Friday, January 30, 2009

Starch (in sauce, soups, cheezecakes, etc)

I promised to explain starch-based starches, and I will. Until I read Cookwise, starches seemed very simple to me. Buy some cornstarch, add a pinch to a thin sauce or soup, and pow! Instant thickness. Starches, obviously, are more complex than this.

What is Starch?

Starch is composed of long strands of sugar (glucose, specifically). Starch comes from plants which store sugar in the form of starch. Some plants store starch in roots or tubers; others, like banana trees, store starch in their fruit. That's why bananas make a great egg replacer! Starch appears in two forms – as amylose or amylopectin. Amylose is found in grains; amylopectin is found in cornstarch, potato starch, and tapioca. (I'm not sure which form is in starchy fruit). While amylose holds its thick form under different temperatures, amylopectin thins when cooled, reheated, stirred too vigourously, or cooked at very high heat. You're probably wondering why anyone would use weak amylopectin, then. Well, there's another important difference between the two starch forms. When they set, amylose is opaque whereas amylopectin is transparent and glossy. While this difference may seem unimportant if you're just adding starch to thicken soup, this difference is very important to bakers. Opaque apple pie filling just doesn't look right.

How Does Starch Thicken?

If you remember only one thing about starch, let it be this: starch needs heat! When starch is heated, its molecules separate from each other, soak up surrounding liquid, and begin to puff. The hotter the liquid, the puffier the starch. Once the liquid nears boiling point, the puffy starch pops, flooding your food with thickening power. (You won't see any puffing or popping). Basically, starch doesn't thicken your sauce or soup until it just starts to boil. (That means you can't dissolve starch in cold water).

This is a very important point. Many people, including myself, add starch to something, stir, and wonder why it doesn't feel thicker. So they add more starch. When the starch finally pops and thickens, they have a gluey, starchy mess. Before you add more starch, first bring your starch-based food to a boil and then determine whether it's thick enough to your likening. (With sauces, you'll know it's boiling when bubbles appear).

Some other quick tidbits about starch: (1) Starch doesn't work with acidic sauces. (2) Salt increases the temperature at which starch molecules puff and pop.

Methods for Adding Starch to Food

There are three methods: slurry, beurre manie, and roux. The point of each method is to prevent lumps from forming when you add the starch to the hot food.

A slurry is a mix of starch and cold water that is then added to the food. When I read this in Cookwise, I was instantly reminded of A Vegan Ice Cream Paradise's soy cream recipes. Her recipes call for mixing 2 tablespoons cornstarch into ¼ cup of soy milk. The rest of the soy milk is heated to a boil with the sugar. Then you turn off the heat, add in the slurry, and stir until slightly thicker. Her recipes are awesome, and now I understand why the cornstarch is set aside.

Beurre maine is butter and flour kneaded together, and then added to the food. As the butter melts, it releases the starch grain by grain. Pretty interesting, huh? Could it be done with Earth Balance? I find that learning about cooking usually brings up even more questions about cooking.

Roux is a cross between beurre maine and a reduction. It can only be used when you have leftover hot fat in a pan from something you just cooked. (For omnis, this is the nasty grease left behind from browned meat.) Roux is the result of vigorously stirring flour into the hot fat, which causes the starch to separate grain by grain. A roux should cook for several minutes. Gravies are rouxes. And, actually, the Chana Masala recipe from my last post has a roux twist to it. You stir in besan (also known as chickpea flour or gram flour) to the spiced oil before adding the puree. Who knew a sauce could be two types of sauces combined?! Cooking is deceptively complex sometimes.

How Much Starch to Use

If using flour:

Thin sauce: 1 T flour per 1 cup liquid

Medium sauce: 2 T flour per 1 cup

Thick sauce: 3 T flour per 1 cup

If using cornstarch:

Thin sauce: ½ T per 1 cup liquid

Medium: 1 T + 1 teaspoon per cup

Thick: 1 ½ T per cup


So there's this food called Cheezish. It's pretty popular at the Vegan Represent forum, and for good reason. This vegan mac and cheese looks like the Kraft stuff, and it tastes very good, too. Personally, I have been scarred by too many bad mock cheese sauces, so I made this for Jeff, who is always eager to try new vegan cheese sauces. I don't have a picture of this dish. My blender didn't puree the pimientos finely enough, so the cheezish didn't look so beautiful. It was a bright orange sauce flecked with red. However, someone else has posted mouth-watering pictures of Cheezish here.

Knowing how starch works in a recipe made a world of difference when I approached this recipe. Just looking at it, I could see where I would have failed.

The cornstarch-based sauce begins as a slurry and is heated in a pan until thick. I stirred the sauce constantly to prevent lumps. (I did not stir vigorously because of the finicky amylopectin.) I waited for bubbles to appear. This point in time is when stupid Gabe would have added starch. The sauce wasn't thickening after a few minutes over medium heat. But I waited patiently, and then, a bubble rose lazily to the surface and popped. Suddenly, there were many bubbles and the sauce began to feel thicker! I let it bubble for a minute as I stirred the thickening sauce.

A success! My first starch-based sauce that wasn't lumpy, gluey, or starchy.

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