Flavor That Food! Exploring the Science of Marinades
AbstractHave you ever tasted a delicious burger and wondered how it got so much flavor? Maybe you have heard your family talk about marinating foods before cooking or grilling them. A marinade is a mixture of seasonings used to flavor or tenderize food. Most cooks have strong opinions about the best way to marinate their favorite food, be it a large steak or a tofu burger. In this cooking and food science fair project, you will run controlled tests to see what factors are most important in making a marinade ingredient stick to the surface of food. Get ready to maximize your marinade!
David Whyte, PhD, and Teisha Rowland, PhD, Science Buddies
Determine how various ingredients affect the adsorption of a marinade onto food.
Every culture has its own unique way of preparing food. But whether it is 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. Figure 1, below, shows raw chicken thighs soaking in a teriyaki-flavored marinade.
Figure 1. This is a picture of raw chicken thighs being soaked in a teriyaki-flavored marinade. (Image credit: Gran / Wikimedia Commons)
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. The ingredients you will be testing are salt, vinegar, and sugar. Salt can help a marinade break open animal cells, which make up a piece of meat. Salt also obviously makes foods salty, while sugar makes them sweet. But how well do these ingredients work for making a marinade be adsorbed to food? Vinegar is an acid — other acids you might find around the kitchen include lemon juice and orange juice. Acids can cause foods, like meats, to be broken down, or tenderized. Does this help make vinegar a good marinade?
While you will be testing salt, vinegar, and sugar as your key marinade ingredients, you will not be using actual seasoned marinades. Instead, along with these ingredients you will use a food dye to determine the level of adsorption because a food dye 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 and Concepts
- 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?
- What ingredients in marinades break down the proteins in meat?
Materials and Equipment
- Cutting board or dinner plate to prepare the tofu on
- 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 disposable cups, at least 9-oz. capacity (30)
- Permanent marker
- Tap water
- Measuring cups
- Food dye, blue. Alternatively, a different dark color, such as green, may be used.
- Clean spoons or other utensils to stir the liquid in the cups
- Distilled white vinegar
- Tablespoon measuring spoon
- Sheet of white paper
- Slotted spoon (or fork)
- Timer or clock
- Lab notebook
Preparing Your Materials
To start this science fair project, you should assemble all of the materials on a clean workspace.
- Have your adult helper cut the tofu block into cubes, about 2 centimeters (cm) on each side, as shown in Figure 2, below. Cut about 60 tofu cubes. Keep the unused tofu in case you need more cubes.
Figure 2. Cut the tofu into cubes like the ones shown here. (Note that this picture shows 18 cubes, but you will want to make about 60.)
- Store 40 of the tofu cubes under plastic wrap in the refrigerator so they do not dry out.
- 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.
- Using the permanent marker, label six of the plastic cups with the numbers 1-6. Line them up on your workspace in increasing order.
- Put ½ cup (C) of water into each of the six cups.
- 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.
- Stir the dye in each cup, going from the cup labeled "2" to the cup labeled "6." Your cups should now look like the ones in Figure 3, below.
Figure 3. Once you have mixed the dye in your standard solutions, they should look like the ones shown here.
Preparing the Test Solutions
Now it is time to make the test solutions. Make sure you rinse out the measuring cup and measuring spoon between making each solution.
- Label four plastic cups, as follows: water, salt, vinegar and sugar.
- To the "water" cup, add 1 C of water.
- To the "salt" cup, add 1 tablespoon (tbsp.) of salt and 1 C of water.
- Since 1 tbsp. of salt is about 18 grams (g), and 1 C of water is about 230 g, this is roughly an 8 percent solution of salt.
- To the "vinegar" cup, add ¼ C of vinegar and ¾ C of water.
- 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.
- To the "sugar" cup, add 1 tbsp. of sugar and 1 C of water.
- Since 1 tbsp. of sugar weighs about 14 g, and 1 C of water weighs about 230 g, this is roughly a 6 percent solution of sugar.
- Add eight drops of dye to each of the solutions: water, salt, vinegar, and sugar.
