Sometimes screw presses are used to squeeze material destined for human consumption. Typically this is a fruit or berry juice, or nutraceuticals. For these applications our screw press construction is modified from the usual sludge, waste, and manure configurations.
Most Vincent presses are made with all liquid contact parts made of 304 grade stainless. This stainless steel is sandblasted before shipping the press. For food grade applications it is necessary to go further, to an alternate finish.
We refer to the alternate finish as Vincent Food Grade. For this case, after the first sandblasting, we fill, by welding, pits and undercuts which the sandblasting has made visible. These new welds are ground, and any weld splatter that has been missed is also ground off. Next the parts are blasted with glass bead. This gives a finish that has a slight luster, an improvement over sand blasting.
We passivate (swab down) the stainless with acid to remove carbon steel inclusions. These inclusions come from using chipping hammers, wire brushes and other carbon steel tools. Without passivating, rust streaks are apt to appear on the press.
During assembly, food grade grease is used in the cone bushings, shaft bearings, and seal housing. If requested, the gearbox can be filled with food grade grease; people do this where they absolutely do not permit any non-food grade lubricants in their facility.
An alternate finish just coming into play is electro-polishing. So far this is limited to our smaller presses.
Vincent does not offer the highly polished equipment used in creameries and factories handling milk products like ice cream, yogurt, and cheese.
Optional CIP accessories are offered with presses for food applications. These include both internal and external CIP. There is a recent newsletter describing these.
In all cases pasteurization is required for food materials from screw presses.