Slow-release intelligent preservative and method for directly evaluating its preservation effect

Abstract

The application discloses a slow-release type intelligent preservative and a method for directly evaluating the preservative effect, and belongs to the technical field of preservation. The porous hydrogel is soaked in a graphene oxide (GO) dispersion liquid, oscillated in a water bath, and dried; then, the porous hydrogel is placed in a citral-ethanol solution, oscillated in a water bath, and a slow-release type intelligent preservative is obtained. The application realizes the combination of high performance based on the porous hydrogel system, the slow release of citral active substances while absorbing water, and the bacteriostatic and preservative effect. The slow-release type intelligent preservative is placed in a preservation box together with mango, covered with a preservative film, the appearance and color change of the preservative are directly observed, the water absorption and citral release of the preservative are connected, and the preservative effect is directly evaluated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preservation, and particularly relates to a slow-release type intelligent preservative and a direct evaluation method of the preservation effect thereof. BACKGROUND

[0002] Fruit and vegetable preservation has been a hot and difficult problem at home and abroad. According to statistics, fruit and vegetable spoilage accounts for more than half of global food waste every year, mostly due to improper preservation during storage and transportation. Fruits and vegetables play an important role in people's daily dietary structure, and as consumers' requirements for food quality increase, it is of great significance to seek efficient and environmentally friendly preservation technology and materials.

[0003] The preservatives in the prior art generally include gas fumigation type, liquid immersion type, solid coating type and solid slow-release preservative. The solid slow-release preservative is a solid dosage form of preservative, which often does not need to rely on special equipment, complicated process and strict environment, and can be preserved for a long time due to the slow release of the preservative. However, the solid slow-release preservative still has many technical problems in the use process, such as uncontrollable release time of effective components, uneven release, etc.

[0004] Patent CN202210300774.0 discloses a 1-MCP slow-release preservative based on a hydrogel system, a preparation method and application, which utilizes a high molecular monomer and a crosslinking agent to wrap 1-MCP powder in a hydrogel system in a solvent containing diphenyl phosphorus oxide, and irradiates and solidifies into glue under ultraviolet light to obtain a 1-MCP slow-release preservative based on a hydrogel system. The preservative prepared by the method has the effects of moisturizing and buffering, and realizes long-acting stable slow release of 1-MCP gas, but diphenyl phosphorus oxide, a harmful substance, is used in the preparation process, and the preservation period and action time cannot be directly displayed, which is difficult to meet the actual preservation application requirements. SUMMARY

[0005] In view of the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a slow-release type intelligent preservative and a direct evaluation method of the preservation effect thereof.

[0006] The purpose of the present application is achieved by the following technical solutions.

[0007] A preparation method of a slow-release type intelligent preservative, comprising the following steps:

[0008] (1) Soak the porous hydrogel in a GO (graphene oxide) dispersion liquid, water-bath oscillate, and dry;

[0009] (2) Put the hydrogel obtained in step (1) into a citral-ethanol solution, water-bath oscillate, and obtain a slow-release type intelligent preservative.

[0010] Preferably, the concentration of the graphene oxide dispersion liquid is 0.5-1.5 mg / mL; and the concentration of the citral-ethanol solution is 5-10 μg / mL.

[0011] Further preferably, the concentration of the graphene oxide dispersion liquid is 1.0-1.5 mg / mL; and the concentration of the citral-ethanol solution is 7.5-10 μg / mL.

[0012] Preferably, the preparation of the porous hydrogel comprises the following steps:

[0013] (1) mixing a NaOH / urea solvent system with bagasse cellulose, pre-cooling, stirring and dispersing until the cellulose is completely dissolved to obtain a bagasse cellulose solution;

[0014] (2) adding acrylic acid and N,N'-methylene bisacrylamide to the bagasse cellulose solution, performing cold plasma treatment, water-bath stirring, standing after gelation, washing, and drying to obtain the porous hydrogel.

[0015] Further preferably, the mass ratio of NaOH, urea and water in the NaOH / urea solvent system is (5-9):(10-14):(80-84); the addition amount of the bagasse cellulose is 1.0-3.0% of the mass of the NaOH / urea solvent system; and the pre-cooling temperature is -12 to -8℃, and the pre-cooling time is 30-45 min.

[0016] Further preferably, the addition amount of the acrylic acid is 2-3 times of the mass of the dry bagasse cellulose; and the addition amount of the N,N'-methylene bisacrylamide is 0.2-0.3 times of the mass of the dry bagasse cellulose.

