2009_Book_FoodChemistry

448 8 Food Additives
8.10.6 Lactic Acid
(8.23)
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 synthesized
enzymatically from fumaric acid with
fumarase (Lactobacillis brevis, Paracolobactrum
spp.) and from other C sources (paraffins) by fermentation
with Candida spp.
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 utilized
as an acid generator. Lactic acid is used
for improving egg white whippability (pH adjustment
to 4.8–5.1), flavor improvement of beverages
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 starting
from ethanal, leading to racemic D,L-lactic
acid (Formula 8.25) or on homofermentation
(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 fermentation.
CH 3 CHO −→ HCN CH 3 CHOHCN −→ Lactate
(8.25)
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 antioxidants.
The production of (2R,3R)-tartaric acid
is achieved from wine yeast, pomace, and cask
tartar, which contain a mixture of potassium hydrogentartrate
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:
8.10.9 Citric Acid
(8.26)
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