CN118318947A - Chlorine dioxide slow-release starch-based fresh-keeping pad and preparation method and application thereof - Google Patents

Abstract

The invention discloses a chlorine dioxide slow-release starch-based fresh-keeping pad and a preparation method and application thereof. The chlorine dioxide slow-release starch-based fresh-keeping pad is prepared by hot-pressing a surface-layer foaming plate and a periphery sealing of a bottom-layer foaming plate through a surface-layer starch-based foaming plate, a bottom-layer starch-based foaming plate and a chlorine dioxide gas slow-release layer of a middle layer, wherein chlorite and an acid activator are filled in the chlorine dioxide gas slow-release layer, and the dosage and the mass ratio of the chlorite to the acid activator are 1:1. According to the invention, the slow release of the chlorine dioxide gas is realized by utilizing the porosity and hygroscopicity of the starch-based foaming plate, the slow release starch-based fresh-keeping pad and the fresh-keeping product are sealed in the modified atmosphere packaging bag, and the modified atmosphere packaging can be formed in the sealed packaging bag by the chlorine dioxide gas with a certain concentration along with the slow release of the chlorine dioxide gas, so that the effects of keeping fresh and preventing collision of the fresh-keeping product are realized, and the fresh-keeping product can be kept for a long time under the conditions of normal temperature and high humidity, for example, the fresh-wet noodles can be kept for 20 days.

Description

Chlorine dioxide slow-release starch-based fresh-keeping pad and preparation method and application thereof

Technical Field

The invention relates to a food fresh-keeping package, in particular to a chlorine dioxide slow-release starch-based fresh-keeping pad and a preparation method and application thereof.

Background technique

In the preservation process of some products with high water activity (content), such as fresh wet noodles, water droplets will condense on the surface of the product in a high humidity environment, and microorganisms are very easy to reproduce under high water content, causing them to spoil in a short time. At present, freshness preservation is often carried out by directly adding bactericides. Chlorine dioxide gas is an efficient and broad-spectrum bactericidal preservative that can kill most bacteria, fungi and viruses in nature. Its strong oxidizing effect can change the reducing amino acids or proteins of microorganisms such as Escherichia coli, Salmonella, yeast and mold, and can also destroy its genetic material by damaging the DNA molecules of microorganisms, thereby inhibiting the growth of microorganisms. Chlorine dioxide gas decomposes when exposed to light, and the residue is low. However, the release rate of chlorine dioxide is also an important factor affecting the preservation effect of chlorine dioxide. At present, chlorine dioxide gas preservatives are mostly used by spraying and soaking in chlorine dioxide solutions, but there are problems such as short action time, difficult to control concentration, and instability.

At the same time, if the release rate of chlorine dioxide is too fast, it will not achieve a long-term effect, and if the release rate is too slow, it will be difficult to effectively inhibit the growth of microorganisms. Therefore, how to obtain a bactericidal and fresh-keeping material that first releases quickly and then releases slowly is the key to solving the current problem of food preservation.

Summary of the invention

The object of the present invention is to provide a chlorine dioxide slow-release starch-based fresh-keeping pad which has a long-lasting fresh-keeping effect, has its own buffering performance, is low in cost and retains the original flavor of the fresh-keeping product.

The starch-based foam board used in the present invention has porosity and hygroscopicity. Compared with traditional fresh-keeping pad materials such as absorbent paper that is easy to break after absorbing water, and non-woven fabrics that are water-permeable but have poor water absorption, the starch-based foam board can have good water absorption while maintaining the mechanical properties of the material. The water absorption rate changes with the change of environmental humidity. The release of chlorine dioxide can be effectively regulated by absorbing moisture in the fresh-keeping system, and the fresh-keeping products can be kept dry. This is of great significance in promoting the development of my country's food storage and preservation technology, providing new packaging materials, etc.

Another object of the present invention is to provide a method for preparing a chlorine dioxide slow-release starch-based fresh-keeping pad.

The third object of the present invention is to provide a modified atmosphere fresh-keeping package and its application.

