Students explore the scientific processes used to make the crops we grow and the livestock we raise (commodities) into some of the foods we eat every day. Students will discover how science and technology work together to create foods like pickles, bread, yogurt and more! To engage further in the topic, students will make their own cheese using enzymes produced through the fermentation of genetically engineered yeast.  Grades 6-8

highly processed foods: foods that have many ingredients and are mostly or fully prepared in the factory so they require little or no preparation before eating

minimally processed foods: foods are changed only a small amount between the farm and the consumer; these foods have few ingredients (often only one) but might be washed, peeled, sliced, juiced, frozen, dried, or pasteurized

rennet: a complex set of enzymes produced in the stomach of young ruminant animals

ruminant: an animal that uses a series of stomach compartments and chews its cud in order to digest plant cellulose

United States Department of Agriculture (USDA): a federal agency responsible for developing and executing federal laws related to farming, forestry, and food

There is a lot of science to explore in the foods we eat every day. This lesson focuses on the science that takes place between the harvest of raw commodities from the farm, to the product that ends up on grocery store shelves. Science plays a role in processing wheat into bread, milk into a variety of dairy products, cucumbers into pickles, and much more.

Most people initially think of processed food as being less healthy than whole foods, especially when considering highly processed foods like premade meals. These convenience foods are often high in refined sugars, sodium, and fats. However, the USDA (United States Department of Agriculture) defines a processed food as one that "has undergone any changes to its natural state—any raw agricultural commodity subjected to washing, cleaning, milling, cutting, chopping, heating, pasteurizing, blanching, cooking, canning, freezing, drying, dehydrating, mixing, and packaging."⁴ Each of these food preparation practices are known as "processing," but don't necessarily decrease the nutritive value of the food. Some even increase the concentration of nutrients. For example, milk can be processed into cheese, this is an old, some may say ancient, food process. After processing, some cheeses have more protein per serving than the milk used to create it. Cheese also has a longer shelf life than milk and adds variety and flavor to our diet. Milk can also be processed into yogurt which has beneficial bacterial cultures that aid in digestion. 

Food packaging science and technology has improved the shelf life of fresh fruits and vegetables. Fresh produce has a lot of value in a healthy diet, but there are inherant challenges for distribution. Many meats, fish, fruits, vegetables, and dairy products stay fresh for only a few days before they begin to spoil. The secret is in the packaging. Modified atmosphere packaging (MAP) fills a food package with a gas or gas mixture other than oxygen. In most cases nitrogen and carbon dioxide. Oxygen promotes spoilage and the growth of aerobic microorganisms. Food products packaged with MAP stay fresh significantly longer.⁷ 

Science and technology can also be used to overcome challenges in our food system. In 2020 approximately 13.25 billion pounds of cheese were produced. The most common enzyme used to transform milk into cheese is Rennet. Rennet causes the milk to coagulate and is used to make hard cheeses.⁵ It helps the milk mixture separate the forming curds from the whey. Rennet splits off the hydrophilic portion of the casein micelles so it will no longer stay suspended in the aqueous solution of milk. Instead, the casein aggregates together to form the curds, while the whey (or liquid portion) separates.⁶  Rennet is found naturally in the stomach lining of a young ruminant animal such as a calf, goat, or sheep. Rennet helps young ruminants digest milk by curdling it. Rennet is not a primary product of raising ruminant livestock, but can be collected as a by-product. Calves raised for veal are the most common source of animal rennet in the United States. As demand for cheese grew in the late 20th century, scientists began searching for alternatives to calf rennet. The veal industry in the United States was (and is) too small to support the entire cheese industry. Fermentation Produced Chymosin (FPC) is the most technologically advanced form of rennet used in cheesemaking. It was approved for use by the FDA in 1990.⁸ FPC is useful because the enzymes in the formulations can be altered and closely controlled to produce desirable flavors in the final aged cheese. FPC comes from cultured yeast cells that have been introduced with genetic information that allows them to produce enzymes such as chymosin, pepsin, and lipases that are identical to those found in animal rennet. FPC is suitable for consumption by vegetarians and it can be produced in quantities that match the market demand.

1. Ask students if science is part of their food. Allow students to think about the question and offer answers.
2. Project the Eating Science Food Collage image on the board. Ask students if they can identify any scientific processes that were used to create these processed foods. 
3. Discuss what a processed food is. Explain that food processing takes a whole, raw food/commodity produced on the farm and prepares it for retail sale. Examples can be as simple as washing and slicing fruits and vegetables. Food processing can also involve some science such as transforming milk into cheese, butter, or yogurt and turning a cucumber into a pickle or sugar into candy. Food processing relies on science.

