Process For Isolating A Protein Composition And A Fat Composition From Mechanically Deboned Poultry

Abstract

A protein fraction and an oxidation stable fat fraction are recovered from poultry containing fat, bone and protein. The poultry is comminuted, mixed with a food grade acid at pH 3.6 to 4.4 to form a liquid protein fraction and a solid fat fraction. The liquid fraction is mixed with a food grade alkali to precipitate the protein.

Claims

1) The process for recovering, from mechanically deboned poultry containing fat, bone and protein, and initial levels of calcium and sodium, and having a color, a protein composition with reduced levels of calcium and sodium as compared to the initial levels of calcium and sodium, wherein the deboned poultry has 65-85% by weight lean, wherein the protein composition retains most or all of the color of the mechanically deboned poultry, the process comprising the steps of: a) comminuting the poultry in water, b) adding a food grade acid to the comminuted poultry to effect a pH of 3.6 to 4.4 thereby to solubilize the protein, wherein calcium remains insoluble, c) after addition of the food grade acid in step b), separating solid fat from the solubilized protein, wherein calcium is separated together with the solid fat from the solubilized protein, d) adding a food grade alkali to the fat to neutralize acid in the fat and to the solubilized protein to neutralize acid in the protein and to precipitate the protein, wherein sodium remains soluble, and e) recovering from the precipitate the protein composition with reduced levels of calcium and sodium as compared to the initial levels of calcium and sodium, wherein the protein composition has 14% or greater by weight protein and less than 10% by weight fat, wherein the less than 10% by weight fat is stabilized against oxidation; and wherein the protein composition retains most or all of the color of the mechanically deboned poultry.

2) The process of claim 1 wherein said pH in step b is from 3.6 to 3.8.

3) The process of claim 1 wherein step a and step b are performed simultaneously.

4) The process of claim 2 wherein step a and step b are performed simultaneously.

5) The process of claim 1 wherein said food grade acid is hydrochloric acid and/or citric acid.

6) The process of claim 2 wherein said food grade acid is hydrochloric acid and/or citric acid.

7) The process of claim 3 wherein said food grade acid is hydrochloric acid and/or citric acid.

8) The process of claim 4 wherein said food grade acid is hydrochloric acid and/or citric acid.

9) The process of claim 1 wherein water is removed from said protein in step c prior to adding said food-grade alkali.

10) The process of claim 9 wherein step a and step b are performed simultaneously.

11) The process of claim 9 wherein said food-grade acid is hydrochloric acid.

12) The process of claim 1 wherein said food grade alkali is sodium hydroxide or sodium bicarbonate.

13) The process of claim 9 wherein said food grade alkali is sodium hydroxide or sodium bicarbonate.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0012] FIG. 1 is a process flow diagram of the process of this invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0013] The present invention relates to a method for processing animal trimmings to recover meat products low in fat content and high in protein and essential amino acid content as well as a stabilized fat product. Meat product describes a protein-containing product which is suitable for human consumption as meat because it contains a certain amount of protein. Generally, mechanically deboned poultry refers to the tissue separated from poultry containing fat and bone during butchering operations. The conventional poultry cuts or parts are generally sold directly to consumers or further processed such as grinding into ground poultry. The tissue remaining after the conventional cuts are removed, generally has a fat content which is too high for human consumption as meat, but contains proteins which can be recovered.

[0014] According to the present invention, once the poultry pieces containing bone such as mechanically deboned poultry are removed from the carcasses, they are preferably forwarded directly to the process of the present invention. Alternatively, the recovered poultry can be frozen or cooled and stored prior to processing. The temperature of the recovered poultry upon removal from the carcasses is usually about 33-40 F., which corresponds to the temperature at which the carcasses are stored prior to butchering. Warmer or cooler trimmings can be used in the process of the present invention.

[0015] The poultry containing bone processed by the present invention can include all the parts normally found in an animal, including adipose tissue, fat, lean ligaments, tendons, bone parts, and the like. It is generally desirable that if components other than fat, lean, and moisture are present, they are present in small quantities and/or can be removed in the desinewing step or by hand, if desired, or can be left therein if their presence does not adversely affect the properties of the poultry meat product. If large amounts of certain components are present, it may be desirable to have them removed by conventional separation techniques prior to processing according to the present invention. For example, it is generally desirable not to have large amounts of bone present or large amounts of low quality ligaments.

