According to a Spanish study, griddling-cooking on a flat metal surface with no oil, or microwave cooking can help maintain the highest antioxidant levels in vegetables.
Fruits and vegetables are considered to be rich in nutritional antioxidants, which provide cancer and disease-preventing effects. This is the reason why people are encouraged to eat several servings of fruits and vegetables.
Researchers at the University of Murcia and the University of Complutense in Spain analyzed six cooking methods with 20 vegetables in order to determine how various food preparing methods affect antioxidant activity.
The six cooking methods studied were boiling, pressure-cooking, baking, microwaving, gridlling and frying.
The researchers said that the highest antioxidant loss was observed in cauliflower after boiling and microwaving, peas after boiling, and zucchini after boiling and frying.
They also observed that green beans, beets, and garlic were found to keep their antioxidant levels after most cooking treatments.
According to them, the vegetables that increased their antioxidant levels after all cooking methods were green beans (except green beans after boiling), celery and carrots.
Artichoke was the only vegetable that kept its high antioxidant level during all the cooking methods, said the researchers.
Griddle, and microwave-cooking helped maintain the highest levels of antioxidants, produced the lowest losses while "pressure-cooking and boiling (led) to the greatest losses," says lead researcher A. M. Jimenez-Monreal.
"In short, water is not the cook's best friend when it comes to preparing vegetables," the researcher added.
A research article on the study has been published in the Journal of Food Science, published by the Institute of Food Technologists.