Both cows milk and water-buffalo's milk produce a violet colour when tested with biuret solution because they both contain protein.
Alkaline levels are essential for the solution to change colour. Without alkaline levels, the colour of the solution would not be detectable.
Copper sulphate gives biuret reagent it's blue colour.
Blue!!
The reagent used in the Biuret Test is a solution of copper sulfate (CuSO4) and potassium hydroxide (KOH). The KOH is there to raise the pH of the solution to alkaline levels; the crucial component is the copper (II) ion from the CuSO4. When peptide bonds are present in this alkaline solution, the copper (II) ions will form a coordination complex with four nitrogen atoms involved in peptide bonds. Copper Sulfate solution is a blue colour, but when the copper (II) ions are coordinated with the nitrogen atoms of these peptide bonds, the colour of the solution changes from blue to violet. This colour change is dependent on the number of peptide bonds in the solution, so the more protein, the more intense the change. When the peptides are very short, the solution turns a pink colour, rather than violet.
non
To test starch: To test starch you take the food sample, and add iodine solution if the colour turns black this means starch is present. To test for protein: To test for protein, you take the food sample and add Biuret A and Biuret B and shake, if the colour turns lilac this means that protein is present.
The biuret test tests for peptide (protein) bonds. In a test with a protein containing substance, a Copper(II) ion is reduced to Copper(I) which forms a compound with the nitrogen and carbon atoms of the peptide (protein) bonds in an alkaline (pH above 7) solution. If the solution goes to a purply-violet colour, proteins have been detected.
Most likely copper.
If Biuret Reagent is related to the presence of Protein macromolecules, then a positive result will change it's colour from blue to violet.
no! no change in colour confirms presence of cysteine
purple for longer peptides (larger proteins) and pink for shorter ones
To mix the reactants. Assuming you have been doing a titration experiment and I am doing your homework its so as you add the acid/alkali you can accuratly close the biuret when the indicator changes colour.