People used to fry up vegetables and the world was a tasty, happy place. Then some dietitian schmucks told us that frying was no good and that we should instead (shudder) boil vegetables. But that turned out to deplete them of too many nutrients, in addition to making them taste like an old man's boiled underwear.
Then it was all about the microwave or, maybe, for the courageous, a brief stir fry, just enough to tender the vegetables up but not destroy any nutrients or turn them into something that causes cancer or heart disease.
But now, out of lovely Spain, comes news that deep frying (yes, deep) and sauteing of vegetables makes them more nutritious.
What They Did
The researchers had it in their minds that certain cooking methods destroyed antioxidants and polyphenols in the vegetables that form a large part of the Mediterranean diet.
In particular, it was thought that cooking destroyed vitamins C and E, along with phytochemicals like beta-carotene. To test the notion, they took potatoes, tomatoes, eggplant, and pumpkin and prepared them in four different ways:
- Deep frying in extra virgin olive oil (EVOO)
- Sauteing them in EVOO
- Boiled in EVOO and water
- Boiled in water
The scientists then matched the pre- and post-cooking levels of fat, moisture, total phenols, and 18 specific phenolic compounds, as well as antioxidant capability.
What They Found
Deep frying and sauteing, of course, increased the fat content of the vegetables (because they absorbed some of the EVOO), whereas both types of boiling reduced it. No surprises there.
However, deep frying and sauteing the vegetables in EVOO increased the number and/or level of phenolics in them. The vegetables naturally picked up phenols like oleuropein, pinoresinol, hydroxytyrosol, and tyrosol from the olive oil, but deep frying and sauteing also increased the level of particular vegetable phenolics such as chorlogenic acid and rutin.
Boiling, however, reduced the number and level of phenolics. None of the cooking methods reduced the antioxidant activity of the vegetables, though.
What This Means To You
Although the study used potatoes, tomatoes, eggplants, and pumpkin, there's no reason to think you can't deep-fry or saute other vegetables to increase their phenolic content, too.
And this is a huge deal, because polyphenols are what makes vegetables so good for us, even beyond what their vitamins and minerals might do.
Just remember that EVOO has a lower "smoke point" than regular olive oil or other "sturdier" cooking oils, for that matter. The smoke point is literally when the oil starts to smoke and it indicates that the oil is breaking down and thus losing its health benefits.
The average stove burner puts out between 250 and 350 degrees when it's on medium/low, so just keep it dialed in at the lower end of that range. Most vegetables should fry up real nice within 3 minutes or so.
- Jessica del Pilar Ramirez-Anayaa; Cristina Samaniego-Sanchez; et al. "Phenols and the antioxidant capacity of Mediterranean vegetables prepared with extra virgin olive oil using different domestic cooking techniques." Food Chemistry, Volume 188, 1 December 2015, Pages 430-438.