Antioxidants and Shelf Life of Foods - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 191

4

d

e

3

a

f

c

b

2

1

4 5 6 7 8 9 10

Concentration (mM)

FIGURE 6.15 Relationship between the concentration of catechins corrected by the anti-
oxidative activity of the respective catechin ([C]) and the antioxidative activity of the tea
{(R′ p /R p ) -1 } for (a) Matcha, (b) Gvokuro, (c) Sen-cha (H), (d) Kamairi-cha, (e) Sen-cha (L)
and (f) Ban-cha. (Adapted from Kumamoto and Sonda. 81 With permission.)

A NTIOXIDANT P OTENTIAL

Widespread interest in natural sources of antioxidants has generated an enormous
amount of research to assess the antioxidant potential of novel sources of phenolic
compounds as well as recognize the inherent activity of commonly consumed foods.
This has been combined with the role of lipid peroxidation in human health through
modulation with food sources of antioxidants. The average daily consumption of
food phenolics has been reported to range from 25 mg to 1 g. 31,80 Using an oxygen
electrode, Kumamoto and Sonda 81 evaluated the antioxidant activity of 25 different
kinds of tea. They correlated antioxidant activity with the amount of the four major
tea catechins (epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin
gallate). A correlation (r) of 0.6402 indicated that catechins contributed significantly
to the antioxidant activity of green tea ( Figure 6.15 ). However, the intercept at
regression line was greater than 1, suggesting other compounds must also be involved
such as other polyphenols as well as vitamin C.
Wanasundra and Shahidi 82 compared different flavonoids with commercial anti-
oxidants BHA, BHT, and TBHQ on the stability of marine oils during storage at
65°C. The synthetic and natural antioxidants were added to refined, bleached, and
deodorized sea blubber and menhaden oils at equivalent concentrations of 200 ppm
and for

-tocopherol, 500 ppm. In the case of sea blubber oil, added rutin, kaemferol,
quercetin, morin, and myrcetin proved more effective than

α

-tocopherol, BHA, and
BHT in extending the induction period. However, myricetin proved to be the most

α