FR2652093A1 - PROCESS FOR DECOLORING SUGAR JUICE. - Google Patents

Abstract

Process for extracting the sugar contained in plants such as sugar beet or sugar cane, in which the concentration of a juice diluted by evaporation of water to result in a juice from which the sugar is separable by cristallsation, relates to a diluted juice with the addition of hydrogen peroxide, the pH of which, with the addition of hydrogen peroxide, is between 8 and 9.5.

Description

The present invention relates to a process for bleaching sweet juice

  in the extraction of the sugar contained in plants such as beets or sugar cane, more particularly a process of discoloration of such a juice which uses hydrogen peroxide. The extraction of sugar commonly involves four main operations: - the formation of a raw juice, for example by crushing the plant as in the case of sugar cane or by diffusion of the plant's sugar in water as in the case of sugar beet, - the purification or purification of raw juice by the action of lime, called liming, followed by carbonation then sulphitation and possibly decalcification to provide a purified juice which, by compared to raw juice, contains a quantity of impurities, the "non-sugars", usually reduced by at least half, - the concentration of the purified juice, by evaporation of water, to provide a concentrated juice, or dense juice , syrupy liquid generally containing around 70% sugar, from which the sugar can be separated by crystallization,

  - the crystallization of the dense juice, followed by drying

  ge, to supply commercial white sugar and molasses

as a residue.

  A description of sugar extraction can be found

  for example in "Sucrerie Française" October 1985, 439-454,

  or in U.S. Patent No. 4,076,552.

  The presence of colored impurities or generators of coloring in the dense juice, gene, even makes it impossible,

  obtaining crystallized sugar of satisfactory quality.

  As the documents cited above show, it is by sulphiting the juice before concentration that the influence of such impurities is limited today. The O

  is the commonly used sulfiting agent.

  It has not only the drawbacks linked to its odor and its toxicity but also that of leaving residual sulfur in the crystallization effluents as in the sugar produced, when the standards or recommendations in

  this area is becoming more and more draconian.

  The replacement of the sulphitation by an operation at least as effective but not posing any problem of

  sugar quality is therefore desired by the industry.

  R.F. MADSEN, W. KOFOD NIELSEN, B. WINSTROM-OLSEN,

  T.E. NIELSEN, "Sugar Technology Review", 6 (1978/79), 49-115, in particular pages 108-110, note that the addition of hydrogen peroxide in the diffusion or in the raw juice has

  a favorable effect on the coloring of the juice before concentra-

  However, it is not possible to avoid sulfita-

  one of the necessary conditions not to

  have excessive browning during evaporation. The addi-

  tion of hydrogen peroxide in the present diffusion of

  the more the disadvantage of darkening the color of the vegetable matter

  the exhaustion of its sugar, the pulp, whose bleaching for use in the food sector will be all the more

more difficult and expensive.

  The addition of hydrogen peroxide in the raw juice is also recommended in the patent of United States of America No. 4076552 already cited. According to this patent hydrogen peroxide

  must be added to the juice just before and / or during the carbona-

  tation. To be best performed, this method requires that during a first carbonation in the absence of hydrogen peroxide the pH be maintained between narrow limits. The hydrogen peroxide must also be added in the presence of a sufficiently large quantity of calcium carbonate otherwise its effect is less and may even result in a stronger coloring of the juice. The patent confirms the observation of R.F. MADSEN et al. already mentioned, as to the need to follow the action of hydrogen peroxide of a sulfitation before concentration. The patent also teaches that one of the roles of sulfitation is to ensure the destruction of any residual hydrogen peroxide which otherwise

  would have a detrimental effect on the quality of the sugar produced.

  Thus, according to the art of the technique, hydrogen peroxide cannot be substituted for a sulphiting agent such as SO in the treatment of a juice which must undergo concentration by evaporation of water and which is designated in

all of the following by diluted juice.

  Yet it is this substitution that allows the pro-

  assigned to the present invention which does not have the disadvantages

  mentioned above and is carried out independently of

  raw juice and liming operations-

  carbonation while effectively limiting the coloring of

lo concentrated juice.

  The present invention consists of a process for extracting the sugar contained in plants such as sugar beet or sugar cane, a process in which a diluted juice is concentrated by evaporation of water to lead to a juice from which the sugar can be separated by crystallization, characterized in that a concentration by evaporation of water relates to a diluted juice supplemented with hydrogen peroxide, whose pH, addition made of hydrogen peroxide, is

between 8 and 9.5.

