Synergistic cold sterilizing and preserving method for fresh meat with high voltage electric field plasma and nano photocatalysis

Abstract

Disclosed is a synergistic sterilizing and preserving method for fresh meat with high voltage electric field plasma and nano photocatalysis, which belongs to the technical field of cold sterilization of food package. The method comprises the steps: uniformly mixing a photocatalyst, a coupling agent and coating liquid at a high speed, performing the coupling to obtain modified coating liquid, smearing the coating liquid onto the surface of a plastic packaging film to obtain a packaging material with a photocatalytic bacteriostatic function, packaging fresh meat in an MAP (modified atmosphere packing) manner by adopting the bacteriostatic packaging material, wherein a coating containing the photocatalytic material is disposed at the inner side of a package, placing the packed fresh meat between two electrodes of a plasma generating device, and performing the plasma sterilization under the condition of a high voltage electric field.

Claims

1. A synergistic cold sterilizing and preserving method for fresh meat with plasma and nano photocatalysis, comprising: (1) preparing a bacteriostatic packaging material having a photocatalytic bacteriostatic function, the preparing of the bacteriostatic packaging material comprising uniformly mixing a photocatalyst, a coupling agent and a coating liquid to form a mixture, performing coupling to obtain a modified coating liquid, and smearing the modified coating liquid onto a surface of a plastic packaging film to form a coating on the surface, wherein the photocatalyst is at least one of nano TiO.sub.2, nano ZnO and nano Fe.sub.2O.sub.3, wherein an amount of the photocatalyst in the mixture is 0.3-2 g/L of coating liquid and wherein a mass concentration of the coating liquid in the mixture is 2-8%; (2) packaging fresh meat in an MAP manner by placing the fresh meat within a package comprised of the bacteriostatic packaging material, and introducing a gas into the package, wherein the gas is at least one of carbon dioxide, oxygen, nitrogen, helium, neon and argon, and wherein the coating is disposed at an inner side of the package; and (3) placing the MAP packaged fresh meat between two electrodes of a plasma generating device, and performing plasma sterilization under a condition of an electric field, wherein a voltage strength of the plasma generating device is 10-50 kv/cm, and a processing time is 1 second to 6 minutes.

2. The synergistic cold sterilizing and preserving method for fresh meat with plasma and nano photocatalysis according to claim 1, wherein a material of the plastic packaging film is polyamide, polypropylene, polyethylene or polyester.

3. The synergistic cold sterilizing and preserving method for fresh meat with plasma and nano photocatalysis according to claim 1, wherein the coating liquid is PVA coating liquid, PE coating liquid or PVDC coating liquid.

4. The synergistic cold sterilizing and preserving method for fresh meat with plasma and nano photocatalysis according to claim 1, wherein the plasma generating device comprises a voltage regulator, an electric field generator, an upper electrode, an upper insulation protection plate, a lower electrode and a lower insulation protection plate, wherein the MAP packaged fresh meat is placed between the upper electrode and the lower electrode; the upper insulation protection plate is arranged between an upper surface of a packaging box and the upper electrode, and the lower insulation protection plate is arranged between a lower surface of the packaging box and the lower electrode.

5. The synergistic cold sterilizing and preserving method for fresh meat with plasma and nano photocatalysis according to claim 4, wherein the upper protection plate and the lower insulation protection plate are each a polypropylene or polyethylene plate, a thickness of the upper protection plate is 1.3-1.8 mm, and a thickness of the lower protection plate is 1.8-3.5 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a high voltage electric field plasma generating system.

DETAILED DESCRIPTION

(2) The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited, as follows:

(3) The high voltage electric field plasma generating system used in embodiments of the present invention is as shown in FIG. 1 ; the device comprises a voltage regulator, a high voltage electric field generator, an upper electrode, a lower electrode and an insulation protection plate, wherein the MAP packaged fresh food is placed between the upper electrode and the lower electrode; an upper insulation protection plate is arranged between the upper surface of a packaging box and the upper electrode, and a lower insulation protection plate is arranged between the lower surface of the packaging box and the lower electrode; and the adopted insulation protection plate is a polypropylene or polyethylene plate, the thickness of the upper protection plate is 1.3-1.8 mm, and the thickness of the lower protection plate is 1.8-3.5 mm.

(4) Samples adopted in embodiments 1-4 and a reference example 1 are fresh chicken fillet; the fresh chicken fillet is randomly selected from a chicken segmentation production line of a production workshop of a slaughter factory and is transported back to a laboratory in an ice box; the surface of the chicken is removed to reserve the middle sterile portion, and the weight of the chicken fillet is kept approximately at 955 g; and bacteria such as M. caseolyticus and P. fluorescens with a known concentration are inoculated to the surface of the chicken.

