Freshness indicator for pork quality control

Abstract

The present invention relates to a highly visible freshness gas indicator by which the freshness of pork can be easily determined with the naked eye. A food packaging material including the freshness gas indicator according to the present invention makes it possible to determine the freshness of pork with the naked eye without opening the packaging material, and thus has the excellent effect of enabling non-destructive quality control from the initial stage of product distribution without complicated processes such as physicochemical analysis or instrumental analysis.

Description

Freshness indicator for pork quality control

[0001] The present invention relates to a freshness gas indicator that can visually confirm the freshness of pork.

[0002] Recently, consumers have increasingly considered safety and quality when purchasing food, and food safety has become increasingly important in food distribution and consumption. Consequently, new packaging concepts that provide consumers with information on food quality have become a key issue in food distribution and the food industry. Consequently, the need for packaging technologies capable of indicating quality levels has emerged to enhance food hygiene and safety and increase consumer trust. Freshness indicators, located inside food packaging, detect and indicate food spoilage in real time. These indicators work by detecting metabolites produced during food spoilage and indicating changes in quality through changes in color. Chemical substances such as oxygen, carbon dioxide, volatile basic nitrogen, organic acids, and ethanol are known as food quality indicators. Freshness indicators enable easy monitoring of food quality through direct visual changes in dyes caused by increases and decreases in these substances.

[0003] Meanwhile, in modern diets, annual per capita pork consumption in Korea is very high, approaching 30kg. Pork's high moisture and protein content makes it prone to spoilage during storage. Therefore, ensuring the quality and safety of pork during distribution and storage is crucial.

[0004] As pork deteriorates, substances such as L-carnitine, choline, and lecithin produce volatile basic nitrogen (VBN) through microbial and enzymatic reactions. These VBN compounds, including ammonia, trimethylamine, and dimethylamine, are collectively referred to as total volatile basic nitrogen (TVB-N), and this is used as a quality indicator for meat. The formation of VBN creates an alkaline environment in the headspace of the packaging container, and acidic pH indicators can react with this environment to cause a color change. Therefore, a freshness gas indicator utilizing a pH indicator that changes color in response to VBN can be applied to pork packaging. This has the potential to enhance consumer trust by allowing them to intuitively recognize storage conditions and quality during distribution and storage. However, the practical application of technology capable of indicating quality status on pork packaging is currently very limited. Therefore, a freshness gas indicator that sensitively detects volatile basic nitrogen generated by microbiological and physicochemical changes during the storage and preservation of pork for quality control purposes is needed.

[0005] The present invention aims to provide a freshness gas indicator for pork.

[0006] The present invention aims to provide a food packaging material including a freshness gas indicator for pork.

[0007] The purpose of the present invention is to provide a method for determining the freshness of pork.

[0008] 1. A freshness gas indicator for pork, comprising: a volatile basic nitrogen gas sensor unit including a mixed indicator of methyl orange and bromocresol green; a protective film laminated on one surface of the volatile basic nitrogen gas sensor unit; and a porous breathable sheet laminated on the other surface of the volatile basic nitrogen gas sensor unit.

[0009] 2. A freshness gas indicator for pork, wherein in the above 1, the methyl orange and bromocresol green are mixed in a volume ratio of 1:0.5 to 4.

[0010] 3. In the above 1, the volatile basic nitrogen gas sensor unit further contains hydrogen chloride, a freshness gas indicator for pork.

[0011] 4. A freshness gas indicator for pork containing 0.01 to 1.0 wt% of the hydrogen chloride based on the mixed indicator of methyl orange and bromocresol green in the above 3.

[0012] 5. A freshness gas indicator for pork, wherein the porous breathable sheet in the above 1 includes a PTFE (hydrophobic polytetrafluoroethylene) filter or a PDMS (hydrophobic Polydimethylsiloxane) filter.

[0013] 6. A freshness gas indicator for pork, wherein in the above 1, the protective film and the porous breathable sheet are thermally bonded to the volatile basic nitrogen gas sensor section.

[0014] 7. In the above 1, the volatile basic nitrogen gas sensor part is manufactured by a method including: 1) a step of preparing a polymer solution by dissolving cellulose acetate in a solvent at a ratio of 1 to 10% (v / v) and adding glycerol; 2) a step of adding a methyl orange solution and a bromocresol green solution at a ratio of 1:0.5 to 4 to the polymer solution; 3) a step of adding hydrogen chloride to the solution of step 2); and 4) a step of coating or absorbing the solution of step 3 onto a filter paper and then drying it.

[0015] 8. A freshness gas indicator for pork, wherein the methyl orange solution and bromocresol green solution in the above 7 are dissolved in a solvent at a ratio of 0.01 to 1% (w / v), respectively.

[0016] 9. Food packaging material comprising any one of the freshness gas indicators for pork 1 to 8 above.

[0017] 10. A method for determining the freshness of pork, comprising the step of calculating a color change value (ΔE) from any one of the pork freshness gas indicators 1 to 8 above.

