KR20230170395A - Freshness indicator - Google Patents

Abstract

The present invention relates to a freshness indicator that can predict the freshness of food by measuring the amount of volatile base nitrogen (VBN) generated from food. By checking the color change of the gas sensor unit according to the amount of volatile base nitrogen, the present invention relates to a non-invasive and fast food safety indicator. The freshness of can be predicted.

Description

FRESHNESS INDICATOR}

The present invention relates to a freshness indicator using volatile basic nitrogen (VBN) gas generated during the storage period of food.

As consumer interest in food quality and safety increases, an industry for intelligent and active packaging that provides information on the freshness of food is emerging. In particular, in the case of meat, deterioration begins due to microbial growth and reaction of autophagic enzymes during storage, and volatile basic nitrogen (VBN) is generated. Volatile basic nitrogen is one of the quality factors for determining the quality and freshness of food. With the increase in meat consumption, there is a growing tendency among consumers to prefer meat that is both good quality and fresh.

Accordingly, there is a need for technological research to analyze the amount of volatile basic nitrogen (VBN) generated during the storage process of fresh livestock meat and provide freshness information on fresh livestock meat to distributors and consumers to easily check quality and safety. This is coming to the fore.

Korean Patent No. 2178075

The present invention provides a freshness indicator and a freshness indicator for detecting the amount of volatile basic nitrogen (VBN) generated during the storage process of food and visually displaying the freshness correlated thereto so that consumers and distributors can easily determine the freshness of the food. The purpose is to provide food packaging materials containing this.

1. A freshness indicator including a gas sensor unit with a mixed layer of bromocresol green and bromocresol purple.

2. A freshness indicator in 1 above, where the food subject to the freshness indicator is beef or pork.

3. The freshness indicator of 1 above, wherein the food subject to the freshness indicator is beef, and the mixed layer contains bromocresol green and bromocresol purple in a weight ratio of 1:1 to 1:2.

4. The freshness indicator of 1 above, wherein the mixed layer is coated on a substrate.

5. The freshness indicator according to 1 above, further comprising a membrane filter on the mixed layer.

6. The freshness indicator of 5 above, wherein the membrane filter is hydrophobic.

7. Food packaging material including the freshness indicator of any one of claims 1 to 6 on the side where the food is stored.

The freshness indicator of the present invention detects the concentration of volatile basic nitrogen (VBN) generated during the storage process of food and measures the freshness of the food in a non-destructive, visible way without complex processes such as physicochemical or instrumental analysis. It can be figured out.

Figure 1 shows the color change of a freshness indicator with six types of indicator combinations according to the number of days of food sample storage.

Hereinafter, the present invention will be described in detail.

The freshness indicator of the present invention includes a gas sensor unit having a mixed layer of bromocresol green and bromocresol purple.

Bromocresol Green and Bromocresol Purple are indicators that can indicate the presence or absence of volatile basic nitrogen (VBN) generated during the storage period of food through color changes. By providing a mixed layer, the gas sensor unit can sensitively detect and indicate even a small amount of volatile basic nitrogen, and exhibits a clear color change, providing excellent visibility.

The mixed layer of bromocresol green and bromocresol purple may be, for example, a coating layer of bromocresol green and bromocresol purple solutions. For example, this may be a coating of bromocresol green and bromocresol purple solutions on a substrate, or may be formed by absorbing the solution into the substrate or immersing the substrate in the solution. For example, when the substrate is immersed in a solution, the immersion time is, for example, 5 seconds to 60 minutes, 5 seconds to 30 minutes, 5 seconds to 15 minutes, 5 seconds to 10 minutes, 5 seconds to 5 minutes, 5 seconds. It may be from 3 minutes to 3 minutes, 5 seconds to 1 minute, 5 seconds to 30 seconds, 5 seconds to 15 seconds, 5 minutes to 30 minutes, 5 minutes to 20 minutes, or 5 minutes to 15 minutes, but is not limited thereto.

The substrate can be used without limitation as long as it can be coated or absorbed with bromocresol green and bromocresol purple solutions, for example, paper, cloth, polymer resin, etc.

For example, bromocresol green and bromocresol purple are 0.010 to 0.250%, 0.010 to 0.200%, 0.015 to 0.150%, 0.020 to 0.100%, 0.025 to 0.100%, 0.030 to 0.15%, and 0.040 to 0.100%, respectively, relative to the solvent. % , may be included in the solution at a weight ratio of 0.050 to 0.100%, but is not limited thereto. In addition, since the amount of volatile basic nitrogen (VBN) that can be detected can vary depending on the weight ratio, it can be appropriately selected depending on the type of food for which freshness is to be indicated. For example, the indication range for bromocresol green is pH 3.8-5.4, and the indication range for bromocresol purple is pH 5.2-6.8, so foods that generate large amounts of volatile basic nitrogen (e.g. pork belly parts) In the case of foods that produce a smaller amount of volatile base nitrogen (e.g. beef brisket), the content of bromocresol purple can be increased, and in the case of foods that generate a smaller amount of volatile basic nitrogen, the content of bromocresol purple can be reduced, etc. The weight ratio of Bromocresol Green and Bromocresol Purple can be adjusted to suit the characteristics.

