PET FOOD PRODUCT COMPRISING DENATURED ZEIN PROTEIN

Abstract

A process for the preparation of a food product, particularly a pet food product, comprising zein protein and particularly also comprising animal protein, said process comprising the steps of: (i) providing a composition comprising zein protein; (ii) treating the composition from step (i) to denature said zein protein to provide a composition comprising denatured zein protein; and (iii) mixing said composition comprising denatured zein protein with other ingredients of said food product, particularly animal protein.

Claims

1. A process for the preparation of a pet food product, said process comprising: (i) providing a composition comprising zein protein; (ii) treating the composition from step (i) to denature said zein protein to provide a composition comprising denatured zein protein; and (iii) mixing said composition comprising denatured zein protein with animal protein to form said food product.

2. The process according to claim 1, wherein said pet food product is a wet pet food.

3. The process according to claim 1, wherein said pet food product comprises reconstituted animal material.

4. The process according to claim 1, wherein said pet food product comprises a blended proteinaceous matrix or network of animal protein and denatured zein protein.

5. The process according to claim 1, wherein the animal protein comprises ground animal material.

6. The process according to claim 1, further comprising: (iv) preparing a slurry from the mixture of step (iii) and subjecting the slurry to conditions of shear to produce an emulsion of said mixture; (v) heating the mixture of step (iii), or where performed step (iv), to an internal temperature of at least 70 C., wherein the duration of heating is at least 30 seconds; and (vi) forming discrete pieces of said pet food product.

7. The process according to claim 1, wherein said treating step (ii) comprises an application of mechanical energy to denature said zein protein.

8. The process according to claim 1, wherein said treating step (ii) comprises passing said composition comprising zein protein through a twin-screw extruder.

9. The process according to claim 1, wherein said treating step (ii) is conducted at a temperature in the range of from about 100 C. to about 160 C.

10. The process according to claim 1, wherein said composition comprising zein protein of step (i) is in powder form.

11. The process according to claim 1, wherein prior to or during said treating step (ii) an aqueous medium is added to said composition comprising zein protein in amount such that the weight ratio of said composition to said aqueous medium is from about 70:30 to about 60:40.

12. (canceled)

13. The process according to claim 1, wherein said treating step (ii) comprises adjusting the pH of the composition to a pH of no more than 7.00.

14. The process according to claim 1, wherein said treating step (ii) avoids or substantially avoids the formation of gelled zein protein during the performance of said step (ii).

15. The process according to claim 1, wherein said denatured zein protein provided by step (ii) is in particulate form or micro-particulate form.

16. The process according to claim 15, wherein said denatured zein protein provided by step (ii) is in particulate form or micro-particulate form such that the particulate or micro-particulate forms are non-aggregated or substantially non-aggregated.

17. The process according to claim 1, wherein said denatured zein protein provided by step (ii) is in particulate form such that the particle size is no greater than a particle size of the native zein protein from which it is derived.

18. The process according to claim 1, wherein prior to or during treating step (ii), one or more water-dispersible material(s) is added to the composition comprising zein protein.

19. The process according to claim 18, wherein said one or more water-dispersible material(s) is selected from proteins, plant-derived proteins, hydrocolloids, or gums.

20. (canceled)

21. (canceled)

22. The process according to claim 1, wherein between steps (ii) and (iii) said composition comprising denatured zein protein is dried, collected and stored for subsequent use in said process for the preparation of a pet food product.

23. (canceled)

24. A process for preparing a wet pet food product, said process comprising: (i) providing a composition comprising zein protein; (ii) treating the composition from step (i) to denature said zein protein to provide a composition comprising denatured zein protein; (iii) mixing said composition comprising denatured zein protein with an animal protein source; (iv) preparing a slurry from said mixture and subjecting the slurry to conditions of shear to produce an emulsion of said mixture; (v) heating the mixture to an internal temperature of at least 70 C.; (vi) forming discrete pieces of reconstituted animal material; (vii) optionally combining said reconstituted animal material with a sauce; (viii) inserting said reconstituted animal material and optional sauce into packaging; and (ix) sealing and sterilizing the package to provide a packaged wet pet food product.