[0016] Meat producing animals includes animals which are known to provide meat. Such animals include beef, pork, poultry such as chicken or turkey, e.g. mechanically deboned chicken, and the like. The lean material can be referred to as protein-containing material, and can be in the form of water soluble protein which include muscle fiber, and non-water soluble protein which are generally the myofibrilar or locomotion proteins or the connective tissue which surrounds muscle fiber and which attach the muscle fibers to ligaments. Of particular interest for purposes of the present invention is the presence of the water soluble protein and the acid soluble protein from the animal muscle tissue in the fatty tissue within the fat trimmings. By separating this protein material from the animal trimmings, a high quality meat product can be provided. This product can be utilized as an additive to conventional meat products such as to hamburger.

[0017] Poultry containing meat, fat and bone, which can be used in the present invention preferably, have an average fat content of between about 5 and 50% by weight, preferably between about 10 and 30% by weight. The lean content of the poultry containing bone is preferably between about 65% and 85% by weight, and more preferably between about 75 and 85% by weight. The lean content includes protein and moisture. In order to ensure reliable and consistent results, it is preferable that the lean content of the animal trimmings is at least about 30% by weight and preferable at least about 39% by weight.

[0018] Referring to FIG. 1 which illustrates a preferred embodiment of this invention, a feed 12 such as mechanically deboned or separated poultry containing about 50% by weight muscle tissue and about 50% by weight fat, mechanically separated chicken or the like are directed to a comminution step 14 which increases the surface area of the poultry rendering it more suitable for further processing. Suitable comminution apparatus include meat grinder available from Weiler and Company Corporation located in Whitewater, Wis. or Carnitec USA, Inc, located in Seattle, Wash. The starting poultry is first ground to a size that enables it to be put through a micro-cutter. It is preferable to coarse cut % inch, followed by a inch grind. Some mechanically deboned meat may not need to be pre-ground because it is already at the appropriate particle size. Once ground, the material is mixed with water (33-40 F.) at a ratio of one part ground meat to approximately 5-6 parts water. This amount of water can vary and can go as high as approximately 1 part ground meat to 10 parts cold water. The addition of water lowers the ionic strength of the homogenate which is required for complete solubilization of the proteins. Optionally, acid can be added to the poultry in step 20 to improve protein solubilization. The comminuted poultry is directed to homogenization step 16 where it is mixed with potable water 18 at a water temperature typically between about 33 F. and about 40 F. and homogenized, typically to an average particle size of about 0.5 to about 4 millimeters preferably between about 1 to about 2 millimeters. A preference has been shown for a micro-cut with a 0.035 mm cutting head size. Representative suitable homogenizers for this purpose include emulsifiers or micro-cutters, available from Stephan Machinery Corporation, located in Columbus, Ohio or high-shear mixers available from Silverson, located in East Longmeadow, Mass. or the like.

[0019] In a step to control microorganisms, the temperature of the homogenate is kept cold throughout the process (33-40 F.). The cold temperature is most effective for separating the fat from the protein. This unit operation is accomplished while the pH is still near the pH of the initial muscle. An alternative is to add enough food-grade acid to bring the composite pH to the isoelectric point. Typically, the isoelectric point is about pH 5.5, but it can vary from species to species. At the isoelectric point, proteins are least able to form emulsions with lipid molecules, and, therefore, more lipid renders away from the proteins during the extraction process. Once the tissue is homogenized, it is ready to be adjusted to a low pH.

[0020] The resultant homogenate is directed to step 22 wherein it is mixed with a food grade acid 24 such as dilute hydrochloric acid, dilute phosphoric acid, dilute citric acid, ascorbic acid, tartaric acid or mixtures thereof or the like in order to reduce the pH of the homogenate to between pH 3.6 and pH 4.4, preferably between pH 3.6 and pH 3.8 to dissolve animal muscle tissue thereby to obtain a satisfactory yield of protein such as 80% yield or higher in an acidic protein solution thereof while retaining the fat portion in solid form. It is preferred to utilize hydrochloric acid since its use results in more significant reduction of viable microorganisms in the acidic protein solution.

[0021] Acidification of the proteins under low salt conditions has been shown to unfold the proteins, which is believed to create more surface area along the proteins and hence more potential water binding sites. Once the proteins are soluble, the fat renders away from the proteins and floats to the surface of an aqueous acidic solution. Other potential impurities, including any residual bone, skin or sinew, stay insoluble as well. The pH is adjusted to 3.6 to 4.4. As an example, the approximate amount of acid needed to effect solubilization of the muscle proteins is approximately 0.15 to 0.80 weight %, e.g. 0.198 weight % based on the weight of HCl to total weight (pH 3.74). This amount is dependent on the desired low pH (pH 3.6 or 4.4) and also on the pH of the starting material. Suitable mixers to effect this step include Lightning Mixers available from SPX Corporation, located in Charlotte, N.C. or the like.

