Abstract:
Process for preparing baked dog biscuits having a coating containing at least one inorganic pyrophosphate, comprising: 
     (a) subjecting unbaked dog biscuit dough to a liquefied coating material containing at least one inorganic pyrophosphate, thereby, forming a coating of such liquefied coating material on the dog biscuit; and 
     (b) baking the unbaked dog biscuit dough pieces having a coating containing said at least one inorganic pyrophosphate. The baked, coated dog biscuits are chewed and/or eaten by dogs, with the result that tartar accumulation on their teeth is reduced or prevented.

Description:
BACKGROUND OF THE ART 
     1. Field Of The Invention 
     The invention relates to dog biscuits having a coating containing an anti-tartar agent. The invention also relates to a process of preparing such dog biscuits. The invention further relates to a process of preparing tartar on dogs&#39; teeth by the dog chewing on such dog biscuits. 
     2. Background Art 
     Dental calculus, or tartar as it is sometimes called, is a deposit which forms on the surfaces of the teeth at the gingival margin. Supragingival calculus appears principally in the areas near the orifices of the salivary ducts; e.g., on the lingual surfaces of the lower anterior teeth and on the buccal surfaces of the upper first and second molars, and on the distal surfaces of the posterior molars. Mature calculus consists of an inorganic portion which is largely calcium phosphate arranged in a hydroxylapatite crystal lattice structure similar to bone, enamel and dentine. An organic portion is also present and consists of desquamated epithelial cells, leukocytes, salivary sediment, food debris and various types of microorganisms. As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agency. In addition to being unsightly and undesirable from an aesthetic standpoint, the mature calculus deposits are constant sources of irritation of the gingiva and thereby are a contributing factor to gingivitis and other diseases of the supporting structures of the teeth, the irritation decreasing the resistance of tissues to endogeneous and exogenous organisms. 
     A wide variety of chemical and biological agents have been suggested in the art to retard calculus formation or to remove calculus after it is formed in humans. Mechanical removal of this material is done routinely in humans. 
     Chemical Technology: An Encyclopedic Treatment, Vol. V, Barnes &amp; Noble Books, (1972), pages 392 to 406, is a general disclosure of types of leathers and their uses, and the tanning of leather. Arnold, John R., &#34;Hides And Skins&#34;, (1925), pages 6, 7, 252, 253, 310 and 311, is a general disclosure on raw and tanned hides and skins. 
     U.S. Patent No. 4,145,447 discloses a hard, unit-integral, unitized, self-contained, compact, chew-resistant nutritionally balanced animal food product having a density of at least about 0.5 oz./in.3, a final water content of at least about 5.5 percent by weight, and a breaking force of at least about 60 psi. The animal food contains, for example, dried meals, dried fish, dried dairy products, fish meal, fish flour, cereals, flours, carbohydrates, dried fruits, etc., with or without food additives or supplements such as vitamins, minerals, medicinals, etc., for example chemicals, enzymes, etc., capable of removing plaque or tartar from the animals&#39;s teeth, etc. 
     U.S. Pat. No. 4,044,158 discloses the use of tetrasodium pyrophosphate as a chelating agent in semi-moist pet foods. The neutral chelating agent is used in a semi-moist pet food having a pH of from 6.3 to 7.2 and which comprises about 5 to about 50 percent by weight meat or meat by-products, about 15 to about 50 percent moisture, and about 1 percent to about 26 percent by weight vegetable protein. The vegetable protein, an amylaceous material, and the chelating agent, it is taught, forms a composition which replaces part of the caseinate binder customarily present in a semi-moist pet food. No mention is made of any anti-tartar effectiveness of the pet food. 
     U.S. Pat. No. 4,215,149 discloses a process for maintaining the palatability of a pet food by coating particulates having a moisture content of less than 15 percent with fat and then with a monoalkali metal or monoalkaline earth metal salt of phosphoric acid to make the food more palatable to cats. Exemplary salts are monosodium phosphate and monocalcium phosphate. 
     U.S. Pat. No. 3,639,569 discloses the use of a tris(phosphonoalkyl)amine in a dentifrice composition with a dentifrice abrasive selected from the group consisting of beta-phase calcium pyrophosphate, particulate thermosetting polymerized resin, alumina, sodium metaphosphate, and mixture thereof, or in a mouthwash composition, or in a chewing gum composition or dental prophylaxis paste composition. The patent discloses that the use of inorganic pyrophosphates as anti-calculus agents in oral compositions has the problem of hydrolysis in aqueous products and loss of activity prior to the termination of the normal shelf-life of such products. The patent also teaches that calculus inhibition by chelation of calcium ion may seriously damage tooth structure by decalcification. 
     U.S. Pat. No. 3,957,964 discloses microcapsules containing essential oils of mint flavor in a dentifrice adapted to release a plural flavor-burst signaling the onset of and the completion of a toothbrushing operation. The dentifrice may be a toothpaste having dicalcium phosphate as a polishing agent. 
