Mold growth inhibitor and method

A dry, powdery composition containing mold inhibiting quantities of sorbic acid or a salt thereof and sodium diacetate may be coated on grain or grain products to inhibit mold.

FIELD OF THE INVENTION 
This invention relates broadly to the field of agriculture, and 
particularly to the field involving long-term storage of whole-kernal 
grains such as corn. 
BACKGROUND OF THE INVENTION 
Whole grain cereals such as corn, oats and the like, when harvested, 
commonly contain significant amounts of moisture, e.g., in the range of 
from 20%-35%. When stored under aerobic conditions, whole kernel grains 
quickly develop mold which in turn not only renders the grain less 
palatable to animals but additionally may form toxic substances known as 
mycotoxins. 
One method of reducing or inhibiting mold growth involves the drying of 
whole kernel grains immediately after harvesting to reduce the moisture 
content of the grains. Another method involves the treatment of whole 
kernel grains with solutions containing mold-inhibiting chemicals such as 
sodium diacetate, or certain organic acids such as propionate acid, and 
blends of acetic acid and sorbic acid. Solutions of mold-inhibiting 
chemicals, such as aqueous solutions of formalin, propionic acid, formic 
acid, benzoic acid, acetic acid, sorbic acid, isobutyric acid, etc., have 
been used to treat silage. One researcher has reported the treatment of 
silage with an aqueous solution containing sodium diacetate and sorbic 
acid or a salt thereof, optimum results being reported at a concentration 
of 0.04% sorbic acid and 0.02% sodium diacetate. Reference is made to G. 
Cirilli et al, Corn Silages and Spores, 1st Note-Antifungal Treatments, 
Tecnica Molitoria, 19-20; Cirilli, Mycostatic and Antimycotic Activity of 
Aflaban--Experimental Study, 1976-1980, Report of International Free 
University, Laboratory of Applied analytical Chemistry, Bologna, Italy; 
Glabe, U.S. Pat. No. 4,034,117; and Glabe et al, U.S. Pat. No. 4,015,018. 
Prior to the present invention, the generally preferred method for 
inhibiting mold growth on whole kernel grains such as corn was the drying 
process which reduces the moisture content to about 15% but which also is 
very expensive and, further, decreases feed value. The treatment of whole 
kernel grains with solutions of propionic acid, blends of acetic and 
sorbic acid, and sodium diacetate, all for the purpose of inhibiting mold 
growth, have shown some promise but do not appear to be commercially 
feasible. 
SUMMARY OF THE INVENTION 
It has now been found that mold growth in whole kernel grain can be 
inhibited by coating the grain kernels with an effective amount of a dry, 
particulate, finely divided, powdery composition containing 
mold-inhibiting quantities of sodium diacetate and sorbic acid or a salt 
thereof. This treatment of freshly harvested grain (containing from about 
20% to about 35% moisture, typically about 22%) can be accomplished 
quickly and easily without the use of complex spraying devices and without 
adding additional moisture to the grain. The treatment has proven very 
effective in inhibiting mold growth, and appears to involve a 
substantially complete coating of each grain kernel with the powdery 
composition. Although any appropriate means of applying the composition to 
grain kernels can be employed, the preferred method involves the 
introduction of grain and the composition to a rotating "tumble" drum in 
which the kernels rub together and in which each kernel is substantially 
completely coated with the composition. 
In a preferred embodiment, the particulate composition includes sorbic acid 
or a salt thereof and sodium diacetate in a weight ratio of about 0.04/1 
to about 1/1, respectively. This particulate composition is particularly 
effective in inhibiting mold growth, and exhibits far better results than 
may be obtained through the use of equal amounts of only sodium diacetate 
or only sorbic acid. 
The preferred weight ratio of sorbic acid to sodium diacetate in the 
particulate composition is from about 0.2/1 to about 0.7/1. The 
composition may contain a variety of other particulate materials that do 
not interfere with the mold-inhibiting action of the composition. For 
example, the composition may include a small amount of an anti-caking 
material, such as a zeolite, to maintain the particulate composition in a 
free-flowing condition. Fillers or carriers such as bentonite, clays and 
kaolin, may also be employed. 
