R Sanz

University of Barcelona, Barcelona, Catalonia, Spain

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Publications (11)35.04 Total impact

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    ABSTRACT: The quality of wine greatly depends on the features of the yeast used in its production, and yeast cell viability is one of the most important quality control issues to consider in this regard. In the first steps of winemaking, the use of a low-cost and simple methodology for monitoring the cell viability of yeast inoculates is of paramount importance. Gravitational field-flow fractionation is a useful technique for the determination of cell viability because it provides gentle experimental conditions, although the proper use of fluorophore probes as biomass indicators is required. In this paper the use of different fluorescent probes such as carboxyfluorescein diacetate (cFDA), calcein-AM, and SYTO-13 were considered as viability biomarkers. Calceina-AM allowed the establishment of a direct GrFFF method to determine cell viability, with a limit of detection of 5.0 x 10(4) viable cell/mL. SYTO-13 could be used as biomass indicator with a limit of detection of 3.5 x 10(4) total cells/mL. The suitability of the procedure was tested with three commercial yeast samples, and the results were compared with those obtained using standard techniques.
    Biotechnology Progress 01/2006; 22(3):847-52. · 1.85 Impact Factor
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    ABSTRACT: Yeasts are widely used in several areas of food industry, e.g. baking, beer brewing, and wine production. Interest in new analytical methods for quality control and characterization of yeast cells is thus increasing. The biophysical properties of yeast cells, among which cell size, are related to yeast cell capabilities to produce primary and secondary metabolites during the fermentation process. Biophysical properties of winemaking yeast strains can be screened by field-flow fractionation (FFF). In this work we present the use of flow FFF (FlFFF) with turbidimetric multi-wavelength detection for the number-size distribution analysis of different commercial winemaking yeast varieties. The use of a diode-array detector allows to apply to dispersed samples like yeast cells the recently developed method for number-size (or mass-size) analysis in flow-assisted separation techniques. Results for six commercial winemaking yeast strains are compared with data obtained by a standard method for cell sizing (Coulter counter). The method here proposed gives, at short analysis time, accurate information on the number of cells of a given size, and information on the total number of cells.
    Journal of Chromatography A 11/2004; 1054(1-2):293-301. · 4.61 Impact Factor
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    ABSTRACT: This work continues the project on field-flow fractionation characterisation of whole wine-making yeast cells reported in previous papers. When yeast cells are fractionated by gravitational field-flow fractionation and cell sizing of the collected fractions is achieved by the electrosensing zone technique (Coulter counter), it is shown that yeast cell retention depends on differences between physical indexes of yeast cells other than size. Scanning electron microscopy on collected fractions actually shows co-elution of yeast cells of different size and shape. Otherwise, the observed agreement between the particle size distribution analysis obtained by means of the Coulter counter and by flow field-flow fractionation, which employs a second mobile phase flow as applied field instead of Earth's gravity, indicates that yeast cell density can play a major role in the gravitational field-flow fractionation retention mechanism of yeast cells, in which flow field-flow fractionation retention is independent of particle density. Flow field-flow fractionation is then coupled off-line to gravitational field-flow fractionation for more accurate characterisation of the doubly-fractionated cells. Coupling gravitational and flow field-flow fractionation eventually furnishes more information on the multipolydispersity indexes of yeast cells, in particular on their shape and density polydispersity.
    Analytical and Bioanalytical Chemistry 09/2004; 379(7-8):1068-75. · 3.66 Impact Factor
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    ABSTRACT: Membraneless hyperlayer flow field-flow fractionation (Hyp FIFFF) has shown improved performance with respect to Hyp FIFFF with membrane. The conditions for high recovery and recovery independent of sample loading in membraneless Hyp FIFFF have been previously determined. The effect of sample loading should be also investigated in order to optimize the form of the peaks for real samples. The effect of sample loading on peak retention parameters is of prime importance in applications such as the conversion of peaks into particle size distributions. In this paper, a systematic experimental work is performed in order to study the effect of sample loading on retention parameters. A procedure to regenerate the frit operating as accumulation wall is described. High reproducibility is obtained with low system conditioning time.
    Annali di Chimica 04/2004; 94(3):197-206. · 0.99 Impact Factor
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    ABSTRACT: Vinification processing is largely related to yeast performance and depends on the initial cell viability. To optimize the quality of wine fermentation, control of the yeast quality is mandatory. The present paper describes a new method using gravitational field flow fractionation (GrFFF) with fluorescence detection for the determination of yeast cell viability before the fermentation process. A GrFFF calibration procedure was developed using commercial yeast to prepare standards of viable cells and propidium iodide (PI) as fluorescent probe for nonviable cells. The suitability of the new method was tested with several commercial yeast strains with a g/L content ranging from 1 to 3. The validation of the method was performed by comparing GrFFF viability values with those obtained using Coulter counter and flow cytometry techniques.
    Biotechnology Progress 01/2004; 20(2):613-8. · 1.85 Impact Factor
