Abstract

Objective

The objective of this cooking and food science fair project is to determine how various ingredients affect the adsorption of a marinade onto food.

Introduction

Every culture has its own unique way of preparing food. But whether it's Chinese or American, Italian or Indian, some of the main dishes call for a marinade. The word marinade comes from the Latin word marinara, which means "of the sea." The original marinades from several centuries ago were briny (very salty) liquids, like seawater. Whatever they are made of, marinades are meant to preserve, tenderize, and flavor foods.

In this science fair project, you will test how various ingredients affect the adsorption (yes, with a "d") of a marinade ingredient onto the surface of a food. The word adsorb is used to describe the process by which a substance adheres to the surface of an object, as opposed to being absorbed into it.

In place of a seasoned marinade, you will use a food dye to determine the level of adsorption because it is easy to measure visually. The food you will use for the experiments is tofu, which has the benefits of being inexpensive and easy to cut into cubes. Using tofu and food dyes might seem like an odd way to study marinades, but using a real marinade and steaks would be quite costly and difficult to visually examine. This is a good example of simplifying a complex problem to make it easier to control the variables so you get a clear result.

The methods might be unusual, but the results of your experiments can be applied in the kitchen the next time you help your family prepare your favorite marinade!

Terms, Concepts, and Questions to Start Background Research

• Marinade
• Adsorption
• Absorption
• Acidity
• Standards
• Concentration

Questions

• What is the difference between absorption and adsorption?
• Look up the recipes for several marinades (try the second link in the Bibliography, below). Which ingredients increase the acidity of the marinades? How much salt is used?
• Based on your research, what ingredients in marinades break down the proteins in meat?

Bibliography

• Filippone, P. (2008). Marinade Science—How marinades work. Retrieved September 30, 2008, from http://homecooking.about.com/od/specificdishe1/a/marinadescience.htm.
• Allrecipes.com. (2008). Marinades Recipes. Retrieved September 30, 2008, from http://allrecipes.com/Recipes/BBQ--Grilling/Sauces-Marinades-and-Rubs/Marinades/Main.aspx

Materials and Equipment

• Knife
• Tofu, extra-firm (2 packages, about 28 oz. total); you can substitute a meat if you choose. The dye will work well with chicken breast, but other meats have not been tested by Science Buddies. Caution: Always wash your hands and clean work surfaces after working with raw meat to avoid the spread of harmful bacteria.
• Plastic wrap, clear
• Plastic cups, 16-oz. capacity (30)
• Permanent marker
• Tap water
• Measuring cup, 1-cup
• Food dye, blue
• Salt
• Vinegar
• Sugar
• Tablespoon measuring spoon
• Sheet of white paper
• Slotted spoon (or fork)
• Timer
• Lab notebook

Experimental Procedure

Preparing Your Materials

To start this science fair project, you should assemble all of the materials on a clean workspace.

1. Have your adult helper cut the tofu block into cubes, about ½ inch on each side. Cut about 60 tofu cubes. Keep the unused tofu in case you need more cubes.
2. Store 40 of the tofu cubes under plastic wrap in the refrigerator so they don't dry out.
3. The first 20 tofu cubes should be brought to room temperature for the first trial.

Creating Your Standards

In this section, you will make a set of standards. These will be used to compare the tofu cubes from your test solutions to so you can see which test solution helps the food product adsorb more marinade. The standards will progress from "1" for no color, up to "6" for the maximum amount of color.

1. Using the permanent marker, label six of the plastic cups with the numbers 1-6. Line them up on your workspace in increasing order.
2. Put ½ cup of water into each of the six cups.
3. Add dye to the cups, starting with the cup labeled "1," as follows: 0 drops, 1 drop, 2 drops, 4 drops, 8 drops, and 16 drops.
4. Gently drop two room-temperature tofu cubes into each cup.
   1. The reason for using two cubes in each cup is to provide two standards, which helps minimize any effects due to natural variations in size, texture, etc. of the tofu cubes.
   2. You will take the cubes out of each standard solution when you are ready to examine your experimental samples.
5. Record the time that you added the cubes to the dye solution in your lab notebook.

