Global Odor Research Articles

Characterisation of volatile compounds in Tunisian fenugreek seeds

Abstract In this study, we intend to develop a simple and fast analytical procedure to identify the volatile compounds implicated in the odour of Tunisian fenugreek (Trigonella foenum-graceum L.) seeds. Two procedures, solvent extraction and static headspace solid-phase microextraction (SHS-SPME), have been used under different conditions. The volatile compounds extracted were systematically identified using gas chromatography–mass spectrometry, based on their mass spectrum and Kovats index on two columns of different polarity. A total of 67 compounds were identified, some of them being reported for the first time in fenugreek seeds (e.g. several pyrazines, 2,5-dimethyl-4-hydroxy-3(2H)-furanone or 1-epi-cubenol). Methanol was found to be the preferred solvent for high and medium boiling point volatile compounds, such as sotolone and nitrogen compounds. For SHS-SPME, the fibre coated with divinylbenzene/carboxen/polydimethylsiloxane 2 cm was the most suitable for extracting volatile compounds from ground seeds. The efficiency of this fibre was confirmed by direct gas chromatography–olfactometry, with a global odour similar to that of fenugreek seeds.

Screening of the odour-activity and bioactivity of the essential oils of leaves and flowers of Hyptis Passerina Mart. from the Brazilian Cerrado

The chemical profile of the essential oils obtained from the leaves and flowers of Hyptis passerina Mart., a rare species of the Brazilian Cerrado, has been determined for the first time. Analyses by GC-MS showed sesquiterpenes as major compounds. β-epi-acorenol (35.7% and 32.8%, respectively from leaf and flower essential oils), was isolated and identified by 1D and 2D NMR. The flower-derived oil presented a higher concentration of hydrocarbon and oxygenated monoterpenes, while the leaf-oil was richer in diterpenes. The global odour impressions of both oils were given by direct analysis and GC-MS-O and were characterized as herbaceous with tea notes, and green, cooked and woody impressions for leaf-oil; herbaceous, with spicy, woody and minty notes for flower-oil. β-epi-acorenol, spathulenol, β-caryophyllene, and caryophyllene oxide were relevant for the odour-activity of both oils, as well as minor constituents, such as linalool. The antimicrobial activity was investigated by means of agar diffusion disc method and contact bioautography, against Gram-positive and negative bacteria and yeast. Both oils presented to be bioactive against the tested microorganisms with significant inhibition level.

The significance of low impact odorants in global odour perception

Low impact odorants are generally considered unimportant in aroma perception; however, recent evidence establishes the significance of these compounds in global odour perception. We hypothesise that the perception of high impact odorants is modified by sub- and peri-threshold odorants, even those with low odour activity. In order to fully evaluate the importance of low impact odorants, and better understand the complexities of global odour perception, a new multidisciplinary approach is needed incorporating chemical, sensory and neurological model studies.

The effect of cysteine on production of volatile sulphur compounds by cheese-ripening bacteria

The effect of cysteine on the ability of smear cheese-ripening bacteria ( Brevibacterium linens and Arthrobacter spp) to produce volatile sulphur compounds (VSC) from methionine was studied. These bacteria were cultivated in a synthetic medium supplemented with various cysteine concentrations with or without methionine. Cultures with only cysteine showed slightly lower levels of VSC produced and an unpleasant odour like rotten eggs, resulting from hydrogen sulphide production. The levels and profiles of VSC produced with supplemented methionine–cysteine mixtures had strain-dependant behaviours. However, the highest levels of dimethyl disulfide, dimethyl trisulfide and dimethyl tetrasulfide were observed when increasing the cysteine concentration from 0.2 to 1.0 gl − 1 at the same methionine concentration (1.0 gl − 1 ). In contrast, production levels of thioesters, especially S-methylthio acetate, were reduced by 50 and 80% under such conditions. An initial sensory approach showed that such an effect could have a strong impact on the global odour of ripened cheeses.

Complementary approaches to measure environmental odours emitted by landfill areas

This paper presents different methods to assess the odour emission and the odour annoyance in the surroundings. It is shown, on the example of landfill areas and composting facilities, that chemical analyses are helpful to identify key compounds of the odour release, and to set up the specification of a monitoring instrument. Sensitive methods, like dynamic olfactometry or sniffing team investigation, are mainly applicable to provide a global odour plume or an average annoyance zone. And the electronic nose can supply a warning signal to the plant manager or a real time estimation of the annoyance zone.

