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Most olfactometers used to study human olfaction have stimulus durations of more than 1 second and often lasting minutes(Dravnieks 1975; Leland et al. 2001; Schmidt and Cain 2010). During long stimulations, olfactory receptor responses and their resulting behaviors are modulated by adaptation and habituation to the stimulus(Pellegrino et al. 2017; Rankin 2009; Wilson and Linster 2008). For example, EOG results from the first deorphanized olfactory receptor tissue reached a maximum in ∼1 s, dropping to 1/2 maximum in the next second, and showing little signal reduction until the stimulation stopped after 6 seconds(Zhao et al. 1998). Longer stimulations can result in complete habituation; receptors still respond even though the behavior shows complete habituation (Barwich 2014). To minimize the effects of adaption and habituation on stimulus responses, the sniff olfactometer (SO) combined the precision of a blast olfactometer with the gentleness of a stream olfactometer by blasting a brief odorant puff (70ms duration) into a subject’s self-imposed inhalation air stream(Rochelle 2017; Rochelle et al. 2017b; Wyckoff and Acree 2017). Here we describe SO protocols for threshold determinations of odorants in aqueous headspaces using odorant recognition probabilities associated with Log(odorant-concentrations(Rochelle et al. 2017a)). During a single trial a subject, preconditioned to associate a veridical name with a given odor (e.g., a pyrazine with “nuts” when the odor was detected and “not nuts” if it wasn’t) was cued to “inhale” and 750ms later, a 15ml-70ms puff of odorant headspace was delivered into their inhalation airstream. A session consisted of 12 randomized double-blind trials of 3 different odorant concentrations. Additional sessions with different concentrations were conducted until the response probability to the samples ranged from below 0.2 to above 0.8. The robustness of the fitted function and the size of their confidence intervals depended on the difference between the concentrations of the odorants during a single session: small differences in sample concentration resulted in the data failing to fit a logistic function; larger concentration differences resulted in a better fit to the model. However, if one of the stimuli had no odorant at all i.e., a blank, the response to the blank was random.

Plant proteins can serve as inexpensive and environmentally friendly meat-replacements. However, poor taste characteristics and relatively low nutritional value prevent their full acceptance as meat substitutes. Fermentation of food has been historically used to improve the quality of foods. In this work we describe the improvement in digestibility, nutritional value, physical properties, and organoleptic characteristics, of a pea and rice protein concentrate blend through fermentation with shiitake mushroom mycelium. Ileal digestibility pig studies show increases in the DIAAS for the shiitake fermented pea and rice protein blend turning the blend into an “excellent source” of protein for humans. The fermentation also increases the solubility of the protein blend and reduces the content of the antinutrient compounds phytates and protease inhibitor. Mass spectrometry and sensory analyses of fermented protein blend indicates that fermentation leads to a reduction in off-note compounds substantially improving its organoleptic performance.

The purpose of this work is to determine the key odorants (KO) in shochu, a Japanese spirit made from sweet potato, barley, rice, soba, or sugarcane extract fermented with 20% rice koji. Each carbohydrate source produces a mild flavored spirit, but sweet potato produces shochu with a strong savory character. The KOs released by sweet potato, barley, rice, and sugarcane shochus were determined using headspace solid-phase micro-extraction (HS-SPME), gas chromatography-olfactometry (GC-O) dilution analysis to determine aroma characteristics, gas chromatography-mass spectrometry (GC-MS), and authentic standards to determine identity. The five top KOs found in sweet potato shochu were ethyl octanoate, ethyl cinnamate, 2-methyl-3-furanthiol, β-damascenone, 2-methyl-3-(methyldithio)-furan. The five top KOs in barley, rice, and sugarcane shochus were ethyl octanoate, ethyl hexanoate, isoamyl acetate, ethyl 2-methylbutanoate, and ethyl isobutyrate. The unique savory aroma of sweet potato was found to have higher levels of ethyl cinnamate, 2-methyl-3-furanthiol, and 2-methyl-3-(methyldithio)-furan while the five top KOs in barley-, rice-, and sugarcane-derived shochus were esters common in most alcoholic fermentations. There is growing evidence that a small number of odorants determine our perception of food aroma. The first challenge is to determine what these key odorants are and second to determine the rules used by the olfactory system to create odor images. This research identifies candidates for the unique aroma of sweet potato shochu.