[0018] 11. A method for determining the freshness of pork, wherein in the above 10, if the color change value (ΔE) of the freshness gas indicator for pork exceeds 23.0, the freshness is determined to have decreased.

[0019] The freshness gas indicator of the present invention has excellent visibility, allowing the freshness of pork to be easily determined with the naked eye.

[0020] The freshness gas indicator of the present invention has excellent visibility, allowing the initial spoilage point of pork to be easily identified with the naked eye.

[0021] The food packaging material including the freshness gas indicator of the present invention is excellent in that it enables quality control from the initial stage of product distribution without complex processes such as non-destructive physicochemical analysis or instrumental analysis, as it can visually determine the freshness of pork without opening the packaging material.

[0022] FIG. 1 is a diagram showing a packaging container (120) for pork (130) with a freshness gas indicator (110) attached according to one embodiment.

[0023] FIG. 2 is a diagram showing the configuration of a freshness gas indicator in which an adhesive portion (100); a protective film (200); a gas sensor portion (300); and a porous breathable sheet (400) are sequentially laminated according to one embodiment.

[0024] FIG. 3 is a block diagram showing a method for manufacturing a gas sensor unit (300) laminated on a freshness gas indicator (110) according to one embodiment.

[0025] ① of FIG. 4 is a diagram showing the color change of a gas sensor part manufactured without adding hydrogen chloride according to one embodiment. Despite the value ranging from an initial ΔE of 0.00 to ΔE of 15.21 over 48 hours of reaction with volatile basic nitrogen, the gas sensor part remained only in a dark and deep color without any noticeable color change.

[0026] ② of FIG. 4 is a diagram showing the color change of a gas sensor unit (300) manufactured by adding hydrogen chloride according to one embodiment). The gas sensor unit (300) initially had a bright pink color in the range of ΔE 0.00 to ΔE 23.00, but as the reaction time with volatile basic nitrogen passed and the color change value (ΔE) exceeded ΔE 23.0, it changed to a green color.

[0027] Fig. 5 is a diagram showing the color change and color change value (ΔE) of the freshness gas sensor unit (300) according to the trimethylamine (TMA) concentration according to one embodiment. When the TMA concentration is 10 mg% or less, the color is a bright pink series, and when the TMA concentration reaches 20 mg%, it is a dark green with a ΔE of 33.86.

[0028] Figure 6 is a diagram showing the color change value (ΔE) for the total microbial count (TBC) of the freshness gas sensor unit (300) according to one embodiment. The coefficient of determination (R), which is the proportional variation of the response variable y (ΔE value of the gas sensor unit) to the independent variable x (total microbial count) of the relational expression y = 7.805x-27.549 2 ) shows a high relationship strength between the total microbial count (TBC) and the color change value (ΔE) at 0.9252.

[0029] Fig. 7a is a diagram showing color changes and total volatile base nitrogen (TVB-N) concentration changes according to storage period under 25°C conditions after attaching a freshness gas indicator (110) to the inside of a pork packaging material according to one embodiment. After 18 hours, the TVB-N concentration exceeded 15 mg%, exhibited a ΔE of 23.1, and turned green, indicating a decline in freshness. After 30 hours, the TVB-N concentration exceeded 20 mg%, exhibited a ΔE of 33.06, and turned dark green, indicating the progression of spoilage.

[0030] FIG. 7b is a diagram showing color changes and total volatile base nitrogen (TVB-N) concentration changes according to storage period under 4°C conditions after attaching a freshness gas indicator (110) to the inside of a pork packaging material according to one embodiment. After 5 days, the TVB-N concentration exceeded 15 mg% and the color changed to green, indicating a decline in freshness. After 8 days, the TVB-N concentration exceeded 20 mg%, showing a ΔE of 28.37 and a dark green color, indicating the progression of spoilage.

[0031] FIG. 8a is a diagram showing color changes and total microbial count (TBC) concentration changes according to storage period under 25°C conditions after attaching a freshness gas indicator (110) to the inside of a pork packaging material according to one embodiment. After 18 hours, the TBC concentration reached 7 log CFU / g, exhibiting a ΔE of 23.1 and discoloration to green, indicating a decline in freshness. After 24 hours, the TBC concentration exceeded 7 log CFU / g, exhibiting a ΔE of 28.71 and discoloration to dark green, indicating the progression of spoilage.

[0032] FIG. 8b is a diagram showing color changes and total microbial count (TBC) concentration changes according to storage period under 4°C conditions after attaching a freshness gas indicator (110) to the inside of a pork package according to one embodiment. After 5 days, the TBC concentration exceeded 7 log CFU / g and turned green, indicating a decline in freshness. After 8 days, the TVB-N concentration exceeded 20 mg%, showed a ΔE of 28.37, and turned green, indicating the progression of spoilage.

