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Biomedical subjects

Manuel Medina

Publications and source records attributed to Manuel Medina.

14 recordsLinked to original sources
PubMed2005

Biological aging of sherry wines using pure cultures of two flor yeast strains under controlled microaeration.

Sherry wines obtained after biological aging for an average of 0, 2, and 4 years were inoculated separately with the flor yeast strains Saccharomyces cerevisiae var. capensis and Saccharomyces bayanus and subjected to short, periodic microaeration to a dissolved oxygen concentration of 4 mg L(-1) after formation of the yeast film. A principal component analysis with the acetaldehyde, ethanol, volatile acidity, and glycerol concentrations obtained was performed. The first principal component was found to account for 49.5% of the overall variance and to be defined mainly by glycerol and ethanol. The second component accounted for 38.8% of the variance and was defined by volatile acidity and acetaldehyde. The conditions used in the tests allowed the biological aging of the wines to be substantially shortened. Thus, 42 days after flor-film formation by S. cerevisiae var. capensis, 0- and 2-year-old wines exhibited parameter values similar to those obtained for the wine aged for 4 years. The wines inoculated with S. bayanus exhibited high acetaldehyde concentrations and ethanol levels above 15% (v/v)-sherry wines with alcohol concentrations below 14.5% are undesirable-, so one need not exclude the sequential or simultaneous inoculation of S. bayanus together with S. cerevisiae var. capensis in order to improve the biological aging process.

Acetaldehyde↗
PubMed2005

Potential application of a glucose-transport-deficient mutant of Schizosaccharomyces pombe for removing gluconic acid from grape must.

Musts from rotten grapes typically contain high levels of gluconic acid, which can raise severe problems in winemaking processes. In this work, the ability of the glucose-transport-deficient mutant YGS-5 of Schizosaccharomyces pombe to completely or partly remove gluconic acid from a synthetic glucose-containing medium and the potential use of this yeast strain for the same purpose in musts and wines were examined. Surprisingly, the S. pombe YGS-5 strain successfully removed 93% of the initial gluconic acid (2.5 gL(-1)) and 80% of the initial malic acid (1.0 gL(-1)) within 30 h after inoculation. Also, the yeast strain produced no volatile compounds other than those obtained in fermentations conducted with the wine yeast Saccharomyces cerevisiae. S. pombe YGS-5 could thus be used to remove gluconic acid present in musts from rotten grapes. On the basis of these results, various ways of using S. pombe YGS-5 to treat musts containing gluconic acid in order to solve the problems due to the high gluconic acid concentrations in botrytized grape must are proposed.

Fermentation↗
PubMed2005

Retention of browning compounds by yeasts involved in the winemaking of sherry type wines.

Wine model solutions were used to study the ability of dehydrated yeasts to retain the brown products formed in the reaction between (+)-catechin and acetaldehyde. Saccharomyces cerevisiae races capensis and bayanus, two typical flor yeasts involved in the biological aging of sherry wines, had a higher capacity to retain coloured compounds than S. cerevisiae fermentative yeast. Of the flor yeasts, capensis exhibited a higher colour reduction capacity than bayanus. Such differences may account for the different rate at which browning compounds are removed at different times of year during the biological aging of wines.

Acetaldehyde↗
PubMed2004

Gas chromatographic quantification of major volatile compounds and polyols in wine by direct injection.

Methanol, propanol, isobutanol, isoamyl alcohol, 2-phenylethanol, acetaldehyde, 1,1-diethoxyethane, acetoin, ethyl acetate, ethyl lactate, and ethyl succinate and the polyols 2,3-butanediol (levo and meso forms) and glycerol were quantified by direct injection of wine samples. Linear responses over the usual concentration ranges for these compounds and r2 values from 0.9932 to 0.9998 were obtained. The confidence limits for the mean values ranged from 2.34% for diethyl succinate to 8.52% for 1,1-diethoxyethane, both at a probability level of 0.05. Relative errors ranged from 8 to 10% for the polyols and 1,1-diethoxyethane and were all less than 5% for alcohols and acetaldehyde. The proposed method is useful with a view to identifying relationships between alcoholic fermentation byproducts and controlling biological or chemical aging in wines.

Acetaldehyde↗
PubMed2004

Effect of Schizosaccharomyces pombe on aromatic compounds in dry sherry wines containing high levels of gluconic acid.

Volatile compounds have been determined in control dry sherry wines and those supplemented with gluconic acid, which were inoculated with the Schizosaccharomyces pombe 1379 (ATCC 26760) yeast strain. These compounds were grouped, according to volatiles exhibiting the identical odor quality, into nine groups of the same odor character (aromatic series) as a way of establishing the aroma profile for the studied wines. Control and supplemented wines showed changes in the balsamic, spicy, roasty, and fruity aromatic series, and tasters judged the aroma as typical of wines subjected to biological aging. This fission yeast may be used as a treatment to reduce gluconic acid contents in wines obtained from rotten grapes, making feasible the incorporation of these wines into the biological aging process. In addition, this procedure may also help to accelerate the traditional biological aging in sherry winemaking due to the contribution of some specific compounds by S. pombe to the wine.