This perspective examines psychophysical methods that may reveal the algorithms that encode odor images by integrating current data from sensory measurement into a computational model of odor perception. There is evidence that algorithms used by the nervous system to process odor sensations require input from only a few odorants, between three and eight. Furthermore, the number of recognizable odors in foods that contribute anything to the aroma of all foods is approximately 250. This may imply that it is the ratio of a small number of key odorants (KOs) that create a multitude of food odors. Studies with large mixtures of odorants (formulated to be of equal potency) show that a subject's ability to detect individual odorants in these mixtures was vanishingly small. These large mixtures had weak and nondescript but similar odor character. If only a few stimulants are used to represent complex images, it is direct evidence of the simplicity and therefore the tractability of the computational process.

Mechanistic approaches provide alternative solutions to in silico analyses of odorant molecules’ odor-structure relationships., Crucial for any hypothesis about odor coding is the classification and prediction of sensory qualities in chemical compounds. The relationship between perceptual quality and molecular structure has occupied olfactory scientists throughout the 20th century, but details of the mechanism remain elusive. Odor molecules are typically organic compounds of low molecular weight that may be aliphatic or aromatic, may be saturated or unsaturated, and may have diverse functional polar groups. However, many molecules conforming to these characteristics are odorless. One approach recently used to solve this problem was to apply machine learning strategies to a large set of odors and human classifiers in an attempt to find common and unique chemical features that would predict a chemical’s odor. We use an alternative method that relies more on the biological responses of olfactory sensory neurons and then applies the principles of medicinal chemistry, a technique widely used in drug discovery. We demonstrate the effectiveness of this strategy through a classification for esters, an important odorant for the creation of flavor in wine. Our findings indicate that computational approaches that do not account for biological responses will be plagued by both false positives and false negatives and fail to provide meaningful mechanistic data. However, the two approaches used in tandem could resolve many of the paradoxes in odor perception.

It is well known that lipid degradation modifies the aroma of the meat-like reaction of cysteine and reducing sugars. However, how aroma modification is caused by the odourants produced in the reaction mixtures is rarely studied. In the present study, 76 volatiles were reported from the reaction models containing cysteine and glucose with (or without) chicken fat or oxidized chicken fat. Using aroma extract dilution analysis (AEDA) of gas chromatography-olfactory (GC-O), 15 potent odourants were screened, whereby 12 of them were identified and quantified to be 1~77889 µg/kg of the reaction mixtures. Aroma models, with similarity ratings to the reaction mixtures (by sensory analysis) ranging as high as 90%, were prepared. Sensory assessment by omission study showed that the presence of fatty compounds from lipid degradation in the reaction mixtures although of low FD factors by GCO, nonetheless contributed the greatest to the alteration of overall aroma, followed by the quantitative reduction of the thiols from the Maillard reaction. The quantitative change of the heterocyclic odourants which formed from the Maillard reaction or the interaction of the Maillard reaction with lipid degradation was found to have a marginal impact. Copyright © 2015 John Wiley & Sons, Ltd.

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) is well-known to contribute "petrol" aromas to aged Riesling wines, but its prevalence and contribution to young Riesling or non-Riesling wines is not well understood. TDN concentrations were measured in 1-3-year-old varietal wines produced from Cabernet franc (n = 14 wines), Chardonnay (17), Cabernet Sauvignon (4), Gewurztraminer (4), Merlot (9), Pinot gris (6), Pinot noir (9), Riesling (28), or Sauvignon blanc (6). TDN concentrations in the Riesling wines, 6.4 ± 3.8 μg/L, were significantly higher than in all other varietals, 1.3 ± 0.8 μg/L. The odor detection thresholds for TDN were then determined in both model wine and a neutral white wine. Group sensory thresholds were found to be the same in both matrices, 2 μg/L, indicating little masking of TDN due to the odorants in the neutral white. The TDN sensory threshold was a factor of 10 below the previously reported odor threshold. On the basis of this revised threshold, 27 of 28 Riesling wines had suprathreshold TDN, whereas only 7 of 69 non-Riesling wines had suprathreshold TDN. The monoterpenes linalool and geraniol were also measured in the Riesling wines, and odor activity values (OAVs) were calculated for the monoterpenes and TDN. The OAV for TDN was higher than for the monoterpenes in 25 of 28 Riesling wines.

