Lara Tat

University of Udine, Udine, Friuli Venezia Giulia, Italy

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Publications (9)12.66 Total impact

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    ABSTRACT: The effects of three preparation techniques on the oenological properties of a yeast autolysate were investigated: enzymatic autolysis, thermolysis, and the combination of a slow freezing-defrosting and mechanical disruption were carried out on a commercial formulation of active dry yeasts (Saccharomyces cerevisiae). The powders obtained by freeze drying, were characterized: volatile compounds were analyzed by SPME-GC with mass spectrometric (MS) and olfactometric detection (O); the release of colloids in winelike solution was studied by SDS-PAGE and size exclusion chromatography (SEC). Finally, the effects of the powders addition on the aroma composition of a white wine were investigated by SPME-GC-MS, SPME-GC-O, and sensory evaluation. The products obtained were quite different from each other. In particular, enzymatic autolysis led to higher contents of nonglycosilated soluble proteins in the powders and determined a higher retention of wine aroma compounds. On the contrary, thermal autolysate was richer in glycoproteins, and it was able to increase the wine aroma intensity; nevertheless, in the wines treated with such preparation, a slight yeastlike olfactory note was perceived.
    Journal of Agricultural and Food Chemistry 03/2012; 60(12):3211-22. · 3.11 Impact Factor
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    ABSTRACT: The addition of a commercial yeast autolysate to a model solution of five typical wine aroma compounds (ethyl octanoate, linalool, 2-phenylethanol, β-ionone and octanoic acid) was investigated considering different variables, such as temperature, pH and the presence of highly concentrated natural volatile substances in wine (e.g. 3-methyl-1-butanol). The interactions of such compounds with both yeast walls and released colloids were studied using gas chromatography, with liquid-liquid extraction and solid-phase microextraction. The results were compared with those obtained by adding the commercial product to a white table wine, spiked with the five standard compounds. The data confirmed that yeast walls mainly bind less polar molecules: their loss in synthetic medium seemed to increase at higher pH values. Temperature and pH affected differently the interactions between yeast colloids and volatile compounds in wine and model solution: in complex solutions (as the addition of 3-methyl-1-butanol demonstrated) the interaction mechanisms could be influenced by competitive or other matrix-related effects, which can reduce the binding of single compounds, or even enhance their volatility.
    Food Chemistry 07/2011; 127(2):473-80. · 3.33 Impact Factor
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    ABSTRACT: Some modifications to a previous nondestructive colorimetric method that permits evaluation of the oxygen diffusion rate through wine closures were proposed. The method is based on the reaction of indigo carmine solution with oxygen and the tristimulus measurement of the consequent color change. Simplified preparation and measurement procedures were set up, allowing the analysis of a large number of samples simultaneously. The method was applied to the evaluation of the variability within the lot of 20 different types of stoppers (synthetic, produced by molding, and natural cork). The closures were tested at a storage temperature of 26 degrees C. With regard to oxygen permeability, the natural cork stopper showed a low homogeneity within the lot, especially during the first month after bottling, whereas the synthetic closure showed a greater steadiness in the performance. The limits of the colorimetric method were also analyzed, and three possible causes of degradation of the indigo carmine solution were identified: oxygen, light, and heat.
    Journal of Agricultural and Food Chemistry 02/2010; 58(6):3567-72. · 3.11 Impact Factor
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    ABSTRACT: Interest in high-quality and peculiar products is a recent trend in the enological field; for this reason, production of wines from autochthonous vine varieties is requested by consumers. Aglianico wine from the Italian region "Basilicata" is an example of a promising product strictly connected to the territory; nevertheless, it is affected by a frequent sweet-like off-flavor. In this study the compositional cause of this off-flavor was investigated by SPME-GC-olfactometry, SPME-GC-MS, and sensory tests. Ethyl phenylacetate (EPhA) was found to be the compound mainly responsible, and its sensory threshold was determined near 73 microg/L; products with the odorant concentration near and up to these values were always recognized as significantly different from the other wines and were often far from wine technical pleasantness; besides EPhA gave to the wines a strong honey-like character. Some preliminary hypotheses about its mechanism of formation (shikimate pathway) are presented in this study: these hypotheses could explain the correlation between EPhA and volatile phenols that was found by both sensory tests and GC quantitative analysis of wines affected by different levels of defect.
    Journal of Agricultural and Food Chemistry 07/2007; 55(13):5205-12. · 3.11 Impact Factor
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    ABSTRACT: A qualitative study of volatile compounds in three commercial yeast extracts and autolysates was performed by solid-phase microextraction-gas chromatography with mass spectrometric and olfactometric detection; their addition to white wines and their effect on wine aroma composition were investigated by analytical, olfactometric and sensory evaluations. More than 160 volatile compounds were detected in the headspace of the commercial powders (some not previously reported in literature), and their olfactory characters were described. Yeast derivatives strongly modified wine aroma composition, either affecting the volatility of wine aroma compounds or by releasing exogenous volatiles. Dosage appeared to be fundamental: low amounts increased the volatility of some esters, giving more flowery and fruity notes to the wine; higher amounts increased fatty acid content in the wine headspace, producing yeasty, herbaceous and cheese-like smells. Sensory tests demonstrated that yeast derivatives would not be suitable for wines with a typical varietal aroma.
    Food Chemistry. 01/2006;
  • Roberto Zironi, Lara Tat
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    ABSTRACT: Durante mucho tiempo, la producción italiana de espumosos, los reconocidos como spumanti, ha sido considerada como un pariente pobre del más noble y renombrado champán francés. En los últimos años se observa una importante revalorización de la «tradición nacional» en este sector, gracias al descubrimiento, en este producto, de aquellos perfumes y aromas característicos de las diversas zonas de producción que tanto atraen al consumidor. Y es que, además de los espumosos, Italia cuenta con una remarcable producción de vinos frisantes o de aguja, que se diferencian de los primeros por la cantidad de anhídrido carbónico que contienen.
    ACE: Revista de enología, ISSN 1697-4123, Nº. 59, 2005. 01/2005;
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    ABSTRACT: Different novel fibers for solid-phase microextraction were developed in the last years. The aims of this work were the study of their performances in wine headspace analysis, and the optimization of some analytical conditions. The fibers were evaluated for their sensitivity and repeatability; the results showed a strongly different behavior for the different solid-phases, both for the different zones of the chromatogram and for different levels of concentration. A Divinylbenzene/Carboxen/Polydimethylsiloxane fiber coating appeared the most suitable for the analysis of aromatic fraction of wines in its totality. For specific applications, the choice of a suitable solid-phase, depends on the class of compounds be analyzed.
    Food Chemistry. 01/2005;
  • Sciences Des Aliments - SCI ALIMENT. 01/2004; 24(5):371-382.