RESUMO
The yeasts, Saccharomyces pastorianus, are hybrids of Saccharomyces cerevisiae and Saccharomyces eubayanus and have acquired traits from the combined parental genomes such as ability to ferment a range of sugars at low temperatures and to produce aromatic flavour compounds, allowing for the production of lager beers with crisp, clean flavours. The polyploid strains are sterile and have reached an evolutionary bottleneck for genetic variation. Here we describe an accelerated evolution approach to obtain lager yeasts with enhanced flavour profiles. As the relative expression of orthologous alleles is a significant contributor to the transcriptome during fermentation, we aimed to induce genetic variation by altering the S. cerevisiae to S. eubayanus chromosome ratio. Aneuploidy was induced through the temporary inhibition of the cell's stress response and strains with increased production of aromatic amino acids via the Shikimate pathway were selected by resistance to amino acid analogues. Genomic changes such as gross chromosomal rearrangements, chromosome loss and chromosome gain were detected in the characterised mutants, as were single-nucleotide polymorphisms in ARO4, encoding for DAHP synthase, the catalytic enzyme in the first step of the Shikimate pathway. Transcriptome analysis confirmed the upregulation of genes encoding enzymes in the Ehrlich pathway and the concomitant increase in the production of higher alcohols and esters such as 2-phenylethanol, 2-phenylethyl acetate, tryptophol, and tyrosol. We propose that the polyploid nature of S. pastorianus genomes is an advantageous trait supporting opportunities for genetic alteration in otherwise sterile strains.
Assuntos
Álcool Feniletílico , Saccharomyces cerevisiae , 3-Desoxi-7-Fosfo-Heptulonato Sintase/genética , 3-Desoxi-7-Fosfo-Heptulonato Sintase/metabolismo , Aminoácidos/metabolismo , Aminoácidos Aromáticos/genética , Aminoácidos Aromáticos/metabolismo , Cerveja , Fermentação , Genoma Fúngico , Genômica , Macrolídeos , Álcool Feniletílico/metabolismo , Poliploidia , Saccharomyces , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Açúcares/metabolismoRESUMO
To differentiate white wines from Croatian indigenous varieties, volatile aroma compounds were isolated by headspace solid-phase microextraction (HS-SPME) and analyzed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOF-MS) and conventional one-dimensional GC-MS. The data obtained were subjected to uni- and multivariate statistical analysis. The extra separation ability of the GC×GC second dimension provided additional in-depth volatile profile information, with more than 1000 compounds detected, while 350 were identified or tentatively identified in total by both techniques, which allowed highly efficient differentiation. A hundred and sixty one compounds in total were significantly different across monovarietal wines. Monoterpenic compounds, especially α-terpineol, followed by limonene and linalool, emerged as the most powerful differentiators, although particular compounds from other chemical classes were also shown to have notable discriminating ability. In general, Skrlet wine was the most abundant in monoterpenes, Malvazija istarska was dominant in terms of fermentation esters concentration, Posip contained the highest levels of particular C13-norisoprenoids, benzenoids, acetates, and sulfur containing compounds, Kraljevina was characterized by the highest concentration of a tentatively identified terpene γ-dehydro-ar-himachalene, while Marastina wine did not have specific unambiguous markers. The presented approach could be practically applied to improve defining, understanding, managing, and marketing varietal typicity of monovarietal wines.
RESUMO
Shiraz wine volatomes from two Australian geographical indications (GIs), that is, Orange and Riverina, were compared using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Shiraz wines were made in triplicate from grapes harvested at two harvest dates from six vineyards in the two GIs. A total of 133 compounds showed a significant trend between wines from the cooler Orange GI and warmer Riverina. Compounds associated with wines from the cooler climate were grape-derived volatiles, such as monoterpenes, sesquiterpenes, green leaf volatiles, and some norisoprenoids. Fermentation-derived compounds, such as esters and S-containing compounds, showed no specific trend related to grape origin. In addition, wines could be also clearly separated according to the harvest date, irrespective of the climate, with C6 compounds, higher alcohol acetates, and other esters contributing utmost to the differentiation of samples, whereas terpenoids and norisoprenoids did not have an influence. This study demonstrated the plasticity of wine volatome related to grape origin and also the maturity level (harvest date), irrespective of climate.
Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Vitis/química , Compostos Orgânicos Voláteis/química , Vinho/análise , Austrália , Clima , Análise Discriminante , Frutas/química , Odorantes/análise , Terpenos/químicaRESUMO
Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCâ¯×â¯GC-TOF-MS) was combined with conventional mono-dimensional GC-MS to differentiate Croatian virgin olive oils (VOO) according to variety and geographical origin, based on the profile of volatile aroma compounds isolated by HS-SPME. More than 1000 compounds were detected after untargeted profiling and 256 were identified or tentatively identified, providing one of the most detailed profiles of volatile aroma compounds in VOO up to date. Among them, 131 volatile compounds were significantly different across monovarietal VOOs, while 60 were found useful for the discrimination according to geographical origin. Many major lipoxygenase and minor non-lipoxygenase-generated compounds were shown to have discriminating ability with respect to both factors. Multivariate statistical analysis extracted twenty-one volatile markers with the highest discriminant power for varietal differentiation. The approach reported may have practical application in better understanding, defining, managing, and communicating the varietal or geographical typicity of monovarietal VOOs.
Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Azeite de Oliva/química , Compostos Orgânicos Voláteis/química , Lipoxigenase , Odorantes , Azeite de Oliva/classificaçãoRESUMO
We carried out comprehensive mapping of volatile compounds in 70 wines, from 48 wineries and 6 vintages, representative of the two main production areas for Italian sparkling wines, by HS-SPME-GCxGC-TOF-MS and multivariate analysis. The final scope was to describe the metabolomics space of these wines, and to verify whether the grape cultivar signature, the pedoclimatic influence of the production area, and the complex technology were measurable in the final product. The wine chromatograms provided a wealth of information, with 1695 compounds being found. A large number of putative markers influenced by the cultivation area was observed. A subset of 196 biomarkers fully discriminated between the two types of sparkling wines investigated. Among the new compounds, safranal and α-isophorone were observed. We showed how correlation-based network analysis could be used as a tool to detect the differences in compound behaviour based on external/environmental influences.
Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Microextração em Fase Sólida/métodos , Vinho/análise , Cicloexenos , Itália , Espectrometria de Massas/métodos , Terpenos , Compostos Orgânicos Voláteis/análiseRESUMO
The Palearctic planthopper Hyalesthes obsoletus is the natural vector of the grapevine yellow disease Bois noir. Grapevine is an occasional host plant of this polyphagous planthopper. To deepen our knowledge of the role of plant volatile organic compounds for H. obsoletus host plant searching, we carried out behavioral, morphological, and electrophysiological studies. We tested the attraction of H. obsoletus to nettle, field bindweed, hedge bindweed, chaste tree, and grapevine by using a Y-shaped olfactometer. The results showed a significant attraction of male H. obsoletus to chaste tree, and of the females to nettle. Male H. obsoletus were repelled by odor from hedge bindweed. Ultrastructural studies of the antennae showed at least two types of olfactory sensilla at the antennal pedicel: plaque organs and trichoid sensilla. Volatile organic compounds from nettle and chaste tree were collected, and the extracts were analyzed by coupling gas-chromatography to both mass-spectrometry and electroantennography. The volatile organic compounds that elicited electrophysiological responses in male and female antennae were identified. These findings are discussed with respect to behavior of H. obsoletus males and females in the field.
Assuntos
Hemípteros/fisiologia , Compostos Orgânicos Voláteis/farmacologia , Animais , Comportamento Animal/efeitos dos fármacos , Calystegia/química , Convolvulus/química , Fenômenos Eletrofisiológicos , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Hemípteros/efeitos dos fármacos , Masculino , Odorantes , Percepção , Urtica dioica/química , Vitex/química , Vitis/química , Compostos Orgânicos Voláteis/químicaRESUMO
A headspace SPME GC-TOF-MS method was developed for the acquisition of metabolite profiles of apple volatiles. As a first step, an experimental design was applied to find out the most appropriate conditions for the extraction of apple volatile compounds by SPME. The selected SPME method was applied in profiling of four different apple varieties by GC-EI-TOF-MS. Full scan GC-MS data were processed by MarkerLynx software for peak picking, normalisation, alignment and feature extraction. Advanced chemometric/statistical techniques (PCA and PLS-DA) were used to explore data and extract useful information. Characteristic markers of each variety were successively identified using the NIST library thus providing useful information for variety classification. The developed HS-SPME sampling method is fully automated and proved useful in obtaining the fingerprint of the volatile content of the fruit. The described analytical protocol can aid in further studies of the apple metabolome.
Assuntos
Cromatografia Gasosa-Espectrometria de Massas/métodos , Malus/química , Microextração em Fase Sólida/métodos , Compostos Orgânicos Voláteis/análise , Liofilização , Malus/metabolismo , Metaboloma , Metabolômica/métodos , Análise de Componente Principal , TemperaturaRESUMO
The volatile compounds emitted by two raspberry varieties ( Rubus idaeus , cv. Polka and Tulameen) were analyzed, in both the case of fresh fruits and juices, by two headspace methods that are rapid, solvent-free, and with reduced or no sample pretreatment: solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) and proton-transfer reaction-mass spectrometry (PTR-MS). Multivariate analysis of the SPME/GC-MS results allows for an unambiguous sample discrimination for both mashed fruits and juices. PTR-MS instrumental fingerprint provides, in a faster way, similar qualitative information on the overall flavor profile. The two cultivars show both qualitative and quantitative differences. SPME/GC-MS analysis shows that alcohols and aldehydes are more abundant in the headspace of Tulameen as, e.g., hexanal and hexanol that induce herbaceous odor notes. This observation has been confirmed by sensory analysis. PTR-MS was also used to monitor rapid processes that modify the original aromatic profile, such as lipo-oxigenase activity induced by tissue damages occurring during industrial transformation, accidental mechanical damages, or as a consequence of chewing.
Assuntos
Frutas/química , Cromatografia Gasosa-Espectrometria de Massas/métodos , Espectrometria de Massas/métodos , Rosaceae/química , Microextração em Fase Sólida/métodos , Compostos Orgânicos Voláteis/análise , Álcoois/análise , Aldeídos/análise , Bebidas/análise , Humanos , Olfato , Especificidade da Espécie , PaladarRESUMO
The gastronomic relevance and high price of white truffle are related mainly to its unique aroma. Here we evaluate, for the first time, the possibility of characterizing in a rapid and non-destructive way the aroma of white truffles based on proton transfer reaction mass spectrometry (PTR-MS). We indicate that anonymous PTR-MS fingerprinting allows sample classification and we also compare qualitatively and quantitatively PTR-MS data with measurements made by solid-phase microextraction gas chromatography (SPME-GC) of the same samples under the same conditions. PTR-MS fragmentation data of truffle-relevant compounds are also published here for the first time. Most of the sulfur-containing compounds detected by GC and relevant for white truffle aroma have a high positive correlation with single PTR-MS peaks. Our work indicates that, after preliminary comparison with GC data, PTR-MS is a new tool for the rapid, quantitative and non-invasive characterization of white truffle by direct headspace injection without any pre-concentration.