[0017] Further preferably, the voltage of the cold plasma treatment is 40-80 kV, the frequency is 50-70 Hz, the power is 45-60 kW, and the treatment time is 3-7 min; the temperature of the water-bath stirring is 60-80℃, and the stirring speed is 80-120 r / min; and the standing time is 18-24 h.

[0018] Preferably, the temperature of the water-bath oscillation is 35-40℃, the speed is 140-180 r / min, and the time is 20-40 min.

[0019] Further preferably, the temperature of the water-bath oscillation is 37℃, the speed is 140-180 r / min, and the time is 30 min.

[0020] A slow-release type intelligent preservative prepared by the preparation method of any one of the above.

[0021] The method for directly evaluating the preservation effect of the slow-release intelligent preservative described above includes the following steps:

[0022] The slow-release smart preservative was placed in a food storage box along with fruits and vegetables, covered with plastic wrap, and stored in a constant environment. The quality changes and disease occurrence of the fruits and vegetables were observed every two days. The humidity changes inside the food storage box during the storage period were monitored, and the color changes of the preservative were characterized. By visually judging the appearance and color changes of the preservative, and considering its water absorption and citral release, the preservation effect was directly evaluated.

[0023] A preferred method for directly evaluating the preservation effect of slow-release smart preservatives includes the following steps:

[0024] The slow-release intelligent preservative was placed in a storage box along with the fruits and vegetables, covered with plastic wrap, and stored in an MGC-300 artificial climate chamber (Changzhou Jintan Liangyou Instrument Co., Ltd.) at a temperature of 25±1℃ and a humidity of 75±1%. The quality changes and disease incidence of the mangoes were observed every two days. The fruit rot rate was calculated using the formula: Fruit rot rate (%) = (Number of diseased fruits / Total number of fruits) × 100. The humidity changes inside the storage box were monitored using an electronic thermometer and hygrometer. The color changes of the preservative were characterized using a CR-100 colorimeter (Konica Minolta). A standard white plate (L) was used as the reference. * =95.35, a * =0.01, b * =2.30) After calibration, the colorimeter is held perpendicular to the sample surface for measurement. Three points are measured for each sample, and the average value is taken. The color value is expressed as L. * (+brightness, -darkness), a * (+red, -green), b * (+yellow, -blue). ΔE reflects the total color difference (TCD) of the preservative sample, calculated according to the following formula:

[0025]

[0026] Among them, L0 * a0 * b0 * These represent the color values ​​of the preservative on day 0; L * a * b * These represent the color values ​​of the preservative and the mangoes after being stored together for different number of days.

[0027] Table 1 shows the color parameters L of the preservative of this invention. * a * b * And how ΔE changes with storage time.

[0028] Table 1

[0029]

[0030]

[0031] Note: Different letters in the same row indicate significant differences (p < 0.05)

[0032] The process of water absorption in storage affected the L * , a * , b * value to a certain extent, and the ΔE value was far greater than 3 at different storage days, which confirmed that the visual sensory could see obvious color change. First, the preservative gradually absorbed a small amount of water from the initial freeze-dried state to form a gel layer, the shape slightly shrunk, and a small amount of citral active molecules were released. Then, the water absorption and swelling volume increased, the hydrogel network structure opened, and the release of citral increased. In this process, a large number of water molecules entered the hydrogel pores and interacted with GO through hydrogen bonds, which made it more evenly dispersed between the hydrogels, resulting in the color of the sensor deepening and the brightness decreasing. As the release of citral increased, the preservative had the strongest preservation effect at this time, and the state of the preservative could be used to judge that the fruits and vegetables could be stored for a period of time. With the extension of storage time, the pores of the hydrogel were filled with water molecules, and the preservative had a large volume and uniform color. Combined with the release mechanism and cycle of citral molecules, it could be judged that citral was close to being completely released, and the hydrogel also gradually reached water balance, so the preservation effect was greatly weakened. At this time, the state of the preservative prompted consumers to handle the fruits and vegetables in time. In summary, the appearance and color change of the preservative were directly evaluated by judging the water absorption and citral release (see Figure 6 ).

[0033] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0034] (1) The present application utilizes the porous hydrogel system to composite GO and citral, realizes high-performance collection through the hydrogen bond interaction with the active functional groups in the hydrogel network structure, and prepares a multifunctional composite material.

[0035] (2) The composite GO makes the preservative more sensitive to capture water molecules in the air, reduces the relative humidity in the preservation box, and prolongs the storage time of fruits and vegetables.

