Note: Descriptions are shown in the official language in which they were submitted.
CA 02618372 2008-02-07
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TITLE OF INVENTION
CHEW PRODUCT IMPREGNATED WITH CALCIUM
FIELD OF THE INVENTION
This invention relates to a chew product useful for the dental hygiene of
animals such as dogs. The chew product of the invention is manufactured from
rawhide, preferably scrap material from a leatller tanning process, wherein
the
rawhide is delimed, bleached, impregnated with calcium, rolled, and dried. The
impregnated calcium imparts desirable properties to the chew product of the
invention including: whitening the product, adding nutritional value, and
aiding in
dentalliygiene.
BACKGROUND OF THE INVENTION
A problem with conventional processes of making rawhide chew products
is the difficulty of simulating the white color of bone. To solve this
problem, a
titanium dioxide coating has been employed as a whitening agent. However, the
most readily commercial available form of titanium dioxide contains
impurities.
Because of the difficulty and added costs of removing these impurities to make
food grade titarziuin dioxide, it would be advantageous to discover an
alternative
wliitening agent.
The addition of calcium as a wliitening agent in chew products is known.
Some processes mix calcium witli comminuted rawhide which is then molded or
extruded into a dog chew product such as U.S. Patent No. 6,972,133 issued to
Denesulc et al. Unfortunately, such processes require the use of added
machinery
for comminuting, and molding or extrusion.
Frudakis et al., in U.S. Patent No. 6,165,474, avoids comminuting rawhide
and employs the conventional method comprising rolling wet rawhide sheets and
drying. The resulting dried rawhide chew product is then basted with a
solution
comprising calcium. Such a process provides only a surface coating of calcium
which can be easily removed, for example by the licking of a dog. Upon
removal,
the calcium no longer imparts its benefits as a whitening agent and dental
hygiene
aid. It would therefore be desirable to prolong the benefits that calcium
imparts in
a non-comminuted rawhide chew product.
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SUMMARY OF THE INVENTION
It has now been discovered that impregnated calcium, preferably
precipitated calcium carbonate (herein referred to as PCC), may advantageously
replace titanium dioxide as a whitening agent for rawhide chew products.
Calcium has several desirable properties as a whitening agent compared to
titanium dioxide including: 1) readily coimnercially available forms of
calcium
are already food grade aaa.d do not incur any additional effort to remove
harmful
impurities; 2) calcium provides nutritive value while titanium dioxide does
not; 3)
calciuin has mild abrasive qualities thereby aiding dental hygiene.
Rather than a mere coating, the present invention provides for a chew
product which is impregnated with calcium. Calcium is contacted with wet
rawhide. Because wet rawhide is more porous than dried rawhide, the calcium
not only adlieres to the surface of the rawhide but enters its interior
cellular
structure. Therefore the benefits imparted by calcium are prolonged because
calcium which is impregnated beneath the rawhide surface is not easily removed
compared with calcium which is merely coated on the rawhide surface.
One aspect of the invention is a chew product comprising rawhide
impregnated with calcium thereby prolonging the imparted benefits of calcium
compared to a chew product having a relatively easily removable calcium
surface
coating. The calcium is preferably calcium carbonate. The rawhide is
preferably
rolled in a cylindrical shape and lcnotted on both ends thereof to simulate a
bone.
Another aspect of the invention is a method of impregnating calcium into
rawhide wherein the rawhide is soaked in a solution comprising calcium. The
calcium is preferably calcium carbonate, and more preferably a precipitated
calcium carbonate. The rawhide is allowed to soak for a sufficient amount of
time
to allow the rawhide to become porous and allowing the calcium to eiiter
interstitial spaces beneath the surface of the rawliide. This amount of time
is the
rawliide is soalced is preferably at least 15 minutes, more preferably at
least 30
minutes, and most preferably at least 60 minutes. The rawhide is then
optionally
rolled into a cyliiidrical shape and knotted at both ends thereof. The rawhide
is
then dried.
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DETAILED DESCRIPTION OF THE INVENTION
The calcium impregnated chew product of the invention is made by
soaking rawhide in a vat comprising water and calcium. A vat suitable for use
in
the invention may be any container wliich can liold liquid. Suitably, the vat
is
shaped lilce a drum or barrel and has an approximate volume from about 3 to 40
cubic meters.
Prior to calcium impregnation, it is preferable to subject the rawhide to a1i
initial soak. Rawhide sh.eets are loaded into a vat. Water is then added to
the vat
in an amount suitable for completely wetting the rawhide; preferably water is
added in an amount of about 100 weight of the rawhide in the vat. The vat is
sealed and is agitated back and forth and/or rotated lilce a washing macliine
for a
length of time suitable for completely wetting the rawhide and opening the
interstitial spaces thereof; typically the length of time is about 30 minutes.
