Biophysical study on complex formation between β-Lactoglobulin and vitamin B12

•Binding interaction of β-Lactoglobulin with vitamin B12 was studied.•Vitamin B12 quenched the fluorescence of β-Lactoglobulin by static quenching.•The binding constant between β-Lactoglobulin and vitamin B12 is ~ 104 M−1.•Vitamin B12 alters the microenvironment of tryptophan residue of β-Lactoglobulin.•Secondary & tertiary structure of β-Lactoglobulin remain unaltered by vitamin B12.