0000000000012276
AUTHOR
J. L. Le Quere
Heat treatment of vegetable oils. II. GC-MS and GC-FTIR spectra of some isolated cyclic fatty acid monomers
Gas liquid chromatography coupled with mass spectrometry (GC-MS) showed that the cyclic fatty acid monomers (CFAM) isolated from a heated linseed oil have two ethylenic bonds, while the CFAM isolated from heated sunflower oils were saturated and monoethylenic isomers. GC-MS studies also showed the presence of cyclohexenic derivatives in the case of linseed oil.
Interactions between non-volatile water-soluble molecules and aroma compounds in Camembert cheese
Abstract Interactions between selected aroma compounds and non-volatile water-soluble molecules were studied using dynamic headspace-gas chromatography. A model water-soluble extract (MWSE), previously constructed in gustatory and physico-chemical accordance with the crude Camembert cheese WSE, allowed the contribution of non-volatiles to the headspace composition of volatile compounds to be assessed. The presence of the MWSE increased the headspace concentration of 2-heptanone, 1-octen-3-ol and 3-methylbutanol, showing that these three volatile compounds were released by MWSE. Omission tests performed on MWSE allowed for the impact of each MWSE component on aroma compounds release to be de…
Taste active compounds in a goat cheese water-soluble extract 1. Development and sensory validation of a model water-soluble extract
The aim of this study was to evaluate the impact of the components of a goat cheese water-soluble extract (WSE) on its flavor by both physicochemical and sensory techniques with special emphasis on taste. After characterization of the organoleptic properties of the cheese, the WSE was extracted with pure water and submitted to successive tangential ultrafiltrations and nanofiltration. The physicochemical assessment of these fractions led to the constitution of a model mixture (MWSE) compared by sensory evaluation to the crude WSE, using a panel of 16 trained members. The results of both sensory profile and triangular tests indicate no significant difference, therefore proving that the recon…
Evolution of the taste of a bitter camembert cheese during ripening : characterization of a matrix effect
The objective of this study was to characterize the effect of ripening on the taste of a typically bitter Camembert cheese. The first step was to select a typically bitter cheese among several products obtained by different processes supposed to enhance this taste defect. Second, the evolution of cheese taste during ripening was characterized from a sensory point of view. Finally, the relative impact of fat, proteins, and water-soluble molecules on cheese taste was determined by using omission tests performed on a reconstituted cheese. These omission tests showed that cheese taste resulted mainly from the gustatory properties of water-soluble molecules but was modulated by a matrix effect d…
Tergal glands of male and femaleCryptocercus punctulatus scudder (Dictyoptera: Cryptocercidae): Composition, sexual dimorphism, and geographic variation of secretion
International audience; Males and females of Cryptocercus punctulatus possess tergal glands, but they differ in position, size, morphology, and secretion chemistry. Compound A (linalyl acetate) is the most abundant of the 21 compounds found only in the secretion of these glands. Compound B, 4,6,8-trimethyl-7,9-undecadien-5-ol, is specific to the tergal secretion of females.C. punctulatus lives only in the United States; its distribution is disjunct. Compound A is found in samples from the eastern population but is absent in samples from the western population. The amount of compound B per gland in samples from the western population is at least twice as high as in the samples from the easte…
2-methylthiazolidine and 4-ethylguaiacol, male sex pheromone components of the cockroach Nauphoeta cinerea (Dictyoptera, Bladeridae) : A reinvestigation
49 ref.; International audience; In Nauphoeta cinerea, male calling behavior is associated with sex pheromone release by the sternal glands. The male pheromone that attracts females from a distance is a mixture of 2-methylthiazolidine and 4-ethylguaiacol. It is active at very low concentrations, 0.05 and 0.01 ng, respectively. Two other compounds, 3-hydroxy-2-butanone and 2-methyl-2thiazoline, act at close range, keeping the female in the vicinity of the male. The function of the volatile pheromone and those of previously described contact pheromones are discussed in regard to their possible involvement in the establishment of male dominant-subordinate relationships.
