Antimicrobial and antirancidity agent

An aqueous composition includes a normally biodegradable component and contains tertiary butyl hydroquinone to inhibit microbial growth. Oxidative rancidity is also controlled when the composition has a fat or oil content. A method is described which adds tertiary butyl hydroquinone to aqueous biodegradable materials in concentrations that inhibit microbial growth.

The present invention relates to an aqueous composition containing tertiary 
butyl hydroquinone in bacteriostatic concentrations and an improved method 
for inhibiting microbial growth in aqueous, normally biodegradable 
materials. 
Tertiary butyl hydroquinone (TBHQ) is known from the prior art to have 
anti-rancidity properties in that, at relatively low concentrations, it 
inhibits oxidative rancidity of fats and/or oils in various materials. 
Such materials include foods, soaps, food derivatives, industrial oils, 
and the like. It is believed that the rancidity is chemically induced when 
atmospheric oxygen reacts with fats or oils in such items to accomplish an 
autoxidative production of peroxides that break down into aldehydes and 
ketones which exhibit odors characteristic of rancidity. The prior art 
teaches that tertiary butyl hydroquinone, at relatively low 
concentrations, will prevent this autoxidation and the resulting oxidative 
rancidity of fats and oils. 
Many of these same types of materials have a water content as well as a fat 
or oil content. Others, while they have little or no fat or oil, do 
contain water. These types of water-containing compositions or materials 
are exemplified by glues, gelatins, adhesives, starches, and the like. 
These types of materials can be considered as being normally supportive of 
microbial, mold or bacterial growth. The terms "aqueous material" or 
"aqueous, normally biodegradable material" are used interchangeably herein 
to refer to materials that include enough moisture so as to provide a 
medium for the growth of microorganisms, whether or not they also have a 
fat and/or oil content. 
In many instances, it is desirable to control the growth of microorganisms 
within these aqueous materials so as to retard undesirable decomposition 
and putrefaction. Heretofore, it has not been recognized that tertiary 
butyl hydroquinone will, when added in relatively high concentrations, 
inhibit the growth of microorganisms within aqueous, normally 
biodegradable materials. 
Accordingly, an object of the present invention is an improved aqueous 
material that is resistant to the growth of decomposing and putrefying 
microorganisms and a method for producing same. 
Another object is an improved aqueous material containing fats or oils and 
method for producing that material so that it resists both oxidative 
rancidity and the growth of microorganisms therein. 
One other object of this invention is an improved aqueous material and 
method utilizing tertiary butyl hydroquinone as an agent for inhibiting 
the development of microorganism growth. 
The present invention is an improved aqueous material which includes 
tertiary butyl hydroquinone present in concentrations that inhibit 
microorganism growth and an improved method for inhibiting microorganism 
growth within aqueous, normally biodegradable materials. 
Other objects and advantages of the present invention will be apparent to 
those skilled in the art from the detailed description of the invention 
which follows. 
It has been determined that tertiary butyl hydroquinone will inhibit the 
development of microorganisms within aqueous materials. Certain 
concentrations of tertiary butyl hydroquinone have been found to be 
bacteriostatic when included in a variety of aqueous materials which would 
otherwise support the growth of decomposing and putrefying microorganisms. 
These materials can take the form of a variety of products having a 
perceptible moisture content, such as foods, food derivatives, soaps, 
adhesives, industrial oils, and the like. 
Tertiary butyl hydroquinone has been known to be useful to impede the 
development of oxidative rancidity within materials having a fat and/or 
oil content. It has been discovered that TBHQ also has valuable additional 
qualities as an inhibitor to microbial growth in aqueous materials applied 
at levels greater than those previously utilized to reduce oxidation. 
