Biochirality originates from the chiral influences in the universe. The parity non-conservation of weak neutral current, which takes place through the exchange of neutral boson Z0 combined with the long range Coulomb interaction in atoms and molecules, produces a parity violating energy difference (PVED). In this note, the fact is to be indicated that there is a λ-type second order phase transition of D- and L-alanine (valine) at a certain critical temperature Tc. The PVED is to be calculated as 6×10-5eV/molecule by varieties of modern physical and chemical methods including the differential scanning calorimeter (DSC), SQUID, single crystal X-ray diffraction spectra,Iow-temperature 1H.MAS ssNMR, Raman spectra and ultrasonic measurement. A mechanism that differs from Salam's hypotheses is also discussed here.