(5) The coating amount of the modified coating liquid on the surface of the plastic packaging film in embodiments 1-4 is 0.3-5 g/m.sup.2.

(6) Embodiment 1

(7) First, PVA particles are heated and then dissolved in 100 ml distilled water to obtain the PVA coating liquid with the mass concentration of 4.3%; then nano TiO.sub.2 and the coupling agent 570 are added into the PVA coating liquid and are sufficiently stirred to prepare homogeneous suspension, thereby obtaining the modified coating liquid, wherein the consumption of nano TiO.sub.2 is 0.5 g/L coating liquid, and the consumption of the coupling agent 570 is 10 mg/100 g coating liquid; and finally the modified coating liquid is smeared onto the polyamide (PA) plastic film and is dried to form a film, thereby obtaining the bacteriostatic packaging material.

(8) The preprocessed chicken is placed into a food packaging container and is packaged in an MAP manner by utilizing the bacteriostatic packaging material, the coating containing the photocatalytic material is disposed at the inner side of the package, the introduced gas in the packaging process is oxygen and Ar (the volume ratio is 1:1), the packaged packaging box is arranged between the electrodes so as to be processed by plasma, the plasma processing time is 60 s, and the processing voltage strength is 30 kv/cm.

(9) Embodiment 2

(10) First, PVA particles are heated and then dissolved in 100 ml distilled water to obtain the PVA coating liquid with the mass concentration of 3.5%; then nano ZnO and the coupling agent 570 are added into the coating liquid and are sufficiently stirred to prepare homogeneous suspension, thereby obtaining the modified coating liquid, wherein the consumption of nano ZnO is 0.5 g/L coating liquid, and the consumption of the coupling agent 570 is 11 mg/100 g coating liquid; and finally the modified coating liquid is smeared onto the polyamide (PA) plastic film and is dried to form a film, thereby obtaining the bacteriostatic packaging material. The preprocessed chicken is placed into a food packaging container and is packaged in an MAP manner by utilizing the bacteriostatic packaging material, the coating containing the photocatalytic material is disposed at the inner side of the package, the introduced gas in the packaging process is N.sub.2 and O.sub.2 (the volume ratio is 1:1), the packaged packaging box is arranged between the electrodes so as to be processed by plasma, the plasma processing time is 120 s, and the processing voltage strength is 30 kv/cm.

(11) Embodiment 3

(12) First, PVDC particles are heated and then dissolved in 100 ml distilled water to obtain the PVDC coating liquid with the mass concentration of 5.8%; then nano Fe.sub.2O.sub.3 and the coupling agent 570 are added into the coating liquid and are sufficiently stirred to prepare homogeneous suspension, thereby obtaining the modified coating liquid, wherein the consumption of nano Fe.sub.2O.sub.3 is 0.5 g/L coating liquid, and the consumption of the coupling agent 570 is 12 mg/100 g coating liquid; and finally the modified coating liquid is smeared onto the polyamide (PA) plastic film and is dried to form a film, thereby obtaining the bacteriostatic packaging material.

(13) The preprocessed chicken is placed into a food packaging container and is packaged in an MAP manner by utilizing the bacteriostatic packaging material, the coating containing the photocatalytic material is disposed at the inner side of the package, the introduced gas in the packaging process is CO.sub.2 and N.sub.2 (the volume ratio is 1:1), the packaged packaging box is arranged between the electrodes so as to he processed by plasma, the plasma processing time is 180 s, and the processing voltage strength is 30 kv/cm.

(14) Embodiment 4

(15) First, PVA particles are heated and then, dissolved in 100 ml distilled water to obtain the PVA coating liquid with the mass concentration of 3.5%; then nano Fe.sub.2O.sub.3, nano ZnO and the coupling agent 570 are added, into the PVA coating liquid and are sufficiently stirred to prepare homogeneous suspension, thereby obtaining the modified coating liquid, wherein the consumption of nano Fe.sub.2O.sub.3 is 0.3 g/L coating liquid, the consumption of the nano ZnO is 0.3 g/L coating liquid, and the consumption of the coupling agent 570 is 10 mg/100 g coating liquid; and finally the modified coating liquid is smeared onto the polyamide (PA) plastic film and is dried to form a film, thereby obtaining the bacteriostatic packaging material.

