Role of Strecker aldehydes on beer flavour stability

In this work, attempts were made in order to measure the importance of “Strecker aldehydes” on flavour stability of beer correlating chemical and sensory data. It has been observed that methional and phenylacetaldehyde accumulates during storage and that these molecules were well correlated with “Aroma Quality”. A “fresh beer” was spiked with methional, phenylacetaldehyde and also with trans-2-nonenal, singly and in combination, the “Similarity Value” was then determined, between samples and an “aged beer”. The highest value was 72 % when the three compounds were added simultaneously and the combination of the two Strecker aldehydes increases by 54 % the degree of similarity

Volatile sulphur compounds in wines related to yeast metabolism and nitrogen composition of grape musts

The influence of nitrogen compounds in grape musts on the content of sulphur compounds of wines was studied. Different vinifications were performed with the addition of methionine (20 mg l−1) and/or cysteine (40 mg l−1) to grape musts before alcoholic fermentation. Six grape musts, with different nitrogen composition, from cultivars of the ‘Vinhos Verdes’ Region, in Portugal, were used. Addition of methionine to grape musts enhanced the content of wines in 3-(methylthio)-1-propanol, acetic acid-3-(methylthio)propyl ester, 3-(methylthio)propionic acid and some unidentified sulphur compounds. Increase of cysteine concentration in musts led to the production of wines with high levels of hydrogen sulphide and cis-2-methyltetrahydrothiophene- 3-OL and also unidentified sulphur compounds; however, the content of 3-(methylthio)propionic acid in the wines decreased considerately with the addition of cysteine to grape musts. This work showed that cultivars from the Vinho Verde Region show different sulphur compound contents. Avesso wines, elaborated from grape musts with low amino acids level, presented the highest total sulphur compounds content. Wines from Azal branco and Alvarinho were characterised by high contents of 4-(methylthio)-1-butanol and 3-(methylthio)propionic acid, respectively. A high content of N-(3-(methylthio) propyl)-acetamide and dimethylsulphone characterise the Loureiro wines. In contrast, Trajadura wines, produced from a must rich in amino acids, presented a low total sulphur compounds content; however, these wines were also characterised by high concentrations of 4-(methylthio)-1-butanol, acetic acid-3-(methylthio)propyl ester and hydrogen sulphide

Fatty acid composition of wild edible mushrooms species: a comparative study

A comparative study was developed on the total fatty acids composition of twelve wild edible mushroom species (Suillus bellini, Suillus luteus, Suillus granulatus, Hygrophorus agathosmus, Amanita rubescens, Russula cyanoxantha, Boletus edulis, Tricholoma equestre, Fistulina hepatica, Cantharellus cibarius, Amanita caesarea and Hydnum rufescens). In order to define qualitative and quantitative profiles, combined fatty acids were hydrolyzed with potassium hydroxide/methanol and all free compounds were derived to their methyl ester forms with methanolic boron trifluoride, followed by analysis by GC-MS. Thirty fatty acids were determined. As far as we know, the fatty acid profiles of A. caesarea and H. rufescens are described for the first time. As for the remaining species, a high number of new compounds were identified, which much improved the knowledge about their fatty acids profiles. In general, oleic, linoleic, palmitic and stearic acids were present in highest contents. Polyunsaturated and monounsaturated fatty acids, valuable healthy compounds for humans, predominated over saturated fatty acids for all the studied mushroom species. R. cyanoxantha presented the highest fatty acids amounts, while B. edulis was the poorest species. By Agglomerative Hierarchic Cluster Analysis the studied species were gathered in 5 groups, based in their fatty acid patternsFundação para a Ciência e a Tecnologia (FCT) for a grant (SFRH/BD/22108/2005)

Antimicrobial activity of endophytic fungi from olive tree leaves

In this study, the antimicrobial potential of three fungal endophytes from leaves of Olea europaea L. was evaluated and the host plant extract effect in the antimicrobial activity was examined. The volatile compounds produced by endophytes were identified by GC/MS and further correlated with the antimicrobial activity. In potato dextrose agar, both Penicillium commune and Penicillium canescens were the most effective inhibiting Gram-positive and -negative bacteria (up to 2.7-fold compared to 30 µg/mL chloramphenicol), whereas Alternaria alternata was most effective inhibiting yeasts (up to 8.0-fold compared to 25 μg/mL fluconazole). The presence of aqueous leaf extract in culture medium showed to induce or repress the antimicrobial activity, depending on the endophytic species. In the next step, various organic extracts from both A. alternata mycelium and cultured broth we re prepared; being ethyl acetate extracts displayed the widest spectrum of anti-microorganisms at a minimum inhibitory concentration ≤0.095 mg/mL. The volatile composition of the fungi that displayed the highest (A. alternata) and the lowest (P. canescens) antimicrobial activity against yeasts revealed the presence of six volatiles, being the most abundant components (3-methyl-1-butanol and phenylethyl alcohol) ascribed with antimicrobial potentialities. Overall the results highlighted for the first time the antimicrobial potential of endophytic fungi from O. europaea and the possibility to be exploited for their antimicrobial agents. Graphical Abstract: [Figure not available: see fulltext.]This work is funded by FEDER funds through COMPETE (Programa Operacional Factores de Competitividade) and by national funds by FCT (Fundação para a Ciência e a Tecnologia) in the framework of the project “EndoBio—Isolation and screening of endophytic fungi for biological control of olive against Colletotrichum acutatum and Verticillium dahliae” (PTDC/ AGR-PRO/4354/2012).info:eu-repo/semantics/publishedVersio