The chlorine dioxide slow-release starch-based fresh-keeping pad of the present invention can release chlorine dioxide gas by absorbing water vapor generated on the surface of the product. In the chemical reaction of chlorine dioxide gas generation, water molecules and their activity play a crucial role. In a solid system, the above reaction hardly occurs (or occurs very slowly). In the reaction system, as the water activity changes, the gas release rate also changes accordingly. The gas reaction speed and degree can be regulated by regulating the change of water in the system. The preparation of a carrier material that can regulate the change of water activity is the core key to the development of a functional regulated fresh-keeping pad. The starch-based foaming material has porosity and hygroscopicity, and its pore size becomes smaller as the amount of moisture absorbed increases. The present invention utilizes the good hygroscopicity of the starch-based foaming material and the structural characteristics of pore size change to encapsulate the chlorine dioxide slow-release layer in the middle. During the preservation process, the starch-based foaming board absorbs water vapor generated by the fresh-keeping product and utilizes its own hygroscopic characteristics to achieve the purpose of first quickly releasing and then long-term slow-release of chlorine dioxide, thereby achieving the formation of a safe high chlorine dioxide concentration environment in the early stage to quickly inhibit the growth of microorganisms on the surface of the fresh-keeping product, and maintaining a low chlorine dioxide concentration environment in the later stage to achieve a long-term stable preservation effect.

The purpose of the present invention is achieved through the following technical solutions:

A chlorine dioxide slow-release starch-based fresh-keeping pad comprises a surface starch-based foam board, a bottom starch-based foam board and a middle chlorine dioxide gas slow-release layer; the chlorine dioxide gas slow-release layer comprises chlorite and an acidic activator; the mass ratio of chlorite to the acidic activator is 1:1.

Preferably, the dosage of chlorite is 0.01-0.03 g/50 g of fresh-keeping product.

Preferably, the chlorite used is sodium chlorite.

Preferably, the acidic activator used is at least one of oxalic acid, citric acid, tartaric acid and sodium bisulfate.

Preferably, the thickness of the bottom starch-based foam board and the surface starch-based foam board are both 3-6 mm; the thickness of the chlorine dioxide gas slow-release layer is 1-2 mm.

Preferably, the raw materials used for the starch-based foamed board include 80-85wt% starch, 4-8wt% polyvinyl alcohol, 5-10wt% plasticizer, 3-6wt% foaming agent, 1-2wt% nucleating agent, 1-2wt% fiber, and the balance is water, and the board is made by an extrusion foaming process.

A method for preparing the chlorine dioxide slow-release starch-based fresh-keeping pad comprises the following steps:

(1) Weighing chlorite and acid activator;

(2) The chlorite and the acidic activator weighed in step (1) are uniformly mixed and evenly spread on the surface of the bottom starch-based foam board, and then the surface starch-based foam board and the bottom starch-based foam board are sealed by hot pressing to obtain a slow-release starch-based fresh-keeping pad.

The present invention also provides a modified atmosphere fresh-keeping package, which is prepared by sealing the chlorine dioxide slow-release starch-based fresh-keeping pad in an outer package.

The invention also provides an application of the modified atmosphere fresh-keeping packaging, and the modified atmosphere fresh-keeping packaging is used for preserving fresh wet noodles.

The present invention is based on starch-based foaming board to prepare modified atmosphere fresh-keeping packaging for products with high moisture content. The fresh-keeping product is placed directly above the slow-release fresh-keeping pad and sealed in the outer packaging. Based on the hygroscopic characteristics of the starch-based foaming board, the starch-based fresh-keeping pad can effectively absorb water vapor on the surface of the product, reducing the effect of excessive moisture on the fresh-keeping of the product. At the same time, the absorbed moisture can make the chlorine dioxide slow-release layer release chlorine dioxide gas, and spontaneously form a modified atmosphere packaging in the sealed modified atmosphere fresh-keeping bag; and as the starch-based foaming board absorbs moisture, the pore size of the starch-based foaming board becomes smaller, from 0.69mm to 0.32mm, thereby achieving the effect of first rapid release of chlorine dioxide gas and then long-term slow release, thereby achieving long-term fresh-keeping of the product.

