Enhanced expression of juice from soft vegetable tissues by pulsed electric fields: consolidation stages analysis Original Research Article

The expression behaviour of different soft vegetable tissues is compared. The detailed analysis of different consolidation stages is done for potato tissue. The primary consolidation Terzaghi’s coefficient Cv is estimated as Cv≈(2.0±0.6)×10−2 cm2/s. The logarithmic type of secondary consolidation is observed and the dependency of the consolidation processes on the applied pressure is discussed. The four main time constants that characterize the consolidation curve are defined: t0 is the time of pre-consolidation stage, t1 is the time of intensive liquid expression during the primary consolidation stage, t2 is the time of transition to the secondary consolidation, and td is the expected ‘theoretical’ time of complete liquid expression. At a pressure of P=5 bar, t0≈10 s, t1≈103 s, t2≈104 s, and td≈6×104 s (17 h). Consolidation behaviour after application of pulsed electric fields (PEF) is studied. At low degrees of PEF treatments (electric field intensity E<300 V/cm, total time of PEF treatment TPEF<0.1 s), unchanged pressing behaviour at the primary consolidation stage (tt1, which is disadvantageous from industrial point of view. It is shown that PEF should be applied after a pre-consolidation stage. But the time at which PEF treatment starts tPEF has no significant effect on the juice yield for the case when t0