Steaming vs. Roasting Your Veggies

There are many ways to prepare vegetables. One popular method is oven roasting, another is steaming.
While roasting broccoli takes up to 20 minutes, steaming is 3 times faster.

If you think about the temperatures involved, this may seem counter-intuitive. Oven temperature when roasting (450 degrees) is much higher than steam (boiled water is 220 degrees), so logically roasting should get the job done faster.

The explanation is easier to understand by reflecting on a painful experience we’ve all been through at some point in the kitchen. If you’ve ever steamed food in a covered saucepan and lifted the lid, you may have inadvertently placed your hand directly over the steam and been instantly scalded. However, when you open the oven door to overturn some roasting vegetable, you can comfortably have your hand inside for 10 seconds without being burned.

To understand why this happens, we need to go back to basic chemistry and the wonderful property of water molecules. The H2O molecule is shaped like a V:  at the bottom is the oxygen atom, and at the top are 2 hydrogen atoms. This shape creates a slight electrical polarity, which means the oxygen atom will be attracting hydrogen atoms from OTHER water molecules. Water molecules like to hang out together.

These “hydrogen bonds” means it takes a lot of energy to separate water molecules from one another. For example: when turning water to steam. Water in its liquid form will absorb a lot of heat (energy) before it finally starts to vaporize (become steam). This is called¬†latent heat of vaporization.

When we heat water to its boiling point and get the steam going, there’s a lot of energy stored in those vapor molecules. Once that vapor touches the broccoli floret, it condenses back to liquid form, releasing a lot of energy (heat) onto the vegetable, much more energy than dry, hot air upon contact with a floret.

And that’s why steaming is faster than roasting.

No matter what preparation method you choose, always make room for lots of veggies in your diet.

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