After many years of teaching upper-level college biology classes, I realized that, to an extent, I was “preaching to the choir.” These students were already interested in the subject matter—they had, after all, chosen to major in it—and they had moderately good science backgrounds. I decided to make a bigger impact by teaching nonscience majors (many of whom have not taken biology since ninth grade).

By the time nonscience majors get to my course, they usually have forgotten much of what they learned in high school, and many hold deep-seated misconceptions. These students are smart and capable; if they have failed to grasp genetics or evolution up to this point, it is not for lack of ability. Most likely, it is because they did not make connections that enabled them to put what they learned into a context that made sense.

I attempt to provide that context by organizing an entire course around food. The Biology of Food course—a large lecture course with no laboratory section—is a mixture of kitchen chemistry, post-eating food metabolism, origins of different foods (from crop breeding to evolution), and ecological and environmental impacts of farming and harvesting practices. The material is a combination of lessons I have developed specifically for the course and information adapted from Harold McGee’s On Food and Cooking (1984). Nearly every topic begins with the introduction of one or more recipes, followed by student investigation of the related cooking methods and ingredients. This approach ties information to experiences just enough to engage students in the material. The approach is also directly transferable for use in high school biology courses. Because there is no laboratory, options are limited, but it is essential to use inquiry-based methods. Two methods used in the course are described in this article.

The bread problem

Figure 1. Two loaves of bread.

To begin the course, I arrive the first day with two loaves of bread that I made in a breadmaker (Figure 1). One loaf is light and fluffy; the other is short, dense, and very heavy. I pose the following to students: “Here we have two loaves of bread. One turned out great. The other would make a good doorstop. We need to know what happened to make these loaves turn out differently. What do we need to know to figure this out?” Students discuss the problem in groups, and together we compile a list of responses on the board. During the discussion, students focus on the following questions:

• What do we already know?
• What do we need to find out?

Students want to immediately work on solving the problem. For example, a few who have made bread before may ask, “Did you forget the yeast?” However, not everyone has this level of background and therefore it is important not to skip ahead. Students quickly discover what information is needed—the ingredients and process used to make the bread. I list the ingredients for students: milk, flour, an egg, sugar, and yeast. I state that I used the same set of ingredients for both loaves and that I put the ingredients into a bread machine and pressed “start.” The bread machine then mixed, kneaded, waited (first rise), kneaded, waited (second rise), and cooked the bread. The machine treated both loaves the same way.

At this point, students realize that they need more information before moving forward. I divide the class in half and assign some students to research flour, and the others to research yeast. I then divide the class in half again (differently this time) and assign some students to find out what happens during kneading and the others to find out what happens during rising. They all must research what happens during cooking.

The next class meeting begins with student groups discussing their research. The research is then compiled. Flour, the ground seeds of wheat, contains starch and some protein. When flour, eggs, and milk are mixed, a thick suspension of starch granules and protein molecules is obtained. Yeast is a type of microorganism (see sidebar “Yeast.”). When yeast is put into the bread dough, yeast cells eat some of the material in the dough and multiply.

During kneading, physical manipulation is used to unfold the protein molecules from the wheat seeds. The protein molecules adhere to one another, producing a network of tangled molecules called gluten. The gluten network traps air bubbles that are introduced by the kneading process.

During rising, yeast cells consume sugar and metabolize it to produce carbon dioxide (CO₂) and ethanol. The CO₂ diffuses into the air bubbles that are trapped during kneading, which causes these bubbles to expand. The dough rises because the gluten network traps the air bubbles and prevents them from escaping.

During cooking, the gas bubbles expand as the temperature increases (after all, PV = nRT). The loaf rises further—the classic “oven spring”—until the temperature is high enough for the starch to gelatinize and solidify the loaf; the high temperature ultimately kills the yeast. (Many television advertisements for store-bought chilled or frozen breads and pastries show time-lapse movies of bread, cookies, turnovers, or biscuits expanding rapidly in the oven. This rapid rise is called oven spring.)

