Effect Of Pulsed Electric Fields On The Functional Properties And Structure Of Milk Proteins

Pulsed electric fields (PEF) are a new non-thermal food preservation method, which treats liquid or semi-solid food with high electric field intensities, very short electric pulse and very high pulse frequency. There are still lots of problems to solve for industrial application of PEF, for example, effects of PEF on food constituents and structures, product safety assurance after PEF processing etc. In this work we use PEF to process milk proteins to investigate the effect of PEF on the functional properties and structure of them, in order to provide some reference for the application of PEF on dairy industry.We studied the effect of PEF on casein: (1) After being treated by PEF, the pH, viscosity, emulsifying properties and foaming properties of casein didn't change significantly, while solubility increased.It might because PEF affected the structure of casein micelle while not to casein itself. (2) With the increment of the PEF strength or treatment time, the hydrophobicity of casein changed insignificantly, the content of molecule of higher weight and larger size increased a little, it may be the result of the dissociation and converge of casein micelle. SDS-PAGE and CD showed that PEF might had a tiny effect on the subunits and secondary structure of casein. (3) There was no significant change in in vitro digestibility of casein after being treated by PEF.We also studied the effect of PEF on whey-protein: (1) Its pH and viscosity had no significant change neither, but solubility, emulsifying properties and foaming properties increased, it might be the result of unfolding and relax of protein, and when the strength or treatment time got higher, the aggregation made a decrease of foaming properties.(2) The effect of PEF on the structure of whey-protein were also studied, it was basicly the same as casein, besides the content of its surface free sulfhydryls increased.