Aerogel fresh-keeping pad based on tribute pomelo peel residues as well as preparation method and application of aerogel fresh-keeping pad

Abstract

The invention relates to the technical field of food preservation, and discloses an aerogel preservation pad based on tribute pomelo peel residues as well as a preparation method and application of the aerogel preservation pad. The method comprises the following steps: (1) blanching tribute pomelo peel with boiling water for enzyme deactivation, and soaking to obtain a tribute pomelo peel raw material I; (2) extracting the tribute pomelo peel raw material I to obtain a tribute pomelo peel raw material II and tribute pomelo essential oil; (3) purifying the tribute pomelo peel raw material II to obtain tribute pomelo peel pectin; (4) dispersing the tribute pomelo peel pectin, and performing first contact mixing with a second sodium chloride solution and a potassium hydroxide solution to obtain a stock solution; (5) performing high-pressure homogenization on the tribute pomelo essential oil, a surfactant, a cosurfactant and deionized water to obtain an essential oil nano-emulsion; and (6) carrying out second contact mixing on the stock solution and the essential oil nano-emulsion to obtain the aerogel fresh-keeping pad based on the tribute pomelo peel residues. The prepared aerogel fresh-keeping pad based on the tribute pomelo peel residues is low in cost, high in water absorption, not prone to swelling and disintegration and excellent in antibacterial activity, oxidation resistance and mechanical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of food preservation, and particularly relates to an aerogel fresh-keeping pad based on pomelo peel residue, a preparation method thereof, and an application thereof. Background Art

[0002] During the storage of chilled meat, microbial contamination and spoilage are likely to be caused due to the accumulation of exudate, and the economic losses caused by meat spoilage globally reach tens of billions of US dollars every year. At present, the preservation of chilled meat mainly relies on physical temperature control and chemical preservatives (such as sodium lactate, nitrite), but the former cannot effectively inhibit the growth of psychrophilic bacteria, and the latter has potential food safety risks. As an auxiliary fresh-keeping means, the fresh-keeping pad can absorb exudate, but most commercially available products are made of polypropylene or polyethylene materials, which only have the function of physical water absorption, cannot inhibit the proliferation of microorganisms, and are non-degradable, which will exacerbate "white pollution".

[0003] In recent years, aerogels have been regarded as ideal food packaging materials due to their ultra-low density, high porosity, and adjustable chemical functions. However, existing aerogels are mostly based on synthetic polymers (such as polyurethane, polyimide) or silicon-based materials, which have problems such as high cost, complex production processes, and poor biocompatibility. Although natural polymer-based aerogels are environmentally friendly, they generally have defects such as low mechanical strength, easy swelling and disintegration after water absorption, and lack of antibacterial activity after being prepared into fresh-keeping pads, and it is difficult to meet the dual requirements of chilled meat packaging for material stability and functionality.

[0004] In summary, developing an aerogel fresh-keeping pad with low cost, high water absorption, strong antibacterial property, excellent antioxidant property and mechanical property can not only solve the technical bottleneck of chilled meat preservation, but also promote the development of circular economy, which has significant industrial value and social significance. Summary of the Invention

[0005] The object of the present invention is to solve the problems existing in the prior art, such as high cost in preparing the aerogel fresh-keeping pad, and the prepared aerogel fresh-keeping pad has problems such as low mechanical strength, easy swelling and disintegration after water absorption, and lack of antibacterial activity.

