6 Cooking Techniques That Alter Antioxidants in Vegetables

Are you unintentionally ruining your vegetables? Depending on how you prepare your vegetables, you may be significantly impacting its antioxidant capacity. A team at the University Complutense of Madrid, Spainset out to understand how home cooking techniques impacted vegetables.
Since “diets high in vegetables and fruits have been associated with a reduced risk of cancer,” and have motivated programs that seek to increase the consumption of vegetables, the researchers believed that understanding what cooking methods best retained the nutritional profile — particularly antioxidants — “to improve their functional activity.”
The vegetables under evaluation included: artichoke, asparagus, beetroot, broad bean, broccoli, brussels sprout, cauliflower, carrot, celery, eggplant, garlic, green bean, leek, maize, onion, pea, pepper, spinach, Swiss chard, and zucchini. The researchers cooked the vegetables in a lab after cleaning them how the typical consumer would. Seven samples were created, one being kept uncooked, and the remaining six prepared by: boiling, microwaving, pressure-cooking, frying, griddling, and baking. Keep reading to find out how the vegetables fared after being cooked. 

1. Boiling

In the first antioxidant loss measurement (losses of LOO radical scavenging in the lipid system) the vegetables that were boiled saw the greatest decrease when compared to raw. Peas, cauliflower, and zucchini were the biggest losers, with losses above 50 percent. In the range of 30 to 50 percent loss were spinach, garlic, broccoli, Brussels sprouts, leek, and green beans. Artichoke, eggplant, and onion maintained fairly consistent antioxidant levels when boiled. Only one — asparagus — increased its capacity when boiled.
The second measurement took hydroxyl radical scavenging ability (OH losses) into account as a measurement of antioxidant impact. In this measure, peppers lost the highest amount, followed by spinach, cauliflower, and Swiss chard. Only beetroot, garlic, and green beans retained their raw levels. 

2. Pressure-Cooking

If you love using your pressure-cooker, you should stick with Swiss chard, beetroot, onion, artichoke, and asparagus to enjoy vegetables that keep their antioxidant profile intact. Spinach and broad beans lost between 5 and 25 percent, while eggplant significantly increased its capacity. The remaining vegetables on the list lost between 30 and 50 percent of their antioxidants after being subjected to the pressure-cooker. Again, in the second measurement, peppers lost out, and unlike in the LOO measurement, Swiss chard lost 30 to 50 percent. Celery on the other hand, increased its OH scavenging ability. 

3. Baking

To bake up vegetables in the oven, your best bets are green beans, eggplant, maize, Swiss chard, and spinach — all of which increased antioxidant activity significantly after being baked. Artichokes, asparagus, broccoli, and peppers more or less stayed the same as their raw counterparts after baking, making them good baking options as well.
Brussels sprouts, leeks, cauliflower, peas, zucchini, and carrots all lost capacity, ranging form 30 to 50 percent. Lesser losses of 5 to 30 percent occurred in onions, broad beans, celery, beetroot, and garlic. For the third time, pepper had high losses in OH scavenging ability, while microwaving increased celery significantly. 

4. Microwaving

A fair number of vegetables kept their antioxidant capacities after being microwaved, arguably the easiest preparation method. Those vegetables included artichokes, asparagus, garlic, onions, and spinach. The scavenging capacity was improved in eggplant, maize, peppers, and Swiss Chard.
Cauliflower was the only vegetable to lose over 50 percent of its antioxidant capacity, while broad bean and beet root were the only ones with minimal declines of 5 to 30 percent. The rest didn’t lose a majority, but did still see over a third of capacity disappear after this cooking method was employed. 

5. Griddling

Brussels sprouts and peas did not fare well with the griddle, but with decreases of 30 to 50 percent, they were the only vegetables to lose more than one third of capacity. Artichokes, beetroot, celery, eggplant, garlic, and maize were able to retain their raw levels, while green beans, broccoli, Swiss chard, spinach, asparagus, and onion increased significantly once prepared on the griddle.
Falling in between 5 and 30 percent were the remaining vegetables. Proving that OH scavenging abilities in peppers do not do well when cooked, griddling too caused that vegetable to have the highest decreases while celery continued to outperform the rest. 

6. Frying

Fried vegetables that you can love, while their antioxidants as measured by LOO radical scavenging love you back are Swiss chard, artichoke, and green beans. Eggplant was the only clear winner with increases in activity after frying.
On the other end of the spectrum was zucchini, which lost above 50 percent. Leeks, onions, peas, Brussels sprouts, and peppers did not exactly fare well either, with losses of 30 to 50 percent. The remaining had less substantial declines in antioxidant activity. This was the only time when peppers did not lose in the second measurement. Instead, Swiss chard saw a decline in OH scavenging, but celery was still on a winning streak.