Abstract:
There is provided, a method for preserving high moisture content agricultural grains, which comprises treating such grains with a composition consisting essentially of: 1) an organic food-grade acid or phosphoric acid, 2) any water-soluble, non-corrosive, non-toxic, alkali or alkaline earth metal sulfate salt, and 3) a synthetic organic cationic or anionic surfactant for enhancing the penetration of said acid into said grains.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application is a continuation-in-part application of our earlier co-pending application, Ser. No. 466,777, filed May 3, 1974, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. FIELD OF THE INVENTION 
     The present invention is directed to a method for preserving high moisture content agricultural grains which become subject to bacterial degradation due to the high moisture content present. More particularly, the present invention is directed to a method for preserving high moisture content agricultural grains by treating said grains with a specific acid/alkali or alkaline earth metal sulfate salt/surfactant admixture. 
     In our co-pending application of identical title, there is described a means for preserving high moisture content grains employing a mixture of a food-grade organic acid or phosphoric acid and a surfactant. The present invention is an improvement over that invention. 
     2. DESCRIPTION OF THE PRIOR ART 
     U.S. Pat. No. 3,682,653 employs a surfactant and propionic acid, in combination, as a grain conditioner lubricant for softening a mass of whole kernel grains. Essentially, the patentee employs a mixture of liquid lecithin, propionic acid, and water. The propionic acid serves to reduce the pH of the lecithin and permits the lecithin to become water dispersible. 
     The invention of the patentee is quite different from that disclosed and claimed herein for a number of reasons. Firstly, the patentee is not at all concerned with the preservation of high moisture content grains. Secondly, the patentee requires the presence of a natural amphoteric surfactant (lecithin), whereas, as will be seen from the discussion which follows, a synthetic organic cationic or anionic surfactant is required for this invention to enhance the spreading factor of the acid contained in applicants&#39; composition required to preserve the high moisture content grains. Non-ionic or amphoteric surfactants will not suffice for applicants&#39; purposes. 
     Finally, one observes upon a reading of this patent, that the patentee requires propionic acid for the purpose of dispersing the lecithin, whereas in the instant invention, the surfactant is employed for the sole purpose of dispersing the acid of applicants&#39; composition in the high moisture content grain for preservation purposes. 
     Aside from the foregoing, according to the patentee, 1/4 lb. of acid per ton of grain would be required, whereas with the present invention, appreciably more acid per ton would be required, and as such, the patentee&#39;s acid content would be so minimal that preservation of a high moisture content grain could not be achieved. 
     U.S. Pat. No. 2,890,120 discloses a method for preserving edible plant materials, i.e., fruits and vegetables which become deteriorated via enzyme deterioration. Specifically, the method includes applying to said plant materials, a composition containing at least an acid, a volatile oxygenated organic solvent and a wetting (surface active) agent. The invention of this patentee is distinguished from the invention disclosed and claimed herein on at least three bases. Firstly, the plant materials of the patentee are deteriorated via enzymes whereas the grain material disclosed in the instant invention is deteriorated through bacteria as a result of the high moisture content present. Secondly, an alkali or alkaline earth metal sulfate salt is an absolute requirement for the instant invention whereas for the patentee, it is not taught or suggested. Finally, the patentee requires the presence of a volatile oxygenated organic solvent for two reasons: 1) to facilitate the penetration of the patentee&#39;s acid through the cell walls and membranes of his plant materials, and 2) for acting synergistically with the other components of the patentee&#39;s solution to promote enzyme inactivation. In the instant invention, no volatile oxygenated organic solvent is at all required. In fact, to employ such would be detrimental to the purposes intended to be achieved by the applicants. 
     SUMMARY OF THE INVENTION 
     It is the primary object of the present invention to provide a method for preserving high moisture content agricultural grains. 
     Accordingly, to this end, it is intended for the purpose of this invention to employ a high moisture content agricultural grain preserving composition, which consists essentially of: 1) a food-grade organic acid or phosphoric acid, 2) an alkali or alkaline earth metal sulfate salt, any one of which is characterized as being water soluble, non-corrosive and non-toxic to the grain treated, and 3) a synthetic organic cationic or anionic surfactant for enhancing the penetration of the acid employed in this composition into the high moisture content grain for effecting preservation of the same. Non-ionic or amphoteric surfactants will not serve applicants&#39; purposes here. 
     In terms of definition, the term &#34;food-grade organic acid&#34; refers to conventional organic acids approved for use with food products and with respect to the expression &#34;non-corrosive&#34; respective of the alkali or alkaline earth metal sulfate salt, this expression simply indicates that the salt must be non-corrosive to the high moisture content grains treated, as well as being non-corrosive and non-toxic to animals who might consume such grains. 
     The term &#34;high moisture&#34; as it pertains to agricultural grains means any agricultural grain whose moisture content is 18% or more. 
     DETAILED DESCRIPTION OF THE INVENTION 
