TECHNICAL FIELD

The present invention relates to a fumaric acid composition having an enhanced rate of solubility in cold water and to a method for manufacturing same.

Fumaric acid has long been used as an acidulant in various food products, particularly in dry beverages mixes where quick dissolution in cold water at 2 to 5°C is necessary. However, fumaric acid is hydrophobic in nature because of the low resultant dipole moment inherent in its chemical structure. Indeed solubility of fumaric acid in water at 25° C. is only 0.63 g. per 100 g. as compared to other acidulants such as citric acid or tartaric acid which are water soluble up to their own weight. Despite this drawback, fumaric acid treated with a wetting agent is preferred as an acidulant, because it is substantially more effective than its competitors.

BACKGROUND ART

Various wetting agents have been found, for example, U.S. Patent 3,009,810 issued to Raffensperger and Takashima showed that fumaric acid particles would dissolve readily, if they were coated with 0.2 to 2.0% by weight of a partial low chain fatty ester of a polyoxyeth lene derivative of hexitol ^• anhydride derived from sorbitol. Van Ness in U.S. Patent 3,151,986 eliminated the problem of agglomeration and caking

associated with the Raffensperger product by admixing with fumaric acid particles 0.1 to 1.0% by weight of a -dialkyl ester of sodium sulfosuccinate conatining 7 to 11 carbons in each alkyl chain. Demeler et al. -U.S. Patent 3,351,471 treated ultrafine fumaric acid crystals having a particle size below 10 microns with anionic and nonionic surfactants. This process, however, required that the particles of fumaric acid be in a micronized state in order for the dissolution in cold water to take place. U.S. Patent 3,370,956 issued to Reitmann and Hamilton enhanced the solubility of fumaric acid by treating acid crystals with a water solution of a water soluble edible surfactant, the solution optionally containing a water dispersible edible film forming additive. An example of the water soluble surfactant is a hydroxy- carboxylic acid of from about two to twelve cabon atoms such as citric and tartaric acid. The film forming additive was selected from the group consisting of carbohydrates, water soluble gelatins. and surfactants, with effective amounts of this component ranging from about 0.001 to about 0.7% by weight based on total solids.

In each of the above formulations the fumaric acid is mixed with a surfactant to enhance solubility. The surfactant lowers the surface tension at the solute crystal interface there¬ by accelerating the dissolution of the fumaric acid. The absolute solubility of the acid at a given temperature is, of course, unchanged.

Although the cold water soluble fumaric acid compo¬ sitions of the prior art all dissolved rapidly in cold water ■ various undesirable characteristics remained. The surfactant would cause the product to foam or exhibit off flavors. Due to static charges or the tackiness of the surfactant the product might cake and agglomerate. Shelf life was, at times, limited. Often, it was critical that the crystals have a particle size below 50 microns to facilitate dissolution. Another problem associated with these products was poor material handling characteristics such as low flowability, high dust generation, and inability of the product to be sieved. Further, most of the surfactants used were derived synthetically, and therefore have reduced consumer appeal.

DISCLOSURE OF INVENTION

The preferred product of■the present invention is a granular fumaric acid composition of increased solu¬ bility in cold water which has little off flavor, can be manufactured to a particle size between 50 and 400 U.S. Standard Sieve, and exhibits goods material handling characteristics. The solubility of the product is enhanced by coating fumaric acid crystals having a particle size,,., . between 10 and 40 microns with a film of a hydrol zed carbohydrate and then spray drying an aqueous slurry of-the treated particles to produce the granular product. The pre¬ ferred carbohydrate is a maito-dextrin consisting of at least 75 % by weight of polysaccharides above trisaccharides.

It is an object of this invention to produce a cold water soluble fumaric acid composition, said composition com¬ prised of fumaric acid particles coated wtih 2.5 to 10% by weight of a hydrolyzed carbohydrate wetting agent, the preferred carbohydrate being a maito-dextrin consisting of at least 75% by weight of polysaccharides above trisaccharides.

