Pulsed Electric Field Treatment of Raw Milk and Its Effect on Protein-Free Amino Acids Transition

As a nonthermal microbial inactivation technology, pulsed electric field (PEF) treatment technology shows potentials in liquid food sterilization and other biological applications. The purpose of this study is to investigate the effect of PEF treatment on sterilization, the physical and the chemical properties of raw milk. Fresh raw milk samples were subject to PEF process with electric field strength ranged from 15 to 35 kV/cm for 1.25–5 ms in this study. The sterile rate and the shelf-life were evaluated and compared for PEF-treated, pasteurized, and untreated raw milk samples. It was demonstrated that similar inactivation effect was achieved as compared with pasteurization when raw milk was PEF-treated for 5 ms using 35-kV/cm field strength. The concentration of protein and free amino acids (FAA) was also measured and the results indicated that the PEF process promoted the protein-FAA transition as the concentration of FAA in the raw milk sample increased by as much as 14%. It is also shown that the input energy density of PEF treatment can be the deciding factor which affects both inactivation of microorganisms and the transformation of composition in the liquid food.