Enhancement of juice recovery from carrot using 2-stage pressing with ohmic heating

Experiments were conducted to study the enhancement of carrot juice recovery using 2-stage pressing with ohmic heating. the study was designed using response surface methodology employing the box-behnken design. the independent variables were: duration of first pressing (1,2,3 min.),voltage gradient (15,20,25 v/cm) and final temperature (60,70,80oc). control experiments,without any ohmic heating between the 2-stage pressing,were also conducted for the purpose of comparison. total juice recovery and juice quality were the dependent variables. mathematical analysis for multistage pressing was applied to 2-stage expression process. the total juice recovery increased with increase in the duration of 1st pressing. maximum enhancement in juice recovery in 2-stage expression with ohmic heating over control was 13.76%. the total solids ranged between 7.55 to 11.12% and increased with increase in the duration of 1st pressing. total soluble solids were in the range of 3.6 to 6.6obrix and increased at lower voltage gradient and higher final temperature. the ohmic heating did not cause much change in the colour of juice. the study indicated that maximum juice recovery of 98.9% can be obtained with 1st pressing of 2.72 min.,ohmic heating up to a final temperature of 65.6oc under a voltage gradient of 15 v/cm followed by 2nd pressing of 10 min. © school of engineering,taylors university.