The beneficial effects of the present invention are:

1. The chlorine dioxide slow-release starch-based fresh-keeping pad of the present invention does not need to add water to the raw materials. The starch-based foamed board used has good water absorption while maintaining its own mechanical properties, can absorb moisture on the surface of high-humidity products, and regulate the water absorption rate according to the change of the relative humidity of the environment, thereby regulating the rate of chlorine dioxide release, achieving the slow release of chlorine dioxide gas, and at the same time keeping the fresh-keeping products dry, effectively extending the shelf life of the fresh-keeping products.

2. The chlorine dioxide slow-release starch-based fresh-keeping pad of the present invention can realize the rapid release of chlorine dioxide first and then the slow release, so that the product is in a safe high-concentration chlorine dioxide environment in the early stage and maintains a low-concentration chlorine dioxide environment in the later stage, achieving the fresh-keeping effect of rapid bacteriostasis in the early stage and long-term maintenance of bacteriostasis in the later stage.

3. The slow-release starch-based fresh-keeping pad of the present invention has certain buffering properties and can still maintain its buffering properties in a high-humidity environment, thereby effectively protecting the appearance of fresh-keeping products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram showing the pore changes of a starch-based sustained-release fresh-keeping pad as humidity increases.

Figure 2 shows the moisture absorption curves of starch-based foamed board at different humidity levels.

FIG. 3 is a chlorine dioxide release curve of a chlorine dioxide slow-release fresh-keeping pad at different humidity levels.

FIG. 4 is a graph showing the chlorine dioxide release curves in Examples 1, 2, and 3.

FIG5 is a graph showing the chlorine dioxide release curve in Comparative Example 2.

FIG6 is a comparison diagram of fresh wet noodles in Examples 2 and 3 and Comparative Example 1 after 20 days of preservation.

FIG. 7 is a graph showing the antibacterial (Aspergillus niger) experimental effect when the dosage of chlorite is 0.01 g and 0.03 g.

Detailed ways

In order to better understand the present invention, the present invention is further described below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

The method of the chlorine dioxide slow-release starch-based fresh-keeping pad in the embodiment is as follows:

(1) Sodium chlorite is selected as the chlorite, and citric acid is selected as the acidic activator;

(2) 80 wt% starch, 6 wt% polyvinyl alcohol, 5 wt% glycerol (plasticizer), 3 wt% ethanol (foaming agent), 2 wt% calcium carbonate (nucleating agent), 2 wt% dry peanut shell residue (fiber), and 2 wt% water are used to prepare a starch-based foamed board through an extrusion foaming process;

(3) The chlorite and the acidic activator weighed in step (1) are uniformly mixed, uniformly sprinkled on the starch-based foam board and fully mixed, and the surface foam board and the bottom foam board are hot-pressed and sealed at the periphery to prepare a fresh-keeping mat.

Example 1

Sodium chlorite is selected as chlorite, and citric acid is selected as acid activator, both of which are used in an amount of 0.01g; they are evenly sprinkled on the starch-based foam board and fully mixed, the thickness of the surface starch-based foam board and the bottom starch-based foam board is selected to be 6mm, the thickness of the chlorine dioxide gas slow-release layer is controlled to be 1mm, and the surface foam board and the bottom foam board are hot-pressed and sealed around to obtain a fresh-keeping mat. The slow-release starch-based foam fresh-keeping mat is sealed together with 50g of fresh wet noodles in a 0.3mm thick PE self-sealing bag.

Example 2

Sodium chlorite is selected as chlorite, and tartaric acid is selected as acidic activator, both of which are used in an amount of 0.02g, and are evenly sprinkled on the starch-based foam board and fully mixed. The thickness of the surface starch-based foam board and the bottom starch-based foam board is selected to be 6mm, and the thickness of the chlorine dioxide gas slow-release layer is controlled to be 2mm. The surface foam board and the bottom foam board are hot-pressed and sealed around to obtain a fresh-keeping mat. The slow-release starch-based foam fresh-keeping mat is sealed together with 50g of fresh wet noodles in a 0.3mm thick PE self-sealing bag.

Example 3

Sodium chlorite is selected as chlorite, and tartaric acid is selected as acidic activator, both of which are used in an amount of 0.03g, and are evenly sprinkled on the starch-based foam board and fully mixed. The thickness of the surface starch-based foam board and the bottom starch-based foam board is selected to be 6mm, and the thickness of the chlorine dioxide gas slow-release layer is controlled to be 2mm. The surface foam board and the bottom foam board are hot-pressed and sealed around to obtain a fresh-keeping mat. The slow-release starch-based foam fresh-keeping mat is sealed together with 50g of fresh wet noodles in a 0.3mm thick PE self-sealing bag.

