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November 5, 1999

Our knowledge of how our press performs in pineapple is very limited. We know of installations in Honduras, Brazil, Venezuela, the Philippines, and Japan where a Vincent screw press is used in making pineapple juice, but we have had almost no significant contact with any of them for many years. Many of the sales were made through the late Art Lund, a sales agent, and we have no data as to the actual operations. As recently as 1998 we supplied a VP-16 for use in a pineapple operation in Costa Rica.

Some notes indicate we should expect a 42% to 48% juice yield, and that the press should have the rotating cone option. Other notes show 50% yield and that the rotating cone is not necessary.

The process in Honduras involves first trimming the pineapple and then crushing it in a Vincent shredder. Next the crushed material is run through a Vincent screw press. We are not sure but we believe they add water to the press cake and then press it again. In any case, the press liquor is run through Brown or FMC finishers.

In Okinawa they have two presses. One VP-12 is fed the culls and odd pieces of pineapple for juicing. The second, a smaller VP-10 press, is used to press the pulp wash. It is likely that the press cake from the VP-12 is washed to diffuse the remaining sugars, and then re-pressed.

One press in Brazil has been in service for almost 30 years, and it is operating successfully to this day. Benedito Jorge, now a director of Citrosuco, has been involved with this press from the very start.

The Ginaca machine is used to core and skin the pineapple; the plug of fruit produced is sliced into the familiar canned fruit salad item. We have observed that the Ginaca works best on green fruit, and the skins and trims from such fruit are relatively slimy and do not press well. Consequently, when pressing trim from Ginaca machines it is common to de-rate the brochure capacity figures of our presses.

With FMC Italy's help we did a process chart in 1996 where 20 MT/HR of topped, skinned and cored pineapple are run through an FMC Paddle Finisher. Free running juice and the juice that can be easily separated are recovered.

The pulp (pomace) discharged from the Paddle Finisher is further squeezed in a Screw Finisher. The pomace discharged by this Finisher still contains juice. The moisture content is 78% to 80%.

Next the pomace is pressed, without the addition of water, in a Vincent screw press. Normally 8% of the juice recovery is obtained in this press.

There is a letter from the 1970's where we wrote that we had two 10" units, with non-rotating cones, running twelve years in Venezuela (24 hour day during a six month season). Whole mature fresh Spanish Reds, at 85% moisture, less tops, produced juice at 10º to 13º Brix. They used 3/32 perf screens, and reportedly the press met its 10,000 pph capacity rating and ran consistently with a 50/50 split between juice and cake, with some runs of 60% juice when at 13º Bx. The speed was increased from the normal 21 rpm up to 30 rpm, taking the motor from 5 hp up to 7-1/2 hp. The cone pressure was nominal, 40 psi.

Frequently we find that pineapple plants make use of old Jones screw presses. These are vertical machines, a dated version of the Vincent horizontal interrupted screw design.

Issue 99

Pineapple Beverage Juice

February 21, 2003

Pineapple juice is produced at canneries from pineapple meat that cannot be used for higher value products such as slices, chunks, tidbits, and crushed. The juice is concentrated from 12º natural Brix to as high as 60º in order to reduce shipping volume and tonnage. Typically Cook TASTE evaporators (vertical tube, falling film, multiple effect) are used for this purpose.

Last year Vincent ran screw press tests at a long established pineapple cannery. The principal sources of juice were (a) eradicator meat that is scraped off the skin in the Ginaca machines, (b) the core (central fibrous portion of the fruit), and (c) strip slices that are cut from the top and bottom of the plug of meat that is being sliced. These various juice components were all directed to a Rietz RD-18 Disintegrator.

To produce beverage juice, the shredded material is first pumped to a bank of three FMC finishers. The juice from the FMC's goes to four Brown finishers. The pulp from the FMC's and Brown's goes to a Jones screw press for a third pressing. The juice from these three sources is combined, filtered and concentrated.

Cake from the Jones press is directed to the area of the plant where mill (as opposed to beverage) juice is extracted. This cake is mixed with skin material and pressed one more time before the cake is sold as silage (animal feed).

Alternatively, pineapple juice can be produced from the whole pineapple. This month we visited five small plants in Costa Rica and Panama that do this. They start with a Brown International machine known as the Pine-O-Mat. The first step in its operation is to split the fruit in half, along the core. Then all of the juicy pulp is scraped from the inside of each half. The outer skins are directed from the Pine-O-Mat into a Vincent 12" or 16" screw press, while the pulp is pumped to a series of finishing machines or a centrifuge. Press liquor from the screw press goes to finishers and, maybe, an evaporator.

Operation of the Pine-O-Mat is interesting. It has two large drums, one with a grating surface and one with a feeder surface. While being scoured, the pineapple is pressed against a screen/grid plate. The pressure and preset gap of the grid plate can be adjusted for different diameters of pineapple. The idea is to scrape off the pulp and juice, down to the eyes. The eyes are pulled back to the skin as the pineapple half is compressed between the rolls. This allows the grate to operate at high juice yields, without adding the bitterness from the eyes into the juice.

The Pine-O-Mat juice yield is about 50% of the weight of topped pineapples and can go as high as 55% with over-ripe fruit. Combined canning and juice lines can yield up to 75% by weight of the pineapple.

Issue 136

Pineapple Mill Juice

November 8, 2002

Mill juice is the name used in Hawaiian pineapple processing to designate juice that is produced from pineapple skin. This juice is used to top off cans of pineapple slices and chunks.

In contrast, pineapple beverage juice is made from Ginaca strip slices, core, and eradicator meat. The beverage juice from these parts of the fruit typically has 12º Brix. Cake remaining after extraction of beverage juice is directed into the third stage press used in mill juice production.

The juice pressed from pineapple skins has a Brix of 8º to 10º Bx. The juice is produced by first shredding the ends (top and bottom) along with the lateral skin and cull fruit. A high-horsepower shredder, with a coarse screen, is used. Once shredded, the skin is first, second and third pressed. That is, the cake from the first pressing goes directly, without any water addition, to second pressing; and cake from second pressing goes directly to third pressing. The cake after third pressing, called silage, is sold as animal feed.

Recent testing with a Vincent Twin Screw press, Model TSP-12, provided the following data: Skin at the shredder (before pressing), 88% moisture; after first pressing, 80% moisture; after second pressing, 78% moisture; after third pressing (silage), 78% moisture. Brix of all press liquors, 9º.

Only screw presses of the interrupted flight design (Vincent, Jones, Rietz, and Schwarz) were used on the pineapple skin. The one Rietz press in service had the rotating cone feature; however, this appeared unnecessary as there was no channeling tendency and there was negligible press liquor coming through the cone screen. Cake discharge was uniform and non-channeling in all the presses.

Dramatic improvement in juice production was realized by steam injection. Steam was injected both at the inlet hoppers of the screw presses and where stationary resistor teeth protruded into the main screen portion of the presses. Press liquor temperature was held at about 130º F.

The juice from the presses is first filtered in a static screen. Then it is heated to 190º F for three minutes and screened in a second set of static screens. Then it is cooled and filtered in a Vincent Fiber Filter. The filtrate from this machine is sent to a Westfalia horizontal centrifuge, while the Fiber Filter sludge goes to a Westfalia decanter. Filtrate from both Westfalia's goes to ultrafiltration and deionization. Color and Ph are corrected in the deionizer.

Issue 133