Carmen Ancín

Production of volatile compounds in the fermentation of chardonnay musts inoculated with two strains of Saccharomyces cerevisiae with different nitrogen demands

This paper studies the behaviour of two strains of Saccharomyces cerevisiae with different nitrogen requirements in the production of esters and higher alcohols during alcoholic fermentation. To carry out the study a chardonnay must with a high content of nitrogen compounds was used. The results showed that the strain with the highest nitrogen demand produced a higher concentration of esters during fermentation and gave rise to a wine with a somewhat lesser content of higher alcohols. The formation of volatile compounds was probably related to the consumption of nitrogen by the strains as the nitrogen nutrients act as precursors in the synthesis of esters and alcohols and regulate their production.

Influence of prefermentation clarification on the higher alcohol contents of wines

Abstract Nitrogenous compounds and the amount of solids have an effect on both the metabolic pathway and on the concentration of higher alcohols (HA) in wines. In this study, the influence of two prefermentation clarification treatments (static sedimentation and vacuum filtration) on the concentration of nitrogen which can be assimilated and glucose consumption have been studied with respect to HA concentration of wines. The results show that total HA decreased with increasing must clarification level, and the clarification is more of a determining factor than amino nitrogen. No relation has been found in these complex mediums between Leu concentration and the formation of isoamyl alcohol nor between Val and isobutyl alcohol. The concentration of n-propyl alcohol was unrelated to concentration and consumption of Thr and Gaba. There seems to be a relationship between slower glucose consumption in filtered musts and lower HA concentration in wines.

Influence of vacuum filtration of Viura must on the concentration of fatty acids and their utilization in fermentation

Fatty acids such as palmitoleic, oleic, linoleic and linolenic along with sterols constitute growth or survival factors for yeast. The objective of this work was to study the influence of vacuum filtration of Viura must on fatty acid contents and their use during fermentation. The results were compared with unclarified must, the control. Filtration drastically reduced the total fatty acid concentration (81.5%) and especially unsaturated fatty acids (97.1% of linoleic, and 100% of linolenic), as well as the minor saturated acids, arachidic and behenic. In the first half of fermentation, fatty acids were excreted in the filtered must (76.8%) whereas they were consumed in the control (46.8%). In the second half of fermentation, there was greater consumption in the control sample (74.5%) than in the filtered sample (37.4%).

Sedimentation clarification of Garnacha musts. Consumption of amino acids during fermentation and aging

Given the importance of finding good methods for the clarification of musts, the aim of this study was to observe the influence of sedimentation on the consumption of amino acids and the other nitrogenous compounds during fermentation and aging of obtained wines. Garnacha grapes were selected and original must was taken as a control. In decanted Garnacha musts, the reduction in the fermentation rates was not due to the deficiency of assimilable nitrogen (ammonium and amino nitrogen). In the first half of fermentation, basic amino acids were consumed similarly in both musts, however, the neutral and dicarboxylic acids were consumed more in the decanted must. In the latter part of fermentation, there was a greater liberation, in general, of amino acids in the decanted must, probably due to the lesser tolerance of yeast to ethanol in the clarified medium.

Changes in free amino acid concentration during stabilization and aging of wines derived from garnacha and viura musts clarified by static sedimentation

Abstract Stabilization of wine by refrigeration assures an increase in cleanliness and effective physicochemical stabilization. The objective of the present work was to study the changes in free amino acid concentrations in rose and white wines stabilized by precipitation in the cold, filtered through non-sterilizing filters and aged for a year in bottle. The wines derived from musts clarified by static sedimentation were compared with control wines obtained from uncarified musts. The results show that the unclarified-must wines had a greater consumption of amino acids due, probably, to the greater microbial population.

Sedimentation clarification of viura musts. Utilization of amino acids during fermentation

The influence of sedimentation on viura musts concentration of free amino acids and changes during fermentation were studied; the results were compared with an unclarified sample. The protein fraction was reduced by this treatment; the amino nitrogen increased slightly in the decanted must, and the concentration of ammonium nitrogen was similar in both samples. The decanted must had a greater concentration for most of the amino acid constituents of proteins, neutral as well as basic. This treatment did not alter the medium sufficiently to modify yeast utilization of these nutrients during fermentation; in fact, in both samples, basic, neutral, and acidic amino acids were consumed in a similar manner in the first half of fermentation (until 50% sugar consumption) and were excreted similarly in the freshly produced wine.