Native American grape (Vitis) species have many desirable properties for winegrape breeding, but hybrids of these non-vinifera wild grapes with Vitis vinifera often have undesirable aromas. Other than the foxy-smelling compounds in Vitis labrusca and Vitis rotundifolia , the aromas inherent to American Vitis species are not well characterized. In this paper, the key odorants in wine produced from the American grape species Vitis riparia and Vitis cinerea were characterized in comparison to wine produced from European winegrapes (V. vinifera). Volatile compounds were extracted by solid-phase microextraction (SPME) and identified by gas chromatography-olfactometry/mass spectrometry (GC-O/MS). On the basis of flavor dilution values, most grape-derived compounds with fruity and floral aromas were at similar potency, but non-vinifera wines had higher concentrations of odorants with vegetative and earthy aromas: eugenol, cis-3-hexenol, 1,8-cineole, 3-isobutyl-2-methoxypyrazine (IBMP), and 3-isopropyl-2-methoxypyrazine (IPMP). Elevated concentrations of these compounds in non-vinifera wines were confirmed by quantitative GC-MS. Concentrations of IBMP and IPMP were well above sensory threshold in both non-vinifera wines. In a follow-up study, IBMP and IPMP were surveyed in 31 accessions of V. riparia, V. rupestris, and V. cinerea. Some accessions had concentrations of350 pg/g IBMP or30 pg/g IPMP, well above concentrations reported in previous studies of harvest-ripe vinifera grapes. Methyl anthranilate and 2-aminoacetophenone, key odorants responsible for the foxiness of V. labrusca grapes, were undetectable in both the V. riparia and V. cinerea wines (10 μg/L).

The straight-chain aldehyde hexanal has a distinct “green-grassy” smell quite different from the similar “citrus-waxy”-smelling homologues heptanal to undecanal (Kittel et al., Chemosens Percept 1:235–241, 2008). Two prior studies demonstrated the absence of cross-adaptation between hexanal and three other homologues (Kurtz et al., Chemosens Percept 3:149–155, 2010) but a significant mixture suppression between the dissimilar-smelling odorants hexanal and octanal (Kurtz et al., Chemosens Percept 4:186–194, 2009). In contrast, this study of similar-smelling octanal and decanal showed little mixture suppression. In contrast to the hexanal and octanal adaptation, data from Kurtz et al. (Chemosens Percept 3:149–155, 2010) showed a significant cross-adaptation between octanal and decanal. The differences observed between mixture suppression and adaptation suggest that these two phenomena are processed separately.

Gas chromatography – Olfactometry (GC-O) purifies odorants and delivers them as 1 to 2 second doses to an olfactometer where their odor properties (quale and intensity) can be studied independent of other odors. Adding an odor to the olfactometer air before combining it with the GC effluent creates an odor pedestal upon which an odorant eluting from the GC can be studied to provide insight into mixture perception. This paper describes the development and testing of a gas chromatography - pedestal olfactometer (GC-PO) that produces a Gaussian shaped distribution of one odorant in a background of constant odor composition (the pedestal).

Espresso coffee samples were freshly prepared with 10% sucrose, 0.0143% sucralose (equivalent in sweetness to 10% sucrose), or unsweetened, each with and without nondairy creamer. A sensory panel rated the intensities of “malty,” “caramel,” “roasty,” and “coffee-like.” The concentrations of flavor chemicals associated with the latter three sensations (Furaneol, 2-ethyl-3,5-dimethyl [EDM] pyrazine, and 2-furfuryl thiol, respectively) were determined by gas chromatography, using solid-phase microextraction sampling of coffee headspace. Furaneol and furfuryl thiol were essentially unaffected by creamer addition, but the more nonpolar EDM pyrazine was greatly reduced. The malty, caramel, roasty, and coffee-like flavor intensities were not significantly affected by creamer addition. This appears to be a case of disconnect between the absence of an odorant and perception. Furaneol, furfuryl thiol, and EDM pyrazine concentrations were unaffected by adding either sweetener. The malty sensation was the same with and without added sweetener. The roasty and coffee-like ratings both decreased to similar extents in the samples with the two added sweeteners. The ratings for caramel were considerably increased, again to a similar extent, by both sweeteners. Since the added sweeteners were both nonvolatile, this is clearly a case where taste affected odor perception.