I then ask students, “What happened with the heavy loaf that I made?” I encourage students to break the heavy loaf open to see that the ingredients are well mixed, but that the loaf contains only very small air pockets. I make sure to let students know that under no circumstances can they eat the bread—no eating is allowed in the classroom. Students conclude that the air pockets must not have expanded during the first and second rise. The easiest explanation is that the yeast added to the mix was dead, and the yeast packets used must have been expired. (I actually cheat to ensure that the second loaf doesn’t rise by microwaving the yeast.)

Students learn several things from this exercise:

• A step-by-step method of problem solving;
• How breadmaking works;
• The composition of wheat endosperm (which can be addressed when discussing seeds);
• The nature of a particular species of fungus, yeast, and some of its metabolic properties (which can be addressed when discussing fermentation and winemaking);
• The principle of protein unfolding (which can be addressed when discussing omelet-cooking and cheese-making); and finally
• Students make the connection between biology, chemistry, and physics, as they think about the chemical reactions involved, how CO₂ makes the air bubbles expand, and how cooking makes the bubbles expand even further.

Feedback from students is usually enthusiastic. Often students claim that they have “never thought about bread that way before.” Furthermore, students complete most of the work themselves, though I help them put the information together at the end.

The fish harvest scenario

I use a different “gimmick” when students start analyzing a recipe for poached salmon. I could list the fish stocks that are in decline from overfishing, describe the features of endangered populations, and encourage better stewardship of the Earth. Instead, I begin class by handing out two different printed scenarios, blue to one side of the room and orange to the other (Figures 2 and 3). The information is nearly identical on both sheets, except for one seemingly minor piece of data. Each group plays the role of biologists for a large fishing company. In this scenario, the head of the company suggests raising the harvest from 5,000 fish per year to 7,000 fish per year. I ask students, “Based on your information sheet, what would you recommend? Is this suggestion a good or bad idea?”

By giving students numbers that make the calculations easy, they can subtract the 5,000 or 7,000 fish from the total population, consider the reproduction rates and the age-to-maturity of the species, and determine whether the new harvest rate (7,000) would result in catching more fish than are produced each year. Students with the blue sheet (Figure 2) conclude that 7,000 is fine; students with the orange sheet (Figure 3) find that 7,000 is too many, and that the fish will be depleted.

The discussion is interesting because both groups perform the same calculations, with the same population size and harvest rates, but they reach opposite conclusions. This startles students. The only difference is the age-to-maturity factor (in reality, orange roughy do take quite a long time to reach sexual maturity), a characteristic that students don’t think to consider.

The numbers are imaginary, selected to make the two scenarios identical in all respects but one, and the mathematical algorithms are designed for ease of use to facilitate the comparison. Nonetheless, the comparison of the two scenarios does its job: Students are now curious about the biology. I can now address the issue, “How can we know how many fish to catch?”

At the next class meeting, each student is assigned an “identity.” Identities include politicians up for reelection, scientists, environmental activists, and CEOs of big fishing operations. This time, students are given an authentic scenario from the news (see sidebar “Lead-in to student research”). The International Commission for Exploration of the Sea (ICES) has noted that the cod fishery in the North Sea is in decline and recommend at least an 80 percent cutback of harvest rates; preferably a total ban on fishing. If enacted into law, this will eliminate 200,000 jobs (Malakoff and Stone 2002; Smith 2002; Schiermeier 2003; NOAA 2004). Then I ask students, “In your role as a ________, what would you do?“ Each group of students tries to influence their politician and come up with a response. For example, do they cut back the fish harvest by 80 percent, or do they do something else?

In general, students are on the side of the fish and accept the ICES recommendation. In reality, however, the European Union compromised on a mere 40 percent cutback.

I have found it quite helpful to use this kind of scenario in class. Students are given opportunities to discuss options among themselves and discover that they are not alone in failing to have the answer at the tips of their tongues. Students work through the scenario and discover for themselves an important scientific point related to that scenario. Their interest and understanding become apparent through in-class assessments (minute papers), overall enthusiasm, and more accurate and informed papers.

By relating the information to food, it is possible to link the science to students’ daily lives. This gives them a way to relate new information to things they already know, enabling them to learn the material more easily.