     U.S. Pat. No. 3,959,458 discloses the use of from about 0.2 to about 8 percent by weight of an orally acceptable monofluorophosphate with an anticalculus agent which is a condensation product of ammonia and phosphorus pentoxide or with a polyphosphonate in an oral composition. The oral composition may further contain a calcium pyrophosphate abrasive. The patent teaches that sodium or calcium monofluorophosphate, when used in combination with the anticalculus agents, exhibit no detectable damage to silicate fillings in the mouth whereas other anticaries agents, such as sodium fluoride, do exhibit damage. It is also taught that below about pH 5.0 some of the anticalculus agents can damage dental enamel. 
     U.S. Pat. No. 4,314,990 discloses the use of a phosphate buffering agent, which provides phosphate ions to maintain the pH of a slurry in the range of about 6.8 to 8.0, in a toothpaste composition which comprises 6 to 45 percent of a silica dental abrasive, from about 0.01 to 3 percent of a fluoride ion source, from about 10 to 45 percent of water, and about 30 to 70 percent of a humectant. 
     U.S. Pat. No. 4,323,551 discloses the use of a tetra-alkali metal pyrophosphate salt to provide from about 0.5 to 5 percent of the P207 species in a mouthwash composition comprising 0.02 to 0.2 percent of a quaternary ammonium compound, and a carrier liquid wherein the pH is adjusted to about 7.0 to 9.5 with a mineral or organic acid. 
     U.S. Pat. No. 4,421,527 discloses the use of a precipitated amorphous silicon dioxide prepared by acidulation in an abrasive composition in a toothpaste that contains fluoride. Phosphoric acid is disclosed as an acidulant. Soluble phosphates, such as the pyrophosphates, are taught as improving fluoride pellicle penetration. 
     U.S. Pat. No. 4,515,770 discloses a process wherein a soluble source of phosphate ions or a soluble source of calcium ions is uniformally distributed through sucrose in crystalline form as a result of dissolution of the sucrose and soluble source of calcium or phosphate ions in water followed by evaporation of the water solvent. It is taught PG,7 that it is of substantial importance that the calcium or phosphate ion source be as rapidly soluble in saliva as the sugar so that the protective ions will migrate to salivary retention areas as rapidly as the sugar. A material, it is taught, which is cariogenic by virtue of directly or indirectly participating in the lowering of pH in salivary retention areas is rendered non-cariogenic by treatment to incorporate enough of either a calcium or phosphate ion source to keep the acidic medium from dissolving the tooth enamel. It is also disclosed that systematically administered phosphates are said to differ in cariostatic activity depending on the type of anion (cyclictrimeta-, hexameta-, ortho-, and pyrophosphate, increasing in effectivness in that order). It is further taught that these developments have unfortunately resulted in only minor advances in prevention of carious degradation of teeth because none of the &#34;remineralization&#34; processes have been shown to be consistently effective. 
     U.S. Pat. No. 4,515,772 discloses the use of from about 10 to about 70 percent of a dental abrasive selected from the group consisting of insoluble metaphosphates, alumina, thermosetting polymerized resins, and silica from about 50 ppm to about 3,500 ppm of fluoride ions from a fluoride ion source, and an amount of a pyrophosphate salt selected from the group consisting of dialkali metal and mixtures of dialkali metal and tetraalkali metal pyrophosphate salts sufficient to provide at least 1.5 percent P 2  O 7   -4 . The pyrophosphate ion is provided by a mixture of disodium pyrophosphate and tetrasodium pyrophosphate. The fluoride ion source is disclosed as an essential component. The upper limits on the sodium pyrophosphate salts are determined by solubility considerations, while the tetrapotassium level is established for taste reasons. It is further taught that surprisingly mixtures of certain pyrophosphate salts can provide a safe and effective anti-calculus product while also not presenting difficult formulation problems. 
     U.S. Pat. No. 4,532,124 discloses the use of a plaque mineralizing aqueous solution comprising urea, a fluoride salt, a water-soluble calcium salt, and a water-soluble phosphate salt in the mineralization of dental plaque. It is disclosed that high plaque calcium and inorganic phosphate levels will lower the `critical pH`, the pH which plaque must reach before it becomes unsaturated with respect to biological apatite, and enamel dissolution commences. The urea is metabolized by bacteria to produce alkali in plaque. Aspartame and amino acids may be substituted for urea. 
     U.S. Pat. No. 4,540,584 discloses the use of coral sand as an effective component in a mineral supplement in an amount sufficient to provide calcium carbonate as a mineral supplemental for humans, such coral sand also containing PO 4 . The composition, it is taught, is useful for replenishing calcium and phosphorous, as well as other minerals. Acidic foods tend to result in decayed teeth and bone fractures because of calcium poverty. 
     U.S. Pat. No. 3,567,459 discloses conversion of a hot melt of sugar having a moisture content less than 5 percent to a dough-like bone-forming composition by incorporation of nutritional fillers, fatty flavoring materials, and fat-absorbing farinaceous materials. The composition is formed and cooled. The patent teaches mastication of bones provides teeth cleaning benefits stemming from abrasion and other contacts of bone fragments. 
     U.S. Pat. No. 3,701,830 discloses the use of a neutral protease enzyme for removing plaque from and preventing the formation of calculus on the teeth of dogs wherein the neutral protease is obtained by fermentation with a strain of Bacillus suptilis or Bacillus sterothermophilus. 
