Search

International audience; Ichang lemon is a citrus fruit whose rind gives off a delicious and much appreciated fragrance and flavor. The volatile components of the fruit peel of Ichang lemon were investigated by GC-MS and GC-O (AEDA method). Simultaneously, its genetic origin was identified by using diagnostic SNP markers specific to ancestral species and multiallelic SSR and InDel markers. Ichang lemon combines three ancestral genomes (Citrus maxima, Citrus ichangensis, and Citrus reticulata) and may be a pummelo x Yuzu hybrid. Although the major compounds of the Ichang lemon aromatic profile were present in Citrus junos, a few pummelo-specific compounds were also detected, such as indole and nootkatone, in agreement with its maternal lineage. 3-Methyl-3-sulfanylbutyl acetate, reported to occur in passion fruit and brewed coffee, was identified by GC-MS, GC-QTOF-MS, and GC-FTIR for the first time in citrus. This odor-active compound has a sulfurous, tropical fruity, green note.

Citrus juices can be cold-concentrated by crossflow microfiltration (CMF) in order to obtain functional foods enriched in carotenoids, flavonoids and pectins. The work aimed to characterize the organoleptic quality of this type of micronutrient-dense foods through their aroma profile and sensory analysis. Two citrus concentrates with and without a diafiltration step were compared.Both citrus products were very different, linked to aroma compound, sugar and organic acid contents. Due to its sugar/acidity balance and its better aromatic profile responsible for the citrus-floral flavour, the concentrate without diafiltration was preferred by the sensory panel. Thanks to a simple transfer model, we showed that retention of volatiles clearly varied from one aroma compound to another. The terpene hydrocarbons were the most retained by the membrane during CMF, probably because they were strongly associated with insoluble solids by adsorption.Even though the process modified their organoleptic profiles, both citrus-based products were well rated and can be consumed directly as pleasant functional drinks. © 2022 Society of Chemical Industry.

Semiochemicals such as herbivore-induced plant volatiles (HIPVs) and host chemicals serve as communication signals for parasitoids searching for oviposition sites. The braconid koinobiont endoparasitoid Dolichogenidea gelechiidivoris (Hymenoptera: Braconidae) efficiently parasitises larvae of Tuta absoluta (Lepidoptera: Gelechiidae), a major pest of tomato (Solanum lycopersicum). However, the attractive compounds used by the parasitoid to locate T. absoluta on host plants are not known. We therefore performed behavioural assays and chemical analyses to investigate the chemical basis of interactions between the parasitoid, the tomato plant and T. absoluta. Y-tube olfactometer bioassays revealed that D. gelechiidivoris was attracted to T. absoluta larvae-infested tomato plant volatiles and preferred volatiles of plants with a high infestation level than those with a low infestation level. The parasitoid was also attracted to volatiles of larval frass and to the sex pheromone of T. absoluta. Coupled gas chromatography–mass spectrometric analyses were performed on plant and frass volatiles. We found both qualitative and quantitative differences in volatile emission between healthy and T. absoluta larvae-infested tomato plants, where volatile emission rate increased with increasing infestation level. The most characteristic volatile compounds which distinguished T. absoluta larvae-infested plants from healthy plants were α-pinene, sabinene, β-myrcene, 2-carene, α-phellandrene, 3-carene, α-terpinene, β-phellandrene, (Z)-β-ocimene, (E)-β-ocimene, allo-ocimene, (E)-β-caryophyllene and methyl salicylate. With the exception of caryophyllene oxide, all larval frass volatile compounds were also found in tomato plant headspace volatiles. Olfactometer bioassays using synthetic compounds revealed that D. gelechiidivoris was attracted to α-pinene, β-myrcene, α-phellandrene, α-terpinene, β-ocimene, methyl salicylate and (E)-β-caryophyllene, and the 7-component blend of these attractants elicited the greatest attraction in the parasitoid. These findings open new avenues for exploiting these attractants as kairomone-based lures to recruit and retain the parasitoid in tomato fields for the biological control of T. absoluta.

The African citrus triozid, Trioza erytreae Del Guercio (Hemiptera: Triozidae) is one of the primary vectors of the bacterium Candidatus Liberibacter spp. which causes citrus greening, a disease of global economic importance in citrus production. Despite its economic importance, little is known about its chemical ecology. Here, we used behavioral assays and chemical analysis to study the chemical basis of interaction between T. erytreae and one of its preferred host plants, Citrus jambhiri. In dual choice Y-tube olfactometer assays, lemon leaf odors attracted females but not males compared to plain air or solvent controls. However, in a petri dish arena assay, both sexes were arrested by lemon leaf odors. Coupled gas chromatography-mass spectrometry (GC/MS) analysis revealed quantitative differences in the odors of flushing and mature leaves, dominated by terpenes. Twenty-six terpenes were identified and quantified. In Petri dish arena assays, synthetic blends of the most abundant terpenes mimicking lemon flushing leaf odors elicited varying behavioral responses from both sexes of T. erytreae. A nine-component blend and a blend of the three most abundant terpenes; limonene, sabinene and β-ocimene arrested both sexes of T. erytreae. In contrast, a six-component blend lacking in these three components elicited an avoidance response in both sexes. Furthermore, both sexes of T. erytreae preferred the three-component synthetic blend to lemon crude volatile extract. These results suggest that lemon terpenes might be used in the management of T. erytreae.

Several abiotic factors influence the chemical composition of essential oils. Understanding these factors is an important step in developing quality products that meet market demands. This research work aims to study the chemical composition of the essential oils of ylang-ylang (Cananga odorata, forma genuina) according to the maturity of flowers. The volatile compounds of ylang-ylang flowers from Reunion Island were extracted by hydrodistillation and the samples were analyzed by high resolution gas chromatography coupled with mass spectrometry (GC-MS) allowing for the identification of 70 volatile compounds. The chemical composition of the essential oils extracted from the flowers at 5 different stages of development varies both qualitatively and quantitatively. The volatile compounds observed belong to 4 chemical groups which are esters, alcohols, terpenes, and ether-oxides. The synthesis of light oxygenated compounds is largely the predominant chemical subgroup in all stages of development. Their relative content is considerably increased during flower ripening with a peak concentration in stage 4 (SD4). The highest concentrations of non-terpene esters and heavy oxygenated compounds are found in stages 1 (SD1) and (SD5), respectively, while no chemical subgroup is dominant in the intermediate stages 2 (SD2) and (SD3). The dynamics of volatile compounds have also been studied. This study established that the stage of development of ylang-ylang flowers significantly influences the dynamics of volatile compounds in the extracted essential oils. Total oxygenated compounds that are highly odoriferous in essential oils increase progressively and significantly with flower maturity, unlike hydrocarbon terpenes, which are less valuable in terms of their contribution to the fragrance and following opposite kinetics; suggesting that odoriferous properties increase with the development of the flower, with a higher intensity at SD4.