A novel prototype to closely mimic mastication for in vitro dynamic measurements of flavour release
International audience; Flavour release during eating of a food depends upon many parameters that can hardly be managed. In-vivo measurements by the APCI MS-nose method allowed temporal sensory evaluation and flavour release data to be directly correlated, but several limitations have frequently been reported. These were: high inter-individual variability, low repeatability of measurements, and weak experiment throughput due to panellists' exhaustion. To overcome most of these limitations, the use of an artificial mouth for online mesurement of flavour release is recommended. However, the systems used in previous reports were limited in terms of reproducing in-vivo oral functions and parame…
Isolation and identification of 4,6,8-trimethyl-7,9-undecadien-5-ol, a female-specific compound, in tergal gland secretion ofCryptocercus punctulatus scudder (Dictyoptera: Cryptocercidae)
International audience; The secretion of the tergal glands of Cryptocercus punctulatus consists of a complex mixture of 27 compounds. Of this mixture, only one compound (compound B) is specific for females. By dissecting 200 tergal glands, 50 µg of pure compound B was collected by preparative GC; it was identified as (Z, E-4,6,8-trimethyl-7,9-undecadien-5-oI. Its functions as well as its absolute configuration still have to be determined.
Identification and sensory evaluation of the character-impact compounds of goat cheese flavour
1 SUMMARY The volatile compounds of various goat cheeses have been isolated in order to identify the character-impact odorants by a combination of instrumental analyses and sensory studies. Different extraction procedures have been studied in order to obtain a volatile fraction representative of the cheeses. The most representative extract, as determined by sensory evaluation, has been submitted to GC-MS and to GC-olfactometry, using the aroma extract dilution analysis (AEDA) method. The volatile fatty acids have been found to be the most important compounds for the characteristic goat flavour. Among them, branched-chain fatty acids ( e.g. , 4-methyloctanoic and 4-ethyloctanoic) have been f…
Metabolism of L-phenylalanine in the lignin-degrading white-rot fungi Bjerkandera adusta and Ischnoderma benzoinum
International audience
Calling behaviour of female Periplaneta americana: Behavioural analysis and identification of the pheromone source
Abstract The site for the production of Periplanone B, one of the components of the female sex pheromone of Periplaneta americana , was localized in glands situated in the genital atrium, and we have called these structures atrial glands. While emitting the sex pheromone, females adopt a characteristic calling posture during which time the atrial glands are exposed. Behavioural assays of males utilizing pentane extracts of various female body parts revealed that atrial gland extracts are highly attractive, and induced more wing-raising behaviour, than any other female body part. GC-MS analyses support these results by revealing that Periplanone B is only present in the atrial glands. We est…
Production of a cheese model for sensory evaluation of flavour compounds
Summary - A cheese model used to perform sensory evaluation of flavour compounds extracted from various cheese varieties was made with caseins, low heat milk powder, deodorized milk fat, NaCI and renne!. Its composition and physicochemical properties were close to mature hard cheese, apart from a lower dry matter content and sodium concentration, and a higher lactose concentration. Its preparation was established in arder to avoid drainage for at least 24 h, which should allow the incorporation of not only sorne lipophilic substances such as aromas but also some water-soluble substances such as amino acids and peptides. The rheological behaviour of the cheese model measured by a compression…
Taste active compounds in a goat cheese water-soluble extract 2. Determination of the relative impact of water-soluble extract components on its taste using omission tests
The aim of this work was to determine the relative impact of water-soluble compounds on the gustatory properties of a goat cheese water-soluble extract (WSE). Using a semisynthetic model mixture (MWSE) previously elaborated in physicochemical and gustatory accordance with the cheese WSE (see part 1, Engel et al. J. Agric. Food Chem. 2000, 48, 4252-4259), omission tests were performed. Among the main taste characteristics of the WSE (salty, sour, and bitter), saltiness was explained by an additive contribution of sodium, potassium, calcium, and magnesium cations, whereas sourness was mainly due to a synergistic effect involving sodium chloride, phosphates, and lactic acid and bitterness was …
Role of sodium nitrite on phospholipid composition of cooked cured ham. Relation to its flavor
Abstract The role of sodium nitrite on phospholipid composition was studied during the processing of cooked cured ham. Evolution of the different classes of phospholipids in raw meat, cured meat with brine injected at 0, 50 and 100 mg of sodium nitrite/kg meat, and cooked meat, was determined as well as fatty acid content of phosphatidyl choline and phosphatidyl ethanolamine in raw and cooked meat. The major effect of sodium nitrite was observed on phosphatidyl ethanolamine whose content was significantly lowered in the presence of this salt. This effect was observed at the end of the curing process and was not modified by the cooking. The fatty acid content between raw meat and cooked cure…
