Search results for "Organo"
showing 10 items of 1460 documents
Aroma compounds in wine as influenced by apiculate yeasts
1996
Aroma compounds of wines resulting from fermentation of sterile grape musts from Monastrell variety inoculated with pure and mixed cultures of apiculate and Saccharomyces yeasts, were isolated and analyzed by gas chromatography with flame ionization and mass spectrometry. Samples fermented with mixed cultures produced a higher concentration of selected compounds and higher total amounts of alcohols and acids, in contrast with wines produced with pure cultures of Saccharomyces spp. Apiculate yeasts are important in the chemical composition and quality of wine.
Saccharomyces Yeasts I
2011
Publisher Summary This chapter discusses the microbiological aspects of saccharomyces yeasts in wine production. Yeasts, which play a central role in the winemaking process, are unicellular fungi that reproduce by budding. Most yeast belongs to the phylum Ascomycota on the basis of their sexual development. The selection of wine yeasts with specific genetic markers provides a system for the precise monitoring of the growth of particular strains during fermentation. Analyses of this type have shown that fermentation is driven mainly by inoculated yeasts, although these sometimes become only partially established. The growth of the natural flora is not completely suppressed during the initial…
The chemodiversity of wines can reveal a metabologeography expression of cooperage oak wood
2009
Wine chemical compositions, which result from a complex interplay between environmental factors, genetic factors, and viticultural practices, have mostly been studied using targeted analyses of selected families of metabolites. Detailed studies have particularly concerned volatile and polyphenolic compounds because of their acknowledged roles in the organoleptic and therapeutic properties. However, we show that an unprecedented chemical diversity of wine composition can be unraveled through a nontargeted approach by ultrahigh-resolution mass spectrometry, which provides an instantaneous image of complex interacting processes, not easily or possibly resolvable into their unambiguous individu…
Influence of Soil Salinity on Sensory Characteristics and Volatile Aroma Compounds of Nero d’Avola Wine
2010
The influence of soil salinity on the chemical composition, volatile aromatic compounds, and sensory characteristics of Nero d'Avola wine was examined. Data on vineyard productivity, such as grape yield, are also reported. Physicochemical parameters were determined on the samples analyzed. Solid-phase microextraction was used for the extraction of aromatic volatile compounds, followed by capillary gas chromatography-mass spectrometry. Sensory analyses were performed by visual inspection, smelling, and tasting. Statistical analysis showed that most of the physicochemical parameters and volatile constituents, both primary and fermentation aromas, were influenced by the soil salinity. The comp…
(−)Geosmin sorption by enological yeasts in model wine and FTIR spectroscopy characterization of the sorbent
2010
Abstract For the first time, we report that enological yeasts or yeast cell walls can sorb (−)geosmin, an undesirable molecule that causes critical organoleptic defects in wine at low concentrations (around 50 ng l −1 ). The wine is described as “earthy” or “mouldy”. The influence of various post-harvesting processes on yeast (−)geosmin sorption capacity was studied. The dried yeast biomass obtained by the different processes was analysed by FTIR spectroscopy in ATR mode: structural differences were detected between the samples depending on the strain and the treatment used. Surface proteins and mainly phospholipids from the plasma membrane appeared to induce significantly different signals…
Malolactic fermentation in white wines
2022
Abstract Malolactic fermentation (MLF) is an important process in wine production and involves the bioconversion of malic acid into lactic acid and CO2. However, many other biochemical reactions occur simultaneously, and several other grape must and wine compounds are also modified besides malic acid. Some can improve quality, while others may be detrimental to sensory quality or health. Among them, there are the synthesis of carbonyl compounds, esters, monoterpenes, volatile phenols, acetamide or mousy odor, methanethiol, dimethyl disulfide, methionol, 3-(methylsulfanyl) propionic acid, citrulline, or biogenic amines. The role of MLF in winemaking is triple: reducing the acidity of the win…
Preparation and XAFS studies of organotin(IV) complexes with adenosine and related compounds and calf thymus DNA
2007
Complexes of adenosine and related compounds (adenosine-5’-monophosphate, adenosine-5’-triphosphate and pyridoxal-5-phosphate) with Bu2SnO and/or BuSnCl2 were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain the organotin(IV) moiety and the ligand in a ratio of 1:1. The FT-IR spectra demonstrated that Bu2SnO reacts with the D-ribose moiety of the ligands, while Bu2SnCl2 is coordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mossbauer Δ (quadrupole splitting) values with those calcul…
Comparative Experimental and Theoretical Study of the Fe L-2,L-3-Edges X-ray Absorption Spectroscopy in Three Highly Popular, Low-Spin Organoiron Com…
2019
The occupied and unoccupied electronic structures of three highly popular, closed shell organoiron complexes ([Fe(CO)(5)], [(eta(5)-C5H5 )Fe(CO)(mu-CO)](2), and [(eta(5)-C5H5)(2)Fe]) have been theoretically investigated by taking advantage of density functional theory (DFT) calculations coupled to the isolobal analogy (Elian et al. Inorg. Chem. 1976, 15, 1148). The adopted approach allowed us to look into the relative role played by the ligand -> Fe donation and the Fe -> ligand back-donation in title molecules, as well as to investigate how CO- (terminal or bridging) and [(eta(5)-C5H5)](-)-based pi* orbitals compete when these two ligands are simultaneously present as in [(eta(5)-C5H…
Sulfur Dioxide Oxidation Catalyzed by Photosensitized Ytterbium Diphthalocyanine
2008
Oxidation of SO2 into SO3 was found effectively catalyzed by photosensitized ytterbium diphthalocyanine, YbPc2 (Pc = phthalocyanine ligand, C32H16N8) when performed in air-saturated dimethylformamide (DMF) solution at 20 °C. The process follows according to a multi-step complex mechanism involving chemical induction as its driving force. Excitation energy of the sandwich molecular system in YbPc2 is used to promote the reaction by creating a reactive intermediate form of the ytterbium complex hosting up to eight SO2 molecules. The conversion of SO2 proved complete.
Zirconium & Hafnium: Organometallic ChemistryBased in part on the article Zirconium & Hafnium: Organometallic Chemistry by Bernard Gautheron,…
2006
This review considers the main aspects of organometallic chemistry of zirconium and hafnium during the last 10 years. It is complementary to the first edition of Encyclopedia of Inorganic Chemistry. The material is presented in two major parts divided in five and three sections respectively. The first part is devoted to syntheses: the first section, by far the largest, covers in a systematic manner bis and mono cyclopentadienyl complexes with +4, +3, and +2 oxidation states and more especially constrained-geometry (CG) complexes, cationic complexes, and anionic or zwitterionic 18-electron complexes; unusual coordination geometries at carbon stabilized by group 4 metallocenes are presented i…