These levels are referred to herein as bacteriostatic concentrations of 
TBHQ. Generally speaking, the bacteriostatic concentrations of TBHQ in 
aqueous materials which also contain fats or oils will not only, in 
accordance with the present invention, inhibit microbial growth normally 
expected from the water content thereof but also will be of a 
concentration that is known to be more than adequate to inhibit oxidative 
rancidity within the fat or oil component. 
The bacteriostatic concentrations of TBHQ contained in materials according 
to the present invention vary somewhat depending upon the make-up of the 
material itself and also upon the particular microorganism to be 
controlled. Such concentration variations will be evident from the 
examples herein. Basically, the degree to which TBHQ is effective as a 
bacteriostat is dependent upon the concentration of TBHQ, the conditions 
of manufacture (e.g. degree of heat processing), the environmental storage 
conditions, and the type of microorganisms present in each particular 
aqueous material which would normally grow to cause microbial 
deterioration. 
The minimum level of these TBHQ bacteriostatic concentrations can be 
defined in terms of when evidence of antimicrobial activity in the aqueous 
material begins to be realized. Often this is the case when the 
concentration of tertiary butyl hydroquinone approximates roughly 0.02 
weight percent of the aqueous, normally biodegradable material. However, 
it should be borne in mind that, in certain materials, bacteriostatic 
effects can first become evident at TBHQ concentrations as low as 0.01 
weight percent, based on the weight of the materials, as indicated in the 
examples herein. Also, for example, bacteriostatic effects have been 
observed at levels as low as 0.005 weight percent TBHQ within pasteurized 
fluid whole milk. 
Similarly, the maximum upper level of the TBHQ concentrations within the 
aqueous materials will be variable depending upon the aqueous, normally 
biodegradable material. Usually, such upper limit will be determined by 
economic considerations or considerations such as statutory maximum TBHQ 
levels and the like. A general statement in this regard can be made only 
to the effect that levels of diminishing returns often occur at 
concentrations on the order of approximately 0.1 weight percent TBHQ based 
on the weight of the aqueous material. 
It is to be noted that the concentrations herein are determined differently 
from those conventionally referred to as the concentration of added TBHQ, 
which conventional concentration is based upon the amount of fat or oil 
present in the system. In the present invention it is necessary to add the 
TBHQ on the basis of the total weight of the aqueous material to be 
preserved. 
The concentrations just discussed are, as previously mentioned, effective 
to inhibit the growth of microorganisms within aqueous materials. It is to 
be understood that when the aqueous materials contain fat or oil, these 
same levels will, as known heretofore, be more than adequate to retard 
oxidative rancidity of such fat or oil that would otherwise be expected to 
become evident within such materials with the passage of time. Evidence of 
both microbial growth and the onset of oxidative rancidity will be 
significantly delayed due to the addition of these bacteriostatic 
concentrations of TBHQ. 
The present method relates primarily to adding and mixing bacteriostatic 
amounts of tertiary butyl hydroquinone with aqueous, normally 
biodegradable materials so as to inhibit the growth and development of 
microorganisms. A discussion of concentrations needed to achieve such 
newly discovered use of TBHQ as a bacteriostat are contained elsewhere in 
this description, from which it will be seen that the concentrations vary 
depending upon the make-up of the aqueous material being treated, 
preparation and storage conditions, and the like. 
Depending upon the particular aqueous material being treated, tertiary 
butyl hydroquinone can be added directly thereto and mixed, or it may be 
added by using water or some other substance as a carrier. The TBHQ is 
normally mixed with the aqueous material in any conventional manner so as 
to achieve a reasonably uniform distribution throughout the aqueous 
material.

The following examples are presented to illustrate the present invention. 
It will be understood that the specific embodiments and illustrations 
should not be taken in any manner as limiting the invention as defined in 
the appended claims. 
