KR20230170394A - 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 of 2018, the total domestic fishery production was 3,791 thousand tons (Korea Fisheries Society, 2019 Fisheries Yearbook). Among these, about 5% of the total supply of marine products is lost due to loss of freshness during transportation, processing, and distribution, from production to cooking. Therefore, measures are needed to maintain freshness during the distribution process of marine products, and monitoring of freshness of marine products must be a prerequisite. The freshness of marine products is reduced due to autoenzymes contained in microorganisms and muscles, and odor (bad smell) is generated accordingly. Volatile basic nitrogen (VBN), which causes odor (bad smell), is one of the important quality factors in determining the freshness of seafood. Accordingly, a new type of packaging technology that allows consumers or distributors to easily predict the freshness of seafood by measuring the amount of volatile basic nitrogen (VBN) generated during the storage period of seafood is attracting attention.

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 period of food and visually displaying the freshness correlated thereto, so that consumers or distributors can easily and quickly determine freshness. The purpose is to provide food packaging materials containing this.

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

2. In 1 above, a freshness indicator where the food subject to the freshness indicator is a marine product selected from the group consisting of mackerel, mackerel, cutlassfish, cod, herring, saury, bonito, croaker, flounder, monkfish, flounder, conger eel, filefish, rockfish, and stingray. .

3. The freshness indicator of 1 above, wherein the food subject to the freshness indicator is mackerel, and the mixed layer contains cresol red and bromocresol purple in a weight ratio of 1:9 to 3:7.

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 porous breathable sheet on the mixed layer.

6. The freshness indicator of 5 above, wherein the porous breathable sheet is hydrophobic.

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

The freshness indicator of the present invention detects volatile basic nitrogen (VBN) generated during the storage period of food and correlates it with freshness to predict the freshness of food quickly and easily in a non-destructive and visual way without any additional process. .

Figure 1 is a graph showing the correlation between food sample storage days and volatile base nitrogen (VBN) values.
Figure 2 is a graph showing the correlation between the number of days food samples are stored and changes in the number of microorganisms.
Figure 3 is a graph showing the correlation between the number of days of food sample storage and pH change.
Figure 4 shows a gas sensor manufactured by selecting various combinations and content ratios of cresol red, bromocresol purple, bromocresol green, and bromothymol blue. It shows the color change according to the negative ammonia concentration.
Figure 5 shows the color change of the gas sensor unit manufactured by selecting a combination of bromothymol blue and phenol red according to the treatment of food samples.

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 cresol red and bromocresol purple.

Cresol Red 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 cresol red and bromocresol purple may be, for example, a coating layer of cresol red and bromocresol purple solutions. For example, it may be coated on a substrate, or it may be formed by absorbing the solution into the substrate.

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

The content ratio of cresol red and bromocresol purple is not particularly limited, and the amount of volatile basic nitrogen (VBN) that can be detected may vary depending on the content ratio, so this can be applied to the type of food for which freshness is to be indicated, etc. It can be selected appropriately. For example, since the pH range of cresol red is higher than that of bromocresol purple, the content of cresol red can be increased in the case of foods that generate a large amount of volatile basic nitrogen (e.g., fermented fish). In the case of foods that generate a small amount of volatile basic nitrogen (e.g., mackerel, mackerel, etc.), the content ratio of cresol red and bromocresol purple can be adjusted by reducing the content of cresol red.

To give a specific example, when the target food is mackerel, the weight ratio of cresol red and bromocresol purple may be 1:9 to 3:7.

Solvents for cresol red and bromocresol purple solutions can be used without limitation as long as they can dissolve these indicators, for example, acetone, butanone, cyclohexanone, isophorone, tetralone, Ketone-based solvents such as decalone and acetylacetone; Chlorine-based solvents such as chloroform, methylene chloride, 1,2-dichloroethane, 1,12-trichloroethane, chlorobenzene, and o-dichlorobenzene; Ether-based solvents such as tetrahydrofuran and dioxane; Aromatic hydrocarbon solvents such as toluene, xylene, trimethylbenzene, and mesitylene; Aliphatic hydrocarbon solvents such as cyclohexane, methylcyclohexane, n-pentane, 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 ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether, dimethoxy ethane, propylene glycol, diethoxymethane, triethylene glycol monoethyl ether, glycerin, and 1,2-hexanediol; Alcohol-based solvents such as methanol, ethanol, propanol, isopropanol, and cyclohexanol; Sulfoxide-based solvents such as dimethyl sulfoxide; and amide-based solvents such as N-methyl-2-pyrrolidone and N,N-dimethylformamide, or solvents consisting of a combination of one or more of these may be used. Preferably, a ketone-based solvent may be used, and more specifically A mixed solvent of acetone and butanone may be used.

