July 30, 1996 ISSUE #047
Screw presses are most commonly used to remove liquids from waste streams.Typical applications range from pressing citrus peel in the production of cattle feed to removing fiber from process wastewater at paper mills and plasticrecyclers.
An opposite class of applications are those where a valuable liquid can be extracted by the press. Fruit and berry juices were commonly produced with screw presses in the 1960's, although bag presses are now used in order to achieve maximum yield. Another large scale liquid extraction application of the past involves pressing alfalfa as part of the process of producing a poultry feed additive.
More recently Vincent presses have been found to be uniquely suitable for extracting special juices, flavors and essences. These applications include:
Steak sauces such as Worcestershire and Lea & Perrins are made from vinegar marinated garlic and onion, along with a variety of spices. The solids must be pressed from the marinated mass. The combination of wedgewire screens for fine filtration and the interrupted screw to prevent co- rotation made the Vincent press a winner in this application.
This spring a small CP-6 press was supplied to International Flavors and Fragrances. It was shipped to Mexico for use on broccoli, cauliflower, beans, and certain vegetable leaves. We can only guess at what it is they extract from the juices.
Earlier this month tests were performed for a Chinese joint venture of the French distiller, Charles Jacquin et Cia. Their need is to extract juice from the ginger root; this is clarified and used in the production of a fine liqueur. The trials were performed with both shredded and diced ginger root. A great deal of fiber was evident, so excellent results were achieved. The roots were pressed from 83% to only 62% moisture content with a double pass through the press.
In all of these applications the screw press is but one of several machines that are required. Shredding, grinding or macerating may be required ahead of the press. After pressing, the press liquor invariably requires clarification.This involves the use of static screens, decanters, centrifuges, diatomaceous earth (DE) filters and similar devices.