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    ABSTRACT: Sonication procedures are generally used prior to field flow fractionation (FFF) separation in order to produce suspensions without aggregates. Yeast cells manufactured in active dry wine yeast (ADWY) were placed in an ultrasound water bath in order to disrupt possible clumps and to obtain a single-cell suspension to be used in optimal conditions during fermentation processes. In order to determine whether this sample preparation procedure meets absolute needs, different yeast samples before and after sonication were analysed by two field flow fractionation techniques. It is shown that 2 min of sonication in the sample preparation process is sufficient to obtain an optimal dispersion of the yeast cells, that is, without critical percentage of aggregates. To demonstrate this effect, photographs of the yeast cell suspensions were performed with non-sonicated and sonicated yeast sample dispersion. The resulting data are compared with the elution profiles obtained from the two different FFF techniques. It is demonstrated that fractogram profiles prove the effectiveness of sonication methodologies.
    Journal of Chromatography A 07/2003; 1002(1-2):145-54. · 4.61 Impact Factor
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    ABSTRACT: Important oenological properties of wine depend on the winemaking yeast used in the fermentation process. There is considerable controversy about the quality of yeast, and a simple and cheap analytical methodology for quality control of yeast is needed. Gravitational field flow fractionation (GFFF) was used to characterize several commercial active dry wine yeasts from Saccharomyces cerevisiae and Saccharomyces bayanus and to assess the quality of the raw material before use. Laboratory-scale fermentations were performed using two different S. cerevisiae strains as inocula, and GFFF was used to follow the behavior of yeast cells during alcoholic fermentation. The viable/nonviable cell ratio was obtained by flow cytometry (FC) using propidium iodide as fluorescent dye. In each experiment, the amount of dry wine yeast to be used was calculated in order to provide the same quantity of viable cells. Kinetic studies of the fermentation process were performed controlling the density of the must, from 1.071 to 0.989 (20/20 density), and the total residual sugars, from 170 to 3 g/L. During the wine fermentation process, differences in the peak profiles obtained by GFFF between the two types of commercial yeasts that can be related with the unlike cell growth were observed. Moreover, the strains showed different fermentation kinetic profiles that could be correlated with the corresponding fractograms monitored by GFFF. These results allow optimism that sedimentation FFF techniques could be successfully used for quality assessment of the raw material and to predict yeast behavior during yeast-based bioprocesses such as wine production.
    Biotechnology Progress 01/2003; 19(6):1786-91. · 1.85 Impact Factor
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    ABSTRACT: Sedimentation field flow fractionation separation associated with flow cytometry has been used for the characterization of several commercial Saccharomyces cerevisiae yeasts used for wine production. A new type of channel 80 microm thick and new operating conditions, such as sample introduction when field and flow are established and a channel inlet connected to the accumulation wall, were used. Good repeatability (5% RSD) and reduced analysis time (2-10 min) were obtained. The avoidance of the stop-flow relaxation process in conjunction with the use of a channel of reduced thickness has demonstrated that an effective "steric-hyperlayer" mode driving to a major focusing effect of the species in the channel thickness is involved in the elution of the yeast cells. Flow cytometry analyses were performed, and the forward scattering and side scattering yeast characteristics correlation maps were obtained. Field flow fractionation and flow cytometry information obtained indicated that the fractogram profiles of the yeast cell depended not only on the size, but also on the shape and density.
    Analytical Chemistry 10/2002; 74(17):4496-504. · 5.82 Impact Factor
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    ABSTRACT: Performance of gravitational field-flow fractionation (GFFF) is improved here with respect to the ability to fractionate and distinguish different varieties of wine-making yeast from Saccharomyces cerevisiae. A new GFFF channel with non-polar walls has been employed to enhance fractionation selectivity and reproducibility. Since GFFF retention depends from first principles on particle size, Coulter counter measurements were performed in order to compare size distribution profiles with GFFF profiles. From such a comparison, GFFF was shown to be able to reveal differences in yeast cells other than size. This could make use of GFFF for screening different varieties of wine-making yeast towards future quality assessment procedures based on a possible correlation between yeast cell morphology indexes and quality indexes.
    Journal of Chromatography A 09/2002; 966(1-2):135-43. · 4.61 Impact Factor
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    ABSTRACT: Steric/hyperlayer flow field-flow fractionation (St/Hyp/FlFFF) is suitable for the separation and characterization of micrometer-sized particles. In this technique, an ultrafiltration membrane is commonly used as the surface of the accumulation wall. St/ Hyp/FlFFF has been recently tested in membraneless mode and an improvement in performance was found. Recovery was also improved and second-order effects were reduced.In the framework of St/Hyp/FlFFF optimization, the effect of sample loading is a problem of a certain importance. For quantitative purposes, the conversion of peaks into mass particle size distributions is of prime importance and, therefore, the conditions in which there is no effect of sample loading on recovery should be investigated.In this paper, systematic work was performed in order to study the effect of sample loading on recovery. We have found the conditions in which recovery is independent of sample loading. For these conditions, the limit of detection for various micrometer-size standard polystyrene particles was calculated. The absolute sample recovery was calculated by applying a quantitative method for single-run analysis in FFF with UV/Vis detectors.
    Journal of Liquid Chromatography &amp Related Technologies 01/2002; 25(13-15):2211-2224. · 0.57 Impact Factor
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    ABSTRACT: Gravitational field-flow fractionation (GrFFF) is applied to the fractionation of active dry wine yeast. An experimental approach to the analysis of the effects that field variation by changing mobile phase composition and flow-rate have on the fractionation process of standard particles (polystyrene) was first developed to further obtain effective fractionation of wine yeast by GrFFF. Scanning electron microscopy and Coulter counter particle size measurements were used to monitor the fractionation extent and capabilities of GrFFF to describe the distribution of yeast cells populations.
    Journal of Chromatography A 07/2001; 919(2):339-47. · 4.61 Impact Factor