[0006] In order to achieve the above object, the first aspect of the present invention provides a method for preparing an aerogel fresh-keeping pad based on pomelo peel residue, and the method includes the following steps:

[0007] (1) The pomelo peel is successively blanched with boiling water to inactivate enzymes and then soaked in a first sodium chloride solution to obtain pomelo peel raw material I;

[0008] (2) The pomelo peel raw material I is extracted by steam distillation to obtain pomelo peel raw material II and pomelo essential oil;

[0009] (3) Adjust the pH of the pomelo peel raw material II to 2.0 - 3.0, then perform ultrasonic water bath, and then obtain pomelo peel pectin through centrifugation and purification;

[0010] (4) Disperse the pomelo peel pectin in deionized water to obtain a pectin solution with a pectin mass - volume fraction of 2 - 5%, and then perform first - contact mixing of the pectin solution with a second sodium chloride solution and a potassium hydroxide solution to obtain a stock solution;

[0011] (5) Mix the pomelo essential oil with a surfactant, a co - surfactant, and deionized water, and then perform high - pressure homogenization to obtain an essential oil nano - emulsion with an average volume diameter of 50 - 100 nm;

[0012] (6) Add the stock solution to the essential oil nano - emulsion at a dosage volume ratio of 10:1 - 5 for second - contact mixing, and then perform freeze - drying to obtain an aerogel fresh - keeping pad based on pomelo peel residue;

[0013] Among them, the concentrations of the potassium hydroxide solution and the second sodium chloride solution are 0.5 mol / L and 0.8 mol / L respectively.

[0014] The second aspect of the present invention provides an aerogel fresh - keeping pad based on pomelo peel residue prepared by the method described in the first aspect.

[0015] The third aspect of the present invention provides the application of the aerogel fresh - keeping pad based on pomelo peel residue described in the second aspect in the fresh - keeping of chilled meat.

[0016] Compared with the prior art, the method provided by the present invention has at least the following beneficial effects:

[0017] (1) The method provided by the present invention uses pomelo peel residue as a raw material, realizing the high - value utilization of agricultural waste while reducing the raw material cost of preparing the aerogel fresh - keeping pad;

[0018] (2) The method provided by the present invention extracts pectin as an aerogel matrix, and at the same time, by adding sodium chloride and potassium hydroxide, the pomelo pectin forms a more optimized three - dimensional network structure; combined with essential oil loading, the broad - spectrum antibacterial and antioxidant activities of D - limonene and myrcene in the essential oil are optimized;

[0019] (3) The aerogel fresh - keeping pad based on pomelo peel residue prepared by the present invention has both high water absorption, antibacterial (broad - spectrum antibacterial), and antioxidant properties, breaking through the limitations of the single function of existing aerogels; the aerogel fresh - keeping pad based on pomelo peel residue provided by the present invention can extend the shelf life of chilled meat to 15 days, meeting the national standard (total number of colonies ≤ 6 log CFU / g). Description of the Drawings

[0020] Figure 1It is the scanning electron microscope image of the aerogel fresh-keeping pad based on pomelo peel residue prepared in the preferred embodiment of the present invention and the comparative example;

[0021] Figure 2 It is the infrared spectrum of the aerogel fresh-keeping pad based on pomelo peel residue prepared in the preferred embodiment of the present invention and the comparative example. Specific Embodiments

[0022] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0023] As described above, the first aspect of the present invention provides a method for preparing an aerogel fresh-keeping pad based on pomelo peel residue, and the method includes the following steps:

[0024] (1) The pomelo peel is successively blanched with boiling water to inactivate enzymes and then soaked in a first sodium chloride solution to obtain pomelo peel raw material I;

[0025] (2) The pomelo peel raw material I is extracted by steam distillation to obtain pomelo peel raw material II and pomelo essential oil;

[0026] (3) The pH of the pomelo peel raw material II is adjusted to 2.0 - 3.0 and then subjected to ultrasonic water bath, and then pomelo peel pectin is obtained through centrifugation and purification;

[0027] (4) The pomelo peel pectin is dispersed in deionized water to obtain a pectin solution with a pectin mass-volume fraction of 2 - 5%, and then the pectin solution is first contacted and mixed with a second sodium chloride solution and a potassium hydroxide solution to obtain a stock solution;

[0028] (5) The pomelo essential oil is mixed with a surfactant, a co-surfactant, and deionized water and then subjected to high-pressure homogenization to obtain an essential oil nanoemulsion with an average volume diameter of 50 - 100 nm;

[0029] (6) The stock solution is added to the essential oil nanoemulsion at a dosage volume ratio of 10:1 - 5 for second contact and mixing, and then freeze-dried to obtain an aerogel fresh-keeping pad based on pomelo peel residue;

[0030] Wherein, the concentrations of the potassium hydroxide solution and the second sodium chloride solution are 0.5 mol / L and 0.8 mol / L respectively.

