Page 408 - Biosystems Engineering

Extraction, Refining, and Stabilization of Edible Oils 385

Time of oxidation (hr)
0 1 2 3 4 5 6 7
120

Peroxide volue (milliequivalent peroxide/kg sample)
100

80

60

40

20

0
25 50 75 100 125 150 175 200
Temperature (°C)
FIGURE 13.4 Peroxide values of fl axseed oil at different temperatures in the
presence of air: without antioxidant (○); with antioxidant ( ). Peroxide values of
fl axseed oil at different times in the presence of air at 30°C: without antioxidant
( ); with antioxidant ( ).

antioxidants, such as, tocopherols, ascorbic acid, and β-carotenes. 28
Black tea and green tea also have very good antioxidant potential. 29
Extracts from grapes were also shown to exert good antioxidant
activities, which proved beneficial in reducing the incidence of car-
diovascular disease. 28

13.6 Measuring Antioxidant Activities
The efficacy of synthetic and natural antioxidants is measured by
monitoring the oxidative stability of oil. After the sample is oxidized
under standard conditions, the extent of oxidation is measured by
chemical, instrumental, or sensory methods.
A variety of methods used to assess antioxidant activities includ-
ing the following.