US2421380A - Method of treating sugar - Google Patents

Description

and destroy at least part of the sucrose.

Patented June 3,

name s. label], Washington, n. (2., minor to the Government of the United States I No Drawing. Application June 24,1941;

Serial No. 399,533

Claims; (01. 127-63) The invention described herein maybe manufactured and used by or for the Government for governmental purposes without the payment to meof any royalty thereon.

The present invention relates to a method of treating sugar;

It is an object of the present invention to provide' an improved method for the bleaching of sugar, wherein the colored impurities are bleached, without appreciable modification or destruction of the sucrose.

Another object of the invention is to provide a method of treating sugar which effects a bleaching action and also prevents bacterial action. Other objects of the invention will appear more fully from the following specification.

Heretofore, various chemicals, such as chlorine, hypochlorites and peroxides have been separately used for bleaching sugar solutions, but these have not been wholly satisfactory because they attack Furthermore, when the bleaching agent reacts with the sucrose, it is notavailable for reaction with the impurities.

In accordance with the present invention, these undesirable results are overcome by a process wherein the sugar or sugar solution is subjected to a simple chemical treatment which bleaches 'the impurities without destroying or causing the deterioration of the sucrose. This treatment contemplates broadly the bleaching of the sugar or magnesium chlorlte.

- 1 t The inventionaalso contemplates a process wherein the rate of bleaching may nbe regulated.v

maybe accomplished by adjusting {theacidity of the sugarchloritemixture-or byfthe i addition-oi? an expediting agents The'acidity of the mixture maybe controlled'by thezaddition of acids, such as sulphuric :or phosphoricaacids; or

emphasis on the prolonged germicidal action of the 'chlorite, the buffering or. neutralizingagent isadded to the sugar chlorlte mixture, thereby controllingthe acidity'thereof and also preventing acid hydrolysis of the sucrose; If a more rapid rate of bleaching is desired, the acidity of (Granted under the m or March 3, 1883, as amended April so, 192s; are 0. G. 757) more than compensates for'the slight sugar destructlon due to the expediting agent.

The practice of the invention is illustrated by the following examples wherein ordinary laboratory equipment may be used.

Example 1 sugar. The solution is allowed to stand four days at room temperature. During this period, the

- color of the sugar solution decreases from an original value of l0g5sot=.047 to a value of l0gssot=.00365, or approximately 92%. In this and subsequent examples, the color is measured by the method described by Brewster in the 1936 Journal Research National Bureau of Standards," volume 16, page 349.

II 1 part of sodium, calcium or magnesium chlorite per 1000 parts of sugar is used. the color reduction is from -logaaot=.047 to .0055, or approximately 80%. The amount of chlorite added depends on the amount and character of the impurities to'be bleached, and it also depends on the desired degree of bleaching.

The sugar solution containing the chlorite is now heated to approximately 80 C. and filtered. The filtered solutionmay be run through a column containing a decolori'zing carbon, such as animal charcoal, for the purpose of further decolorization and clarification. Experience has shown that the purifyingefiect of the decoloriz- .Ying carbon is greatly'increased by the previous treatment QfthesugarsoIution with the chlorite.

i se l' l l n i na s at in .vacuo. and brought to crystallization. The recentnrugau; r l

' .xl sqm leai;

,isuitin 'wh mfc" stals may separat d o a 4 by the addition" of abase-ortbuflerliig agent, such .I raw'sugar is mixed than equal weight I as calcium-carbonate'or sodiumbicarbonates If I a slow rate ofbleaching'is desired, with particularv oi!v water' and; with-5 part calcium chlorite per 1000 parts of; sugar; andthesolution-is made slightly acid by the addition ofan acid, say phosphoric acid. The solution is heated to approximately 70 C. and filtered. The filtered solution is concentrated in vacuo, and brought to crystallization. The resulting colorless crystals are separated in known manners 1 The reason for makingthe solution acid is that the bleaching action is more-rapid in acid than in neutral or alkaline solutions. However, since sucrose is hydrolyzed in strongly acid solution, it is necessary to regulate the. acidity during the I 2,4a1,seo

' 31 bleaching operation. for acidity is approximately pH 4.

The use of phosphoric acid in conjunction with the calcium chlorite is particularly advantageous. Not only is the bleaching effect accelerated by the acid, but the precipitation of the resulting cal- The higher practical limit I cium phosphate causes the removal. of colloidal matter from the sugar solution.

Example 3 g A raw sugar solution of 60 Brix'is heated to 75 C. and mixed with milk of lime to give an alkaline reaction with phenolphthalein. Calcium chlorite is added in the proportion of .3 part of chlorite to each 1000 parts of sugar. After mixing, the

\ alkalinity is neutraiizedwith monocalcium phosphate in suflicient quantity to give a precipitate that separates sharply from solution The warm solution is then filtered. The filtrate is treated with decolorizing carbon, filtered again and concentrated in vacuo. The resulting white crystals are separatedin conventional manner.

Example 4 The raw sugar is dissolved in an equal weight of water and is mixed with a 10% aqueous sodium chlorite solution in the proportion of 1 part sodium chlorite per 1000 parts of sugar. The acidity is adjusted to, say, pH 5 by the addition ofphosphoric acid. A aqueous sodium hypochlorite solution is added, as an. ex-

occurs, but only to a very limited extent.