Kairomones are chemical signals that mediate interspecific interactions beneficial to organisms that detect the cues. These attractants can be individual compounds or mixtures of herbivore-induced plant volatiles (HIPVs) or herbivore chemicals such as pheromones, i.e., chemicals mediating intraspecific communication between herbivores. Natural enemies eavesdrop on kairomones during their foraging behaviour, i.e., location of oviposition sites and feeding resources in nature. Kairomone mixtures are likely to elicit stronger olfactory responses in natural enemies than single kairomones. Kairomone-based lures are used to enhance biological control strategies via the attraction and retention of natural enemies to reduce insect pest populations and crop damage in an environmentally friendly way. In this review, we focus on ways to improve the efficiency of kairomone use in crop fields. First, we highlight kairomone sources in tri-trophic systems and discuss how these attractants are used by natural enemies searching for hosts or prey. Then we summarise examples of field application of kairomones (pheromones vs. HIPVs) in recruiting natural enemies. We highlight the need for future field studies to focus on the application of kairomone blends rather than single kairomones which currently dominate the literature on field attractants for natural enemies. We further discuss ways for improving kairomone use through attract and reward technique, olfactory associative learning, and optimisation of kairomone lure formulations. Finally, we discuss why the effectiveness of kairomone use for enhancing biological control strategies should move from demonstration of increase in the number of attracted natural enemies, to reducing pest populations and crop damage below economic threshold levels and increasing crop yield.

International audience; 1. Tsetse flies (Diptera: Glossinidae) are K‐strategist species and deposit a single larva at 10‐day intervals in specific sites. As larviposition site selection strongly impacts reproductive success, the selection of larviposition sites is unlikely to be random and will be subject to strong selective processes, probably mediated by specific cues.2. This study was designed to assess the existence of an aggregation effect in the palpalis group and to test its potential chemical nature (contact or volatile compounds). The larviposition site selection of Glossina palpalis gambiensis was studied according to the presence of conspecific and heterospecific larvae (morsitans group) buried in substrates. Three sets of experiments were performed with either individual or grouped gravid females and with or without physical access to the substrate.3. In individual larviposition experiments, females were more likely to select trays with buried larvae than unconditioned sand (63.2% and 36.8%, respectively; P

Dark chocolate samples were previously classified into four sensory categories. The classification was modelled based on volatile compounds analyzed by direct introduction mass spectrometry of the chocolates&rsquo, headspace. The purpose of the study was to identify the most discriminant odor-active compounds that should characterize the four sensory categories. To address the problem, a gas chromatography-olfactometry (GC-O) study was conducted by 12 assessors using a comparative detection frequency analysis (cDFA) approach on 12 exemplary samples. A nasal impact frequency (NIF) difference threshold combined with a statistical approach (Khi&sup2, test on k proportions) revealed 38 discriminative key odorants able to differentiate the samples and to characterize the sensory categories. A heatmap emphasized the 19 most discriminant key odorants, among which heterocyclic molecules (furanones, pyranones, lactones, one pyrrole, and one pyrazine) played a prominent role with secondary alcohols, acids, and esters. The initial sensory classes were retrieved using the discriminant key volatiles in a correspondence analysis (CA) and a hierarchical cluster analysis (HCA). Among the 38 discriminant key odorants, although previously identified in cocoa products, 21 were formally described for the first time as key aroma compounds of dark chocolate. Moreover, 13 key odorants were described for the first time in a cocoa product.

International audience; This study explores the ability of lactic acid bacteria (LAB) to ferment soy juice. The ability of 276 LAB strains from 25 species to ferment the principal soy carbohydrates, sucrose, raffinose or stachyose was tested in synthetic media and a soy juice. Fermented soy juices (FSJs) were characterized for their odor. Selected FSJs were characterized by targeted metabolomics. All Streptococcus, 83% of Leuconostoc and Lactobacillus and 41% of Lactococcus strains were sucrose-positive, while only 36% of all the LAB strains tested were raffinose-positive and 6% stachyose-positive. Nearly all (97%) the sucrose-positive strains fermented soy juice, indicating that an ability to use sucrose is a good criterion to select strains for soy juice fermentation. Among the most efficient acidifying strains, 46 FSJs had an odor deemed to be acceptable. FSJ composition was dependent on both species and strains: 17/46 strains deglycosylated soy juice isoflavones, the 27 S. thermophilus strains converted a mean 4.4 ± 0.1 g/L of sucrose into 3.0 ± 0.1 g/L of lactic acid versus 5.2 ± 0.1 g/L into 2.2 ± 0.1 g/L for the 18 Lactobacillus and one Lactococcus strains. This study highlights the diversity of the metabolic profiles of LAB strains in soy juice fermentation.

This study identified biogenic amines, fatty acids, and volatile compounds in adjuevan, an Ivorian traditionally salted and fermented fish. Samples were obtained from two processing methods (method 1: entire fish adjuevan; method 2: both sides filleted adjuevan) with the fish species Galeoides decadactylus. Biogenic amines found in freshly produced adjuevanwere histamine, putrescine, cadaverine, tyramine, -phenyl ethylamine, and spermidine. Among these, the most prevalent were -phenyl ethylamine and cadaverine. Biogenic amine contents varied according to the processing method but re-mained lower than levels considered hazardous for human health. The major fatty acids present in adjuevan from method 1 were docosahexaenoic acid, palmitic acid, and oleic acid. In adjuevan from method 2, the major fatty acids were oleic acid, stearic acid, and palmitic acid. The omega ()-3/-6 ratio was 8.87 and 4.12 for adjuevan from methods 1 and 2, respec-tively. Most of the fatty acids are considered healthy fats, making adjuevan a useful food for treating and preventing life-style diseases. The volatile compounds found composed of 19 aldehydes, 12 alcohols, 7 esters, 7 ketones, 3 furans, 10 aro-matic compounds, and 7 acids with aldehyde, alcohol, and ester compounds as the predominant groups. Among the alde-hydes, 2,4-heptadienal (E,Z), octanal, and 2-octenal (E) were most prevalent in adjuevan from method 1, whereas 2-none-nal (E), 2,4-heptadienal (E,Z), and octanal were most prevalent in adjuevan from method 2.

L’intelligence des arbres est un sujet qui passionne les populations urbaines. Elle fait l’objet d’un débat animé entre les différents acteurs du secteur forestier. La présente note vise à objectiver ce débat en synthétisant les connaissances récentes sur le sujet. Elle montre que les arbres peuvent communiquer entre eux, soit via des molécules volatiles, soit via des échanges souterrains, notamment grâce à un réseau mycorhizien. Les arbres peuvent aussi percevoir la lumière et les sons. Ils peuvent donc s’adapter à un environnement changeant, ce qui traduit une certaine forme d’intelligence. Néanmoins, renoncer à l’exploitation du bois sur cette base ne peut être justifié. Cela se traduirait par des impacts environnementaux dont la portée est occultée par les détracteurs de l’exploitation forestière., Palaver around the trees: discussions about their intelligence to the drifts of anthropomorphismThe intelligence of trees is an issue that fascinates people in urban areas. It is the subject of passionate debate between forest sector stakeholders. This article aims to objectify this debate by synthesizing recent knowledge on the subject. It shows that trees can communicate with each other, either via volatile molecules or via underground exchanges, in particular through a mycorrhizal network. Trees can also perceive light and sound. They can therefore adapt to a changing environment, which reflects a certain form of intelligence. Nevertheless, abandoning timber logging for this reason is not acceptable. This would result in environmental impacts that are often overlooked by the opponents of logging.