(16) The preprocessed chicken is placed into a food packaging container and is packaged in an MAP manner by utilizing the bacteriostatic packaging material the coating containing the photocatalytic material is disposed at the inner side of the package, the introduced gas in the packaging process is a mixture of O.sub.2, CO.sub.2 and N.sub.2 (the volume ratio is 1:1:1), the packaged packaging box is arranged between the electrodes so as to be processed by plasma, the plasma processing time is 120 s, and the processing voltage strength is 30 kv/cm.

(17) Reference Example 1

(18) The condition of the embodiment is the same with that of embodiment 1, and only the bacteriostatic packaging material is replaced with an ordinary polyamide (PA)/polyethylene film.

(19) Performance Test:

(20) 1. Test on Quantity of Bacterial Colonies

(21) P. fluorescens and M. caseolyticus experimental strains in putrid chicken adopted by the bacterial suspension are cultured at a table concentrator until an appropriate concentration is achieved, and after the culture medium is removed, sterile PBS is used to prepare the bacterial suspension for standby application. Before the samples in embodiments 1-5 and reference example 1 are sterilized, the content of P. fluorescens strain is 6.150.41 log, and the content of the M. caseolyticus strain is 6.390.32 log. After the samples in embodiments 1-4 and reference example 1 are sterilized by plasma, the content of the strain is as shown in table 1.

(22) TABLE-US-00001 TABLE 1 Variation of Quantity of Bacterial Colonies on the Surface of Plasma Processed Chicken Item P. fluorescens (log) M. caseolyticus (log) Embodiment 1 2.66 0.14 3.0 0 Embodiment 2 3.06 0.35 3.36 0.21 Embodiment 3 3.34 2.81 3.75 0.28 Embodiment 4 3.75 0.42 4.0 0.32 Reference example 1 5.15 0.35 5.50 0.01

(23) It can be seen from table 1 that after the plasma processing, the quantity of the bacterial colonies of M. caseolyticus and P. fluorescens in the novel homemade bacteriostatic nano material film packaging group is far smaller than that in an ordinary film packaging group.

(24) 2. Influence of Different Storage Times on the Quantity and Color of the Bacterial Colonies

(25) TABLE-US-00002 TABLE 2 Variation of Quantity of Bacterial Colonies on the Surface of Plasma Processed and packed Chicken Item 3 days 7 days 10 days 14 days Embodiment 1 2.47 0.21 3.03 0.18 3.46 0.35 4.37 0.36 Embodiment 2 3.07 0.25 3.78 0.22 4.63 0.33 5.29 0.30 Embodiment 3 3.78 0.31 4.37 0.28 5.48 0.42 6.30 0.30 Embodiment 4 4.31 0.31 4.78 0.28 5.64 0.25 6.31 0.24 Reference 5.39 0.23 7.44 0.31 7.57 0.33 8.36 0.32 example 1

(26) TABLE-US-00003 TABLE 3 Influence on Color Difference L* of the Plasma Processed Packaged Chicken in the Storage Process Processing group 3 days 7 days 10 days 14 days Embodiment 1 Before the processing 55.06 2.7 56.09 4.98 56.64 3.37 58.35 5.75 After the processing 58.21 2.16 55.71 3.51 58.29 3.73 58.91 4.20 Embodiment 2 Before the processing 56.88 3.24 59.58 2.8 57.43 2.17 55.72 3.97 After the processing 59.6 2.68 59.84 4.63 56.19 2.17 55.67 2.16 Embodiment 3 Before the processing 55.5 3.2 58.18 3.36 56.88 4.21 59.58 4.01 After the processing 58.8 2.34 58.85 2.98 59.34 2.28 61.02 2.42 Embodiment 4 Before the processing 56.92 4.49 58.03 2.84 56.56 2.54 58.4 3.39 After the processing 59.42 4.59 59.9 3.02 58.22 2.69 60.15 3.00

(27) After the plasma processing, compared with that in the control group, the quantity of the bacterial colonies on the surface of the packaged chicken is obviously reduced, as shown in table 2. The chicken in the control group can be stored for less than or equal to 7 days at 4 C., the quantity of the bacterial colonies at the seventh day is already more than 7 log, i.e., the chicken has a trend of going bad; and after the chicken is packaged by utilizing the photocatalytic packaging film and processed by the plasma, the chicken can be stored for 14 days at 4 C., thus being twice of the control group. The surface color change of the chicken in the storage process is as shown in table 3. After the chicken is processed by the plasma and then is stored at 4 C., the surface color of the chicken is not changed, it shows that the combination of the plasma and the photocatalytic film can effectively prolong the storage period of the chicken, and the storage period is twice of the chicken packaged by utilizing the ordinary packaging film.