by Cynthia Alonzo, MS
Too often we educators are challenged by the misconception that science classes are not necessary or critical for students without science related career goals. Yet, many issues people confront in their lives every day are science related. These can include medical treatments, disease prevention, global warming, ozone depletion, biotechnology research, alternative energies, use and management of our natural resources, and many more.. Clearly, science is all around us.
Science affects everyone, whether they understand it or not. Citizens are asked to vote on issues and make choices and decisions that will affect our society, our future, and our world. We are inundated with arguments from politicians, corporations, and activists to choose a side or take a position on a science related issue. Yet genuine understanding of these scientific issues is often lacking. A strong foundation of scientific knowledge does much more than prepare students to study science at higher levels of education. It prepares them to enter the workforce and to pursue a variety of interesting and important careers and vocations. Most importantly, science knowledge enables students to be more prepared to take part in today’s technologically-based society.
One of the barriers students face learning science is the belief that science is a mere collection of dry facts that are difficult to understand and dull to memorize. Nothing could be further from the truth! Sparking a student's interest in science is as simple as opening the door to the world around them. Understanding basic science is analogous to reading the owner’s manual of a new electronic toy. It provides the understanding and appreciation to make the most of the possibilities and potential around us.
As scientific knowledge changes and grows on a constant basis, learning can not be limited to memorization of facts that will soon be out dated. Rather, scientific education needs to be focused on learning how to discover knowledge and to solve problems. A Chinese proverb says “If you give a man a fish he can eat for a day, but if he is taught to fish he can eat every day.” Learning science is like learning to fish - it provides the student with the analytical skills needed to embark on a lifetime of discovery.
The key to helping students become more engaged and excited about science is to provide them with opportunities to actively experience science in action. Inquiry-based, hands-on science experimentation does not just focus on the absorption of facts. By actually doing lab experiments students are encouraged and challenged to think like scientists by making predictions, manipulating their environment, observing results, and developing new questions.
Hands-on science does not require an elaborate laboratory setup or expensive equipment. Science is all around us and the tools to learn about it are too! One such tool is the microbes that are found in virtually every environment on earth. We interact with microbes, both positively and negatively, on a daily basis. Our strong association with the microbial world provides the opportunity to teach core science concepts in ways that are tangible to students. This allows them to recognize scientific principles at work in the world around them and to relate those principles to their real lives. The following are two simple experiments that are fun, as well as informative. These experiments instill an appreciation for the history of food science and generate some interesting family conversations.
Microbiology Lessons via Food Preservation
Archeological evidence shows that humans have been preserving foods since 15,000 to 10,000BC. The development of technologies to preserve food literally changed the course of human history. Food preservation facilitated humanity’s change from nomadic hunter-gatherer societies to settled agricultural based societies. The ability to store food ensured a food supply that was more consistent and less dependent upon the success of the last hunt or seasonal availability. When food for more than a single day could be accumulated at one time, people were free to devote energy and resources to cultural activities such as art and philosophy and the study of science!
Osmosis: Salt has been used to preserve foods since ancient times. Salt, and even sugar, can preserve food by altering osmotic conditions. Osmosis is the movement of water across a semi-permeable membrane that allows small molecules to pass through it. Water moves through the membrane from high concentration to low concentration until the amount of water on each side of the membrane is equal. Living cells are surrounded by semi-permeable membranes called the cellular membranes.
Osmosis can be observed when a limp celery stalk or carrot is placed in water and it subsequently becomes firm. The vegetable became limp because the water it contained passed through its semi-permeable skin into the environment’s air which had a lower concentration of water than the vegetable. Once placed in water, the vegetable’s surrounding environment has a higher concentration of water than the vegetable; this causes water to flow back across the skin into the vegetable.
As single celled organisms, bacteria are particularly sensitive to osmotic changes. It is this sensitivity that makes the salting of food an effective method of preservation. A coating of salt causes water to flow through the membrane from the food cells to the environment. This movement of water preserves the food in two ways. First, the loss of water from the cells kills bacteria that may be present on the food. Second, the presence of high salt conditions on the surface of the food creates an environment that is toxic to many microorganisms so the food is protected from further spoilage.
Observing Osmosis Activity: You will need:
two eggs of equal size
container large enough to submerge eggs for soaking
two clear glasses large enough to submerge an egg
1. Soak both eggs in vinegar for approximately 48 hours. The acetic acid in the vinegar will dissolve the calcium carbonate that is the main component of the egg shell. Once the shell is dissolved, the semi-permeable membrane that surrounds the egg will be exposed.
