US1913776A - Bleaching of flour - Google Patents

Description

. and by this means all drawbacks inherent in Patented June 13, 1933 rm eraser, or BLOEMENDAAL, murmurs nmacrnive or 31mm.

7 No Drawing. Application filed larch 21, 1929, Serial No. 349,006, and in the Netherlands April 5, 1928.

The present invention relates to the bleaching of flour, by means of liquid organic peroxides. i

' It has already been proposed to bleach flour by mixing with it, organic "peroxides followed by a physical or mechanical treatment, for example, by the action of actinic rays, by warming or stirring, or both. The only practical method of proceeding was to 10 add the organic peroxide to the flour in a more or less, finely divided solid condition, although it has been proposed to add it in the form of a solution in volatile solvents and as a suspension in 'wat'enjilheuse o solutions, however, involves considerable 7 losses of the solvent,p and the use of suspensions or of the peroxide in the solid condition necessitates "fine\ grinding. which is diflicult and expensive, and even with the finest grinding which is possible in practice, the limited amount of exposed surface of the peroxide is a handicap in the bleaching process.

. It has now been found possible by using other peroxides than those hitherto proosed, to obtain a method which is technicaly practicable for bleaching flour, in which the chemical reagent does its workv while resent 1n the use of solutions, suspensions or $011 powders are obviated.

It has been found of considerable advantage to use organic peroxides-liquid below C., but mixtures giving to the flour a disagreeable odour are, ofcourse, of no pracr tical use.

According to the present invention, the bleaching of flour and other milling produets is effected by mixing them with a small amount of one or more organic peroxides that give no bad odour to the flour, and for this purpose the reagent used is a liquid diaromatic peroxide-whieh does not impart an 5 objectionable odour to the flour,

' liquid mixture of organic peroxides. The treatment'is preferably followed by a simple mechanical or physical after-treatment or by both. In carrying out the new process, it is not necessary to melt the peroxide or the the flour in the liquid condition, v

'many cases it results in a saving of the re- 50 d agent, or atleast'in a more rapid bleaching or is a mixture before it is mixed with the flour.

It can be brought to and kept in the liquid .state after it has been mixed with the flour in the solid state by the addition of substances that lower the melting point or retard-crystallization or both, and if necessary,

liquid reagent in water with or without f stabilizing colloids, ammonium salts, or organic nitrogen compounds of basic character, or by distributing throughout the flour a dry mixture of the liquid reagent with a mineral powder, such as kieselguhr, or a vegetable powder, such as rice starch, as has already been suggested for use with solid peroxides with a different object in view.

The novel method ives rise to an extremely uniform distri ution of the reagent through the flour and a very great active surface of the reagent. "The very intimate contact between the peroxide and the flour, however, does not give rise to any local deterioration of the flour grains, but in because, the comparatively large free surface assists the decomposition of the peroxide.

The least practical method of bringing the reagent into the liquid state is by melting the pure organic peroxides which melt at low temperatures of about 40 C. and already proposed for the bleaching of flour, namely, 'di-acetyl peroxide, benzoyl-acetyl peroxide, and hydrocinnamyl peroxide which when in the pure state have properties which are unfavourable for bleaching flour.

In particular, the hydro-cinnamyl peroxide is out of the question owing to its v though -orth0-toluyl and meta-toluyl peroxides which melt at somewhat higher temperatures, about 55 0., may give some intense and very' objectionable odour. Al-

trouble in actual practice, due to the tendency to sudden decomposition at melting temperature, they may nevertheless be used for the bleaching of flour in accordance with the present invention as they have the property of remainin' easily in the super-cooled state after they ave been melted, and particularly ,if they are absorbed by the flour while in the liquid condition.

Generally speaking, in order to liquefy peroxides below the temperature of 45 (3., which is generally regarded as dangerous, the methods of lowering melting points known from general scientific principles may be employed; for example, the reciprocal lowering of melting points by the action of different peroxides one on the other or the lowering obtained by the addition of difl'erent substances in amounts of not more than from 10 to 30% or by both methods combined. The mixtures obtained are at a temperature of 20 0., or at least below 45 (1, in the condition of a melt or of a s'uper-cooled'liquid. In order to lower the melting point in this wa substances such as low melting point so ids may be used, for example, benzoyl anhydride, benzophenone, which are added to the-peroxide in an amount not greater than that which gives an eutectic mixture.

