María Carmen Polo

Influence of the polysaccharides and the nitrogen compounds on foaming properties of sparkling wines

Abstract The increase in the height of the wine contained in a tube, when air is passed through a fritted plate placed at its bottom was measured and used to evaluate the foam characteristics of base wines and sparkling wines. The height was detected with an ultrasonic wave transmitter/receiver, using original equipment and software. The relationship between the foam characteristics of these wines and their content in neutral and acid polysaccharides, free amino-acids, peptides and protein nitrogen was studied. It was seen that there are significant differences in foam parameters according to grape variety and aging time. It was also seen that the height reached by the foam shows a positive correlation with most of the free amino-acids, with the polysaccharides and with the protein nitrogen. No relationship was found between foam characteristics and concentrations of wine peptides. Predictive models were obtained for the parameters defining foam, based on content in neutral polysaccharides, protein nitrogen and the free amino-acid phenylalanine.

Polydimethylsiloxane solid-phase microextraction-gas chromatography method for the analysis of volatile compounds in wines. Its application to the characterization of varietal wines.

A study was made of the validity of the solid-phase microextraction method, using a polydimethylsiloxane coated fused-silica fiber, for the extraction-desorption of the minor volatile compounds from wine before their gas chromatographic analysis. The aspects considered were the influence of ethanol on extraction, repeatability, limits of detection, linearity and recovery of compounds. This method, together with the direct injection of the major volatile compounds, was applied to 16 varietal wines. The findings indicate that the method is a highly suitable technique for the analysis of wines and that the volatile composition of wines depends, at least partly, on the grapes with which they have been made.

Release of nitrogen compounds to the extracellular medium by three strains of Saccharomyces cerevisiae during induced autolysis in a model wine system

To detect differences among three strains of Saccharomyces cerevisiae used in the manufacture of sparkling wines and to study the changes in nitrogen compounds during autolysis, a model wine system was used. Significant differences were observed between the mean values of the autolytic capacity of the three strains. The amount of nitrogen (total, protein, peptide and amino) present in the autolysates and the concentration of most free amino acids was significantly affected by the strain. These findings suggest that the strain of yeast used in the manufacture of sparkling wines can play an important role in the aging process and can affect final composition.

Influence of the yeast strain on the changes of the amino acids, peptides and proteins during sparkling wine production by the traditional method.

The influence of five yeast strains on the nitrogen fractions, amino acids, peptides and proteins, during 12 months of aging of sparkling wines produced by the traditional or Champenoise method, was studied. High-performance liquid chromatography (HPLC) techniques were used for analysis of the amino acid and peptide fractions. Proteins plus polypeptides were determined by the colorimetric Bradford method. Four main stages were detected in the aging of wines with yeast. In the first stage, a second fermentation took place; amino acids and proteins plus polypeptides diminished, and peptides were liberated. In the second stage, there was a release of amino acids and proteins, and peptides were degraded. In the third stage, the release of proteins and peptides predominated. In the fourth stage, the amino acid concentration diminished. The yeast strain used influenced the content of free amino acids and peptides and the aging time in all the nitrogen fractions.

Analytical methods for the characterization of proteins and peptides in wines

Abstract Although proteins and peptides are minor constituents of wine, they make a significant contribution to its quality. Proteins can cause a number of technological problems during vinification and may be responsible for the appearance of turbidity in bottled wine. Peptides exhibit surfactant and sensory properties that can influence the organoleptic characteristics of wine. These reasons make protein and peptide analysis a necessity. In this paper, some of the applications in sample preparation, electrophoretic and chromatographic analysis, and detection of proteins and peptides in wine are examined. Special attention is paid to the methodologies that the authors have used in previously published studies, in some cases developed by them, and in other cases taken from the literature and used routinely in their laboratory.

Structural and ultrastructural changes in yeast cells during autolysis in a model wine system and in sparkling wines.

This study shows the changes that occur during the autolysis of yeast in a model wine medium and in a sparkling wine after 12 months of aging, using Nomarsky Light Microscopy and Low Temperature Scanning Electron Microscopy (LTSEM). The size of the yeasts after 24 h of autolysis in a model medium is much smaller than when they are in the growth stage. With LTSEM. a large number of folds can be observed on the surface of the yeast and practically empty cells. Greater morphological changes, both structural and ultrastructural, can be observed in the yeast after 12 months of aging in wine than in the yeast after 24 h of induced autolysis. However, less of the cytoplasmic content of the yeast that has undergone autolysis in the wine was solubilized than that of the yeast after 24 h of autolysis in the model wine system. These findings indicate that autolysis of yeast in wine is a long-lasting process, which continues for at least 12 months.

Proteolytic activity of Leuconostoc oenos: Effect on proteins and polypeptides from white wine

Abstract The proteolytic activity of Leuconostoc oenos protease on white wine proteins and polypeptides was studied. Comparison of the peptide profiles before and after protease action demonstrated the presence of two new and an increase in two other peptide peaks. In total 56.7 mg l−1 of peptides was liberated by action of the Lc.oenos proteases. Essential amino acids for Lc. oenos growth were liberated as free amino acids, and arginine, which has a stimulatory effect on Lc. oenos growth, was quantitatively the more important amino acid obtained by protease activity. Thus proteolytic activity serves to provide the cells with essential growth factors.

Effect of the addition of bentonite to the tirage solution on the nitrogen composition and sensory quality of sparkling wines

When producing sparkling wines by the traditional method, a small amount of bentonite is added to the tirage solution to help with the flocculation of the yeast. This work studies the effect of this addition on the nitrogen composition and sensory quality of the sparkling wines. Two batches of sparkling wines were industrially produced, one with addition of bentonite to the tirage solution and the other without bentonite addition. Samples were taken at 20, 40, 90, 180, 270 and 365 days of aging with yeast. Total, free amino-, protein- and peptide-nitrogen concentrations were determined and foam properties and sensory quality were evaluated. It was observed that the bentonite retained part of the peptides and proteins and had an adverse effect on the sensory quality of the wine.

Classification of variety musts by statistical analysis of their electrophoretic protein pattern

Abstract Unsupervised classification techniques (Principal Components Analysis and Cluster Analysis) have been applied to electrophoretic analytical data from seventeen grape must samples of six different cultivars. A good grouping of samples according to their cultivar has been obtained.

Characterization of the proteic and the phenolic fraction in tartaric sediments from wines

Abstract The proteic and phenolic fraction precipitated along with potassium bitartrate crystals during the different stages of Spanish sparkling wine-making were studied. Electrophoretic and chromatographic techniques, together with chemical analysis, were carried out to determine the nature and physico-chemical properties of the organic compounds present in sediments. The phenolic compounds were more abundant and highly polymerized in the samples obtained from cold stabilization. Cinnamic acids esterified with tartaric acid comprised the main low molecular weight phenolic compounds in all the samples. There was a propensity for certain proteins to precipitate out of the wines, given that the main bands detected in the tartrates presented higher electrophoretic mobilities than those in the wines themselves. The distribution of the molecular weights of the proteins in the tartrates differed from that of the proteins in the wines. The molecular weights of the main bands obtained using SDS-PAGE were smaller than 20 000 or higher than 50 000 in the case of the proteins from the tartrates, whereas the molecular weights of the main bands for the proteins in the musts and in the wines ranged between 20 000 and 40 000.