     With respect to the food-grade organic acids suitable for the purpose of this invention, those acids which are preferred, are those of formic acid, acetic acid, propionic acid, and lactic acid. Of these, propionic acid is the acid of choice because it not only serves the function required of an acid for the purpose of this invention, but, in addition, this particular acid is an effective fungicide and as such, enhances the preservation power of the composition employed. However, any other food-grade organic acid approved for use by the Food and Drug Administration&#39;s &#34;GRAS&#34; list is acceptable also. 
     Respective of the inorganic sulfate salts, suitable for applicants&#39; purposes, sodium sulfate is preferred. However, potassium, calcium, magnesium or any other alkali or alkaline earth metal sulfate will equally suffice. 
     With respect to the concentration parameters for the acids, alkali or alkaline earth metal sulfates and surfactants employed in applicants&#39; composition, naturally, the concentration of same will vary over wide limits, depending upon the moisture content of the grain treated. However, generally, the following guidelines are suggested. 
     For 1 ton of grain containing 25% moisture content, the following active ingredient concentrations are suitable for applicants&#39; purposes: 
     1. Acid -- 10 lbs. 
     2. Alkali or alkaline earth metal sulfate salt -- 1/2 lb. 
     3. Surfactant -- 1 lb. 
     Similarly, for one ton of grain having a moisture content of 15%, the following active ingredient concentrations are suitable: 
     1. Acid -- 21/2  lbs. 
     2. Alkali or alkaline earth metal sulfate salt -- 1/8 lb. 
     3. Surfactant -- 1/4 lb. 
     Referring to the above examples, with respect to the grain having a moisture content of 25%, 12% of that moisture is inactive. Consequently, the amount of active water in the 25% moisture grain is actually 13% (25-12%). 
     Similarly, with respect to the grain having a 15% moisture content, the amount of active moisture contained in said grain would be 3%, (15-12%). 
     Accordingly, 15% moisture grain requires 3/13 times the formula or roughly 1/4 of the formula used for application to a 25% moisture grain. This is based on perfect mixing conditions. For practical purposes it may be necessary to use an inert diluent. Based on the foregoing guidelines, it is believed that the skilled artisan can easily calculate the amount of acid, alkali or alkaline earth metal sulfate, and surfactant required for applicants&#39; purposes simply by determining the amount of moisture content contained in a particular grain and calculating the amount of each active ingredient required on a proportional basis in light of the above guidelines. 
     With respect to the surfactants suitable for applicants&#39; purposes, applicants do not limit themselves to any particular cationic or anionic surfactant. That is, virtually any of these will suffice for applicants&#39; purposes. However, without limitation, the following commercially available surfactants have been found to be quite suitable. Any sodium alkylsulfonethanolamine; any ammonium or sodium alkylarylpolyethersulfonate (Triton); any long alkyl chain sulfonate; any alkyl aryl sulfonate; any sulfonated fatty acid; or any sodium sulfosuccinate. Specific illustrative examples of the following aforementioned types of surfactants are: sodium dodecylsulfonethanolamine, ammonium dodecylbenzenepolyethersulfonate, sodium dodecylbenzenepolyethersulfonate, dodecylsulfonate, sodium dodecylbenzenesulfonate, sulfonated myristic acid, sulfonated palmitic acid, sulfonated stearic acid and di-(2-ethylhexyl)sodium sulfosuccinate. These and other cationic and anionic surfactants useful in the instant invention can be found in the text entitled &#34;ENCYCLOPEDIA OF SURFACE ACTIVE AGENTS,&#34; by Sisley and Wood, published by Chemical Publishing Company, New York, N.Y. (1964). 
     Naturally, for the purpose of this invention, more than one food-grade acid can be employed; that is, mixtures of conventionally acceptable food-grade acids are equally as suitable for the purposes of this invention. 
     With the foregoing in mind, the following brief explanation will provide the skilled artisan with a basis to fully understand the uniqueness and novelty of the present invention. 
     Firstly, the basis of this invention is the realization that food-grade acids can be used to preserve high moisture content grain, such as corn grain or any other agricultural grain which tend to deteriorate via bacteria as a result of the high moisture content present. However, a problem arises when using such an acid and mainly, the acid alone cannot normally penetrate or permeate through the high moisture content grain sufficiently to impart this preservative effect. 
     Consequently, the uniqueness of the instant invention is the realization that when an alkali or alkaline earth metal sulfate salt, as heretofore described, is combined with a conventional food-grade acid and a synthetic organic cationic or anionic surfactant capable of enhancing penetration of that acid through high moisture content grains, the alkali or alkaline earth metal sulfate salt, somehow combines with the surfactant to enable the food-grade acid to fully penetrate throughout the high moisture content grain so as to permit an overall substantial preservative effect to be achieved. 
     It is interesting to note that when the alkali or alkaline earth metal sulfate salt is deleted from applicants&#39; composition, or in the alternative, when the surfactant is omitted, inferior acid penetration and hence, little or no preservation effect is observed. Consequently, for the purpose of this invention, the combination of acid heretofore described, the alkali or alkaline earth metal sulfate salt heretofore described, and the surfactant is absolutely essential to achieve applicants&#39; goal. 
     In application, one simply determines the amount of high moisture content grain to be treated as well as the amount of moisture contained in that grain. The amount of moisture contained in a particular grain can be easily determined by means well known to the skilled artisan concerned with the subject matter of this invention. Subsequently, based upon these estimations, the basic formulation of the present invention is prepared by simply mixing together the essential ingredients. Then, the prepared formulation is applied to the high moisture content grain by any suitable means, for example, spraying the same onto the grain mass, until the high moisture content grain is saturated with the formulation. 
    