[0031] It should be noted that in the present invention, the pectin solution with a pectin mass-volume fraction of 2-5% means that the mass of pectin in the pectin solution accounts for 2% to 5% of the total volume of the pectin solution.

[0032] It should be noted that in the present invention, both the first sodium chloride solution and the second sodium chloride solution are sodium chloride solutions.

[0033] Preferably, in step (1), the time for blanching and inactivating enzymes with boiling water is 3-5 s.

[0034] Preferably, in step (1), the concentration of the first sodium chloride solution is 1 wt%.

[0035] Preferably, in step (1), the soaking time is 25-45 min.

[0036] Preferably, the method of the present invention further includes: in step (2), before performing the extraction, first drain the pomelo peel raw material I, then crush and sieve it to an average volume diameter of 0.3-0.6 mm, and then apply it to the extraction.

[0037] It should be noted that in the present invention, the average volume diameter is measured by dynamic light scattering (DLS).

[0038] Preferably, in step (2), the time for extraction by steam distillation is 2-3 h.

[0039] Preferably, in step (2), the pomelo peel raw material I is mixed with water before the extraction, and the weight ratio of the pomelo peel raw material I to the water is 1:3-5.

[0040] Preferably, the method of the present invention further includes: in step (3), before adjusting the pH of the pomelo peel raw material II to 2.0-3.0, first mix the pomelo peel raw material II with distilled water at a weight ratio of 1:20, and then adjust the pH to 2.0-3.0 using a citric acid solution with a concentration of 0.5 mol / L.

[0041] According to a preferred embodiment, in step (3), the conditions of the ultrasonic water bath at least satisfy: the temperature is 65-75 °C, the time is 50-70 min, and the ultrasonic power is 460-480 W. In this preferred case, it is more beneficial to assist in improving the extraction yield of pomelo pectin.

[0042] Preferably, in step (3), the conditions for centrifugation at least satisfy: the rotation speed is 3800-4100 rpm, and the time is 12-20 min.

[0043] Preferably, the method of the present invention further includes: in step (3), repeating the centrifugation 2-3 times, and collecting the supernatant of each centrifugation for the purification.

[0044] Preferably, in step (3), the purification is carried out using an ethanol solution, and includes the following steps:

[0045] Add 1.5 times the volume of an ethanol solution with a concentration of 95 wt% to the supernatant obtained by centrifugation, mix well, let stand for 2 h, wash with an ethanol solution with a concentration of 75 wt% after flocculent precipitate is formed, filter, place in a constant temperature oven at 60 °C and dry to constant weight, then pulverize and sieve to obtain pomelo peel pectin.

[0046] Preferably, in step (4), the pomelo peel pectin is dispersed in deionized water by means of shear ultrasonic fragmentation.

[0047] More preferably, the conditions of the shear ultrasonic fragmentation at least satisfy: the power is 300-500 W; the time is 5-10 min.

[0048] According to a preferred embodiment, in step (4), the weight ratio of the amounts of the pectin solution, the second sodium chloride solution and the potassium hydroxide solution is 1:0.18-0.5:0.5-0.82. In this preferred case, it is more conducive to achieving the structural stability of the aerogel fresh-keeping pad.

[0049] Preferably, in step (4), the first contact mixing is carried out under stirring conditions, and at least satisfies: the rotation speed is 500-800 rpm, and the time is 20-45 min.

[0050] Preferably, the method of the present invention further includes: in step (5), repeating the high-pressure homogenization 7-9 times, and the pressure of the high-pressure homogenization is 100 Mpa. In this preferred case, it is more conducive to realizing the slow release of essential oil in the aerogel fresh-keeping pad.

