- The Washington Times - Tuesday, September 14, 2004

Remember when you were a child and bit into a chocolate-covered cherry? The sugar

syrup ran down your chin, and it tasted wonderful.

When this candy was made, each cherry was rolled in a thick paste of very fine sugar crystals to form a ball, which was then dipped in chocolate. What caused that thick sugar paste to turn into syrup while it was completely sealed in chocolate?

Here’s another mystery. Cassava, the source of tapioca, contains cyanide, yet it is a major food in many parts of the world. How can this be? Then there is the white chocolate banana cream pie mystery. When it is made, it is so thick you can stand a spoon up in it. The next day, it is soup. What happens?

These strange occurrences and thousands more are the work of mischievous proteins called enzymes, whose job it is to start or speed up chemical reactions. We can make these little fellows work for us if we understand their structure and function.

Enzymes have a jigsaw-puzzle configuration that fits exactly the substance they are going to break down. They latch onto the substance and pull or strain the bonds in the area where the substance is going to break. Once the substance is almost apart, the enzyme spits it out. The substance then breaks apart on its own, and the enzyme moves on to another molecule.

All of this happens quickly. A single enzyme can break apart 1,000 molecules per second.

Back there in our white chocolate banana cream pie, if the filling did not get heated enough (up to 170 degrees) to kill the egg-yolk enzyme alpha amylase, a few surviving enzymes could gobble up the firm starch gel and easily turn it to soup.

With cassava, the enzyme that breaks up the cyanide and the cyanide itself are in the same cell but sealed off in separate parts. If the cassava is cut, this allows the enzyme to get to the cyanide and convert it to harmless compounds.

The traditional method of preparation is to chop or mash the cassava and allow it to stand for a while. This gives enzymes in the cassava plenty of time to render the cyanide harmless before it is eaten.

Most of us have cried while chopping onions. The onion enzyme and the substance that breaks up into the irritating gases are in the same cell. When we cut the onion, we allow the enzyme to get to this substance, and fumes are produced. This chemical warfare is an onion’s way of protecting itself when it is attacked. This is similar to what happens with cassava.

In making the chocolate-covered cherries, candy manufacturers add an enzyme from yeast to the thick paste, which is made of sucrose, a double sugar composed of glucose and fructose joined together.

When the enzyme breaks up sucrose into glucose and fructose, both of these sugars are more soluble than sucrose, and enough water is present for the sugars to dissolve into the thick syrup that can dribble off of your chin.

We witness enzymes in action every time we cut a piece of fruit and see the cut surface turn brown. This browning is desirable and an important step in flavor, aroma and color development of cacao, chocolate, tea and cider, although not in sliced fruits and vegetables.

Vitamin C prevents this browning, so to protect your fruit, you can simply crush a vitamin C tablet and dissolve it in a bowl of water. As you slice the fruit, toss it immediately into the vitamin C water. Or, because orange juice is high in vitamin C, place the sliced fruit in cold orange juice until ready to use. This is ideal for delicately flavored fruits such as bananas.

Enzymes are everywhere. Even experienced cookbook author Jean Jones once called to ask, “Shirley, what is in carrots that’s causing them to wreck my gelatin mold?” Her orange gelatin carrot mold had failed three times. When she went over how she made it, she mentioned that she had added a teaspoon of minced ginger root.

I began to search scientific literature and found that, sure enough, ginger root contains a single enzyme that breaks down both collagen and protein fibers. No wonder minced ginger is used in so many marinades for stir-fries. It’s a perfect tenderizer, which of course means that it is not a plus for gelatin salad.

Many cooks know raw pineapple has an enzyme that can break down proteins, but there are many little-known enzymes in fruit that can attack gelatin and meat fibers.

Papain, an enzyme in papayas, is used as a meat tenderizer. Fresh figs, kiwis and honeydew melons also contain enzymes that can wreck gelatin.

Oddly enough, enzymes that break down tough fibers in meat to tenderize it are not very effective on thick pieces of meat because they can only work on the surface. If you have ever had a piece of tough meat with a mushy surface, you can be pretty safe in guessing it has been treated on the surface with tenderizer.

Cooks have sometimes tried disastrously to punch lots of holes in a piece of meat and then soaked the meat in pineapple juice so that enzymes could seep into the interior. If they leave the meat in the least bit too long, the result will be mush all the way through.

However, you can get wonderfully tender pieces of thinly sliced meat using minced ginger root. The stir-fry recipe that follows is a delicious example of enzymes doing their best work.

Strikingly beautiful, incredibly tender, low-fat chicken

Marinating chicken in buttermilk, which contains calcium to initiate the tenderizing that occurs in natural aging, and ginger root, which contains an enzyme that breaks up protein fibers, produces marvelously tender chicken. Intensely flavored ingredients such as chili and ginger root enhance the flavors of this low-fat dish. A small amount of gin dissolves and releases alcohol-soluble flavor components that were locked in the ingredients. The salt in the marinade acts as a brine to make the chicken juicy.

MARINADE:

6 large, boneless chicken breast halves, trimmed and cut at an angle across the grain into 5 to 6 slices

1 teaspoon salt

3 tablespoons minced fresh ginger root

1/4 teaspoon cayenne

½ cup (approximately) buttermilk

STIR-FRY:

1 small head Romaine lettuce, shredded

3 tablespoons olive oil

3 medium shallots, chopped

2 tablespoons minced ginger root

1 small serrano chili, seeds included, sliced thinly crosswise

1/3 cup gin

1½ cups seedless red or black grapes, stems removed

2 teaspoons fresh thyme leaves

½ cup chicken broth

1 teaspoon instant chicken bouillon

1 tablespoon sugar

1 tablespoon cornstarch

5 scallions, green included, sliced into rings

½ bunch cilantro, coarsely chopped, optional

Place chicken in a small bowl and rub 1 teaspoon salt and 3 tablespoons ginger root into the slices. Sprinkle with cayenne and add just enough buttermilk to cover. Cover with plastic wrap and marinate for about 3 hours in the refrigerator.

Spread shredded lettuce on a serving platter and set aside. Rinse chicken, drain and pat dry.

Heat olive oil in a large skillet or wok over high heat and cook shallots, 2 tablespoons ginger root and chili, stirring constantly.

Add marinated chicken and cook briefly, stirring constantly, 1 to 2 minutes. Add gin and quickly cover to steam for 1 minute. Immediately remove chicken with a slotted spoon and spread over lettuce.

Add grapes to skillet and stir-fry just to warm, less than a minute. Remove grapes with a slotted spoon and spread them out with the chicken. Add the thyme to the skillet and stir, then add chicken broth and return to the heat. Stir well to loosen any bits on the pan.

Stir in the bouillon and sugar. Add the cornstarch and stir until no lumps remain. Cook, stirring constantly, until it thickens. Pour immediately over the chicken. Garnish with scallion and cilantro and serve immediately. Makes 4 to 6 servings.

Food scientist Shirley O. Corriher is the author of “CookWise: The Hows and Whys of Successful Cooking” (William Morrow).


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