The Hyblean pastures are characterized by a great variety of native forages, and offering opportunity for selective feeding by animals. Over 100 plant species belonging to over 25 families occur, although not all of these may occur in single pasture.1 The occurrence of pasture species and the selective forage behaviour of dairy cattle in very complex pastures was part of a larger study on the influence of diet upon cheese flavour. The plant diversity may contribute to cheese flavour.2 The animals were individually followed on the pasture and the kind of species and plant parts selected were recorded.3 The volatile constituents of the above-ground (aerial) parts of the most commonly occurring and selected plant species in the Hyblean pasture were extracted by steam distillation and analysed by GC–olfactometry (GC–O) and GC–MS. The number of odour-active compounds identified in the plants ranged from 12 in Sinapis to 26 in Erodium. Copyright © 2004 John Wiley & Sons, Ltd.

The application of solid phase microextraction (SPME) to gas chromatography-olfactometry (GC-O) dilution analysis has previously been achieved by varying the thickness of the fibre phase and the length of exposure. In this study, eight steps of dilution by a factor of 2 were achieved by splitting of the injected sample in different ratios in the gas chromatograph's injection port. Using solvent injection and SPME headspace sampling, it was found that the nominal split ratios of the hardware requires calibration to achieve the actual dilutions desired. This calibration method was applied to the CharmAnalysis of coffee as it was brewed.

The fatty acid profile from the retronasal aroma of Cheddar cheese was determined using the retronasal aroma simulator (RAS). Seven odor potent fatty acids identified in Cheddar cheese were placed in model systems and sampled in the RAS. Volatile acids were trapped by solid phase microextraction and identified by GC/MS. The six released fatty acids were added to a model cheese system and subjected to a descriptive analysis sensory test, using omission testing (N-1). Six cheese models, each omitting one fatty acid, were tested in triplicate against a complete model by a trained panel, under a randomized complete block design. Panelists rated the intensity of six descriptors. In one additional test session, the complete model was tested against a model omitting all fatty acids. Results indicated that the omission of propionic acid from the cheese model led to a significant increase (α=0.10) in the ratings for the ‘cream’ descriptor ( P =0.08). The omission of all fatty acids resulted in a significant decrease in the ratings for the ‘sweaty’ descriptor ( P =0.07). Surprisingly, the ratings for the ‘Cheddar’ descriptor did not change under any circumstances. This suggests that although some compounds contribute heavily to the aroma of a food based on their odor potency, the removal of such compounds does not necessarily alter the sensory perception of the overall food concept.

Ragusano cheeses were produced in duplicate from milk collected from pasture-fed and total mixed ration (TMR)-fed cattle at four time intervals. The cheeses were subjected to chemical analysis, conventional sensory testing, and gas chromatography-olfactometry (GCO). Data from each type of analysis were examined by principal component and factor analysis and by pattern recognition (SIMCA) to see if sufficient information for classification into pasture-fed and TMR-fed groups was contained therein. The results clearly indicate that there are significant differences in sensory panel and chemical analysis results between the two cheeses. The data were also examined to see if models of sensory responses as a function of analytical or GCO results or both could be constructed with the modeling technique partial least-squares regression (PLS). Strong PLS models of some sensory responses (green and toasted odor; salt, pungent, bitter, and butyric sensations; and smooth consistency) were obtained.

Bats should benefit from recognition of their roost-mates when colonies form stable social units that persist over time. We used Y-maze experiments and gas chromatography–olfactometry (GC-O) to evaluate whether female big brown bats Eptesicus fuscus (Chiroptera: Vespertilionidae) use chemical cues to distinguish among conspecifics. In dual-choice Y-maze experiments, females chose the scent of another female from their own roost over a conspecific female from a different roost in a majority of trials. Analysis of total body odors using GC-O suggests that individuals from a given colony may share a more common odor signature with roost-mates than with non-roost-mate conspecifics. Using four principle components derived from 15 odor variables, discriminant function analysis correctly assigned most individuals to the correct colony.

