUME FRACTION

This study aimed to check the hypothesis that aroma concentration in the aqueous phase of an oil-in-water emulsion controlled the odor intensity of single aroma compounds. A set of flavored oil-in-water emulsions, prepared according to a 2² experimental design (aroma concentration, oil volume fraction) with two central points, was assessed for odor intensity by a 24-member panel during four sessions. In each session, three of the four-studied aroma molecules (benzaldehyde, ethyl butyrate, linalool and acetophenone) were investigated. Whatever the aroma, the experimental data showed that the oil volume fraction of the emulsion (from 0.12 to 0.48) did not influence the odor intensity. For each emulsion composition, aroma concentrations at equilibrium in both phases were calculated using the oil-water partition coefficient of the compound. Odor intensities, estimated from aroma concentration in the aqueous phase using previously reported modeling of odor intensity above water solutions, were then compared to experimental data. It is confirmed that the perceived odor intensity is governed by the aroma concentration in the aqueous phase at the time of the trial and not by the averaged apparent concentration in the emulsion.     

Characteristic odor components of Citrus reticulata Blanco (ponkan) cold-pressed oil

Citrus reticulata Blanco (ponkan) cold-pressed oil and its oxygenated fraction were studied by analytical (GC and GC/MS) and sensory analyses. The monoterpene group was predominant, accounting for more than 89.6% (w/w), of which limonene was the most abundant (80.3%). Among the oxygenated compounds, octanal and decanal were the major ones among 12 aldehydes accounting for >1.5%; six alcohols were identified with a total concentration of >0.7%, while oxides, ketones and esters did not quantitatively or qualitatively contribute to the oil. Sniffing the ponkan cold-pressed oil and its oxygenated fraction demonstrated that octanal and decanal were the characteristic odor components of ponkan. Reconstruction of the ponkan aroma model and its sensory evaluation by a hedonic test were performed, showing that, in addition to octanal and decanal which played important roles, (R)-(+)-limonene contributed to the aroma model as a background component, making the aroma model very similar to that of the original.     

Characteristic Odor Components of Citrus reticulata Blanco (Ponkan) Cold-pressed Oil

Citrus reticulata Blanco (ponkan) cold-pressed oil and its oxygenated fraction were studied by analytical (GC and GC/MS) and sensory analyses. The monoterpene group was predominant, accounting for more than 89.6% (w/w), of which limonene was the most abundant (80.3%). Among the oxygenated compounds, octanal and decanal were the major ones among 12 aldehydes accounting for >1.5%; six alcohols were identified with a total concentration of >0.7%, while oxides, ketones and esters did not quantitatively or qualitatively contribute to the oil. Sniffing the ponkan cold-pressed oil and its oxygenated fraction demonstrated that octanal and decanal were the characteristic odor components of ponkan. Reconstruction of the ponkan aroma model and its sensory evaluation by a hedonic test were performed, showing that, in addition to octanal and decanal which played important roles, (R)-(+)-limonene contributed to the aroma model as a background component, making the aroma model very similar to that of the original.     

Partition coefficient and comparative olfactometry

The air/water partition coefficients of many odorants can becalculated from available data on their vapor pressures andsolubilities at 25°. A gas-flow method is described forobtaining equilibrium concentration data to calculate the coefficientsof certain odorants for which theoretical or gas chromatographictechniques are not applicable. It is shown that the odor thresholdsobtained in airdilution olfactometry agree with those measuredby sniff tests on aqueous dilutions, when the air/water partitioncoefficient is taken into consideration. Similar calculationsinvolving the oil/water partition coefficient show close correspondencebetween thresholds measured in water or safflower oil dilution.A conversion factor was obtained for comparing squeeze-bottlepair tests with stoppered flask 2/5 tests in the measurementof olfactory threshold.     

USE OF SENSORY EVALUATION FOR MEASURING DEODORIZING EFFECTS OF AN AIR CONDITIONER

The application of sensory methodology for measuring deodorizing effect of an air conditioner equipped with electric plasma was introduced. Deodorizing effect was measured using chemical and sensory methods at different time (0, 30 and 60 min) and mode (control, blowing and cooling) of an air conditioner. Smoke from a roll of cigarette in a closed room was used as a source of odor and the concentrations of acetic acid and ammonia were measured as odorous chemical components. As one of the sensory methods triangle test was used and as a first step to obtain deodorizing effects by triangle test, the threshold of each panelist was obtained as the log dilution ratio of odor concentration at which the difference from odorless air was detected. The odor concentration at each time and mode was calculated using the threshold of the panel and the deodorizing effect was obtained on the basis of the odor concentration. In addition to a triangle test, scaling methods such as category scaling or magnitude estimation were used to measure deodorizing effect of an air conditioner. Deodorizing effects by scaling methods were calculated based on odor intensity with time at each mode. The regression analysis was done between the efficacy of deodorizing effect by sensory test and those by acetic acid and ammonia, the R² values of the regression equations for triangle test, category scale, and magnitude estimation were 0.84, 0.72 and 0.69, respectively. Deodorizing effect by triangle test explained the decrease of acetic acid and ammonia better than those by category scaling or magnitude estimation while high cost and time consuming labor involved in triangle tests reduced the merit. The results of this study demonstrated that various sensory methods could be used to measure deodorizing effect of air conditioners and further researches on fast and reliable methods are needed to establish the official procedures.     

