Pulsed electric field treatment of reconstituted skim milks at alkaline pH or with added EDTA

Pulsed electric field (PEF) treatment at 49 kV/cm for 19.36 μs (up to 70 °C) was performed on reconstituted skim milk (10 wt%). The milk condition was varied either by pH adjustment (pH 6.7-8.0) or by the addition of ethylenediaminetetraacetic acid (EDTA) (up to 30 mM). Except for milks at pH ≥ 7.5, PEF treatment did not affect size and ξ-potential of the milk particles, the amounts of protein in the serum or the state of the whey proteins. For milks at pH ≥ 7.5, a decrease in the size of the milk particles and an increase in the amount of proteins in the serum were measured. Sodium dodecyl sulphate - polyacrylamide gel electrophoresis (SDS-PAGE) measurements showed that the amount of caseins in the serum increased, while the whey proteins were not affected. This indicates that the decrease of the size of the milk proteins is due to the dissociation of the casein micelles. Further, this study demonstrates that the PEF effects on milks at pH ≥ 7.5 is due to ohmic heating during the PEF treatment.