The Yogurt Lab

Introduction:
   In order to understand this lab, it is important to understand yogurt. Yogurt is the product of a certain bacteria that changes the properties of milk into a more viscous form. Bacteria in itself is a single-celled organism that reproduces by binary fission. This means that it splits apart to copy itself and can do it quickly with the right temperatures and food supply, which makes it a very durable organism. Although bacteria does not have DNA like humans, it is found all over the planet and can be considered one of the most successful organisms. Bacteria can survive so well that scientists believe that bacteria would be able to live on other planets or moons with harsh conditions. Over the years, bacteria has been associated with harmful disease, when in fact a small amount is harmful to people. With the help of antibiotics, modern medicine took a leap forward in fighting disease, but the new 'clean' world has created super strains of bacteria that are much harder to kill, like MRSA. Without bacteria, we would not have digestion aid, waste decomposition in nature, or foods such as cheese, some breads, and of course, yogurt.

Purpose:
First, the two main objectives are to understand bacteria's role in yogurt making and to test Koch's postulates.
They are the following:

• Distinguish the "infected" population from the non-infected. Diagnose the infected and recognize differences
• Discover what bacteria is causing the abnormal change
• After discovering the cause, re-introduce said bacteria with a "pure" culture
• Reevaluate the culture for the same abnormalities that were observed, to confirm the bacteria as the source

Procedure:
The following procedure was done at home using materials that were readily available

1. Take about 50 ml of milk and heat to 80°C to kill any bacteria that may be in the milk
2. Add one eight of a teaspoon of yogurt when the milk has come to room temperature so that the bacteria is not killed in the hot temperature. 
3. Cover the milk so it is air tight and wait until it becomes thick.
4. Keep in a warm environment to help the process, an incubator at best, but a laundry room works as well. 

Controls and Variables

Having plain milk in the fridge was the control, the yogurt was testing the bacteria's effects, and the E. coli that  I observed from a friend was to test whether all bacteria makes yogurt.


Hypothesis:
The milk will not change unless there is a sudden change within the fridge. The yogurt added to the milk will convert the milk into yogurt by changing the lactose to lactic acid. The E. coli will not make yogurt.

Results:
The milk with yogurt thickened substantially, but it is not at correct "yogurt" consistency. The milk stayed the same, and other groups said that the E. coli made the milk spoil and did not thicken.

Discussion:
Overall, doing the lab at home was very informative. I did not try the yogurt yet, but I'm sure that it is fine. One source of error may include possible bacteria from the air when mixing ingredients. Through the evidence of others and mine, not all bacteria makes yogurt, and there are many benefits for bacteria in everyday life.