Evaluation of characteristic aroma compounds of Citrus natsudaidai Hayata (Natsudaidai) cold-pressed peel oil

The characteristic aroma compounds of Citrus natsudaidai Hayata essential oil were evaluated by a combination of instrumental and sensory methods. Sixty compounds were identified and quantified, accounting for 94.08% of the total peel oil constituents. Limonene was the most abundant compound (80.68%), followed by gamma-terpinene (5.30%), myrcene (2.25%) and alpha-pinene (1.30%). Nineteen compounds which could not be identified in the original oil were identified in the oxygenated fraction. Myrcene, linalool, alpha-pinene, beta-pinene, limonene, nonanal, gamma-terpinene, germacrene D, and perillyl alcohol were the active aroma components (FD-factor > 3(6)), whereas beta-copaene, cis-sabinene hydrate and 1-octanol were suggested as characteristic aroma compounds, having a Natsudaidai-like aroma in the GC effluent. Three other compounds, heptyl acetate, (E)-limonene oxide and 2,3-butanediol, which each showed a high RFA value (>35) were considered to be important in the reconstruction of the original Natsudaidai oil from pure odor chemicals. The results indicate that 1-octanol was the aroma impact compound of C. natsudaidai Hayata peel oil.     

Comparison of Three Different Extraction Methods on Osmanthus Volatile Oil: Aroma and Biological Activity

The osmanthus volatile oil was welcomed by consumers even if the high price since the unique and pleasant odor. Meanwhile, the low yield of osmanthus volatile oil restricts industrial production. In this work, an osmanthus volatile oil was obtained by means of a novel ultrasonic-assisted flash extraction method and was compared with the oil from hydrodistillation and supercritical fluid extraction on yield, aroma, and biological activities. The volatile oil obtained from the ultrasonic-assisted flash extraction was obtained with the petroleum ether and got a high yield at 3.51 % within a 40-min process, an increase of nearly 81 % from the single solvent extraction. This oil also showed a high aroma intensity and aroma compound concentration. Meanwhile, the oil also has the highest antioxidant ability but lower antibacterial activity against oil from hydrodistillation. It was considered that this work was helpful for the optimization of the extraction method of osmanthus volatile oil.     

TIME-INTENSITY MEASUREMENT OF MATRIX EFFECTS ON RETRONASAL AROMA PERCEPTION

A computerized time intensity procedure was used to evaluate the retronasal aroma intensity of vanillin and limonene in oil/water emulsion. The maximum perceived retronasal intensity of limonene was decreased as oil content in the emulsion increased, but temporal perception (time to maximum intensity and total duration of perception) was not affected. Total duration of vanillin retronasal aroma increased as oil content increased, and salivary flow rate had a significant effect on perception of vanillin aroma. These results suggest that time intensity measurements may be a valuable tool for evaluating the effects of matrix interactions on retronasal aroma intensity.     

Odor reduction rate in the confinement pig building by spraying various additives.

The objective of this on-site experiment was to evaluate and compare the effectiveness of currently utilized various additives, i.e. tap water, salt water, digested manure, microbial additive, soybean oil, artificial spice and essential oil, to reduce odor emissions from the confinement pig building. Odor reduction rates were evaluated with respect to sensual odor (odor concentration index, odor intensity and odor offensiveness) and odorous compounds (ammonia and sulfuric odorous compounds). Of the additives investigated in this study, salt water, artificial spice and essential oil had a positive effect on reducing odor generation. The effectiveness of salt water was only observed on ammonia, showing the reduction rates as a function of time (t=immediately, 1h, 3h, 5h, and 24h after spraying) were 0.1%, 20%, 36%, 11% and 0.2% as compared to initial level before spraying. The odor intensity and offensiveness were lessened by spraying artificial spice and essential oil of which maximum reduction rates ranged from 60% to 80%. Additionally, the essential oil had a significant effect on reducing sulfuric odorous compounds for 24h after spraying, which implicates that it functioned as not only a masking agent but also as an antimicrobial agent.     