    
     A better understanding of the present invention will be gained from the following examples, which are simply illustrative and nonlimitative thereof. 
     EXAMPLE I 
     This example, set out in two parts (part A and part B) illustrates the &#34;spreading factor&#34; discussed in connection with the formulation of this invention. 
     
         ______________________________________PART A(RATE OF PENETRATION OF THE ACID THROUGH THEGRAIN MASS, THE SPREADING FACTOR)                       InchesFormulation                 Per Hour______________________________________50% -  Propionic acid           5.050% -  Mixture of Propionic acid (60%)  and Acetic acid (40%)    5.150% -  Propionic acid and 1/4% sodium sulfate                           16.450% -  Mixture of Propionic acid/Acetic acid  and 1/4% sodium sulfate  17.050% -  Propionic acid and 1/10% sodium alkyl-  sulfonethanolamine*      7.550% -  Propionic acid and 1/10% sodium alkyl-  sulfonethanolamine* and 1/4% sodium  sulfate                  19.8______________________________________ *sodium dodecylsulfonethanolamine 
    
     Each of the above formulations were diluted with distilled water to the required percent. 35mm Pyrex tubes (specially prepared) were employed. High moisture corn (25%) was packed in the tubes at 5 lbs. per square inch at each inch level. All experiments were conducted at 70° F. These values hold only for the particular batch of corn used and are not absolute, and vary with the degree of attrition if ground. 
     
