Milk Lab

     Greetings, Ladies and Gentlemen. To kick off the first lab of All About That Base, No Acid,  we worked with something you might have heard of, something called Milk. We used acetic acid to curdle milk and weighed the resulting precipitate to measure protein content of Skim Milk. The purpose of this was to discover how proteins can be denatured, and changed from their usual state, and also to see how some proteins are not affected by acid.

To start the experiment by we added 15 mL of milk to a 50 mL beaker. After massing both the empty (30.3grams) and filled beaker(45.6 grams), we added 30 drops of concentrated acetic acid to the milk and then waited 5 minutes to let the new mixture settle. Next, we created a funnel using filter paper and we put the settled milk through the filter to catch the developing milk curds. One in awhile we would have to stir/ scrape out things in order to make sure all the liquid went through. After we decided most of the milk and milk curds were filtered out, we set the filter in a box to sit overnight. Before leaving the classroom we poured 1 mL of water into a test tube and 1 mL of the filtered milk into another test tube. Then we added Biuret Reagent to see if there were proteins left in the certain mixture and we had water just as a control. It turned out some of the proteins ended up filtering into the milk instead of staying in the filter paper. 

Above is the milk filtering out the curds in the filter paper.

Above this is how we we stirring/scraping out some of the curds in the filter paper.

Above is us comparing water and filtered mileafter adding the Biuret Reagent. The water is on the right while the filtered milk is on the left. Since the filtered milk turned purple it means there were still proteins in the solution.

After returning to school we weighed the dried milk curds on the filter paper and it weighed 1.3 grams. 

To determine the amount of proteins we collected we subtracted the dried milk curds and the filter paper minus the weight of just the filter paper (1.3-.7) and we got a total of .6 grams of protein. Since we had 15.3 grams of regular milk to begin with we figured out that 4% of the milk was composed of proteins.after doing some other calculations we figured out that the milk was only supposed to have .509 grams of proteins and somehow we collected more than just proteins in our experiment. The expected value was .091 grams lower than the value we got, showing that we filtered out more particles from the milk than just protein. This result could have happened because the filter also filtered out non protein particles, meaning that not just protein was denatured. It could also mean that particles from our environment might have transferred to our paper plate. In the future, this might be prevented if we separated the plates from different groups more as they were laid to dry so that other people's filtered out substance didn't get on ours. These results support the expected outcome because we expected the acetic acid to denature the milk proteins, thereby causes the denatured proteins to be filtered out of the substance with a high success rate.

The purpose of this lab was to see how proteins can be denatured, and this lab illustrated the idea that pH can dramatically effect a substance by causing the protein particles to clump together.