Certain methods of preparation and cooking can causevegetables to lose their cancer-fighting compounds, with microwaving the biggest culprit, finds a new study published in the Journal of the Science of Food and Agriculture.
A study investigating various cooking methods of broccoli concluded that microwaving is the clear loser: microwaved broccoli had lost 97 per cent, 74 per cent and 87 per cent of three major antioxidant compounds - flavonoids, sinapics and caffeoyl-quinic derivatives. By stark comparison, steamed broccoli had lost only 11 per cent, 0 per cent and 8 per cent, respectively, of the same antioxidants.
"Most of the bioactive compounds are water soluble, during heating they leach in a high percentage to the cooking water, reducing their nutritional benefits in the foodstuff.
Because of this it is recommended to cook vegetables in the minimum amount of water (as in steaming), in order toretain their nutritional benefits," said Dr Cristina Garcia-Viguera, co-author of the study.
The discovery is supported by evidence from another study published simultaneously in JSFA. Researchers in Finland, VTT Biotechnology, observed the effects of preparation and storage on various bioactive compounds in frozen vegetables.
They found that the blanching of vegetables prior to freezing caused losses of up to a third of their antioxidant content. Dr Riitta Puupponen-Pimiä, co-author of the study, pointed out that the effects of blanching were largely plant species-dependent. Slight furtherlosses occurred during frozen storage, though most bioactive compounds, including antioxidants, were quite stable during storage.
Science today has shown that antioxidant compounds, which are naturally prevalent in many vegetables, have protective effects on the body, eliminating harmful free radicals - highly volatile molecules that damage the DNA of cells that can cause serious diseases such as cancer and heart disease.
The authors note that while a healthy diet should contain more than enough antioxidants, how food isprepared and cooked may be just as important as what is eaten.
Full findings of the 'Phenolic compounds contentin edible parts of broccoli inflorescences after domestic cooking,' study by Vallejo F, Tomás-Barberán F A, García-Viguera C., are published in the Journal of the Science of Food and Agriculture . 2003 Volume 83(14) as is the Puupponen-Pimiä R, et al study, 'Effects of blanching and freezing on vegetables'.