[0033] Figure 9a is a diagram showing color and pH changes according to storage period under 25°C conditions after attaching a freshness gas indicator (110) to the inside of a pork package according to one embodiment. After 18 hours, the pH exceeded 6.1, exhibited a ΔE of 23.1, and discoloration to a greenish tone indicated a decline in freshness. After 30 hours, the pH exceeded 6.3, exhibited a ΔE of 33.06, and discoloration to a dark green tone indicated the progression of spoilage.

[0034] Figure 9b is a diagram showing color changes and pH changes according to storage period under 4°C conditions after attaching a freshness gas indicator (110) to the inside of a pork package according to one embodiment. After 5 days, the pH exceeded 6.1 and the color changed to green, indicating a decline in freshness. After 6 days, the pH exceeded 6.3, showing a ΔE of 26.34 and a dark green color, indicating the progression of spoilage.

[0035] Figure 10(A) is a diagram showing color changes and the time of initial spoilage according to the storage period under conditions of 25°C after attaching a freshness gas indicator (110) to the inside of a pork package according to one embodiment. After 18 hours, the color changes to green, indicating the beginning of initial spoilage.

[0036] Figure 10(B) is a diagram showing color changes and the time of initial spoilage according to the storage period under 4°C conditions after attaching a freshness gas indicator (110) to the inside of a pork package according to one embodiment. After 5-6 days, the color changes to green, indicating the beginning of initial spoilage.

[0037] The present invention relates to a freshness gas indicator for pork.

[0038] The freshness gas indicator of the present invention provides the effect of easily and quickly predicting the freshness of pork according to the storage temperature and storage period, the point at which initial spoilage begins, and the changes in the progression of spoilage with the naked eye.

[0039] Referring to Fig. 1, a freshness gas indicator (110) can be attached to the upper portion (headspace) of a packaging container (120) and used to check the freshness status of pork (130). More specifically, the quality status of pork can be predicted in real time by visually checking the color change of the freshness gas indicator (110).

[0040] The freshness gas indicator (110) can sensitively detect volatile basic nitrogen generated by microbiological and physicochemical changes depending on the condition of pork (130) inside the packaging container.

[0041] The freshness gas indicator (110) can display a color change by reflecting changes in the hydrogen potential (pH), total bacterial count (TBC), and total volatile basic nitrogen (TVB-N) according to the concentration of volatile basic nitrogen generated in the packaging container.

[0042] TVB-N is a measure of the total amount of nitrogen compounds produced during the breakdown of proteins and amines, and is an indicator used to evaluate the freshness of fish, seafood, and meat. In particular, volatile inorganic nitrogen such as ammonia, dimethylamine, and trimethylamine significantly affect sensory characteristics. TVB-N can be measured using the micro-diffusion method (Conway method). The TVB-N concentration of fresh pork is 10-15 mg / 100 g or less, and if it exceeds 15 mg / 100 g, freshness decreases and early spoilage may begin, and if it exceeds 20 mg / 100 g, spoilage can be considered advanced.

[0043] pH indicates the acidity of meat. Fresh meat is generally slightly acidic, but as it decomposes, the pH can approach neutrality. While meat is alive, its pH is neutral. After death, the pH decreases due to the production of lactic acid and phosphoric acid. Over time, the pH increases due to reactions with enzymes secreted by microorganisms and various nitrogen compounds produced by the breakdown of proteins within the meat. Fresh beef typically has a pH of 5.4 to 6.0, while fresh pork ranges from 5.5 to 6.1.

[0044] TBC is a factor that increases pH and can be used as an indicator of meat freshness. A lower TBC value indicates freshness, while a higher TBC value indicates a higher level of microbial contamination and spoilage.

[0045] A freshness gas indicator (110) comprises a volatile basic nitrogen gas sensor unit (300) including a mixed indicator of methyl orange and bromocresol green; a protective film (200) laminated on one surface of the volatile basic nitrogen gas sensor unit; and a porous breathable sheet (400) laminated on the other surface of the volatile basic nitrogen gas sensor unit, thereby enabling immediate detection of changing TVB-N, pH, or TBC concentrations inside a pork packaging material.

[0046] Referring to Fig. 2, the freshness gas indicator (110) includes a protective film (200) and a porous breathable sheet (400) laminated with a gas sensor section (300) interposed therebetween. In addition, it includes an adhesive section (100) laminated on the other side of the protective film (200) so that it can be attached to the inside of a pork packaging container.

[0047] The gas sensor unit (300) may include a pH indicator capable of detecting TVB-N, pH, or TBC concentration and indicating a color change. The pH indicator may be coated or absorbed onto the substrate of the gas sensor unit (300), but is not limited thereto.

[0048] The gas sensor unit (300) may include a pH indicator mixed with methyl orange and bromocresol green. Methyl orange and bromocresol green have excellent visibility, visually indicating color changes according to the freshness of pork. Methyl orange is red below pH 3.1 and turns yellow when pH exceeds 4.4. Bromocresol green is yellow below pH 3.8 and changes color to blue when pH exceeds 5.4. Since each indicator has a different pH color change range, the addition ratio of the indicator can be adjusted according to the appropriate pH of the target food.