[0051] Preferably, in step (5), the surfactant is selected from at least one of Tween 80, sucrose stearate, and sucrose palmitate.

[0052] Preferably, in step (5), the co-surfactant is 1,2-propanediol and / or glycerol.

[0053] Preferably, in step (6), the volume ratio of the amount of the stock solution to the essential oil nanoemulsion is 10:3. In this preferred case, it is more conducive to improving the antioxidant activity of the aerogel fresh-keeping pad.

[0054] Preferably, in step (6), the second contact mixing is carried out under stirring conditions and at least satisfies: the rotation speed is 450 - 600 rpm and the time is 0.8 - 1.5 h.

[0055] Preferably, the method of the present invention further includes: in step (6), before carrying out the freeze-drying, the product of the second contact mixing is first frozen at -80 °C for 12 h.

[0056] Preferably, in step (6), the conditions of the freeze-drying are controlled such that the water content of the prepared aerogel fresh-keeping pad based on Gongyou pomelo peel residue is 1 - 3 wt%.

[0057] As described above, the second aspect of the present invention provides an aerogel fresh-keeping pad based on Gongyou pomelo peel residue prepared by the method described in the first aspect.

[0058] Preferably, the density of the aerogel fresh-keeping pad based on Gongyou pomelo peel residue is 0.05 - 0.15 g / cm 3 , and the water absorption rate is not less than 300 wt%.

[0059] As described above, the third aspect of the present invention provides the application of the aerogel fresh-keeping pad based on Gongyou pomelo peel residue described in the second aspect in the fresh-keeping of chilled meat.

[0060] Preferably, the chilled meat is selected from at least one of beef, pork and poultry meat.

[0061] According to a preferred embodiment, the application of the present invention further includes: placing the aerogel fresh-keeping pad based on Gongyou pomelo peel residue on the surface of the chilled meat and storing it under refrigeration conditions at 2 - 8 °C, and the shelf life is extended to 12 - 15 days.

[0062] The present invention is described in detail below through examples. Without special instructions, the raw materials used are all ordinary commercially available products.

[0063] Gongyou pomelo peel: It is fresh Gongyou pomelo peel with a water content of 60 - 75 wt%;

[0064] Surfactant: It is Tween 80, purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd.;

[0065] Co-surfactant: It is 1,2-propanediol, purchased from Wuhan Huaxiang Kejie Biotechnology Co., Ltd.;

[0066] First sodium chloride solution: The concentration is 1 wt%.

[0067] Example 1

[0068] This example is used to illustrate that the method for preparing the aerogel fresh-keeping pad based on Gongyou pomelo peel residue provided by the present invention is carried out according to the following steps:

[0069] (1) After rinsing the fresh pomelo peel with clear water to remove impurities, it was blanched in boiling water for 5 s to inactivate enzymes and then soaked in the first sodium chloride solution for 30 min to obtain pomelo peel raw material I.

[0070] (2) The pomelo peel raw material I was drained, then crushed and sieved to an average volume diameter of 0.43 mm. Then, the pomelo peel raw material I was mixed with water (the dosage weight ratio was 1:3) and extracted by steam distillation for 3 h to obtain pomelo peel raw material II and pomelo essential oil.

[0071] (3) The pomelo peel raw material II was mixed with distilled water at a dosage weight ratio of 1:20. Then, the pH was adjusted to 2.0 using a citric acid solution with a concentration of 0.5 mol / L. Then, it was subjected to ultrasonic water bath for 60 min at 70 °C and an ultrasonic power of 480 W, and then centrifuged twice (the rotation speed was 4000 rpm and the centrifugation time for each time was 15 min).

[0072] All the supernatant obtained by centrifugation was collected, 1.5 times the volume of an ethanol solution with a concentration of 95 wt% was added, and it was fully mixed and allowed to stand for 2 h. After flocculent precipitate was formed, it was washed with an ethanol solution with a concentration of 75 wt%, filtered, and placed in a constant temperature oven at 60 °C to be dried to a constant weight. Then, it was crushed and sieved to obtain pomelo peel pectin.

