Extraction of Coconut Milk by Continuous Screw Press

Abstract

Studies were conducted on the extraction of coconut milk using a continuous screw press. Speeds of 8.5, 12.5, and 17.5 r/min were used on the pressing screw. Pressures of 60, 80, 100, 120, 140, 160 and 180 lbf/in² were used on the creeping cone, which in this machine serves as a solids releasing valve. A hydraulic press was used to evaluate the screw-press cake by completely removing the remaining coconut milk from the pressed solid material under a direct pressure of 185 p.s.i./m² for 1 minute. The results of the experiments indicate a gradual increase in efficiency in the coconut milk extraction process as the pressure is augmented from 60 to 180 lbf/in², with a more pronounced effect within the range of 60 to 100 lbf/in². The increase in efficiency ranged from 3.5 percent at 8.5 r/min to 6.5 percent at 7.5 r/min. Capacity in the performance of the press is the characteristic most affected by changes in speed of the pressing screw. The capacity at a speed of 17.5 r/min dropped from 3,160 to 2,720 lbs/hr. With a speed of 12.5 r/min the capacity fluctuated between 1,800 and 1,700 lbs/hr, and at 8.5 r/min it was about 1,300 lbs/hr. The recommended set of conditions to extract coconut milk using this type of continuous screw-press are a speed of 17.5 r/min and a pressure of 100 lbs on the creeping cone, when working with comminute material from a hammer mill with a No. 4 screen (10 1/4-in perforations/in²).