An original approach for gas chromatography-olfactometry detection frequency analysis: Application to gin
Abstract Gas Chromatography-Olfactometry (GC-O) is a technique that lies halfway between physicochemical and sensory analysis and involves the perception of volatile flavour compounds, separated by gas chromatography, by the human nose. Of the different GC-O procedures available, detection frequency has been proved to be more rapid and more repeatable, even with an untrained panel. This characteristic regarding the panel is often not considered when dealing with the sensory attributes determined by assessors. An original approach to GC-O using the detection frequency procedure has been developed and tested on two types of gin and made it possible to benefit from sensory data. The panel cons…
Chemistry of defensive secretions in nymphs and adults of fire bug , Pyrrhocoris apterus L.(Heteroptera, Pyrrhocoridae)
International audience; The defensive secretions from the nymphs and the adults of both sexes in P. apterus were chemically investigated. Forty components were identified from the nymphal posterior dorsoabdominal glands and 35 from the adult metathoracic glands of both sexes. Within the 43 identified chemicals, we found 23 aldehydes, five saturated hydrocarbons, five alcohols, three ketones, three lactones, two terpenes, one phenol and one ester. Thirteen of these compounds had never been reported within the Heteroptera. Whereas eight components are specific to the nymphs, methyl pentenal, (E)-2-hexenol, and heptadecanal are the only adult-specific components. The biological role of all the…
Isolation of a peptidic fraction from the goat cheese water-soluble extract by nanofiltration for sensory evaluation studies
Abstract The effect of the small water-soluble peptides on the taste of cheeses has not been clarified yet because of the high difficulties to isolate them from the other water-soluble compounds. A new filtration method, nanofiltration, using ionizable membranes, allowed us to purify a peptidic fraction prepared from the permeate obtained by ultrafiltration (MWCO=1000) of a goat cheese water-soluble extract. A large proportion of mineral salts and a part of amino acids were eliminated from the nanofiltration retentate where a majority of small peptides were concentrated. The peptidic fraction was incorporated in a cheese model with known synergistic effectors such as mineral salts and amino…
(3Z,6Z,8E)-3,6,8-dodecatrien-1-ol : Sex pheromone in a higher fungus-growing termite, Pseudacanthotermes spiniger (Isoptera, Macrotermitinae)
International audience; The female sex pheromone of the fungus-growing termitePseudacanthotermes spiniger (Termitidae, Macrotermitinae) was isolated from sternal glands of alates. The compound inducing attraction and excitation in males was identified as the (3Z,6Z,8E)-3,6,8-dodecatrien-1-ol by GC-MS, microhydrogenation, GC-FTIR, and NMR. This unsaturated alcohol is present in both sexes but in much higher quantities in females than in males (about 10 times). The hypothesis is suggested that this alcohol, which is detected at extremely low concentrations by the workers ofP. spiniger, may be used either as a trail-following pheromone or a sex pheromone according to concentrations and to targ…
Identification of tasty compounds of cooked cured ham : physico-chemical and sensory approaches
Abstract Tasty compounds from meat have not been studied in depth. The aim of this work was to isolate, identify and quantify tasty compounds from cooked cured ham and to link them to the sensory evaluations of the fractions from which they are extracted. The extraction of the water-soluble fraction from ham was done by an hydraulic press. The crude extract was ultrafiltered and both gel filtration and nanofiltration allowed to obtain edible fractions. Some links between the physicochemical and sensory data have been found, in particular, the umami taste was related to the presence of IMP and monosodium glutamate. The direct influence of proteolytic peptides on this taste is discussed. More…
Use of omission tests to evaluate taste-active compounds in food : application to cheese and tomato
International audience
Evaluation of taste compounds in water-soluble extract of goat cheeses
Abstract The water-soluble fractions of two goat cheeses — one denomination of origin commercial trade mark (crottin de Chavignol®) and one bought in a local cheese making establishment (Bouton de culotte®) — containing many taste and flavour molecules were studied. Ultrafiltration with a 1000 Da threshold membrane, followed by gel filtration on Toyopearl HW-40S gel using water as eluent, led to the production of edible fractions. Physicochemical and sensory analysis of these fractions showed that the most tasty fractions contained, essentially, the free amino acids and mineral salts. Some of these tasty fractions also imparted some flavours. The quantity of small peptides (MW
Volatile components of dry-cured ham
