Avaluació dels condicionants del most en el desenvolupament de la fermentació alcohòlica a baixes temperatures
Title: Evaluation of factors affecting must composition in the development of alcoholic fermentation at low temperatures <br/><br/>Josep M. Llauradó i Reverchon under the guidance of Dr. Albert Mas i Barón and Dra. Magdalena Constantí i Garriga.<br/>Departament de Bioquímica i Biot...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2002 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/8644 |
| Acceso en línea: | http://www.tdx.cat/TDX-0108103-100007 http://hdl.handle.net/10803/8644 |
| Access Level: | acceso abierto |
| Palabra clave: | nitrògen baixes temperatures fermentació alcohòlica saccha/omyle 663/664 |
| Sumario: | Title: Evaluation of factors affecting must composition in the development of alcoholic fermentation at low temperatures <br/><br/>Josep M. Llauradó i Reverchon under the guidance of Dr. Albert Mas i Barón and Dra. Magdalena Constantí i Garriga.<br/>Departament de Bioquímica i Biotecnologia<br/>Defended/Presented on the 23rd of October 2002<br/><br/>The alcoholic fermentation at low temperatures (< 15 ºC) results in more aromatic wines with paler colour, characteristics highly appreciated in white and rose wines. Although this enological practice is well established in some European traditional processings (Sauternes, Jura, Amarone, Vinosanto, second fermentation of sparkling wines), low temperature fermentations can be problematic in musts from southern regions. These musts have typically a high sugar content and a low nitrogen availability for yeast. In addition, at low temperatures, a higher competition for nutrients occurs between the inoculated yeast and the non-Saccharomyces species. Altogether can result in stucked or delayed fermentations.<br/><br/>In this work the nitrogen composition of five varieties of fresh must (white Grenache, Chardonnay, Pinot Noir, Carinyena and Riesling) were characterized as well as their respective microfermentations (500 mL) evaluating the variety effect, the temperature (13 ºC and 17 ºC) and the addition of yeast nutrients, on the fermentative kinetics. A new empirical parameter was designed for this study (R). The calculation of R is based on the nitrogen content of some neutral amino acids and the initial sugar concentration. A correlation between the value of R and the maximum rates in all the fermentations was observed, therefore R could be considered as an estimator of the fermentability of must. Low temperature of fermentation (13 ºC) reduced the amounts of ethyl acetate, acetaldehyde and acetic acid. On the other hand, yeast nutrients showed a clearly incidence in the composition of the higher alcohols, limiting their production.<br/><br/>According to the previous results Carinyena presented the most difficult fermentations, hence fresh must of this variety was used in a second experiment. The must was supplied with several combinations of yeast nutrients (diammonium hydrogen phosphate and Fermaid K) and inoculated with different commercial yeast strain. A slight sinergic effect of the addition of both yeast nutrients was observed depending on the yeast strain inoculated. In addition, the yeast nutrients enhanced the imposition of the inoculated yeast strain in a must with a significant initial population of wild yeast. The presence of wild yeast, specially Candida stellata, caused changes in the differential consumption of glucose and fructose. The addition of yeast nutrients reduced the amount of acetic acid and increased glycerol content; those modifications were different depending on the inoculated yeast strain.<br/><br/>Two commercial yeast strains were pre-adapted to the fermentation temperature (13 ºC and 17 ºC). Their fermentative kinetics were compared to those carried out at 25 ºC (fermentation starter effect) with yeasts simply rehydrated and with a cryotolerant strain. A fermentative improvement was observed due to the temperature pre-adaptation dependent on the yeast strain. Furthermore, the temperature adaptation had an incidence on the composition of secondary products that may affect the quality of wines. |
|---|