WO1991005847A1

WO1991005847A1 - Process for clarifying raw juice and installation for implementing it

Info

Publication number: WO1991005847A1
Application number: PCT/CH1990/000243
Authority: WO
Inventors: Walter Gresch
Original assignee: Bucher-Guyer Ag Maschinenfabrik
Priority date: 1989-10-20
Filing date: 1990-10-16
Publication date: 1991-05-02
Also published as: HU907458D0; HUT57017A; CZ509490A3

Abstract

The process for clarifying raw juices of fruit, grapes, berries and other fruits and vegetables or wine and beer is implemented by a combination of continuous pre-fining (1) and a continuously oprating single-stage transverse current filtering installation (3). The transverse current filtering installation (3) is operated with a relatively high solid content in the retentate circuit (8) or with a high concentration factor. This considerably improves the efficiency of the installation and provides concomitant savings in capital and operating costs.

Description

Process for clarifying raw juice and plant for carrying out the process.

The invention relates to a method and a system for clarifying raw juice from fruit, grapes, berries or other fruits and vegetables or wine and beer by means of pre-washing and cross-flow filtration.

With the pre-finishing of juices by adding fining agents, all substances causing cloudiness should be removed so far that night cloudiness no longer occurs at a later point in time. In addition, the pretreatment is intended to improve the sensory properties of the juice and possibly also lighten the color. Furthermore, the performance of cross-flow filtration is to be significantly improved.

Methods have already become known which work with continuous pre-finishing and semi-discontinuous, 1-stage cross-flow filtration, a batch tank being arranged between pre-finishing and cross-flow filtration. With these versions, the turbidity remains in the system until the system is cleaned. As a result, the product quality, in particular the stability with regard to subsequent clouding, can be impaired. Due to the semi-discontinuous system, the dwell time of the raw juice in the system is not particularly short. This can cause damage to sensitive products when driving in higher temperature ranges (e.g. 55 C).

Furthermore, a method is known with a continuous pretreatment and a semi-continuous as well as continuous 1-stage cross-flow filtration. In this embodiment, a filter press is provided in the retentate circuit of the cross-flow filtration system with which the turbidity is removed from the cross-flow filtration system. The filtrate from the filter press is fed into a buffer tank of the crossflow filtration system or. returned to the feed line of the crossflow filtration. Due to the use of a filter press for permanent trub separation from the retentate circuit of the cross-flow filtration system, the operating mode semi-continuously or 1-stage-continuously has a significantly smaller influence on the behavior of the cross-flow filtration system, especially the service life until cleaning. The cross flow filtration system works with capillary modules respectively. Thin channel modules. The known plant is intended for the clarification of wine.

A disadvantage of this known embodiment is that the outlay for the slurry removal device is very high. In the case of semi-continuous systems, further investment costs arise through the use of a buffer or batch tank, which also greatly increases the effort for a fully automatic system. In addition, the flux, that is to say the throughput of the cross-flow filtration system, remains relatively low, which increases the cost of operating the system. The thin-channel capillary modules of the cross-flow filtration system do not allow a high concentration factor.

In 1-stage operation without separation of sludge from the retort circuit of the crossflow filtration system, the flux, ie the filter performance per unit filter area, is very low with the required concentration factor or the required yield. For this reason, continuous systems are generally built in several stages, the concentration factor in the first Level is relatively low. Such systems are only worthwhile from a certain size.

The invention is based on the object of avoiding the disadvantages mentioned and of creating a method of the type mentioned at the outset which increases the profitability of the system, facilitates the automation of the process sequence and improves the product quality.

According to the invention, this object is achieved by the indirect or direct combination of at least partially continuous pretreatment with a least 1-stage, continuous cross-flow filtration system, which with a relatively high solids content in the retentate or. a high concentration factor is operated.

Further features, refinements and developments of the invention can be found in the patent claims.

The invention is explained in more detail in the following description and the drawing, which represents several exemplary embodiments. Show it

Fig. 1 is a schematic representation of the system according to the invention and

2 an embodiment with gelatin /

Bentonite pretreatment and diafiltration.

In the exemplary embodiment according to FIG. 1, the system for carrying out the method according to the invention consists of a continuously working pretreatment 1 which is connected via a line 2 to a downstream, preferably working, preferably 1-stage crossflow filter. trationsanlage 3 is operationally related. The pretreatment 1 is fed via a line 4 to the raw juice to be clarified and via lines 5, 6, 7 various fining agents. Compared to normal fining, only about 10 - 60% of the full fining agent requirement is used for pre-finishing. The line 2 of the pretreatment 1 opens into the retentate circuit 8 of the crossflow filtration system 3. A circulating pump 9 arranged in the retentate circuit 8 conveys the raw juice via the membrane 10 of the crossflow filtration system 3. The clarified juice is discharged as a permeate via a line 11.