[0036] (3) In the process of water absorption of the preservative, water molecules enter the interior of the hydrogel to compete for the hydrogen bond interaction sites of citral, and the water absorption of the preservative is closely related to the release of citral, which realizes the slow release of citral active substances while absorbing water, and then plays a bacteriostatic preservation role.

[0037] (4) The prepared preservative realizes long-acting slow release of citral, and overcomes the defects of citral, such as easy volatilization, instability, and easy degradation under relatively hot and acidic environment conditions.

[0038] (5) The water molecules are absorbed to promote uniform dispersion of GO between the hydrogel network structures, so that the preservative shows color difference in the storage process; by directly judging the appearance form and color change of the slow-release preservative, the water absorption and citral release are connected, so that the preservation time can be directly evaluated, and the purpose of intelligent preservation is achieved.

[0039] (6) The slow-release intelligent preservative prepared by the application uses non-toxic and harmless polymer materials, and has good biocompatibility and food safety guarantee. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The principle diagram for preparing the slow-release intelligent preservative of the application.

[0041] Figure 2 The flow chart for preparing the slow-release intelligent preservative of the application.

[0042] Figure 3 The preservation device diagram of the slow-release intelligent preservative of the application for mango fruits.

[0043] Figure 4 The influence curve diagram of the slow-release intelligent preservative of the application for the change of humidity in the package during the storage of mango fruits.

[0044] Figure 5 The influence curve diagram of the slow-release intelligent preservative of the application for the rot rate of mango fruits during the storage of mango fruits.

[0045] Figure 6 The evaluation diagram of the slow-release intelligent preservative of the application for the appearance form and color change and preservation effect during the storage. DETAILED DESCRIPTION

[0046] The application will be further described in detail in combination with examples, but the implementation manner of the application is not limited to this.

[0047] The principle diagram and the flow chart for preparing the slow-release intelligent preservative of the application are shown in Figure 1 , Figure 2 respectively, and the preservation device diagram of the obtained preservative for mango fruits is shown in Figure 3 .

[0048] The following control group is mango fruits without adding the preservative during the storage.

[0049] Example 1

[0050] The slow-release type intelligent preservative and its preparation method and application of the embodiment are as follows:

[0051] 7 g of NaOH and 12 g of urea were weighed and dissolved in 81 g of deionized water, 2 g of dry bagasse cellulose was added and pre-cooled at -12℃ for 30 min, and stirred and dispersed until the cellulose was completely dissolved to obtain a bagasse cellulose solution. 6 g of acrylic acid (AA) and 0.6 g of N,N'-methylene bisacrylamide (MBA) were weighed and added to the cellulose solution, and then cold plasma treatment was performed (voltage 50 kV, frequency control 60 Hz, power control 45 kW), the treatment time was 5 min. 70℃ water bath stirring, speed 100r / min, after gelation, room temperature standing 18h, the product was washed with water and ethanol, and vacuum dried to constant weight to obtain a porous hydrogel. The prepared porous hydrogel was soaked in a 1.0 mg / mL GO dispersion solution, 37℃ water bath oscillation 30 min, speed 160r / min, vacuum dried to constant weight. Then placed in 7.5μg / mL citral-ethanol solution, 37℃ water bath oscillation 30 min, speed 160r / min, to obtain a slow-release type intelligent preservative. The preservative was placed in a fresh-keeping box together with fruits and vegetables, and covered with a fresh-keeping film. It was determined that the humidity in the packaging of the preservative of the embodiment was 67% (the control group was 91%) on the 10th day of mango fruit storage, and the fruit rot rate was 42% (the control group was 70%), see Figure 4 、 Figure 5 .

[0052] Example 2

[0053] Take 7 g NaOH and 12 g urea dissolved in 81 g deionized water, add 2 g of dry bagasse cellulose and pre-cool together at -12℃ for 30 min, stir and disperse until the cellulose is completely dissolved, to obtain a bagasse cellulose solution. Take 6 g of acrylic acid (AA) and 0.6 g of N,N'-methylene bisacrylamide (MBA) and add to the cellulose solution, then perform cold plasma treatment (voltage of 50 kV, frequency control of 60 Hz, power control at 45 kW), treatment time of 5 min. 70℃ water bath stirring, speed of 100 r / min, after gelation room temperature standing for 18 h, the product is washed with water, ethanol, vacuum dried to constant weight, to obtain a porous hydrogel. The prepared porous hydrogel is soaked in a 1.5 mg / mL GO dispersion, 37℃ water bath oscillation for 30 min, speed of 160 r / min, vacuum dried to constant weight. Then placed in a 7.5 μg / mL citral-ethanol solution, 37℃ water bath oscillation for 30 min, speed of 160 r / min, to obtain a slow-release type intelligent preservative. The preservative is placed together with fruits and vegetables in a preservation box, covered with a preservative film. It is determined that the preservative of the present embodiment is 64% (control group is 91%) in the package humidity, the fruit rot rate is 40% (control group is 70%) at the 10th day of mango fruit storage, see Figure 4 、 Figure 5 .