Correct misconceptions your students may have about all processed foods being "bad." News and headlines often communicate negative messages about processed foods. While heavily processed foods such as premade meals and microwaveable dinners are known to contribute to high blood pressure, diabetes, and obesity, there are many other forms of food processing that produce a variety of healthy eating options. To engage your students with this concept, ask them to consider eating wheat seeds instead of milling the seed to make flour. Then ask what other commodities would be limited for consumption without processing.

Activity 1: Biotech Cheese

1. Explain to students that you will be giving them a list of clues leading them to the food they will be investigating. Instruct students to raise their hand when they think they know the food you are describing. Provide the following clues:
   • It is believed that this food was discovered anciently by accident due to the pouches that were used to store food prior to glass and plastic.
   • This food has over a thousand varieties throughout the world.
   • This food is created using science.
   • It is high in protein.
   • It is a processed food.
   • Wisconsin produces the most of this food. California and Idaho come next.
   • All varieties of this food are made from milk.
   • Processing milk into this food product increases it's shelf life and the versatility of the food. 
   • It can be eaten raw or as a cooked ingredient in foods. (Cheese!)
2. Watch A Brief History of Cheese. Ask students to pay attention for the name of an enzyme that is used to make cheese and where that enzyme is found. 
3. Students should have identified rennet as the enzyme used to make cheese and that it is produced in the stomach of some mammals. Help students make basic science connections to comprehend that digestive systems (in humans and animals) create enzymes that chemically break down food. Young animals such as goats, sheep, and calves rely on milk from their mother to grow and be healthy. The lining of their stomach produces the enzyme, rennet to digest milk.
4. Explain that historically rennet (from the stomach) was harvested as a byproduct when young animals were harvested for meat. In the United States, veal (meat from a calf still drinking milk) is a very small industry in relation to the amount of cheese we consume. Cheese processing plants needed a new source for rennet that could be produced in large quantities to meet the demand for cheese.
5. As a rule, a students should not eat in a science lab or eat any substances or products created in a science lab. However, this science lab may be an exception and perhaps moved to a classroom not inside of a lab. Once this is sorted out, introduce the investigation explaining that you'll be making two batches of cheese—one using traditional calf rennet and one using the rennet that can now be created using biotechnology.
6. Follow the instructions found in the Biotech Cheese recipe. An illustration of the lab can also be found in the Biotech Cheese Demonstration video. 
7. When the cheese is ready, follow appropriate hand washing practices and allow students to compare the two cheese samples. Provide crackers or another compatible food to pair with the cheese. Instruct students to observe the look of the cheese samples and then to compare the flavor and texture.
8. After students have had a chance to test both samples, reveal the cheese that was made with traditional calf rennet and the cheese that was made with Fermentation-produced Chymosin (FPC). Project the graphic to describe both types of rennet. 
9. Discuss the benefits of implementing technology in food processing. Are there any drawbacks or challenges as well?

Activity 2: Science in Food Processing

1. Refer back to the Eating Science Food Collage image from the Engagement section of the lesson. Explain that you are going to explore a little more of the science involved in creating these foods.
2. Divide the class into 9 teams. 
3. Give each team one Eating Science Food Card. Depending on the time you have available, have each team research their food card and share with the class the science involved in processing the food on their card.
   • If time is short, have students read the brief explanation on their card and do their own (10 minute) research to understand it further. Have each team take 1-2 minutes to share with the class.
   • If you have adequate time, have students create an interactive infographic describing each step in the process of creating their food. Share the infographics with the class.

After conducting these activities, review and summarize the following key concepts:

• Food processing includes any process that takes place between the farm and the grocery store. It could include washing, cutting, heating, pasteurizing, cooking, mixing, packaging, or any other procedure that alters the food from it's natural state.
• Processing can add nutrition value to food as well as variety to our diets. (With the exception of highly processed, pre-made meals.)
• Many scientific processes are used in the creation of our foods.

1. https://nationalhistoriccheesemakingcenter.org/history-of-cheese/
2. https://www.popcornforthepeople.com/blogs/blog/11-fun-facts-about-cheese
3. https://exploratorium.edu/cooking/pickles/history.html
4. https://www.hsph.harvard.edu/nutritionsource/processed-foods/
5. Say Cheese! A Kid's Guide to Cheese Making. Ricki Carroll and Sarah Carroll
6. Foods Experimental Perspectives. 7th edition. Margaret McWilliams
7. https://www.lasercomponents.com/us/news/in-state-of-the-art-high-tech-packaging-food-stays-fresh-longer-3/
8. https://www.vrg.org/blog/2012/08/21/microbial-rennets-and-fermentation-produced-chymosin

• Biotech Cheese Kit
• Food Chemistry Experiments
• Gourmet Lab: The Scientific Principles Behind Your Favorite Foods
• Hilmar Cheese Company Virtual Video Tour
• Say Cheese! A Kid's Guide to Cheese Making