TNE1991
Summary : Principles of the pulper / finisher separating plant waste from tomato juice. Main
machines used (Bertocchi, FBR, Ing.A.Rossi, Rossi & Catelli, Sasib, Metro Int., US
constructors), and innovative trends (superior thickness, controlled atmosphere).
Theme(s): Industrial technology (equipment, packaging); Firms (industrial equipment).
Date : Oct 2000
Industrial equipment: Pulper / Finisher
Adapted from Carlo Sassi's (Metro International) presentation at the 4 th Processing Tomato
Congress in Sacramento June 2000
In a processing line for tomato paste (or juice) production, juice extraction is the section where
seeds, peels and stems are separated from the juice, which is then conveyed to other sections
of the processing line.
The present report intends to briefly describe the historical evolution of juice extractors, paying
particular attention to the machines currently utilized by main Italian Constructors and to the
innovative trends recently introduced.
Physical principles
Juice is obtained by applying force to the mass of fruit, suitable to push the juice through a
screen, which retains the waste (seeds, peels, stems). This force is obtained either by
producing an appropriate pressure on the inlet side (screw press) or by using a centrifugal force
effect.
Most machines now on the market use this centrifugal force system, while the other system is
limited to drinkable juice extraction and to hand-powered machines.
The use of centrifugal force, combined with an adequate mechanical action, permits an increase
of the pulp present in the juice.
This effect improves the consistency of the juice and the product thus obtained.
(Figure 01 - Screw press)
Machines utilized
A brief outline of the technology currently in competition on the market is opportune in order to
present a complete account of the sector.
Traditional machines, used until the beginning of the seventies, were composed of 3 parts :
• pulper
• finisher
• super-finisher
Rotors were composed of 3 or 4 blades with axial development and a slight helicoïdal
deformation, mostly designed for discharging waste. This unit was enclosed in a cylindrical or
truncated-conical screen. These machines remain on the market for small capacity needs.
The Alberto Bertuzzi Company continues to make lines according to the traditional technique;
Bertuzzi has improved his machines with updated devices such as those that exclude air from
the processing zone by injecting inert gas.
Due to the high capacities of modern processing plants, they almost all function with the widely
available “Turbo” extractors. These are characterized by rotors with a large number of blades,
(up to 24 or more) and by high rotation speeds (2.000 rpm. or more). The screens used for juice
extraction still have a cylindrical or truncated-conical shape.
Extraction can be carried out by single-unit machines or by two units in sequence (pulperfinisher) : the second solution is preferable when raw material is not always of the best quality,
as more care is required in order to eliminate impurities from the juice.
Generally, extraction can be adjusted in two ways :
- by controlling the distance between the blades-tips and the screen : reducing the distance
generally produces a higher yield from the extractor.
- by controlling the speed of the rotor : increased speed produces a stronger centrifugal force,
causing a more effective extraction of juice and pulp.
Sometimes the two systems are combined in order to obtain a more flexible machine. In the
case of tomato processing, it is preferable to adjust the speed of rotation by reducing the
distance between blades and screen : reducing the gap prevents seeds and stems from building
up between blades and screen and reduces the wear on the machine as well as any possible
subsequent juice pollution.
Main Machines currently in use
BERTOCCHI
The HX extractor functions mainly as a single-stage unit. It is widely available in North America
and has proved to be particularly suitable for tomato processing in California.
Protected by an international patent, the HX extractor is characterized by the exclusive design
of its pitted or indented blades.
This design increases the amount of product centrifugally forced through the screen, improving
the efficiency of extraction, which can be controlled, thanks to the conical screen axial transfer,
by varying the distance between rotor and screen.
A speed variator can even be introduced, as it can on all the machines on the market today. An
HX evolution kit is available to improve capacity for cold break processing.
F.B.R
Available in double and single stage versions, the F.B.R. “VORTEX” extractor has been
developed in recent years to match the high capacity needs of modern installations. Distance
control between rotor blades and screen is obtained by conical rotor axial transfer inside a
conical screen.
Great care has been taken to develop a C.I.P. periodical cleaning system for the screen,
allowing the extractor's performance to be sustained over long periods without necessitating
screen disassembly for maintenance. A wide range of models is available to cover all the
market needs.