To give a specific example, when the target food is beef, the weight ratio of bromocresol green and bromocresol purple may be 1:1 to 1:2. The beef part may be, for example, sirloin, but is not limited thereto.

Solvents for bromocresol green and bromocresol purple solutions can be used without limitation as long as they can dissolve these indicators, and include acetone, butanone, cyclohexanone, isophorone, tetralone, and acetyl Ketone-based solvents such as acetone (acetylacetone); Chlorine-based solvents such as chloroform, 1,2-dichloroethane, and chlorobenzene; Ether-based solvents such as dioxane; Aromatic hydrocarbon-based solvents such as toluene, xylene, and the like; Aliphatic hydrocarbon solvents such as n-hexane, n-heptane, n-octane, n-nonane, and n-decane; Ester solvents such as ethyl acetate, butyl acetate, and ethyl cellosolve acetate; polyhydric alcohols and derivatives thereof such as 1,2-hexanediol; Alcohol-based solvents such as methanol and ethanol; Sulfoxide-based solvents such as dimethyl sulfoxide; and amide-based solvents such as N-methyl-2-pyrrolidone and N,N-dimethylformamide may be used.

For chemical resistance of Bromocresol Green and Bromocresol Purple solutions, cellulose acetate, cellulose nitrate, cellulose propionate, hydroxypropyl cellulose, and hydroxy It may further include propylmethyl cellulose (hydroxypropylmethyl cellulose), etc. This is, for example, 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% relative to the solvent. , may be further included in a weight ratio of 3 to 7%, but is not limited thereto. Additionally, in order to adjust the color change sensitivity of the gas sensor unit, additives such as glycerol, polyethylene glycol, and dibutyl phthalate may be further included.

For example, the gas sensor unit may be manufactured by further including cellulose acetate in bromocresol green and boromocresol purple solutions and immersing the substrate in the solution. In this case, bromocresol green and bromocresol purple may be included in the solution at a weight ratio of 0.050 to 0.100%, respectively, and cellulose acetate may be included in a weight ratio of 2.5 to 7.5% relative to the solvent, and the substrate immersion time is 5 to 15 minutes. It can be manufactured as, but is not limited to this.

For the freshness indicator of the present invention, for example, the food subject to the freshness indicator may be livestock products. This may include, for example, but is not limited to beef (various parts such as tenderloin, sirloin, brisket, etc.) or pork (various parts such as pork belly, whole fat, sirloin, etc.).

The freshness indicator of the present invention may further include a membrane filter on the gas sensor unit.

By further including a membrane filter, the gas to the gas sensor can be transmitted to indicate freshness, while the color change sensitivity of the gas sensor can be maintained by reducing the contact of moisture, foreign substances, etc. to the gas sensor.

The membrane filter may be hydrophobic in terms of preventing moisture generated from food from diffusing into the gas sensor unit. This can be made hydrophobic by coating the filter with a hydrophobic polymer or by electrospinning. Hydrophobic polymers include polyethylene (PE), polyacrylonitrile, polyacrylate, polyacrylamide, polyurethane, polystyrene, epoxy, and polyvinyl chloride ( polyvinyl chloride, fluorocarbon polymer, polytetrafluoroethylene (PTFE), polydimethylsiloxane (PDMS), polyester, polyethylene terephathalate (PET), polybutylene polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene terephthalate glycol (PETG), polypropylene (PP), polyamide (PA)-6, poly It may be methyl methacrylate (PMMA), polyethyl methacrylate, polycarbonate (PC), polymethylpentene, etc. For example, hydrophobic membrane filters include PTFE + PE backing (polytetrafluoroethylene with polyethylene backing) membrane filter, pure PTFE (polyteterafluoroethylene) membrane filter, PTFE-D membrane filter (thick membrane), PTFE-J membrane filter (thin membrane), PTFE -It may be a membrane filter such as a T membrane filter (strong heat resistance), a PVDF (polyvinylidene fluoride) membrane filter, or a PVDF-D membrane filter (thick membrane).

The freshness indicator of the present invention may further include a protective film, an adhesive portion, etc.

The protective film serves to physically and chemically protect the gas sensor unit from the external environment. Since deformation may be applied to the gas sensor unit due to ultraviolet rays or oxygen in the external environment, the protective film prevents deformation of the gas sensor unit due to this environment.