[0073] (4) The pomelo peel pectin was dispersed in deionized water by shear ultrasonic fragmentation (power: 300 W; time: 10 min) to obtain a pectin solution with a mass volume fraction of 5%. Then, the pectin solution was mixed with the second sodium chloride solution (0.8 mol / L) and potassium hydroxide solution (0.5 mol / L) at a dosage weight ratio of 1:0.35:0.65 and a rotation speed of 500 rpm for the first contact mixing for 30 min to obtain a stock solution.

[0074] (5) The pomelo essential oil was mixed with a surfactant, a co-surfactant, and deionized water under a pressure of 100 Mpa and then subjected to 8 times of high-pressure homogenization to obtain an essential oil nanoemulsion with an average volume diameter of 50 - 100 nm.

[0075] (6) Then, the stock solution was added to the essential oil nanoemulsion at a dosage volume ratio of 10:3 and a rotation speed of 500 rpm for the second contact mixing for 1 h. Subsequently, it was placed in a circular mold with a diameter of 10.0 mm, and then frozen in a refrigerator at -80 °C for 12 h and freeze-dried until the water content was 2 wt% to obtain an aerogel fresh-keeping pad based on pomelo peel residue, named P1.

[0076] Example 2

[0077] This example is carried out in a similar manner to Example 1. The difference is that in step (6), the volume ratio of the stock solution to the essential oil nanoemulsion is 10:2;

[0078] Finally, an aerogel fresh-keeping pad based on pomelo peel residue is obtained and named P2.

[0079] Example 3

[0080] This example is carried out in a similar manner to Example 1. The difference is that in step (6), the volume ratio of the stock solution to the essential oil nanoemulsion is 10:4;

[0081] Finally, an aerogel fresh-keeping pad based on pomelo peel residue is obtained and named P3.

[0082] Example 4

[0083] This example is carried out in a similar manner to Example 1. The difference is that in step (4), the weight ratio of the pectin solution, the second sodium chloride solution, and the potassium hydroxide solution is 1:0.1:0.1;

[0084] Finally, an aerogel fresh-keeping pad based on pomelo peel residue is obtained and named P4.

[0085] Example 5

[0086] This example is carried out in a similar manner to Example 1. The difference is that in step (4), the weight ratio of the pectin solution, the second sodium chloride solution, and the potassium hydroxide solution is 1:1:1;

[0087] Finally, an aerogel fresh-keeping pad based on pomelo peel residue is obtained and named P5.

[0088] Comparative Example 1

[0089] This comparative example is carried out in a similar manner to Example 1. The difference is that the second sodium chloride solution, the potassium hydroxide solution, and the pomelo essential oil are not used, specifically including;

[0090] S1. After rinsing the fresh pomelo peel with water to remove impurities, it is blanched in boiling water for 5 s to inactivate enzymes and then soaked in the first sodium chloride solution for 30 min to obtain pomelo peel raw material I;

[0091] S2. Drain the pomelo peel raw material I, then crush and sieve it to an average volume diameter of 0.43 mm. Then, mix the pomelo peel raw material I with water (weight ratio of 1:3) and extract it by steam distillation for 3 h to obtain pomelo peel raw material II and pomelo essential oil;

[0092] S3. Mix the pomelo peel raw material II and distilled water at a weight ratio of 1:20, then adjust the pH to 2.0 with a 0.5 mol / L citric acid solution, and then perform ultrasonic water bath for 60 min at 70 °C and an ultrasonic power of 480 W. Then perform centrifugation twice (rotation speed: 4000 rpm, each centrifugation time: 15 min);

[0093] Collect all the supernatant obtained by centrifugation, add an ethanol solution with a concentration of 95 wt% at a volume 1.5 times that of the supernatant, mix well, let it stand for 2 h, wash it with an ethanol solution with a concentration of 75 wt% after flocculent precipitate appears, filter it, and place it in a constant temperature oven at 60 °C to dry to constant weight. Then, after pulverization and sieving, pomelo peel pectin is obtained;

