Malolactic fermentation acidity

The following factors participate in the control of malolactic fermentation acidity (Section 6.2.1), temperature (Section 6.2.4), aeration (Section 6.2.5), vatting time and sulfiting (Section 6.2.2). 

In addition to alcohoHc fermentation, a malolactic fermentation by certain desirable strains of lactic acid bacteria needs to be considered. Occasionally, wild strains produce off-flavors. Malolactic fermentation is desirable in many red table wines for increased stabiUty, more complex flavor, and sometimes for decreased acidity. Selected strains are often added toward the end of alcohoHc fermentation. AH the malic acid present is converted into lactic acid, with the resultant decrease of acidity and Hberation of carbon dioxide. Obviously this has more effect on the acidity the more malic acid is present, and this is the case in wine from underripe, too-tart grapes. Once malolactic fermentation has occurred, it does not recur unless another susceptible wine is blended. 

Other Food Uses. Jellies, jams, and preserves use malic acid to balance flavor and adjust pH for pectin set. Canned fmits and vegetables employ malic acid in combination with ascorbic acid to produce a synergistic effect that aids in the reduction of browning. Wine and cider producers use malic acid in malolactic fermentation to provide bouquet and for pH adjustment. 

The sugars in fruits such as grapes are feimented by yeasts to produce wines. In winemaking, lactic acid bacteria convert malic acid into lactic acid in malolactic fermentation in fruits with high acidity. Acetobacter and Gluconobacter oxidise ethanol in wine to acetic acid (vinegar). 

Malleability, of silver, 22 641 Malleable irons, 14 522 Malolactic fermentation, 26 313—314 Malonic acid, 23 419 Malononitrile, 8 174 Malting, 75 523. See also Malts barley cleaning and grading for, 75 525-527... 

Figure 8.9—Separation of the main organic acids in white wine. Malic and lactic acids are indicators of the classical malolactic (fermentation process application note from TSP).

In the fermentative process, the first step is due to yeasts which transform sugars to alcohol (alcoholic fermentation). This is followed by a second fermentation step (malolactic fermentation), which corresponds to the transformation of L-malic acid to L-lactic acid. 

Malolactic fermentation (MLF) is an important secondary fermentation that occurs in many wines generally about 2-3 weeks after completion of the alcoholic fermentation. Lactic acid bacteria, principally Oenococcus oeni (formerly Leuconostoc oenos) are responsible for this fermentation. 

FIGURE 4.21 H NMR spectra (400 MHz) of time course evolution of red wine in alcoholic and malolactic fermentations for grape red must (pH 3). Peaks 1, ethanol 2, ethanol satellites 3, lactic acid 4, acetic acid 5, succinic acid 6, malic acid 7, 2,3-butanediol 8, proline 9, alanine. (From Avenoza et at, 2006.)... 

Avenoza, A., Busto, J. H., Canal, N., and Peregrina, J. M. (2006). Time course of the evolution of malic and lactic acids in the alcoholic and malolactic fermentation of grape must by quantitative 1H NMR (qHNMR) spectroscopy. J. Agric. Food Chem. 54, 4715-4720. 

Together with proteins and peptides, amino acids constitute the main components of the nitrogenous fraction of musts and wines. They are also the most studied and best known nitrogenated components in wines. Free amino acids in musts are of paramount importance. They constitute a source of nitrogen for yeasts in alcoholic fermentation, for lactic acid bacteria in malolactic fermentation, and can also be a source of aromatic compounds (Kosir and Kidric, 2001). In certain cases, some amino acids... 

Usually, after alcoholic fermentation, the wine undergoes malolactic fermentation, induced primarily by Oenococcus oeni. Not only can this lactic acid bacterium convert L-malic acid into L-lactic acid but also it is involved in many other transformations fundamental to Amarone quality. 

De-acidification blending higher acid wine for acidification. Malolactic fermentation for de-acidification Tolerated tartaric, malic, citric and tumaric acids (from natural sources if suppliers exist) according to BATF regulations. Calcium carbonate (max. 75 p.p.m.) and cream of tartar from natural sources, if they exist... 

