According to the University of Wisconsin, the yearly volume of cheese consumed in America is over thirteen pounds per person.  America is the world’s largest producer of milk products and the largest supplier of cheese to both domestic and foreign markets (Gould 2011).  Students consume a large volume of dairy products.  The American Dairy Association, supported by the National School Lunch program, makes dairy consumption a priority in the school lunch program (Gunderson 2009).  It is also a major ingredient in students’ number one food choice, macaroni and cheese (Cain-Bish 2007).

Since students consume such a large volume of this product, learning how it is produced, and the chemical processes involved in its production seems to be a natural connection for them.  The middle school science students can explore the chemical processes of the digestive system in mammals and apply those chemical processes to the creation of cheese, a natural colloid with a liquid dispersed in a solid gel.

I live on a farm, and one of my many chores is to produce cheese from our goat milk.  The process is pretty straightforward in that it is a treatment of a liquid to draw the solids out with the fats suspended within the solids.  Since goat milk is naturally homogenized, there is no cream separation step in the process.  I pasteurize the milk and add inoculants to create the flavor.  I then add rennet (a chemical naturally produced in the stomach of a calf to draw out the fats and proteins from the milk for digestion).  Alternatively, I use vegetable rennet to satisfy the desires of my vegetarian and ovo-lactate vegan customers.  The solids are placed in cheesecloth for draining and pressed to create a “wheel” or sold fresh or crumbled (farmer’s cheese, chevre’, or feta). It can be sold salted or unsalted.

One of the lessons I use to teach my students about digestive chemical reactions is the process of cheese production and creation of colloids.  The students use hot plates, food grade thermometers, sauce pans, presses, cheesecloth, and utensils.  The students work in groups of 3, and the volume of cheese per group is enough for them to spread on a few crackers.  The students learn that cheese is a byproduct of digestive chemical reactions of the rennet upon the fats and proteins within the milk.  They learn to identify the properties of a colloid, melting the cheese will release the fats and the resultant oils will liquefy. We do this with a sample of the finished cheese heated in a pan and then placed on a paper towel to show oil absorption.

The students also learn that there is more to cheese than just cheddar.  This spring, several of my goats are expecting triplets (each) sometime in mid-May.  I plan on bringing a nanny and kids to school to demonstrate where exactly milk comes from and how to milk a goat. It is my hope that they become more aware of where their food comes from and how fundamental chemistry is to their food source.

References

Caine-Bish, N., & Scheule, B. (2007). Food Preferences of School Age Children and

Adolescents in an Ohio School District. The Journal of Child Nutrition &

Management: Publication of the School Nutrition Association, (2), Retrieved

from http://docs.schoolnutrition..org/newsroom/jcnm/07fall/caine-bish/index.asp

Gould, B. (2011). Per Capita U.S. Cheese Consumption (Annual) > Per Capita Total

American Cheese Consumption . In University of Wisconsin Dairy Marketing and

Risk Management Program. Retrieved from http://future.aae.wisc.edu/data/

annual_values/by_area/2178?tab=sales.

Gunderson, G. W. (2009, May 27). The National School Lunch Program Background

and Development [report]. Retrieved from United States Department of

Agriculture: Food and Nutrition Service website: http://www.fns.usda.gov/

cnd/lunch/aboutlunch/programhistory_11.htm.