[0094] S4. Disperse the pomelo peel pectin in deionized water by means of shear ultrasonic fragmentation to obtain a pectin solution with a mass volume fraction of 5%;

[0095] S5. Then stir and mix the pectin solution at a rotation speed of 500 rpm for 1 h, then place it in a circular mold with a diameter of 10.0 mm, and then freeze it in a refrigerator at -80 °C for 12 h, and then freeze it in a refrigerator at -80 °C for 12 h. After freeze-drying until the moisture content is 3 wt%;

[0096] Finally, an aerogel fresh-keeping pad based on pomelo peel residue is obtained and named DP1.

[0097] Comparative Example 2

[0098] This comparative example is carried out by a method similar to that of Example 1. The difference is that in step (6), pomelo essential oil is not used, specifically including:

[0099] (6) Then stir and mix the stock solution at a rotation speed of 500 rpm for 1 h, then place it in a circular mold with a diameter of 10.0 mm, and then freeze it in a refrigerator at -80 °C for 12 h. After freeze-drying until the moisture content is 3 wt%;

[0100] Finally, an aerogel fresh-keeping pad based on pomelo peel residue is obtained and named DP2.

[0101] Comparative Example 3

[0102] This comparative example is carried out by a method similar to that of Example 1. The difference is that in step (4), the concentrations of the second sodium chloride solution and potassium hydroxide solution are 0.8 mol / L and 0.6 mol / L respectively;

[0103] Finally, an aerogel fresh-keeping pad based on pomelo peel residue is obtained and named DP3.

[0104] Comparative Example 4

[0105] This comparative example was carried out using a method similar to that of Example 1. The difference is that in step (4), the concentrations of the second sodium chloride solution and the potassium hydroxide solution are 0.6 mol / L and 0.5 mol / L, respectively;

[0106] Finally, an aerogel fresh-keeping pad based on pomelo peel residue was obtained and named DP4.

[0107] Test Example 1

[0108] Detect the physical and chemical properties of the aerogel fresh-keeping pads based on pomelo peel residue (hereinafter referred to as samples) prepared in the above partial examples:

[0109] 1. Mechanical properties: First, use a texture analyzer to measure the texture properties of the samples; perform two compressions, and compress the samples to 50% of their initial height at 5 mm / s through a cylindrical probe with a diameter of 36 mm. The results are expressed in hardness. Some results are shown in Table 1;

[0110] 2. Water absorption capacity (WAC): Cut a certain amount of the sample, weigh it, then immerse it in a centrifuge tube filled with 30 mL of distilled water, and then weigh it after soaking at 4 °C for 24 h to evaluate the WAC of the sample. Some results are shown in Table 1;

[0111] 3. Water vapor sorption capacity (WVSC): Cut a certain amount of the sample from the aerogel fresh-keeping pad based on pomelo peel residue and record its initial weight. Place the sample in a desiccator at a temperature of 25 °C and a humidity of 100%. After the sample reaches a constant weight, use an analytical balance to record the weight increase value as the water vapor transmission rate to evaluate the water vapor sorption capacity of the sample. Some results are shown in Table 1;

[0112] 4. Density: Measure the weight of each sample using an analytical balance, and use an electronic vernier caliper to measure the diameter and height of the sample at three different positions to confirm the sample volume, and then calculate the density of each sample. Some results are shown in Table 2;

[0113] 5. Microscopic morphology: Use SEM (scanning electron microscope) analysis to observe the surface and cross-sectional microstructures of the samples. The samples are cryo-fractured into small pieces with a thickness of less than about 1 mm using liquid nitrogen and directly placed on the sample stage. Under the condition of an acceleration voltage of 10 kV and a magnification of 50×, use SEM to observe the morphology of the samples. Some results are shown in Figure 1 ;

[0114] 6. Infrared analysis: Use the FTIR spectral ATR accessory to analyze the samples in the wavenumber range between 4000 - 600 cm -1 with a resolution of 4 cm -1 Some results are shown in Figure 2 ;

[0115] 7. Antioxidant performance: It was determined by the DPPH method and the ABTS method, and the scavenging effect of superoxide radicals of the samples was determined by electron spin resonance spectroscopy. Some results are shown in Table 2.