         __________________________________________________________________________PART B(RATE OF PENETRATION OF THE ACID THROUGH THE GRAIN KERNEL,THE ABSORPTION FACTOR)Formulation                 Percent Absorption                       in hours                       1/2                          1  2  4  12 24__________________________________________________________________________50% -Propionic acid         20 24 28 28 30 3750% -Propionic acid/Acetic acid-60/40 mixture          19 23 26 29 32 3550% -Propionic acid and 1/4% sodiumsulfate                27 29 31 32 38 4950% -Propionic acid/Acetic acid mixtureand 1/4% sodium sulfate                       19 24 26 27 35 4450% -Propionic acid and 1/10% sodiumalkylsulfonethanolamine*                       30 38 35 56 64 7550% -Propionic acid/Acetic acid mixtureand 1/4% sodium sulfate and sodiumalkylsulfonethanolamine* (1/10%)                       63 67 79 90 91 9050% -Propionic acid, 1/4% sodium sulfateand 1/10% sodium alkylsulfonethanolamine*                       51 60 71 80 92 93__________________________________________________________________________ 
    
     In the above comparative studies, 100 gram portions of the 25% moisture corn were employed. The various test liquids were mixed at the rate of 1% with the grain mass. The preparation was allowed to stand for the varying time periods noted at 50° F. The test liquids were then eluted from the grain with three successive washes of distilled water. Aliquots were titrated for acid not absorbed and calculations were noted for the percent of acid absorbed. These values are not absolute and hold only for the particular batch of corn used, and vary with the degree of attrition, if ground. 
     EXAMPLE II 
     
         GROWTH OF MOLD IN 30% HIGH MOISTURE CORN AT 70°FFormulation                 Days                       4  14 28    80__________________________________________________________________________1/2% -Propionic acid         0  1  2     31/4% -Propionic acid         1  2  4     41/2% -Propionic acid and 1/4% sodium sulfate                       0  0  4     41/4% -Propionic acid and 1/4% sodium sulfate                       0  4  4     41%   Propionic acid, 1/4% sodium sulfate and1/10% sodium alkylsulfonethanolamine*                       0  0  0     01/2% -Propionic acid, 1/4% sodium sulfate and1/10% sodium alkylsulfonethanolamine*                       0  0  0     01/4% -Propionic acid, 1/4% sodium sulfate and1/10% sodium alkylsulfonethanolamine*                       0  0  1     4__________________________________________________________________________ *sodium dodecylsulfonethanolamine 
    
     In the above comparisons, 200 gram samples in wide mouth jars with loose lids were allowed to stand over water in a loose-lidded container at 70° F. The growth of mold in the high moisture corn employed was then determined. The degree of mold growth ranged from 0 or no growth to 4 or maximum growth. 
     EXAMPLE III 
     With respect to the surfactants illustrated previously and used for applicants&#39; purposes, the following data, set out in Table I below is pertinent from the standpoint of demonstrating the ability of the surfactants to enhance acid penetration. 
     
                                           TABLE I__________________________________________________________________________                            PercentSurfactant                       Absorption__________________________________________________________________________Sodium alkylsulfonethanolamine*+propionic acid (50%)                            75Ammonium alkylarylpolyethersulfonate.sup.1 +propionic acid                            790%)Sodium alkylarylpolyethersulfonate.sup.2 +propionic acid                            770%)Sulfonated fatty acid.sup.3 +propionic acid (50%)                            68Propionic acid by itself (50%)   33__________________________________________________________________________ *sodium dodecylsulfonethanolamine .sup.1 ammonium dodecylbenzenepolyethersulfonate .sup.2 sodium dodecylbenzenepolyethersulfonate .sup.3 sulfonated palmitic acid 
    
     Conditions same as in Example I, part B. 
     These values are not absolute and serve only as examples as they vary with the particular batch of corn used, and degree of attrition, if ground. These are weighted values based on the surfactant employed and propionic acid. 
     It should be emphasized that while the foregoing examples have been directed to high moisture content corn, it is obvious that other high moisture content grains are susceptible to the same treatment. 
     Although the present invention has been adequately described in the foregoing specification and examples included therein, it is obviously apparent that various changes and/or modifications can be made thereto without departing from the spirit and scope thereof.