     U.S. Pat. No. 3,882,257 discloses a process where 75 percent by weight of bones is admixed with 23.5 percent by weight of animal by-products, and the mixture is bound with salt in the preparation of a pet food having about 40 percent natural animal protein. The product enables a dog to exercise his jaws and gums to remove tartar from teeth. 
     U.S. Pat. No. 3,899,607 discloses a dough mixture which is: worked and shaped at a temperature of 170° to 220° F to form a simulated bone having a structural matrix; or cooked, dried to a moisture content of between 5 and 12 percent by weight, ground and mixed with a dextrin adhesive to form a simulated bone having a structural matrix. 
     U.S. Pat. No. 4,364,925 discloses an enzyme for removing plaque and/or tartar from the teeth is included in a chew-resistant layer of an integral chew-resistant multi-layer animal food system having a structure supporting fibers. A cracker containing protease or amylase. U.S. Pat. Nos. 3,194,738 and 3,686,393 also relate to the use of enzymes for inhibiting plaque. 
     U.S. Pat. No. 3,488,419 discloses the use of a polyphosphonate or salt thereof in an oral composition or toothpaste. The patent teaches that inorganic polyphosphates, such as pyrophosphates, hydrolyze in aqueous products and do not remain in active form throughout the normal shelf-life of such products. The patent also teaches that calculus inhibition by chelation of calcium ion may seriously damage tooth structure by decalcification. 
     U.S. Pat. No. 3,535,420 discloses the use of a cyclic tetraphosphonic acid as an anti-calculus agent in an oral composition. The patent teaches that inorganic polyphosphates, such as pyrophosphates, hydrolyze in aqueous products and do not remain in active form throughout the normal shelf-life of such products. It is also taught that although certain of the art-disclosed chelators are purportedly safe for use on dental enamel, the chemical similarity of calculus to the tooth structure limits the usefulness of the chelation approach because the more effective chelators can seriously damage the tooth structure by decalcification. The cyclic tetraphosphonates are calcium sequestrants, but they retard calculus formation by a mechanism that is believed to involve the inhibition of hydroxylapatite crystal growth rather than calcium sequestering. 
     U.S. Pat. No. 3,686,393 discloses the use of a dextranase used to eliminate dental plaque formation. 
     U.S. Pat. No. 3,956,479 discloses the use of a quaternary ammonium compound having a carbamate, or a thiocarbamate, or a dithiocarbamate, or a carbamide group in an oral preparation. The compounds, it is taught, are effective in reducing caries and inhibiting formation of oral calculus. 
     U.S. Pat. No. 4,003,971 discloses the use of a dentifrice component in the production of dentifrice speckles. Antimicrobial agents for incorporation into oral dentifrice formulations may be effective by reducing dental plaque or inhibiting the formation of dental calculus. 
     U.S. Pat. No. 4,254,101 discloses the sue of from about 6 to 45 percent of a silica dental abrasive, from about 30 to 70 percent of a humectant, and from about 0.03 to 1.0 percent of a carboxyvinyl polymer in a toothpaste composition. The use of optional anticalculus agents, in amounts of from about 0.01 to 2.5 percent by weight of the toothpaste composition are taught. 
     U.S. Pat. No. 4,472,373 discloses the use of a pyridium salt as an anti-plaque agent in a flavored alcoholic carrier. Phosphates, such as calcium pyrophosphate, are disclosed as dentifrice abrasives. 
     U.S. Pat. No. 4,153,732 discloses the use of at least one soluble aluminum ion containing salt with adipic acid, ascorbic acid, or mixtures thereof as a cariostatic additive for comestibles. The patent teaches that calcium pyrophosphate and insoluble sodium metaphosphate abrasives coact with aluminum fluoride in dentifrice compositions. 
     U.S. Pat. No. 4,627,977 discloses an oral composition, such as, a toothpaste (including gel or cream), mouthwash, lozenge, chewing gum or tooth powder, containing a calculus-inhibiting amount of a linear molecularly dehydrated polyphosphate salt (e.g., a water-soluble alkali metal pyrophosphate) to inhibit enzymatic hydrolysis of said polyphosphate salt in saliva, a combination of a fluoride ion-providing source and a synthetic linear polymeric polycarboxylate. See also British Published Patent Application No. 2,180,157. 
     U.S. Pat. No. 4,678,662 discloses calcium carbonate particles coated with at least one pyrophosphate derivative, such as, disodium dihydrogen pyrophosphate and tetrasodium pyrophosphate. 
     European Published Patent Application No. 0236920 discloses a dentifrice comprising essentially insoluble calcium pyrophosphate as an abrasive and a clinically effective amount of soluble pyrophosphate, such as, tetrasodium pyrophosphate, or tripolyphosphate as an anticalculus agent. 
     U.S. Pat. No. 4,684,518 discloses a process for reducing the incidence of calculus on dental enamel. The enamel surfaces in the mouth are contacted with a composition comprising a soluble pyrophosphate source capable of providing at least 1.5 percent of P 2   O   7  and from about 50 to about 3500 ppm of fluorine. 
