| Unit III Objectives |
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The students will learn:
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So far, we have been talking about cells and how genetic changes occur. But that is not the only thing happening in organisms: different processes take place naturally in organisms in order that they can grow, move, and maintain themselves. Let us turn our attention to a common biological process: fermentation.
As you probably know, this process has been harnessed to produce a number of foods that we enjoy today, e.g. cheese, yogurt, apple cider, etc. Before we study the significance of fermentation in biotechnology, let us first understand how it occurs in natural settings.
One of the basic jobs cells do is to produce energy constantly. To do this, cells break down the food taken by the organism. In most organisms, a key component of this process is oxygen. However, there is also a kind of back-up system that will provide energy if oxygen is missing.
This system or process is known as fermentation. Fermentation is one method by which organisms, including human beings, derive their energy for living when oxygen (O2) is lacking. Normally, when oxygen is plentiful, the cells of most organisms break down sugars and starch from food to release carbon dioxide (CO2), water (H2O), and energy.
When oxygen is insufficient, cells in organisms switch to the fermentation process to provide that energy. Our body cells are also able to switch to fermentation, e.g., during strenuous exercise, when we cannot take in oxygen quickly enough. Like the normal process, fermentation also breaks down sugars, releasing carbon dioxide (CO2) and energy. In addition, depending on the type of fermentation, lactic acid or alcohol is produced. These are the two most common types of fermentation naturally occurring in nature. Our muscle cells produce lactic acid during fermentation. This causes the pain that we feel in our muscles.
Breakdown of Sugar when Oxygen is available.
Sugar + O2 CO2 + H2O + energy
Various foods such as food and fruit juices will ferment when left on their own. Invisible to the eye, single-celled microorganisms such as yeast and bacteria are at work, breaking down the sugar molecules present.
When we deliberately introduce living organisms into our bread, milk, and apple juice, we are applying biotechnology to food production. Indeed, sugars in the dough, juice, and milk are food for these microscopic organisms. The carbon dioxide and lactic acid or alcohol are really waste products for these organisms but are useful for human beings.
Different types of yeasts or bacteria used will yield different by-products, providing variety to our tastes. We can obtain different wines and beers depending on the type of bacteria or yeast we use. In baking, it is the CO2 that makes the dough rise.
Fermented products also last longer. The fermentation process preserves foods. This is why fermentation was a popular preservation method in the days before refrigeration.
Fermentation technology has its share of limitations, a few of which are listed below.
The word manipulate or control may evoke some fears that human beings are tinkering with nature and life. However, human beings have influenced the course of nature since the dawn of civilization. A long time ago, people used to travel long distances to gather wild grain and fruit and to eat.
Later, they found that the seeds from their food began to grow where they were left behind. Soon, they began to plant the seeds near their dwellings. Thus, began the earliest form of agriculture. In so doing, wild plants were being "domesticated" or tamed.
Similarly, our early ancestors used to hunt animals for meat. However, they found out that some animals could be reared in their villages, and so was born the domestication of wild animals. Soon, they also found that animals could help them in doing work and animals like horses were reared not so much for their meat but for their strength.
People also found that fermented foods were tasty and was a form of preservation e.g. cheese and wines. Without fully understanding what was taking place, our ancestors were making use of natural processes and manipulating genetic traits. This manipulation became a part of everyday life.
Selective breeding and fermentation techniques were developed over many centuries and were tied to the way of life of the ordinary people: farming, cattle-rearing, baking, weaving, making dairy products, establishing beautiful gardens, brewing beer, etc.
Every family produced their own food and other daily needs on a small scale. They were able to enjoy the fruits of their own labor, the products of biotechnology, in their own homes. In the days when electricity was yet undiscovered and the refrigerator yet uninvented, fermentation contributed greatly to extending the shelf lives of food products.
As such, these ancient practices, even though they were a form of tampering with nature, were widely accepted. In fact, we can say that biotechnology was an integral part of cultural norms.
Today, the scenario is rather different. With increased urbanization, more and more families no longer produce their daily requirements themselves. Instead, they depend on farmers and industry.When food and other items are being produced for hundreds of thousands of people at a time, some safeguards need to be in place and somebody has to check that these standards are met.
Setting and checking standards is a way our society regulates what is acceptable. This includes both the process of manipulation and the outcome.
There are several concerns which require monitoring:
Both the risks and benefits need to be considered, especially as we develop the new biotechnology, which we shall explore in Unit IV.
| Materials |
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| Purpose of Activity |
| Use this activity to discuss food preservation and variety in general and introduce how fermentation biotechnology allows us to achieve a similar aim. |
Discuss how fermentation is used in food processing. During the discussion, guide students in peeling and slicing the washed cucumbers and onions (or have this prepared).
Lay the cucumber and onion slices in the bowl. Cover with equal amounts of vinegar and water.
Let this sit for a while (perhaps proceed with the next activity, "Then and Now"). Have the students taste the cucumbers and onions.
Explain that the acid in the vinegar stops microorganisms from growing. Thus, the sugars and starch in the cucumber and onions are not broken down. They now taste different and can be preserved for a longer time than when they were fresh. Although this is the opposite action to fermentation of food, the aim is similar: to create a new product that has a longer shelf life and a different taste.
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| Purpose of Activity |
| Use this activity to discuss the usefulness and history of fermentation and other methods of food preservation. |
On the board, create a chart that looks like this:
Talk about the fruits in the activity "Fruitful Choices."
Have the students imagine they are living in the mid-1800s. Point out that there is no refrigeration.
On the chart, write down the food categories:
"Meats," "Fruits," "Vegetables," and "Dairy." For each, identify ways in which the foods were preserved.