The variegated coffee bug Antestiopsis thunbergii Gmelin is a key pest of Coffea arabica in East Africa. Although the bug feeds on various parts of the coffee plant, it has a strong preference for mature green berries which are essential for the bug to complete its life cycle, reproduce and enhance its longevity. To locate mature green coffee berries, we hypothesized that second instar nymphs, which are the most mobile and active feeding immature stage of the bug, must rely on key volatile compounds emitted by the host for recognition. We tested this hypothesis using behavioral and electrophysiological assays and chemical analysis. In olfactometer assays, the second instar nymphs were strongly attracted to volatiles emitted from mature green berries but avoided those from ripe coffee berries of C. arabica. Coupled gas chromatography–electroantennographic detection (GC/EAD) isolated five antenally active components from mature green berries volatiles, four of which were identified by coupled GC–mass spectrometry as toluene, anisole, methyl 3-ethyl-4-methylpentanoate and (5S,7S)-conophthorin. In concentration assays, in which second instar nymphs did not respond to toluene, they were strongly attracted to anisole, methyl 3-ethyl-4-methylpentanoate and (5S,7S)-conophthorin, and a blend from the three compounds at concentrations lower or equivalent to the natural volatile extract. Our results suggest that the blend from these three compounds allows host recognition in second instar nymphs of the variegated coffee bug and is a candidate kairomone for monitoring the pest in coffee plantations.

Objectifs/ObjectivesThe study aims to improve knowledge over LAB characteristics to ferment a commercial soy juice. Matériels et Méthodes/Materials and methodsFirst 280 strains of LAB from 23 different species of Lactococcus, Streptococcus, Lactobacillus and Leuconostoc genera were tested for their abilities to ferment soy juice containing sucrose, raffinose or stachyose as carbon source and to acidify synthetic media containing sucrose, raffinose or stachyose as unique carbon source. Then, fermented soy juices (FSJ) were produced by 10 h of fermentation (inoculation level 1 %), followed by 14 days of storage at 4 °C. The scents of FSJ were sensorially characterized and FSJ’s primary and secondary metabolites were analyzed. Résultats principaux/Main ResultsWithin 48 h, 39 % of L. lactis strains, 82 % of Lactobacillus strains and all S. thermophilus strains could acidify the synthetic medium with sucrose, as previously described in fermentation patterns of these species. 101 strains representing 18 species could use raffinose and 12 strains representing 6 species could use stachyose. 94 % of the strains that could use sucrose could also ferment soy juice, whose sucrose is the major sugar. Interestingly, 3 strains from species never tested to ferment soy juice, L. kunkeei, L. xiangfangensis and L. pontis revealed abilities to ferment soy juice. Among the 280 strains, 116 strains could acidify soy juice below 6.0 pH units within 10 h. Among the 116 corresponding FSJs, the scents of 48 FSJs were judged as acceptable. The use of sucrose was species-dependent: less residual sucrose was present in FSJs from strains of L. plantarum, L. pentosus, L. lactis, L. delbrueckii and L. coryniformis species compared to S. thermophilus strains. None of the strains used raffinose nor stachyose. S. thermophilus strains produced more lactic acid and less acetic acid than the other strains, in agreement with their homolactic metabolism. Due to acetic acid, FSJs from L. plantarum were more frequently described as ‘sour’. In addition, some strains presented specific traits. For example, CIRM-BIA2115 of L. plantarum produced a floral scent in FSJ likely related to the production of phenylethan-1-ol observed. ConclusionThe present study is an advance on the knowledge of LAB diversity and their capacity to ferment soy juice. It shows that LAB capacity to use sucrose is important to ferment soy juice and highlights the importance of screening due to the diversity of LAB metabolism.

Insect parasitoids are under selection pressure to optimize their host location strategy in order to maximize fitness. In parasitoid species that develop on host eggs, one of these strategies consists in the exploitation of oviposition-induced plant volatiles (OIPVs), specific blends of volatile organic compounds released by plants in response to egg deposition by herbivorous insects. Plants can recognize insect oviposition via elicitors that trigger OIPVs, but very few elicitors have been characterized so far. In particular, the source and the nature of the elicitor responsible of egg parasitoid recruitment in the case of plants induced with oviposition by stink bugs are still unknown. In this paper, we conducted behavioral and molecular investigations to localize the source of the elicitor that attracts egg parasitoids and elucidate the role of host mating in elicitation of plant responses. We used as organism study model a tritrophic system consisting of the egg parasitoid Trissolcus basalis, the stink bug host Nezara viridula and the plant Vicia faba. We found that egg parasitoid attraction to plant volatiles is triggered by extracts coming from the dilated portion of the stink bug spermathecal complex. However, attraction only occurs if extracts are obtained from mated females but not from virgin ones. Egg parasitoid attraction was not observed when extracts coming from the accessory glands (mesadene and ectadene) of male hosts were applied, either alone or in combination to plants. SDS-PAGE electrophoresis correlated with olfactometer observations as the protein profile of the dilated portion of the spermathecal complex was affected by the stink bug mating status suggesting post-copulatory physiological changes in this reproductive structure. This study contributed to better understanding the host location process by egg parasitoids and laid the basis for the chemical characterization of the elicitor responsible for OIPV emission.

In oenology, bio-protection consists in adding bacteria, yeasts or a mixture of microorganisms on grape must before fermentation in order to reduce the use of chemical compounds such as sulphites. More particularly, non-Saccharomyces yeasts are used as a total or partial alternative to sulphites. However, scientific data capable of proving the effectiveness of adding these yeasts on grape must remain scarce. A single study in white winemaking showed that early addition of a non-Saccharomyces T. del¬brueckii strain could be a microbiological and chemical alternative to sulphites (Simonin et al., 2018). However, there is a lack of scientific data concerning red winemaking where the process allows to leave the yeasts added during the whole winemaking. This study reports for the first time the analysis of microbio¬logical and chemical effects of one Metschnikowia pulcherrima strain, inoculated at the beginning of the red winemaking process in three wineries as an alternative to sulphiting. The implantation of the M. pulcherri¬ma was successful in all the wineries and effectively limited the development of spoilage microorganisms in the same way as the addition of sulphites. The addition of non-Saccharomyces strain could protect must and wine from oxidation as demonstrated by the proanthocyanidin and anthocyanin analysis. Adding M. pulcherrima had no effect on wine volatile compounds and sensorial analysis. However, the un¬targeted analysis by FTICR-MS highlighted a bio-protection signature and an activation of certain metabolic pathways.