[0022] The resultant mixture of acidic solution of animal muscle protein and solid fat then is directed to separation step 26 such as a decanter centrifuge and/or screen filter 26 to separate the acidic protein solution from the solid fat.

[0023] Subsequent to the solubilization of the proteins and removal of impurities and fat, the proteins are subjected to an increase in pH such as by the addition of diluted, food-grade base such as sodium hydroxide (NaOH) or sodium bicarbonate (NaHCO.sub.3). The base is added until the isoelectric point is obtained and the proteins refold and rejoin with each other to form large, fiberized molecules. Upon reaching the isoelectric point pH, the proteins easily release their closely aligned water molecules, and the moisture content can be returned to the moisture content found in meat or consistent with LFTM. The solid fat in step 28 is optionally mixed with a food grade alkali to separate water from fat and to neutralize the fat. Optionally, cold potable water from step 29 can be added to the fat in step 28. The alkali promotes separation of fat from water. The fat then is filtered in step 31 to remove water from fat and reduce the water content from about 70 to 50 weight percent to about 30 to 20 weight percent. Optionally, the fat can be refrigerated or frozen in step 33. Suitable filtration apparatus include vibrating screen available from Sweco Corporation, located in Florence, Ky. or the like. The screens have a size between about 4000 micron and about 2000 microns, preferably between about 3500 microns and about 2500 microns. Additional base can be added in step 34 to bring the pH of the precipitated proteins back to the original pH of the tissue. This assures that the base (NaOH or NaHCO.sub.3) has fully reacted with and consumed all of the previously added acid such as HCL or citric. An optional step is to direct the protein product to a unit operation 35 which removes water to concentrate the liquid for the purpose of creating larger fibers upon raising the pH. The unit operation could consist of any device found to remove water in a continuous or batch manner, such as an evaporator or more desirable an ultrafiltration unit. The amount of water removed can vary, however, greater amounts of water removed results in larger and more robust and sturdy fibers and increased protein recovery. The resultant protein product is a viscous sediment containing protein at a concentration of about 4-14 percent by weight or higher to produce a protein containing solution which is directed to mixing step 34 wherein it is mixed with food grade alkaline 36 such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, or the like. The protein product is precipitated in step 38 and is recovered such as by centrifugation and filtration in step 40. Optionally, an ultrafiltrate retentate having a >5000-1 0000 molecular weight cut off (MWCO) is recovered in step 41. This ultrafiltrate can be blended as desired with the precipitated protein in step 43. This results in a protein product having a reduced sodium content. The sodium is concentrated in the lower molecular weight fraction that is discarded. The resultant product has desired reduced sodium and is obtained by a process (pH 3.6-4.4) that provides high yield of protein from the starting poultry feed of about 80% or greater. Thus, the process of this invention, provides a greatly improved protein product over the available prior art.

[0024] The protein product from step 40 contains 14 percent or greater by weight protein, contains less than 10 percent by weight fat, is produced at a temperature less than 110 F., can be frozen within 30 minutes in step 42 from process completion, does not allow a significant increase in bacteria and, in the embodiment wherein the protein precipitated with alkali does not retain chemicals or additives other than a low concentration of salt such as sodium chloride or the like.

[0025] The meat protein products of this invention are not significantly altered by the processing method of this invention. An examination of the proteins associated with the starting meat source and the lean cold processed meats (precipitated refolded protein) shows that the extraction process is mild enough not to effect changes in the proteins throughout the entire process. It also shows that very little to no hydrolysis has occurred during the processing, partly due to the low temperature. Refolding of the protein also does not affect its profile.

[0026] In summary, the process of this invention produces protein in higher yields as compared to the prior art, contains fewer microorganisms as compared to the prior art and is in a form by which it can be more easily mixed with meat as compared to the products of the prior art. In addition, the fat product obtained is stabilized against oxidation.

[0027] The following examples illustrate this invention and are not intended to limit the same.

Example I

[0028] Frozen mechanically separated chicken was obtained from a commercial production facility in Georgia. The product was fully thawed at refrigerated temperatures and the thawed meat was mixed with cold water at a 1:4 ratio (meat: water). The mixture was homogenized using a Kitchen Aid hand-held mixer for 2 min at high speed. The homogenate was adjusted to pH 2.8 or 3.6 using hydrochloric acid (2N), The acidified homogenate was filtered through a 1000 micron stainless steel screen. The filtrate was adjusted to pH 5.5 using sodium hydroxide (4N) and filtered through the same washed 1000 micron screen to de-water. Precipitated samples were frozen and sent to Silliker Labs, Chicago Heights, IL for analysis.