25. (canceled)

26. (canceled)

27. (canceled)

28. (canceled)

29. (canceled)

30. (canceled)

31. (canceled)

32. (canceled)

Description

EXAMPLES

Example 1a

[0122] Maize gluten (zein) powder having a protein content of 60 wt % was mixed with water in the mixing chamber of a multi-zone twin-screw extruder, to provide a mixture having a water content of 35 wt % (i.e. 65:35 maize gluten powder:water). The feed rate of water and zein powder was 39 kg/h. The extruder was operated with a screw speed of 300 rpm. The extruder had a heating zone and a cooling zone. The maximum temperature of the heating zone was 140 C. The zein/water mixture was passed into the heating zone of the extruder to denature the zein protein, and the denatured zein protein was then passed into the cooling zone of the extruder where it was cooled at successive temperatures to 50 C. and 30 C. The particle size and the moisture content after extrusion of the product were analysed, and the results are shown in Table 1. The Control in Table 1 is native zein protein, i.e. without denaturation.

Example 1b

[0123] The procedure of Example 1a was repeated except that the water was replaced with a 0.5M aqueous solution of NaOH, to provide a 65:35 mixture of maize gluten powder:aqueous solution.

Example 1c

[0124] The procedure of Example 1a was repeated except that the water was replaced with a 50:50 mixture of glycerol:water, to provide a 65:35 mixture of maize gluten powder:glycerol/water as before.

TABLE-US-00001 TABLE 1 Particle Size (D90; m) Moisture Content (%) Control 800 9.0 Example 1a 535 34.0 Example 1b 473 32.9 Example 1c 724 18.4

[0125] The resulting denatured zein protein was dispersible in water at room temperature, and able to be combined with an animal protein to form a reconstituted animal material in a meat emulsion, as described below.

Examples 2a, 2b and 2c

[0126] A series of experiments was conducted, in which the denatured zein protein described in each of Examples 1a, 1b and 1c above was used as an ingredient in the manufacture of a reconstituted animal material in accordance with conventional techniques and using a conventional recipe, the output being chunks having dimensions of about 7 mm7 mm7 mm. A Reference Example using the conventional recipe was also made by adding porcine liver to approximately 830 g of meat emulsion, such that the liver was present at 17 wt % of the dry matter of the reconstituted animal material. For each sample, the denatured zein protein (DZP) was incorporated into the reconstituted animal material at a level of 10 wt %, by total weight of the reconstituted animal material. Recipes were calculated so that every recipe retains the same amount of dry solids compared to the existing recipe. Thus, additional water was included in order to keep the moisture level of the liver replacement at the same level as the liver in the original recipe i.e. at 78.35%. The basis of this calculation is 1 kg emulsion.

TABLE-US-00002 TABLE 1 Recipes DZP in Liver in Liver DZP Water Moisture Example recipe (%) recipe (%) (g) (g) added (g) (g) Reference 0 17 170 0 0 78.35 Example 2 10 7 70 39.36 60.64 78.35

[0127] The rheology of the emulsions was analysed and each of the emulsions of Examples 2a, 2b and 2c exhibited a viscosity of from about 610.sup.4 to 910.sup.4 cP, which was within the acceptable and workable limits suitable for the downstream processing equipment and comparable with the viscosity of the emulsion of the Reference Example.

[0128] A Comparative Example emulsion was prepared in the same way as described above but using native zein protein (i.e. not denatured). The viscosity of this emulsion was significantly greater that the viscosities of Examples 2a, 2b and 2c and the Reference Example, at about 1.110.sup.5 cP.

[0129] After mixing of the ingredients, the emulsions were cooked in a steam oven and the chunks cut into regular 777 mm sizes. Upon visual inspection, the freshly made chunks of each of Examples 2a, 2b and 2c exhibited excellent form and structure, and were similar in appearance to the conventional recipe of the Reference Example. In contrast, the chunks of the Comparative Example exhibited dry regions where the zein protein had not mixed adequately with the rest of the emulsion.

[0130] The hardness of the fresh chunks was analysed and in all cases the chunks of Examples 2a, 2b and 2c exhibited a chunk hardness which was at least as hard as the Reference Example, and would hence be expected to perform at least as well as the Reference Example in terms of fines content.