The cross-flow filtration system 3 is equipped with large-channel modules which have a channel gap width or, in the case of tubular modules, a channel diameter of at least 4 mm. This results in a relatively high proportion of solids. a high concentration factor in the retentate circuit 8 of the crossflow filtration system 3. The wet turbidity content of the retentate stream is at least 40% and the concentration factor based on apple juice from the horizontal basket press is at least 20%. For cross-flow filtration, there is also an additional trub load which is the Schönunsgtrub.

To the concentration factor resp. To keep the trubate content in the retentate stream approximately constant, part of the retentate is discharged from the retentate circuit 8 through a line 12.

Experiments in connection with the pretreatment have shown that from a sufficiently high turbidity content, for example at a concentration factor of 30-40, the flux generally increases very strongly with an increasing concentration factor. The flux increase in apple juice is generally over 75% of the average value of conventionally operated plants. To the crossflow filtration In order to run at maximum power, the turbidity content is kept constant at such a high value that the system can still be operated without the risk of blockages in the modules. The flux increase achieved makes it possible to achieve considerable savings in investment and operating costs and, at the same time, improve turbidity stability due to the pretreatment.

Due to the continuous operation of the cross-flow filtration system, the use of a batch tank is no longer necessary. This results in a relatively simple structure of the plant and, above all, the prerequisite for cost-effective automation of the process sequence. Further advantages due to the relatively high concentration factor and the 1-stage, continuous operation are that the dwell time of the raw juice is short and a special sediment removal, for example by means of special filter presses and the like, is not necessary or. is not desired. In 1-stage continuous operation, the turbidity is subject to a relatively short residence time in the crossflow filtration system, so that there is no disturbing damage to the end product due to the high proportion of turbidity in the retentate. The investment costs can thus be kept relatively low and the system is easier to operate.

In order for the cross-flow system to run constantly in continuous operation despite the high concentration factor, a time-constant input product to the cross-flow system is required. Such is best guaranteed by at least partially continuous pre-finishing.

The cross-flow filtration system 3 is operated warm at a temperature of at least 30 ° C. This measure also contributes to a significant increase in flux. The continuous pretreatment can also be carried out, for example, using the known flotation process. The raw juice in the pretreatment 1 is mixed with various fining agents, which are supplied via the lines 5, 6, 7 in metered, controllable amounts. After the flocculation has ended, the flocked-out fining slurry is continuously discharged from the pre-fining 1 through line 13. In this case, care must be taken to ensure that the concentration factor in the subsequent cross-flow filtration system 3 is increased rapidly in order to prevent pore blockages or. to avoid irreversible flux reduction. This can be accomplished in a simple manner in that, for example, during the start-up period, no or very little retentate is discharged through line 12 from the retentate circuit 8 of the crossflow filtration system 3. This measure is very advantageous in the case of a relatively high amount of fining.

The combined method according to the invention has the advantage over clarification, which is carried out exclusively by flotation, that fewer fining agents are required with a better brilliance of the clear juice. In addition, the flotation system can be dimensioned much smaller in this case, since it is only pretreated.

In addition to a continuous gelatin / bentonite pre-screening, the system according to the invention or the pre-screening 1 can also be preceded by a continuous depectinization 14 or a centrifuge 15 (FIG. 1). If pre-centrifugation is carried out before the pretreatment, the trub ejection produced by the centrifuge 15 can be introduced via a line 16 into the retentate circuit 8 of the continuously operating crossflow filtration system 3 to improve the overall yield. As can be seen from FIG. 1, an aroma recovery system 17 can be connected upstream of the continuous pretreatment 1.

In very difficult cases, the centrifuge 15 or other turbid separation devices can also be used between pre-treatment 1 and crossflow filtration system 3. In this case, it is advantageous to also arrange the aroma recovery system 17 between pretreatment 1 and crossflow filtration system 3.

In the exemplary embodiment according to FIG. 2, the raw juice is fed in a continuous process via a line 18 and a feed pump 19 to a continuous gelatin / bentonite pretreatment 20 which consists of a plurality of retention tanks 21 arranged one after the other. The raw juice is first mixed and treated via a line 22 with a first fining agent, preferably gelatin, and after a certain dwell time in the first dwell tank or tanks 20 via a line 23 with a second fining agent, preferably bentonite. After the last fining agent has been added, the raw juice remains in the last one or more retention tanks 21 for a certain time and is then fed via a line 24 to the retentate circuit 8 of the continuously operating cross-flow filtration system 3.

To improve the yield, it is expedient to collect the retentate discharged via the line 12 from the retentate circuit 8 of the cross-flow filtration system 3 with the aid of a metering pump 25 in a retentate collecting tank 26 and from time to time, together with the cross-flow filtration, diafiltration perform. For this purpose, water is constantly fed to the retentate collecting tank 26 via a line 27 for diluting the retentate. In the simple diafiltration, 1 part by volume of Reten¬ tat is continuously mixed with 1 part by volume of water and in the double diafiltration 2 parts by volume of retentate is mixed with 2 parts by volume of water. The mixture of retentate and water is continuously fed back into the retentate circuit 8 of the crossflow filtration system 3 via a line 28 and a pump 29. A line 30 is provided for the disposal of the retentate collecting tank 26.