Gluconates↗
PubMed2004

Off-vine grape drying effect on volatile compounds and aromatic series in must from Pedro Ximénez grape variety.

Changes in 36 volatile compounds of must from ripe grapes dried by direct exposure to sun and must from ripe grapes were studied. Compounds not dependent on sampling site in both musts were selected, and their concentration/Brix degree ratio values, were subjected to variance analysis. Only butan-1-ol and isoamyl alcohols showed no differences, while (E)-hex-3-en-1-ol, (Z)-hex-3-en-1-ol, (E)-hex-2-en-1-ol, (E)-hex-2-enal, hexanoic acid, isobutanol, benzyl alcohol, 2-phenylethanol, gamma-butyrolactone, gamma-hexalactone, and 5-methylfurfural, showed significant differences between the two must types, which may be ascribed to the drying process. An approach to describe must odor has been carried out by grouping volatile compounds in aromatic series, increasing their values in the fruity, solvent, sweet, and roasted series and diminishing the herbaceous as a consequence of the drying process.

Desiccation↗
PubMed2004

Interaction of yeasts with the products resulting from the condensation reaction between (+)-catechin and acetaldehyde.

The condensation reaction between (+)-catechin and acetaldehyde was studied in model solutions in the presence and absence yeasts in order to evaluate its contribution to color changes in fermented drinks such as white wine. On the basis of the results, the yeasts retain the oligomers produced in the reaction, their retention ability increasing for higher polymerization degrees. As a result, the color of model solutions, measured as the absorbance at 420 nm, was found to decrease after the addition of yeasts. On the other hand, the yeasts exhibited no inhibitory effect on the condensation reaction, which took place at the same rate in their presence and absence. At acidity levels and reactant concentrations similar to those in wine, with acetaldehyde in high concentration as it is present in sherry wines, the reaction was found to occur very slowly. Taking into account that Yeasts are present during most of the winemaking process; consequently, they retain oligomers, and the studied reaction could mainly contribute to the alteration of the color of white wine after bottling.

Acetaldehyde↗
PubMed2004

Gluconic acid consumption in wines by Schizosaccharomyces pombe and its effect on the concentrations of major volatile compounds and polyols.

Schizosaccharomyces pombe 1379 (ATCC 26760) yeast strain in wine substantially increases acetaldehyde and 1,1-diethoxyethane concentrations and to decreases levo-2,3-butanediol, glycerol, acetoin, and gluconic acid concentrations. In this study, S. pombe has been used for the first time to reduce gluconic acid in wine under aerobic conditions. Only acetaldehyde and acetoin exhibited significantly higher levels in the wines containing gluconic acid. The high in vitro specific activity of alcohol dehydrogenase observed may be directly related to the high production of acetaldehyde by the studied fission yeast.

Acetaldehyde↗
PubMed2003

[Orthopedic implant infection: prognostic factors and influence of long-term antibiotic treatment on evolution. Prospective study, 1992-1999].

INTRODUCTION: Orthopedic implant infections are significant because of their morbidity, a tendency to serious relapses and an elevated health cost. OBJECTIVES: To study prognostic factors and the influence of long-term antibiotic treatment on the evolution of orthopedic implant infections. METHODS: This prospective study was performed in 110 patients with orthopedic implant infections. Clinical, analytical, and microbiological studies, as well as gammagraphy with Tc, Ga and labeled leukocytes, were performed in all patients. Controls were carried out at 7, 15 and 30 days after starting treatment, every 3 months thereafter until the end of treatment, and every 6 months thereafter up to one year after stopping treatment. Initial antibiotic treatment was prescribed according to the epidemiological characteristic of the type of infection and was modified according to the microorganism isolated. Duration of treatment was established by patient and implant characteristics, severity of infection and evolution of the process, and it was adjusted to criteria of cure, failure and relapse. RESULTS: Among the 110 cases, 63 were women and 37 men, with a mean age of 59.6 years (range 18-79 years). Implants included 72 joint prostheses (42 knee, 29 hip and 1 shoulder) and 38 bone implants. Microbiological documentation was obtained in 60%; among these, 60.6% were gram-positive cocci, with a predominance of staphylococci, 33.3% were gram-negative bacilli and 6.1% were anaerobic microorganims. Prognostic factors significantly associated with failure or relapse included previous joint surgery, previous hospital stay longer than 15 days, diabetes, microbiological isolation and treatment with cefuroxim plus rifampicin. Mean treatment duration was 9.8 months (range 2-17 months). Antibiotic treatment consisted of the following: 61 cases received fluorquinolones or cotrimoxazole plus rifampicin, 29 received cefuroxime-axetil plus rifampicin and the remaining 20 received monotherapy. Among 110 cases, 91 cured (83%). Treatment failures or relapses were observed in 19 (17%) patients; 26.7% of the latter were related to the implants. Tolerance to long-term antibiotic treatment was good.Conclusion. Long-term antibiotic treatment lasting a mean of 9.8 months had a positive influence on the evolution of orthopedic implant infections.