For greater capacities (over 50 tons/hr) there now exists a new single body extractor “JUMBO
VORTEX” P.60L.
ING. A. ROSSI
The company produces machines that range from 5 to 100 tons/hr.
This extractor is available in single- and double-stage versions. Extraction yield control is
carried out by varying the distance between rotor and conical screen, without having to stop the
machine. Speed control can be included on request.
A C.I.P. cleaning system (optionally automatic) uses a temporized inlet of water and steam.
This Company markets a new double-unit line - pulper and finisher - with a variable
configuration :
- sequential installation (pulper-finisher) with a capacity up to 55 short tons/hr (Cold Break).
- parallel installation with a capacity up to 100 short tons/hr for each machine (Hot Break).
The configuration can easily be changed and the machine is suitable for a variety of operating
conditions and for different types of product.
The conical screen can be removed whilst leaving the rotor in place.
ROSSI & CATELLI
Available in single and double stage versions (pulper-finisher), the “BUTTERFLY” extractor is
one of the most famous and widely used turbo extractors.
It is characterized by a set of fixed-blade rotors made of special steel that guarantees an
excellent effect on the product and, at the same time, an optimum resistance to wear. Extraction
yield control is carried out by varying the rotation speed.
This machine has been updated over the years with improvements derived from the
constructor’s experience : all routine maintenance (such as screen replacement) can be done
easily and quickly, the rotor configuration (number of blades) can be changed according to
working requirements, the C.I.P. washing system is efficient and guarantees long endurance.
ROSSI & CATELLI
SASIB
The “TE” extractor has recently been updated and is available either as a single-stage machine
or as a double stage unit (pulper-finisher).
The horizontal axis of the machine is equipped with a rotor and a screen of truncated-conical
shape.
The screen can now be replaced without disassembling the rotor.
Extraction yield control is carried out by rotor axial transfer (without needing to stop the
machine) or by varying the number of rotor blades. It is possible to vary the rotation speed
according to special requirements.
This machine is very famous among users, as it has been present on the market for many years
and is known to be reliable.
U.S. CONSTRUCTORS
Two U.S. tomato extractor suppliers have been included in this list.
• LANGSENKAMP
Traditional updated conical separators are available. All of them have variable speed
adjustments, a wide range of flow rates and the option of maintenance without disassembly.
• BROWN
International Corporation
Single stage and double stage traditional cylindrical extractors are available (paddle separators)
with capacities up to 45 tons per hour.
Velocity, angle, clearance and type of screen can be adjusted according to intended use.
For particular uses, Brown can propose the famous Screw Finisher (screw press).
METRO INTERNATIONAL
The double stage “Twin Jet” and simple stage “Mono Jet” machines have quite recently been
designed and possess some original peculiarities.
Their vertical axis configuration and double stage engineering combined with mono-block
design lead to some exclusive advantages:
- great compactness and minimal space needed;
- a single motor, for driving the 1st stage (pulper) as well as the 2nd stage (finisher);
- minimal power needs;
- 1st stage (pulper) control by speed variation ;
- 2nd stage (finisher) control by axis transfer of the truncated-conical screen ;
The technical innovations of the extractor are protected by US and European patents.
Innovative trends
The most important innovative trends concern topics that have already become part of the
machines or are still at the experimental stage, in particular :
-
-
-
high thickness screens - where the screen's thickness is considerably larger than the
diameter of the holes. This can be achieved by changing from punching to tool
perforation, thus considerably extending the screen's life. It also ensures a greater
reliability of the machine.
high capacities - in response to the needs of modern processor, extractors available on
the market increasingly conform to the expanded capacity of most processing lines.
Reduced wear on rotor blades - the blade edges have been hardened. Some
constructors have also assembled blades with sintered hard metal in the external part
closest to the screen, minimizing wear and maintenance for the duration of the machine.
controlled atmosphere - it is now possible to extract juice in a controlled atmosphere
avoiding contact with oxygen in the air. The solutions proposed by constructors differ
technically.
(Sources : Carlo Sassi, Metro Int. June 2000, Sacramento)