EXAMPLE I 
An aqueous protein suspension of bone glue, having a 38 percent by weight 
solids content and which would normally undergo rapid spoilage was treated 
by adding various levels of tertiary butyl hydroquinone thereto. The 
levels in this and the other examples are designated as "% TBHQ (W/W)" to 
indicate the weight percent of TBHQ that was added to the aqueous 
material, based on the weight of that material. Each sample was stored for 
42 days and periodically observed for spoilage. Spoilage is determined for 
this composition by the presence of a strong ammonia-like odor. It is 
believed that bacterial growth which causes spoilage causes the production 
of ammonia which then renders impossible conventional means for counting 
bacteria. The results are listed in the following table: 
______________________________________ 
% TBHO(W/W) 
6 DAYS 11 DAYS 17 DAYS 42 DAYS 
______________________________________ 
0 (Control) 
Spoiled Spoiled Spoiled Spoiled 
0.001 " " " " 
0.005 " " " " 
0.01 " " " " 
0.02 O.K. O.K. O.K. " 
0.04 " " " O.K. 
0.08 " " " " 
0.01 " " " " 
______________________________________ 
From this data, it can be seen that bone glue, an aqueous protein product 
containing a very low level of fat, had bacterial growth therein inhibited 
for at least 42 days with storage at room temperature when TBHQ at a 
concentration of 0.04 weight percent was added thereto. Significant 
inhibition of bacterial growth was also realized at a concentration of 
0.02 weight percent. 
EXAMPLE II 
Various concentration of TBHQ were added to an aqueous material that was an 
aqueous protein suspension consisting of gelatin. Such a composition, 
without TBHQ, would normally undergo rapid spoilage. This gelatin had a 30 
percent solids content based on weight. The samples were stored at room 
temperature for up to 42 days, with observations thereof having been made 
to detect the growth of mold on the surface thereof. These observations 
are as follows: 
______________________________________ 
% TBHQ 4 6 8 11 17 42 
(W/W) DAYS DAYS DAYS DAYS DAYS DAYS 
______________________________________ 
0 (Control) 
O.K. Moldy Moldy Moldy Moldy Moldy 
0.001 " " " " " " 
0.005 " " " " " " 
0.01 " O.K. O.K. " " " 
0.02 " " Moldy " " " 
0.04 " " O.K. O.K. " " 
0.08 " " " " " " 
0.1 " " " " O.K. " 
______________________________________ 
These data indicate that the addition of TBHQ at levels from about 0.01 
weight percent and higher based on the total weight of the aqueous 
material resulted in a delay in the spoilage of the gelatin suspension. 
EXAMPLE III 
Tertiary butyl hydroquinone was added at various concentrations to aqueous 
adhesive suspensions containing starch and stored at room temperature for 
42 days. The results are as follows: 
______________________________________ 
% TBHQ (W/W) 
8 DAYS 11 DAYS 17 DAYS 42 DAYS 
______________________________________ 
0 (Control) 
Moldy Moldy Moldy Moldy 
0.005 " " " " 
0.01 O.K. " " " 
0.02 " " " " 
0.04 " O.K. " " 
0.08 " " O.K. " 
0.1 " " " " 
______________________________________ 
The length of time for mold to grow within the starch based adhesive, 
containing essentially no fat or oil, is seen to be proportional to the 
amount of TBHQ added to the system. 
EXAMPLE IV 
From the following data, it can be seen that the addition of TBHQ at a 
level as low as 0.005 percent (W/W) to pasteurized fluid whole milk 
prevents the growth of the normal spoilage bacteria associated with milk. 
Reported after 4, 7, and 17 days of storage at 36.degree. F. are the 
observed total plate counts per ml. 