[0049] The gas sensor unit (300) may include an indicator mixed with methyl orange and bromocresol green, preferably in a volume ratio of 1:1 to 3, more preferably 1:1.5 to 2.5. Within the above ratio range, the changing pH of the pork can be immediately reflected, clearly indicating a color change.

[0050] In one embodiment, the gas sensor unit (300) includes an indicator mixed with methyl orange and bromocresol green in a 1:2 ratio.

[0051] In the present invention, the gas sensor unit (300) may further include hydrogen chloride. By including hydrogen chloride, the initial color of the methyl orange and bromocresol green mixed indicator is maintained in an acidic state, and when reacted with basic volatile basic nitrogen, the color difference is greatly increased, thereby providing improved visibility.

[0052] The gas sensor unit (300) may contain 0.01 to 1.0 wt% of hydrogen chloride based on a mixed indicator of methyl orange and bromocresol green. If the amount of hydrogen chloride added is large, the rate at which the pH increases due to the volatile basic nitrogen reaction slows down, so it is important to adjust the amount of hydrogen chloride added depending on the target food. When applied to pork, hydrogen chloride is preferably added in an amount of 0.1 to 0.8 wt%, more preferably 0.2 to 0.6 wt%, based on a mixed indicator of methyl orange and bromocresol green, so that changes in the freshness of the pork can be quickly reflected.

[0053] In one embodiment, the gas sensor unit comprises 0.5 wt% hydrogen chloride based on a mixed indicator of methyl orange and bromocresol green.

[0054] The gas sensor unit (300) may further include a polymer solution for chemical resistance. The polymer solution may be a solution of cellulose nitrate, cellulose propionate, hydroxypropyl cellulose, or hydroxypropylmethylcellulose dissolved in acetone. For example, cellulose acetate may be dissolved in a volume ratio (v / v) of 1 to 20%, 1.5 to 19%, 1.5 to 17%, 1.5 to 15%, 2 to 15%, 2 to 12%, 2.5 to 12%, 2.5 to 10%, 2.5 to 7.5%, or 3 to 7% relative to acetone, but is not limited thereto.

[0055] The gas sensor unit (300) can mix 65 to 75% (v / v) of methyl orange and bromocresol green mixed indicator based on 100% (v / v) of the polymer solution.

[0056] The gas sensor unit (300) may further include a plasticizer for flexibility and processability. Examples of the plasticizer include, but are not limited to, glycerol.

[0057] The gas sensor unit (300) can be manufactured by a method including: 1) preparing a polymer solution by dissolving cellulose acetate in a solvent at a ratio of 1 to 10% (v / v) and adding glycerol; 2) adding a methyl orange solution and a bromocresol green solution at a ratio of 1:0.5 to 4 to the polymer solution; 3) adding hydrogen chloride to the solution of step 2); and 4) coating or absorbing the solution of step 3 onto a filter paper and then drying it.

[0058] In step 2), the methyl orange solution and bromocresol green solution may be dissolved in the solvent at a ratio of 0.01 to 1% (w / v), respectively.

[0059] In steps 1) and 2), the solvent may be a ketone solvent such as acetone, butanone, cyclohexanone, isophorone, tetralone, acetylacetone, etc.; a chlorine solvent such as chloroform, 1,2-dichloroethane, chlorobenzene, etc.; an ether solvent such as dioxane; an aromatic hydrocarbon solvent such as toluene, xylene, etc.; an aliphatic hydrocarbon solvent such as n-hexane, n-heptane, n-octane, n-nonane, n-decane, etc.; an ester solvent such as ethyl acetate, butyl acetate, ethyl cellosolve acetate, etc.; a polyhydric alcohol such as 1,2-hexanediol and its derivatives; an alcohol solvent such as methanol, ethanol, etc.; a sulfoxide solvent such as dimethyl sulfoxide, etc. And amide solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, etc. can be used.

[0060] Step 3) may contain 0.01 to 1.0 wt% of hydrogen chloride based on a mixed indicator of methyl orange and bromocresol green.

[0061] In step 4), the filter paper may be used without limitation as long as it can be coated or absorbed with the polymer solution including the methyl orange solution and bromocresol green solution, such as paper, cloth, and polymer resin.

[0062] The protective film (200) can enhance visibility by physically and chemically protecting the gas sensor unit (300) from the external environment while transparently reflecting color changes in the gas sensor unit (300). Since the gas sensor unit (300) may be deformed by ultraviolet rays or oxygen in the external environment, the protective film (200) can be composed of a film with high gas and ultraviolet ray blocking properties and visibility. The above film may be made of any material known in the art without limitation, and examples thereof include ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), polystyrene (PS), polyvinyl alcohol (PVA), oriented polypropylene (OPP), oriented nylon (ONy), polyethylene terephthalate (PET), polyglycolic acid (PGA), PET composites, polyethylene (PE), polypropylene (PP), polyamide (PA), polycarbonate (PC), polydihydroferulic acid (PHFA), polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), epoxy, polyimide (PI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), etc.