DETAILED DESCRIPTION 
Both sorbic acid and sodium diacetate are nontoxic to man or animals when 
used in the proportions useful in the instant invention. Salts of sorbic 
acid, such as the sodium or potassium water-soluble salts, can be employed 
in place of the sorbic acid which is only slightly soluble in water. 
Sorbic acid itself, however, is preferred. 
The particulate composition of the instant invention may be prepared simply 
and readily by dry-mixing together suitable quantities of sorbic acid and 
sodium diacetate in a suitable blender or drum until a substantially 
homogenous physical mixture thereof has been obtained. It is possible, 
though unlikely, that some chemical reaction may occur between the sorbic 
acid and sodium diacetate even when mixed and stored in dry form, 
resulting, perhaps, in the production of acetic acid and the sodium salt 
of sorbic acid. Accordingly, as used herein, the recited compositions that 
include sorbic acid and sodium diacetate will be deemed to include any 
reaction products thereof as well. The substantially homogenous 
particulate composition may include, as well, small quantities of known 
anti-caking materials, typified by Zeolex 23-A, a product of J. M. Huber 
Corp. Sodium diacetate is somewhat hydroscopic, and the presence of the 
anti-caking material helps to maintain the free-flowing characteristics of 
the composition. Additional dry carriers or fillers such as bentonite, 
clay and kaolin may be employed as well. It is believed that the use of 
such fillers may contribute to the homogeneity of the dry coatings that 
are formed on each kernel. Through the use of fillers such as those 
described above, the amounts of sorbic acid or its salts and sodium 
diacetate may be significantly reduced, thereby reducing the raw material 
cost of the composition. 
Treatment of whole kernel grains with the composition of the invention may 
be accomplished in a variety of ways. Appropriate amounts of the 
composition and grain may be added to a closed container, and the 
container itself may then be shaken, rolled or otherwise agitated to cause 
the kernels to rub against each other and thus to cause each kernel to 
become substantially coated with the particulate mixture. On a continuous 
basis, one may employ a drum having intake and exhaust ends, the drum 
being positioned generally horizontally with its exhaust end slightly 
lower than its intake end. Quantities of grain and of the mold-inhibiting 
composition may be charged to the intake end of the drum, and the drum, 
which is rotatable about its generally horizontal axis, may have a series 
of interior paddles or vanes to agitate the grain and composition as the 
drum is rotated or "tumbled" about its axis, the substantially 
homogenously coated grain kernels being withdrawn on a continuous basis 
from the exhaust end of the drum. Tumble drums in and of themselves are 
well known in the art, as are devices for metering quantities of seeds or 
of powdered substances. The latter devices often employ small hoppers for 
measuring given amounts, by volume or weight, of seeds or other materials, 
the hopper contents being discharged, in a predetermined manner, into the 
drum. 
If desired, the sorbic acid or its salt and the sodium diacetate may 
separately, preferably concurrently, be coated upon the grain. With 
reference to the tumble drum described above, the sorbic acid or its salt 
and the sodium diacetate may separately be charged to the drum or may be 
mixed together immediately before they are charged to the drum. 
The coating which ordinarily is formed on grain kernels in accordance with 
the invention is exceedingly thin, and often can be visually perceived 
only with great difficulty with the unaided eye. 
The amount of the mold-inhibiting composition, by weight, that is employed 
with a given weight of grain is that amount which effectively inhibits 
mold. The effective concentration of the composition thus may vary 
according to the ratio of sorbic acid or its salts to sodium diacetate 
within the composition. For example, a composition having a weight ratio 
of sorbic acid to sodium diacetate of approximately 0.44/1 gave excellent 
mold-inhibiting results when used at a concentration by weight of 0.5% 
based on the weight of freshly harvested corn having a moisture content of 
approximately 22%. With a ratio of sorbic acid to sodium diacetate of 
approximately 0.11/1, excellent results were obtained at a concentration 
of the composition of approximately 1% by weight based upon the weight of 
the corn. The concentration of the composition also will depend upon the 
amount of moisture in the grain, and the grain moisture content may also 
require modification of the ratio of sorbic acid or its salt to sodium 
diacetate in the mold inhibiting composition. 