[0116] Table 1

[0117] Parameter P1 P4 P5 DP3 DP4 Hardness (N) 3842 3512 3733 2136 2696 Water Absorption Rate (wt%) 410 330 350 80 0 Water Vapor Transmission Rate (%) 22.3 17.4 16.3 7.0 6.1

[0118] Table 2

[0119] Parameter P1 P2 P3 DP1 DP2 <![CDATA[Density (g / cm 3 )]]> 0.058 0.059 0.056 0.047 0.046 Superoxide Radical Scavenging Rate (%) 66.05 52.49 57.32 6.05 12.56

[0120] It can be seen from the results that due to its high porosity and nano-porous structure, aerogels usually show brittleness. However, second sodium chloride solutions and potassium hydroxide solutions with specific concentrations can connect polymer chains or particles through chemical bonds to form a three-dimensional network structure, significantly improving the compressive, tensile strength and flexibility of the materials, thereby enhancing their durability and application scope.

[0121] On this basis, with the synergistic effect of pomelo essential oil, the aerogel fresh-keeping pad can form more pores, enhance its mechanical properties, and at the same time greatly improve its antioxidant activity.

[0122] Application test example 1

[0123] The aerogel fresh-keeping pad based on pomelo peel residues prepared in the above partial examples (hereinafter referred to as the sample) was subjected to an application test for fresh chilled beef preservation:

[0124] 1. Juice loss rate: The sample was cut into blocks of 2*2*1 cm, taken out and the juice on the surface was dried with filter paper, then its mass was weighed and the value was recorded as M2. Compared with the initial mass M1 of the sample, the juice loss rate W of fresh chilled beef per day was calculated by the following formula. Some results are shown in Table 3, where P0 is the blank control group;

[0125] W% = (M1 - M2) ÷ M1 × 100%

[0126] Table 3

[0127] Juice Loss Rate (wt%) P0 P1 P2 P3 DP1 DP2 Day 6 16.2 7.1 9.0 8.3 10.3 11.4 Day 12 27.2 12.3 14.5 14.2 20.7 19.54

[0128] 2. Total number of colonies: Referring to GB 4789.2-2022 "National Food Safety Standard Food Microbiology Examination Determination of Total Number of Colonies", the total number of colonies of fresh chilled beef per day during the refrigerated preservation of fresh chilled beef using the sample was determined. Some results are shown in Table 4, and P0 is the blank control group.

[0129] Table 4

[0130] Total Colony Count (lg CFU / g) P0 P1 P2 P3 DP1 DP2 Day 6 6.06 3.51 3.67 3.90 4.47 4.23 Day 12 7.18 5.02 5.34 5.78 6.07 6.15

[0131] The results show that since the water content in chilled fresh meat plays a crucial role in the quality and storage of meat, controlling the water in the meat and promptly absorbing the excess liquid flowing out of the meat is beneficial to extending the shelf life of the meat. It can be shown that P1, P2, and P3 have excellent water absorption ability, can promptly absorb the excess liquid seeping out of beef, and maintain themselves without being dissolved.

