- The Washington Times - Wednesday, January 7, 2009

Cooking knowledge has been handed down generation to generation, so it should not be a surprise that errors are passed on as well. One such error is that acidic ingredients preserve the shape of food.

I have had three chefs tell me that acid preserves the shape of foods. Things like: “You should add vinegar to Boston baked beans to preserve the shape of the beans during the lengthy cooking.”

This is absolutely not true. Acidic ingredients can prevent the cooking of starches — keep them rock-hard raw and inedible. In Boston baked beans, thank goodness, most cooks do not add enough vinegar to cause this. The sugar and molasses actually are what cause the beans to retain their shape during hours of cooking.

In an effort to clarify this whole issue, let’s go over foods and shape changes during cooking. Cooking methods and other ingredients can change the shape of food. Proteins become firmer with heat (for example, eggs go from liquid to solid) but fruits and vegetables soften with heat. Starches swell and soften.

Proteins: heat or acid

Raw natural proteins are separate individual units. Picture little individual wads of ribbon, each held together by bonds. You have a wad (raw protein) over to the left, one to the right — they are totally separate, with plenty of room for light to go between them. You can see right through an egg white when you crack it in a pan. As you heat raw proteins, some of their bonds break, and the “wad” partially unwinds, with some of its bonds sticking out. Almost immediately, this partially unwound protein with its bonds exposed runs into another unwound protein, and they bind together. There is no longer room for light to go between. The egg white in the frying pan becomes solid white.

Acidic ingredients can “cook” raw proteins just like heat. Ceviches are raw fish or scallops that have been “cooked” with lime juice (the most acidic of citrus juices).

Fruits and vegetables: sugar or calcium

When you heat a fruit or vegetable, the cell walls shrink, and the cells start to leak. The complex pectic substances and hemicellulose glue between the cells change to water-soluble pectins and dissolve. The cells are leaking and falling apart. It’s no wonder fruits and vegetables soften when we cook them.

In many desserts, you may want the fruit to soften but not fall apart. In an apple pie, you want nice apple wedges, not applesauce. In some legume dishes such as Boston baked beans, you want the beans to hold their shape — not turn to bean mush like refried beans.

Sugar and/or calcium prevent the reactions that cause the glue between the cells to dissolve. So, with sugar or calcium, fruit or vegetable cells stay together, and the fruit or vegetable holds its shape. The same beans that become bean mush (refried beans) when cooked for several hours can hold their shape through days of cooking if sugar and molasses (which contains both sugar and calcium) are added — they become Boston baked beans.

Sugar gives cooks great control over the texture of a fruit or vegetable. In the recipe for apple wedges below, I wanted to serve the wedges as a firm, sweet complement to a meat main course, so I tossed them with sugar to preserve their shape before I even started cooking. Cooks can saute apple wedges without sugar to soften slightly — until they are the texture the cook wants — then add sugar to preserve the shape.

You can see that the timing of when you add the sugar can give you great control over the texture of fruits and vegetables. I have known many fine cooks who add a little sugar to a vegetable just after cooking. Even a tiny amount of sugar provides complex flavors as well as enhancing shape.

For the applesauce (recipe below), I wanted the apples to become very soft with cooking so that I could mash them. So, I did not add sugar until after I had cooked and mashed the apples.

Starch: acidic Ingredients

Starches are granules of carbohydrates that are packed with layer after layer of starch. They are insoluble in cold liquid, but as the liquid warms, it seeps into the granule and causes the granule to swell. Rice, potatoes and pasta (starchy foods) soften (cook) as the granules swell. As the liquid is heated and more and more seeps into the granule, it swells to many times its original size and finally pops. In making a sauce or gravy, this is when starch rushes out into the sauce and it thickens.

Acidic ingredients prevent starch from swelling. Thus, acidic ingredients can prevent the cooking of a starch. They preserve the shape of the raw food but keep it completely raw — uncooked. In paella, if very acidic tomatoes are added initially, the rice may remain rock-hard after hours of cooking. Lemon meringue pie recipes that have a lot of lemon juice may direct you to wait until after you have heated the starch and liquid and allowed it to thicken before you stir in the lemon juice.

Homemade applesauce

Awhile back, I had not had homemade applesauce since childhood. I was startled that a dish I had dismissed as ordinary could be so extraordinarily good. Fresh applesauce is not related to that in cans or jars. Fruit or vegetable cells lose water and soften with heat. Pectic substances that hold cells together convert to soluble pectins and dissolve; cells fall apart, and the fruit or vegetable becomes mushy. Makes 4 servings.

5 medium apples, peeled, cored and cut into wedges (I like Fuji or ripe Golden Delicious)

1/2 cup (packed) light brown sugar

1 teaspoon ground cinnamon

1/2 teaspoon salt

Microwave the apples in a glass container covered with plastic wrap for 10 minutes on High or until very soft (see note). Mash the apples into applesauce with a potato masher. Stir in brown sugar, cinnamon and salt. Serve hot or cold.

Note: The apples can be cooked on the top of the stove in a heavy covered saucepan. Add 3 tablespoons of water and cook on medium-low heat until apples are very soft, about 20 minutes.

Apple wedges

Simple apple wedges are a refreshing addition to a meat sauce or are excellent stirred into cooked vegetables such as carrot slices. The cooking time here is lengthy to prove a point, but for most dishes, I cook them just 4 to 5 minutes so they retain a little crispness. Adding the sugar before cooking preserves the insoluble pectic-substance “glue” that holds the cells together and keeps the apple wedges firm. Brown sugar contains calcium, which also helps in preserving firmness. Makes 4 to 6 servings.

5 medium apples, peeled, cored and cut into wedges (I like Fuji or ripe Golden Delicious)

1/2 cup (packed) light brown sugar

1 teaspoon ground cinnamon

1/2 teaspoon salt

2 tablespoons butter

Stir together the apples, brown sugar and cinnamon in a glass mixing bowl. Cover with plastic wrap and microwave on High for 10 minutes (see note). Sprinkle with salt, add butter, and stir gently. Serve hot or cold.

Note: The apples, sugar and cinnamon can be cooked on top of the stove in a heavy covered saucepan. Add 3 tablespoons of water and cook on medium-low heat until wedges have softened slightly, about 15 minutes.

• Food scientist Shirley O. Corriher is author of “CookWise” and “BakeWise.”

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