The Food Lab: Better Home Cooking Through Science

major stems from a bunch of kale, then shredding the leaves
into bite-sized strips.
Some folks make the false assumption that it’s the acid in
the dressing or marinade that causes the tough leaves to
tenderize. Actually, it’s the oil that does the job. (See
“Vinaigrettes,” here, for more on this.) Plant leaves naturally
have a waxy cuticle on them in order to protect them from
rain. Haven’t you seen rainwater falling on a leaf? It rolls
straight off, like water off a duck’s back. But this cuticle is
oil soluble, so when you massage oil into a pile of kale
leaves, it removes the coating, allowing the cells underneath
to acquire some controlled damage, thereby softening them.
The question then is this: is it necessary to pretenderize the
greens with straight oil before dressing them, or can the
dressing alone do the job?
I tried it both ways, making a couple big batches at the
office for folks to try (any day when there are extra greens
in the office is a happy one). The first I tossed with olive oil,
salt, and pepper, massaging the oil into the leaves and
letting the kale rest for half an hour before tossing it with the
dressing. The second one I tossed with the dressing alone
(adding extra olive oil, salt, and pepper to compensate) and
served it up immediately.