Produce Degradation Pathways and Prevention

312 Produce Degradation: Reaction Pathways and their Prevention

TABLE 10.6
Antibrowning Additives

Antibrowning Additive

Mechanisms of Action

(Proposed) Limitations of Use

SO 2 , sulfites, bisulfites Direct inactivating effect on
PPO (binding on protein,
limitation of substrate access to
the active sites, etc.); reduction
of o-quinones; formation of
colorless conjugated
compounds with o-quinones
and blocking of their
subsequent reactions

Health risks, dangerous

especially for asthmatics

Regulation of residual

concentration in food products

Sulfhydryl-containing amino
acids and peptides:
Cystein
N-acetylcysteine
Glutathion

Similar to sulphites:

Direct inactivation of PPO

(probably formation of

stable complexes with

copper); reduction of o-

quinones to o-phenols;

formation of colorless

conjugated compounds

with o-quinones and

blocking of their

subsequent reactions

Cystein and glutathione cause

the unpleasant odor in fruit and

vegetables

High price of treatment

compared with sulphites

(N-acetylcysteine is most

expensive); cysteine when used

in lower pH values can cause

the formation of colored

products (pinkish-red

compounds in cauliflower or

cabbage)

Ascorbic acid and derivatives:
Ascorbic acid and salts
(Ca, Fe, Mg,Na)
Ascorbic acid-2-phosphate
Ascorbic acid-2-
triphosphate
Erythrobic acid and salts
(Na)

Reduction of o-quinones to o-

phenols; very gentle

acidification

Antibrowning effect depends on

the concentration of ascorbic

acid in the reaction; when all

ascorbic acid is oxidized the

browning reaction continues

Carboxylic acids:
Citric
Gluconic
Lactic
Malic
Malonic
Pyruvic
Oxalic
Oxalacetic
Tartaric

Chelating effect binding the

copper (hydroxy acid only);

acidification

Limited efficiency when acids

without chelating effect are

used

EDTA Chelating effect binding the
copper; weak acidification