The present disclosure relates to a method for reducing the pulp content of fruit juices containing pulp, especially citrus juices. The fruit juice is continuously purified of the pulp phase in the centrifugal field of a separator and the pulp phase is discharged through a fluid discharge.
It is known to use separators in the production of citrus juices made of citrus fruits for clarifying a citrus juice containing pulp.
In the production of citrus juices, the citrus fruits are washed, sorted and supplied to juice-extraction machines, the so-called extractors. The juice running off the extractors has a high pulp content which is removed in further process steps. Finishers will remove the coarser fruit cells at first.
A hydrocyclone is optionally connected upstream of the separator in order to separate sand particles from the fruit juice. Separators will separate fine pulp in the next step separators. More or less pulp is removed depending on each production step.
In order to reduce the number of discharges of solid matter, which discharges are each accompanied by a certain loss of juice, it is known to guide the pulp phase from the solid chamber of the separator via a separating plate continuously to a peeling disk and to convey the same from there out of the machine. As a result of this operating mode of the separator, the number of discharges can be reduced considerably with the still present discontinuous solids discharge system. Solid particles will frequently accumulate over time on the plates during the clarification of juice. This layer of solids will reduce the efficiency of the clarification. It generally needs to be removed two to three times per hour by the discharge of the drum, for example, by opening the piston slide.
The free-flowing pulp phase, which is discharged via a separator plate, mostly comprises relatively soft, compressible solid matter. This concerns a separation of solids and fluids despite the given residual flowability of the pulp phase during the separation of this relatively viscous phase from the citrus juice.
After the clarification in the separator, further processing of the thus clarified citrus juice can occur, for example, concentration in evaporators in which the water content in the juice is reduced.
It is also known to control the separator in the clarification of the citrus juice by an optical turbidity device in the discharge of the clear-phase line in order to determine, for example, when an additional discharge of solid matter is necessary by the piston slide. A control of this kind, for securing a fully automatic operation, is not sufficient as a result of the consistency of the citrus fruit content and the rapidly changing properties of the product which is supplied to the machine.
The problem arises, especially after the start-up of the separator and after the discharge of solid matter, that clear juice will also flow through the peeling disk for the discharge of the pulp phase for a certain period of time, while pulp needs to accumulate again in the solids collecting chamber until it is discharged via the separator plate again.
It is known for solving this problem to seal the peeling disk for the discharge of the pulp phase by closing a valve downstream of this peeling disk and by opening the valve only when sufficient pulp has accumulated in the solids collecting chamber.
It is disadvantageous, in this procedure, that it requires a manual intervention during the start-up of the separator and after discharges of the solid matter with the help of the piston slide. It is not possible to perform any automatic control by way of the optical turbidity device because the measurement in the clear phase is not meaningful enough in this respect.
In view of the background as explained above, to the present disclosures provides for a method to further optimize the method that is disclosed above. In particular, regarding the necessary manual interventions during the start-up of the separator and after discharges of the solid matter, the method according to the present disclosure avoids such manual interventions.
The present disclosure thus relates to a method for influencing the pulp content of a fruit or citrus juice. The method steps include: continuously purifying the juice of a pulp phase in a centrifugal field of a separator, the pulp being discharged from a drum of the separator through a pulp discharge line; measuring a density of the discharged pulp phase by a density flow-through measuring device; and, controlling a controllable device in accordance with a density measurement by the density flow-through measuring device thereby influencing the density of the pulp phase.
Additional features of the present disclosure are discussed below.
Accordingly, a density flow-through measuring system is installed in the pulp discharge line from the separator drum, which measuring system controls a controllable element depending on the density measured.
The method, according to the present disclosure, is especially suitable for fruit juices which are of such a nature that it is possible to discharge the solids-like, but still sufficiently flowable, pulp phase by fluid discharge from the separator drum. The method according to the present disclosure is thus especially suitable for citrus fruits. In addition, the method according to the present disclosure can also be used for the reduction of the pulp content of other fruits which have such a consistency that its pulp can be guided through a fluid discharge especially by a peeling disk out of the separator drum.
According to an embodiment of the present disclosure, the pulp phase is recirculated entirely or partly via a recirculation line to the feed line of the separator in the case of an inadequate content of solid matter, for example, when the density limit is not reached. The problem of product losses after the start-up of the machine and after discharges of solid matter with a further discontinuously working solids discharge system is thus solved in a simple way. That is because after the start-up and after the discharging, the phase flowing off via the separator plate, which is mostly clear juice at first, is guided back to the feed line after a density measurement until a sufficient amount of pulp has accumulated in the solids collection chamber after a certain period of time, so that the pulp starts to flow over the separator plate. The density measurement is repeated after a predetermined period of time in order to determine whether the density of the pulp is high enough in the meantime in order to stop the recirculation of the pulp to the feed line of the separator. This is followed by a changeover and the pulp guided out of the separator is guided to a pulp tank.
The start-up of the separator and the further operation after the discharge of solid matter can thus be automated in a simple manner by a simple control method, according to the present disclosure.
The following parameter ranges may be applied in orange juice in a separator of type GSE 200 supplied, for example, by GEA Westfalia Separator GMBH, which separator, is equipped with a continuous “depulping apparatus” having the following characteristics:
Feed capacity of juice: 15,000 to 25,000 L/h; or, for example, 18,000 to 22,000 L/h;
Content of solid matter in the incoming juice: 10 to 14% by volume; or, for example, 10 to 12% by volume;
Content of solid matter in the discharged juice: 0.5 to 2.0% by volume; or, for example, 0.5 to 1% by volume;
Target concentration of solid matter in the pulp flow: 80 to 95% by volume;
Actual concentration of solid matter in the pulp flow during start-up: 10 to 28% by volume, whereby juice concentration in the feed may be doubled; and
Switching point of control unit: 60 to 80% by volume; or, for example, 75 to 80% by volume.
The following parameters are advantageous and may be obtained in the processing of lemon juice:
Feed capacity of juice: 12,000 to 25,000 L/h; or, for example, 15,000 to 18,000 L/h;
Content of solid matter in the incoming juice: 8 to 12% by volume; or, for example, 8 to 10% by volume;
Content of solid matter in the discharged juice: 0.5 to 2.0% by volume; or, for example, 0.5 to 1% by volume;
Target concentration of solid matter in the pulp flow: 80 to 95% by volume;
Actual concentration of solid matter in the pulp flow during start-up: 16 to 24% by volume, whereby juice concentration in the feed may be doubled; and
Switching point of control unit: 60 to 80% by volume; or, for example, 75 to 80% by volume.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.