The volatile components of dry-cured ham were isolated by vacuum distillation and analyzed by gas chromatography-mass spectrometry. The structures of 76 molecules were identified by mass spectrometry, cochromatography, or measured Kovats indices. The compounds identified may come from the catabolism of the main constituent parts of the meat (glucids, lipids and protids) during the curing of the hams, from the pig feed, or from technological processes. The volatile compounds extracted from 50 g of ham according to the technique described correspond to a chromatographical surface equivalent to 0.12 mg of the dodecane internal standard, or approximately 2.4 ppm of the weight of the sample. Fla…
Isolation of oligopeptides from the water-soluble extract of goat cheese and their identification by mass spectrometry
A procedure for the separation and identification of small peptides from the water-soluble fraction of a goat cheese was developed. The water-soluble extract was ultrafiltered (1000 Da membrane cutoff), and peptides were isolated by sequential chromatography: size exclusion chromatography (HPLC-grade water), anion exchange chromatography (phosphate buffer gradient), and semipreparative reverse-phase high-performance liquid chromatography (water/acetonitrile gradient). The fractions obtained were analyzed by combined mass spectrometry methods including electrospray ionization, liquid secondary ionization, and tandem mass spectrometry to identify and to confirm the sequences of 28 tri- to oct…
Gas chromatography-fourier transform infrared spectrometry of fatty acids: New Applications with a direct deposition interface
Infrared spectroscopy is a suitable spectroscopic method to differentiate geometric Z and E isomers of unsaturated compounds. A direct-deposition Fourier transform infrared spectrometer (FTIR), coupled to a gas chromatograph, was used successfully to analyze with a high sensitivity traces of C18:1 fatty acid methyl ester (FAME) isomers. It could also conclusively distinguish between isomers of conjugated diunsaturated FAME. The achievable sensitivity of this direct-deposition device makes possible accurate FAME mixture analyses that are not currently attainable with the more conventional light-pipe interface.
Interactions between volatiles and lipids in complex systems
Partition equilibria of three aroma compounds in three different biphasic systems were studied by a liquid/liquid partition technique to investigate interactions that occur between volatiles and lipids in biphasic solutions. The lipids used were linoleic acid and ricinoleic acid and tetradecane as a model. The three aroma compounds were ethyl acetate, 2,5-dimethylpyrazine, and oct-1-en-3-ol. The results showed that the intermolecular forces involved were weak. Infrared spectroscopy was then performed on binary systems (tetradecane and linoleic acid or aroma compound) and on ternary systems (tetradecane, linoleic acid, and aroma compound) to determine the nature of the interactions. This met…
Chemistry of pheromonal and defensive secretions in the nymphs and the adults ofDysdercus cingulatus Fabr. (Heteroptera, Pyrrhocoridae)
59 ref.; International audience; The exocrine secretions from the nymphs and the adults of both sexes in D. cingulatus were chemically investigated. Seven compounds were identified in the anterior glands, and eleven in the median dorsoabdominal glands of nymphs and adults of both sexes. Fifty-five compounds were identified in the defensive glands (34 in posterior dorsoabdominal glands ofnymphs and 21 in metathoracic glands of adults), and six in the sternal glandular epithelium of the males. The biological function of the glandular secretions and of their identified compounds were investigated and are discussed.
Inactivation of lactococcal aromatic aminotransferase prevents the formation of flora aroma compounds from aromatic amino acids in semi-hard cheese
The enzymatic conversion of aromatic amino acids to aroma compounds plays a role in the formation of an undesirable floral aroma in Cheddar-like cheeses. In lactococci, the first step of aromatic amino acid degradation is a transamination, catalysed by an aromatic aminotransferase (AraT). We observed previously that in vitro, araT inactivation prevented degradation of aromatic amino acids and decreased degradation of Met and Leu. In this study we evaluated the effect of araT inactivation in Lactococcus lactis on flavour development in St. Paulin-type cheese. The degradation of amino acids was monitored by using radiolabelled amino acids and the volatile compounds formed were analysed by GC-…
Production of halogenated compounds by Bjerkandera adusta.
International audience; The white-rot fungusBjerkandera adusta produces volatile chlorinated phenyl compounds. The main compounds identified were 3-chloro-4-methoxybenzaldehyde (3-chloro-p-anisaldehyde), 3-chloro-4-methoxybenzyl alcohol (3-chloro-p-anisyl alcohol), 3,5-dichloro-4-methoxybenzaldehyde (3,5-dichloro-p-anisaldehyde), and 3,5-dichloro, 4-methoxybenzyl alcohol (3,5-dichloro-p-anisyl alcohol).p-Anisaldehyde, veratraldehyde and the corresponding alcohols,p-anisyl alcohol and veratryl alcohol were produced simultaneously. Even with a very low concentration of chloride in the medium (<>–5 m), chlorinated aromatic compounds were still observed. Addition of bromide to the culture mediu…