Comparative Example 1

50 g of fresh wet noodles were sealed in a 0.3 mm thick PE ziplock bag without any treatment.

Comparative Example 2

Sodium chlorite is used as the chlorite, and citric acid is used as the acid activator. The dosage of both is 0.02 g, which are evenly sprinkled on the PE film and fully mixed to obtain a PE film fresh-keeping mat. The PE film fresh-keeping mat and 50 g of fresh wet noodles are sealed together in a 0.3 mm thick PE ziplock bag.

The inventor characterized the pore size of the starch-based foam board under different humidity. The specific test method is to place the starch-based foam board in a constant temperature (25°C) and constant humidity sealed box (humidity is 60% RH, 80% RH, 93% RH respectively) for 14 days, and then perform electron microscope scanning on the starch-based foam board. The electron microscope scanning image is shown in Figure 1. It can be clearly seen that the pore size of the starch-based foam board decreases with the increase of humidity. The pore size of the starch-based foam board in the scanning electron microscope image was counted by the software Image J, as shown in Table 1. As the humidity increases, the pore size of the starch-based foam board decreases from 0.69mm to 0.32mm.

The inventors tested the moisture absorption performance of starch-based foam boards at different humidity levels. The specific test method is to cut the foam board samples into 4cm×3cm blocks in advance, place them in a 40℃ oven to dry for 12h, and then weigh their initial mass. Then the samples are placed in a constant temperature (25℃) and constant humidity sealed box (the humidity is 80%RH and 93%RH, and the default mass does not change at 60%RH), and weighed every 24h. Each sample is measured three times in parallel. The test results are shown in Figure 2. The moisture absorption rate of the material is calculated according to the following formula:

Wherein, _Mt is the mass of the sample weighed at time t (g); _M0 is the initial mass of the sample (g).

The results show that the moisture absorption rate and equilibrium moisture of the starch-based foam board increase with the increase of relative humidity, indicating that the starch-based foam board has good moisture absorption performance, and the overall trend of the moisture absorption curve shows a gradual and rapid increase first and then a stable equilibrium, which is consistent with the gas release curve of rapid release in the early stage and long-term sustained release in the later stage.

The inventors tested the compression properties of starch-based foam boards under different humidity. The specific test method is to place the starch-based foam boards in a constant temperature (25°C) and constant humidity sealed box (the humidity is 60% RH, 80% RH, and 93% RH respectively) for 14 days, and then use the INSTRONT 5566 universal material testing machine to test the compression properties of the starch-based foam boards. Fix the sample on the sample table, make the test probe close to the surface of the sample and set the compression distance of the testing machine to 50% of the sample thickness, set the compression speed to 5mm/min, and after compressing once, wait for the sample height to return to stability, and use a vernier caliper to measure the recovered height. Five parallels are set for each group of samples, and the test results are shown in Table 2. The calculation formulas for compressive strength and rebound rate are as follows:

Wherein, F is the maximum load (N) when the sample is compressed to 50%; S is the bearing area of the probe (m ² ).

Wherein, h is 50% of the sample thickness (mm); _h1 is the height of the sample recovered after the first compression (mm).

The results show that the starch-based foamed board used in the present invention can still maintain good compressive strength in a high humidity environment, with a rebound rate of more than 70%, and can play a role in buffering and protecting fresh-keeping products.

The inventors have measured the chlorine dioxide release curve of the chlorine dioxide slow-release starch-based fresh-keeping pad in the present invention at different humidity. The specific test method is: place the chlorine dioxide slow-release fresh-keeping pad containing 0.03g sodium chlorite and 0.03g citric acid in a sealed box with constant temperature (25°C) and constant humidity (75%RH, 80%RH, 93%RH) at regular intervals, and use a handheld gas meter to measure the chlorine dioxide gas concentration in the box. The test results are shown in Figure 3. The results show that as the ambient humidity increases, the concentration and peak concentration of chlorine dioxide in the box also increase.