     U.S. Pat. No. 4,722,461 discloses an oral composition in the form of a mouthwash or liquid dentifrice comprising: an amount of a fluoride ion source sufficient to supply from about 50 ppm to about 3500 ppm of fluoride ions; an amount of a pyrophosphate salt selected from the group consisting of dialkali metal and mixtures of dialkali metal and tetraalkali metal pyrophosphate salts sufficient to provide at least 1.5 percent of P 2  O 7   -4  ; and water. The pH of the composition is from about 6.0 to about 10.0. Calcium pyrophosphate is termed to be an abrasive. See European Published Patent Application No. 0097476. 
     British Published Patent Application No. 2,201,593 discloses an oral composition in the form of a toothpaste effective in reducing calculus comprising: a safe and effective amount of a soluble pyrophosphate salt or mixture of the salts; from about 5 to about 60 percent of a suitable toothpaste abrasive; an amount of a fluoride ion source sufficient to provide from about 50 ppm to about 3500 ppm fluoride; from about 5 to about 60 percent of humectant selected from the group consisting of sorbitol, glycerine, polyethylene glycols, mineral oil, and mixtures thereof; from about 0.3 to about 5 percent of a surfactant selected from the group consisting of alkyl sulfate surfactants, ethoxylated alkyl sulfate surfactants and mixtures thereof; and water. The composition has a pH of from about 6 to about 10, is substantially free of polyethylene glycols having fewer than six ethoxy units and short chain monohydric alcohols and has potassium ions present at a level of from about 0.5 to about 7 percent. The soluble pyrophosphate salt can be, for example tetrapotassium pyrophosphate, tetrasodium pyrophosphate, sodium acid pyrophosphate and mixtures thereof. 
     U.S. Pat. No. 4,806,340 discloses an oral dentifrice composition such as a toothpaste, dental gel, toothpowder, dental tablet or lozenge containing as anticalculus agent about 4.3 to about 7 percent of alkali metal pyrophosphates comprising at least 4.3 percent of tetrapotassium pyrophosphate alone or admixed with up to 2.7 percent of tetrasodium pyrophosphate, and as inhibitors against enzymatic hydrolysis of such agent in saliva, a fluoride and preferably up to about 3 percent of a synthetic anionic polymeric polycarboxylate. The composition is used in a program of oral hygiene and/or for inhibiting dental calculus. It is known that saliva contains acid phosphatase, alkaline phosphatase and pyrophosphatase enzymes. It is considered that any one of the three enzymes may adversely affect pyrophosphates as an inhibitor of hydroxyapatite formation and calculus. It is accordingly apparent that an anticalculus pyrophosphate dentifrice composition, should inhibit, reduce or nullify the destructive activity of all three salivary enzymes. See also British Published Patent Application No. 2,182,244. 
     Australian Published Patent Application No. 168071 discloses a dialkali metal-alkaline earth metal pyrophosphate containing about 1 to about 5 percent by weight of chemically combined fluorine. The composition is a dentifrice base. The method of producing the fluorinated dialkali metal-alkaline earth metal pyrophosphate, which comprises reacting together, in the presence of an aqueous medium, a water-soluble metal fluoride, an alkali metal pyrophosphate (such as, tetrasodium pyrophosphate), and a water soluble alkaline earth metal salt. The reactants being employed in the proportions required to yield a dialkali metal-alkaline earth metal pyrophosphate containing about 1 to about 5 percent by weight of chemically combined fluorine. 
     British Patent No. 777,556 discloses a dentifrice composition which contains a fluoride compound which releases fluoride ions in water, a calcium polyphosphate polishing agent, and a calcium ion suppression agent to maintain the effect of the fluoride upon ageing. 
     BROAD DESCRIPTION OF THE INVENTION 
     An object of the invention is to provide dog biscuit having a coating containing at least one pyrophosphate. Another object of the invention is to provide a process for preparing dog biscuits, having a coating containing at least one pyrophosphate. Another object of the invention is to provide a process for the prevention of tartar accumulation on the teeth of dogs. A further object of the invention is to provide a process for the prevention of tartar accumulation on the teeth of dogs by the chewing and eating of dog biscuits having a coating containing at least one pyrophosphate by the dogs. 
     Other objects and advantages of the invention are set out herein or are obvious herefrom to one skilled in the art. 
     The objects and advantages of the invention are achieved by the compositions and process of the invention. 
     The invention includes a process for preparing dog biscuit dough having a coating containing at least one inorganic pyrophosphate compound, which includes preparing a dog biscuit dough, forming the dog biscuit dough into pieces, subjecting the dog biscuit dough pieces to a liquefied coating material having at least one inorganic pyrophosphate, thereby forming a coating of such liquefied coating material on the dog biscuit dough pieces, and baking (and optionally drying) the dog biscuit dough pieces having a coating containing at least one inorganic pyrophosphate. The inorganic pyrophosphate reduces the accumulation of tartar on the teeth of dogs. 
     Tartar is an incrustation on the teeth consisting of salivary secretion, food residue and various salts, such as, calcium carbonate or phosphate. Tartar is also termed dental calculus. 
     Caries are cavities or decay of the teeth which begins at the surface of the tooth and may progress through the dentine into the pulp cavity. It is believed that the action of microorganisms in the mouth on ingested sugars and carbohydrates produces acids that eat away the enamel. By preventing the formation of calculus or tartar, the invention formulation is in effect an anti-cariogenic agent. 