Additional food connections

Other issues exist that can be introduced through foods. Muscle physiology is an obvious choice for meat eaters. Neuron function is necessary to understand hot peppers. Genetics is needed to explain crop breeding, which is essential to understand the origin of corn, or how Europeans developed bell peppers from the hot peppers Columbus brought back from the Americas. To understand spices, it is essential to know how plants protect themselves from being eaten by producing strongly flavored compounds (sometimes toxic compounds). To understand the origins of these compounds, we must delve into evolutionary principles and plant/animal coevolution (see sidebar “Fish and soybeans”). The increasing use of genetically modified foods is all over the news, which requires understanding natural selection and biodiversity. Hamburgers lead easily to the study of bacterial antibiotic resistance. Mayonnaise is a terrific introduction for water structure, H-bonding, and hydrophobic interactions, which makes the subsequent discussion of protein folding and unfolding remarkably easy for students to follow.

The focus on food and recipes offers a particularly good entry into genetics and evolution. Where do we get bread flour and cake flour? Before the advent of the current flourmills, we used soft wheat (for cake flour) and hard wheat (for bread flour)—two varieties that are genetically distinct. In another example, I provide my favorite recipe for grilled pork tenderloin, brushed with an ancho-guajillo-pasilla dry rub, and plated on a bed of roasted sweet peppers with chipotle Hollandaise. This recipe uses five different varieties of chiles: Where did these varieties come from? These questions lead directly to a discussion of genetics, mutation, and crop breeding.

Why are mole negro, vindaloo, and Thai curry so different?  They are prepared the same way: grind up some plant materials to make a sauce for chicken.  What about ravioli, chaio tzu, and empanadas?  They, too, are prepared the same way, but are wildly different dishes.  These comparisons illustrate that variations in foods from different cultures are not necessarily the result of differences in human ingenuity.  They reflect differences in the plants and animals that are available locally.  Where do these differences come from?  The answer, of course, involves natural selection, genetic drift, and plate tectonics—natural evolutionary processes. 

By discussing crop breeding first, it is easy to present all of the basic evolutionary mechanisms using the example of crop selection by humans. This is nonthreatening even for those whose worldview holds that religious viewpoints, not evolution, describes the history of life on Earth.  Once students understand the processes, it is relatively simple to replace “humans” with “environmental factors” as the selective agent. That this approach is effective is revealed in the comments from some of my students at the end of the semester—they understand evolution much better than they did before, and most importantly, they see that it really does not conflict with their religious views.

Developing an entire course around food has been an interesting and enlightening experience. It has forced me to look deeply into my own way of thinking about the foods and techniques that I encounter every day. It has been a challenge to devise methods that allow students opportunities to practice thinking this same way. It has been enlightening to discover, in some cases, how very differently this group of nonscientists views things that I take for granted. From this experience, I can offer two main conclusions. First, it is important to tie science topics into things that my students have experienced, so that the information feels relevant to them. The focus on food is one way to do this. Second, it is important to give students time to think, interact, and question. The bread baking and fish scenarios described here are examples of ways that this can be done. Not only does this approach result in increased student learning, it also makes teaching more fun.

J. Jose Bonner is a biology professor at Indiana University, Department of Biology, 915 E. Third Street, Bloomington, IN 47405; e-mail: jbonner@bio.indiana.edu.

References

Malakoff, D., and R. Stone. 2002. Fisheries science: Scientists recommend ban on North Sea cod. Science 298:939.
McGee, H.J. 1984. On Food and Cooking: The Science and Lore of the Kitchen. New York: Scribners.
National Oceanic and Atmospheric Administration’s (NOAA) Northeast Fisheries Science Center. 2004. The North Sea Large Marine Ecosystem. na.nefsc.noaa.gov/lme/text/lme22.htm#fish.
Prakash, S. 2004. Fish Farmers Turn to Soybean Feed. National Public Radio. www.npr.org/features/feature.php?wfId=1910474.
Schiermeier, Q. 2003. Europe dithers as Canada cuts cod fishing. Nature 423:212.
Smith, G. 2002. North Sea cod on the brink of extinction. The Herald (UK) 16 October.