Again, liquids may be used, for example in such an amount that the limit of miscibility is reached. In any event,'. the

- weight of the added material is always small relatively to the weight of the perox- 1de or peroxides, in contra-distinction to solutions in which the weight of peroxide is small relatively to the weight of the solvent, such as have been proposed for the bleachmg of flour but are not found to be fit for the purpose in practice.

In carrying out the new method of bleaching flour, the asymmetrical aromatic peroxides give best results; they are liquid at low temperatures and can be easily supercooled. In particular, the liquefied prod- 7 pets made in accordance with my co-pend- 113g application Serial No. 349,005. filed arch 21, 1929, may be employed. These may be prepared to have any desired meltmg polnt, even as lowas temperatures well below the normal room temperature.

, The stabilit in the super-cooled state may be im roved b adding to the mixture, or retam' g in t e mixture, related organio substances or decomposition products, even resinous substances such as benzaldehyde, benzo-phenone, or benzal-di-acetate. Even volatile substances may beused for lowering the melting point. They may leave behind in the flour after their whole or partial evaporation, a finely divided supercooled peroxide.

In some cases their vapour only suflices to render the peroxides deliquescent. Such bodies have the advantage that they have a low molecular weight, and therefore give or a negative catalyst; such substances include acetic acid orpyridine. Again, they may have a favourable effect on the viscosity or the surface tension of the peroxide, as, 1 for example, in the case of alcohols and ketones. An addition of suchbodies assists the absorption of the liquid peroxide into the particles of flour. This absorption may sometimes be so slow, especially when the flour is wet, that extremely fine drops of the liquid peroxide remain in the flour.

There is no difficulty in adding the mixtures of peroxides described above to the flour; they may, for. example, be injected from a fine spray. In any event,'nothing more than moderate warming not exceeding 45 C. is necessary to ensure that the reagent will be present in the flour in the liquid state. The flour, after the liquid peroxide hasbeenadded, may be subjected to physical or mechanical after treatment, as already proposed in the case of solid peroxides, or to energetic stirring for a shorter or longer period carried out in special apparatus to which heat is applied externally or generated by the friction in order to melt the peroxides or to make the bleaching more rapid.

On the other hand this stirring may be carried out in ordinary mixing machines 3 or flour apparatus. When the stirring is carried on for a long enough time, the liquid peroxide is completely absorbed in the flour particles, its surface is extremely extended, and all the advantages of the'new 1 method are fully obtained.

The advantages of the method described are generally speaking, ease of dosing into the flour, and easy uniform distribution without losing any amount of solvent, and 1 in addition, generally speaking quicker bleaching or less chemicalneeded. Moreover, some peroxides which cannot be used in the pure state can be employed when admixed with others, even when in the pure state there is risk of explosion 'or of local intense action, as in the case of phenylacetic peroxide, or if they. are liable to hydrolyze too easily, 'as in the case of benzoyl-acetyl. peroxide. When used in liquid this is the case with para-toluyl peroxide.

The cause of this may be that the organic M d formed from the peroxide during p to be treated.

bleaching does not accumulate at the surface of the particles of the peroxide, but is dissolved in the liquid reagent.

The following are examples of methods of keeping the peroxides in the liquid state at a low temperature: or without danger of decomposition.

.Example 1 Di-ortho-toluyl peroxide and di-metatoluyl peroxide each alone has a melting point above 55 C. However, they yield an eutectic mixture melting at about 33 C. A

mixture containing ortho toluyl peroxide,

zoyl peroxide melts at 26 0., while the eutectic point is some degrees lower still.

Example 3 A mixture of ortho toluyl-benzoyl peroxit ide with di-ortho-toluyl peroxide remains liquid below 20 C.

