FOOD SCIENCE EXPERIMENT: SOUR SECRET
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The following experiment is designed to supplement activities in already
existing food and nutrition projects. First read the section "Caution-Be
Science Wise" and then help 4-H members work through the experiment.
CAUTION - BE SCIENCE WISE!
Before you begin any science experiment, you should always follow these basic
rules:
1. Be sure to read ALL directions before starting the experiments.
2. In many experiments, a "control" is used. The control is the standard
against which you compare the experimental food.
3. When doing the experiments, keep everything the same as the control except
for the one thing the directions say to change. Use the same size pans,
the same type of bowls and the same mixing speeds. Be sure that just ONE
thing changes each time.
4. Be sure to label each food when conducting these experiments. Use a piece
of masking tape, a marking pencil, a crayon or anything that will help you
remember which food is which. In some experiments, you'll have no trouble
telling the foods apart. In others, the foods may look the same.
5. The experimental food is not meant to be perfect. Since you are purposely
doing something wrong, you can't expect it to be perfect! So it's all
right when something turns out "bad." That's what is SUPPOSED to happen.
6. Not all experiments in food science yield products that can be eaten.
NEVER SAMPLE PRODUCTS IN AN EXPERIMENT UNLESS YOUR LEADER SAYS THEY ARE
SAFE TO EAT.
7. Records are an important part of any scientific project. You should write
down what happens in each experiment. Experiments may not turn out exactly
the same every time. Recording your results will help you and others who
may try to repeat your experiment.
THE SOUR SECRET
INTRODUCTION
Besides cooking, an acid such as vinegar or lemon juice can be added to a
protein food to cause protein coagulation. You can tell that coagulation has
occurred if solid particles form in a liquid that contains protein, such as
milk. Give it a try.
INGREDIENTS
1/2 cup milk
1-1/2 teaspoons vinegar or lemon juice
EQUIPMENT
Measuring cup - liquid
Measuring spoons
PROCEDURE
1. Put the milk in the measuring cup.
2. Add the vinegar or lemon juice to the milk and stir.
3. Let the mixture stand for 10 minutes. Record what you see.
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4. Now stir the milk again. Do the solid materials dissolve? ________________
This coagulated milk is also called "sour milk." This does not mean it is
spoiled! It means that its flavor has changed. You can now use this milk
in a recipe that has sour milk as one of the ingredients.
5. See if you can answer these questions based on what you observed:
* Can you tell if the protein has been changed? If so, how?
* You are making a banana bread that calls for 1 cup sour milk as one of
the ingredients. What can you do to make milk sour?
EXPLANATION
Acids such as vinegar or lemon juice cause the protein in milk to coagulate
and separate out from the milk. These solid materials will not dissolve when
stirred. This "secret" can be used to make sour milk from fresh milk for use
in recipes in which sour milk is one of the ingredients.
SOURCE: Food Mysteries, Michigan State University
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Updated 8/15/05