______________________________________ 
% TBHQ (W/W) 
0 DAYS 4 DAYS 7 DAYS 17 DAYS 
______________________________________ 
0 (Control) 
4 .times. 10.sup.3 
2.4 .times. 10.sup.3 
3.9 .times. 10.sup.4 
7.0 .times. 10.sup.7 
0.001 1.1 .times. 10.sup.3 
6.9 .times. 10.sup.2 
2.7 .times. 10.sup.5 
0.005 6.0 .times. 10.sup.2 
2.0 .times. 10.sup.2 
6.0 .times. 10.sup.2 
0.01 5.0 .times. 10.sup.2 
2.2 .times. 10.sup.2 
8.0 .times. 10.sup.2 
0.02 2.0 .times. 10.sup.2 
2.2 .times. 10.sup.2 
4.0 .times. 10.sup.2 
0.04 2.0 .times. 10.sup.2 
2.9 .times. 10.sup.3 
6.0 .times. 10.sup.2 
0.08 2.0 .times. 10.sup.2 
2.7 .times. 10.sup.2 
8.0 .times. 10.sup.2 
0.1 2.0 .times. 10.sup.2 
2.3 .times. 10.sup.2 
2.3 .times. 10.sup.3 
______________________________________ 
EXAMPLE V 
Experiments were conducted to evaluate the inhibitory effect of TBHQ on the 
following microorganisms: Pseudomonas aeruginosa Ps6, Esterichia coli Es9, 
Straphylococcus aureus St12, fresh meat bacteria from fresh pork, and 
aerobic sporeformers from soy flakes. For each microorganism, a standard 
plate count (SPC) agar was made with TBHQ, the TBHQ being added at various 
weight percents based upon the total weight of the respective agars. Each 
was autoclaved for 15 minutes at 121.degree. C. The pork and soy flakes 
were diluted in phosphate buffer and spread onto the various agar media in 
Petri dishes. Each of the pure strains of Ps6, Es9 and St12 were grown for 
24 hours at 37.degree. C in brain heart infusion (BHI) broth, and about 
10.sup.5 cells were spread onto prepoured plates containing the various 
agar media. Control plates without TBHQ in the agar medium were included 
for each bacteria as well as for the suspensions from soy flakes and fresh 
meat. Results after four days of incubation, consisting of 1 day at 
32.degree. C., followed by three days at room temperature, were as 
follows, reported as plate count for each of the agar media containing the 
various concentrations of TBHQ, again reported as %(W/W) of the aqueous 
material. In this example, the aqueous material is the agar. 
__________________________________________________________________________ 
Control 
0.003 
0.01 0.02 0.05 0.1 
No % % % % % 
TBHQ TBHQ TBHQ TBHQ TBHQ TBHQ 
__________________________________________________________________________ 
Pseudomonas 
7.2 .times. 
Appr. 
Appr. 
Appr. 
Appr. 
700* 
aeruginosa 
10.sup.5 
10.sup.5 
10.sup.5 
10.sup.5 
10.sup.4 
Escherichia 
1.9 .times. 
Appr. 
Less* 
Less Less Less 
coli 10.sup.5 
10.sup.4 
than than than than 
10 10 10 10 
Staphylococcus 
2.9 .times. 
Less* 
Less Less Less Less 
aureus 10.sup.5 
than than than than than 
10 10 10 10 10 
Soy Flake 
1.6 .times. 
1.9 .times. 
Less* 
Less Less Less 
Bacteria 
10.sup.4 
10.sup.3 
than than than than 
10 10 10 10 
Fresh Meat 
6.5 .times. 
5.0 .times. 
2.8 .times. 
5.3 .times. 
7.5 .times. 
2.7 .times.* 
Bacteria 
10.sup.6 
10.sup.6 
10.sup.6 
10.sup.5 
10.sup.4 
10.sup.2 
Mold From Air 
Growth 
Growth 
Growth 
No* No No 
Growth 
Growth 
Growth 
__________________________________________________________________________ 
The above results exhibit the effectiveness of TBHQ in inhibiting the 
growth of various types of bacteria and mold. An asterisk indicates when a 
level of effectiveness begins to become evident. 
Obviously, many modifications and variations of the invention as 
hereinbefore set forth may be made without departing from the spirit and 
scope thereof, and only such limitations should be imposed as are 
indicated in the appended claims.