The protective film may be composed of a film with high gas barrier properties and UV protection properties. The film may be made of materials known in the art without limitation, such as ethylene vinyl alcohol (EVOH), nylon (m-xylenediamine (MXDA) and adipic acid). condensation polymerization), polyvinylidene chloride (PVDC), polystyrene (PS), polyvinyl alcohol (PVA), oriented polypropylene (OPP), biaxially oriented nylon (ONy) ), polyethylene terephthalate (PET), polyglycolic acid (PGA), PET composite material with dispersed organically modified montomrillonite (OMMT), polyethylene (PE), polypropylene ( polypropylene, PP), SAN (styrene acrylonitrile copolymer) resin, ABS (acrylonitrile-butadiene-styrene) resin, expandable polystyrene (EPS), polymethyl methacrylate, polyamide (PA), Polycarbonate (PC), polydihydroferulic acid (PHFA), polybutylene terephthalate (PBT), polyvinyl chloride (PVC), polyurethane (PU), Modified polyphenylene oxide (MPPO), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), epoxy, Polyimide (PI), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), etc. can be used.

Gas and ultraviolet ray blocking functions can be improved by coating on polymer films of various materials. The coating may be wet coating, dry coating, organic/inorganic layered coating, etc. For example, wet coating includes PVDC coating, organic-inorganic nanocomposite coating, and acrylic acid-based resin coating, while dry coating includes physical vapor deposition (PVD) and chemical vapor deposition (CVD). .

For example, the protective film may be included on the gas sensor unit, and if a membrane film is included on the gas sensor unit, it may be included on the other side of the side to which the membrane filter is attached.

The adhesive portion can be used for adhesion to food packaging materials, adhesion between each layer, etc.

Additionally, the present invention relates to a food packaging material including the freshness indicator.

Food for measuring freshness generates volatile basic nitrogen (VBN) depending on the storage period, and the generated volatile basic nitrogen rises within the packaging material and can reach the freshness indicator attached to the top of the food. When the freshness indicator includes a membrane filter, the gas may pass through the membrane filter and reach the gas sensor unit, and the gas sensor unit may detect the gas and indicate a change in color. By recognizing this color change, the presence and amount of volatile basic nitrogen generated by the food can be known, so freshness can be visually confirmed.

The type of food subject to the freshness indicator may be livestock products, for example, beef (various parts such as tenderloin, sirloin, brisket, etc.) or pork (various parts such as pork belly, fat, sirloin, etc.).

When a membrane filter is further included among the freshness indicators included in the food packaging material, the freshness indicator may be included in the food packaging material with the membrane filter side facing toward the food.

Hereinafter, the present invention will be described in detail with reference to examples.

Example 1. Manufacturing of freshness indicator

The method of manufacturing the gas sensor part of the freshness indicator of the present invention is as follows. Cellulose acetate was added and dissolved in acetone at a ratio of 5% (w/v). Afterwards, glycerol and polyethylene glycol were added at a ratio of 20% (w/w) compared to the cellulose acetate content. Afterwards, bromocresol green and bromocresol purple were added at a ratio of 0.075% (w/v) and bromocresol purple at a ratio of 0.075% (w/v) to acetone to prepare a mixed polymer solution of bromocresol green and bromocresol purple.

The filter paper was immersed in this, dried at room temperature, and cut to a certain size to form a mixed layer of bromocresol green and bromocresol purple.

A hydrophobic membrane filter with a size larger in all directions than the size of the cut filter paper was attached to one side of the gas sensor unit manufactured by the above method using a thermal bonding method. Afterwards, a protection made of polyethylene terephthalate (PET) or biaxially oriented polypropylene (OPP) is applied to the other side of the gas sensor part to which the polytetrafluoroethylene (PTFE-D) hydrophobic membrane filter is attached. A freshness indicator was manufactured by placing the film and heat-sealing the protective film and the hydrophobic membrane with the gas sensor part in the middle through a laminating process.

Among the packaging materials that can contain food that generates volatile base nitrogen (VBN), a food packaging material was manufactured by attaching a freshness indicator to the upper side of the part where the food would be located, allowing the freshness of the packaged food to be known through the freshness indicator.

Example 2. Confirmation of performance of freshness indicator

In this example, the performance of the freshness indicator manufactured in Example 1 was confirmed for beef among foods. For beef samples, the amount of volatile basic nitrogen (VBN) generated during the storage period was measured, and a gas indicator equipped with various indicators was applied to check whether there was a color change.

1. Measurement of volatile basic nitrogen (VBN) generation in beef samples

(1) Experimental method

Beef, one of the livestock products, was stored in a packaging container at 4°C for a certain period of time and the volatile basic nitrogen generated was analyzed.