The dry, powdery composition of the invention may also be employed to 
inhibit mold growth in such grain products (usually moist or wet) as 
middlings, brewer's by-products, corn gluten feeds and wet mashes from 
alcohol production. The preferred use, however, is with whole kernel 
grains.

EXAMPLE 1 
To each of 57 glass jars was added 606 grams of freshly harvested whole 
kernel corn having a moisture content of 22%. The kernels in each jar were 
coated, as set out in Table 1 below, with a quantity of a candidate 
mold-inhibiting composition, the coating operation involving rapidly 
agitating a container of the corn kernels with a composition. The jars, 
with their tops open, were then stored at 70.degree. F.-80.degree. F. and 
at about 70%-85% relative humidity. The jars were periodically visually 
inspected for mold growth, and the following table reports the number of 
days required before mold growth was visually observed. 
TABLE 1 
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Days to Formation of Visible Mold 
Percent by Weight of Inhibi- 
tion Based on Weight of Corn 
Candidate Inhibitor 
0.0% 0.5% 1.0% 
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(A) Control (no inhibitor) 
5 -- 
(B) 97% Sodium diacetate 
-- 12 60 
3% Zeolex 23-A 
(C) 87.3% Sodium diacetate 
-- 5 90+ 
2.7% Zeolex 23-A 10% 
Sorbic acid 
(D) 77.6% Sodium diacetate 
-- 12 90+ 
2.4% Zeolex 23-A 20% 
Sorbic acid 
(E) 68.9% Sodium diacetate 
-- 90+ 90+ 
2.1% Zeolex 23-A 30% 
Sorbic acid 
(F) Sorbic acid (100%) 
-- 5 9 
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EXAMPLE 2 
Various candidate mold-inhibiting compositions were used to treat batches 
of corn freshly harvested at ten different farms in Wisconsin. The 
moisture content of the batches of corn varied from about 19% to about 
33%. Certain batches of the corn were treated only with sodium diacetate 
at varying concentrations. Other batches were treated with a mixture of 
sorbic acid and sodium diacetate at a weight ratio of approximately 0.4/1. 
The results, reported in Table 2, indicate the expected increased 
susceptibility to mold of high moisture corn, and further show the 
excellent mold-inhibiting qualities of the formulation of the invention. 
The corn was treated in drums, and the treated corn was stored in steel or 
wood bins on each farm and was monitored daily for mold growth. The number 
of days required for approximately 30% of each batch of grain to become 
discolored and to show deterioration from mold growth is reported in the 
last column of Table II. 
TABLE 2 
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On-Farm Storage 
Days to Formation of Mold 
Results: 
Farm % Moisture 
Candidate Inhibitor 
Wgt. % Days 
______________________________________ 
A 19-21 Sodium diacetate 
0.6 90+ 
B 28-30.5 Sodium diacetate 
0.6 21 
C 20-22 Sodium diacetate 
0.7 90+ 
D 27.5-32 Sodium diacetate 
0.6 21 
E 17-20 Sodium diacetate 
0.75 14 
F 22-25 Sodium diacetate 
0.3 14 
G 26.5-28.5 Sodium diacetate 
0.45 14 
H 30-33 Sodium diacetate 
0.6 28 
I 28 Sorbic acid/ 0.3 90+ 
Sodium diacetate: 
0.4/1 
J 28 Sorbic acid/ 0.45 90+ 
Sodium diacetate: 
0.4/1 
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EXAMPLE 3 
An inhibitor was prepared containing 77.6% of sodium diacetate, 2.4% of 
Zeolex 23-A as an anti-caking agent, and 20% of sodium sorbate, the 
percentages being by weight. The resulting dry, powdered mixture can be 
added to whole kernel corn within a glass jar which is shaken vigorously 
to coat the composition upon the corn kernels and to inhibit the formation 
of mold. 
While a preferred embodiment of the present invention has been described, 
it should be understood that various changes, adaptations and 
modifications may be made therein without departing from the spirit of the 
invention and the scope of the appended claims.