Interaction between Hypholoma fasciculare and the ectomycorrhizal fungus Pisolithus tinctorius

In the past few years, cord-forming basidiomycetes have received considerable attention in their growth strategies in the presence of other fungi (saprotrophic and pathogenic). In the present study, the in vitro interaction between the cord-forming basidiomycete Hypholoma fasciculare and the ectomycorrhizal fungus Pisolithus tinctorius was studied. Dual-cultures were established and the radial fungal growth, hyphae morphology and production of volatile compounds were evaluated during interaction. Growth of P. tinctorius is severely inhibited by H. fasciculare even before mycelia contact, suggesting a mechanism of antagonism at a distance. Following contact with H. fasciculare mycelia, P. tinctorius displayed distinctive hyphal interference with collapsed or atypical hyphae. Alteration in the production of volatile compounds, distributed in several chemical classes (alcohols, ketones, aldehydes, terpenes, among others) was also detected over the time course of interaction. Sesquiterpenes compounds with putative antifungal properties were the most abundant before fungal contact and their possible role during interaction will be discussed

Systemic release of volatiles by Brassica oleracea var. acephala induced by Pieris brassicae predation.

Pieris brassicae is a specialist on crucifers and its interactions with some of its host plants have been increasingly studied given their importance in pest management, chemical ecology and entomology. Plants are known to respond to insect attack by releasing volatiles that can either warn neighbour plants to the presence of a predator or attract insect parasitoids, thus reducing the attack efficiency. The influence of P. brassicae feeding on Brassica oleracea L. var. acephala (kale) was investigated, namely, its effect in the volatiles released by the plant through time. Substantial differences, mainly quantitative, were found between the volatiles composition of B. oleracea var. acephala before the attack and after insect feeding. More than 40 compounds were found, between terpenes (monoterpenes and sesquiterpenes) and lipoxygenase pathway byproducts (alcohols and aldehydes), ketones, norisoprenoids, among others. After insect attack, monoterpenes like limonene, eucalyptol, camphor and caryophyllene increased noticeably. These compounds have been regarded as markers in local tissue responses and in this study an increase in their concentration was detected at 1 and 4 hours after feeding, with subsequent reduction after 8 hours. Menthol, menthone, phenol and sabinene were found only in the time following the attack. A considerable increase in hexenyl acetate, a well known semiochemical, was also found, with this compound being the major peak in all experiments, rising with time. These findings provide further knowledge of the ecological interactions between these two species and, given the chemical diversity of these matrices, they may constitute a good source of health promoting compounds.Fundação para a Ciência e Tecnologia for financial support (PTDC/AGRAAM/ 64150/2006). F. Fernandes (SFRH/BD/37963/2007

Mitochondrial dynamics and quality control in Huntington's disease

Huntington's disease (HD) is an inherited neurodegenerative disorder caused by polyglutamine expansion mutations in the huntingtin protein. Despite its ubiquitous distribution, expression of mutant huntingtin (mHtt) is particularly detrimental to medium spiny neurons within the striatum. Mitochondrial dysfunction has been associated with HD pathogenesis. Here we review the current evidence for mHtt-induced abnormalities in mitochondrial dynamics and quality control, with a particular focus on brain and neuronal data pertaining to striatal vulnerability. We address mHtt effects on mitochondrial biogenesis, protein import, complex assembly, fission and fusion, mitochondrial transport, and on the degradation of damaged mitochondria via autophagy (mitophagy). For an integrated perspective on potentially converging pathogenic mechanisms, we also address impaired autophagosomal transport and abnormal mHtt proteostasis in HD

Metabolic fate of dietary volatile compounds in Pieris brassicae

In this work, the evolution of the qualitative and quantitative profile of the volatile fraction of Pieris brassicae after feeding on Brassica oleracea var. acephala (kale) was monitored through time. HS-SPME/GC-MS was applied to both the host plant and the living insect and its excrements. A total of seventy seven compounds (lipoxygenase pathway by-products, nitrogen compounds, norisoprenoids, sulphur compounds, terpenes, among others) were identified. Thirty eight compounds were identified in insect after 2 h of starvation and forty eight compounds in excrements. Qualitative and quantitative changes were detected along time. Dimethyldisulfide, dimethyltrisulfide, limonene and eugenol were major compounds for all analysed times in both matrices, being limonene an important compound in insect after starvation. The accumulation by P. brassicae of some compounds, such as limonene, was verified, suggesting a mechanism by which the insect can take benefit from bioactive constituents from the diet. Along with accumulation, complete excretion of some compounds, including nitrogen bearing compounds, by-products of glucosinolates was detected. These results reflect one of the strategies used to overcome plant barriers, namely detoxification of toxic compounds. The findings contribute to the knowledge of the metabolization of the volatile compounds in insects and contribute to the body of knowledge of this ecologic system.FC