Food Chemistry

3.7 Changes in Acyl Lipids of Food 219

ties are of importance in the use of BHA, TBHQ
and BHT in food processing. All three antiox-
idants are steam distillable at higher tempera-
tures. Utilization of antioxidants is often regu-
lated by governments through controls on the use
of food additives. In North America incorporation
of antioxidants is permitted at a maximum level
of 0.01% for any one antioxidant, and a max-
imum of 0.02% for any combination. The regu-
lations related to permitted levels often vary from
country to country.
The efficiency of an antioxidant can be evaluated
by a comparative assay, making use of an “antiox-
idative factor” (AF):

AF=IA/I 0 (3.91)

where IA=oxidation induction period for a fat or
oil (cf. 3.7.2.1.1) in the presence of an antioxidant
and I 0 =oxidation induction period of a fat or oil
without an antioxidant.
Hence, the efficiency of an antioxidant increases
with an increase in the AF value. As illustrated
by the data in Table 3.41, BHA in comparison
with BHT shows a higher efficiency in a lard sam-
ple. This result is understandable since in BHT
both tertiary butyl substituents sterically hinder
the reaction with radicals to a certain extent (re-
action 1 in Fig. 3.35). The effect on antioxidants
depends not only on the origin of fat or oil but,
also, on the processing steps used in the isola-
tion and refining procedures. Hence, data in Ta-
ble 3.41 serve only as an illustration.
BHA and BHT together at a given total concen-
tration are more effective in extending shelf-life
of a fat or oil than either antioxidant alone at the
same level of use (Table 3.41).
To explain this, it is suggested that BHA, by
participating in reaction 1 (Fig. 3.35), provides

Table 3.41.Antioxidative factor (AF) values of some
antioxidants (0.02%) in refined lard

Antioxidant AF Antioxidant AF

d-α-Tocopherol 5 Octyl gallate 6
dl-γ-Tocopherol 12 Ascorbyl palmitate 4
BHA 9 .5BHAand
BHT 6 BHTa 12

aEach compound is added in amount of 0.01%.

a phenoxy radical (I):

(3.92)

which is then regenerated into the original

molecule by rapid interaction with BHT:

(3.93)

On the other hand, the phenoxy radical (II) de-

rived from BHT can react further with an addit-

ional peroxy radical:

(3.94)

Propyl gallate (PG) increases the efficiency

of BHA, but not that of BHT. Ascorbyl palmitate,

which is by itself a rather weak antioxidant,

substantially sustains the antioxidative activity of

γ,d,l-tocopherol.

3.7.3.2.3 Synergists..............................................

Substances which enhance the activity of antiox-

idants are called synergists. The main examples

are lecithin, amino acids, citric, phosphoric, cit-

raconic and fumaric acids, i. e. compounds which