[0063] The protective film (200) can improve its external gas and ultraviolet ray blocking function through coating. The coating may be a wet coating, a dry coating, an organic / inorganic laminated coating, etc.

[0064] The protective film (200) can be laminated on one side of the gas sensor unit (300), and can be laminated on another side of the gas sensor unit (300) other than the side on which the porous breathable sheet (400) is laminated.

[0065] The porous breathable sheet (400) can be made of a material that has high gas permeability while blocking moisture. Accordingly, it prevents moisture and foreign substances generated during pork storage from coming into contact, thereby preventing deterioration of the gas sensor unit (300). In addition, it allows volatile basic nitrogen gas to pass through, thereby inducing a reaction with the pH indicator of the gas sensor unit (300), thereby maintaining color change sensitivity.

[0066] The porous breathable sheet (400) may be hydrophobic. This may be achieved by coating a hydrophobic polymer on the sheet or by electrospinning or other methods. The hydrophobic polymer may include a PTFE (hydrophobic polytetrafluoroethylene) filter paper or a PDMS (hydrophobic polydimethylsiloxane) filter paper.

[0067] In one embodiment, the porous breathable sheet (400) includes a PTFE-D (Hydrophobic polytetrafluoroethylene) filter paper.

[0068] The porous breathable sheet (400) can be laminated on one side of the gas sensor unit (300), and can be laminated on another side of the gas sensor unit (300) other than the side on which the protective film (200) is laminated. The lamination can be performed by thermal bonding.

[0069] The adhesive portion (100) can be used for adhesion to food packaging material or adhesion between each layer.

[0070] The protective film and the porous breathable sheet can be thermally bonded to the volatile basic nitrogen gas sensor portion.

[0071] In another aspect, the present invention provides a food packaging material including a freshness gas indicator (110) for pork.

[0072] The food packaging material may be any one selected from the group consisting of a label, an envelope, a wrap, and a container, but is not limited thereto. The freshness gas indicator (11) may be attached to the upper or side portion inside the food packaging material according to an appropriate selection by a person skilled in the art. The freshness gas indicator (110) may be attached to the upper or side portion inside the food packaging material so that the surface on which the porous breathable sheet (400) is laminated faces the contents, i.e., pork.

[0073] The present invention provides a method for determining pork freshness, comprising the step of calculating a color change value (ΔE) from a freshness gas indicator (110) in another aspect.

[0074] In the present invention, a method for judging pork freshness may include a step of attaching a freshness gas indicator (110) to the inside of a pork packaging material such that the surface on which a porous breathable sheet (400) is laminated faces the pork; and a step of calculating a color change value (ΔE) from the freshness gas indicator (110).

[0075] Color change values ​​(ΔE) can be measured using color measurement equipment such as a colorimeter or spectrophotometer, but are not limited thereto.

[0076] The color change value (ΔE) is a value comparing the difference between two colors using the following mathematical formula 1 according to the CIELAB color coordinates established by the CIE (International Commission on Illumination).

[0077] [Mathematical Formula 1]

[0078]

[0079] In mathematical expression 1, L represents the brightness value, a represents the red-green axis value, and b represents the yellow-blue axis value. L0, a0, and b0 represent the initial L, a, and b values, respectively.

[0080] In the present invention, the method for judging the freshness of pork can be used to determine that pork is fresh if the color change value (ΔE) calculated from the freshness gas indicator (110) is ΔE 0.00 to ΔE 22.9.

[0081] In the present invention, the method for judging the freshness of pork can be such that if the color change value (ΔE) calculated from the freshness gas indicator (110) exceeds ΔE 23.0, it can be judged that the freshness of the pork has decreased. Alternatively, it can be judged that initial spoilage has begun.

[0082] In one embodiment, the gas indicator (110) changes color to a green color when the total volatile base nitrogen (TVB-N) concentration exceeds 15 mg% and the color change value (ΔE) exceeds 23.0.

[0083] In one embodiment, the gas indicator (110) changes color to a green color when the hydrogen ion concentration index (pH, potential of hydrogen) exceeds 6.1, and the color change value (ΔE) exceeds 23.0.

[0084] In one embodiment, the gas indicator (110) changes color to a green color when the total bacterial count (TBC) exceeds 6.5 Log CFU / g and the color change value (ΔE) exceeds 23.0.

[0085] In the present invention, the method for judging the freshness of pork can determine that spoilage of pork has progressed when the color change value (ΔE) calculated from the freshness gas indicator (110) exceeds ΔE 28.0.

[0086] In one embodiment, the gas indicator (110) changes color to a dark green color when the total volatile base nitrogen (TVB-N) concentration exceeds 20 mg% and the color change value (ΔE) exceeds 28.0.