[0054] Example 3

[0055] Take 7 g NaOH and 12 g urea dissolved in 81 g deionized water, add 2 g of dry bagasse cellulose and pre-cool together at -12℃ for 30 min, stir and disperse until the cellulose is completely dissolved, to obtain a bagasse cellulose solution. Take 6 g of acrylic acid (AA) and 0.6 g of N,N'-methylene bisacrylamide (MBA) and add to the cellulose solution, then perform cold plasma treatment (voltage of 50 kV, frequency control of 60 Hz, power control at 45 kW), treatment time of 5 min. 70℃ water bath stirring, speed of 100 r / min, after gelation room temperature standing for 18 h, the product is washed with water, ethanol, vacuum dried to constant weight, to obtain a porous hydrogel. The prepared porous hydrogel is soaked in a 1.5 mg / mL GO dispersion, 37℃ water bath oscillation for 30 min, speed of 160 r / min, vacuum dried to constant weight. Then placed in a 7.5 μg / mL citral-ethanol solution, 37℃ water bath oscillation for 30 min, speed of 160 r / min, to obtain a slow-release type intelligent preservative. The preservative is placed together with fruits and vegetables in a preservation box, covered with a preservative film. It is determined that the preservative of the present embodiment is 64% (control group is 91%) in the package humidity, the fruit rot rate is 40% (control group is 70%) at the 10th day of mango fruit storage, see Figure 4 、 Figure 5 .

[0056] Comparative Example 1

[0057] Take 7 g NaOH and 12 g urea dissolved in 81 g deionized water, add 2 g of dry bagasse cellulose and together pre-cool at -12℃ for 30 min, stirring and dispersing until the cellulose is completely dissolved, to obtain a bagasse cellulose solution. Take 6 g of acrylic acid (AA) and 0.6 g of N,N'-methylene bisacrylamide (MBA) and add to the cellulose solution, then perform cold plasma treatment (voltage of 50 kV, frequency control of 60 Hz, power control at 45 kW), treatment time of 5 min. 70℃ water bath stirring, speed of 100 r / min, after gelation room temperature standing for 18 h, the product is washed with water, ethanol, vacuum dried to constant weight, to obtain a porous hydrogel. The prepared porous hydrogel is soaked in a 0.5 mg / mL GO dispersion, 37℃ water bath oscillation for 30 min, speed of 160 r / min, vacuum dried to constant weight. Then placed in a 5 μg / mL citral-ethanol solution, 37℃ water bath oscillation for 30 min, speed of 160 r / min, to obtain a slow-release type intelligent preservative. The preservative is placed in a fresh-keeping box together with fruits and vegetables, covered with a fresh-keeping film. It is determined that the preservative of the present example has a humidity of 74% (control group is 91%) and a fruit rot rate of 52% (control group is 70%) on the 10th day of mango fruit storage, see Figure 4 , Figure 5 .

[0058] Comparative Example 2

[0059] Take 7 g NaOH and 12 g urea dissolved in 81 g deionized water, add 2 g of dry bagasse cellulose and together pre-cool at -12℃ for 30 min, stirring and dispersing until the cellulose is completely dissolved, to obtain a bagasse cellulose solution. Take 6 g of acrylic acid (AA) and 0.6 g of N,N'-methylene bisacrylamide (MBA) and add to the cellulose solution, then perform cold plasma treatment (voltage of 50 kV, frequency control of 60 Hz, power control at 45 kW), treatment time of 5 min. 70℃ water bath stirring, speed of 100 r / min, after gelation room temperature standing for 18 h, the product is washed with water, ethanol, vacuum dried to constant weight, to obtain a porous hydrogel. The prepared porous hydrogel is soaked in a 1.0 mg / mL GO dispersion, 37℃ water bath oscillation for 30 min, speed of 160 r / min, vacuum dried to constant weight. Then placed in a 5 μg / mL citral-ethanol solution, 37℃ water bath oscillation for 30 min, speed of 160 r / min, to obtain a slow-release type intelligent preservative. The preservative is placed in a fresh-keeping box together with fruits and vegetables, covered with a fresh-keeping film. It is determined that the preservative of the present example has a humidity of 66% (control group is 91%) and a fruit rot rate of 50% (control group is 70%) on the 10th day of mango fruit storage, seeFigure 4 、 Figure 5 .