The inventors measured the chlorine dioxide gas release curves of the fresh-keeping pads of Examples 1, 2, 3 and Comparative Example 2 of the present invention. The specific test method is: the material to be tested is placed in a sealed box with constant temperature (25°C) and constant humidity (93% RH) (50g of fresh wet noodles and a hygrometer are sealed in a 0.3mm thick PE ziplock bag for 3 days, and the hygrometer shows 93% RH, so the test selects humidity 93% RH), and the chlorine dioxide gas concentration in the box is measured with a handheld gas meter at intervals. The test results are shown in Figures 4 and 5. The results show that the chlorine dioxide gas concentration of Comparative Example 2 has dropped to 0 at the 19th hour, while Examples 1, 2, and 3 still maintain a low chlorine dioxide concentration at the 55th hour. The chlorine dioxide slow-release starch-based fresh-keeping pad of the present invention can achieve the effect of rapid release in the early stage and slow release of chlorine dioxide in the later stage. Furthermore, the peak chlorine dioxide concentrations of Examples 1, 2, and 3 are much lower than those of Comparative Example 2, indicating that the chlorine dioxide slow-release starch-based fresh-keeping pad of the present invention rapidly releases chlorine dioxide in the early stage but does not reach an excessively high concentration to damage the appearance and nutrients of the product.

The inventors determined the total colony count of the fresh wet noodles in Examples 1 and 3 of the present invention and Comparative Example 1 after treatment for 20 days, and tested them according to the method in GB 4789.2-2022 "National Food Safety Standard for Food Microbiological Examination for Determination of Total Colony Count", and the test results are shown in Table 3. The results show that the chlorine dioxide slow-release starch-based fresh-keeping pad can effectively inhibit the growth of bacteria in noodles, and the total colony count of the fresh wet noodles in Examples 1 and 3 after treatment for 20 days is less than the total colony count limit of 5×10 ⁵ CFU/g specified in GB 2713-2015 "National Food Safety Standard for Starch Products", while Comparative Example 1 exceeds it.

The inventors determined the inhibitory effect of the environment on Aspergillus niger in Examples 1 and 3 of the present invention and Comparative Example 1. The specific test method is to inoculate a 5 cm × 5 cm Aspergillus niger (CMCC98003) bacterial block on a PDA plate in a clean bench, and place the inoculated plates in a constant temperature (25°C) and constant humidity (93% RH) sealed box for culture, and keep the same preservation treatment method as in Examples 1 and 3 and Comparative Example 1. The results after 14 days of culture are shown in Figure 7. It can be clearly seen in Figure 7 that the chlorine dioxide slow-release starch-based fresh-keeping pad has an inhibitory effect on the growth of Aspergillus niger.

The inventors conducted a sensory evaluation test on the odor of fresh wet noodles in Examples 1, 2, 3 and Comparative Example 1 of the present invention after 20 days of treatment. The noodle odor evaluation standard is: 1-3 = normal, no odor, 3-6 = slight sour odor, 6-9 = obvious sour odor. The evaluation method is that 10 volunteers evaluate the odor of fresh wet noodles in Examples 1, 2, 3 and Comparative Example 1 after 20 days of treatment, and the evaluation results are shown in Table 4. The results show that the fresh wet noodles treated with the chlorine dioxide slow-release starch-based fresh-keeping pad can still remain normal and odorless after 20 days.

The inventors determined the residual amount of chlorine dioxide in the noodles in Examples 1, 2, and 3. The specific implementation method refers to GB5009.244-2016 "Determination of Chlorine Dioxide in Food", weigh 1.00g of sample in a 50mL centrifuge tube, add 20mL phosphate buffer (pH6.5), 8000r/min homogenization extraction for 3min, 10000r/min refrigerated centrifugation for 10min, and then filter. Take 5mL of filtrate in a stoppered colorimetric tube, add 1mL glycine solution, 1mL phosphate buffer and 1mL DPD solution, dilute to 10mL with water and shake well, measure the absorbance at 552nm within 60s, and prepare a series of concentrations of chlorine dioxide standard solution samples according to the above method and measure the absorbance at 552nm to obtain a standard curve. Examples 1, 2, and 3 were measured three times in parallel, and the test results are shown in Table 5. The chlorine dioxide in the sample is settled according to the following formula:

Wherein, X is the chlorine dioxide content in the sample (mg/kg), c is the chlorine dioxide concentration in the sample solution (mg/L), _c0 is the chlorine dioxide concentration in the blank reagent (mg/L), V is the final fixed volume of the sample solution (mL), and m is the sample mass (g).