2. Use a spoon to carefully remove the eggs, one at a time. Place the first egg into a clear glass containing water and the second into a clear glass containing corn syrup. The level of liquid in each glass should be enough to submerse the egg.
3. Observe the eggs after 30 minutes and again at one hour.
Both eggs will show visible evidence of osmosis. The egg placed in the water will swell in size as water from the glass flows across the membrane and into the egg. The egg placed in corn syrup will shrink in size as water flows across the membrane from the egg into the corn syrup. If a scale and a measure tape are available, they should be used to weigh and take the circumference of the eggs before and after osmosis so that the observation can be quantified as it would be in a formal lab.
Fermentation: Fermentation is the biochemical conversion of sugars, starches, or carbohydrates into alcohol and organic acids. The fermentation of foods predates written history and is one of the oldest methods of preserving perishable foods. Preserving by fermentation not only makes foods available for future use, but, in many cases, makes them more digestible, nutritious and flavorful.
Foods preserved or made by fermentation are found in all cultures. The list is virtually endless and ranges from the obvious of alcoholic beverages, pickles, yogurt, bread and cheese to the unexpected such as chocolate, soy sauce, coffee, tea, and MSG.
Bacteria, yeast or fungi can be used to provide fermentation depending on the type of food to be preserved. Fermentation works to preserve food primarily because desirable microbes slow the deterioration of the food by inhibiting the growth of spoiling types of microorganisms. Some fermenting processes lower the pH of foods and this creates an acidic environment that prevents the growth of harmful microorganisms. Essentially, fermentation encourages the growth of good microorganisms while preventing or inhibiting the growth of bad microbes.
Foods cured in a brine solution of salt, water, and sometimes sugar and spices are naturally fermented, or pickled, using microorganisms found on the food. During the curing process, desirable bacteria convert carbohydrates to acetic acid that “pickle” and preserves the food. The brine also protects food from spoilage by organisms that can not grow in the high salt solution. Most types of bread are made by the process of fermentation. When yeast eats the sugar in the bread dough, it creates bubbles of carbon-dioxide gas that cause the dough to rise and double in size.
Creating Fermentation Activity: You will need:
1 container of commercially-prepared plain yogurt (natural style is best)
1 quart of milk, add 1/3 cup powdered milk to the milk for thicker yogurt
a measuring cup
a candy thermometer
a clean quart-sized glass container
1. Warm the milk in a pan until a skin forms at the surface. The thermometer should read 160 degrees F. This kills any germs that may spoil the milk before the yogurt forms. Then cool down the milk to 110 degrees F.
2. To 1/2 of the container of yogurt and add an equal amount of warm milk and mix thoroughly. Then add the rest of the yogurt and stir to make a "starter" culture.
3. Gently blend the starter culture with the rest of the milk in the pan.
4. Pour the entire mixture into the glass container and wrap a towel around it to seal in the heat. Let the yogurt culture stand undisturbed at room temperature, covered or uncovered, for 8-12 hours. The fermentation is complete and the yogurt is done when gently tilting the container causes the yogurt slides away from the side of the jar in one piece.
5. Store the finished yogurt in the refrigerator to stop the bacterial growth. This yogurt can be eaten plain or mixed honey, fruit, or jam.
Professor Cynthia Alonzo is the author of a microbiology lab manual around which the MBK LabPaq (www.LabPaq.com) produced by Hands-On Labs, Inc. was designed and developed. Cindi has a BS in Genetics, a MS in Molecular Biology, and an MS in Education. She began her science career working as a researcher in virology and molecular biology. Then as a favor to a friend, she agreed to teach a one-semester microbiology course in her spare time. She soon found she loved teaching far more than her research career. As she began to focus more on teaching, a desire to be an outstanding educator drove Cindi to return to school for an MS in Education. She has been a full time college professor ever since. Cindi began teaching microbiology courses online for CCC-Online in 2000. She strongly believes that online instruction will play an increasingly larger role in the future of education and wants to ensure rigorous lab science courses like microbiology are not left behind. For this reason, Cindi chose to work with the dedicated educational professionals at Hands-On Labs, Inc. (www.LabPaq.com) who offer academically aligned, single student/single use laboratory experiments in a box for course specific science classes. She is delighted to be a part of a company that shares her sincere dedication to the advancement of science education and science literacy around the world.