CA2618372A1 - Chew product impregnated with calcium - Google Patents

Abstract

It has now been discovered that impregnated calcium, preferably precipitated calcium carbonate, 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 commercially available forms of calcium are already food grade and do not incur any additional effort to remove harmful impurities; 2) calcium provides nutritive value while titanium dioxide does not; 3) calcium 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. Therefore the desirable properties 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.

Description

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.

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.

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 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 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 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 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 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 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.

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.

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.

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 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.

Claims (14)

1. A method for making a chew product from rawhide comprising the steps of impregnating calcium in said rawhide by soaking said rawhide in a solution comprising calcium and subsequently drying.

2. The method of claim 1 wherein said rawhide is soaked in said solution for at least 15 minutes.

3. The method of claim 1 wherein the calcium is calcium carbonate having a mean particle size of up to about 250 nanometers.

4. The method of claim 1 wherein the calcium is calcium carbonate having a rhombohedral morphology.

5. The method of claim 1 wherein the solution comprising calcium further comprises a bleaching agent.

6. The method of claim 1 wherein, prior to drying, the rawhide is soaked in a vat comprising at least one degreasing agent, deliming agent, bleaching agent, or bactericide.

7. The method of claim 1 wherein, prior to drying, the rawhide is rolled and optionally knotted at least one end thereof.

8. A method for making a chew product from rawhide comprising the steps of:
a) degreasing said rawhide by soaking it in a vat comprising at least one degreasing agent b) deliming said rawhide by soaking it in a vat comprising at least one deliming agent c) bleaching said rawhide by soaking it in a vat comprising at least one bleaching agent d) impregnating calcium by soaking said rawhide in a vat comprising a solution of calcium, and e) drying said rawhide;

wherein drying is preformed subsequent to degreasing, deliming, bleaching, and calcium impregnation.

9. The method of claim 11 the calcium is calcium carbonate.

10. The method of claim 11 wherein impregnating calcium occurs immediately after bleaching wherein calcium is added to the vat comprising the bleaching agent.

11. The method of claim 11 wherein the rawhide is soaked in a vat comprising at least one bactericide after steps a-d but prior to step e).

12. A chew product comprising a sheet of rawhide impregnated with calcium.

13. The product of claim 16 wherein the calcium is calcium carbonate.

14. The product of claim 16 further comprising a bactericide.