Evaluation of Characteristic Aroma Compounds of Citrus natsudaidai Hayata (Natsudaidai) Cold-Pressed Peel Oil

The characteristic aroma compounds of Citrus natsudaidai Hayata essential oil were evaluated by a combination of instrumental and sensory methods. Sixty compounds were identified and quantified, accounting for 94.08% of the total peel oil constituents. Limonene was the most abundant compound (80.68%), followed by γ-terpinene (5.30%), myrcene (2.25%) and α-pinene (1.30%). Nineteen compounds which could not be identified in the original oil were identified in the oxygenated fraction. Myrcene, linalool, α-pinene, β-pinene, limonene, nonanal, γ-terpinene, germacrene D, and perillyl alcohol were the active aroma components (FD-factor > 3⁶), whereas β-copaene, cis-sabinene hydrate and 1-octanol were suggested as characteristic aroma compounds, having a Natsudaidai-like aroma in the GC effluent. Three other compounds, heptyl acetate, (E)-limonene oxide and 2,3-butanediol, which each showed a high RFA value (>35) were considered to be important in the reconstruction of the original Natsudaidai oil from pure odor chemicals. The results indicate that 1-octanol was the aroma impact compound of C. natsudaidai Hayata peel oil.     

Pulse Width Modulation Applied to Olfactory Stimulation for Intensity Tuning

For most olfactometers described in the literature, adjusting olfactory stimulation intensity involves modifying the dilution of the odorant in a neutral solution (water, mineral, oil, etc.), the dilution of the odorant air in neutral airflow, or the surface of the odorant in contact with airflow. But, for most of these above-mentioned devices, manual intervention is necessary for adjusting concentration. We present in this article a method of controlling odorant concentration via a computer which can be implemented on even the most dynamic olfactometers. We used Pulse Width Modulation (PWM), a technique commonly used in electronic or electrical engineering, and we have applied it to odor delivery. PWM, when applied to odor delivery, comprises an alternative presentation of odorant air and clean air at a high frequency. The cycle period (odor presentation and rest) is 200 ms. In order to modify odorant concentration, the ratio between the odorant period and clean air presentation during a cycle is modified. This ratio is named duty cycle. Gas chromatography measurements show that this method offers a range of mixing factors from 33% to 100% (continuous presentation of odor). Proof of principle is provided via a psychophysical experiment. Three odors (isoamyl acetate, butanol and pyridine) were presented to twenty subjects. Each odor was delivered three times with five values of duty cycles. After each stimulation, the subjects were asked to estimate the intensity of the stimulus on a 10 point scale, ranging from 0 (undetectable) to 9 (very strong). Results show a main effect of the duty cycles on the intensity ratings for all tested odors.     

ALTERNATIVE ANALYSES OF MAGNITUDE ESTIMATION DATA

Three methods of standardizing magnitude estimation data, external calibration, modulus normalization, and equalization were examined using a sensory evaluation data set arising from an incomplete block experiment testing five gels of varying firmness. Both the original data and a logarithmic transformation of the data were analyzed. Instrumental data were also collected. When untransformed data were analyzed the method of standardization profoundly affected tests of significance, coefficients of variation (%CV), and estimation of the power function relating the sensory data to the concentration of the underlying gel. The logarithmically transformed data lead to results independent of the standardizing technique and with higher F-ratios, lower %CV's and normally distributed errors.     

EFFECTS OF DIFFERENT FACTORS ON SENSORY ATTRIBUTES, OVERALL ACCEPTANCE AND PREFERENCE OF ROOIBOS (ASPALATHUS LINEARIS) TEA

Effects of serving size, gender, age, tea type, tea‐making technique and water quality on the sensory attributes (appearance, aroma and taste), overall acceptability and preference of Rooibos tea were investigated. In general, there were significant effects of age and main factor interactions on the attributes and product acceptability (P ≤ 0.05). The interaction of serving size, gender and age affected the acceptability of Rooibos (P ≤ 0.05). Although there was significant difference between natural and vanilla‐flavored tea in terms of color, clarity, odor and taste (P ≤ 0.05), no difference was observed in the product acceptability (P > 0.05). The tea‐making technique only affected the odor, with traditionally brewed tea having lower intensity scores than the infused tea. The tea prepared using natural spring water was found to be clearer and had higher acceptability scores than the tea prepared using tap water (P ≤ 0.05). There was no existing significant preference for the natural Rooibos over the vanilla‐flavored one, and the traditionally brewed tea over the infused one; however, the tea prepared using the spring water was preferred over the one prepared using tap water.