[0131] The chunks (50 g) from each sample were placed into a pouch with water (50 g), and the pouch sealed and then retorted (sterilised) under conventional conditions. The pouch was maintained for two weeks at 25 C. After two weeks, the pouches were opened and the chunks inspected as before. In all cases, the mature chunks of Examples 2a, 2b and 2c exhibited excellent form and structure, and were similar in appearance to the conventional recipe of the Reference Example. No crumbling, stickiness or dryness was observed. This test represents an accelerated ageing test to gauge how the chunks behave in a conventional gravy or sauce when retorted and stored.

[0132] The freshly made and mature chunks were also tested by texture profile analysis (TPA) as described herein. The results show that the chunks of Example 2a, 2b and 2c exhibited hardness, adhesiveness, cohesiveness and chewiness which was substantially equivalent to, and within acceptable quality control limits for, the existing commercial product, as represented by the Reference Example, in respect of both the fresh chunk and the mature chunk.

Examples 3a and 3b

[0133] The procedure of Example 1a was repeated but replacing a portion of the zein protein with a water-dispersible protein which had greater hydrophilicity than the zein protein. In Example 3a the zein protein was blended with gelatin in a ratio of 95:5, and in Example 3b the zein protein was blended with gelatin in a ratio of 90:10. The resulting mixture again had of protein:water ratio of 65:35. The presence of the gelation in the protein fraction resulted in a reduction in the particle size; for instance, the measured D90 value of the particulate material of Example 3b was 425 m.

[0134] The micro-particulate denatured zein protein of Examples 3a and 3b were used to prepare emulsions and chunks in the same was as described above. In both instances, the freshly made chunks exhibited excellent form and structure upon visual inspection, and were similar in appearance to the conventional recipe of the Reference Example. The fresh and mature hardness of the chunks were analysed and comparable to the Reference Example in both cases.

Examples 4a, 4b and 4c

[0135] The procedure of Example 1b was repeated but replacing a portion of the zein protein with gelatin, namely 5 wt % (Example 4a), 7.5 wt % (Example 4b) and 10 wt % (Example 4c). The resulting mixture had of ratio of protein:aqueous 0.5M NaOH solution of 65:35. The resultant micro-particulate denatured zein protein was used to prepare emulsions and chunks as described above. The viscosity of the emulsions and the chunk hardness of the fresh and matured chunks were all within acceptable limits and comparable with the Reference Example. Upon visual inspection, the chunks exhibited excellent form and structure, with even blending of the zein protein and similar appearance to the Reference Example. Example 4b and 4c in particular demonstrated excellent homogeneity.

Example 5

[0136] The procedure of Example 1a was repeated except that liquid whey concentrate (LWC; approx. 6 wt % whey protein on a dry matter basis) was used as a hydrophilic plasticiser in place of the water, to provide a mixture of zein protein:LWC in a ratio of 65:35.

Example 6

[0137] The procedure of Example 1a was repeated except that 50 wt % of the zein protein was replaced with whey protein isolate powder, to provide a mixture of zein protein, whey protein and water in a protein:water ratio of 65:35. The presence of the more hydrophilic whey protein in the protein fraction resulted in a significant reduction in the particle size; the measured D90 value of the particulate material of Example 6 was about 200 m.

Example 7

[0138] The procedure of Example 1b was repeated except that 50 wt % of the zein protein was replaced with whey protein isolate, to provide a mixture of zein protein, whey protein and 0.5M NaOH aqueous solution which had a protein:aqueous solution ratio of 65:35.

Example 8

[0139] The procedure of Example 1b was repeated except that 1 wt % of the zein protein was replaced with gum Arabic, to provide a mixture of zein protein, gum Arabic and 0.5M NaOH aqueous solution which had a protein:aqueous solution ratio of 65:35.

[0140] The micro-particulate denatured zein protein of Examples 5, 6, 7 and 8 were used successfully to prepare emulsions and chunks, all of which demonstrated processability and product characteristics within acceptable quality control limits.

[0141] The results demonstrate that, unexpectedly, micro-particulate denatured zein protein is an excellent partial replacement for animal protein in pet food products.