Uji Coliform - MPN Tahap 1 Uji Penduga

Summary

This video script explains the process of identifying E. coli bacteria in food and beverages using the Most Probable Number (MPN) method. The process includes three main steps: dilution, incubation, and observation. The first step involves preparing samples through serial dilutions and placing them in test tubes. In the second step, the samples are incubated at 37°C for 24 hours, and the presence of E. coli is indicated by gas bubbles or turbidity. If no reaction is observed, the process is repeated. The final results help determine whether E. coli is present in the sample.

Takeaways

• 😀 The MPN (Most Probable Number) method is used to detect E. coli in food and beverages.
• 😀 The procedure begins with sample dilution into different concentrations (10^-1, 10^-2, 10^-3) using distilled water.
• 😀 Each dilution is placed in separate test tubes for further incubation and testing.
• 😀 In addition to test tubes, Durham tubes are used to detect gas bubbles, indicating the presence of E. coli.
• 😀 Lactose broth medium is used for incubating the samples, which remains liquid and does not solidify like agar.
• 😀 The samples are incubated at 37°C for 24 hours initially to promote bacterial growth.
• 😀 If no gas bubbles or turbidity are observed after 24 hours, the samples are re-incubated for another 24 hours.
• 😀 Gas production or changes in turbidity after incubation indicate a positive result for E. coli.
• 😀 If positive signs are detected, further confirmation tests are conducted using the positive tubes from the first round of testing.
• 😀 Negative results are concluded when no signs of gas bubbles or turbidity are found even after 48 hours of incubation.

Q & A

What is the purpose of the Most Probable Number (MPN) method?

The MPN method is used to estimate the population of coliform microbes, specifically E. coli, in food and beverages.

What are the three main steps in the MPN method?

The three main steps in the MPN method are: 1) Preliminary test (uji penduga), 2) Incubation, and 3) Observation of results (looking for bubbles or turbidity).

What materials are required for the preliminary test in the MPN method?

For the preliminary test, you need sterilized equipment and materials, including test tubes, Durham tubes, and Lactose Broth media.

How is the sample diluted in the MPN method?

The sample is diluted through a series of steps: 1 ml of the original sample is added to 9 ml of water to create a 10^-1 dilution, and further dilutions are made to 10^-2 and 10^-3.

Why are Durham tubes used in the MPN method?

Durham tubes are used to detect the presence of gas bubbles, which indicate the growth of E. coli, as part of the observation process in the preliminary test.

What role does Lactose Broth play in the MPN method?

Lactose Broth is a liquid medium used to support the growth of coliform bacteria, including E. coli, during the incubation phase of the test.

What is the incubation process in the MPN method?

In the incubation process, the samples are placed in an incubator at 37°C for 24 hours to allow bacterial growth and potential gas production.

What happens if no gas or turbidity is observed after the first 24 hours of incubation?

If no gas or turbidity is observed, the sample is incubated for another 24 hours. If there is still no change, the result is considered negative for E. coli.

How is the result interpreted if gas or turbidity is observed after incubation?

If gas or turbidity is observed, the sample is considered positive for E. coli, and further testing is done to confirm the presence of the bacteria.

How are the test results further analyzed after incubation?

After incubation, the test tubes are analyzed for the presence of gas or turbidity. Positive tubes are identified, and further testing is conducted using only those positive samples (e.g., A1, A2, B1, B2, and C1).