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 . 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______________________________________ ( 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 ). ( 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 .
process for preparing baked dog biscuits having a coating containing at least one inorganic pyrophosphate , comprising : 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 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 .