[0060] Comparative Example 3

[0061] 7 g of NaOH and 12 g of urea were weighed and dissolved in 81 g of deionized water, 2 g of dry bagasse cellulose was added and pre-cooled at -12℃ for 30 min, and stirred and dispersed until the cellulose was completely dissolved to obtain a bagasse cellulose solution. 6 g of acrylic acid (AA) and 0.6 g of N,N'-methylenebisacrylamide (MBA) were weighed and added to the cellulose solution, and then subjected to cold plasma treatment (voltage of 50 kV, frequency control of 60 Hz, and power control of 45 kW), and the treatment time was 5 min. The product was washed with water and ethanol, and vacuum dried to constant weight, to obtain a porous hydrogel. The prepared porous hydrogel was soaked in a GO dispersion solution of 0.5 mg / mL, and oscillated in a water bath at 37℃ for 30 min at a speed of 160 r / min, and vacuum dried to constant weight. Then it was placed in a citral-ethanol solution of 7.5 μg / mL, and oscillated in a water bath at 37℃ for 30 min at a speed of 160 r / min, to obtain a slow-release intelligent preservative. The preservative was placed in a fresh-keeping box together with fruits and vegetables, and covered with a fresh-keeping film. It was determined that the preservative of the present example had a humidity of 77% (control group was 91%) and a fruit rot rate of 44% (control group was 70%) in the packaging at the 10th day of mango fruit storage, see Figure 4 、 Figure 5 .

[0062] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A method for preparing a slow-release intelligent preservative, characterized in that, It comprises the following steps: (1) soaking the porous hydrogel in a graphene oxide dispersion solution, water bath oscillation, drying; (2) placing the hydrogel obtained in step (1) in a citral-ethanol solution, water bath oscillation, to obtain a slow-release type intelligent preservative; The concentration of the graphene oxide dispersion solution is 1.0-1.5 mg / mL; the concentration of the citral-ethanol solution is 7.5-10 μg / mL; The preparation of the porous hydrogel comprises the following steps: (1) mixing a NaOH / urea solvent system with bagasse cellulose, pre-cooling, stirring and dispersing until the cellulose is completely dissolved, to obtain a bagasse cellulose solution; (2) adding acrylic acid and N,N'-methylene bisacrylamide to the bagasse cellulose solution, carrying out cold plasma treatment, water bath stirring, standing after gelation, washing, drying, to obtain the porous hydrogel.

2. The method of claim 1, wherein the method is characterized by, The mass ratio of NaOH, urea and water in the NaOH / urea solvent system is (5-9):(10-14):(80-84); the addition amount of the bagasse cellulose is 1.0-3.0% of the mass of the NaOH / urea solvent system; the pre-cooling temperature is-12~-8 ℃, and the time is 30-45 min.

3. The method of claim 1, wherein the method is characterized by, The addition amount of the acrylic acid is 2-3 times of the dry mass of the bagasse cellulose; the addition amount of the N,N'-methylene bisacrylamide is 0.2-0.3 times of the dry mass of the bagasse cellulose.

4. The method of claim 1, wherein the method is characterized by, The voltage of the cold plasma treatment is 40-80 kV, the frequency is 50-70 Hz, the power is 45-60 kW, and the treatment time is 3-7 min; the water bath stirring temperature is 60-80 ℃, the rotation speed is 80-120 r / min; the standing time is 18-24 h.

5. The method of claim 1, wherein the method is characterized by: The water bath oscillation temperature is all 35-40 ℃, the rotation speed is all 140-180 r / min, and the time is all 20-40 min.

6. A slow-release type intelligent preservative prepared by the preparation method of any one of claims 1-5.

7. The method for directly evaluating the fresh-keeping effect of the slow-release intelligent fresh-keeping agent according to claim 6, characterized in that, It comprises the following steps: Placing the slow-release type intelligent preservative together with vegetables and fruits in a preservation box, covering with a preservation film, placing in a constant environment for storage, observing the quality change and disease incidence of the vegetables and fruits every two days, monitoring the humidity change in the preservation box during the storage of the vegetables and fruits, characterizing the color change of the preservative, directly evaluating the preservation effect by visually judging the appearance and color change of the preservative, and connecting the water absorption and citral release.

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