International audience; Acibenzolar-S-methyl (ASM) is a chemical compound, which is able to induce resistance in several model and non-model plants, but the end-players of this induced defense remain ill-defined. Here, we test the hypothesis that treatment with ASM can protect apple (Malus × domestica) against the rosy apple aphid (Dysaphis plantaginea) and investigate the defense molecules potentially involved in resistance. We measured aphid life traits and performed behavioral assays to study the effect of ASM on plant resistance against the aphid, and then combined transcriptomic, bioinformatics, metabolic and biochemical analyses to identify the plant compounds involved in resistance. Plants treated with ASM negatively affected several life traits of the aphid and modified its feeding and host seeking behaviors. ASM treatment elicited up-regulation of terpene synthase genes in apple and led to the emission of (E,E)-α-farnesene, a sesquiterpene that was repellent to the aphid. Several genes encoding amaranthin-like lectins were also strongly up-regulated upon treatment and the corresponding proteins accumulated in leaves, petioles and stems. Our results link the production of specific apple proteins and metabolites to the antibiosis and antixenosis effects observed against Dysaphis plantaginea, providing insight into the mechanisms underlying ASM-induced herbivore resistance.

To be able to account for sensory quality earlier in the assessment of a new banana hybrid in a selection scheme, the ability of instrumental parameters to predict the sensory perception of banana odour and aroma was investigated. Thirteen cultivated bananas and four new triploid hybrids were characterized by both sensory profiling and chemical analyses. PLS regression models were built using cultivated bananas, and the quality of predictions was validated using hybrids. Forty-one volatile compounds were detected in banana cultivars by SPME–GC–MS. Major differences were observed in the distribution of volatile compounds among cultivars. 3-methylbutyl esters were the most abundant in the 17 banana cultivars. PLS models were able to predict four odours (‘banana’, ‘fermented’, ‘grassy’, and ‘chemical’) and five aromas (‘banana’, ‘fermented’, ‘chemical’, ‘medicinal’, and ‘pineapple’) with a goodness of fit (R2) between 0.52 and 0.71. Two butanoate esters, 2-methylpropyl butanoate and 3-methylbutyl butanoate, mainly contributed to ‘banana’ odour and aroma. Two other esters, 3-methylbutyl acetate and ethyl 3-methylbutanoate contributed to the ‘fermented’, ‘chemical’, and ‘medicinal’ notes, suggesting that interactions between volatile compounds could lead to differences in the perception of odours and aromas. The ‘grassy’ odour was the only attribute which was negatively associated with volatile compounds. Total organic acids enhanced the ‘pineapple’ aroma, whereas it reduced the perception of the ‘banana’ aroma, suggesting interactions between volatile and non-volatile compounds or cognitive associations between aromas and sourness. In conclusion, PLS models can now be used for high throughput phenotyping to predict odours and aromas in dessert banana.

International audience; Fungi are commonly identified as the cause for dairy food spoilage. This can lead to substantial economic losses for the dairy industry as well as consumer dissatisfaction. In this context, biopreservation of fermented dairy products using lactic acid bacteria, propionibacteria and fungi capable of producing a large range of antifungal metabolites is of major interest. In a previous study, extensive screening was performed in vitro and in situ to select 3 dairy fermentates (derived from Acidipropionibacterium jensenii CIRM-BIA1774, Lactobacillus rhamnosus CIRM-BIA1952 and Mucor lanceolatus UBOCC-A-109193, respectively) with antifungal activity. The aim of the present study was to determine the main compounds responsible for this antifungal activity. Fifty-six known antifungal compounds as well as volatiles were targeted using different analytical methods (conventional LC and GC, GC–MS, LC-QToF). The most abundant antifungal compounds in P. jensenii-, L. rhamnosus- and M. lanceolatus-derived fermentates corresponded to propionic and acetic acids, lactic and acetic acids, and butyric acid,respectively. Many other antifungal compounds (organic acids, free fatty acids, volatile compounds) were identified but at lower levels. In addition, an untargeted approach using nano LC-MS/MS identified a 9-amino acid peptide derived from αs2-casein in the L. rhamnosus-derived fermentate. This peptide inhibited M. racemosus and R. mucilaginosa in vitro. This study provides new insights on the molecules involved in antifungal activities of food-grade microorganism fermentates which could be used as antifungal ingredients in the dairy industry.

International audience; Direct-injection mass spectrometry (DIMS) techniques have evolved into powerful methods to analyse volatile organic compounds (VOCs) without the need of chromatographic separation. Combined to chemometrics, they have been used in many domains to solve sample categorization issues based on volatilome determination. In this paper, different DIMS methods that have largely outperformed conventional electronic noses (e-noses) in classification tasks are briefly reviewed, with an emphasis on food-related applications. A particular attention is paid to proton transfer reaction mass spectrometry (PTR-MS), and many results obtained using the powerful PTR-time of flight-MS (PTR-ToF-MS) instrument are reviewed. Data analysis and feature selection issues are also summarized and discussed. As a case study, a challenging problem of classification of dark chocolates that has been previously assessed by sensory evaluation in four distinct categories is presented. The VOC profiles of a set of 206 chocolate samples classified in the four sensory categories were analysed by PTR-ToF-MS. A supervised multivariate data analysis based on partial least squares regression-discriminant analysis allowed the construction of a classification model that showed excellent prediction capability: 97% of a test set of 62 samples were correctly predicted in the sensory categories. Tentative identification of ions aided characterisation of chocolate classes. Variable selection using dedicated methods pinpointed some volatile compounds important for the discrimination of the chocolates. Among them, the CovSel method was used for the first time on PTR-MS data resulting in a selection of 10 features that allowed a good prediction to be achieved. Finally, challenges and future needs in the field are discussed.

International audience; Free- and glycosylated-volatile profiles of 14 strawberry varieties, 9 for industrial processing (‘Darselect’, ‘Clery’, ‘Honey’, ‘Honeoye’, ‘Siabel’, ‘FCMO060’, ‘Fraise19’, 2 ‘Senga Sangana’) and 5 for fresh market (‘Gariguette’, ‘Charlotte’, ‘CIR121’, 2 ‘Clery’ (full-field and hydroponic)), were compared. All volatiles were analysed by GCMS. Volatiles from glycosides were first released by direct enzymatic hydrolysis. The extraction method was optimised for furaneol, a key component of strawberry aroma. More than 60 volatile compounds were identified, the most abundant being butyl acetate (average: 17 mg/kg), furaneol (average: 2 mg/kg) and free hexanoic acid (average: 3 mg/kg). Free-volatile profiles showed a split between fresh market strawberries, distinguished by esters and carbonyl molecules like isobutyl acetate or hexanal, and strawberries for processing, distinguished by molecule like 3-penten-2-one and 1-butanol. The three ‘Clery’ profiles were different notably in their hexanal, 4- vinylguaiacol and 3-penten-2-one concentrations. The glycosylated volatile profiles were similar among most strawberry varieties with, as major glycosylated volatiles, hexanoic acid (average: 1.7 mg/kg), benzyl alcohol (average: 0.5 mg/kg), gamma-decalactone (average: 0.5 mg/kg) and coumaran (average: 2.5 mg/kg). The potential for volatile enhancement by deconjugation was different. Potentially fresh market strawberries had a volatile increase of 6% against 50% for strawberries for processing.