After the initial soalc, the calcium impregnation may be performed by
feeding an amount of calcium into the vat after completion of agitation and/or
rotating. The amount of calcium added is an amount sufficient for the calciuin
to
enter the interstitial spaces beneath the rawhide surface; typically this
amount is
no more than about 2 weight percent of the rawhide in the vat, preferably no
more
than 1 weight percent, more preferably no more than about 0.5 weight percent,
and most preferably no more than about 0.2 weiglit percent of the rawhide in
the
vat.
In a preferred embodiment, the calcium impregnation is performed after
draining the vat of liquid from the initial soak wherein an amount of fresh
water is
fed into the vat, an amount of calcium is added to the vat, and the vat is
sealed and
agitated and/or rotated for a period of time. The fresh water is added in an
amount sufficient for the water to contact all of the surfaces of the rawhide
during
agitation and/or rotating and is preferably in an amount which allows at least
some of the calcium added to dissolve therein. Typically, the amount of fresh
water added is no more than 75 weight percent of the rawhide in the vat,
preferably no more than 50 weight percent, and most preferably no more than
about 25 weiglit percent of the rawllide in the vat. The amount of calciuin
added
is a.n amount sufficient for the calcium to enter the interstitial spaces
beneath the
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rawhide surface; typically this amount is no more than about 2 weight percent
of
the rawhide in the vat, preferably no more than 1 weight percent, more
preferably
no more than about 0.5 weight percent, and most preferably no more than about
0.2 weight percent of the rawhide in the vat. The vat is agitated and/or
rotated for
a sufficient amount of time for the liquid in the vat to contact all of the
surfaces of
the rawhide and allow the calcium to enter the interstitial spaces beneath the
rawhide surface; typically this amount of time is about 60 minutes.
The calcium used in the present invention is preferably calcium carbonate
having a mean particle size which facilitates its entry into the interstitial
spaces
beneath a rawhide surface. Preferably, the mean particle size is no more than
250
nanometers. More preferably, the mean particle size is no more than 200
nanometers. Even more preferably, the mean particle size is no more than about
100 nanometers. Most preferably, the mean particle size is no more than about
70
nanometers. In general, precipitated calcium carbonates would satisfy the
preferred parameters for mean particle size.
In general, precipitated calcium carbonate ("PCC") is derived from lime
and is made by hydrating high-calcium quiclclime, and then reacting the
resulting
slurry with carbon dioxide. The resulting product is particularly suitable for
the
present invention because it is extremely white and typically has a uniform
narrow
particle size distribution. PCC is available in numerous crystal morphologies
all
suitable for the present invention. However, morphologies which facilitate
entry
into the interstitial spaces beneath a rawhide surface are preferred. An
example of
a preferred morphology is rhombohedral. A PCC which satisfies the preferred
mean particle size and morphology of the present invention is SOCAL 31
commercially available from Solvay S.A. of Belgium.
The rawhide used in the present invention may advantageously be scrap
material obtained from a leather tanning manufacturing process wherein animal
hides are split into a top layer and a bottom layer. The top layer is
typically
processed to malce what is considered high quality leather while the bottom
layer
is considered waste material or scrap. The scrap may be used as the rawhide or
rawhide sheets specified by the invention.
In an embodiment of the invention, the rawhide is subjected to deliming,
degreasing, and bleaching. This embodiment is especially preferred if scrap
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material from a leather tanning process is used as the rawllide material for
the
invention.
Lime is used in a typical taniiing process to aid in the removal of hair from
the animal hide. If rawhide obtained from waste material of a tanning process
is
used, it is preferable to remove this lime with a deliming agent. During the
deliming process, rawhide is loaded into a vat, an a.inount of deliming agent
is fed
into the vat, the vat is sealed, and for a length of time the vat is agitated
and/or
rotated. The amount of deliming agent added is sufficient for removal of metal
species, such as calcium and iron, which are typically added to the rawhide in
a
tanning process. Preferably the amount of deliming agent added is no more than
about 5.0 weight percent of the rawhide in the vat, more preferably no more
than
about 2.5 weight percent, and most preferably no more than about 1.2 weight
percent of the rawhide in the vat. The length of time the vat is agitated
and/or
rotated is sufficient to allow the deliming agent to contact all the surfaces
of the
rawhide and is typically about 90 minutes. After agitation and/or rotating of
the
vat, it is preferable to drain the vat.
Deliming agents suitable for use by the invention are known in the art.
Typical deliming agents are coinpounds which chelate or otherwise bind with
metal species thereby facilitating their removal. Examples of deliming agents
useful in the present invention are (NH3)2SO4 and orga.nic acids have the
ability of
chelate metal species such as glycolic or lactic acid. One deliming agent
especially preferably for use in the present invention is GLYCLEAN PBL, a
mixture of glycolic and sulfuric acid, coinmercially available fiom E. I. du
Pont
Canada Company.