It is also an object of this invention to produce a granular composition of cold water soluble fumaric acid having a particle size between 50 and 400 U.S. Standard Sieve. ^* '•

It is another object of this invention to produce a fumaric acid composition that has little off flavor, good shelf life, little tendency to cake or agglomerate, and which can be handled readily.

An additional object of this invention is to produce a cold water soluble fumaric acid composition of granular par¬ ticles between 50 and 400 U.S. Standard Sieve that can be sieved, screened or classified to discreet particle size compositions.

It is a further object of this invention to provide a method for manufacturing this product.

Further objects of this invention will be apparent from reading the specification and the claims.

BEST MODE FOR CARRYING OUT THE INVENTION

Because fumaric acid is used as an acidulent in the food industry, particularly in dry water soluble beverage mixes, . an ingredient to be used as a wetting agent in a fumaric acid formulation must be edible. It should also be able to extend the shelf life of the fumaric acid, and not interfere in its characteristic acidic taste. We have, found that a hydrolyzed 0 carbohydrate of low sweetness and low dextrose equivalence can be used as a wetting agent for the fumaric acid. Preferably the hydrolyzed carbohydrate is a malto-dextrin, which is defined as a polysaccharide constitutionally between dextrin and maltose, the composition being dependent upon the relative amounts of each, 5 Malto-dextrin is readily digestible natural food derivative produced from starch in barley during the manufacture of malt or from hydrolysis of corn starch. Most preferably the malto-dextrin should have a composition which contains at least 75% by weight of a polysaccharide above trisaccharide. Commer¬ 0 cially, malto-destrin is available as Mor-rex (produced by Corn Products) and Maltrin (produced by Grain Processing Corporation) , which have the following typical physical properties and chemical analysis:

Phvsical Properties Mor-rex Maltrin M-100

5 Dextrose Equivalence 9.0 - 12.0 9.0 - 12.0 Moisture, % Max. 5.0 5.0 pH, 20% Solution 4.5 - 5.5 4.0 - 4.7 Bulk Density, g./cc. 0.513 - 0.577 0.513 Form white powder

Carbohydrate Analysis, % Dry Basis

Dextrose 1 1 Disaccharides _ 4

Trisaccharides 5 6

Tetrosaccharides 4 - .5

Pentasaccharides and above 86 84

Hexasaccharides and above 82 not available

The preferred malto-dextrin wetting agents have low hygro- scopocit , which enhances the ability of malto-dextrin containing compositions to be spray dried. Furthermore, this property extends the shelf life of dry mixes containing malto- dextrin by preventing moisture absorption. Not surprisingly, malto-dextrin is. accepted readily in the marketplace as a valuable food additive and is used currently in beverage powders, condi¬ ments, dehydrated foods, instant tea, cakes ^" and cookies to extend shelf life, control browning, and induce thickening.

Fumaric acid is a hydrophobic compound that is not easily wetted. Dissolution may be enhanced by drastic reduction in particle size in order to expose greater surface area to the solvent. Even then, however, the acid has a tendency to clump or agglomerate when added to an aqueous solution. While the reduction in particle size is beneficial, powdered fumeric is difficult to handle in that it has poor bulk flowability, creates substantial quantities of dust and is difficult to sieve properly.

Reduction in size accompanied by a coating of a surfac¬ tant to lower the surface tension increases dissolvability. Unfortunately, surfactants used as wetting agents tend to foam and can affect the taste of the ^' fumeric acid product. In some ^' instances the surfactant causes the fumaric acid crystals to cake or agglomerate thereby aggravating the material handling diffi¬ culties. Finally, poor shelf life is attributable to some surfactant materials.

Hydrolyzed carbohydrates are wetting agents which do not foam. Because they are low in sweetness they do not influence the flavor of the product, and have been used in a variety of other food preparations to extend shelf life.

Upon receiving a coating of a hydrolyzed carbohydrate, the outside surface of the fumaric acid particles is easily wetted so that they become dispersed throughout the solution. This

occurs because the malto-dextrin coating is hydrophilic in nature. Once the particles are dispersed, dissolution occurs at a faster rate, especially if accompanied by gentle stirring.

