Malic acid, additive

Liquid chromatography/enzymatic Sugar profile of sucrose, glucose and fructose or amino acids, e.g., o-malic acid Addition of cane and beet invert sugar, addition of D,L-malic acid... 

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. 

In addition to its presence in fmits, S(—)-malic acid has been found in cultures of a variety of microorganisms including the aspergiUi, yeasts, species of Sekrotinia, and Penicillium brevicompactum. Yields of levorotatory malic acid as high as 74% of theoretical have been reported. Iron, manganese, chromium, or aluminum ions reportedly enhance malic acid production. S(—)-Mahc acid is involved in two respiratory metaboHc cycles the Krebs tricarboxylic acid... 

Ca.ndy. Its low melting point and sugar inversion properties make malic acid a desirable acidulant, especially in hard candy products (44,45). Due to their insolubiUty, hard water salts can cause clouding of the finished product. However, because of the higher solubiUty of calcium malate [17482-42-7] relative to alternative acidulants, clarity of the finished product is enhanced. Additionally, in sugar confectionery products where acidulation may exceed 2.0%, malic acid can provide economic benefits. 

Fumaric acid and malic acid [6915-15-7] are produced from maleic anhydride. The primary use for fumaric acid is in the manufacture of paper siting products (see Papermaking additives). Fumaric acid is also used to acidify food as is malic acid. Malic acid is a particularly desirable acidulant in certain beverage selections, specifically those sweetened with the artificial sweetener aspartame [22839-47-0]. 

The purification of j8-poly(L-malic acid) from A o-basiae has been reported involving methanol precipitation of the polymer in the form of the Ca salt [5]. This is possible because a high concentration of CaCOs is present in the growth medium. Unfortunately, the polymer acid is not soluble in aceton thus missing an additional purification step. In our hands, purification of jS-poly(L-malate) from several Aureobasidiae strains was unsatisfactory because of low yields and resisting impurities. 

Chemoenzymatic synthesis of biodegradable poly(malic acid) was performed by lipase-catalyzed polymerization of benzyl /J-malolactone, followed by the debenzylation [72]. The addition of a small amount of /J-PL (17 mol % for the monomer) increased Mw up to 3 x 104 [73]. 

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. 

The reaction mixture for a coupled assay includes the substrates for the initial or test enzyme and also the additional enzymes and reagents necessary to convert the product of the first reaction into a detectable product of the final reaction. The enzyme aspartate aminotransferase (EC 2.6.1.1), for instance, results in the formation of oxaloacetate, which can be converted to malic acid by the enzyme malate dehydrogenase (EC 1.1.1.37) with the simultaneous conversion of NADH to NAD+, a reaction which can be followed spectropho-tometrically at 340 nm ... 

The enzyme fumarase catalyses the stereospecific iram -addition of water to fumaric acid giving (5)-malic acid, and the reverse reaction, the rrans-elimination of water from (S )-malic acid ... 

Uses of MA include unsaturated polyester resins (63%), lubricating oil additives (11%), copolymers (8%), alkenyl succinic anhydrides (5%), malic acid (3%), fiimaric acid (2%), and agricultural chemicals (2%). 

The addition of water to fiimaric acid catalysed by fumarase is a highly stereospecific reaction and malic acid is formed as the sole product (Figure 2.22, X=H). The ammonia lyase 3-methylaspartase catalyses the similar addition of ammonia to yield L-aspartic acid. When uimatural substrates are used in these reactions (X =/= H), less success is experienced. An increasing X-group gives slow reaction rates. 

It is interesting to note that the oxa-analogous Michael addition was reported for the first time in 1878 by Loydl et al. [19] in their work on the synthesis of artificial malic acid, which was five years ahead of the discovery of the actual Michael reaction described first by Komnenos [20], Claisen [21], and later Michael in 1887 [22] as one of the most important methods for C—C bond formation. In continuation of the early work on the oxa-Michael addition [23], the inter- and intramolecular additions of alkoxides to enantiopure Michael acceptors has been investigated, leading to the diastereo- and enantioselective synthesis of the corresponding Michael adducts [24]. The intramolecular reaction has often been used as a key step in natural product synthesis, for example as by Nicolaou et al. in the synthesis of Brevetoxin B in 1989 [25]. The addition of oxygen nucleophiles to nitro-alkenes was described by Barrett et al. [26], Kamimura et al. [27], and Brade and Vasella [28]. 

L-malic acid by addition of water to fumaric acid by fumarase from Brevibacterium... 

The major organic acids in fruits other than grape are usually citric and malic acids (Table III). However, quinic acid, in addition to citric and malic acids, was a principal acid in peaches (71, 72). The main acid... 

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). 

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