Food Chemistry

448 8 Food Additives

(8.23)

8.10.6 Lactic Acid

D,L-orL-lactic acid (pK= 3 .86) is utilized as an
80% solution. A specific property of the acid is
its formation of intermolecular esters, providing
oligomers or a dimer lactide:

(8.24)

Such intermolecular esters are present in all lactic
acid solutions with an acid concentration higher
than 18%. More dilute solutions favor complete
hydrolysis to lactic acid. The lactide can be uti-
lized as an acid generator. Lactic acid is used
for improving egg white whippability (pH adjust-
ment to 4.8–5.1), flavor improvement of bever-
ages and vinegarpickled vegetables, prevention of
discoloration of fruits and vegetables and, in the
form of calcium lactate, as an additive in milk
powders.
Lactic acid production is based on synthesis start-
ing from ethanal, leading to racemicD,L-lactic
acid (Formula 8.25) or on homofermenta-
tion (Lactobacillus delbruckii, L. bulgaricus,
L. leichmannii) of carbohydrate-containing raw
material, which generally provides L-but also
D,L-lactic acids under the conditions of fermen-
tation.

CH 3 CHO
HCN
−→CH 3 CHOHCN−→Lactate
(8.25)

8.10.7 Malic Acid

Malic acid (pK 1 = 3 .40; pK 2 = 5 .05) is widely

utilized in the manufacturing of marmalades,

jellies and beverages and canning of fruits and

vegetables (e. g. tomato). The monoesters with

fatty alcohols are effective antispattering agents

in cooking and frying fats and oils.

Malic acid synthesis, which provides the racemic

D,L-form, is achieved by addition of water to

maleic/fumaric acid.L-Malic acid can be syn-

thesized enzymatically from fumaric acid with

fumarase (Lactobacillis brevis, Paracolobactrum

spp.) and from other C sources (paraffins) by fer-

mentation withCandida spp.

8.10.8 Tartaric Acid

Tartaric acid (pK 1 = 2 .98; pK 2 = 4 .34) has

a “rough”, “hard” sour taste. It is used for the

acidification of wine, in fruit juice drinks, sour

candies, ice cream, and because of its formation

of metal complexes, as a synergist for antioxi-

dants. The production of (2R,3R)-tartaric acid

is achieved from wine yeast, pomace, and cask

tartar, which contain a mixture of potassium hy-

drogentartrate and calcium tartrate. This mixture

is first converted entirely to calcium tartrate,

from which tartaric acid is liberated by using

sulfuric acid. Racemic tartaric acid is obtained

by cis-epoxidation of maleic acid, followed by

hydrolysis:

(8.26)

8.10.9 Citric Acid

Citric acid (pK 1 = 3 .09; pK 2 = 4 .74; pK 3 = 5 .41)

is utilized in candy production, fruit juice, ice

cream, marmalade and jelly manufacturing, in

vegetable canning and in dairy products such

as processed cheese and buttermilk (aroma

improver). It is also used to suppress browning

in fruits and vegetables and as a synergetic