Page 405 - Biosystems Engineering

382 Cha pte r T h i r tee n

unsaturated fatty acids involves hydrogen abstraction at the allylic
carbon to produce delocalized three-carbon allylic radicals.

Termination Phenolic substances (antioxidants) function as free-
radical acceptors and could terminate free radicals at the initiation
stage. Hindered phenolics such as BHA, BHT, TBHQ, EQ, and
tocopherols, as well as polyhydroxy phenolics like propyl gallate,
are primary antioxidants that delay or inhibit the initiation step by
reacting with a lipid free radical or by inhibiting the propagation
step by reacting with the peroxy or alkoxy radicals. Thymol, a phe-
nolic compound obtained from an extract of the spice ajowan, also
actively prevents further oxidation in the glycerides, which was
suggested by Nag et al. 22
Some compounds contribute to antioxidant defense by chelating
transition metals and preventing them from catalyzing the produc-
tion of free radicals in the cell. Particularly important is the ability to
sequester iron, which is the function of iron-binding proteins such as
20
transferrin and ferritin. Selenium and zinc are commonly referred to
as antioxidant nutrients, but these chemical elements have no anti-
oxidant action themselves and instead are required for the activity of
some antioxidant enzymes. 20

13.5.2 Functions of Antioxidants
Antioxidants mixed with food materials have the potential to

1. Control damaging free radicals.
2. Minimize the effects of aging.
3. Help control fatty deposits in the arteries and maintaining
elasticity of the veins and good circulation.
4. Helps to relieve localized oxidative stress and also promote
healthy joint cells.
5. Although antioxidants may not cure cancer, much research
has been done, and is still continuing, regarding the role of
antioxidants in the prevention and alleviation of cancer.
6. It can help boost the immune system and clear the blood.
7. Promotes tissue growth and helps prevent destruction of
DNA. Antioxidants are also indicated to assist with memory
loss.
8. Oxidation processes can hamper wound healing, and because
antioxidants will help control this, better healing should be
promoted and the immune system boosted in general, which
will help to prevent infections.
9. Assist in free-radical scavenging.