Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.14/16324
Título: Production of volatile phenols by Lactobacillus plantarum NCFB 1752 influence of wine related factors
Autor: Fras, Pauline Capucine
Orientador: Couto, José António
Campos, Francisco
Data de Defesa: 2011
Resumo: Lactic acid bacteria play important roles in wine and wine process. They are responsible for the occurrence of malolactic fermentation and may have positive and negative impacts on the organoleptic perception of a wine. Volatile phenols are a class of volatile compounds which give a “horse sweat” and “pharmaceutical” unpleasant odour to wine. It is well-known that production of these compounds is mainly due to yeasts Dekkera/Brettanomyces during alcoholic fermentation and post-fermentation steps, but recently it has been found that certain LAB strains can produce reasonably high amounts of these compounds in laboratory conditions despite this production has not been reported in wines. The ability of Lactobacillus plantarum NCFB 1752 to produce volatile phenols has previously been studied under laboratory conditions and on synthetic models. In this work, the same strain was studied on near-wine and real wine conditions and with different wine components which have not been previously investigated. Red and white wines were mixed with MRS medium (with pH adjusted to 4.5 and 5% v/v ethanol) at different proportions in order to study their impact on bacterial growth and metabolism. It was found that the presence of wine slows bacterial growth and shifts bacteria metabolism in favour of 4-vinylphenol production instead of 4-ethylphenol. To go further, in other experiments MRS broth was blended with specific wine compounds: fructose, caffeic acid and two tannin fractions with different molecular weights. Results seem to point out the role of phenolic compounds and, to a lesser extent, of fructose, in a shift in volatile phenol metabolism in LAB. On the other hand, caffeic acid enhanced the production of volatile phenols in MRS broth.
URI: http://hdl.handle.net/10400.14/16324
Aparece nas colecções:ESB - Dissertações de Mestrado / Master Dissertations
R - Dissertações de Mestrado / Master Dissertations

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