Malic acid effectiveness

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. 

The optical activity of malic acid changes with dilution (8). The naturally occurring, levorotatory acid shows a most peculiar behavior in this respect a 34% solution at 20°C is optically inactive. Dilution results in increasing levo rotation, whereas more concentrated solutions show dextro rotation. The effects of dilution are explained by the postulation that an additional form, the epoxide (3), occurs in solution and that the direction of rotation of the normal (open-chain) and epoxide forms is reversed (8). Synthetic (racemic) R,.9-ma1ic acid can be resolved into the two enantiomers by crystallisation of its cinchonine salts. 

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. 

Hand in hand with this research on finding a suitable carboxyUc acid chemical for cross-linker has been the search for an economical catalyst system. The catalyst found to be most effective for the esterification reaction was sodium hypophosphite (NaH2P02). This material was also costiy and out of range for the textile industry. Because weak bases function as catalyst, a range of bases has been explored, including the sodium salts of acids such as malic acid. 

In this paper, we prepared LaMnOa perovskite-type oxides using the malic acid method and investigated their physical properties. It has been also investigated the effect of partial substitution of metal iorrs into La and Mn sites and the reaction conditions on the activity for the combustion of soot particulates. 

J. Gerke, W. Romer, and A. Jungk, The excretion of citric and malic acid by proteoid roots of Liipinus aihus L. effects on soil solution concentrations of phosphate, iron, and aluminium in the proteoid rhizosphere samples of an Oxisol and a Luvi.sol. Z. Pktnzenernaehr. Bodenk. I57 2S9 (1994). 

Addition of salts, adds and bases tend to make the laevo-rotary acid more dextro-rotary. With rising temperature, the pure add and also the solutions become more laevo-rotary. These changes cannot be due to dectrolytic dissociation, because the effect of hydrochloric acid is quite marked up to rdatively high concentrations and it would take relatively little acid to force back the dissociation of malic acid to a negligible value. Another reason is that we get a similar change with the concentration with malic ester in alcoholic solution. 

The change with the concentration cannot be due to the reversible formation and decomposition of a lactone of the ordinary type because we get the effect with ethyl malate as well as with malic add. The change cannot be due to a reversible conversion of laevo-malic acid into dextro-malic add, because then a solution of equivalent amounts of dextro- and laevo-malic acids would become optically active on addition of salts, adds and bases. Hydrochloric add or sodium hydroxide imparts no activity to a solution of d/-malic add. The changes on adding electrolytes to a solution of dextro-malic add are equal and opposite in sign to the changes in laevo-malic acid under the same conditions. 

Aside from the multifaceted chemical conversions, there are sources to develop into industrially viable microbial conversions. 1,2,4-Butanetriol, for example, used as an intermediate chemical for alkyd resins and rocket fuels, is currently prepared commercially from malic acid by high-pressure hydrogenation or hydride reduction of its methyl ester. In a novel environmentally benign approach to this chemical, wood-derived D-xylose is microbially oxidized to D-xylonic acid, followed by a multistep conversion to the product effected by a biocatalyst specially engineered by inserting Pseudomonas putida plasmids into E. coli ... 

Since parasorbic acid was previously isolated by steam distillation of the juice of mountain ash berries (.S), we steam distilled a sample of the cranberry leaf extract, but obtained little 2. The literature reports that before the ash berry juice was distilled, it was treated with calcium hydroxide to precipitate malic acid. Tschesche later showed that such treatment followed by acidification converted the glucoside of parasorbic acid, into the free acid (lactone), 2, (9). This base treatment effects a B-ellmination of the glucose fragment. In the absence of this base treatment, no free parasorbic acid was liberated from the berries. 

Fig. 23. Effect of cation used for the adjustment of modifying pH on EDAs of MRNis (O) modified with (R.R)-TA, pH 5.0, 0 C ( ) modified with (R,R)-TA, pH 5.0, 100 C ( ) modified with (R)-malic acid, pH 5.0,0 C. Reaction conditions MAA (neat), 60 C, 90 kg/cm2.

N.A. Rosa canina L. R. damascena Mill. R. gallica L. Malic acid, citric acids, pectin, geraniol, citronellol, vitamins , complex.102 07 60 Astringent, mild diuretic and laxative effect. Excellent source of vitamin C when it s fresh. 

The M-L fermentation causes several beneficial changes in these high acid, low pH wines, among them a decrease in acidity and an increase in the pH. The effect of the conversion of malic acid to lactic acid on the total acidity of native and hybrid wines is shown in Table VIII. The total acidity decreased to the range 0.6-0.8 gram/100 ml which is considered desirable in these native wines. This conversion is of particular significance in regard to flavor since lactic is less sour than malic at the same titratable acidity and the same pH (63). 

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. 

A slight stimulatory effect on cell yield might have evolutionary significance in establishing primeval strains however, from gross observation, it is not very interesting. Of greater interest is a rather spectacular effect of malic acid on end product formation. 

Figure 2. Effect of low pH on growth of Leu-conostoc oenos ML 34 without malic acid (O, ) and with 0.2% la-malic acid (A).

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