     Preferably the dry dough ingredients are mixed, then water is added and the mixing continued, and finally the fat (tallow) is added and thoroughly mixed in. The dog biscuits can be made from any suitable dough. In one advantageous embodiment, a bone-shaped canine biscuit is provided which is baked from a dough comprising wheat flour, wheat meal, soybean meal, meat and bone meals, animal fat and water. The baked, coated biscuit has an overall moisture content of 13 weight percent or less. 
     The coating on the dog biscuit dough preferably contains about 0.1 to about 10 weight percent of the at least one inorganic pyrophosphate compound, and most preferably about 0.5 to about 5 weight percent of said at least one inorganic pyrophosphate compound. The preferred inorganic pyrophosphate salt(s) is an alkali metal pyrophosphate. While the preferred alkali metal pyrophosphate is tetrasodium pyrophosphate, most preferably the dog biscuit dough contains a combination of trisodium monoacid pyrophosphate and tetrapotassium pyrophosphate (or tetrasodium pyrophosphate). 
     The invention also involves unbaked dog biscuits which have a coating which contains at least one inorganic pyrophosphate. The dog biscuit pieces preferably are bone shaped. The unbaked dog biscuits preferably have a moisture content usually in the range of about 25 to about 40 weight percent, preferably about 33 to about 35 weight percent. 
     The invention also involves a process for preparing baked dog biscuits which have a baked coating containing at least one inorganic pyrophosphate. The process includes: 
     (a) placing a coating, balanced and which contains the at least one inorganic pyrophosphate, onto unbaked dog biscuit dough pieces comprising unbaked dog biscuits; and 
     (b) baking the coated, unbaked dog biscuits. 
     The baked dog biscuits can be dried, if necessary, to obtain the desired moisture level. The baked dog biscuits should have a moisture content of 13 weight percent or less, advantageously between 5 and 13 weight percent, and preferably between about 8 and about 12 weight percent. 
     The invention product is baked so that it comprises a baked dog biscuit which has a coating containing at least one inorganic pyrophosphate. 
     The invention further involves baked, coated dog biscuits, such coating containing at least one inorganic pyrophosphate. The ingredients, ratios, ranges, etc., for the invention dog biscuit dough and coating applies to the invention baked, coated dog biscuits, except as otherwise noted herein. 
     The invention product (including coating) should be slightly acid to neutral. 
     The inorganic pyrophosphates are anti-tartar, anti-plaque or anti-calculus agents. The invention product exhibits anti-tartar properties over its normal shelf life. The invention product does not adversely affect canine tooth enamel. 
     The invention further involves a process for the prevention or reduction of tartar accumulation on the teeth of dogs. The process includes the chewing and/or eating of the invention baked, coated dog biscuits by the dogs. 
     The invention biscuits, when eaten and chewed by dogs, cleans teeth surfaces, removes tartar (by mechanical action), and exercises and massages the gums. The pyrophoshate in the coating of the invention biscuits prevents or reduces the formation of tartar on the dog&#39;s teeth. The pyrophosphate, in the levels involved, does not adversely affect the gastrointestinal system or the health of the dogs. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As used herein, all parts, percentages, ratios and proportions are on a weight basis unless otherwise stated herein or otherwise obvious herefrom to one skilled in the art. As used herein, all temperatures are in degrees Fahrenheit unless otherwise stated herein or otherwise obvious herefrom to one skilled in the art. 
     The dog biscuits can be made from any suitable dough, which is modified as described herein to provide nutritionally-balanced dog biscuits containing pyrophosphate. 
     Any suitable dough comprising at least one flour, meal, fat and water can be employed for the coated product. For instance, when the desired product is a canine biscuit, a conventional dough for dog biscuits can be used, optionally containing discrete particles of meat and/or meat byproducts or farinaceous material. Such doughs typically contain fat solids. Examples of suitable doughs for the production of hard dog biscuits are disclosed in U.S. Pat. No. 4,454,163, and suitable doughs for the production of soft dog biscuits (containing humectant to control water activity) are disclosed in U.S. Pat. No. 4,454,164. The pertinent portions of U.S. Pat. Nos. 4,454,163 and 4,454,164 are incorporated herein by reference. Particulate proteinaceous particles, such as particles of meat, texturized vegetable protein and/or meat byproducts can be incorporated to add flavor to the biscuits and texturize the surface. Particulate farinaceous materials such as bran particles can also be employed to texturize the surface of the biscuits and to provide other useful properties to the product. A dough found to produce biscuits highly palatable to dogs includes suitable proportions of wheat flour, wheat meal, soybean meal, meat and bone meal, animal fat and natural flavors in admixture with water. The meal used in the doughs suitable for production of biscuits useful in the invention can comprise meat and/or bone and/or vegetable matter including farinaceous materials, materials prepared from legumes such as beans and peas, tuberous materials such as potato meal, and the like. The meals can be finely or coarsely ground as desired for the texture. Flours made from any suitable farinaceous material can be used. 