[0087] In one embodiment, the gas indicator (110) changes color to a dark green color when the hydrogen ion concentration index (pH, potential of hydrogen) exceeds 6.2 to 6.3, and the color change value (ΔE) exceeds 28.0.

[0088] In one embodiment, the gas indicator (110) changes color to a dark green color when the total bacterial count (TBC) exceeds 7.0 Log CFU / g and the color change value (ΔE) exceeds 28.0.

[0089] Example

[0090] (1) Manufacturing of gas sensor unit

[0091] The method for manufacturing the gas sensor unit (300) included in the freshness gas indicator (110) of the present invention is as follows. Cellulose acetate is completely dissolved in 30 mL of acetone at a ratio of 5% (w / v). Then, glycerol is added in the same amount (w / w) as cellulose acetate and sufficiently dissolved to prepare a polymer solution. In addition, methyl orange and bromocresol green are each dissolved in ethanol (75%) at a volume ratio of 0.1% (w / v) to prepare an indicator solution. Thereafter, a total of 20 mL of methyl orange solution and bromocresol green solution are added to the polymer solution at a volume ratio of 1:2. In order to brighten the initial color of the gas sensor part (300) to increase visibility and to make it more sensitive to volatile basic nitrogen, 0.1 mL of 1N hydrogen chloride (HCl) was added, and then filter paper (pore size 8-12 ㎛) cut to a certain size (2 cm) was immersed in the completed solution and dried.

[0092]

[0093] (2) Manufacture of freshness gas indicators and food packaging materials containing the same

[0094] A hydrophobic PTFE-D filter paper larger in all directions than the size of the filter paper was adhered to one side of the gas sensor unit (300) manufactured by the method of Example (1) using a thermal bonding method. Then, PET was positioned as a protective film (200) on the other side of the gas sensor unit to which the PTFE-D filter paper was adhered. A freshness gas indicator (110) was manufactured by thermally bonding the PET film and the PTFE-D filter paper with the gas sensor unit (300) included in the middle through a laminating process.

[0095] An adhesive portion (100) was formed on the protective film (200) surface of the manufactured freshness gas indicator (110), and the porous breathable sheet (400) surface with PTFE-D filter paper attached was positioned so that it faces the pork, and then attached to the upper side of the inside of the packaging material to produce a food packaging material.

[0096]

[0097] Experimental Example 1: Confirmation of suitability of freshness gas indicator (110)

[0098] In the following experiments, the color change of the freshness gas indicator was measured three times repeatedly using a colorimeter (CM-2500d; Konica Minolta Inc., Tokyo, Japan), and the color change value (ΔE) was calculated according to the following mathematical equation 1. In mathematical equation 1, L represents the brightness value, a represents the red-green axis value, and b represents the yellow-blue axis value. L0, a0, and b0 represent the initial L, a, and b values, respectively.

[0099] [Mathematical Formula 1]

[0100]

[0101] The suitability of the gas sensor unit (300) can be determined by sequentially increasing the color change value (ΔE) and determining that the greater the change value, the greater the visibility.

[0102] (1) Confirmation of improved visibility by adding hydrogen chloride

[0103] Two types of gas sensor parts manufactured in the same manner as in Example (1) except that the addition of hydrogen chloride was different were applied to a freshness gas indicator and attached to the inside of pork packaging material, and the visibility was compared by checking the color change according to [Mathematical Formula 1] during the storage period at 25°C.

[0104] As a result, in the case of the freshness gas indicator (② of FIG. 4) including a gas sensor unit (300) manufactured by adding hydrogen chloride, the degree of change in color was distinct as storage time elapsed, and it was confirmed that visibility was greatly improved compared to the freshness gas indicator (① of FIG. 4) including a gas sensor unit manufactured without adding hydrogen chloride (FIG. 4).

[0105] More specifically, in the case of Fig. 4①, a color difference from ΔE 0.00 to ΔE 15.21 occurred from the initial 0 hour to 48 hours, and the color corresponding to each color change value (ΔE) maintained a similar dark color, so no distinct visible change was observed, whereas in the case of Fig. 4②, a large color difference from ΔE 0.00 to ΔE 37.86 was confirmed during the same period, and a distinct color change was observed from the initial bright pink color (ΔE = 0) to a dark dark green (ΔE = approximately 37.86) after 48 hours.

[0106]

[0107] (2) Performance verification of freshness gas indicator according to volatile basic nitrogen

[0108] After exposing the freshness gas indicator (110) manufactured in the example to a trimethylamine solution corresponding to volatile basic nitrogen in a concentration range of 0 to 25 mg%, the color change was confirmed and the color change value (ΔE) was obtained.

[0109] Referring to Fig. 5, the freshness gas indicator (110) clearly reflected a visible color change as the color change value (ΔE) increased significantly depending on the trimethylamine concentration. When the trimethylamine concentration was 10 mg% or less, it had a reddish color, and when the trimethylamine concentration reached 20 mg%, which is the meat spoilage standard, it showed a color difference of ΔE 33.86 and became dark green. As a result, it was confirmed that the freshness gas indicator (110) changed to a color that was clearly different from the color before reaching the spoilage standard, so that the freshness of pork could be easily distinguished with the naked eye (Fig. 5).