  What has been stated above with regard to the four main operations of extraction applies to the process of the invention except obviously for what relates to the

sulfitation which is avoided.

  The amount of hydrogen peroxide to which is added

  The diluted juice can vary within fairly wide limits, but a sensible result is generally not obtained when adding less than 30 g. about hydrogen peroxide counted as 100% per tonne of raw material, such as beet or cane, presented for extraction for

  form the raw juice as said further.

  In all of the following the amount of hydrogen peroxide

  drogen added to the diluted juice to form the diluted juice addition-

  born of hydrogen peroxide is counted as it says just above. It is preferably between 50 g./T. and

100 g./T.

  Hydrogen peroxide is added to the diluted juice to

  concentrate, normally in the form of an aqueous solution

  mercial like for example a 35% or 50% solution in

weight of hydrogen peroxide.

  Diluted juice, with added hydrogen peroxide

  born, is at a temperature which can be between approximately C and 150 C but which is preferably in the range of temperatures at which the concentration of the diluted juice is carried out by evaporation of water, for example between approximately

   C and 120 C, preferably between about 60 C and 100 C.

  Diluted juice, with added hydrogen peroxide

  born, is at a pressure which can depend on the chosen temperature and which is normally between atmospheric pressure o10 and a pressure less than about 0.08 bar, most often between atmospheric pressure and 0.1

bar approx.

  The pH of the diluted juice, addition of the peroxide

  of hydrogen, is preferably between approximately 8.5 and 9.

  It can be naturally ensured by the simple fact of adding hydrogen peroxide to the diluted juice, or, if necessary, be regulated by means of a compatible non-sulfur agent.

  with food use such as acetic acid.

  If the diluted juice, addition made of hydro-

  gene, has a pH greater than 9.5 when it is subjected to a concentration by evaporation of water, the dense juice obtained is clearly more colored than that resulting from the concentration by evaporation of water of the same diluted juice not added with peroxide of hydrogen but subjected to sulfitation before

concentration.

  If the diluted juice, addition made of hydro-

  gene, has a pH below 8 when it is subjected to a concen-

  tration by evaporation of water, the crystallization of sugar at

  from dense juice is made difficult.

  The diluted juice to which hydrogen peroxide is added most often contains about 10% to 50% of

sugar by weight.

  The diluted juice to which the invention applies can in fact be a diluted juice which has not yet been subjected to a concentration by evaporation of water and / or a juice which has already been partially concentrated in this way during its transformation into dense juice from which the sugar is separated by crystallization.

  The result aimed by the present invention is nor-

  badly reached in a period between the time when the hydrogen peroxide is used and that at which the diluted juice is found in the form of dense juice, which does not exceed twenty minutes approximately. Most often this duration is

in the range of 5 to 15 minutes.

  The equipment for carrying out the present invention, from the use of hydrogen peroxide to the production of dense juice, is designed like that known today to be suitable for concentration by evaporation of water from a juice. diluted into a dense juice. The material chosen must suit the conditions

  of execution of the process and the requirements of the food sector

  re. Stainless steel meets this double requirement.

  The following examples, given as an indication but not limiting, illustrate the invention in comparison with

known techniques.

  In these examples the coloring of the juices is determined

  born by measuring the absorbance at 420 nm using a refractor

  tometer on the various juices concerned filtered through a porous membrane. This method is known to those skilled in the art. It is based on the protocol established at Community level

  European and is described for example in 1984 by IRIS-

  Sugar Industry Research Institute.

  In each of the examples, the value 100 is assigned to the coloring of the dense juice obtained from the diluted juice.

  to which the present invention is applied.

  In each of the examples, a value of the colora-

  tion greater than 100 means for the diluted juice or for a juice derived therefrom other than the dense juice obtained according to the invention, a darker coloring than that of said dense juice. Conversely, a value of the coloration less than translated for the diluted juice or for a juice derived therefrom other than the dense juice obtained according to the invention, a coloration more

white than that of said dense juice.

  The starting juices used in all the examples are industrial diluted juices. They contain, next to

  water and impurities, 14% to 15% sugar by weight.

  The hydrogen peroxide is used in the form of a 35% commercial aqueous solution of hydrogen peroxide in

  weight. The values of the committed quantities of hydro-

  gene are expressed in grams of 100% hydrogen peroxide per tonne of raw material presented for extraction to form the raw juice, g./T., as was said earlier in

this text.