The perception of wine aroma is an excellent example of the human ability to experience multiple sensations as a single gestalt, i.e. a configural perception or as a top-down process. For example, the same wine recognized as Riesling could, after some time spent on analysis, yield, “This Riesling has a moderate petrol aroma and a faint lemon smell.” Recent studies of binary mixtures showed that only similar odors cross-adapt while dissimilar odors suppress each other in mixtures, indicating a possible explanation for the suppression of fruity/floral by 2,2,1-trimethyl- dihydronaphthalene (TDN) in Riesling.

Novel methods for testing olfactory and visual interactions were devised. Visual stimuli were the outlines of cherries and a banana; olfactory stimuli were benzaldehyde and isoamyl acetate. Perithreshold detection levels for visual stimuli and olfactory stimuli were calculated. An olfactory task (OF) and visual task (VF) were tested. The OF task required panelists to perform an odor task while viewing an image; the VF task required panelists to perform a visual task while sniffing an odor. No significant changes in detection sensitivity were found in either the OF or VF tasks when either the visual or olfactory stimuli were congruent or incongruent.

The volatile content of the effluent from the retronasal aroma simulator (RAS) was compared with that of human breath using mass spectroscopy (MS-Nose). The ratios of volatile compounds from the RAS were closely related to those from the panelists' breath with the correlation coefficients ranging from 0.97 to 0.99 from model food systems. A greater sensitivity using the RAS was achieved because higher concentrations of volatiles in the MS-Nose were produced from the RAS than from the breath. In analyzing the effects on volatility of RAS parameters including airflow rate, temperature, saliva ratio, and blending speed, airflow rate had the greatest effect. The correlation coefficients for the real food systems studied ranged from 0.83 to 0.99. The RAS gives a good approximation of time-averaged flavor release in the mouth as defined by breath-by-breath measurements.

This review summarizes the outcome of sweet taste chemoreception research over the last 30 years. Since the sweet taste receptor has yet to be isolated and identified, several models have been developed to account for sweetness and to explain how molecules are structured to elicit sweet taste chemoreception. The models proposed are classified as follows: category I: the receptor binding theories AH-B, AH-B-X; AH-B-γ; the multi-attachment theory; the α-helix protein theory; category II: the direct G-protein binding theory. All currently established hypotheses are discussed and their ability to account for the sweetness of a variety of structurally dissimilar compounds critically evaluated. After 30 years, the AH-B theory still appears to be the best explanation for the ligand binding chemistry that induces sweet taste response, and it is also consistent with prevailing sweet taste transduction hypotheses.

SUMMARY —The conversion of glutamine to the bitter compound, 2-pyrrolidone-5-carboxylic acid (PCA), in table beets was studied. Glutamine was analyzed by a phosphate-buffer hydrolysis and distillation method. PCA was extracted with ethyl acetate and the ditrimethylsilyl derivative prepared and measured quantitatively by gas-liquid chromatography. The accumulation of glutamine in fresh beets with excessive amounts of nitrogen fertilization caused a substantial increase in PCA content of processed beets. Conversion of glutamine to PCA in beets was proportional to the heating time during processing. Glutamine content did not alter during raw beet storage periods at 35°F; PCA content increased gradually.

Volatile compounds from lychee (Litchi chinesis Sonn.), a tropical fruit native to China, were extracted using both Freon 113 and ethyl acetate solvents. The odor-active compounds present in the fr...

Analysis of the aroma of dairy products is a complex problem due to the heterogeneous nature of milk. Several analytical methods have been used to study the aroma of dairy products; gas chromatography–mass spectrometry (GC/MS) and gas chromatography– olfactometry (GC/O) are most commonly used. In order to identify the individual odor-active compounds a bioassay that is representative of the pattern of odorants in terms of their smell activity is advantageous. Identification of these compounds is carried out using extraction, distillation, concentration and chromatography. This paper reviews the GC/O work on dairy products to date. Common odor-active compounds were found in various types of dairy products analyzed. Seven common odorants were found in four different types of raw milk: dimethylsulfone, ethyl butanoate, ethyl hexanoate, heptanal, indole, nonanal, and 1-octen-3-ol. The effect of heating cows milk changed the aroma profile of the milk, resulting in the formation of four common odor-potent compounds: hexanal, 2-nonanone, benzothiazole, and δ -decalactone. Five fermented dairy products have been analyzed by GC/O. Fermentation resulted in the formation of common odorants: 1-octen-3-one, methional, 3-methylbutanal, and butyric acid. The flavor chemistry of dairy products has been successfully analyzed using GC/O. However, further work must be conducted to produce a sample that reflects the retronasal composition of the product. This requires the use of a retronasal aroma simulation (RAS) device and/or gas chromatography olfactometry headspace (GCO-H).

