Free Run Grape Juice

November 17, 2003

There is an interesting application for the Series KP screw presses in the grape juice and wine industry. This involves improving the yield of free run juice at a minimum capital cost.

Successful testing was conducted over a harvest season. Three model KP-16 presses were utilized to increase the proportion of free run juice while at the same time increasing the throughput capacity of downstream presses.

The normal flow was to process the grapes through destemmers, followed by crushers. Free run juice from this mass was removed in rotary drum screens. The remaining solids, called "must", were pressed for maximum yield in traditional Le Coq and Diemme screw presses.

The quality of the juice from the high yield presses is lower than that of free run juice. This is because of impurities that are pressed into the juice in presses designed and operated for maximum yield.

Installing the "soft squeeze" KP presses after the rotary screens allowed additional yield of free run juice. At the same time, the physical volume of must was reduced. This in turn increased the capacity of the Le Coq and Diemme presses.

One innovation was to use the cake discharge cone as an adjustable fixed orifice device, rather than the normal floating constant pressure door. This was achieved by replacing the air pressure regulator controls on the discharge air cylinder with a linear positioner. With this the operator was able to set (and vary) a discharge opening that resulted in the best yield without over-pressing the must.

Since this testing was performed, the larger capacity Models KP-24 and KP-30 have been introduced. It is expected, should industry conditions improve, that the large scale presses will find application in large volume grape juicing.

Issue 145