During the diafiltration, the supply of the pre-treated raw juice to the crossflow filtration system 3 is preferably throttled or interrupted. Because of this measure, yields of over 99% are achieved despite only 1-stage continuous crossflow filtration. This is due to the fact that, owing to the high flux of crossflow filtration, multiple times, instead of just diafiltration, are possible within a short time.

In order to regulate the amounts of fining agents required for the pretreatment, the permeate amount is measured with the aid of a quantity measuring device 31 (FIG. 2) via a control line 32, the measurement data are passed to a control and regulating device 33, which with the respective Dosierpum¬ pe 34 is connected for the fining agent in question and regulates the supply amount depending on the permeate output. The same regulation is also envisaged for the rejection of retentions. For this purpose, the quantity measuring device 31 for the permeate is connected via a control line 35 to a control and regulating device 36 which controls the metering pump 25 for the retentate to be discharged and regulates the amount of retentate. In addition, other known methods can be used to determine the concentration factor or to keep the turbidity in the retentate cycle constant. To regulate the amount of raw juice that is supplied to the system according to the invention, a control valve 37 is provided between the feed pump 19 and the pretreatment 20 (FIG. 2). The control valve 37 is connected via a control line 38 to a pressure regulator 39, which is arranged upstream of the circulation pump 9 of the retentate circuit 8. The raw juice supply can be regulated in a simple manner based on a pressure in front of the circulating pump 9 which is to be kept constant by means of the pressure regulator 39.

The method according to the invention can be used wherever the increased turbidity content in the retentate during a short residence time cannot have a disruptive effect on the quality of the end product and where high economy and stability against roughening are important. This applies above all to the production of bulk juices from fruit, grapes, berries or other fruits, and in some cases also to wine and beer, in particular to make the generally slow filtration less expensive. In the case of beer filtration, there is the possibility of making the filtration process less expensive by mixing the yeast and turbid matter deposited in the storage tanks during the secondary fermentation back into the tank contents before the crossflow filtration. Because of this, not only are higher filtration capacities achieved, but at the same time there is no need for a separate treatment of the tank support.

The present process is particularly predestined for the separate filtration of fermenter yeast and tank girders, which are very turbid. The flux in conventional systems is very low.

Due to the increased power (flux) of the crossflow filtration, the combination according to the invention of continuous pretreatment and continuous crossflow In many cases, stro filtration is economically more economical than the pure cross-flow filtration system. The combination according to the invention offers above all more security against subsequent clouding, in particular in the case of juices containing high polyphenols.

Claims

PATENT CLAIMS

1. Process for clarifying raw juice from fruit, grapes, berries or other fruits and vegetables or wine and beer by means of pretreatment and crossflow filtration, characterized by the indirect or direct combination of at least partially continuous pretreatment with an at least 1- stage, continuous cross-flow filtration system, which with a relatively high solids content in the retentate resp. a high concentration factor is operated.

2. The method according to claim 1, characterized in that the cross-flow filtration by means of large-channel modules with a channel gap width, respectively. a duct diameter of at least 4 mm is carried out.

3. The method according to claim 2, characterized in that the cross-flow filtration is carried out by means of tube modules.

4. The method according to any one of claims 1 to 3, characterized in that the cross-flow filtration is carried out by means of ultra or microfiltration.

5. The method according to any one of claims 1 to 4, characterized in that the wet turbidity content in the retentate of the cross-flow filtration at least 40% respectively. the concentration factor based on apple juice from the horizontal basket press is at least 20%.

6. The method according to any one of claims 1 to 5, characterized in that the cross-flow filtration is carried out warm at a temperature of at least 30 C.

7. The method according to any one of claims 1 to 6, characterized in that the raw juice in the Durchlaufverfah¬ ren first treated with at least one fining agent and after a residence time with at least one other fining agent. is mixed and then clarified at least indirectly by means of ultra or microfiltration.

8. The method according to any one of claims 1 to 7, characterized in that a further residence time after adding the last fining agent, respectively. after finishing the fining.

9. The method according to any one of claims 1 to 8, characterized in that the residence time after the addition of the last fining agent, respectively. is at least one minute after fining.

10. The method according to any one of claims 1 to 9, characterized in that a continuous advance, in which the fining at least partially is permanently removed, is achieved by flotation.

11. The method according to claim 10, characterized in that a continuous depectinization or pre-centrifugation can be connected upstream of the system.

12. The method according to claim 11, characterized in that the ejection of the pre-centrifugation is fed to the continuous cross-flow filtration.

13. The method according to any one of claims 1 to 12, characterized in that the amount required for the supply of fining agents is derived directly from the permeate amount measurement of the cross-flow filtration.

14. The method according to any one of claims 1 to 13, characterized in that the supply amount of raw juice is automatically controlled by regulating a control valve arranged between the feed pump and the cross-flow filtration, based on a pressure to be kept constant before the circulation pump of the cross-flow filtration.