Preparing the Test Solutions

Now it's time to make the test solutions. Make the test solutions in the measuring cup, and then transfer them to a clean glass or plastic container. Make sure you rinse out the measuring cup and measuring spoon between making each solution.

1. Label four plastic cups, as follows: water, salt, vinegar and sugar.
2. Pour 1 cup of water into the "water" cup.
3. Prepare and pour the salt solution into the "salt" cup: 1 tablespoon of salt in 1 cup of water.
   1. Since 1 tablespoon (tbsp.) of salt is about 18 grams (g), and 1 cup of water is about 230 g, this is roughly an 8 percent solution of salt.
4. Prepare and pour the vinegar solution into the "vinegar" cup: ¼ cup of vinegar and ¾ cups of water.
   1. Look at the label on the vinegar bottle for the percent acidity. The percent acidity measures the percent of acetic acid in the vinegar. Divide this number by 4 to obtain the percent acidity for your test solution. Record this information in your lab notebook.
5. Prepare and pour the sugar solution into the "sugar" cup: 1 tbsp. of sugar in 1 cup of water.
   1. Since 1 tbsp. of sugar weighs about 14 g, and 1 cup of water weighs about 230 g, this is roughly a 6 percent solution of sugar.
6. Add eight drops of dye to each of the solutions: water, salt, vinegar, and sugar.
7. Carefully add two room-temperature tofu cubes to each of the dye test solutions.
8. Record the times that the cubes go into and come out of the dye test solution in your lab notebook.
9. Allow the tofu cubes to marinate for 1 hour at room temperature.

Making Your Labels

1. Prepare a surface, with appropriate labels, on which to put the tofu cubes. Position the white piece of paper lengthwise. On the piece of paper, write the following with the permanent marker:
   1. The numbers 1 to 6, about 1 inch apart near the top of the paper. The cubes from the standards will go next to these numbers
   2. The words water, salt, vinegar, and sugar across the middle of the paper. Write the words about 1 inch apart.
2. Cover the paper with clear plastic wrap. You will put the cubes on the plastic wrap over the words that describe their treatment to keep food dye from leaking through the paper. Work on a surface that can get a little wet.
3. Using a slotted spoon, remove the two cubes from each of the standard solutions.
4. Line the cubes up on the piece of plastic wrap, with the two cubes next to each other, near their corresponding numbers, 1 to 6. This is your set of standards.
5. Using the same slotted spoon, remove the two cubes from each of the test solutions.
6. Put the cubes from each solution over the word that indicates its solution: water, salt, vinegar, or sugar.
7. Now estimate the level of color for the cubes from the different test solutions, using the standard cubes for comparison.
   1. Look carefully at the colors of the cubes from the water, salt, vinegar, and sugar solutions. Select which of the standard tofu cubes has a color that is the best match for each treatment. For instance, the tofu cubes from the sugar solution might most closely match the tofu cubes labeled "4."
8. Record the test solution tofu cube and standard tofu cube matches in your lab notebook.
   1. If any of them are darker than standard number 6, mark it as >6.
9. What was the effect of salt on the adsorption of dye? What about vinegar and sugar?
10. Clean all of your equipment and repeat the entire experiment two more times. Review all your data to determine which test solution leads to the most marinade adsorption.

Variations

• Try variations that change one of the following: time that cubes are marinated, salt concentration, temperature (room temperature vs. refrigerator), and vinegar concentration. Vary one variable at a time, keeping everything else constant. Make fresh standard cubes if they are drying out or fading.
• Some marinades have vegetable or olive oil in them. What happens if you mix oil in with the marinade?
• Try natural colorings, such as saffron or paprika.
• Experiment with a yogurt- or buttermilk-based marinade. How do these dairy products affect the marinade?
• Cut the tofu cubes with a knife after adsorption to investigate how far the dye has been absorbed into the cubes.
• Experiment with cubes of chicken breast or other meat. Caution: Raw chicken might have live Salmonella bacteria, which is a health hazard. Be careful to wash everything that comes into contact with the raw meat.

• For more science project ideas in this area of science, see Cooking & Food Science Project Ideas.

Credits

David Whyte, PhD, Science Buddies

Last edit date: 2008-12-04 12:00:00