The results showed that when noodles were preserved with a chlorine dioxide slow-release preservation mat, the residual chlorine dioxide on the noodles was very small. When 50g of noodles were preserved with a preservation mat containing 0.03g of sodium chlorite, the residual amount was less than 0.7mg/kg.

Table 1 Average cell particle size of starch-based foamed board at different relative humidity

Table 2 Compression properties of starch-based foam board at different humidity

humidity Compressive strength(Kpa) Rebound rate (%) 60%RH 359.45±7.40 90.21±1.43 80%RH 31.11±1.23 78.36±2.06 93%RH 15.97±0.97 70.19±2.48

Table 3 Total number of colonies in fresh wet noodles after 20 days of treatment in Examples 1, 3 and Comparative Example 1

Example 1 Example 3 Comparative Example 1 Total colony count (CFU/g) 2.77×10 ³ 1.75×10 ³ 6.7×10 ⁵

Table 4 Odor measurement results of fresh wet noodles after 20 days of treatment in Examples 1, 2, 3 and Comparative Example 1

Example 1 Example 2 Example 3 Comparative Example 1 1.88±0.79 1.37±0.45 2.75±0.77 7.36±0.83

Table 5 Chlorine dioxide residual in Examples 1, 2, and 3

Example 1 Example 2 Example 3 ClO ₂ residual amount (mg/kg) 0.187±0.006 0.360±0.010 0.653±0.006

The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims (9)

1. A chlorine dioxide slow-release starch-based fresh-keeping pad, characterized in that it comprises a surface starch-based foamed board, a bottom starch-based foamed board and a chlorine dioxide gas slow-release layer in the middle layer, wherein the chlorine dioxide gas slow-release layer comprises chlorite and an acidic activator; the mass ratio of chlorite to the acidic activator is 1:1. 2. The chlorine dioxide slow-release starch-based fresh-keeping pad according to claim 1, characterized in that the amount of chlorite used is 0.01-0.03g/50g of fresh-keeping product. 3. The chlorine dioxide slow-release starch-based fresh-keeping pad according to claim 1, characterized in that the chlorite used is sodium chlorite. 4. The chlorine dioxide slow-release starch-based fresh-keeping pad according to claim 1, characterized in that the acidic activator used is at least one of oxalic acid, citric acid, tartaric acid and sodium bisulfate. 5. The chlorine dioxide slow-release starch-based fresh-keeping pad according to claim 1, characterized in that the thickness of the bottom starch-based foam board and the surface starch-based foam board are both 3-6 mm; the thickness of the chlorine dioxide gas slow-release layer is 1-2 mm. 6. The chlorine dioxide slow-release starch-based fresh-keeping pad according to claim 1 is characterized in that the raw materials used for the starch-based foamed board are 80-85wt% starch, 4-8wt% polyvinyl alcohol, 5-10wt% plasticizer, 3-6wt% foaming agent, 1-2wt% nucleating agent, 1-2wt% fiber and water, and is made by extrusion foaming process. 7. The method for preparing the chlorine dioxide slow-release starch-based fresh-keeping pad according to any one of claims 1 to 6, characterized in that it comprises the following steps: (1) Weighing chlorite and acid activator; (2) The chlorite and the acidic activator weighed in step (1) are uniformly mixed and evenly spread on the surface of the bottom starch-based foam board, and then the surface starch-based foam board and the bottom starch-based foam board are sealed by hot pressing to obtain a slow-release starch-based fresh-keeping pad. 8. A modified atmosphere fresh-keeping package, characterized in that the chlorine dioxide slow-release starch-based fresh-keeping pad according to any one of claims 1 to 6 is sealed in an outer package. 9. An application of the chlorine dioxide slow-release starch-based fresh-keeping pad according to any one of claims 1 to 6, characterized in that it is used for preserving fresh wet noodles.