EP0092466B2 - Process for extracting beet juice - Google Patents

Abstract

1. A beet juice extracting process, in particular employing diffusion, of the type comprising previously treating beets cut into cossettes with calcium ions, characterized in that said prior treatment is effected by treatment of the cossettes with an aqueous solution of calcium saccharate, and a temperature less than 158 C.

Description

The present invention relates to a process for extracting beet juice, in particular by diffusion.

The processes of extraction of beet juice, formerly by pressure and now by diffusion, bring, with the juice containing sucrose, impurities and, in particular, pectic matters which, on the one hand, lower the purity, on the other hand, make subsequent filtrafions more difficult.

This is the reason why different authors have imagined insolubilizing pectic matter. To this end, they have proposed carrying out a preliminary treatment of the beets cut into cossettes with lime generally in the form of milk of lime.

Pectic substances are linear polymers of galacturonic acid. Part of the carboxyl groups is methylated, part of the hydroxyl groups is acetylated. When pectic materials are treated with lime, there are two reactions, first hydrolysis of the esters with formation of methanol and acetate, then degradation of the glycosidic bonds with decomposition of the polymer. When the temperature rises, the second type of reaction is favored. On the other hand, if the temperature drops, it is the first reaction which predominates and an insoluble calcium pectact is obtained.

The prior art therefore consisted either in treating the beet chips with lime, generally in the form of milk, or in adding lime to the water used for extraction by diffusion.

(See, for example: FR-A-895 534 and DE-C-817 880).

These processes have had no success because, at the temperature chosen for the action of lime on the cellular juice of beets, the OH-ions cut the glycosidic bonds of the carboxylic groups and destroy the pectic chain. The degradation of the pectins favoring the dissolution of the hemicellulose of the tissue, this greatly reduces the rigidity of the pods, prevents the percolation of the extraction liquid and makes it difficult to press the exhausted pods later.

The present invention aims to allow an improvement in the fixation of calcium ions on the galacturonic chains of the beet cut into pods, prior to the extraction operation, in particular by diffusion, without destroying the glycosidic bonds.

To this end, the subject of the present invention is a process for extracting beet juice, by diffusion, of the type comprising a prior treatment of the beets cut into chips with calcium ions, characterized in that said preliminary treatment is carried out by treating the cossettes with an aqueous solution of calcium saccharate obtained by adding quicklime to a diffusion juice at a temperature below 15 ° C.

The reaction can, in practice, be carried out between a temperature of 0 ° and a temperature below 15 ° C. Beyond that, there is a risk of breaking down the calcium saccharate.

The aqueous calcium saccharate solution advantageously contains from 1 to 15% by weight of calcium saccharate.

The invention is set out below in more detail using a drawing representing only one embodiment.

In this drawing, the single figure is a diagram of an installation for implementing the method according to the present invention.

The installation shown schematically in the single figure comprises a processing device A. The beets cut into pods enter 1 in this device, for example perclotation, which receives in 11 a saccharated juice at a temperature below 15 ° C.

After reaction and fixing of the calcium, the pods exit in 2 and are reheated in a heat exchanger B, for example percolation, by means of diffusion juice at 70 ° C. entering in 6. The pods which exit in 3 from the exchanger B are sent to a scalder C which receives in 4 a scalding juice (diffusion juice taken in the process and previously reheated). The juice-pod mixture heated to 70 ° C. leaves at 5 from the scalder C and is sent to a diffusion extraction apparatus, not shown, where the diffusion takes place for 50 to 80 min.

The pulps leaving the diffusion extraction apparatus undergo conventional pressing, for example by means of screw presses, bringing the dry matter content of pulps to more than 40%.

A part of the juice withdrawn at 7 from the exchanger B is brought at 8 to a heat exchanger D , where this juice is cooled to 4 ° C. by means of ice water entering at 15 and leaving at 16.

The cooled juice leaving at 9 from the exchanger D is introduced into a reactor E into which is also introduced at 10 quicklime powder. The reaction time is approximately 10 min. The saccharated juice which leaves at 11 is sent to the apparatus A as indicated above.

The juice leaving at 12 from the treatment apparatus A and the rest of the juice, discharged at 13, which is not withdrawn from the exchanger B for the preparation of the saccharated juice are combined at 14 and recovered.
By way of example, there are introduced into treatment apparatus A , at 1, 1000 kg of cossettes at 10 ° C. and, at 11, 227 kg of saccharated juice at 10 ° C. (pH = 12.6).

2.100 kg of calcium chips are obtained at 10 ° C., which are introduced into the exchanger B. In addition, exchanger B is sent at 6, 1413 kg of diffusion juice at 70 ° C.

In 3, 1220 kg of calcium chips are obtained at 54 ° C. which are introduced into the scalder C with 2425 kg of scalding juice at 75 ° C. 3645 kg of juice / pod mixture at 70 ° C. are sent, in 5, to the diffusion extraction apparatus.

From exchanger B, 1313 kg of diffusion juice cooled to 33 ° C. emerge, of which 220 kg are sent in 8 to exchanger D. After cooling to 4 ° C, the 220 kg of diffusion juice are added with 7 kg of quicklime powder at 10 ° C, in reactor E.

After reaction and treatment in the treatment apparatus A , there is discharged, in 12, 127 kg of potassium juice (after exchange of potassium ions with calcium ions). At 14, a total of 1220 kg of juice is drawn off.

The method according to the invention makes it possible to improve the purity of the extraction juices, to reduce the extraction time (of the order of 20%) and to improve the filterability of the juices.

The method according to the invention also makes it possible to improve the conditions for pressing spent pulp, thanks to the more rigid texture imparted by the fixation of calcium ions. Thus, it is possible to obtain by the method according to the present invention pressed pulps having a dry matter content of more than 40%, while the traditional methods allow to obtain pulps having at most dry matter contents from 27 to 28 %. The method according to the invention therefore makes it possible to achieve very significant energy savings.

Claims (1)

1. A beet juice extracting process by diffusion, of the type comprising a prior treatment of beets cut into cossettes with calcium ions, characterized in that said prior treatment is effected by treatment of the cossettes with an aqueous solution of calcium saccharate obtained by adding quick lime to a diffusion juice, at a temperature less than 15° C.

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