Malo-lactic fermentation

Clarification, decrease foaming, promote malo-lactic fermentation Soy sauce, fish sauce, bouillon, dehydrated soups, gravy powders, processed meats, special diets Tenderization, recover proteins from bones... 

TABLE 4.4 Concentrations of selected volatile compounds prior to malo-lactic fermentation in Cabernet Sauvignon and Tempranillo wines data from Hernandez-Orte... 

The effects of initial amelioration are most readily discernible in the alcohol and acid content of the new wine. Instead of alcohol concentrations of 7-10%, the new wines contain 12-13%. The effect of partial amelioration on acid content is illustrated in Table VIII. The total acid values of the new wines are the result both of partial amelioration and deposition of tartrates during the alcoholic fermentation. Even so, most of the acid values remain high, and additional techniques must be employed to reduce the acid content to an acceptable level. Processes currently used include further amelioration, blending several native varieties and hybrids of the same or different vintages, blending a small proportion of low-acid vinifera wine, and encouraging the malo-lactic fermentation. Treatment with calcium carbonate is permitted by federal regulations and occasionally is used to reduce natural acidity in the absence of a malo-lactic fermentation. 

As a result of the high natural acidity in the native and hybrid grapes, the malo-lactic (M-L) fermentation is of particular significance in the production of quality wine from this fruit. A survey of New York State wines in 1964 (60) revealed that 45% had undergone the M-L fermentation, including 68% of the reds and 27% of the whites. This... 

During an extended period of study of the malo-lactic fermentation in one New York State winery, a pattern has emerged. In this operation all grapes received during a vintage were pressed immediately (either cold or hot press), the must was cooled to 20°-21°C, and sulfur dioxide was added only to white must to achieve a free S02 concentration of 20 ppm or less. The must was inoculated with yeast at the completion of the days pressing. 

The bacterial conversion of malic acid to lactic acid and carbon dioxide has been recognized since 1890 and is referred to as the malo-lactic fermentation. This conversion has been promoted under controlled conditions in the cooler viticultural regions of the world where grapes mature with excessive amounts of malic acid which causes taste imbalance... 

Rankine, B. C., Influence of Yeast Strain and Malo-lactic Fermentation on... 

Fixed Acid. The total acid (as tartaric) less the volatile acidity (as tartaric) is the fixed acidity. It is useful to make this calculation when one suspects activity of acid-reducing bacteria, as in the malo-lactic fermentation. 

Malic Acid. This is seldom determined quantitatively in winery practice. However, qualitative paper chromatography is often done to follow malo-lactic fermentation. Using n-butyl alcohol and formic acid (80), the Rf values are tartaric 0.28, citric 0.45, malic 0.51, ethyl acid tartrate 0.59, lactic acid 0.78, succinic 0.78, and ethyl acid malate 0.80. 

Practical and fundamental aspects of malo-lactic fermentation are given. Conditions which winemakers can use for better control of the fermentation, including detailed procedures for inoculation with Leuconostoc oenos ML 34 and for inhibition with fumaric acid, are presented. New information on the role of malic acid decarboxylation in bacterial metabolism and on the enzymatics of malic acid decarboxylation are reviewed. The malic acid decarboxylation seems to involve two pathways a direct decarboxylation of malic to lactic acid with NAD as a coenzyme and a concurrent but small oxidative decarboxylation to pyruvic acid and NADH. How these pathways can bring about the marked stimulation of bacterial growth rate by the malo-lactic reaction and their negligible effect on growth yield are discussed. 

San Joaquin Valley (Calif.) table wines (wines with less than 14% ethanol) represent about 80% of wine production in California. In two large wineries there, the malo-lactic fermentation is inhibited and does... 

Desirability of Malo-Lactic Fermentation. Three important aspects of malo-lactic fermentation must be considered in appraising its desirability deacidification, bacteriological stability, and increased flavor complexity (4). 

In addition to malo-lactic fermentation, another biological method for deacidification of high-acid must is to use malic acid-metabolizing Schizo-saccharomyces yeast for the alcoholic fermentation. Benda and Schmidt (33) have selected strains of these yeasts which produce wines with no off-flavors. In using some of these same strains we have also been able to make wines of sound character (18). 

Bacteriological Stability. The bacteriological stability provided by malo-lactic fermentation is its most important attribute. Wines aged before bottling (and which are susceptible to the fermentation) will nearly always be fermented during the first or second year. With proper post-fermentation treatment, these wines can be safely bottled without fear of further bacterial attack. We have seen no instances where a second bacterial fermentation has occurred once the malo-lactic fermentation was completed unless additions had been made to the wines or they had been blended. 

The highly flavorable compound diacetyl is an important by-product of lactic acid bacterial fermentation. The mechanism of its formation has recently been unraveled (35). Diacetyl (measured as diacetyl rather than as diacetyl plus acetoin) is present in higher concentrations in wines with malo-lactic fermentation (cf. Ref. 36). At approximately threshold levels, this compound might contribute favorably to the flavor of wine (7) since increased complexity has been shown to enhance the quality of wine (37). 

Absolute stabilization may not be required. We have stated that the factors which influence the malo-lactic fermentation are qualitative,... 

Fumaric Aero Inhibition. Another means of preventing malo-lactic fermentation is to add fumaric acid after alcoholic fermentation is complete (45, 46, 47,48). The inhibition is relative and its extent is dependent on the amount added. The susceptibility to fumaric acid is also dependent on the strain of malo-lactic bacteria tested (49). However, we know of no case where fumaric acid addition at the levels suggested by Cofran and Meyer (45) (about 0.05%) did not delay malo-lactic fermentation under normal winemaking conditions. This includes several experiments from our pilot winery (50). Nevertheless, we have not been hasty to recommend the use of fumaric acid as an inhibitor because 1) of the difficulty in solubilizing the acid in wine 2) we do not know the mechanism of action of its inhibition [Pilone (47, 48) has shown that the bacteria metabolize low levels of fumaric acid to lactic acid but, at inhibitory levels at wine pH, the acid is bactericidal] and 3) of the desirability of minimizing the use of chemical additives. 

The efficiency of using starter cultures is in dispute. Rankine and Pilone (54) have found no consistency in the rate of completion of malo-lactic fermentation in relation to the amount of inoculum used or the time of addition. Indeed we, and others, also have found from time... 

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