[0110]

[0111] (3) Confirmation of the performance of the freshness gas indicator according to the total number of microorganisms

[0112] In order to confirm the reflection of color change of the freshness gas indicator (110) according to the degree of spoilage when applied to pork, the relationship between the color change value (ΔE) and the change in total microbial count (TBC) was analyzed.

[0113] First, a freshness gas indicator (110) was attached to the inside of the pork packaging material and stored at 25℃. As a result of checking the measured total microbial count (TBC) and color change value (ΔE), the color change value (ΔE) also increased according to the increase in the total microbial count (TBC), clearly reflecting the degree of contamination due to microbial proliferation (Table 1).

[0114] Total microbial count (TBC) Color change value (ΔE) 3.80 4.75 14.36 6.18 17.47 6.85 23.17 04 28.7 17.5 13 3.06

[0115] Next, the coefficient of determination (R 2 ) value was used to evaluate the strength of the relationship between the color change value (ΔE) and the total microbial count (TBC), and the coefficient of determination was 0.9252, confirming that the freshness gas indicator (110) can accurately reflect the change in microbial concentration that occurs during storage of pork (Fig. 6).

[0116]

[0117] Experimental Example 2: Performance Verification of Freshness Gas Indicator (110)

[0118] In order to optimize the freshness gas indicator (110) of the present invention, pork samples were stored at 4°C and 25°C, and the total volatile base nitrogen (TVB-N), pH value, and total microbial count (TBC), which are indicators of the degree of spoilage of pork, were measured over time, and the color change of the freshness gas indicator (110) was recorded using a photographic image and a colorimeter.

[0119]

[0120] (1) Performance verification of freshness gas indicator according to volatile basic nitrogen

[0121] After attaching a freshness gas indicator (110) to the inside of the pork packaging, the total volatile basic nitrogen (TVB-N) concentration and the corresponding color change value (ΔE) were checked according to the storage time under conditions of 4°C and 25°C. The total volatile basic nitrogen (TVB-N) concentration was measured by the microdiffusion method using a Conway dish.

[0122] Pork samples were taken, ground, and 5 g was collected. 25 mL of distilled water was added, homogenized with a homogenizer, and extracted for 30 minutes. The solution was centrifuged at 2000 rpm for 15 minutes, and the supernatant was used as the test solution. After filtering the test solution through filter paper (Whatman NO. 1), 1 mL of 0.01 N sulfuric acid was added to the inner chamber of the Conway dish, and 1 mL of the test solution was added to the outer chamber. A small amount of sealant was applied to the lid, 1 mL of a saturated potassium carbonate solution was added, and the lid was closed to seal it. The test solution in the outer chamber of the Conway unit was mixed with the potassium carbonate solution to allow it to react, and the solution was left in an incubator at 25°C for 60 minutes. After that, 10 μL of Brunswik's indicator was added to the inner chamber, and the titration was performed with a 0.01 N sodium hydroxide solution, and the average value of two measurements was obtained. A blank test was conducted in the same manner using distilled water instead of the test solution, and the total volatile base nitrogen (TVB-N) concentration was calculated according to the following mathematical equation 2.

[0123] [Equation 2]

[0124] VBN value (mg%) = [(Test solution titration amount - Blank test titration amount) X (Titer of 0.01 N sulfuric acid solution) X 28.014 X 100] / Sample amount collected (g)

[0125] Referring to Fig. 7, the total volatile base nitrogen (TVB-N) production amount of the pork sample increased over time during the storage period, exceeding the spoilage standard of 20 mg% at 30 hours of storage at 25°C (Fig. 7a) and at 8 days of storage at 4°C (Fig. 7b). At this time, the color change value (ΔE) of the freshness gas indicator (110) exceeded 28 to 30 and then changed to dark green.

[0126]

[0127] (2) Verification of the performance of freshness gas indicators based on total microbial counts

[0128] After attaching a freshness gas indicator (110) to the inside of the pork packaging, the change in total microbial count (TBC) according to the number of days of storage under 4℃ and 25℃ conditions and the color change value (ΔE) of the freshness gas indicator were obtained. The total microbial count (TBC) generated during the storage period of the pork sample was measured using a bacteriological freshness determination method.

[0129] 10 g of pork was placed in a sterile bag with 90 mL of sterile saline (Saline 0.85%) and homogenized for 2 minutes using an automatic homogenizer. The resulting solution was used as a test solution. The test solution was serially diluted 10-fold with sterile saline, and 1 mL of each dilution was inoculated onto two sheets of dry film medium for general bacterial measurement, and cultured at 35°C for 48 hours. After culture, the number of colonies formed on the medium was counted, and the average number of colonies was multiplied by the dilution factor to express it as Log CFU / g.