In a preferred embodiment of the invention, the rawhide is degreased to
remove appendant fat thereby making a healthier food product. During the
degreasing process, rawhide is loaded into a vat, an ainount of water is fed
into
the vat, an amount of degreasing agent is fed into the vat, the vat is sealed,
and for
a length of time the vat is agitated and/or rotated. The water is added in an
amount sufficient for the water to contact all of the surfaces of the rawhide
during
agitation and/or rotating and is preferably in an amount which allows all of
the
degreasing agent added to dissolve therein. The length of time the vat is
agitated
and/or rotated is sufficient to allow the degreasing agent to solubilize and
remove
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fat from the rawhide; typically this amount is no more than about 2 weight
percent
of the rawhide in the vat, preferably no more than 1 weight percent, more
preferably no more than about 0.5 weight percent, and most preferably no more
than about 0.2 weight percent of the rawhide in the vat. After agitation
and/or
rotating of the vat, it is preferable to drain the vat.
Any degreasing agent lcnown in the art for removing fat may be used in the
invention. Suitable degreasing agents include: strong alkali, such as sodium
or
potassium hydroxide; cleaning agents, such as surfactant(s), wetting agent(s),
detergent(s), chelating agent(s), phosphates, carbonates, sulfates, water
softening
agents, and the like. Combinations of wetting agents may also be suitable for
use
by the invention. One degreasing agent especially preferred for use in the
invention is BIOTEN MK 40, a nonylphenol ethoxylate surfactant, commercially
available from MK Quimica do Brasil Ltda. of Brazil.
In a preferred embodiment of the invention, the rawhide is bleached.
During the bleaching process, rawliide is loaded into a vat, and an amount of
bleaching agent is fed into the vat, the vat is sealed, and for a length of
time the
vat is agitated and/or rotated. The beaching agent is added in an amount
sufficient
to contact all of the surfaces of the rawhide during agitation and/or
rotating;
typically this amount is no more than about 2 weight percent of the rawhide in
the
vat, preferably no more than about 1 weight percent, more preferably no more
than about 0.50 weight percent, and most preferably no more than about 0.25
weiglit percent of the rawhide in the vat. The length of time the vat is
agitated
and/or rotated is sufficient to allow the bleaching agent to whiten the
rawhide a11d
is typically about 60 minutes. If more bleaching is preferred to yield a
whiter
rawhide, an additional cycle may be performed wherein the vat is held
stationary
(typically for about 7 minutes) allowing the rawhide to soak in the bleaching
agent and then subjected to additional time period (typically 60 minutes) of
agitation and/or rotating. This cycle may be repeated as several times to
obtain
the desired whitening of the rawhide. After the bleaching process the vat is
preferably drained.
Any bleaching agent lcnown in the art to remove color is suitable for use in
the present invention. Typical bleaching agents include oxidizing agents, such
as
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sodium hypochlorite or hydrogen peroxide. A preferred bleaching agent is 35
weight percent hydrogen peroxide.
In a preferred embodiment of the invention, calcium impregnation is
conveniently conducted by adding calcium during the bleaching process. In this
embodiment, calcium is added to the vat prior to the vat being drained from
the
bleaching process. The amount of calcium added is an amount sufficient for the
calcium to enter the interstitial spaces beneatll the rawhide surface;
typically this
amount is no more than about 2 weight percent of the rawliide in the vat,
preferably no more tllan 1 weight percent, more preferably no more than about
0.5
weight percent, and most preferably no more than about 0.2 weight percent of
the
rawhide in the vat.
The rawhide may be subjected to a process of bactericide addition. During
bactericide addition an amount of hydrochloric acid is preferably added to a
vat
containing rawhide, the vat is seal and agitated and/or rotated (typically
about 10
minutes), an amount of bactericide is added to the vat, the vat is sealed and
agitated and/or rotated (typically about 30 minutes). If desired an additional
cycle
may be performed wherein the vat is held stationary (typically for about
7 minutes) allowing the rawhide to soalc in the bactericide solution and then
subjected to additional time period (typically 40 minutes) of agitation and/or
rotating. After the bactericide addition, the vat is preferably drained and,
to
maintain the efficacy of the bactericide, the resulting rawhide is preferably
not
subjected or any fiuther rinsing, deliming, bleaching, or calciuin
impregnation.
Any bactericide known in the art may be used in the present invention. A
preferable class of bactericide is quaternary alkyl-ammoniuins also known as
"quats."
After the rawhide is treated in accordance witli the forgoing processes, it is
dried in an oven at a temperature not exceeding 60 degrees Celsius. Prior to
drying the rawhide may be rolled into a cylindrical shape and tied at both
ends to
simulate a bone.
