More on mustard

I wanted to pick up where I left off in my last post, because there were a couple of points that I glossed over that deserve a little more detail.

The first involves mustard seed varieties. As I mentioned, mustard seed comes in three different types: black, brown and yellow. Each one is, in fact, a different species. Yellow (Sinapis alba, also called white), brown (Brassica juncea) and black (Brassica nigra). A yellow-hulled version of B. juncea is also available, sold as “Oriental” mustard seed.

Yellow mustard is the mildest of the three, because it contains a different chemical, sinalbin, instead of the sinigrin found in brown and black mustards. That’s why it’s used mostly whole in pickling spice mixes or as the base for the bright yellow prepared mustard that’s ubiquitous in North America. (Incidentally, this kind of prepared mustard usually gets its colour from turmeric; yellow mustard seed isn’t that yellow!)

Also, mustard is known for its emulsification properties. I often add a dollop of mustard to vinaigrettes to help them hold together. (Well, that and for the flavour.) For a long time, I assumed that the molecule responsible was lecithin, the emulsifier par excellence of the culinary world. Not so. The main molecule responsible is actually mucilage, a polysaccharide that’s found in many plants, but is present in high levels in mustard hulls, especially those of white mustard. You may recognize mucilage as the slimy substance in okra and natto (Japanese fermented soy beans). It’s also the ingredient in the marshmallow plant that used to be used to make the marshmallow confection.