The Key to a Successful Sauce is the Emulsifier
by Lynn Parrucci and Amy Eubanks
Give a child a jar half filled with vegetable oil
and half filled with colored water and tell him to mix the two liquids.
Watch his fascination as he tries to stir them, then maybe seal the jar
and shake it, then shake it harder and harder. Just when he thinks he’s
got it-when the oil is broken down into perfect tiny beads suspended in
the water-the liquids slowly begin to separate again, with the oil on top
and the water on the bottom. Try as you might, oil and water don’t mix.
This ancient yet simple scientific observation confounded and
challenged culinary experts for ages. Medieval chefs searched for ways
to bind oil and water together for sauces. As an agent for binding their
sauces, they pounded together bread and almonds, and moistened the mixture
with vinegar, wine or milk. They even tried liver. Neither substance worked
well, but eventually they came upon something that did: eggs. With the
addition of eggs, they found that their sauces stayed together longer.
That’s because egg yolks are emulsifers, agents that promote the combination
of two liquids that otherwise are incapable of mixing-like oil and water.
Ground mustard, milk, sugars and even soaps are emulsifiers. When an emulsifier
is combined with the two incompatable liquids, the mixture is known as
an emulsion. Let’s take a look at the chemistry behind the way emulsifiers
work.
Molecules that dissolve in water are hydrophilic, which means
“water loving,” or lipophobic, which means “oil fearing.” Alternately,
molecules that dissolve in oil are lipophilic (oil loving) or hydrophobic
(water fearing). The shape of an emulsifier’s molecules reveals how it
attracts both: They have a hydrophilic head and a hydrophobic tail. Emulsifiers
are thus able to attract both oil and water, and bring them together. Small
droplets of one substance are suspended inside the other substance. The
emulsifier also helps prevent the individual substances from separating,
which happens because the like charges on the neighboring emulsifier molecules
repel one another.
Emulsions can be disrupted by shaking or by exposure to heat or
cold. The thicker an emulsion, the less likely it is to separate because
the droplets move more slowly through the thick mixture and are less likely
to pool. Egg yolks are very effective as emulsifiers and are used to create
mayonnaise, a stable oil-in-water emulsion in a mixture that contains up
to 75 percent oil.
The following salad dressing uses butter as an emulsifier. Almost
one-fifth of butter is water suspended in milk fat and milk solids. It
contains a water base, and droplets of oil to be dispersed. As the whisked
butter slowly melts, it thickens the sauce.
The recipe is adapted from the Caribbean Christmas collection
in Bon Appetite’s December 1995 issue. The combination of balsamic vinegar,
orange juice and butter gives the dressing an intense sweetness and should
be used sparingly, drizzled over the salad just before serving rather than
soaking the leaves. The recipe can be festive throughout the winter, when
oranges are more abundant, or adapted to summer by adding fresh berries.
Scallop and Orange Spinach Salad
1.5 lb. sea scallops (optional)
paprika to taste
1 lb. fresh spinach leaves
2-3 oranges
2 carrots, sliced and steamed to soften
6-10 dried apricots, chopped (optional)
1/4 cup chopped walnuts or almonds
4 Tablespoons chopped shallots
1/2 cup olive oil
1/2 cup balsamic vinegar
1 cup orange juice
1/2 stick of butter, sliced
1. Wash and pat dry spinach. Grate 1 teaspoon orange peel and
set aside. Peel and slice oranges. Toss in large salad bowl spinach, oranges,
apricots, and carrots. Refrigerate.
2. Spread scallops on broiling pan and sprinkle with paprika to
taste.
3. In small heavy sauce pan, combine oil and vinegar. Cook over
medium high heat approximately 5 minutes until reduced by half. Add orange
juice, shallots and orange peel. Remove from heat.
4. Broil scallops until thoroughly cooked, 6-10 minutes.
5. Bring sauce back to boil and continue cooking until reduced
by 1/4.
6. Remove scallops from broiler and place on salad.
7. Remove sauce from heat. Add butter and whisk until butter is
melted and sauce is thickened. Add additional butter, if necessary, until
desired consistency.
8. Drizzle sauce over salad and serve.
Lynn Parrucci is program coordinator of the Science Center’s
Kitchen Theater, and Amy Eubanks is the research assistant.
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