Raw versus cooked vegetable juice

Abstract

The effect of microwave cooking on vegetables was analysed regarding parameters affecting postprandial glycaemic overload and oxidative stress. Microwave cooking affected the biological activities in different vegetables different ways. Rat intestinal α-glucosidase inhibitory activity was not affected by cooking in yellow cucumber, ridge gourd, radish root and bladder dock juice, however, it was reduced in bottle gourd. On the other hand, an increase in α-glucosidase inhibitory potential was noticed after cooking in green amaranthus. Similarly, free radical scavenging activity increased due to cooking in vegetable juice except in bladder dock and palak. Antihaemolytic activity increased in bottle gourd, radish root, palak and green amaranthus, and decreased in yellow cucumber and bladder dock juice after cooking. However, it was not affected in ridge gourd and radish leaves. Cooking augmented antiglycation properties in the juice of ridge gourd, radish root and leaves, but mitigated those properties in yellow cucumber and bladder dock. No change in antiglycation potential was noticed due to cooking in bottle gourd and green amaranthus leaf juice. Cooking increased total polyphenol content in vegetable juice, however, varied results were obtained for total flavonoid content. Substantial loss in protein content due to cooking was recorded in all vegetables. Although among the studied vegetables, the juice of ridge gourd and radish root displayed a majority of biological activities, the juice of raw yellow cucumber displayed better α-glucosidase inhibition, free radical scavenging and antihaemolytic and antiglycation activities. Therefore, raw yellow cucumber juice may become a cost-effective nutrafood helpful in mitigating disorders of glycaemic overload and oxidative stress.