The fumaric -acid composition is obtained by milling fumaric acid crystals to a particle size between 10 and 40 microns, and then blending it with the hydrolyzed carbohydrates wetting agent. The particle size of the fumaric acid after the milling operation determines the smallest particle size of the final fumaric acid composition. Blending with the wetting agent may be performed in two ways. In the first method a dry mixture of fumaric acid particles and the wetting agent is obtained with the wetting agent comprising between 2.5 and 10% of the total dry mixture. This blend is then slurried with water to obtain an aqueous solution that is between 35 and 65% by weight solids. Alternatively the wetting agent may be admixed with milled fumaric acid by first dissolving the wetting agent completely in water, and then adding the fumaric acid particles to that solution to create a slurry as before. In each instance the object of coating the fumaric acid particles with the wetting agent is obtained by agitation of the slurry.

The slurry is then dried to obtain the finished fumaric acid product. Spray drying is preferred because the particle size of the final product can be regulated by proper selection of spray nozzle type and size, the pressure of the atomizing air, and the rate of drying. Typically, an inlet air temperature to the spray drying chamber is maintained between 150 to 250 ° C, while the outlet air temperature is controlled usually between 80 and 120° C. Atomizing pressures depend upon nozzle selection, but generally lie in a range between 20 and 100 psig. These procedures produce a fumaric acid composition that ranges between 10 and 300 microns in size or approximately between 50 and 400 U.S. standard sieve. The product, which is granular in texture, exhibits excellent flow characteristics and is low in dust formation. Thus, the spray dried fumaric acid composition of this invention may, unlike the prior art products, be sieved, screened or calssified to obtain products in particular particle size ranges. Volatile.- matter in the dried material is preferably

less than 1% by weight.

While the solubility of 'the fumaric acid composition remains dependent upon size to some extent, even the larger granules formed by the -spray drying operation dissolve readily. This is because each particle of each granule of fumaric acid is coated with the hydrolyzed carbohydrate wetting agent during the mixing operation. The preferred product, expecially the larger granules, consists therefore of substantial quantities of particles of smaller size held together by the hydrolyzed carbohydrate coating, each such particle being individually coated with the hydrolyzed carbohydrate. When the granules are added to an aqueous solution, the smaller particles are released leading to fast dis¬ solution of the granular composition. The hydrolyzed carbohydrate further enhances dissolution because the coating keeps the released particles apart and prevents them from clumping together in solution.

The dissolvability of fumaric acid as a function of time in 10% sugar solutions at 2 to 5° C. in grams per liter is shown in Table I below. Untreated fumaric acid is compared with 2.6, 5 and 9.1% malto-dextrin fumaric acid mixtures. From this table it is apparent that a fumaric acid composition containing between 4 and 7% malto-dextrin is preferred because higher concentrations of malto-dextrin increase the solubility of the acid in cold water only marginally. Above about 10% malto-dextrin the solubility of the fumaric acid in cold water .is not substantially enhanced.

TABLE I

Dissolvability of Fumaric Acid in 10% Aqueous Sugar ^" Solution at 2.5° C. (q./l.)

Seconds to Dissolve ^{* "} 30 60 12J) 300

Wt. % Malto-dextrin:

0 0 . 90 1. 20 1. 54 1 . 78

2 . 6 1 . 21 1 . 38 1 . 65 1 . 83

5 .0 1. 51 1. 72 1. 89 2 . 01

9 . 1 1. 62 1. 77 1. 86 2 . 00

EXAMPLE I

Twenty grams of Mor-rex malto-dextrin was dry mixed with 409 grams of fumaric acid milled to between 10 and 40 microns. This mixture was added to 600 milliliters of water at room tempera¬ ture to produce a slurry of about 40% by weight solids having a specific gravity of about 1.023 g./cc. The fumaric acid slurry was transferred from a two liter glass graduated feed flask to a two fluid aspirating type nozzle, Stork-3owen model number 59063, via a small Moyno pump at a feed rate of 77 ml./min. Using an atomizing force of 30 psig the slurry was sprayed through the nozzle into a vertical spray drying chamber and the dried fumaric acid compo¬ sition collected. The inlet air temperature was 160° C. and the outlet air temperature was 75° C. The material that was collected ranged in size from 10 to 60 microns and had 0.5% by weight volatile matter. The dissolvability of the treated fumaric acid in a 10% sugar solution at 2 to 5° C. was 1.51 g./l. after 30 seconds, 1.72 g./l. after 60 seconds and 1.89 g./l. after 120 seconds. At 20° C. the dissolvability in 10% sugar solution was 4.59 g./l. after 30 seconds, 4.61 g./l. after 60 seconds and 4.58 g./l. after 120 seconds.

