Note: Descriptions are shown in the official language in which they were submitted.
~069~75
Specification:
The present invention relates to an aqueous com-
position containing tertiary butyl hydroquinone in bacterio-
static concentrations and an improved method for inhibiting
microbial growth in aqueous, normally biodegradable materials.
Terti-ary butyl hydroquinone (TBHQ) is known from the
prior art to ha~e anti-rancidity properties in that, at rela-
tively low concentrations, it inhibits oxidative rancidity of
fats and/or oils-in various materials. Such materials include
foods, soaps, food deri~atives, industrial oils, and the like.
It is believed that the rancidity is chemically induced when
atmosp-heric 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 character-
istic 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's~me'types of materials have'a water
' cont~nt 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 sup-
portive of microbial, mold or bacterial growt~. The'terms
"aqueous material" or "aqueous, normally biodegradable mater-
ial" 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 contentO
In many instances, it is desirable to control the
growth'of microorganisms within these aqueous materials so
1069375
as to retard undesirable decomposition and putrefaction.
Heretofore,it has not been recognized that tertiary butyl
hydroquinone will, when added in relatively high concentra-
tions, 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 aquebus material con-
taining 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 o~ this invention is an improved
aqueous material and method utilizing tertiary butyl hydro-
quinone as an agent for inhibiting the'development of micro-
organism 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 fsr inhibiting microorganism growth'within
aqueous, normally biodegradab~e materials.
Other objects and advantages of the present in-
vention will be apparent to those skilled in the art from
the'detailed description of the invention which followsO
It has been determined that tertiary butyl hydro-
quinone will inhibit the development of microorganisms within
aqueous materials. Certain concentrations of tertiary butyl
hydroquinone have been found to be bacteriostatic when in-
cluded in a variety of aqueous materials which would other-
wise support the growth of decomposing and putrefying micro-
organisms.- These ~aterials can take the form of a variety
~Q69375
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 contentO It has been dis-
covered that TBHQ also has valuable additional qualities as
an inhibitor to microbial growth'in aqueous materials applied
at leveIs greater than those previously utilized to reduce
oxidation. These levels -are'referred to herein as bacterio-
static 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 in-
hibit oxidative rancidity within the fat or oil component.
The bacteriostatic concentrations of T3HQ 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 micro-
organisms present in each particular aqueous material which
would normally grow to cause microbial deterioration.
The minimum leveI of these TBHQ bacteriostatic con-
centrations can be defined in terms of when evidence of anti-
microbial activity in the aqueous material begins to be real-
ized. Often when this is the case when the concentration of
-3-
io6s3q5
tertiary butyl hydroquinone approximates roughly 0.02 weight
percent of the aqueous, normally biodegradable material. How-
ever, it should be borne in mind that, in certain materials,
bacteriostatic effects can first become evident at TBHQ con-
centrations as low as 0.01 weight percent, based on thé 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 TB~Q within pasteurized
fluid whole milk.
Similarly, the maximum upper level of the TBHQ con-
centrations 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
TBEQ 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 approxi-
mateLy 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 thbse'conventionally referred to
as the concentration of added T~HQ, which conventional con-
centration 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 materialsO It is to be'understood that when
the aquebus 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
106i~375
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 hydro-
; quinone 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 else-
where 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 con-
ditions, 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 sc~e
other substance as a carrier~ The TBHQ is normally mixed with
the aqueous material in any conventional manner so as to
achieve a reasonably unifonm 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.
E X A M P L E
An aqueous protein suspension of bone glue, having
a 38 percent by weight solids content and which would normal-
ly undergo rapid spoilage was treated by adding vàrious levels
of tertiary butyl hydroquinone thereto. The levels in this
106937S
and the other examples are designated as "% TBHQ (W/W)~l to
indicate the weight percent of TBHQ that was added to the
aqueous material, based on the weight of that naterial. 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 r
that bacterial growth which causes spoilage causes the
production of ammonia which then renders impossible conven-
tional means for counting bacteria. The results are listed
in the following table:
Z TBHQ (WIW) 6 DAYS 11 DAYS 17 DAYS 42 DAYS
0 (Control) Spoiled SpoilPd Spoiled Spoiled
O. 001 " " " " ' '~
0.005 " " " " -
0.01. " " " "
0.02 O.K. O.K. O.K. "
0-04 " " " O.K.