Adult↗
PubMed2002

Analytical study of aromatic series in sherry wines subjected to biological aging.

The odor activity values (OAVs) for 49 aroma compounds in commercial sherry pale white wines were grouped, according to the similarity of their aroma descriptors, into nine odor classes with a view to establishing the aroma profile for this type of wine. The results revealed the profile to be largely comprised of the series named "fruity" and "balsamic", mainly as a result of the 1,1-diethoxyethane content in the wines. The same series were calculated from the OAVs obtained in biological aging experiments, carried out with selected strains of the flor yeasts Saccharomyces cerevisiae and Saccharomyces bayanus, over a period of 9 months. Based on the aroma profiles thus obtained, after 6 months of aging the latter race yielded OAVs for the fruity and balsamic series not significantly different (p < 0.05) from those for commercial wines aged for 5 years. However, except for the series named "solvent", all others exhibited lower values in the experiments carried out with selected strains than in the commercial wines, mainly as a result of the absence of contact with wood of the former wines. Taking into account the results, the biological aging of this type of sherry wine can be shortened by subjecting it to controlled aging with selected yeast strains in a first stage and subsequently allowing it to stand in wood casks in a second stage.

Fermentation↗
PubMed2002

Adsorption of phenolic compounds and browning products in white wines by yeasts and their cell walls.

Dehydrated yeast cells at variable concentrations were used as fining agents to decrease the color of white wines with two different degrees of browning (0.153 and 0.177 au, measured at 420 nm). Both wines showed a linear decrease of browning with increasing yeast concentration. However, in terms of efficiency, the yeasts exhibited a higher color lightening at greater concentrations acting on the darker wine. This suggests a preferential retention of some types of yellow-brown compounds that could increase their concentrations at the higher degree of browning. To confirm the role of yeast cell walls in the retention of browning compounds and to evaluate their potential use as fining agents, they were applied at variable concentrations to a browned wine (0.175 au). The cell walls were found to be the active support for the adsorption of browning compounds, but their efficiency was much lower than that of an equivalent amount of the yeast cells from which they were obtained. Finally, HPLC determinations of low-molecular-weight phenolic compounds showed flavan-3-ol derivatives to be significantly retained by both yeasts and their cell walls.

Adsorption↗
PubMed2002

Yeast-induced inhibition of (+)-catechin and (-)-epicatechin degradation in model solutions.

(+)-catechin and (-)-epicatechin degradation in water-alcohol solutions containing Fe2+ and tartaric acid was studied in the presence and absence of yeasts. On the basis of the results, yeast partially inhibited the degradation of both flavans, with much slower formation of browning products absorbing at 420 and 520 nm. In comparative terms, yeast was found to be more efficient toward the degradation products of (+)-catechin absorbing at the latter wavelength. Likewise, the presence of yeast decreased the yield of a group of colored compounds eluting at high retention times in HPLC and indicated these as important contributors to color darkening in white wines. This inhibitory effect may in part account for the resistance to browning observed over periods of several years in sherry wines subjected to biological aging under flor yeast.

Catechin↗
PubMed2002

[Infections in joint prostheses: epidemiology and clinical presentation. A prospective study 1992-1999].

BACKGROUND: The prosthetic infection is a serious complication due to diagnostic problems. AIM: To determinate epidemiological characteristics, and clinical patterns of infections associated to prosthetic materials to improve the diagnosis and management. PATIENTS AND METHODS: From december 1992 to december 1999, 110 patients with prosthetic infections were prospectively evaluated. Diagnosis was made according to standard microbiological, clinical and radiological criteria. RESULTS: The incidence was 5.1% (110/1,400) prosthetic materials insert in the period of study. The average age was 59.6 years (range 18-79), and the majority of patients 63 (57.2%) were female. Forty-two (38%) suffered a total knee replacement, 29 (26%) a total hip replacement, 1 (1%) shoulder replacement and 38 (34%) autogenous bone gratting. In 29 patients (26.3%) a previous chronic disease had been diagnosed (diabetes, neoplasis, rheumatoid arthritis). Previous use of antibiotics was detected in 58 patients (51%), being ciprofloxacin the most frequently used. An etiological diagnosis was reached in 66 patients (60%), isolated grampositive in 58.2%, gramnegative in 32.8%, fundamentally by Staphylococcus sp. and P. aeruginosa respectively. In 9% anaerobe were isolated. There were early infections in 67 cases, delayed in 25, and late in 18. All the patients had local pain and flogotiv signs as initial findings, whereas 46 (41.8%) developed osteocutaneous fistula and only 5 (4.5%) presented temperature. CONCLUSIONS: Prosthetic infection is a frequent complication after articular replacement, and grampositive cocci predominate as ethilogical agents. Sistemic clinical manifestations are uncommon.

Adolescent↗