Intact Protein and Hydrolyzate

Intact protein and base hydrozylate have different color reactions when subjected into various tests. The protein used is Casein which was isolated from milk. Color reactions ,in these test, gives off the information about the composition of a protein. Results often varies from being positive to one and negative to another since one has its peptide bond intact while the other is broken. The different tests that are used in this experiment are : biuret test, Sakaguchi test, ninhydrin test, xanthoproteic test, and Hopkins – Cole test.

Casein is one of the proteins found in milk belonging to a group called phosphoproteins. It is commonly used as a binding agent in foods. It can easily separated from milk through the introduction of acetic acid. Biuret test is a color reaction test used in determining the presence of peptide bonds in the protein. The resulting color, if the test resulted positive, is violet or purple. Sakaguchi test is another color reaction test used in testing certain amino acids or proteins. This test specifically aims to detect the presence of arginine. The positive result for this test yields a reddish wine color or reddish-orange color. Ninhydrin test is a test that is used to detect or determine the presence of free alpha amino group. Ninhydrin targets the free amino acid group and free carboxylic acid group that produces a color reaction of blue-violet solution. Xanthoproteic test is a color reaction test that is used to detect if the following protein contains aromatic rings. The positive result for this test often results into a yellow color. Hopkins-Cole test is another test that is used to determine if a protein contains the amino acid, tryptophan. The positive result will produce a color of violet or purple.