Next, ask the students to think of all the ways in which foods are "preserved" (or their shelf lives extended) now.
Explain that despite the enormous increase in new methods since the 1800s, people have not rejected the old methods of fermentation. This is partly because the technique and the tastes of fermented foods have become a part of human culture and life. If you were Chinese, can you imagine going without soy sauce? How would an oil and vinegar salad dressing taste without the vinegar? And what if you never got to eat cheese ever again?
Explain that in making use of organisms and natural processes, people wanted to improve product quality, increase efficiency of production and raise the quality of life.
Introduce the term biotechnology as the use of biological organisms, systems, or processes to make or modify products. Explain that selective breeding and fermentation for food are examples of old biotechnology, practiced for thousands of years.
| Sample Chart: Then and Now | ||
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| Then | Now | |
| Meat | salted pickled dried | salted pickled dried refrigerated frozen irradiated canned |
| Fruit | preserves--jellies, jams canned pickled dried juiced | preserves--jellies, jams canned pickled dried juiced refrigerated frozen irradiated genetically controlled chemically treated |
| Vegetables | canned dried pickled | canned dried pickled juiced refrigerated frozen irradiated genetically controlled chemically treated |
| Dairy | cheese soured | cheese dried/powdered pasteurized aseptically packaged refrigerated chemically treated |
| Purpose of Activity |
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| Use this activity to illustrate fermentation biotechnology at work. |
There are several simple ways to show fermentation at work. These activities take time to complete, some may require several hours for results to appear.
Refer to the description of the suggested activities.
Here are a few suggestions:
1. Make some bread.
| Materials |
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3 to 3-1/2 cups bread flour |
Students will work in pairs. They will need guidance. If there is no oven available, it may be necessary to leave this activity toward the last hour of the day. Make sure there is enough time for clean-up too.
Before the activity, grease enough self-locking freezer bags for each pair of
students and place the following ingredients in each bag:
1-1/2 cups bread or all-purpose flour
1 package rapid rise yeast
2 Tablespoons sugar
1 teaspoon salt
Also prepare aluminum bread pans for students to place their dough in. You may wish to have their names written on the foil. Students may take the bread dough home in the aluminum pans placed in freezer bags. Do NOT place aluminum pans into microwave ovens.
Line work tables with wax paper.
Have all students wash their hands before the activity. Distribute one bag to each pair. Show students the dried yeast and then place half the yeast in each bag. Tell the students that yeast are single-celled plants which are going to help us make the bread. Pour half the water in each bag. Ask the students to close the bags and mix the ingredients well by hand. Allow the dough to rise.
Remove the dough from the bag and show the students how to knead it. Add a small amount of flour to the dough if necessary.
Divide the dough into two portions, one for each student. If using a conventional oven, place the dough in the aluminum foils that has been lightly sprayed with oil. If using a microwave oven, place in microwaveable plastic bags.
If you can bake the bread, ask students to describe the smell or aroma from the oven. Or, ask the students to take note while they are baking their bread at home.
Point out that in order to make the bread rise, we need to add yeast. Yeast is a single-celled plant, the tiniest in the world. Yeast gives off carbon dioxide gas during fermentation. The gas gets trapped in the flour particles, making the bread rise.
The yeast also releases alcohol during fermentation. This produces the sweet aroma. The alcohol is eventually driven off in the process of baking. When the temperature gets too hot, fermentation stops as the yeast cells die.
Like other living organisms, yeast cells go through mutations and those that ferment quickly were found and cultivated. Thus, we can now enjoy the time-saving benefits of the "rapid rise" yeast.
You may also wish to demonstrate that carbon dioxide gas is in fact produced during fermentation of yeast.
Place about half a pound of grapes in a perforated vegetable bag which can be closed. Carefully squeeze out all the air and then lock it. In a freezer bag without any holes, place 2 tsp of dried baker's yeast. Place the bag of grapes in the freezer bag and close it.
Crush the grapes without opening the bags, allowing the grape juice to seep through the holes and become mixed with the yeast. Place the bags in a warm place and watch what happens in the next hour. There should be foam and gas filling the bag. To test for carbon dioxide, introduce a lighted match into the bag. The fire will be extinguished.
2. Make some cream or cheese.
Before the activity, have students taste some commercially available varieties of dairy products: yogurt, milk, heavy cream, sour cream, and various cheeses.
Explain that making these products involve little helpers called bacteria, which are still alive in the finished products.
Details of the procedures and materials needed can be found in More Science Experiments You Can Eat by Vicki Cobb (J. B. Lippincott, 1979).
If you wish to try making yogurt, you can look up Science Fun with Dairy Foods by Robert L. Horton (Ohio State University Extension Publications, 1989) or Recipes for Science Fun by Susan Strand Noad (Franklin Watts, 1979).
Note: To make cheese and yogurt will require cooking utensils and a stove or a burner.
Explain that the sour tastes comes from the acid that is produced by the bacteria during fermentation. Not only does it change the taste, it thickens the milk to form a custard-like appearance. Given time, the acid will "curdle" the milk. By separating the solid portion, the curds, from the liquid portion, the whey, cheese is formed.
Whey is a waste product in cheesemaking. Alternative uses for whey have to be found or it can be a waste disposal problem when cheese is manufactured in a large quantity. This is one limitation of fermentation biotechnology.
Fermentation is a living process. We can only make these foods by using live bacteria and yeasts. Different types of bacteria and yeasts will release different types of acids and alcohols. Thus, we have to ensure that the products contain the pure type and are not contaminated with other bacteria which can spoil the food and make us sick. This is the reason that we have to wash our hands and utensils well. The "active cultures" found in the commercial dairy products are of the appropriate bacteria. Thus, we can use them to make more food.