Alanine does not show Biuret test because
Biuret test is used for deduction of peptide
linkage & alanine is amino acid.
Albumine is protein so have paptide linkage
so it gives positive Biuret test.
Positive Barfoed test is shown by
monosaccharide but not disaccharide. Positive
Molisch's test is shown by glucose.