Malolactic fermentation (MLF) in wine is by definition the enzymatic conversion of L-malic acid to L-lactic acid, a secondary process which usually follows primary (alcoholic) fermentation of wine but may also occur concurrently. This reduction of malic acid to lactic acid is not a true fermentation, but rather an enzymatic reaction performed by lactic acid bacteria (LAB) after their exponential growth phase. MLF is mainly performed by Oenococcus oeni, a species that can withstand the low pFi (<3.5), high ethanol (>10 vol.%) and high SO2 levels (50 mg/L) found in wine. More resistant strains of Lactobacillus, Leuconostoc and Pediococcus can also grow in wine and contribute to MLF especially if the wine pH exceeds 3.5 (Davis et al. 1986 Wibowo et al. 1985). The most important benefits of MLF are the deacidification of high acid wines mainly produced in cool climates, LAB contribute to wine flavour and aroma complexify and improve microbial sfabilify (Lonvaud-Funel 1999 Moreno-Arribas and Polo 2005). 

Of all the metabolic activities that lactic acid bacteria can carry out in wine, the most important, or desirable, in winemaking is the breakdown of malic acid, but only when it is intended for this to be removed completely from the wine by malolactic fermentation. Although the breakdown of malic and citric acids has considerable consequences from a winemaking perspective, it is also evident that lactic acid bacteria metabolise other wine substrates to ensure their multiplication, including sugars, tartaric acid, glycerine and also some amino acids. We will now describe some of the metabolic transformations that have received most attention in the literature, or which have important repercussions in winemaking. 

As well as fruity and buttery aromas, MLF has also been associated with other characteristic aromas such as floral, roasted, vanilla, sweet, woody, smoked, bitter, honey, etc. (Flenick-Kling 1993 Sauvageot and Vivier 1997). However, further studies are required to be able to relate the wine characteristics that are modified during malolactic fermentation with the production and/or degradation of a specific chemical compound by wine lactic acid bacteria. With this information, the winemaker can choose the best strain of lactic acid bacteria to obtain wine with a specific aroma or flavour. 

Pozo-Bayon, M.A., Alegrfa E.G., Polo, M.C., Tenorio, C., Martin-Alvarez, P.J., Calvo de la Banda, M.T., Ruiz-Larrrea, R, Moreno-Arribas, M.V. (2005). Wine volatile and amino acid com-posidon after malolactic fermentation Effect of Oenococcus oeni and Lactobacillus plantarum starter cultures. J. Agric. Food Chem., 53, 8729-8735. 

Malolactic fermentation usually occurs in sobretablas wine as a result, the wine incorporated into the aging system contains no appreciable concentrations of malic acid. The decrease in tartaric acid contents during biological aging of the wine is a result of crystal precipitations. 

A.2.2 Evolution of Free Amino Acids During Malolactic Fermentation. 166... 

On the other hand, other studies focused on O. oeni amino acid requirements for growth and malolactic fermentation in several growth media (Tracey and Britz 1989). Remize et al. (2006) determined the essential amino acids for the growth of five different strains of Oenococcus oeni. These amino acids corresponded to glutamic acid, methionine, phenylalanine, serine and tyrosine for all the strains studied. They also found that the amino acids valine, leucine, tryptophan, isoleucine, histidine and arginine were essential or necessary for the strains studied, but that the amino acids alanine, glycine and proline were not essential. 

Commercial 0. oeni strains are selected for their oenological parameters, including the absence of amino acid decarboxylases. According to the in vitro studies done by Moreno-Arribas et al. (2003), none of the four commercial malolactic starter cultures tested could produce histamine, tyramine or putrescine. Martln-Alvarez et al. (2006) also compared inoculation with spontaneous malolactic fermentation in 224 samples of Spanish red wine. They found that inoculation with a commercial starter culture of lactic acid bacteria could reduce the incidence of biogenic amines compared to spontaneous malolactic fermentation in wines. Starter cultures could eliminate indigenous bacteria, or could possibly degrade the biogenic amines produced by the undesirable strains. 

Moreno-Arribas and Lonvaud-Funel (1999). Moreno-Arribas et al. (2000) isolated and identified a number of tyramine-producing lactic acid bacteria in wine that had undergone malolactic fermentation all belonging to the lactobacilli. Tyrosine decarboxylase was then purified (Moreno-Arribas and Lonvaud-Funel 2001) and the corresponding gene was purified and sequenced (Lucas and Lonvaud-Funel 2002 Lucas et al. 2003). As far as the literature suggests, no tyramine-producing 0. oeni strain has yet been reported, with the exception of one strain (O. oeni DSM 2025) that was shown to be able to produce tyramine in a laboratory medium (Choudhury etal. 1990). 

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