International audience; Recently isolated spore-forming pigmented marine bacteria, Bacillus indicus HU36 and Bacillus firmus GB1 are sources of carotenoids ( fifteen distinct yellow and orange pigments and thirteen distinct pink pigments, respectively). They are glycosides of oxygenated lycopene derivatives (apo-lycopenoids) and are assumed to be more heat- and gastric-stable than common carotenoids. In this study, the oxidation by O2 of the bacterial carotenoids was initiated by free iron (FeII and FeIII) or by heme iron (metmyoglobin) in a mildly acidic aqueous solution mimicking the gastro-intestinal compartment and compared to the oxidation of the common dietary carotenoids β-carotene, lycopene and astaxanthin. Under these conditions, all bacterial carotenoids appear more stable in the presence of heme iron vs. free iron. Carotenoid autoxidation initiated by FeII is relatively fast and likely involves reactive oxygen–iron species derived from FeII and O2. By contrast, the corresponding reaction with FeIII is kinetically blocked by the slow preliminary reduction of FeIII into FeII by the carotenoids. The stability of carotenoids toward autoxidation increases as follows: β-carotene < lycopene < astaxanthin < HU36 and GB1. In particular, bacterial carotenoids react more quickly than reference carotenoids with FeIII, but much more slowly than the reference carotenoids with FeII. This reaction is correlated with the structure of the carotenoids, which can have opposite effects in a micellar system: bacterial carotenoids with electro-attracting terminal groups have a lower reducing capacity than b-carotene and lycopene. However, their polar head favours their location close to the interface of micelles, in closer contact with oxidative species. Kinetic analyses of the ironinduced autoxidation of astaxanthin and HU36 carotenoids has been performed and gives insights in the underlying mechanisms.

This work reports the identification of volatile compounds involved in the particular and atypical flavor detected in Vitis vinifera red Merlot and Cabernet Sauvignon wines made with grapes infected and wilted by brown rot (Plasmopara viticola). Must made from withered grapes had green aromas while red wines were marked by intense odor reminiscent of green, herbaceous notes but also figs and cooked fruit. Thanks to GC-O and GC–MS analysis, cooked fruit notes were identified as 3-methyl-2,4-nonanedione, γ-nonalactone and γ-decalactone, whereas herbaceous and green aromas were identified as (Z)-1,5-octadien-3-one and 3-isobutyl-2-methoxypyrazine. We show that the organoleptic impact of P. viticola is more pronounced in Merlot wines compared to Cabernet Sauvignon ones. The highest levels of 3-methyl-2,4-nonanedione (75.3 ng/L) were found in old Merlot wines made with 20% infected berries, suggesting the incidence of berry quality on the ability of a wine to age.

Emission of volatile compounds is highly influenced by environment surrounding the fruit in the tree. Little is known about aroma constituents in ripe, fresh figs (Ficus carica L.). Ou hypothesis is that the training of the tree and pruning practice can improve light penetration inside the canopy, and consequently further enhance the aroma released by the fruit. Materials and methods – Fig volatile compounds were extracted and identified using Accelerated solvent extraction-Gas chromatography-Mass spectrometry (ASE-GC-MS) in the fruit from cultivar ‘Bouhouli’ growing in Northwest Tunisia. Results and discussion – Fifty-one volatiles were identified in the fruit. Fig volatile range is composed by three major groups (esters, ketones and alcohols) with butyl, isoamyl and hexyl acetate and acetoin (3-hydroxy-2-butanone) being the four major compounds. Of these four compounds, the isoamyl acetate (with a strong fruity, banana-like smell) and acetoin (described as giving a milk-like note) had the highest aroma potential. Analysis of the volatile blend released by the fruit from two different positions in the tree has shown quantitative as well as qualitative changes between outside and inside the canopy. Sun-exposed figs developed a total of 3,539 μg kg-1 fresh weight (FW) versus 2,657 μg kg-1 FW for shaded figs. Acetoin, the major volatile compound, represented 48% of total concentrations in sun-exposed fruit, and 44% in shaded figs. Principal component analysis (PCA) showed that volatile profile of figs ripened outside the canopy was closely associated to sesquiterpenes and alcohols. Other volatiles found to make difference between fruits from the two position in the tree were: linalool, (E)-2-heptenal and 2,4-decadienal (P≤0.05). Conclusion – Changes in volatiles released by figs from both periphery and underneath the canopy were rather quantitative and concern some compounds having little impac on aroma of the ripe fruit. A proper orchard management will contribute to improve the aromatic fruit quality in figs.

Jicaro seeds (Crescentia alata) are widely consumed in Central America, primarily as a popular tasty and nutritious beverage called “horchata”. Seeds are roasted to develop a specific aroma through a process that has never been explored. Volatile compounds, extracted from raw and roasted jicaro seeds (140 °C for 140 s) by SAFE (Solvent Assisted Flavor Evaporation), were analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). Twenty-seven volatile compounds were isolated, among which, ethyl-2-methylbutyrate was designated by olfactometry as providing the characteristic jicaro note (0.16 and 0.47 mg/kg dry basis (d.b.) in raw and roasted seeds, respectively). The release of volatile compounds from the Maillard reaction, such as pyrazines, and the increase of ethyl-2-methylbutyrate after roasting, exhausted the pleasant jicaro aroma. This mild roasting process had a slight impact on polyphenol, fructose and free amino acid contents, in agreement with the Maillard reaction. Confocal microscopy showed the coalescence of lipids in roasted jicaro seeds, which might explain the higher extracted fat content. Programa Regional de Seguridad Alimentaria y Nutricional/[C-15-2012]/PRESANCA II/Italia Consejo Superior Universitario Centroamericano/[C-15-2012]/CSUCA/Guatemala Institut Français Amérique Centrale/[]/IFAC/Costa Rica European Union Latin America Academic Links/[EULA1401013]/EULAlinks/Alemania UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Centro Nacional de Ciencia y Tecnología de Alimentos (CITA)

The applicability of comprehensive two-dimensional gas chromatography (GC×GC) using a single-stage thermal modulator was explored for the analysis of honeybush tea (Cyclopia spp.) volatile compounds. Headspace solid phase micro-extraction (HS-SPME) was used in combination with GC×GC separation on a non-polar × polar column set with flame ionisation (FID) detection for the analysis of fermented Cyclopia maculata, Cyclopia subternata and Cyclopia genistoides tea infusions of a single harvest season. Method optimisation entailed evaluation of the effects of several experimental parameters on the performance of the modulator, the choice of columns in both dimensions, as well as the HS-SPME extraction fibre. Eighty-four volatile compounds were identified by co-injection of reference standards. Principal component analysis (PCA) showed clear differentiation between the species based on their volatile profiles. Due to the highly reproducible separations obtained using the single-stage thermal modulator, multivariate data analysis was simplified. The results demonstrate both the complexity of honeybush volatile profiles and the potential of GC×GC separation in combination with suitable data analysis techniques for the investigation of the relationship between sensory properties and volatile composition of these products. The developed method therefore offers a fast and inexpensive methodology for the profiling of honeybush tea volatiles. Graphical abstract Surface plot obtained for the GC×GC-FID analysis of honeybush tea volatiles.

