Search results for "Malolactic Fermentation"
showing 10 items of 78 documents
Effect of micro-oxygenation on the evolution of aromatic compounds in wines: Malolactic fermentation and ageing in wood
2009
Abstract The effect of micro-oxygenation on the aromas of two varietal wines (Tempranillo and Cabernet Sauvignon) when alcoholic fermentation is complete was examined. Several factors, such as whether malolactic fermentation (MLF) took place in barrels or stainless steel vats and ageing time in oak barrels, were taken into account. Major aroma components were studied using GC-FID and minor compounds were studied by GC–MS analysis before and after MLF and after 4 and 8 months of maturation in oak barrels. Sensorial analysis was performed to describe and quantify the different wine notes. Micro-oxygenation affects different compounds but the effect depends to a great extent on the grape varie…
Metabolism of Sugars and Organic Acids by Lactic Acid Bacteria from Wine and Must
2008
Heterofermentative lactic acid bacteria (LAB) which are common in plant associated environments are found also in grape must and wine. In this environment specific strains predominate which are adapted to the low pH and high alcohol contents. Must and wine harbour the strictly heterofermentative Oenococcus oeni, Lactobacillus hilgardii and Lactobacillus brevis, and the facultatively heterofermentative Lactobacillus plantarum and Lactobacillus pentosus (Rodas et al. 2005). In addition homofermentative lactic acid bacteria of the Pediococcus group are able to grow in wine and must, but are normally found at low cell densities. The growth of lactic acid bacteria in wine depends largely on suga…
Saccharomyces cerevisiae-Oenococcus oeni interactions in wine: current knowledge and perspectives.
2003
Winemaking can be summarized as the biotransformation of must into wine, which is performed principally by Saccharomyces cerevisiae strains during the primary or alcoholic fermentation. A secondary fermentation, the so-called malolactic fermentation (MLF) is a biodeacidification that is often encouraged, since it improves wine stability and quality. Malolactic fermentation usually occurs either spontaneously or after inoculation with selected bacteria after alcoholic fermentation. The main organism responsible for MLF, the lactic acid bacterium Oenococcus oeni, develops in physicochemically harsh conditions, which may lead to MLF failure. Furthermore, yeast that ferment must before or toget…
Typical metabolic traits of two Oenococcus oeni strains isolated from Valpolicella wines
2004
Aims: Physiological comparison of two indigenous Oenococcus oeni strains, U1 and F3 isolated in the same area (Valpolicella, Italy) in order to select a performant starter for MLF in wine. Methods and Results: Growth rate, sugar and malate metabolism in FT80 media at pH 5·3 and 3·5 were analysed. The amount of total protein synthesized and the level of expression of the small Hsp Lo18 were evaluated by radiolabelling and immunodetection experiments after heat (42°C), acid (pH 3·5) and ethanol (12% v/v) stresses. Strain U1 showed significantly lower specific growth rate and growth yield in acid conditions than strain F3. However, strain U1 had a higher malate consumption capacity at pH 3·5…
The effects of freezing and freeze-drying ofOenococcus oeniupon induction of malolactic fermentation in red wine
2000
Summary The use of Oenococcus oeni starter cultures for the induction of malolactic fermentation (MLF) in wine permits control over the timing of the process and the quality of the wine. Successful inoculation of bacterial starter cultures into wine depends on the selection of suitable strains and on the preparation and conservation of those cultures. Medium for Leuconostoc oenos (MLO) is the best medium for easy and rapid growth of O. oeni cultures under laboratory controlled conditions for isolation and identification. However, this study showed that O. oeni cells inoculated in MLO failed to induce MLF in wine while cells grown in Medium of Preculture (MP) or wine, stored at −20 °C or fre…
Biogenic amine production by lactic acid bacteria, acetic bacteria and yeast isolated from wine
2007
Abstract Biogenic amines are undesirable in all foods and beverages because if consumed at too high concentration, they may induce food-borne intoxications. The biogenic amine production by 155 strains of lactic acid bacteria, 40 strains of acetic bacteria and 36 strains of yeast isolated from wine were analysed in wine, grape must and synthetic media by HPLC. We did not observe biogenic amine production by acetic bacteria and yeast; however, we found production of histamine, tyramine, phenylethylamine and putrescine by LAB. A correlation of 100% was observed between biogenic amine production in synthetic medium and wine and between activity and presence of gene. With the results expose in …
Research report: Interactions between toxic fatty acids for yeasts and colloids, cellulose and yeast ghost using the equilibrium dialysis method in a…
1997
Abstract The capacity of different materials (yeast walls, colloids and cellulose) to bind octanoic acid and decanoic acid was investigated in a model wine. The interactions between these toxic fatty acids and the soluble or insoluble material was shown using the equilibrium dialysis method. Yeast walls adsorb decanoic acid and to a lesser extent octanoic acid which confirms previous results. In comparison, colloids from both grape or yeast weakly bind decanoic acid and do not significantly bind octanoic acid. No interactions between cellulose and fatty acid were observed. According to the yeast wall composition, lipids seem to play a key role for binding. With regards to our results, the e…
Stress Responses of Oenococcus oeni
2011
Oenococcus oeni is an alcohol-tolerant, acidophilic lactic acid bacterium responsible for malolactic fermention in wine. The stress responses of O. oeni have been studied at both the molecular and physiological levels. Genes encoding stress proteins mainly belong to the CtsR regulon. Other regulation mechanisms seem to coexist in O. oeni and may correspond to posttranscriptional regulation. Maintenance of the cell membrane integrity under stress conditions seems to be a prerequisite for survival in wine. The active cell response to protect membrane function under stress conditions requires changes in fatty acid composition and involves stress proteins. Various solute transporters and energy…
Malolactic fermentation in white wines
2022
Abstract Malolactic fermentation (MLF) is an important process in wine production and involves the bioconversion of malic acid into lactic acid and CO2. However, many other biochemical reactions occur simultaneously, and several other grape must and wine compounds are also modified besides malic acid. Some can improve quality, while others may be detrimental to sensory quality or health. Among them, there are the synthesis of carbonyl compounds, esters, monoterpenes, volatile phenols, acetamide or mousy odor, methanethiol, dimethyl disulfide, methionol, 3-(methylsulfanyl) propionic acid, citrulline, or biogenic amines. The role of MLF in winemaking is triple: reducing the acidity of the win…
A novel culture medium for Oenococcus oeni malolactic starter production
2015
Malolactic fermentation is essential in wine quality. One of the strategies used to control this fermentation involves the inoculation of selected lactic acid bacteria, mainly Oenococcus oeni. Laboratory media usually produce large amounts of biomass, but with little or no adaptability to wine. We propose a culture medium to grow and pre-adapt O. oeni cells, and the steps to scale-up production. To achieve this objective, 27 different media were tested. All contained grape must and wine, and nutritional supplements in order to benefit bacterial growth. Those media contained different ethanol levels, pH values, and grape must concentrations. The optimized culture medium named Oenococcus Prod…