EXAMPLES
The following is an illustrative example and is not intended to unduly limit
the claimed invention.
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Initial Rinse
About, 1000 lcilograms of scrap hide was placed in a drum container
having an approximate volume of 5000 liters. At ambient temperature, water was
added to the druin in an amount of 100 percent by weight of the scrap hide.
The
drum was sealed and rotated on its side for about 30 minutes and then the drum
was drained of liquid. The pH of the liquid was 12.50. All pH measurements
were performed with a pH meter cominercially available from Hach Company of
Loveland, Colorado, USA.
Primary De rg easing
After the initial rinse, water was added, at ambient temperature, to the
drum in an amount of about 50 percent by weight of the scrap hide.
Additionally,
a degreaser was added, at ainbient temperature, to the druin in an amount of
about
0.2 percent by weight of the scrap hide. The degreaser used was BIOTEN MK
40, a nonylphenol ethoxylate surfactant, commercially available from MK
Quimica do Brasil Ltda. of Brazil. The drum was sealed and rotated on its side
for about 30 minutes and then the drum was drained of liquid. The pH of the
liquid was 12.02.
Primary De rg easing Rinse
After primary degreasing, water was added, at ambient temperature, to the
drum in an amount of about 50 percent by weight of the scrap hide. The drum
was sealed and rotated on its side for about 30 minutes and then the drum was
drained of liquid. The pH of the liquid was 11.89.
Detiming
After the primary degreasing rinse, a deliming agent was added, at
ambient temperature, to the drum in an amount of about 1.2 percent by weight
of
the scrap hide. The deliming agent used was GLYCLEAN PBL, a mixture of
glycolic and sulfuric acid, commercially available from E. I. du Pont Canada
Company. The drum was sealed and rotated on its side for about 90 minutes and
then the druin was drained of liquid. The pH of the liquid was 9.28.
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Secondary Degreasing
After deliming, water was added, at ambient temperature, to the drum in
an amount of about 50 percent by weight of the scrap hide. Additionally, a
degreaser was added, at ambient temperature, to the drum in an amount of about
0.2 percent by weight of the scrap hide. The degreaser used was BIOTEN MK
40. The drtun was sealed and rotated on its side for about 30 minutes and then
the
drum was drained of liquid. The pH of the liquid was 9.65.
Secondary DegreasingRinse
After primary degreasing, water was added, at ambient temperature, to the
drum in an amount of about 80 percent by weight of the scrap hide. The drum
was sealed and rotated on its side for about 10 minutes and then the drum was
drained of liquid. The pH of the liquid was 9.66.
Bleaching/Whitening
After the secondary degreasing rinse, hydrogen peroxide was added, at
ambient temperature, to the drum in an amount of about 2.5 percent by weight
of
the scrap hide. The hydrogen peroxide used comprised 35 wt. % hydrogen
peroxide and the remainder water. The drum was sealed and subjected to three
cycles of being rotated for 60 minutes and stopped for about 20 minutes. After
the three cycles, the pH of the liquid in the drum was 9.44. Next, a
precipitated
calcium carbonate was added, at ambient temperature, to the drum in an amount
of about 0.75 percent by weight of the scrap hide. The calcium carbonate was
SOCAL 31 available from Solvay S.A. of Belgium. The druin was sealed and
rotated on its side for about 60 minutes and then the drum was drained of
liquid.
The pH of the liquid was 9.50.
Bleaching/Whitening Rinse
After bleaching/wliitening, water was added, at ambient temperature, to
the drum in an a.inount of about 80 percent by weight of the scrap hide. The
drum
was sealed and rotated on its side for about 40 minutes and then the drum was
drained of liquid. The pH of the liquid was 9.55.
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Bactericide Addition
After the bleaching/whitening rinse, 35 weiglit percent hydrochloric acid
was added, at ainbient temperature, to the drum in an amount of about 0.2
weight
percent of the scrap hide. The drum was sealed and rated on its side for about
10
minutes after which the pH of the liquid in lie drum was 5.80. Next, a
bactericide
was added, at ambient temperature, to the drum in an ainount of about 0.04
percent by weight of the scrap hide. The bactericide used was BIODERM BAC
commercially available from MI,'- Quimica do Brasil Ltda. of Brazil. The drum
was sealed, rotated for about 30 minutes, stopped for about 7 minutes, rotated
for
about 40 minutes, and then drained of liquid. The pH of the liquid was 8.08.
Rolling, K notin , and Drying
After the bactericide addition the scrap hides are removed from the drum
and made into cylindrical shapes by cutting and rolling the scrap hides. Knots
are
made on both sides of the cylindrical scrap hides which are then dried in an
oven
at a temperature of at about 30 degrees Celsius for the first 24 hours and at
about
57 degrees Celsius fore 3 days.