0.08 " " " "
OoOl
From this data, it can be seen that bone glue, an aqueous pro-
tein 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 per-
cent.
E X A N P L E II
Various concentration of TBHQ were added to an
aqueous ma~erial that was an aqueous protein suspension con-
sisting of gelatin. Such a composition, without TBHQ, would
normall~ undergo rapid spoilage. This gelatin had a 30 per-
cent solids content based on weight. The samples were stored
-6-
.. . .... . . . . . . ....
1069375
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 (W/W) 4 DAYS 6 DAYS 8 DAYS 11 DAYS 17 DAYS 42 DAYS
0 (Control) O.K. Moldy Moldy Moldy Moldy Moldy
0.001 " l~
0.005 ll ll ll 1l il ,.
0.01 " O.K.O.K. " " "
0.02 " " Moldy ~9
0.04 " " O.K. O.K.
0.08 ~' ll ll ll ll ll -
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.
E X A M P L E III
~ . .
Tertiary butyl hydroquinone was added at various
concentrations to aqueous adhesive suspensions containing
starch and stored at room temperature for 42 days. The re-
sults are as follows:
% TBH~ (W/W) 8 DAYS 11 DAYS17 DAYS 42 DAYS
0 (Control3 Moldy MoldyMoldy Moldy
0.005 " " " "
0,01 O.K. " " "
0.02 " " " "
0.04 17 O.K.
0.08 " " O.K. "
O. 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.
10~i937S
E X A M P L E 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 four,
seven, and seventeen days of storage at 36F. are the observed
total plate counts per ml.
Z TBHQ (WtW) 0 DAYS 4 DAYS 7 DAYS 17 DAYS
0 (Control) 4 x 103 2.4 x 103 3.9 x 104 7.0 x 107
0.001 1.1 x 103 6.9 x 102 2.7 x 105
0.005 6.0 x 102 2.0 x 102 6.0 x 102
0.01 5.0 x 102 2.2 x 102 8.0 x 102
0.02 2.0 x 102 2 2 x 1o2 4 o x 1o2
0.04 2.0 x 102 2.9 x 103 6.0 x 102
0.08 2.0 x 102 2.7 x 102 8.0 x 102
0~1 2.0 x 102 2.3 x 102 2.3 x 103
E X A M P L E V
Experiments were conducted to evaluate the in-
hibitory effect of TBHQ on the following microorganisms:
Pseudomonas aeruginosa Ps6, Esterichia coli Es9~ Straphylococcus
aureus Stl2, fresh meat bacteria from fresh pork, and aerobic
sporeformers fr~ 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 respecti~e agars. Each was autoclaved
for fifteen minutes at 121C. The pork and soy flake~ were
diluted in phosphate buffer and spread onto the various agar
media in Petri dishes. Each of the pure strains of Ps6,
Es9 and Stl2 were grown for 24 hours at 37C in brain heart
infusion (BHI) broth, and about 10 cells were spread onto
prepoured plates containing the various agar media. Control
plates without TBHQ in the agar medium were included for each
-8-
106937S
bacteria as well as for the suspensions from soy flakes and
fresh meat~ Results after four days of incubation, consisting
of one day at 32C., followed by three days at room tempera-
ture~ were as follows, reported as plate count for each of
the agar media containing the various concentrat~ons of
TBHQ, again reported as %(W/W3 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 TB~Q TBHQ TBHO TBHO TBHQ
Pseudomonas 7.2 x Appr. Appr. Appr. Appr. 700*
aeruginosa 105 105 105 105 104
Escherichia 1.9 x Ap~r. Less* Less LessLess
coli 105 10 than than than than
10 10 10 10
Staphylococcus 2.5a x Less* Less Less Less Less
aureus 10 than than than than than
10 10 10 10 10 : ,
Soy Flake 1.6 x 1.9 x Less* Less LessLess
Bacteria 104 103 than than than than
10 10 10 10
Fresh Meat 6.5 x 5.0 x 2.~ x 5.3 x 7.~ x 2.7 x*
; 20Bacteria lo6 1o6 10 105 10 1o2
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 de-
parting from the spirit and scope thereof, and only such
limitations should be imposed as are indicated in the appended
claims.
_g_