International audience; Rapeseed meal is a cheap and abundant raw material, particularly rich in phenolic compounds of biotechnological interest. In this study, we developed a two-step bioconversion process of naturally occurring sinapic acid (4-hydroxy-3,5-dimethoxycinnamic acid) from rapeseed meal into canolol by combining the complementary potentialities of two filamentous fungi, the micromycete Aspergillus niger and the basidiomycete Neolentinus lepideus. Canolol could display numerous industrial applications because of its high antioxidant, antimutagenic and anticarcinogenic properties. In the first step of the process, the use of the enzyme feruloyl esterase type-A (named AnFaeA) produced with the recombinant strain A. niger BRFM451 made it possible to release free sinapic acid from the raw meal by hydrolysing the conjugated forms of sinapic acid in the meal (mainly sinapine and glucopyranosyl sinapate). An amount of 39 nkat AnFaeA per gram of raw meal, at 55 °C and pH 5, led to the recovery of 6.6 to 7.4 mg of free sinapic acid per gram raw meal, which corresponded to a global hydrolysis yield of 68 to 76% and a 100% hydrolysis of sinapine. Then, the XAD2 adsorbent (a styrene and divinylbenzene copolymer resin), used at pH 4, enabled the efficient recovery of the released sinapic acid, and its concentration after elution with ethanol. In the second step, 3-day-old submerged cultures of the strain N.lepideus BRFM15 were supplied with the recovered sinapic acid as the substrate of bioconversion into canolol by a non-oxidative decarboxylation pathway. Canolol production reached 1.3 g/L with a molar yield of bioconversion of 80% and a productivity of 100 mg/L day. The same XAD2 resin, when used at pH 7, allowed the recovery and purification of canolol from the culture broth of N. lepideus. The two-step process used mild conditions compatible with green chemistry.

International audience; The aim of this study was to investigate the influence of volatile compounds from four secondary host plants on the ability of [i]Dinarmus basalis[/i] Rond. (Hymenoptera: Pteromalidae) to locate, recognize, and parasitize its host, 4th instar larvae or pupae of [i]Callosobruchus maculatus[/i] F. ([i]Coleoptera: Chrysomelidae[/i]). To examine this, strains of [i]D. basalis[/i] were transferred from cowpea seeds [i](Vigna unguiculata[/i] (L.) Walp. (Fabales: [i]Fabaceae[/i])) to pigeon pea ([i]Cajanus cajan[/i] (L.) Millsp.) and two varieties of Bambara groundnut ([i]Vigna subterranea[/i] (L.) Verdc.) seeds. The ability of D. [i]basalis[/i] females to recognize the volatile compounds emanating from their complex host plant was tested by using a Y-tube olfactometer and a three-dimensional device. The results suggest that when females have a choice between pure air and the air emanating from their complex host of origin, they are attracted to the air tainted by the volatile compounds they have become accustomed to. They spent significantly more time (p < 0.0001) in the branch of the tube leading to the odorous air than in the tube leading to the pure air. When females from pigeon pea seed hosts were offered a choice between cowpea and pigeon pea seeds, all containing 4th instar larvae, the familiar odor of pigeon pea seeds were most attractive. When females from Bambara groundnut (white and striped) seed hosts were offered a choice between cowpea and pigeon pea seeds, all containing 4th instar larvae, they were significantly attracted to the odour of cowpea seeds. In the three-dimensional system, the females from the four strains did not appear to have any preference for a given type of seed containing 4th instar larvae or pupae. The parasitism rate remained high on all four types of seeds used. These results show that the use of D. [i]basalis[/i] as a biological control agent is possible in host changing situations where C. maculatus starts to attack other legumes. The results of this study also provide information supporting the behavioral plasticity of D. [i]basalis[/i]. Understanding the mechanisms involved in the adaptive phenomena of biological control agents is discussed in the context of the development of adequate methods of pest control.

International audience; The volume, composition and organic load of wastewaters from five wineries producing white, rosé and red wines by thermovinification, as well as traditionally vinified red wines (75 000 hL to 240 000 hL wine), were studied in terms of the vinification methods used. Liquid-phase vinifications (white, rosé, thermovinification) produce wastewaters rich in sugars: 70% of the chemical oxygen demand (COD) when the must is treated, and flows depend on the daily supply of grapes, representing 40 to 46% of the annual volume of wastewaters during the first month of activity (September). In contrast,solid-phase vinifications do not produce large quantities of waste at harvest, and wastewaters produced mainly during devatting are characterised by a predominance of ethanol (≤ 75% COD) and by staggered flows towards the second month (October), which are less intense (26.7 to 33.6%) and more spread out. The specific pollution coefficients of liquid-phase vinifications (5.18 to 6.04 kg COD/t grapes) are greater than those of solid-phase vinifications (3.82 kg COD/t grapes). The higher the winery’s liquid-phase vinification rate, the more the maximal monthly volume of waste will be intense and early. These results should contribute to the improved design and management of winery wastewater treatments.

International audience; Coffee grown at high elevations fetches a better price than that grown in lowland regions. This study was aimed at determining whether climatic conditions during bean development affected sensory perception of the coffee beverage and combinations of volatile compounds in green coffee. Green coffee samples from 16 plots representative of the broad range of climatic variations in Réunion Island were compared by sensory analysis. Volatiles were extracted by solid phase micro-extraction and the volatile compounds were analysed by GC-MS. The results revealed that, among the climatic factors, the mean air temperature during seed development greatly influenced the sensory profile. Positive quality attributes such as acidity, fruity character and flavour quality were correlated and typical of coffees produced at cool climates. Two volatile compounds (ethanal and acetone) were identified as indicators of these cool temperatures. Among detected volatiles, most of the alcohols, aldehydes, hydrocarbons and ketones appeared to be positively linked to elevated temperatures and high solar radiation, while the sensory profiles displayed major defects (i.e. green, earthy flavour). Two alcohols (butan-1,3-diol and butan-2,3-diol) were closely correlated with a reduction in aromatic quality, acidity and an increase in earthy and green flavours. We assumed that high temperatures induce accumulation of these compounds in green coffee, and would be detected as off-flavours, even after roasting. Climate change, which generally involves a substantial increase in average temperatures in mountainous tropical regions, could be expected to have a negative impact on coffee quality. (Résumé d'auteur)

