Percentage of Protein Present in Skim Milk
A Scientific Investigation by,
Waylan Washington & Max Thalhammer
The purpose of this experiment was simple, the purpose was to find the percentage of protein present in skim milk. We tested the concept that when you curdle milk with acid, and separate the curds from the liquid, you can find the true percentage of protein in skim milk. Skim milk is filled with protein and has more than 40 percent less calories than whole milk. Your body relies on more than 20 individual amino acids to support basic bodily functions. Skim milk is an excelent source of protein, because it supplies all of the essential amino acids you need. While skim milk is an excellent protein source, there are other components that make it unhealthy in large quantities. In the lab, we took a small sample of skim milk and added concentrated acetic acid. Adding this acid caused the milk to curdle. After the milk sat curdling for about five minutes, we folded a coffee filter into a funnel, and used it to filter out the acid from the protein. From that point, we set the wet filter into a box to dry overnight. When we received the dried filter the next day, we immediately massed the filter, and started making calculations. The table shown below has our masses for the filter, the dry protein plus the filter and just the protein itself. 
The milk analysis lab in our group’s eyes is viewed as a success. Our group proved, and provided the data to show the percentage of protein in non-fat milk. Also we compared it to the value print on the container. On our first day of the lab our group carefully followed the procedures, and found some trends of the lab. When we added 30 drops of concentrated acetic acid to the milk and we let the milk sit for a few minutes. The milk started to form curds. The acid denatures and coagulates the milk protein, forming these curds. Milk curds due to the pH drops and becomes more acidic , the protein molecule attracts one another and becomes curdles floating in a solution of translucent whey. It smells bad because a high level of lactic acid gives its sour smell. Our lab group found it important to find the percentage of calories in the non-fat milk due to protein, which is 51%. This percent is a very realistic answer, causing our group to view this as good and valid. The worst part of the lab was pouring the coagulated milk into the funnel. Then removing the filter paper and placing it in a massed Styrofoam cup with some paper towel packed into the bottom to absorb any liquid. This part was the worst because the process of waiting took too long. This caused a dislike to the lab. Our group had to test to see if protein was present. So we took a water test tube and the milk filtrate tube and added 1 mL of biuret reagent to each tube. We looked for the tube with a purple or bluish color to determine if protein is present. Protein was present in the milk filtrate but not the water tube.To be honest the results of this experimental lab support what we though the outcome would be. Although we had some flaws and unorganized parts and view of this lab, it was a true success. We finished the lab and found out the percentage of protein in non-fat milk, and the percentage of the value printed on the container. Also we calculate the percentage of calories in the non-fat milk. This lab was not only a success but also very fun and taught us much. The purpose of the milk analysis lab was to find out the percentage of protein in non-fat milk in 15mL carton. Then compare it to the value printed on the back of a carton of non-fat milk. My lab group found out that there is .77grams of dry protein in a 15mL of non-fat milk. We compared that .77 grams to the 8 grams of protein a full carton of non-fat milk. The difference is 7.23 grams of protein. The data that my lab group gathered showed the correct amount of protein collected in one carton of non-fat milk.
Citations:
Coffman, Melodie A. "How Much Protein in a Serving of Skim Milk?" Healthy Eating. Demand Media, n.d. Web. 23 Sept. 2014.
"Casein." Wikipedia. Wikimedia Foundation, 22 Sept. 2014. Web. 23 Sept. 2014.
"How to Make Yogurt." How to Make Yogurt. N.p., n.d. Web. 23 Sept. 2014.
"Nutrition Facts." And Analysis for Milk, Fluid, Nonfat, Calcium Fortified (fat Free or Skim). N.p., n.d. Web. 23 Sept. 2014.
"Skimmed Milk." Wikipedia. Wikimedia Foundation, 09 Mar. 2014. Web. 23 Sept. 2014.
"Why Does Milk Curdle -- and When Is It a Good Thing?" About. N.p., n.d. Web. 23 Sept. 2014.
