Effect of hydrothermal treatments on free radical scavenging potential of selected green vegetables

The effect of hydrothermal treatments, viz. covered lid cooking (CLC), microwave cooking (MW) and stir frying (SF) on the free radical scavenging potential of spinach, fenugreek leaves, broccoli, cabbage and capsicum was studied. The optimum cooking time was adjudged by the sensory evaluation of the vegetables cooked for different time intervals. Hydroxyl radical scavenging potential was increased during CLC and MW in all the vegetables. The maximum gain was in spinach (55.9 and 56.9%) followed by broccoli (38.6 and 40.2%) during two cooking methods. Similarly, superoxide and nitric oxide radical scavenging potential was increased during CLC and MW in all the vegetables. The maximum gain in superoxide radical scavenging activity during CLC was found in broccoli (16.59%), followed by cabbage (12.85%), whereas, maximum gain during MW was found in cabbage (13.92%), followed by broccoli (7.95%). The lesser gain i.e. 2.92 and 1.83% was found during SF, when compared to raw vegetables. The per cent inhibition of nitric oxide radicals in raw vegetables ranged between 44.82 to 55.32%. CLC and MW resulted in better inhibition of nitric oxide radicals in all vegetables, when compared to raw vegetables. On the other hand, SF caused an increase in nitric oxide radical scavenging potential in four out of five vegetables. The study recommended that for retaining antioxidant properties of cooked vegetables, MW should be the most preferred method followed by CLC while SF should be the least preferred one.

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