Analysis Of Casein Lab Report

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Protein Casein DCP & CE
Hypothesis:
Casein is made up of many individual amino acids. Each of them may have positively charge or negative charge depending on the pH of the milk. At certain pH value, positively charges and negatively charges of the casein will equal, so that the number of electrons equals to the number of protons. [1]
Approximately pH 4.6 is the pH value that acid casein is precipitated and least soluble. In milk, which has a pH of about 6.6, the casein has a net negative charge and is quite stable. However, if there is addition acid adds to the milk, it decreases the pH of casein. Therefore, less casein precipitates when pH value is lower than 4.6. [1] Furthermore, if the pH value is very low, some of the casein will be dissolved
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It is because more acid adds to the milk; it will decrease the pH of casein more, and less neutral casein will precipitate as few of casein will precipitate and dissolve again. [1] [2]
For 15% acetic acid, less casein will be precipitated, as the concentration of pH is higher, the pH of milk will be lower than pH 4.6 from pH 6.6. It is because more acid adds to the milk; it will decrease the pH of casein more, and less neutral casein will precipitate as more casein will precipitate and dissolve again. [1] [2]
For 20% acetic acid, less casein will be precipitated, as the concentration of pH is higher, the pH of milk will be lower than pH 4.6 from pH 6.6. It is because more acid adds to the milk; it will decrease the pH of casein more, and less neutral casein will precipitate as more casein will precipitate and dissolve again. [1] [2]
For 25% acetic acid, least casein will be precipitated, as the concentration of pH is highest, the pH of milk will be lower than pH 4.6 from pH 6.6. It is because more acid adds to the milk; it will decrease the pH of casein more, and less neutral casein will precipitate as most of the casein will precipitate and dissolve again. [1]
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From Graph 1, we can see that 5% acetic acid has the largest amount of casein precipitates, indicates that the pH value of casein is closest to 4.6. It is because addition acid adds to the milk, it will decrease the pH of casein, and neutral casein will precipitate. [1] [2]
10% acetic acid has lower amount of casein precipitates, indicates that the pH value of casein is not close to 4.6, too much acids are added and few of the casein precipitates dissolve. It is because more acid adds to the milk; it will decrease the pH of casein more, and less neutral casein will precipitate as few of casein will precipitate and dissolve again. [1] [2]
15% acetic acid has lower amount of casein precipitates, indicates that the pH value of casein is faraway to 4.6, too much acids are added and some of the casein precipitates dissolve. It is because more acid adds to the milk; it will decrease the pH of casein more, and less neutral casein will precipitate as more casein will precipitate and dissolve again. [1]

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