Quantifying Microbes In Milk And Water
Quantification of Microbes in Milk and Water
Naomi Hall
10/20/14
BSC 381L H003
Group: Megan Baker, Katie Coe and Meagan Williams
Abstract
Coliforms are gram negative bacteria commonly found in the intestines of birds and mammals and are the most widely utilized indicators of fecal contamination. The purpose of this experiment was to test various water and milk samples for the presence of coliforms, specifically fecal coliforms. It was expected that fecal coliforms would be found in all water sources with the exception of the bottled and tap water. It was also expected that there would be little to no coliforms in the milk that had been pasteurized as compared to the raw milk which had not been pasteurized. To test the …show more content…
Each group was assigned a different water sample from either bottled water, Lake Byron, Campus Creek, Tap water, or Littlejohn Lake. The sample our group was assigned was the Campus Creek water sample. For the first lab session we began by labeling 5 double-strength and 10 single-strength lactose broths with our group information, section number and which sample we were testing. We labeled five of the single-strength tubes 1.0ml and the other five 0.1ml. We then shook up the water sample vigorously and then transferred 10ml of the water to each of the five double-strength lactose broths, 1.0ml of the water to the single-strength lactose labeled 1.0ml, and 0.1ml of the water to the single-strength lactose labeled 0.1ml. After transferring the water samples to the broths, the tubes were placed in the incubator at 37°C for 24 hours. After 24 hours the tubes were examined to see if any of the tubes had bubbles (indicating gas production) and if there was a change in color from red to yellow (indicating production of acid). To confirm gas-producing bacteria were coliforms, we chose one positive tube and inoculated an EMB plate and incubated the inverted plate at 37°C for an additional 24 hours and then at room temperature until the next lab session.
For the second lab session we observed the EMB plate looking for colonies with a metallic sheen or glossy sheen. We then selected a suspected coliform …show more content…
This is also consistent with what I anticipated in my hypothesis. I hypothesized that there would be a lower number or no microbes/coliforms in the milk samples that were pasteurized than in the raw milk (due to raw milk being unpasteurized). Raw milk had the highest standard plate count and was the only sample to contain coliforms. I believe that most samples contained bacteria because many foods contain a healthy amount of bacteria which are not harmful to the body and because while pasteurization reduces the amount of bacteria in milk, it does not kill all the bacteria. I believe that there was a large amount of bacteria and coliforms in the raw milk because raw milk is not pasteurized and nothing is done to it to kill the microbes contained in the
Naomi Hall
10/20/14
BSC 381L H003
Group: Megan Baker, Katie Coe and Meagan Williams
Abstract
Coliforms are gram negative bacteria commonly found in the intestines of birds and mammals and are the most widely utilized indicators of fecal contamination. The purpose of this experiment was to test various water and milk samples for the presence of coliforms, specifically fecal coliforms. It was expected that fecal coliforms would be found in all water sources with the exception of the bottled and tap water. It was also expected that there would be little to no coliforms in the milk that had been pasteurized as compared to the raw milk which had not been pasteurized. To test the …show more content…
Each group was assigned a different water sample from either bottled water, Lake Byron, Campus Creek, Tap water, or Littlejohn Lake. The sample our group was assigned was the Campus Creek water sample. For the first lab session we began by labeling 5 double-strength and 10 single-strength lactose broths with our group information, section number and which sample we were testing. We labeled five of the single-strength tubes 1.0ml and the other five 0.1ml. We then shook up the water sample vigorously and then transferred 10ml of the water to each of the five double-strength lactose broths, 1.0ml of the water to the single-strength lactose labeled 1.0ml, and 0.1ml of the water to the single-strength lactose labeled 0.1ml. After transferring the water samples to the broths, the tubes were placed in the incubator at 37°C for 24 hours. After 24 hours the tubes were examined to see if any of the tubes had bubbles (indicating gas production) and if there was a change in color from red to yellow (indicating production of acid). To confirm gas-producing bacteria were coliforms, we chose one positive tube and inoculated an EMB plate and incubated the inverted plate at 37°C for an additional 24 hours and then at room temperature until the next lab session.
For the second lab session we observed the EMB plate looking for colonies with a metallic sheen or glossy sheen. We then selected a suspected coliform …show more content…
This is also consistent with what I anticipated in my hypothesis. I hypothesized that there would be a lower number or no microbes/coliforms in the milk samples that were pasteurized than in the raw milk (due to raw milk being unpasteurized). Raw milk had the highest standard plate count and was the only sample to contain coliforms. I believe that most samples contained bacteria because many foods contain a healthy amount of bacteria which are not harmful to the body and because while pasteurization reduces the amount of bacteria in milk, it does not kill all the bacteria. I believe that there was a large amount of bacteria and coliforms in the raw milk because raw milk is not pasteurized and nothing is done to it to kill the microbes contained in the