Page 407 - Biosystems Engineering

384 Cha pte r T h i r tee n

3. These natural antioxidants (not synthetic chemical antioxi-
dants) are identical to the food, which people ate for hun-
dreds of years.
4. These antioxidants not only stabilize food but also add nutri-
tional value to foods, such as ginger rhizome, β-carotene,
ascorbic acid from lemons, tocopherol, ajowan extracts, and
cereal extracts.

There is a continuing need for widely usable natural antioxidants.
In addition to having the same safety and technological requisites of
synthetic compounds, the natural antioxidant additive should also
originate from an abundant and inexpensive vegetable matrix, be
produced by an economic and compatible technology, and be effective.
Most natural antioxidants are phenolic compounds (with the
exception of the tocopherols) that contain ortho-substituted active
groups, whereas synthetic antioxidants (with the exception of gal-
lates) are para substituted. The most potent sources of natural anti-
20
oxidants—spices and herbs—have been used for hundreds of years
not only for flavoring but also for their food-preserving abilities.
22
Nag et al. observed that an azoan extract contained thymol as an
active ingredient, which acted as a natural antioxidant suitable for
the stabilization of oil (Fig. 13.4).
23
Hu et al. determined the antioxidant properties of the whole
leaves of aloe vera (Aloe barbadensis Miller) compared to BHT and α-
tocopherol using the DPPH radical scavenging method. The antioxi-
dant activity of aloe vera extracts and reference compounds follows
this order: 3-year-old aloe vera > BHT > 4-year-old aloe vera >α-
tocopherol > 2-year-old aloe vera. The 3-year-old extract exhibited
the strongest radical scavenging activity of 72.19 percent higher than
that of BHT at 70.52 percent and α-tocopherol at 65.20 percent. These
data suggest that the stage of development of aloe vera dramatically
affects its composition and antioxidant activity. Nag observed that
24
the antioxidant properties of capsicum in flaxseed oil are due to the
presence of compound N-(4-hydroxy-3-methoxy-benzyl)-alkylamide.
Phenolics in vegetable oils may generally exert a beneficial effect
on their oxidative stability. As an example, sesame oil, which contains
sesamine, sesaminal, and sesamole, is known to be highly stable. 25
Similarly, olive oil is a rich source of tyrosols and hydroxytyrosol, and
these compounds are known to possess good antioxidant activity. 26
26
Nag et al. recovered natural antioxidants from olive oil mill waste-
water and studied the oxidative stabilization of lard.
Studies on ginger extracts were also found to have higher anti-
27
oxidant activity than α-tocopherol. In Nigeria, ginger is one of the
few commercial spices produced for local consumption that is used
in bread, oil, essences, pastries, and biscuits. In addition to spices
and herbs, teas, vegetables, and fruits are also good sources of