Flow behaviour and viscosity of reconstituted skimmed milk treated with pulsed electric field

Flow behaviour and viscosity are important functional properties of food proteins and provide physical stability to emulsions and other suspended particles. They also contribute to the mouthfeel and the overall quality of foods. This study dealt with the effects of pulsed electric fields (PEF) on the flow behaviour and viscosity of reconstituted skimmed milk. Reconstituted skimmed milk was subjected to electric field intensities of 15, 18 and 20 kV cm−1 and numbers of pulses of 20, 40 or 60. The steady-state and peak hold tests of the reconstituted and PEF-treated skimmed milk were then investigated as well as the flow behaviour and viscosity using controlled stress rheometer. The rheological properties were also measured, at shear rates of 0–200 s−1 and 200–0 s−1. The shear rate and the shear stress data were described using the Herschel–Bulkley model. The reconstituted skimmed milk showed a shear-thinning behaviour and its apparent viscosity increased with increasing electric field intensity and increasing numbers of pulses. The values increased from 2.12 to 4.25 (10−3 Pa s) for the control and PEF-treated samples respectively. The consistency index (K) also increased with increasing electric field intensity and number of pulses. The K value increased from 1.42 to 1.54 (10−3 Pa sn) for the control and treated samples (20 kV cm−1 and 60 pulses) respectively. These results indicated that the PEF treatment changed the rheological properties of the reconstituted skimmed milk.