[0130] Referring to Fig. 8, as the storage period of pork passed, the total microbial count (TBC) increased, and exceeded the recommended microbial standard of 7 Log CFU / g after 18 hours of storage at 25°C (Fig. 8a) and after 8 days at 4°C (Fig. 8b). At this time, the color change value (ΔE) of the freshness gas indicator (110) exceeded 23 to 28, gradually turning green, and then changing to dark green.

[0131]

[0132] (3) Performance verification of freshness gas indicator according to hydrogen ion concentration index

[0133] A freshness gas indicator (110) was attached to the inside of the pork packaging material, and the change in pH value of the pork sample and the color change value (ΔE) of the freshness gas indicator (110) according to the storage period were obtained under the conditions of 4°C and 25°C.

[0134] Pork samples were taken, ground, and 5 g were collected. 20 mL of distilled water was added, homogenized using a homogenizer, and centrifuged at 2000 rpm for 15 minutes. The pH of the supernatant was measured three times using a pH meter (Orion 3-Star Meter™; Thermo Fisher Scientific Inc.).

[0135] Referring to Fig. 9, the pH of the pork sample initially showed a decreasing tendency and then increased over the storage period, exceeding the spoilage standard of 6.3 at 30 hours of storage at 25°C (Fig. 9a) and at 6 days at 4°C (Fig. 9b). At this time, the color change value (ΔE) of the freshness gas indicator (110) exceeded 28 to 30, discolored to green, and then changed to dark green.

[0136]

[0137] (4) Color change value of the fresh gas indicator at the initial stage of pork spoilage

[0138] A freshness gas indicator (110) was attached to the inside of the pork packaging, and the color change value (ΔE) at the initial spoilage point was determined based on the color change according to the degree of change in total volatile base nitrogen (TVB-N), total microbial count (TBC), and pH of pork stored at 4°C and 25°C.

[0139] Referring to Fig. 10, the color change value (ΔE) of the freshness gas indicator (110) increases steadily over time at a room temperature of 25°C (Fig. 10a), and at the initial spoilage point after 18 hours, the color change value (ΔE) exceeds 23 and changes to a green color, and after 30 hours of spoilage, the color changes to a dark green. In the case of the actual distribution and storage temperature of 4°C (Fig. 10b), the color change value (ΔE) exceeds 23 and changes to a green color, and after 8 days of spoilage, the color changes to a dark green.

[0140] As a result, it was confirmed that the freshness gas indicator (110) according to one embodiment can quickly reflect the initial spoilage point according to the storage temperature and storage period of pork, and can determine the decline in freshness of pork when the color change value (ΔE) exceeds 23 or begins to turn green.

Claims

1. A freshness gas indicator for pork, comprising: a volatile basic nitrogen gas sensor unit including a mixed indicator of methyl orange and bromocresol green; a protective film laminated on one surface of the volatile basic nitrogen gas sensor unit; and a porous breathable sheet laminated on the other surface of the volatile basic nitrogen gas sensor unit.

2. A freshness gas indicator for pork according to claim 1, wherein the methyl orange and bromocresol green are mixed in a volume ratio of 1:0.5 to 4.

3. A freshness gas indicator for pork according to claim 1, wherein the volatile basic nitrogen gas sensor unit further includes hydrogen chloride.

4. A freshness gas indicator for pork, comprising 0.01 to 1.0 wt% of hydrogen chloride based on a mixed indicator of methyl orange and bromocresol green according to claim 3.

5. A freshness gas indicator for pork according to claim 1, wherein the porous breathable sheet includes a PTFE (hydrophobic polytetrafluoroethylene) filter or a PDMS (hydrophobic Polydimethylsiloxane) filter.

6. A freshness gas indicator for pork according to claim 1, wherein the protective film and the porous breathable sheet are thermally bonded to the volatile basic nitrogen gas sensor unit.

7. In claim 1, the volatile basic nitrogen gas sensor unit is a freshness gas indicator for pork manufactured by a method including: 1) a step of dissolving cellulose acetate in acetone at a ratio of 1 to 10% (v / v); 2) a step of adding glycerol to the solution of step 1) to prepare a polymer solution; 3) a step of adding a methyl orange solution and a bromocresol green solution to the polymer solution at a ratio of 1:1 to 3; 4) a step of adding hydrogen chloride to the solution of step 3); and 5) a step of coating or absorbing the solution of step 4) onto a filter paper and drying it.

8. A freshness gas indicator for pork according to claim 7, wherein the methyl orange solution and the bromocresol green solution are dissolved in a solvent at a ratio of 0.01 to 1% (w / v), respectively.

9. A food packaging material comprising a freshness gas indicator for pork according to any one of claims 1 to 8.

10. A method for determining the freshness of pork, comprising the step of calculating a color change value (ΔE) from a freshness gas indicator for pork of any one of claims 1 to 8.

11. A method for determining the freshness of pork, wherein the freshness is determined to have decreased when the color change value (ΔE) of the freshness gas indicator for pork exceeds 23.0 in claim 10.

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