- Using a clean spoon or other utensil for each of the four cups, stir the cups so that the dye gets mixed in and the salt and sugar are completely dissolved in their cups. Your cups should now look like the ones in Figure 4, below.
Figure 4. Your prepared test solutions should look like the ones in this picture.
Testing the Solutions
- Carefully add two room-temperature tofu cubes to each of the solutions you prepared (the six standard solutions and the four test solutions). Do not worry if the cubes in the salt solution float.
- Record the times that the cubes go into and come out of the dye test solution in your lab notebook.
- Allow the tofu cubes to marinate for 1 hour at room temperature.
Analyzing the Tofu Cubes
- Prepare a surface, with appropriate labels, on which to put the tofu cubes, as shown in Figure 5, below. Position the white sheet of paper lengthwise. On the piece of paper, write the following with the permanent marker:
- The numbers 1 to 6, about 5 cm apart near the top of the paper. The cubes from the standards will go right below these numbers.
- The words water, salt, vinegar, and sugar across the middle of the paper. Write the words about 5 cm apart. The cubes from the test solutions will go right below these words.
Figure 5. Prepare a sheet of paper like this one for you to put your tofu cubes on (directly below the labels) and compare the cubes from the test solutions with the ones from the standards.
- Cover the paper with clear plastic wrap. You will put the cubes on the plastic wrap (directly below the words that describe their treatment) to keep food dye from leaking onto the paper. Work on a surface that can get a little wet.
- Using a slotted spoon, remove the two cubes from each of the standard solutions.
- Line the cubes up on the piece of plastic wrap, with the two cubes next to each other, just below their corresponding numbers, 1 to 6. This is your set of standards.
- Using the same slotted spoon, remove the two cubes from each of the test solutions.
- Put the cubes from each solution just below the word that indicates its solution: water, salt, vinegar, or sugar.
- Note: If not all of the surfaces on a cube are equally dyed, arrange the cube so that one of its averagely-dyed sides is facing up for you to examine and compare to the other cubes.
- Now estimate the level of color for the cubes from the different test solutions, using the standard cubes for comparison.
- 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."
- In your lab notebook, make a data table like Table 1, below. Record the test solution tofu cube and standard tofu cube matches in your data table, in the column labeled "Standard Match."
- If any of them are darker than standard number 6, mark it as >6.
(1, 2, 3, 4, 5, or 6)
|Average Standard Match
(1, 2, 3, 4, 5, or 6)
- Calculate the average standard match for the tofu cubes from each test solution. Record the averages in your data table, in the column labeled "Average Standard Match," for each test solution.
- For example, if both tofu cubes from the sugar solution matched the cubes from standard solution 4, then the average standard match for the sugar solution will be a 4.
- On the other hand, if one of the tofu cubes from the sugar solution matched the cubes from standard solution 4, and the other tofu cube from the sugar solution matched the cubes from standard solution 3, then the average standard match for the sugar solution will be 3.5
(since 3 + 4 = 7, and 7 ÷ 2 = 3.5).
- Make a bar graph of your results. Put the test solution name on the x-axis (the horizontal axis) and the average standard match numbers on the y-axis (the vertical axis). Make a bar for each test solution.
- Analyze your results. What was the effect of salt on the adsorption of dye? What about vinegar and sugar?
- Clean all of your equipment and repeat the entire experiment two more times.
- Repeating an experiment helps you make sure that your results are real and accurate.
- Review all of your data to determine which test solution leads to the most marinade adsorption.
- Overall, which tofu cubes consistently adsorbed the most dye? Which adsorbed the least?
- What does this tell you about how well the different ingredients (sugar, salt, and vinegar) stick to the surface of food? Can you explain your results?
- Hint: You may want to re-read the Introduction in the Background section and do some more research on your own to find out how the different ingredients may be working to marinade food.
Ask an Expert
- 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?
- Vinegar is an acid. You could try this science project again using other acids that you typically have in the kitchen, such as lemon juice or orange juice. How well do these other acids that you use as food marinate the tofu cubes compared to the vinegar? To find out more about which foods are acidic, check out the Science Buddies' resource Acids, Bases, & the pH Scale.
- 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.
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