Similar runs using calcium chlorite and sodium or calcium hypochlorite, instead of sodium chlorite and sodium-hypochiorite, give equally 4' a I remaining alter the removal of the bleached crystals contains the unused calcium chlorite. This sirup may be used again for preparing subsequent magmas. when, the, impurities inthe sirup become sufilciently higln the sugar is reclaimed therefromin known manner. f

While this example refers to the use of a chlorite in conjunction withchlorine, theiprocess may also be used with a chlorite alone, or with a. chlorite in conjunction with expediting compounds other than chlorine, such as iodine, bro- 'rine, bromine, iodine, acid. ypochlorites) may be satisfactory results. The relative proportions of hypochlorite and chlorite, whether calcium or sodium, may be varied over a considerable range. Satisfactory results are obtained with from 1 to 4 parts of hypochlorite per part ofchlorite.

Example 5 13 grams of blackstrap-molasses is dissolved in water to make 100 ml and treated, at room temperature, with 1 grand sodium: chlorite. In-

the course of eighteen hours; the. color decreases from -logmt=.253- to logmt=.00807', or approximately 97%. Upon treating. the solution with 1 gram of carbon and filtering. the color further decreases to -Walloon. v

' Should it be desirable'to expedite further the bleaching operation, chlorine, bromine. iodine or hypochlorite may be addedin the proportion of from ito 2 parts per part of sodium chlorite.

- Example 6 Raw sugar is mixed with a sugar sirup containing about 5 grams of calcium. sodium or magnesium chlorite per liter, to form a magma. Chlorine gas is then introduced'into the magma, as an expediting agent, to bring the acidity to, say, pH 5. The magma, which contains the bleached crystals, is now transferred to a centrifugal and the crystals separated. The sirup mine and hypochlorites.

Y Example 7 .A 1 kg. sample of raw sugar is treated with 10 ml of a 10% solution of calcium, sodium or magnesium chlorite by spraying the solution on the sugar. On standing, the compo! the treated raw sugar decreases perceptibly in the course of one day, and continues to decrease with time.

Should it be desirable to control the acidity of the sugar mixture containing the chlorite, calcium carbonate or other buflering agent may be added. The calcium carbonate thus prevents hydrolysis of the sugar, and the chlorite prevents .bacterial action. This is particularly important when the sugar is held in storage.

A particularly important commercial application of the process embodying the invention is in. the preparation of refined sugar. The chlorite, with or without the expediting agent (chloadded to the massecuite, which is prepared from the cane juice, and permitted to react in the conventional crystallizer; or it may be sprayed upon the raw sugar in the centrifugal," in which event the small quantity of chlorite remaining with the resulting raw sugar prevents bacterial action during storage, while continuing with a slow bleaching action; or it may be introduced into the mingling machine" with the raw sugar and sirup during the washing process; or it may be introduced into the "melt either before or after filtration.

The invention may be variously modified and embodied within the scope of the subjoined claims. i

I claim: v

1. The method which comprises subjecting crystalline sugar to the action of a solution containing a chlorite in an amount from'approximately .02% to .5% ofthe' weight of the dry sucrose, with the hydrogen ion concentration lying between pH 4 and pH 8.. 1

2. The method which consists in. subjecting crystalline sugar to the action of a solution containing a chlorite to: effect a bleaching action f and a preservative action.-

-3. The method which subjecting crystallinesugartotheaetionofasolutioneon- -tainingxs chlorite in an amount'fromapproximaul! .0296 15% ct-the weight Of'the sucrose, inthe presence of calcium carbonate in an amount'sufil'cient to maintain the hydr en ion concentration in the pH range of 4 to '8.

4. The method which consists in subjecting raw sugar, while in crystalline form, to the action of a solution containing a chlorite and a' neutralizing buffering agent in quantity sufilcient to maintain a substantially neutral reaction, to ef-- feet a bleaching action and a prolonged bactericidal eflect.

5. The method which consists in subjecting a sugar massecuite to the action of a solution contaming a chlorite, and Separating the treated taining sodium chlorite to efiect a bleaching of the'colored impurities, while simultaneously preventing bacterial action.

8. The method which comprises subjecting crystalline sugar to the action of a solution containing calcium chlorite to eflect a bleaching of the colored impurities, while simultaneously preventing bacterial action.

9. The method which comprises subjecting crystalline sugar to the action of a solution containing magnesium chlorite to eflect a bleaching and preservative action.

10. The method of bleaching crystalline sugar, while simultaneously preventing bacterial action, which comprises subjecting the crystalline to the action of a solution containing a chlorite of a non-toxic metal, with the hydrogen ion concentration lying between pH 4 and pH 8.

HORACE S. ISBELL.

REFERENCES CITED The following references are of record in the file of this ,patent:

UNITED STATES PATENTS Number Name Date 1,989,156 Sanchez Jan. 29, 1935 2,194,956 Taylor Mar. 26, 1940 2,145,062 Taylor Jan. 24, 1939 2,071,091 Taylor Feb. 16, 1937 2,253,368 Dubeau s Aug. 19, 1941 2,343,048 Eble Feb. 29, 1944