A new approach to studying sponge cake aroma after storage in treated paper and plastic packaging by direct gas chromatography–olfactometry (D‐GC–O)

AbstractThe objective of this study was to use D‐GC–O to compare the global odour of a sponge cake flavoured with either a ‘viennoiserie’ aromatic note or a simplified mixture of aroma compounds (used for physicochemical studies), then stored in a glass packaging (inert and impermeable) or in pouches made with treated papers or with plastic packaging, in accelerated ageing conditions (high temperature and relative humidity gradient). After 1 week of storage, the flavoured sponge cake headspace was SPME‐extracted directly into the packaging and analysed by D‐GC–O. The sponge cake global odour was better retained if plastic film rather than treated‐papers was used, for both flavourings. Changes in the relative proportions of aroma compounds in the sponge cake during storage modified the perceived global odour. This was due to their modified retention in the sponge cake and to their transfer through the packaging. SPME coupled to D‐GC–O was confirmed to be a rapid and sensitive method for comparing the aroma compound barrier properties of various packaging films with flavouring mixtures at concentrations close to reality. Copyright © 2007 John Wiley & Sons, Ltd.

New gas chromatography–olfactometric investigative method, and its application to cooked Silurus glanis (European catfish) odor characterization

A new gas chromatography–olfactometric method, gas chromatography–global olfactometry omission detection (GC–GOOD), was applied to dynamic headspace odor extracts of Silurus glanis (European catfish). The GC–GOOD method is based on the omission test theory and uses a gas chromatograph coupled with a three-way valve and an a flame ionization detector. The GC–GOOD method enabled the identification of key families of volatile compounds in the S. glanis global odor and the elucidation of the interactions occurring between these families. Significant main effects were observed for the families of volatile compounds exhibiting cooked odor, grassy odor and alcohol, solvent and plastic odors. Omission of these families involved a loss of odor similarity.

New gas chromatography–olfactometric investigative method, and its application to cooked Silurus glanis (European catfish) odor characterization

A new gas chromatography–olfactometric method, gas chromatography–global olfactometry omission detection (GC–GOOD), was applied to dynamic headspace odor extracts of Silurus glanis (European catfish). The GC–GOOD method is based on the omission test theory and uses a gas chromatograph coupled with a three-way valve and an a flame ionization detector. The GC–GOOD method enabled the identification of key families of volatile compounds in the S. glanis global odor and the elucidation of the interactions occurring between these families. Significant main effects were observed for the families of volatile compounds exhibiting cooked odor, grassy odor and alcohol, solvent and plastic odors. Omission of these families involved a loss of odor similarity.

Optimization of Extraction of Apple Aroma by Dynamic Headspace and Influence of Saliva on Extraction of Volatiles

The dynamic headspace procedure of aroma extraction was optimized on Gala apples (Malus domestica). Two parameters affecting the extractability of compounds were studied: temperature and purge time. The influence of artificial saliva was also included. An increase in purge time and temperature caused an increase in the extraction of volatiles from the apple matrix. The optimum point of extraction was 40 degrees C and 70 min of purge. The study also showed that the addition of saliva influenced the extraction of volatile compounds, but this effect was different from one compound to another. To verify that the headspace extracts presented a global odor representativeness of fresh apple under these conditions of extraction, eight assessors compared the odor of extracts with fresh fruit odor for three different cultivars. With regard to the sensory profiles of extracts, the optimal conditions of extraction were suitable for extraction of volatile compounds, even if cooked apple odor appeared in some extracts. The similarity marks of extracts were low but acceptable.

Breed type and ageing time effects on sensory characteristics of beef strip loin steaks

Forty-two yearling males from seven European beef breeds were used to study breed type and ageing time effects on meat sensory quality. Breeds were grouped according to their double muscled condition (DM), dual-purpose condition (Brown Swiss, BS), fast growth rate (FG) and rustic characteristics (RT). Vacuum packaged loin chops were aged for 1, 3, 7, 10, 14 and 21 days at 4°C and evaluated by a trained taste panel. Ageing time had the main influence in all the studied sensorial descriptors. Breed type did not affect juiciness, fibrosity or overall flavour intensity. Interactions between breed type and ageing appeared in global odour intensity, tenderness ( p<0.05) and acid flavour intensity ( p<0.01). All breed types showed higher tenderness scores as ageing period increased but, comparatively, those with higher scores at an early postmortem period (DM, FG) showed lower scores at a late postmortem time. A possible faster, but shorter and less intensive meat tenderisation rate in animals with double muscled condition, and its particular collagen characteristics, in relation to BS and RT groups, could explain our findings.

Characterization of Malodorous Volatiles in Air Using Olfactometry and Computer Assisted Capillary-Gas Chromatography-Mass Spectrometry

Abstract Characterization of malodorous organic volatiles, arising from animal breeding stations and from the coke and steel industry was performed by means of dynamic headspace enrichment (active charcoal-CS2 method) followed by capillary gas chromatography with olfactive and/or mass spectrometry detection. The results were associated to olfactive threshold values from the literature in order to present circular odour charts reflecting both the quality and the intensity of the odour sample. These charts, by visually indicating the respective contributions of specific chemical classes to the global odour, could help to elaborate the abatement techniques.