Beef was homogenized for 30 seconds using a blender, and 5 g was collected as a sample. 25 mL of distilled water was added to the collected sample and homogenized at 7000 rpm for 30 seconds using a homogenizer. Afterwards, the homogenate was filtered using filter paper. Distilled water was added until the filtrate reached 25 mL, and 20 μL of 5% sulfuric acid solution was added to serve as a test solution.

An airtight agent was applied to the Conway dish, 1 mL of test solution was added to one side of the outer chamber, and the cover was covered. Afterwards, the cover was slightly opened to the opposite side of the outer chamber, 1 mL of 0.01 N sulfuric acid solution was added to the inner chamber, and 1 mL of saturated K ₂ CO ₃ solution was added to the outer chamber on the opposite side of the test solution. After putting the cover on, the Conway dish was shaken back and forth and left and right to mix the test solution and K ₂ CO ₃ saturated solution well. Afterwards, it was left in an incubator set at 25°C for 1 hour. After 1 hour, 10 μL of Brunswik reagent was added to the inner chamber of the Conway dish, and then titrated with 0.01 N sodium hydroxide solution.

(2) Experiment results

Volatile basic nitrogen generated depending on the storage period was calculated using Equation 1. The analyzed volatile basic nitrogen content is shown in Table 1.

[Equation 1]

W: Test sample collection amount (g)

f: Titer of 0.01N sodium hydroxide

a: Test solution titration mL

b: blank test titration mL

2. Color change depending on the volatile base nitrogen concentration of various indicators

In addition to the mixture of bromocresol green and bromocresol purple used in the freshness indicator of the present invention, other indicators were used to produce a freshness indicator with the composition other than the indicator being the same as that of the indicator in Example 1, and then It was applied to packaging containers containing beef samples.

The indicators used are as follows: ① Methyl red 0.1% (w/v) ② Alizarin 0.1% (w/v) ③ Bromophenol blue 0.09% (w/v) and phenol red 0.06% (w/v) compared to acetone. Mixture of ④ Bromocresol Purple 0.1% (w/v) ⑤ Bromocresol Green 0.1% (w/v). The above five types of indicators were selected to have a pH range corresponding to a portion of the pH indicator range of 3.8 - 6.8 of the mixed solution of Bromocresol Green and Bromocresol Purple used in the present invention.

The results of calculating the color change (ΔE) of the freshness indicator by applying the freshness indicator prepared with the above five types of indicators to the packaging container containing the beef of Example 2-1 are shown in Table 2, and the color change As a result of visual comparison with the bromocresol green and bromocresol purple mixture of the present invention, it was confirmed that the indicator combination of the present invention clearly shows a color change depending on the storage period (Figure 1).

3. Color change of the gas sensor according to the storage period of beef

In manufacturing the gas sensor unit prepared in Example 1, the weight ratio of bromocresol green and bromocresol purple in the solution was set to 0.060, 0.075, and 0.090% compared to acetone, and the weight ratio of cellulose acetate was set to 5, 7, and 9% compared to acetone. A total of 18 indicator samples were produced by changing the solution and immersing the filter paper in the polymer solution for 10 seconds or 10 minutes.

The samples were attached to the packaging container containing the beef sample, and the color change (ΔE) according to the sample storage period was measured. The color change values were quantified and shown in Table 3.

This color change (ΔE) can vary depending on various conditions such as the type of livestock product, area, storage temperature, and storage time, and this value changes significantly as the concentration of volatile basic nitrogen (VBN) in the upper layer of the packaging container increases. (ΔE > 12) must be shown to confirm that it is suitable as a gas sensor unit.

G: Content ratio of bromocresol green and bromocresol purple contained in the polymer solution compared to acetone (0.060 - 0.090%)

CA: Cellulose acetate content ratio compared to acetone (5 - 9%)

S: When manufacturing the gas sensor unit, the filter paper was immersed in the polymer solution for 10 seconds.

M: When manufacturing the gas sensor unit, the filter paper was immersed in a polymer solution for 10 minutes.

From the above results, it was found that as the storage period passes, the concentration of volatile basic nitrogen in the upper layer of the food packaging increases, and the color of the gas sensor clearly changes (ΔE > 12).

Claims (7)

A freshness indicator comprising a gas sensor unit having a mixed layer of bromocresol green and bromocresol purple.
The freshness indicator according to claim 1, wherein the food subject to freshness indication is beef or pork.
The freshness indicator according to claim 1, wherein the food subject to freshness indication is beef, and the mixed layer contains bromocresol green and bromocresol purple in an amount ratio of 1:1 to 1:2.
The freshness indicator according to claim 1, wherein the mixed layer is coated on a substrate.
The freshness indicator of claim 1, further comprising a membrane filter on the mixed layer.
The freshness indicator of claim 5, wherein the membrane filter is hydrophobic.
A food packaging material including the freshness indicator of any one of claims 1 to 6 on the side where the food is stored.