GC combined with olfactometry can be used to study the human olfactory process and to quantify the sensory activity of chemicals

A flavor release method using a “retronasal aroma simulator” (RAS) combined with gas chromatography olfactometry (GCO) was used to study the aroma of raspberries, Rubus idaeus cv. Heritage. Dynamic headspace samples were generated with the RAS including synthetic saliva addition and shearing at 37 °C. A headspace dilution series was sampled from the RAS and analyzed by CharmAnalysis GCO to produce measures of odor potency called charm. The most potent flavor compounds in fresh raspberries were β-damascenone, diacetyl, sotolon, 1-hexen-3-one, 1-nonen-3-one, 1-octen-3-one, and (Z)-3-hexenal. Heating raspberries caused an increase in raspberry ketone and rated raspberry aroma. Likewise, β-damascenone, sotolon, vanillin, 1-nonen-3-one, and 1-octen-3-one showed at least 5-fold increases in charm upon heating. Cream addition markedly decreased aroma (GCO and sensory). Comparison of the fresh raspberries odor spectra between RAS−GCO and solvent extraction−GCO showed different profiles, with the former having gre...

A device that simulated retronasal aroma was constructed from a 1 L blender incorporating purge-and-trap, synthetic saliva addition, temperature regulation to 37 °C, and blending at shear rates reported to occur during eating. Volatiles were collected on a silica trap, solvent desorbed, and quantitated by GC/FID or GC/MS with high precision (CV < 5%) and sensitivity (micrograms per liter). Increasing the temperature from 23 to 37 °C and adding shear increased volatility. The addition of synthetic saliva to a model grape beverage (pH 2.6) increased the pH and the volatility of the bases, 2-acetylpyridine, methyl anthranilate, o-aminoacetophenone, and 2-methoxy-3-methylpyrazine, relative to a model neutral compound, 1,8-cineole. The data were consistent with a sensory test that showed a significant shift in the perception of minty to nutty upon the addition of synthetic saliva to a mixture of 1,8-cineole and 2-acetylpyridine in an acid medium. The volatility of eight flavor compounds was investigated in a soybean oil versus water matrix. The volatilities of α-pinene (log P = 3.75), ethyl 2-methylbutyrate, 1,8-cineole, 2-methoxy-3-methylpyrazine, and methyl anthranilate decreased by factors of 8000, 130, 100, 7, and 3 upon oil addition ; however, butyric acid did not decrease, and polar maltol (log P = 0.02) actually increased.

Diacetyl, an important wine flavorant synthesized during alcoholic and malolactic fermentation, has been reported to have a sensory threshold of 2–3 mg/l. A comparative study of threshold for diacetyl in wines was undertaken to determine the effect of wine type on that value. Sensory threshold was determined according to the forced-choice ascending concentration series of limits method described by ASTM (E 679-79), using trained panelists. Panel detection thresholds and standard deviation from the geometric mean were found to be 0.2 mg/l and 0.32 in Chardonnay, 0.9 mg/l and 0.21 in Pinot noir, and 2.8 mg/l and 0.38 in Cabernet Sauvignon. These results demonstrate the important effect of wine type on diacetyl threshold, invalidating the use of a single threshold value for all wines.

