How to Cook Greens

How to Cook Greens

September 11, 2019 100 By Ewald Bahringer


“How to Cook Greens” “The main purpose of cooking
vegetables is to make them more edible, palatable,
and digestible.” The downside, though, is that
“cooking may adversely affect the levels of nutrients, especially the
heat-sensitive and water-soluble ones.” But even if you boil greens for 10 minutes,
the drop in antioxidant capacity, for example, which is a rough proxy for
phytonutrient retention, isn’t that much. Yes, there’s a significant drop
in each case—a 15 to 20 percent drop— but most of the antioxidant
power is retained, even if you boiled lettuce for 10 minutes. The single nutrient that drops
the most is probably vitamin C, but as you can see collards
start out so vitamin C-packed, that even collard greens boiled
for 10 minutes have twice as much vitamin C compared to even raw broccoli. You can see the vitamin C in
spinach really takes a hit. Even just blanching for five minutes
can cut vitamin C levels more than half, with more than 90 percent dissolving
away into the water after 15 minutes; though most of the beta
carotene, which is fat soluble, tends to stay in the leaves. But just keeping it in a regular plastic bag like you get in the produce
aisle can protect it. The refrigeration is important, though. Even in a bag, a hot day
can wipe out nearly 50 percent. Not as bad as drying, though,
which can wipe out up to 90 percent of the vitamin C, suggesting
that something like kale chips may pale in comparison to fresh,
though vitamin C is particularly sensitive. Other nutrients like beta carotene
are less affected across the board. Cooking by microwaving and
steaming preserves the nutrition more than boiling, here
measured in watercress. A little steaming or microwaving
hardly has any effect compared to raw, though boiling even two minutes may
cut antioxidant levels nearly in half. Watercress is a cruciferous
vegetable, though— a cabbage and broccoli-family vegetable, so it’s prized for its glucosinolate content, which turns into that magical
cabbage compound sulforaphane. What does cooking do to it? Fresh is best, but steaming’s not bad,
with microwaving coming in second, and then stir-frying and boiling
at the bottom of the barrel. The glucosinolates in other
cruciferous vegetables are also significantly affected by boiling. The researchers conclude that
red cabbage is best consumed fresh, and look, not just in salads. As I talked about in How Not to Die, I always keep a red or purple cabbage
in my crisper to cruciferize my meals, slicing off shreds and putting
it on basically anything. But if you are going to cook it,
steaming may be the best bet, “so as to retain the optimum benefits
of the health-promoting compounds.” Other nutrients we look to greens for
are the eyesight preserving nutrients like lutein, which I’ve talk
about before, and folate, particularly important for
women of child-bearing age; and vegetables are the
main natural source. It’s been estimated that approximately
half the folate is lost during cooking which may
be true for boiling broccoli or stir-frying spinach or mustard greens. But the folate in stir-fried
kale holds up better, only losing about a quarter,
similar to steamed broccoli florets. But note that broccoli starts
out so high that even boiled broccoli has more folate than raw spinach. But check out broccoli leaves. Not only do they start out
with among the highest levels, the levels actually go up
a bit when you cook them. No one’s ever looked at the folate
concentration in broccoli leaves, which ironically are commonly
just cut off and thrown away yet contributes great
concentrations of this vitamin. Therefore, we should make
sure to eat them. Note they also compared thinly sliced
kale to kale just torn into larger pieces, to determine if a larger
surface of exposure would promote greater losses of folate in kale. However, no effects were
found, so slice away. Here they just looked at stir-frying. What about the effect of
other cooking methods on kale? There’s lots of studies on
cooking cabbage and broccoli, however, very little information
has been available on the queen of greens… until now. First of all, fresh versus frozen. “The freezing process is
generally regarded as destructive to
antioxidant compounds.” One just assumes that frozen would
have a lower antioxidant capacity compared to fresh, but kale,
breaks all the rules. The frozen kale showed a higher
antioxidant capacity than fresh. And not just by a little, we’re
talking 60 percent more. Wow! OK, so what happens when you cook it? If you start out normalizing the
starting levels at 100 percent, blanching and steaming actually
boost the antioxidant content, whereas microwaving or even
boiling doesn’t seem to do much— so you can boil kale without
losing out on its antioxidant punch. I told you kale was a rule breaker. But check out that
blanching and steaming. Heat can disrupt the plant cell walls and all the little
subcellular compartments and spill out extra antioxidant
compounds that may have been hiding. Now that’s usually counterbalanced by
losses caused by high temperatures, but the kale compounds
are looking pretty cruciferocious and stood their ground.