     The doughs generally have a water activity of about 0.90 and above upon completion of mixing of the dough ingredients. A suitable dough contains farinaceous material, an edible oil, an antioxidant, an antimycotic, salt, animal fat, added vitamins and minerals, such as those disclosed in U.S. Pat. No. 4,229,485, column 5, lines 7 to 57, which is incorporated herein by reference. The compositions of the invention also preferably contain at least one animal-derived proteinaceous meal such as meat meal, bone meal, and fish meal. A good biscuit dough for producing the biscuits of the invention contains about 50 to 60 percent by weight wheat flour, about 5 to 10 percent by weight soybean meal, about 3 to 10 percent by weight meat and bone meal, about 1 to 5 percent wheat meal, about 1 to 5 percent animal fat preserved with BHA, about 20 to 30 percent by weight water, and about 2 to 5 percent by weight of natural flavors, vitamin and mineral preblend, and acidulant. 
     The dough can also contain suitable surfactants or emulsifying agents, e.g., which are best used in minor amounts. 
     The dog biscuit dough can be mixed using any suitable or conventional equipment. For example, the mixing can be at 20 to 100 rpm. For example, a dry blending step can be done typically at room temperature for a period of time of about 3 minutes to about 10 minutes. The dry-blended mixture can then be mixed with the hot water to form a first stage dough. The water which can be admixed with the dry-blended mixture is typically at a temperature of about 65° to about 150° F. The hot water can be added, with mixing, over a period of time of about 3 minutes to about 5 minutes to form the first stage dough. Then, the fat portion of the biscuit dough can be admixed with the first stage dough to form the final stage dough. The fat portion can be added at a temperature at which it is at least fluid, typically at about 100° to about 150° F. The fat portion can be mixed for a period of time which is sufficient to form a dough whose homogeneity is visually apparent. A typically final mixing time is about 3 to about 5 minutes. 
     Formation of the dough is usually achieved at about atmospheric pressure with mixing of the components being conveniently achieved in an upright sigma blade mixer or other bakery-type mixers. The various ingredients can be added over a period of time or in a one-shot manner according to the above order of addition. However, melted fat and water can be added simultaneously and mixed from 6 to 10 minutes. 
     The dog biscuits are formed in any conventional or suitable manner, such as, by extrusion, stamping, cutting or molding. Any suitable dog biscuit shapes can be used, such as, a bone-shaped canine biscuit. For many products, such as, the bone-shaped canine biscuits of the invention, a rotary molding system is preferred because it permits the rapid forming of dough pieces with good control over their shape, form and surface characteristics. Docker holes are preferbly formed in the dough piece during molding to facilitate the escape of moisture during baking. 
     The dough can be then formed into pieces by machining on a rotary molder with specific die shapes. The dough can also be formed into pieces by sheeting followed by either a vertical or rotary cutter or by a rotary molder. Suitable die and cutter shapes are those which result in a round, square, triangular, T-bone or chop-shaped biscuit product and the like. The forming is achieved at conventional temperatures of ambient to 110° F. and pressures of less than 75 p.s.i. (gauge), used with a rotary molder, a vertical cutter or rotary cutter. 
     The solvent used in the coating is preferably water, but other non-toxic, edible solvents, such as, ethanol or ethanol/water, can be used. The problem of the necessity of solvent removal from the coated dough due to toxicity is to be avoided in most cases. If a mixture of ethanol and water is used, the amount of ethanol in the mixture is generally about 5 to about 60 percent, preferably about 5 to about 25 percent. When one or more of the inorganic pyrophosphates is not water soluble, it may be ethanol soluble. 
     The invention includes the use of at least one inorganic pyrophosphate. Preferably the inorganic pyrophosphates are water soluble. A mixture of inorganic pyrophosphates can be used to provide a desired pH. The use of a water insoluble inorganic pyrophosphate, by itself or in a mixture, (along with the other water insoluble ingredients) results in a slurry. The use of very fine particles of a water insoluble inorganic pyrophosphate provides better suspension in the coating formulation. 
     The inorganic pyrophosphates are preferably alkali metal pyrophosphates. The preferred alkali metal pyrophosphate is tetrasodium pyrophosphate and tetrapotassium pyrophosphate. An example of useful tetraalkali metal pyrophosphates is tetralithium pyrophosphates. Alkaline earth metal pyrophosphates are also useful, but they are generally insoluble in water. Preferably the inorganic pyrophosphates are soluble in water. 
     The formula M n+2  P n  O 3n+1 , where M is a univalent metal, is the formula for univalent metal pyrophosphates when n is 2. The formula M&#39; n  P n  O 3n+1 , where M, is a divalent metal, is the formula for divalent metal pyrophosphates when n is 2. Such univalent metal pyrophosphates and divalent metal pyrophosphates can be used in the invention. Polyphosphates have the formula M n+2  P n  O 3n+1  or M&#39; n  P 2  O 3n+1 , where n is 2, 3, 4, 5, . . . , and the oxide ratio R between the cationic oxides (M 2  O or M&#39;O) and anionic oxides (P 2  O 5 ) is between 1 and 2. The oxide ratio for pyrophosphate is 2. 
     Generally 0.1 to 10 weight percent, advantageously about 0.5 to about 5 weight percent and preferably about 1.5 to about 3 weight percent of inorganic pyrophosphate is used. 
     Kirk + Othmer, &#34;Encyclopedia Of Chemical Technology&#34;, 2nd Ed., Vol. 15, (1965), pages 232 to 276, discloses a number of water-soluble inorganic pyrophosphate salts. The pertinent portions of Kirk + Othmer, &#34;Encyclopedia Of Chemical Technology&#34;, 2nd Ed., Vol. 15, (1965), pages 232 to 276, are incorporated herein by reference. 