Cheese flavour results from the activity of many starter and non-starter bacteria that contribute to the conversion of curd components into a number of odorant and sapid compounds. Growing bacteria participate in flavour-related reactions, as well as non‐proliferating or even non‐cultivable bacteria encountered during cheese ripening. Some enzymes released from lysed bacteria can participate as well. Many of the activities are strain-dependent, leading to the need of screening approaches to evaluate the flavouring potential of the strains. This lecture presents the main biochemical pathways for the production of flavour compounds and summarizes the variety of approaches used for screening purpose, with examples ranging from simplified in vitro systems to mini-cheese experiments

Development of volatile compounds contributing to cheese flavour primarily depends on the metabolic activity of bacterial cultures used during manufacture. Gas chromatography coupled to mass spectrometry (GC-MS) preceded by volatiles extraction is widely used for volatile analysis. The volatile profiles of ten strains of Lactobacillus casei/paracasei generated using a cheese model were assessed by GC-MS using two extraction methods, headspace solid-phase microextraction (HS-SPME) with DVB/CAR/PDMS fibre and HeadSpace-Trap (HS-Trap) with Tenax® adsorbent. Chromatographic data was processed using XCMS package of R software. Numbers of total fragments detected were 1788 for HSSPME and 2073 for HS-Trap method. After annotation, 70 and 64 compounds considered as flavour contributors were successfully identified in HS-SPME and HS-Trap profiles respectively, with 40 compounds in common. HS-SPME extracted numerous alcohols, esters and acids, while HS-Trap showed higher selectivity towards short aldehydes and ketones, pyrazine derivatives and specific sulfur-containing compounds. Comparison of common volatiles revealed high correlation in extraction of long-chain ketones and alcohols, but poorcorrelation for aldehydes, sulfur compounds and acids. Principal Component Analysis highlighted similar differences between individual samples using both extraction techniques.Although two extraction techniques identified distinct compounds in the samples, they equally represented differences within the sample set.

Untargeted metabolomics approaches are being developed and appear as a must in the modern food science and microbiology research to investigate food quality and safety. Our objective was to assess the relevance of untargeted metabolomics to explore for the first time Camembert cheese ripening, by using liquid chromatography coupled on-line with high resolution mass spectrometry. Metabolic fingerprints were found to differ significantly depending on the ripening time, pointing out the capacity of this approach to study microbial metabolism within cheese and its influence on the ripening process of Camembert cheese. Nearly a hundred metabolites were identified thanks to in-house and public databases. The results highlighted variations over the ripening process of a large diversity of well-known cheese metabolites such as 13 amino acids and 25 volatile compounds, but also less studied ones such as two vitamins and creatinine. As a consequence, untargeted metabolomics approach appears as a technology-driven opportunity to further deepen the characterization of the overall mechanisms of cheese ripening.

Du fait de problèmes de santé publique, l’industrie agroalimentaire doit réduire la quantité de sel et de matière grasse dans les aliments, et donc dans les charcuteries. Lors de la fabrication des saucissons secs, une diminution combinée des taux de sel et de matière grasse animale peut se traduire par des problèmes de stabilité microbiologique, des défauts d’arôme et de texture dus à des modifications physicochimiques et biochimiques. Dans ce contexte, les objectifs de cette thèse étaient : (1) d’étudier l’impact d’une réduction directe des teneurs en sel et en matière grasse animale sur les évolutions physicochimiques et biochimiques au sein des produits, (2) d’identifier les composés aromatiques responsables de l’arôme du saucisson sec, ainsi que leurs origines, (3) de développer de nouvelles formulations de saucissons secs à teneurs réduites en sodium et en acides gras saturés, et (4) d’étudier les transferts d’eau et sel et de développer une isotherme de sorption spécifique pour le saucisson sec. L’étude de l’effet d’une réduction directe combinée a mis en évidence la difficulté de fabriquer des saucissons secs à teneurs réduites en sel et en matière grasse animale, sans modifier les évolutions physicochimiques et biochimiques. Une identification des composés volatils odorants de saucissons secs de haut de gamme a permis de montrer que l’aromatisation par l’ail et le poivre noir pouvait être un levier technologique permettant d’améliorer la qualité aromatique des saucissons secs allégés en sel et en matière grasse animale. L’impact de l’aromatisation et d’une substitution partielle combinée du sel par le chlorure de potassium et du gras de bardière de porc par l’huile de tournesol oléique sur les propriétés physicochimiques, les réactions biochimiques et les attributs sensoriels de saucissons secs, a été étudié. Cette étude a montré le rôle important de l’aromatisation qui agit en introduisant des molécules aromatiques qui rehaussent l’acceptabilité des produits par les consommateurs, en tant qu’exhausteur de la perception du goût salé et aussi, sur les processus fermentaires qui vont conditionner l’aspect et la texture finale du produit. La substitution partielle combinée est une solution efficace pour conserver au mieux la qualité organoleptique des saucissons, en permettant, d’une part, d’éviter les défauts texturaux et sensoriels liés aux modifications physicochimiques, protéolytiques et lipolytiques générés par une réduction directe combinée, et d’autre part, d’améliorer l’arôme du produit en rehaussant les niveaux d’oxydations lipidique et protéique. L’étude des transferts d’eau et de sel a mis en évidence une migration du sel vers le coeur du saucisson, et a permis de déterminer des valeurs de diffusivité apparente de l’eau en surface de ces produits. Il a été montré qu’une forte réduction en matière grasse réduisait la diffusivité de l’eau à la surface du saucisson. Une isotherme de sorption spécifique permettant de prédire l’aw en fonction des teneurs en eau, en lipides et en sel a été construite en adaptant un modèle de Ross établi pour la gélatine salée et grasse., Because of public health problems, the food industry must lower sodium and animal fat contents in all food products, therefore in cured meat products. During dry-fermented sausage manufacture, a combined reduction both in salt and animal fat contents may induce microbial safety problems and textural and aroma defects due to physical-chemical and biochemical changes. On account of that, this work of thesis aims (1) to investigate the impact of a direct reduction on the salt and animal fat contents on the physical-chemical and biochemical evolutions in the products, (2) to identify the aromatic compounds responsible for the aroma of dry-fermented sausage, and their origins, (3) to develop new nutritionally-improved formulations of dry-fermented sausages with less sodium and saturated fatty acids, and (4) to study the impact of lipid and sodium chloride contents on water transfers in dry-fermented sausages and to build a specific sorption isotherm curve for dry sausages. The study of the effect of a combined direct reduction highlighted the difficulty of manufacturing sodium-reduced fat-reduced dry sausages, without affecting the physicalchemical and biochemical evolutions. Identification of odorous volatile compounds of high quality dry sausages showed that flavouring, especially garlic and black pepper, could be a good solution for improving the aromatic quality of salt-reduced fat-reduced dry-fermented sausages. The impact of flavouring and of a combined salt and animal fat replacement by potassium chloride and oleic sunflower oil, respectively, on physical-chemical properties, biochemical reactions and sensory attributes of dry-fermented sausages was then studied. This specific study showed the crucial role played by flavouring which introduces aromatic molecules that enhance the product acceptability by consumers, which acts as an enhancer of the saltiness perception and which improves the product appearance and texture by boosting the fermentation process. Consequently, the combined partial substitution is an efficient solution to preserve at best the organoleptic quality of the products, allowing, on one hand, avoiding the textural and sensory defects related to physical-chemical, proteolytic and lipolytic modifications induced by a combined direct reduction, and on the other hand, enhancing the product aroma by increasing the levels of lipid and protein oxidations. The study on water and salt transfers highlighted a salt diffusion towards the dry sausage core, and made it possible to determine values of apparent water diffusivity at the sausage surface. We demonstrated that a strong reduction in animal fat content significantly lowered the water diffusivity value at the product surface. A specific sorption isotherm curve based on a modified Ross model was built, allowing dry-fermented sausages water activity to be calculated as a function of water, fat and salt contents.

