The chemical solution that can be used to test for presence of protein in food substance is?
Xanthoprotic test
Why does the color of iodine solution turn blue when starch is added to it?
I hope this will help :What properties of starch (given its chemical structure) allow it to be used as an indicator? Davender Khera, Yale UniversityWhen starch is mixed with iodine in water, an intensely colored starch/iodine complex is formed. Many of the details of the reaction are still unknown. But it seems that the iodine (in the form of I5- ions) gets stuck in the coils of beta amylose molecules (beta amylose is a soluble starch). The starch forces the iodine atoms into a linear arrangement in the central groove of the amylose coil. There is some transfer of charge between the starch and the iodine. That changes the way electrons are confined, and so, changes spacing of the energy levels. The iodine/starch complex has energy level spacings that are just so for absorbing visible light- giving the complex its intense blue color.The complex is very useful for indicating redox titrations that involve iodine because the color change is very sharp. It can also be used as a general redox indicator: when there is excess oxidizing agent, the complex is blue; when there is excess reducing agent, the I5- breaks up into iodine and iodide and the color disappears.BTW...there is something known as GOOGLE. Next time you have such kind of doubts, please feel free to use it
Why does biurets reagent react with the presence of protein but not amino acids?
This reagent reacts specifically to peptide bonds which are present in proteins. Amino acids are chained together by peptide bonds to make proteins. An isolated amino acid simply will not react, as it is only a building block of a potential protein given the right circumstances (peptide bonds). ---> -C(=O)NH- An amino acid on it's own just doesn't have the right chemical structure to react with biurets reagent.