     Examples of dialkaline metal pyrophosphates are dicalcium pyrophosphate, dibarium pyrophosphate, and dimagnesium pyrophosphate. Trialkali metal monoacid pyrophosphates, such as, trisodium hydrogen pyrophosphate (SAPP), can be used. Monoalkali metal triacid pyrophosphates, such as, sodium trihydrogen pyrophosphate, can also be present in limited amounts. Examples of other inorganic pyrophosphates include dimanganese pyrophosphate and dizinc pyrophosphate. 
     Tetrasodium pyrophosphate, one part, is soluble in 13 parts of cold water and in 2.5 parts of boiling water. It is insoluble in ethanol. Dicalcium pyrophosphate is practically insoluble in water. The invention use of the term &#34;solution&#34; includes slurries, suspensions and the like. Tetrapotassium pyrophosphate is freely soluble in water and is insoluble in ethanol. 
     The invention product does not include any fluorine-containing compound or other fluoride ion source, or quaternary ammonium compounds. The invention does not include organic acid pyrophosphates. 
     More preferably a mixture of trisodium monoacid pyrophosphate and tetrapotassium pyrophosphate is used (in a ratio to achieve the desired pH). 
     The maximum allowable GRAS level in the U.S. in a composition for sodium acid pyrophosphate (SAPP) is 2.1 weight percent and for tetrapotassium pyrophosphate (TKPP) or tetrasodium pyrophosphate (TSPP) 1.4 weight percent in baked goods. If GRAS levels change (rise) or if higher levels are allowed by the regulatory agencies, higher levels can be used in the invention. TSPP delivers about 65.4 percent by P 2  O, TKPP delivers about 52.65 percent of P 2  O 7  and SAPP delivers about 78.36 percent of P 2  O 7 . 
     The preferred invention coating contains trisodium monoacid pyrophosphate and tetrapotassium pyrophosphate in a weight ratio of about 60 to about 40. 
     The pyrophosphate(s) is used in sufficient amount to deliver generally from about 0.1 to about 5, preferably from about 3.5, most preferably 1.4 to 2.5 weight percent (based on the total composition), of P 2  O 7 . 
     A study of the application of aqueous solutions of a mixture of tetrasodium pyrophosphate and sodium acid pyrophosphate to the teeth of dogs by spraying for one mouth resulted in dose response data. The aqueous solutions containing 5 and 3 weight percent of a mixture of tetrasodium pyrophosphate and sodium acid pyrophosphate resulted in significant reductions in tartar accumulation. The aqueous solutions containing 1.5 and 0.5 weight percent of such mixture resulted in directional trends of reductions in tartar accumulation. See also U.S. Pat. No. 3,323,551. 
     The ratio of sodium acid pyrophosphate (SAPP) to tetrapotassium pyrophosphate (TKPP) is between 4 to 1 and 3 to 7, preferably between 7 to 3 and 1 to 1, most preferably about 3 to about 2. SAPP has a pH of 4.2 and TKPP (and TSPP) has a pH of 10.2, so the combination of SAPP and TKPP (or TSPP) provides a resultant pH which is a balance of the pHs of the two components. 
     The pH of the coating solution of at least one inorganic pyrophosphate salt (and baked, coated dog biscuit) is generally in the range of about 4 to about 10.5, typically from about 4.5 to about 7.5, preferably from about 5 to about 7, most preferably about 5.6 to 6.1. MILK BONE® has a pH of 6.1 to 6.4. Tartar reduction is indicated to be best at neutral pH and palatability is indicated to be best at a slightly acidic pH, so the best mode contemplates a balance of such two factors in any commercial product. 
     The coating solution application is usually conducted at a temperature of about 45° to about 140° F., preferably about 60° to about 125° F. 
     The coating solution contains a suitable surfactant. The preferred surfactant is lecithin or a modified lecithin, most preferably a modified lecithin which is in a dry form. Preferably about 0.5 to about 1.75 weight percent of the lecithin or modified lecithin is used. The surfactant or wetting agent helps the coating material to apply over the entire surface of the dog biscuit dough pieces. 
     The liquefied coating formulation best contains at least one suspension agent. The preferred suspension agent is a polysaccharide gum. Preferably about 0.05 to 1.25 weight percent of xanthan gum is used. Xanthan gum is one of the few gums which acts as an acceptable suspension agent in the invention. Any suitable gums and mucilages can be used. Xanthan gum is preferred because it is stable over a broad range of temperature and holds the same viscosity in the liquefied coating formulation over the broad temperature range. The xanthan gum has a bodying effect so that little or no separation occurs. 
     Malto-dextrin produced by hydrolyzing corn starch is preferred. It serves as a carrier (bodying), binding agent and suspension agent and helps the appearance of the coating. It is a preferred ingredient, but any suitable dextrin can be used in its place. Other malto-dextrins can also be used for the same functions. 
     An adhesive or binding agent, such as, malto-dextrins, is needed in the coating slurry to help the coating material bind (adhere) to the dog biscuit when the dog biscuit is dipped in the coating slurry. Preferably about 5 to about 15 weight percent of the dextrin or malto-dextrin is included in the coating material. 