  When there is sulfitation of the diluted juice before evaporating

  tion of water instead of using hydrogen peroxide according to the invention, it is practiced in a conventional manner, using SO used at a rate of 205 g / tonne of material

  defined as for the quantities of hydrogen peroxide.

  The raw material here is sugar beet.

Example 1:

  The diluted starting juice, whose pH is equal to 9.3 and the color value equal to 90, is added with

  hydrogen peroxide at a rate of 73.5 g./T.

  Addition of hydrogen peroxide, the pH of the juice is brought to a value equal to 8.5 using acetic acid

  and the juice is left in this state for 10 minutes.

  Until the end of this period, the temperature of the juice is equal to a value maintained between 90 C and 100 C. The

  pressure is atmospheric pressure.

  The juice is then concentrated by evaporation of water, at atmospheric pressure, so that the dense juice collected

contains, by weight, 68% sugar.

  The value of its coloring is equal to 100 as agreed. When the same diluted starting juice as above is concentrated at atmospheric pressure after it has been sulphited, the dense juice with a sugar content by weight still equal to 68%, has

  a coloration whose value is 102.5.

  By bringing the concentration by evaporation of water at atmospheric pressure directly to the diluted starting juice used for this example, the coloring of the dense juice obtained, which always contains, by weight, 68% sugar, is

equal to 205.

Example 2:

  The process at the start of Example 1, which incorporates the invention, is followed by leaving the diluted juice, addition made of hydrogen peroxide, at pH 9.2 naturally reached by the very fact of this addition. The dense juice obtained has a coloring whose value is practically equal to that of the dense juice obtained in

  Example 1 from the sulphited juice.

Example 3:

  A diluted industrial juice other than that used in

  examples 1 and 2 has a color value equal to 108.5.

  It is loaded into an evaporator operating at a pressure below atmospheric pressure and equal to about 0.1 bar so that the temperature of the juice during its concentration by evaporation of water remains understood

between 65 C and 75 C.

  g./T. hydrogen peroxide is added to the diluted juice during its rise in temperature from room temperature to working temperature. Addition of hydrogen peroxide, the pH of the diluted juice is adjusted as in

  Example 1 has a value of 8.5.

  The dense juice obtained contains, by weight, 70.5% of sugar and the value of its coloring is equal to 100 as agreed. The dense juice, with a sugar concentration also equal to 70.5% by weight, which is obtained by replacing in the above process the intervention of hydrogen peroxide and the correction of pH by sulfitation, has a coloration of which

the value is 108.

  The above examples show that the use of hydrogen peroxide according to the invention at the time of the concentration of a diluted juice by evaporation of water to form a dense juice, leads to dense juices of coloring at least

  as satisfactory as that achieved when said concentration

  tion relates to a diluted sulphite juice.

  White sugar, obtained by crystallization according to the process adopted industrially from the various juices

  dense resulting in the examples of the application of the in-

  vention, meets each time the coloring criteria as well as those of sucrose content,

  ashes and of course sulfur content, imposed by its trade

specialization.

Claims (10)

  1. Process for extracting the sugar contained in plants such as sugar beet or sugar cane, in which a diluted juice is concentrated by evaporation of water to   lead to a juice from which the sugar can be separated by crystallization   sation, characterized in that a concentration by evaporation   of water relates to a diluted juice supplemented with hydrogen peroxide   ne, whose pH, addition of hydrogen peroxide, is between 8 and 9.5.   2. Method according to claim 1, characterized in that the diluted juice is added with a quantity of peroxide   of hydrogen greater than 30 g./T.   3. Method according to claim 2, characterized in that the amount of hydrogen peroxide is between g./T. and 100 g./T.   4. Method according to one of claims 1 to 3,   characterized in that the temperature of the diluted juice, with added hydrogen peroxide, is between 20 C and C. 5. Method according to claim 4, characterized in   that the temperature is between 40 C and 120 C.   6. Method according to claim 5, characterized in   what the temperature is between 60 C and 100 C.   7. Method according to one of claims 1 to 6,   characterized in that the diluted juice, with added hydrogen peroxide, is at a pressure between the   atmospheric pressure and 0.08 bar.   8. Method according to claim 7, characterized in   that the pressure is between atmospheric pressure than and 0.1 bar.   9. Method according to one of claims 1 to 8,   characterized in that the pH of the diluted juice, addition of   hydrogen peroxide, is between 8.5 and 9.   10. Method according to one of claims 1 to 9,   characterized in that the diluted juice contains by weight between 10% and 50% sugar.