Cellulose acetate, cellulose nitrate, cellulose propionate, hydroxypropyl cellulose, and hydroxypropylmethyl for chemical resistance of cresol red and bromocresol purple solutions. It may further include cellulose (hydroxypropylmethyl cellulose), etc., and may further include a plasticizer, such as an eco-friendly non-phthalate plasticizer (eco-DEHCH), to adjust the viscosity of the cresol red and bromocresol purple solutions. can do.

In the freshness indicator of the present invention, for example, the food subject to the freshness indicator may be fish. This may include, but is not limited to, mackerel, mackerel, cutlassfish, cod, herring, saury, skipjack tuna, croaker, flounder, monkfish, flounder, conger eel, filefish, rockfish or stingray.

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

By further including a breathable sheet, gas can pass through the gas sensor unit to indicate freshness, while preventing deterioration of the gas sensor unit by reducing contact of moisture, foreign substances, etc. to the gas sensor unit.

The breathable sheet may be porous in that it allows volatile basic nitrogen (VBN) generated from food to reach the gas sensor unit with high permeability.

The breathable sheet may be a hydrophobic sheet in that it prevents moisture, etc., which may be generated from food, from diffusing into the gas sensor unit. This may be done by using a sheet of hydrophobic material or by applying a hydrophobic coating on the sheet. Sheets made of hydrophobic materials include polyethylene (PE), polyacrylonitrile, polyacrylate, polyacrylamide, maleic anhydride polymer, and polypropylene glycol. ), polyurethane, polystyrene, epoxy, polyvinyl chloride, polyvinylidene fluoride (PVDF), fluorocarbon polymer, polytetrafluoroethylene, PTFE), polydimethylsiloxane (PDMS), polyester, polyethylene terephathalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), Polyethylene terephthalate glycol (PETG), polypropylene (PP), polyamide (PA)-6, polymethyl methacrylate (PMMA), polyethyl methacrylate ), polycarbonate (PC), polymethylpentene, etc., and specifically, sheets of hydrophobic and breathable materials such as polyethylene, polytetrafluoroethylene, and polyvinylidene fluoride. It can be.

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 air in the external environment, the protective film prevents deformation of the gas sensor unit due to this environment.

As the protective film, materials known in the art can be used without limitation, such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene, SAN (styrene acrylonitrile copolymer) resin, ABS (acrylonitrile-butadiene-styrene) resin, expandable polystyrene (EPS), polymethyl methacrylate, polycarbonate (PC), polydihydroferulic acid (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), polyetherether ketone ( Polyether ether ketone (PEEK), polyphenylene sulfide (PPS), nylon, etc. can be used.

For example, the protective film may be included on the gas sensor unit, and if a breathable sheet is included on the gas sensor unit, it may be included on the other side of the side to which the breathable sheet 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 breathable sheet, the gas may pass through the breathable sheet 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 indication may be fish, for example, mackerel, mackerel, cutlassfish, cod, herring, saury, bonito, croaker, flounder, monkfish, flounder, conger eel, filefish, rockfish, or stingray. there is.

When the freshness indicator included in the food packaging material further includes a breathable sheet, the freshness indicator may be included in the food packaging material with the breathable sheet 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. Acetone and 2-butanone were mixed in a container at a volume ratio of 1:1 to prepare 40 ml of mixed solution. 1.2 g of cellulose acetate was added to the mixed solution and dissolved. Afterwards, 0.3ml of eco-DEHCH, a plasticizer, was added. Afterwards, 8 mg of Cresol Red and 32 mg of Bromocresol Purple were added to prepare a mixed solution of Cresol Red and Bromocresol Purple.

This was applied to filter paper (HC-050) and dried in the dark at room temperature to form a mixed layer of cresol red and bromocresol purple.

A porous breathable sheet (BREATHRON ^™ , Nitto), a triple-structured laminated film, was attached to one side of the gas sensor unit manufactured using the above method using a thermal bonding method. Afterwards, an adhesive was applied to the other side of the gas sensor unit where the porous breathable sheet was adhered, and a PET film was adhered to produce a freshness indicator.

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 for mackerel among foods was confirmed. Mackerel samples were collected and the color change of the indicator was checked by applying an indicator to the change in volatile basic nitrogen (VBN) value, change in the total number of microorganisms, change in pH, and the change in color of the indicator according to the number of days of mackerel storage at 20°C, prepared in Example 1. After mackerel was stored in a food packaging material, the color change of the gas sensor attached to the packaging material was measured.