     A carrier, such as, starch or a modified food starch, is included in the coating formulation. Preferably about 0.1 to about 5 weight percent of the food starch or modified food starch is included in the coating material. The food starch or modified food starch also serves to control the viscosity. 
     Animal fat preferably is included for flavor purposes. Other suitable flavorants can be included, particularly salt. The flavorants can be any dairy product flavorant, such as, milk or cheese, meat flavorants, such as, liver or beef, poultry and fish. Flavorants help provide palatability for the invention coating. 
     Preferably a hydrogenated vegetable oil is included in the coating formulation for sheen and to modify the melting point of the formula fats in the finished product. It also helps to prevent flaking of the coating; also the coating does not have a tacky feeling. 
     Any suitable colorant can be included in the coating formulation. The preferred colorant is caramel color, which also provides some flavor to the product. 
     The coating also incorporates sufficient water to achieve the liquefied coating composition. Amounts of the other ingredients are those which are effective to achieve their functions in the coating formulation. 
     The preferred coating formulation, besides the inorganic pyrophosphates, contains animal fat, a surfactant, such as, a modified lethicin, polysaccharide gum, a modified food starch, flavorant, colorant, hydrogenated vegetable oil, a carrier, such as a malto-dextrin, and water. 
     The coating slurry can be applied to the dog biscuit dough pieces by any suitable means, such as, spraying, dipping, soaking in a container, etc. The coating slurry is applied generally at a temperature of 45° to 200° F., preferably at about 60° to about 190° F., and most preferably at about 180°. The coating slurry has a low microbial profile at such higher temperatures. 
     The coated dough pieces can be baked using any suitable or conventional equipment and conditions. For example, the coated dough pieces can be passed into an oven such as a conventional band oven where the biscuit is baked. The conveyor belts of the oven can be coated with an edible lubricant such as a natural or synthetic cooking oil or shortening to facilitate separation from the conveyor belts of the baked coated products. Temperatures in the range of about 300° to about 600° F. can be used. The baked coated biscuits can also be subjected to subsequent drying at temperatures of about 200° to 400° F, either within the baking oven or separately, to produce the desired moisture content in the final product. 
     The coated, formed pieces are baked, followed by drying, to achieve a shelf stable product without the need of any moisture barrier protection. Baking and drying temperatures and times are those conventionally used in the production of a hard, dry canine biscuit. The pieces are dried to obtain a biscuit having a water activity of 0.70 or less. Typically baking temperatures and times are about 300° F. to about an average of 475° F. for about 25 minutes to about 8 minutes. Drying conditions are typically about 200° to about 325° F. for about 25 minutes to about 12 minutes in a forced air dryer. On a weight basis, the moisture content of the final coated biscuit product is less than or equal to 13 percent by weight, usually at least 5 weight percent, and most preferably about 8 to about 12 percent by weight, of the final biscuit at 70 percent relative humidity. 
     The ingredients, pH and ranges for the invention coated dough are the same for the invention coated dog biscuits. 
     The invention product is similar in palatability to MILK BONE® dog biscuits, which have been widely accepted and a commercial success for many years. 
     The invention product does not include any fluorinecontaining compound or other fluoride ion source, or quaternary ammonium compounds. Also the invention product does not include any organic pyrophosphates. 
     The invention deals primarily with dogs, but has a scope of teeth-bearing non-human mammals, such as, cats. 
     The invention composition is used to reduce and control tartar accumulation on canine teeth. 
     The preferred coating formulation is: 
     
                       TABLE 1______________________________________             PercentagesIngredients         Specific Ranges______________________________________Sodium acid pyrophosphate (SAPP),               1.73     0.25 to 5anhydrous powder, (non-leaveningtype)Tetrapotassium pyrophosphate               1.15     0.25 to 5(TKPP), anhydrous powderSalt                0.50       0.05 to 2.5Malto-Dextrin       9.17        2 to 30Modified Food Starch               2.00      0.1 to 10Colorant            0.50     0.01 to 3Flavorant           2.00     0.01 to 5Xanthan Gum         0.20       0.05 to 1.5Lecithin or Modified Lecithin               1.25        0.5 to 1.75Vegetable Fat       0.50      0.1 to 3Animal Fat          1.00      0.1 to 5Subtotal            20.00Water (assumed completely               80.00      50 to about 97evaporated after drying)Total               100.00______________________________________ 
    
     The following coating-baking procedure is particularly advantageous: 
     (a) dry blending the dry powders. 
     (b) adding 1/4 of the water and slurring the composition. 
     (c) adding remaining 3/4 of the water and mixing to form the coating formulation. 
     (d) heating the coating formulation to 185° to 200° F. with intermittent stirring (add animal fat at about 125° F. during the heating). 
     (e) maintaining the coating formulation at 160° to 190° F. 
     (f) apply the coating material to the unbaked dough pieces. 
     (g) baking the coated, unbaked dough pieces at 325° F. for 25 minutes 
     (h) drying the baked, coated dough pieces for 25 minutes at 225° F. in a forced-air dryer. 
     Definitions and trade name materials: 
     SAPP is trisodium acid pyrophosphate. 
     TSPP is treasodium pyrophosphate. 
     TKPP is tetrapotassium pyrophosphate.