Jorge B. Velázquez

Production of higher alcohols, ethyl acetate, acetaldehyde and other compounds by 14Saccharomyces cerevisiae wine strains isolated from the same region (Salnés, N.W. Spain)

Fourteen strains of the yeastSaccharomyces cerevisiae were isolated from three wineries in the Salnés wine region (N.W. Spain) at the three different periods of the natural fermentation. Each wild yeast was screened for production of acetaldehyde, ethyl acetate, isobutanol,n-propanol, amylic alcohol and other important enological compounds during laboratory scale fermentations of grape juice. After 25 days at 20°C, the analytical results evidenced variations in the production of acetaldehyde (from 13.1 to 24.3 mg/l), isobutanol (from 27.7 to 51.1 mg/l), amyl alcohols (from 111 to 183 mg/l) and ethyl acetate (from 19.3 to 43.7 mg/l). Although isolated from the same wine region, differences in the wine composition were observed depending on the particular yeast strain used for the vinification experiments.

Mevalonic acid increases trans-astaxanthin and carotenoid biosynthesis in Phaffia rhodozyma

SummaryMevalonic acid has been tested as enhancer of pigment biosynthesis in wild-type Phaffia rhodozyma. The addition of 0.1% mevalonic acid to the culture media stimulated both trans-astaxanthin and total carotenoids biosynthesis, with average increases by ca 400%.

Use of Natural Preservatives in Seafood

Seafood products are known to be especially susceptible to both microbiological and biochemical spoilage pathways. Accordingly, efficient and hygienic preservation processes should be applied immediately after capture/slaughter to preserve product freshness and quality. The development of effective processing treatments to extend the shelf life of fresh fish products is a must.

Improvement of the alcoholic fermentation of grape juice with mixed cultures of Saccharomyces cerevisiae wild strains. Negative effect of Kloeckera apiculata

Four assays were designed to study the fermentative behaviour of two selected wild strains of Saccharomyces cerevislae when inoculated in sterilized grape juice either alone or in association. In addition, a wild strain of Kloeckera apiculata was employed for studying and characterizing the influence of this micro-organism on the fermentations when associated with Sacch. cerevisiae. Fermentation was improved when the two strains of Sacch. cerevisiae were grown together since the residual sugar fell to 0.12% and ethanol increased up to more than 11% (v/v). In this case, a proliferation of the two strains with successive exponential phases was observed. On the other hand, when Kloeckera apiculata was incorporated into the fermentations, these were incomplete with a residual sugar level of 1.64% and a final ethanol concentration of 6.4%.

Role of killer character in spontaneous fermentations from NW Spain: ecology, distribution and significance

SummaryThe presence of killer, resistant and sensitive populations of Saccharomyces cerevisiae along the successive stages of alcoholic fermentation in three vineyards from NW Spain was investigated. The global results showed that approximately 71% were killer-sensitive strains, 6.6% were killer-resistant, and 22.4% belonged to the k2 killer type. However, there were important differences concerning the presence of the three phenotypes during successive stages of fermentation. Killer populations were isolated at the highest percentages in samples from must and from active alcoholic fermentations. Killer-resistant strains steadily increased during fermentation. Additionally, important differences in these populations were observed among the three vineyards. In this sense, the presence of killer populations was more important in samples from the vineyards with higher average pH values of the must. However, great differences in the distribution of killer phenotype between successive vintages (with the same initial pH of must) belonging to the same vineyard implies the presence of other factors effecting killer behaviour.

Novel Technologies for the Preservation of Chilled Aquatic Food Products

Most fish and other aquatic species give rise to products of great economic importance in many countries. The demand for such products has been increasing steadily over the last century and shows no signs of lessening, as fishing and farming actually constitute a basic source of food for all populations of the world.

Effect of L-malate, D-glucose and L-lactate on malolactic fermentation and growth of Lactobacillus plantarum and Lactobacillus curvatus wild strains isolated from wine

Abstract l -Malate fermentative rate in Lactobacillus plantarum and Lactobacillus curvatus was improved when l -malate was over 0.1% but decreased when exogenous d -glucose raised over 0.3% or in the presence of exogenous l -lactate. Significant increases in the growth were observed in the presence of exogenous d -glucose. l -malate residual concentrations were in all cases below 1%.

Characterization of killer-resistant strains of Saccharomyces cerevisiae isolated from spontaneous fermentations

A study of 26 killer-resistant wine strains of Saccharomyces cerevisiae, isolated during spontaneous fermentations in three vineyards in NW Spain, was carried out employing several methods that included a spheroplast-killing assay and analysis of chromosomal DNA patterns by pulse-field agarose electrophoresis. The results showed that 92% of the strains were derivatives of K2 killer toxin producing wine strains isolated from the same fermentations, and that they could be grouped into four different karyotypes. The remaining strains were killer-resistant at cell-wall level and were not related to the others, as was demonstrated by the absence of L and M ds-RNAs and by their different karyotypes.

Biotyping of Campylobacter jejuni and Campylobacter coli infections in Spain

Biochemical profiles were studied in 102 Campylobacter isolates from patients affected by enteric disease in Orense (Spain) over a 1-year period. The isolates were identified as hippurate-positive Campylobacter jejuni (n = 90), Campylobacter coli (n = 10) and hippurate-negative C. jejuni (n = 2). Seventy-seven of the hippurate-positive and both hippurate-negative C. jejuni isolates were biotyped as C. jejuni subsp. jejuni biotype 1, nine as C. jejuni subsp. jejuni biotype 2 and four as C. jejuni subsp. doylei. Hippurate-hydrolysis was correlated to a simple scheme based on L-arginine arylamidase production, propionate assimilation and malate assimilation which yielded sensitivity and specificity values of 0.90 and 1.00, respectively. Effective grouping of nalidixic acid-resistant C. jejuni and C. coli isolates (38.5% of the total) was also achieved.

Influence of the curing of the killer phenotype inSaccharomyces cerevisiae wine strains on their fermentative behaviour

Fermentative behaviour and cell growth have been studied in grape juice inoculated either with two killerSaccharomyces cerevisiae wild strains or with their Acridine Orange-cured isogenic counterparts. The number of viable cells/ml at the beginning of the fermentation, as well as during exponential growth, were higher in grape juices inoculated with the cured strains. The CO2 production, fermentative rate and ethanol and acetic acid production were also higher in the cured strains, particularly during the stage of active fermentation. These differences, however, were minimal at the end of the fermentations.