[0132] In addition, according to the food standard of GB / T 17238-2008 "Fresh and Frozen Cut Beef", it is clearly stipulated that the total number of colonies of fresh and frozen cut fresh beef should be less than or equal to 6 logCFU / g. If the total bacterial count is higher than 6 logCFU / g, the sample is considered to be spoiled. The total number of colonies of P0 reached 6.06 logCFU / g on the 6th day, indicating that the beef without using the aerogel pad was spoiled on the 6th day and increased to 7.18 logCFU / g on the 12th day, seriously exceeding the standard. While the total number of colonies of P1, P2, and P3 on the 12th day were 5.02 logCFU / g, 5.34 logCFU / g, and 5.78 logCFU / g respectively, all lower than the national standard. It can be seen that the aerogel fresh-keeping pad based on pomelo peel residue prepared by the present invention can effectively alleviate the growth and reproduction of bacteria, thereby extending the shelf life of chilled fresh meat.

[0133] From the above results, it can be seen that the aerogel fresh-keeping pad based on pomelo peel residue prepared by the present invention has low cost, high water absorption, is not easily swollen and disintegrated, and has excellent antibacterial, antioxidant, and mechanical properties.

[0134] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing an aerogel fresh-keeping pad based on pomelo peel residue, characterized in that: The method comprises the following steps: (1) blanching the pomelo peel in boiling water to inactivate enzymes and then soaking it in a first sodium chloride solution to obtain a pomelo peel raw material I; (2) extracting the tribute pomelo peel raw material I by steam distillation to obtain the tribute pomelo peel raw material II and tribute pomelo essential oil; (3) adjusting the pH of the pomelo peel raw material II to 2.0-3.0, performing an ultrasonic water bath, and then centrifuging and purifying to obtain pomelo peel pectin; (4) dispersing the pomelo peel pectin in deionized water to obtain a pectin solution with a pectin mass volume fraction of 2-5%, and then contacting and mixing the pectin solution with a second sodium chloride solution and a potassium hydroxide solution to obtain a stock solution; (5) mixing the tribute grapefruit essential oil with a surfactant, a co-surfactant, and deionized water, and then performing high-pressure homogenization to obtain an essential oil nanoemulsion with an average volume diameter of 50-100 nm; (6) adding the reserve solution to the essential oil nanoemulsion at a volume ratio of 10:1-5 for a second contact mixing, and then freeze-drying to obtain an aerogel fresh-keeping pad based on Gongyou peel residue; Wherein, the concentrations of the potassium hydroxide solution and the second sodium chloride solution are 0.5 mol / L and 0.8 mol / L respectively.

2. The method according to claim 1, characterized in that The method further comprises: in step (2), before the extraction, draining the tribute pomelo peel raw material I, then crushing and sieving it to an average volume diameter of 0.3-0.6 mm, and then applying it to the extraction.

3. The method according to claim 1 or 2, characterized in that: In step (3), the conditions of the ultrasonic water bath at least meet the following requirements: temperature of 65-75°C, time of 50-70 min, and ultrasonic power of 460-480 W.

4. The method according to claim 1 or 2, characterized in that: In step (4), the pomelo peel pectin is dispersed in deionized water by shearing and ultrasonic crushing.

5. The method according to claim 1 or 2, characterized in that: In step (4), the weight ratio of the pectin solution, the second sodium chloride solution and the potassium hydroxide solution is 1:0.18-0.5:0.5-0.

82.

6. The method according to claim 1 or 2, characterized in that: In step (6), the second contact mixing is carried out under stirring conditions and at least meets the following conditions: a rotation speed of 450-600 rpm and a time of 0.8-1.5 h.

7. An aerogel fresh-keeping pad based on pomelo peel residue prepared by the method described in any one of claims 1 to 6.

8. The aerogel fresh-keeping pad based on pomelo peel residue according to claim 7, characterized in that: The density of the aerogel fresh-keeping pad based on Gongyou peel residue is 0.05-0.15 g / cm 3 , water absorption rate is not less than 300wt%.

9. Use of the aerogel fresh-keeping pad based on pomelo peel residue according to claim 7 or 8 in the preservation of cold fresh meat.

10. The use according to claim 9, characterized in that: The application comprises: placing the aerogel fresh-keeping pad based on pomelo peel residue on the surface of the cold fresh meat, storing it under refrigeration conditions of 2-8° C., and extending the shelf life to 12-15 days.

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