1. Observation of color change according to change in volatile basic nitrogen (VBN) value

(1) Experimental method

10 g of mackerel sample was collected, placed in 90 mL of distilled water and a sterilized bag, and the solution homogenized with a homogenizer was used as a sample solution to measure the amount of volatile basic nitrogen produced. The freshness indicator prepared in Example 1 was applied to this to measure 20 The color change of the indicator according to the amount of volatile basic nitrogen was observed at ℃.

After filtering the homogenate with filter paper (Whatman NO.1), 1 mL of 0.01 N-sulfuric acid was added to the inner chamber of the Conway unit, and 1 mL of the sample solution and 1 mL of potassium carbonate were added to the outer chamber, and the lid was closed and sealed. The Conway unit was placed horizontally to allow the test solution and potassium carbonate solution to react. It was activated in an incubator at 37°C for 90 minutes, and 50 μL of Brunswik indicator was added to the inner chamber, followed by titration with 0.01 N sodium hydroxide solution.

(2) Experiment results

Volatile basic nitrogen (VBN) content was analyzed by microdiffusion method using a conway unit. The amount of volatile basic nitrogen (VBN) generated was calculated according to Equation 1 below.

[Equation 1]

VBN value (mg%) = [(Titer value of sample - Titer value of blank sample)

Figure 1 shows the amount of volatile basic nitrogen generated over the storage period of mackerel samples and the color change of the indicator accordingly. During the storage period of mackerel samples, the amount of volatile base nitrogen (VBN) produced increased as the storage period passed, and on the 3rd day of the storage period, the amount of volatile base nitrogen produced reached 34.5 mg%, passing the initial spoilage judgment section (a) of 30 mg%. did. If the VBN production amount of fish meat is more than 30 mg%, it is confirmed that the color of the gas sensor part of the freshness indicator of the present invention changes from yellow to dark brown when it exceeds the initial spoilage standard, based on the initial spoilage progress, and volatile basic nitrogen is used to determine the initial spoilage. It was confirmed that the color changed to purple as it increased beyond the standard value.

2. Change in total microbial count value

(1) Experimental method

A 10 g mackerel sample was collected, placed in a sterilization bag with 90 mL of 0.1% sterilized peptone water, and the solution homogenized using a stomacher was used as a sample solution to measure the total number of microorganisms in the sample. The freshness indicator prepared in Example 1 was applied to this. The color change of the indicator according to the total number of microorganisms was observed at 20°C.

The sample solution was diluted with 0.1% sterilized peptone water using a stepwise dilution method, inoculated onto dry film plates for measuring general bacteria (petrifilm aerobic count plates, 3M Co., Saint Paul, MI, USA) and incubated at 37°C for 48 hours. After doing so, the number of colonies was measured and expressed as Log CFU/G.

(2) Experiment results

The total number of microorganisms occurring during the storage period of mackerel samples was measured using a bacteriological freshness determination method.

Figure 2 shows the total number of microorganisms measured over the storage period of mackerel samples and the color change of the indicator accordingly. During the storage period of the mackerel samples, the total number of microorganisms increased as the storage period passed, and reached 7 log CFU/g, the initial spoilage judgment standard (b), on the second day of the storage period. It was confirmed that the color of the gas sensor part of the freshness indicator of the present invention changed from yellow to dark yellow when it exceeded the initial spoilage standard ( ^1.5 It was confirmed that the indicator changed to purple as the total number of microorganisms increased.

3. pH changes

(1) Experimental method

5 g of mackerel sample was collected, mixed with 15 mL of distilled water, and the solution homogenized with a homogenizer was used as a sample solution to measure the pH value of the sample. The freshness indicator prepared in Example 1 was applied to measure the pH at 20°C. The color change of the indicator according to the change was observed.

After filtering the sample solution through filter paper (Whatman NO.1), the pH change was measured using a pH meter (Orion 3-Star Meter™; Thermo Fisher Scientific Inc).

(2) Experiment results

Figure 3 shows the change in pH value over the storage period of mackerel samples and the color change of the indicator accordingly. The pH value of the mackerel sample increased as the storage period passed, and reached pH 6.4, the initial spoilage judgment standard (c), between the second and third days of the storage period. It was confirmed that the color of the gas sensor part of the freshness indicator of the present invention changed from yellow to dark yellow when it exceeded the initial spoilage standard (pH 6.2 to 6.4) between the second and third days of the storage period of mackerel. It was confirmed that as the value increased, the color of the indicator changed from dark brown to purple.

4. Color change of gas sensor unit

(1) Experimental method

The freshness indicator manufactured in Example 1 was attached to the inside of the food packaging material containing 100 g of the mackerel sample, and the color change according to the storage period of the mackerel sample at 20°C was measured using a colorimeter (CM-2500d; Konica Minolta Inc., Tokyo, Japan). ) was measured using .