β-Damascenone, a potent aroma compound in a variety of natural products, is primarily liberated from precursors. Isolation of β-damascenone precursors from apples Malus domestica Borkh. cv. Empire, using Amberlite XAD-2 adsorption and C 18 flash chromatography columns followed by C 18 HPLC, yielded at least eight separate precursors, of which the most abundant was further purified and characterized. Mass spectra from ion spray tandem MS, GC/MS of TMS sugars, and GC/MS of the enzymatically released aglycon indicated a structure of 9(or)-α-L-arabinofuranosyl-(1,6)-β-D-glucopyranoside of the acetylenic diol

Thermal processing of synthetic polymers in the presence of oxygen into food-packaging materials can result in the formation of by products which impart off-odors or raise toxicological questions. Volatiles from the thermal oxidation of polyethylene were collected and anlyzed by gas chromatography/olfactometry (GCO; CharmAnalysis). Fourteen odor-active compounds, most of which occurred in amounts that were too low to be detected instrumentally, were present. Overallodor was waxlike but individual components were fruity, herbaceous, rancid, metallic, way, pungent, or orange

Changes in orange juice composition in a model system simulating Brik-Pak aseptic packaging composed of two polymers, LDPE and Surlyn, were measured. GC-FID was used to measure the amount of d-limonene in the juice, while gas chromatography-olfactometry (GCO) was used to measure the odoractive volatiles in orange juice. More than 70% of the limonene was absorbed by the polymers in 24 h at 25 o C. However, results from the GCO analysis indicated that limonene had only trace odor activity. Furthermore, the plastic polymers tested did not substantially alter the odor-active components detected in orange juice

Gas chromatography/olfactometry (GC/O) based on dilution analysis (e. g., CharmAnalysis or aroma extraction dilution analysis) gives an indication of what compounds are most important (most potent) to the aroma of foods. The application of solid phase microextraction to the preparation of samples for GC/O dilution analysis was shown to be feasible by varying the fiber thickness and length to achieve various absorbant volumes.

The effect of controlled atmosphere (CA) storage on the production of 22 odor-active volatiles in ‘McIntosh’ and ‘Cortland’ apples was studied. Volatiles were analyzed periodically during ripening in air after harvest, during refrigerated air and CA storage, and during ripening in air after CA storage. Production of most volatiles at a lower rate during ripening after CA storage than during ripening immediately after harvest cannot be attributed entirely to the action of CA. Under the conditions of this study (3% O2+ 3% CO2+ 94% N2 at 0°C for 19 weeks) CA storage caused a “residual suppression” effect on the production of propyl butanoate, butyl hexanoate, and hexyl hexanoate. Results indicate that CA might have altered the normal metabolism of the fruit by blocking the normal production of some volatiles either temporarily or permanently and either partially or completely.

Cachaca, the most popular alcoholic beverage in Brazil, is a sugar cane spirit similar to rum. Its production is around 2 billion liters per year, of which

Applications of flavour chemistry rely on the idea that people perceive flavour similarly. Odorant-specific sensory deficits (OSDs) are a severe challenge to this notion, and their effects on flavour are not fully understood. OSDs have been studied since Amoore's formative work on specific anosmia [1]. These differences in odorant thresholds for individuals with an otherwise functioning sense of smell can be divided into two categories: stable and variable OSDs. Stable OSDs are likely due to genetically determined components of the transduction system, while variable OSDs are consistent with changes in either peripheral expression or central processing. Variable OSDs are characterised by a subjects' increase in sensitivity to some compounds with time or exposure. This is a well documented phenomenon in humans and other mammals that makes it difficult to measure stable OSDs at a single time [2–5]. The use of gas chromatography-olfactometry (GCO) to investigate the phenomenon of variable OSDs will be discussed.

Taste threshold tests of ferrous sulfate (FeSO4) solutions have been confounded by the presence of putative odorants. To detect the presence of odorants released from these solutions solid-phase microextraction (SPME) was used to collect volatiles in the headspace above FeSO4 solutions. Gas chromatography-olfactometry of samples collected over three time periods (1, 5, and 16 h) and at two temperatures (22 and 37 degrees C) revealed the presence of several metallic-smelling odorants in the headspace. Using authentic standards, two of the odorants were conclusively identified as 1-octen-3-one and 1-nonen-3-one. Trace levels of other odorants were also detected, but dilution experiments indicated that 1-nonen-3-one was at least 10 times more potent than anything else released from the solutions. 1-Octen-3-one and 1-nonen-3-one are excellent candidates for the metallic odor responses often observed in threshold testing of solutions of FeSO4.