TABLE-US-00001 TABLE 1 Metal and oxidation values of precipitated Lean Cold Processed Chicken made for pH 2.8 and pH 3.6 Starting LCPC from LCPC from Analyte MDM pH 2.8 pH 3.6 Procedure Calcium (mg/100 7.55 4.02 3.31 AOAC 984.27 g, dry wgt basis) Sodium (mg/100 3.76 4.10 3.21 AOAC 984.27 g, dry wgt basis) PeroxySafe 0.020 0.014 0.004 AOAC R1 Peroxide value 03050 (meq/kg) (dry wgt basis)

[0029] Processing of mechanically separated poultry through the invention was shown to lower sodium and calcium and overall reduce the amount of oxidation that occurs in the final product compared to the starting material. Processing to pH 3.6 compared to pH 2.8 was shown to result in a great reduction in metals as well as further reduce the amount of oxidation that had occurred. It can be found in the literature that oxidation accelerates at low acidic pH values and therefore could explain in this experiment the oxidation increase as the meat is processed at the lower pH. It is probable that all of the increase in sodium in the lower pH sample (2.8) compared to the pH 3.6 sample is due to the fact that it required more sodium hydroxide to bring the lower pH sample to its iso-electric point.

Example 2

[0030] This example illustrates that recovery of protein from meat trimmings must be effected at a pH of 3.6 or above in order to recover a protein product from satisfactory color. This example also illustrates that initially obtaining protein having an unsatisfactory color cannot be reversibly converted to a protein product having a satisfactory color.

[0031] The results obtained in Table 2 were obtained with 40 g samples of ground beef. To each sample was added 160 ml of cold tap water (40 F.). The samples were then homogenized to a particle size of about 100 microns. The pH of each sample was adjusted with 1M food grade hydrochloric acid to a pH set forth in Table 2. Each sample was centrifuged for 8 minutes at 5000 g at 4 C. and then filtered through glass wool to separate solid fat from protein liquid composition. 40 ml of each liquid portion was poured into a container on top of white paper. Each sample was then measured twice with each sample with a Minolta colorimeter that measures L*, a* and b* values as set forth above.

[0032] The average L*, a* and b* were then computed as shown in Table 2.

TABLE-US-00002 TABLE 2 Color Measurements Ground Beef L* a* b* pH L* (1) a* (1) B* (1) L* (2) a* (2) b* (2) (AVG) (AVG) (AVG) 5.8a 75.33 14.63 15.53 61.95 30.29 21.55 68.64 22.46 18.54 5.8b 71.40 18.35 16.59 76.92 13.93 15.31 74.16 16.14 15.95 5.8 71.40 19.30 17.25 (AVG) 3.8a 56.92 25.11 21.01 58.77 23.53 20.80 57.85 24.32 20.91 3.8b 55.57 26.40 21.19 59.18 23.58 20.89 57.38 24.99 21.04 3.8 57.61 24.66 20.97 (AVG) 3.6 a 56.01 20.38 20.46 57.35 19.46 20.54 56.68 19.92 20.50 3.6b 57.72 21.47 20.92 58.63 20.90 20.81 58.18 21.19 20.87 3.6 57.43 20.55 20.68 (AVG) 3.5a 58.80 15.03 20.67 61.09 13.97 20.40 59.95 14.50 20.54 3.5b 59.69 13.76 20.64 61.92 12.84 20.32 60.81 13.30 20.48 3.5 60.38 13.90 20.51 (AVG) 3.4 a 57.06 14.59 20.62 61.79 12.73 20.14 59.43 13.66 20.38 3.4 b 57.96 14.49 20.82 60.16 13.60 20.54 59.06 14.05 20.68 3.4 (AVG) 59.24 13.85 20.53 3.3a 61.58 12.33 20.52 65.48 10.78 19.50 63.53 11.56 20.01 3.3b 58.78 13.62 20.84 61.65 12.45 20.38 60.22 13.04 20.61 3.3 (AVG) 61.87 12.30 20.31 3.3 to 3.8 a 57.77 19.36 20.46 59.37 18.39 20.45 58.57 18.88 20.46 3.3 to 3.8 b 57.61 16.67 20.56 57.47 16.70 20.56 57.54 16.69 20.56 3.3 to 3.8 58.06 17.78 20.51 (AVG)