In Citrus species chromosome doubling naturally occurs in somatic embryos and doubled diploid plants often show better adaptation to adverse environmental condition. To understand the molecular determinants of stress acclimation, we examined the response to water deficit in diploid (2×VL) and doubled diploid (4×VL) seedlings of Volkamer lemon (Citrus limonia Osb.) assessing the profile of constitutive volatile organic compound (VOC) in control and stressed conditions. Physiological parameters and leaf volatile compound profiles were measured during water deficit and 24 h after rehydration of plants to field capacity. Net photosynthesis and stomatal conductance were reduced in water stressed leaves, with no significant differences between 2×VL and 4×VL plants. Malondialdehyde concentration, a marker of lipid peroxidation of cellular membranes, was significantly more higher in stressed 2×VL leaves than in 4×VL. The blend of constitutive VOC was different in control leaves being oxygenated monoterpenoids more abundant in 2×VL leaves, and monoterpenoids more abundant in 4×VL leaves. Water deficit did not stimulate biosynthesis of terpenoids, whereas accumulation of trans-2 hexenal, a green leaf volatile (GLV) synthesized after membrane denaturation, was observed in stressed leaves of 2×VL leaves, but not in 4×VL leaves. Semiquantitative PCR showed an increase of the expression of HPL, the gene encoding for hydroperoxidase lyase which catalyzes 2-hexenal formation, only in 2×VL plants. The expression of the putative dehydration transcription factor DREB2A was also observed only in 2×VL water stressed plants. This work shows that level of ploidy may alter constitutive content of GLV by Citrus, therefore likely affecting plants capacity of protection and interaction with other organisms. Whereas diploid and double diploid plants showed similar physiological responses to water deficit, a biochemical marker indicated that membranes of double diploid leaves were more resistant to the stress. These results provide intriguing insights into the regulation of terpenoids and oxylipins pathways as a function of polyploidization in a non-model plant species.

Many health authorities have targeted salt reduction in food products as a means to reduce dietary sodium intake due to the harmful effects associated with its excessive consumption. In the present work, we evaluated the effect of reducing sodium chloride (NaCl) content on the microbiological and biochemical characteristics of an experimental surface-ripened cheese. A control cheese (1.8% NaCl) and a cheese with a reduced NaCl content (1.3% NaCl) were sampled weekly over a period of 27d. Reducing NaCl content induced microbial perturbations such as the lesser development of the yeast Debaryomyces hansenii and the greater development of the gram-negative bacterium Hafnia alvei. This was accompanied by changes in proteolytic kinetics and in profiles of volatile aroma compounds and biogenic amine production. Finally, the development of the spoilage microorganism Pseudomonas fragi was significantly higher in the cheese with a reduced salt content.

Volatile compounds from fresh and dried mango were extracted by the solvent-assisted flavour evaporation (SAFE) technique and analysed by GC-MS. Forty-one and fifty five volatile compounds were identified in fresh and dried mango, respectively. Monoterpenes, followed by sesquiterpenes, lactones and alcohols were the major compounds. Drying induced substantial losses of several compounds. The total amount of volatiles decreased by about 59%. These losses could be mainly attributed to the evaporation of the volatiles during drying, the extent of which seemed to increase with the hydrophobicity and Henry's law constant of the compounds. However, new compounds appeared and enrichment of some compounds was observed after drying. Limonene, β-myrcene, δ-3-carene, β-caryophyllene, γ-butyrolactone and 3-methylbutyl butanoate were found to be flavour contributors in both products on the basis of the odour activity values (OAVs). Mesifuran displayed high OAV only in fresh fruit while hexanal and heptanal only in dried mango. (Resume d'auteur)

The identification of infochemicals for parasitoid females is a critical issue in applied and fundamental parasitoid research. The olfactory location of host and its microhabitat by Fopius arisanus (Sonan, 1932) (Hymenoptera: Braconidae), an egg-pupal parasitoid of fruit flies (Diptera: Tephritidae), is investigated. Potential sources of volatiles are placed in opaque traps and tested in field cages, under seminatural conditions. Fopius arisanus females respond positively to synomones from mango leaves and from fruits belonging to many botanical families, including the nonhost plant strawberry. They prefer fruits infested by Tephritidae to uninfested ones but do not discriminate between fresh and old infestations. Fopius arisanus females are attracted by the odours of faeces of the tephritid fly Bactrocera zonata. They exhibit remote detection of a volatile kairomone coating the egg mass of all tested Tephritidae species but absent in the egg mass of the Muscidae Stomoxys calcitrans. All these infochemicals are volatile but only those emanating from fruit and from faeces are attractants perceived before landing. The relationships between this apparent generalist behaviour and the dietary specialization of F. arisanus are discussed, according to its ecology and behaviour in its natural environment. (Resume d'auteur)

The purpose of this study was to determine how water and microbial stages in post-harvest processing affect the volatile content of coffee. Following our aroma analysis carried out on green coffees, we turned our attention to roasted coffees. Coffees produced by three variants of the wet method, and by an ecological process, were compared after roasting. Three degrees of roasting were applied to gain a clearer picture of the differences in roasted coffee aromas by means of a volatile compound analysis. Changes in the post-harvest process actually led to aroma differences in roasted coffees, and with light roasting it was possible to more effectively distinguish between the four treatments based on aroma criteria. Coffee produced by the traditional wet method, with microbial stages, had a better aroma quality than coffee produced by the ecological method, which was purely mechanical. Moreover, in the microbial method, mucilage removal under water gave coffees with more fruity, floral and caramel notes, whereas dry mucilage removal gave more neutral coffees. These results confirmed the importance of microbial mucilage removal under water and tallied with the results of our previous study on green coffee. This work provides coffee producers and roasters with an insight into the volatile composition of roasted coffee depending on the post-harvest process used and degree of roasting applied. © 2007 Elsevier Inc. All rights reserved.