(2) Experiment results

The color change value (ΔE) of the gas sensor unit was calculated according to Equation 2 below. In the equation below, the L value represents brightness, the a value represents red (+) and green (-), and the b value represents yellow (+) and blue (-), and L, a, and b represent the brightness of the initial indicator color. and color values, L', a', and b', were calculated by substituting the brightness and color values for the indicator color that changed over the storage period.

[Equation 2]

The color change value (ΔE) according to the storage period of the mackerel samples for 7 days is shown in Table 1.

Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 ΔE 25.07 27.03 31.06 38.06 43.3 46.8 47.4

The suitability of the gas sensor unit can be judged by whether the color change value (ΔE) increases sequentially. Since the color change value (ΔE) calculated through the above experiment increased sequentially according to the storage period, the gas sensor unit It was confirmed that it was suitable for freshness indication.

Comparative example. Color change of the gas sensor section containing a mixed layer of bromocresol green, bromothymol blue, and phenol red.

(1) Experimental method

1) In order to evaluate the sequential color change of a freshness indicator including a gas sensor unit with a mixed layer of indicators other than the indicator combination of the present invention, only the indicator combination was used during the manufacturing process of the gas sensor unit of the freshness indicator of Example 1. It was manufactured with changes. The indicator combinations used were cresol red/bromocresol purple, cresol red/bromocresol green, and cresol red/bromothymol blue. There were three ratios of each indicator for each combination. By adjusting , the color change in the concentration of ammonia in volatile basic nitrogen (VBN) was confirmed for a total of 9 indicators.

The mixing mass ratio of the indicator combinations used in the experiment is shown in Table 2 below.

division Cresol Red (C) Bromocresol Purple (P) Bromocresol Green (G) Bromothymol Blue (B) One 0.2 (8 mg) 0.8 (32mg) - - 2 0.5 (20mg) 0.5 (20mg) - - 3 0.8 (32mg) 0.2 (8 mg) - - 4 0.2 (8 mg) - 0.8 (32mg) - 5 0.5 (20mg) - 0.5 (20mg) - 6 0.8 (32mg) - 0.2 (8mg) - 7 0.2 (8 mg) - - 0.8 (32mg) 8 0.5 (20mg) - - 0.5 (20mg) 9 0.8 (32mg) - - 0.2 (8 mg)

The combination of the nine indicators was reacted with ammonia at a concentration of 0 to 100 mg/kg to confirm the color change of the indicator.

2) During the manufacturing process of the gas sensor part of the freshness indicator of Example 1, only the combination of indicators was changed to phenol red and bromothymol blue in a 1:1 ratio. This was attached to a packaging material containing 100 g of mackerel sample, and the color change of the indicator according to the storage period was observed.

(2) Experiment results

1) The order of indicator combinations in FIG. 4A and the order of indicator combinations in the part showing the color change in FIG. 4B correspond to those at the same position. The indicator combined with cresol red/bromocresol purple (Table 2, 1 to 3) showed sequential color changes to yellow, dark yellow, and khaki as the reacting ammonia concentration increased, but cresol red/bromocresol The green combination indicator (Tables 2, 4 to 6) showed a color change from yellow to green when the ammonia concentration increased from 0 to 15 mg/kg, but did not show a clear color change even as the ammonia concentration increased thereafter. It was confirmed that the indicator of the cresol red/bromothymol blue combination (Table 2, 7 to 9) showed no significant color change throughout the process of increasing the ammonia concentration from 0 to 100 mg/kg (Figure 4) .

2) As a result of measuring the color change for 7 days during the storage period of mackerel with a freshness indicator manufactured by changing the indicator composition by changing the combination of phenol red and bromotibol blue during the manufacturing process of the gas sensor unit, a significant color change in the freshness indicator was confirmed. There was none (Figure 5). It was confirmed that the pH range of the indicator combination was not suitable for the indicated mackerel, so the amount of volatile basic nitrogen generated from the mackerel could not be properly measured.

Claims (7)

A freshness indicator comprising a gas sensor unit having a mixed layer of cresol red and bromocresol purple.
The freshness indicator according to claim 1, wherein the food subject to freshness indication is a marine product selected from the group consisting of mackerel, mackerel, cutlassfish, cod, herring, saury, skipjack tuna, croaker, flounder, monkfish, flounder, conger eel, filefish, rockfish, and stingray.
The freshness indicator according to claim 1, wherein the food subject to the freshness indicator is mackerel, and the mixed layer contains cresol red and bromocresol purple in a weight ratio of 1:9 to 3:7.
The freshness indicator according to claim 1, wherein the mixed layer is coated on a substrate.
The freshness indicator according to claim 1, further comprising a breathable sheet on the mixed layer.
The freshness indicator of claim 5, wherein the breathable sheet 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.