EX AM LE 2

One hundred and eight grams of Mor-rex malto-dextrin was dry mixed with 1080' grams of fumaric acid milled to between 10 and 40 microns. This mixture was added to 1450 milliliters of water at room temperature to produce a slurry of about 45% by weight solids having a specific gravity of about 1.037 g./cc. The fumaric acid slurry was transferred from a glass graduated feed flask to a two fluid aspirating type nozzle, Stor -Bowen model number 5906B, via a small Moyno pump at a feed rate of 63 ml./min. Using an atomizing force of 30 psig (3.1424 kg/cm.^ aδs) the slurry was sprayed through the nozzle into a vertical spray drying chamber and the dried fumaric acid composition collected. The inlet air temperature was 160° C. and the outlet air temperature was 75° C. The material that was collected ranged in size from 20 to 80 microns and had 0.5% by weight volatile matter. The dissolvability of the treated fumaric acid in a 10% sugar solution at 2 to 5° C. was 1.62 g./l. after 30 seconds, 1.77 g./l. after 60 seconds and 1.86 g./l. after 120 seconds.

EXAMPLE 3

Ten grams of Mor-rex malto-dextrin was dry mixed with 375 grams of fumaric acid milled to between 10 and 40 microns. This mixture was added to 715 milliliters of water at room temp¬ erature to produce a slurry of about 35% by weight solids having a specific gravity of about 1.120 g./cc. The fumaric acid slurry was transferred from a glass graduated feed flask to a two fluid aspirating type nozzle, Stork-Bowen model number 5906B, via a small Moyno pump at a feed rate of 105 ml./min. Using an atom¬ izing force of 40 psig (3.8454 kg/cm. abs.) the slurry was sprayed through the nozzle into a vertical spray drying chamber and the dried fumaric acid composition collected. The inlet air temp¬ erature was 180° C. and the outlet air temperature was 75° C. The material that was collected ranged in size from 10 to 60 microns and had Q.5% bv weiσht volatile matter. The dissolvability of

the treated fumaric acid in a 10% sugar solution at 2 to 5° C. was 1.21 g/1. after -30 seconds, - 1.38 g/1. after 60 seconds and 1.65 g/1. after 120 seconds.

EXAMPLE 4

Six hundred and sixty pounds (299.4 kg.) of fumaric acid {previously milled to between 10 and 40 microns) was added to a. solution containing 35 pounds (15.9 kg.) of "Mor-rex"- alto- dextrin and 960 pounds (435.4. kg.) of water at room temperature ro produce a slurry of about 42% by weight solids. The fumaric acid slurry was transferred from a stainless steel feed ^' tank to ^' a dryer containing two SDX spray dry nozzles with 0.036 inch

(0.0914 cm.) orifices. Using an atomizing force of 900 psig

3 (64.3 kg. /cm. abs.) the slurry was sprayed through these nozzles into a horizontal spray drying chamber and the dried fumaric acid was screened and collected. The fumaric product was analyzed and found to contain 5% of the wetting agent. The inlet air temper¬ ature was 309° F. (154° C.) and the outlet air temperature was 172° F. (77.8° C). The material that was collected ranged in size from 325 mesh to greater than 170 mesh and had 0.5% by weight volatile matter. The dissolvability of the treated fumaric acid in ^' a 10% sugar solution at 2 to 5° C. was 2.01 g./l. after _. 30 seconds and 2.06 g./l. after 60 ^' seconds.

It should be understood that the foregoing examples are to beconstrued as illustrative rather than limiting. Wide deviations from these examples may be made without departing from a main theme of invention specified in claims which follow.