Example 4 Example 5 Di-ortho-toluyl peroxide is stirred cautiously with 9 parts of dry rice starch at 55 to 60 C. until the: mass has become a dry. powder again. After cooling to. room temperature, the peroxide is present in the liquid state but soaked up in the starch gran-- Example 1 The mixture described under Example 1 above is sprayed While moderately heated in the desired amount directly into the flour Example 2 The mixture described under Example 2 following subaboveis emulsified inwater to an amount of 2% to form a milky liquid. A very small amount of ammonium oleate is employed as a stabilizer and the mixture is sprayed into the flour in a Humphries' apparatus. The mixture described in Example 2 above may again be mixed with a little water and oleic acid and stored for preparing emulsion with a large quantity of water and the calculated amount of ammonia at a later time.

Example 3 The mixture described under Example 3 above is mixed with 10% of acetone to make 'it more fluid, and is sprayed into the flour without heating.

Example 4 The powder obtained in accordance with Example 5 above is mixed with flour in a proportion of 114,000 parts.

The following are two examples of aftertreatment after adding the peroxide to the flour.

Example 1 A liquid peroxide prepared in accordance with Examples1-or3 above is mixed with flour in a proportion of 1: 40,000in accordance with any of the aboveexamples. The mixture is passed through agitating drums and mixing worms for some minutes. Inspection under the microscope shows that the peroxide, is no-longer present in the form of fine drops, but is soaked up into the flour particles. Also the colour reaction with Rothenfussers reagent shows extremely uniform distribution of the peroxide.

Example 2 Flour is mixed with a small amount of a solidified mixture of meta-toluyl and or tho-toluyl peroxides and stirred at a temperature of 35 oxide becomes soaked up into the flour in C. After some time the per- I the liquid condition. Instead of heating the flour mixed with the peroxide, the mixture may be brought into .contact with acetone vapour. After a certain amount of stirring, the peroxide becomes soaked up into the flour.

What I claim is 2-- 1. A method of bleaching flour and other milling products at a temperature not exceeding 45 0., which consists in mixing with the product to be treated a small amount of liquid organic non-dialiphatic peroxide, which does not contain hydro-'cin-o namyl peroxide and which does not solidfy at 45 0., and maintaining a bleaching temperature at which the peroxide remains in the liquid state. I

2. A method of bleaching milling products at a temperature not exceeding 45 C., which consists in mixing flour and other I with a product to be bleached a small amount of liquid -diaromatic perox1de, which does not contain hydro-cinnamyl eroxide and which does not solidify at 45 5 and maintaining a bleaching temperature at which the peroxide remains in the liquid state. 3. A method of bleaching fiour and other milling products, which consists in mixing with the product to be treated at a temperature not exceeding 45 C. a small amount ofv liquid organic aromatic peroxide in a super-cooled state, and maintaining the mixture at a temperature not exceeding 45 C. I e I 4. A method of bleaching flour and other vmilling products, which consistsin mixing the product to be bleached at a temperature not exceeding 45 (3., with a. small amount of organic non-dialiphatic peroxide which does not contain hydro-cinnamyl peroxide, liquefying the peroxide after its addition to the flour at a temperature below 45 C. by means of a volatile organic substance, and maintaining the mixture at a temperacure-below 45 C. I

5. A method of bleaching flour and other milling products at a temperature not exceeding 45 C., which consists in mixing W with the product to be treated a small amount 0 liquid organic non-dialiphatic peroxide, which does not contain hydro cinnamyl peroxide, and related organic substance having a low melting'point, which is soluble in the peroxide-in a quantity less than 50% of the peroxide and which will wholly dissolve inthe li uid peroxide at a temperature below 45 and maintaining a bleaching temperature below 45 C. att :vhich the peroxide remains in the liquid s a e.

6. A method of bleaching flour and other milling products at a temperature not exceeding 45 (3., which consists in mixing with the product to be treated a small amount of liquid diaromatic peroxide, which does not contain hydro-cinnamyl perox1de, which does not solidify at 45 C., and a peroxide, which in pure condition is a solid substance below 45 (1., in a quantity which will wholly dissolve into the liquid dlaromatic eroxide at a temperature below 45 (1., an maintaining a bleaching temperature below 45 C. at which the peroxide remains in theliquid state.

JAN STRAUB.