Identificador: TDX:446
Autors: Labbé Pino, Mariela Alejandra
Resum:
This thesis has been divided into three main subjects. The first focuses on how different storage conditions over a year affect the physical and chemical properties of commercial vinegars. The second deals with the aging of model vinegar solutions and wine vinegars by oak chips, with the purpose of understanding the evolution of color and the extraction of polyphenols from wood. The third studies lead reduction at trace levels in model vinegar solutions and commercial wine vinegars using a batch and continuous cation exchange resin. Three wine vinegars Chardonnay, Cabernet Sauvignon and Muscat and one apple vinegar were chosen to study the effect of different storage conditions. For one year various physical and chemical parameters were studied and only at the beginning and the end of this period were the phenolic and furanic compounds quantified. The Muscat wine and apple vinegars showed significant browning when temperature was increased. The total polyphenol content remained stable, except in those vinegars stored at high temperature, largely because of the increase in furanic compounds. American and French oak chips were used to study the aging of two model vinegar solutions (with and without added sugar), one sparkling-wine vinegar (without sugar addition) and one white-wine vinegar (with added sugar). The model vinegar solutions were aged for 448 days and the wine vinegars for 192 days. The total polyphenol content, phenolic profile and color were studied by CIELab coordinates. The evolution of the chromatic characteristics in model solutions and wine vinegars were not affected by the sugar concentration and all the vinegars showed similar behavior over time. The total polyphenol extraction in model vinegar solutions was higher when French oak chips were used and were not affected by the sugar concentration either. The total phenol extraction of the sparkling-wine vinegar was similar to that of the model vinegar with no added sugar. However, the total polyphenol extraction in white-wine vinegar was 40 % of that obtained in a model vinegar solution with added sugar. Nine phenolic compounds from wood were identified. The extraction of phenolic compounds was maximum during the first month, after which the extraction was only significant for a couple of compounds in both of wine vinegars. To study lead reduction in vinegar the adsorption kinetics was determined in a batch system with continuous stirring and a constant amount of resin (Lewatit TP 207). Two concentrations of acetic acid and two initial concentrations of lead were used in this case. The adsorption capacity of the resin was also evaluated using four commercial vinegars: balsamic vinegar, sherry vinegar, barrel-aged wine vinegar and apple-cider vinegar. The kinetic results of the lead adsorption from model vinegars showed that the adsorption equilibrium was reached within 24 hours that the acetic degree did not affect the capacity of the resin to adsorb lead, and that the adsorption isotherm was fitted correctly by the Freundlich equation. The lead reduction in model vinegar solutions was higher than in commercial vinegars, in which the reduction was highest in apple-cider vinegar. The application of this resin in a continuous system using a packed column at two retention times was also studied. The lead reduction is higher in the model vinegar solutions than in the commercial vinegars. We believe that this greater adsorption may be related to the complexity of the matrix. The physical and chemical parameters were not affected by the resin treatment.
Repositori URV