A nanocellulose-based edible preservative liquid, a preparation method and use thereof

Abstract

The application provides a nanocellulose-based edible preservative liquid, a preparation method and a use method thereof. The nanocellulose-based edible preservative liquid comprises a nanocellulose solution, beeswax and glycerol. The preparation method comprises the following steps: mixing the nanocellulose solution, the beeswax and the glycerol according to a proportion and heating to melt the beeswax to obtain a mixed liquid; then, stirring and emulsifying the mixed liquid to obtain a nanocellulose emulsion; finally, performing vacuum defoaming treatment on the nanocellulose emulsion to obtain the nanocellulose-based edible preservative liquid. The application develops an edible and easy-to-wash preservative liquid based on nanocellulose, adopts a dipping coating mode to perform coating film treatment on fruits and vegetables, forms a micro-nano level preservative coating layer on the surface of the fruits and vegetables, can effectively reduce the loss of water and nutrients on the surface and inside of the fruits and vegetables, reduces the gas permeability of the preservative coating layer, and significantly enhances the mechanical strength of the preservative coating layer.

Description

Technical Field

[0001] This invention belongs to the field of fruit and vegetable preservation technology, and relates to a nanocellulose-based edible preservative liquid, its preparation method and usage method. Background Technology

[0002] Fresh agricultural products such as fruits and vegetables suffer particularly severe losses in the post-harvest supply chain due to factors such as dehydration and respiration metabolism. my country is a major consumer of fruit and a major importer of tropical fruits, resulting in 20-30% of its fruit being wasted annually in the post-harvest supply chain, causing significant economic losses. To extend shelf life, various fruit preservation technologies have been developed, such as refrigeration, modified atmosphere packaging (MAP), and preservation coatings. Preservation coatings are transparent, uniform, inert barrier substances applied directly to the fruit's surface. By blocking gases and inhibiting respiration, they reduce moisture loss and fruit shrinkage, thus extending shelf life. Simultaneously, preservation coatings also delay fruit color changes, preserve fruit aroma, and inhibit microbial growth. Due to their excellent performance, ease of application, and controllable cost, preservation coatings are increasingly favored by the food industry and consumers.

[0003] Nanocellulose, due to its excellent film-forming properties, superior gas barrier properties, and outstanding biocompatibility, has been used as a coating matrix component in recent years to prepare fruit and vegetable preservation coatings. However, the inherent hydrophilicity of nanocellulose leads to a decline in the barrier performance of nanocellulose preservation coatings under high relative humidity conditions, and even the destruction of their integrity, rendering them ineffective in preserving freshness. Generally, the water resistance of nanocellulose is enhanced by surface hydrophobic modification or by physical blending with soybean oil, oleic acid, silica, and sunflower oil.

[0004] The modification process is complex, involves toxic reagents, and the inedibility and high cost of the blended components limit the use of edible nanocellulose composite coatings. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an edible preservative liquid based on nanocellulose, its preparation method, and its usage method. The present invention develops an edible and easy-to-wash preservative liquid based on nanocellulose. It uses an immersion coating method to coat fruits and vegetables, forming a micro-nano-scale preservative coating on the surface of the fruits and vegetables. This can effectively reduce the loss of moisture and nutrients on the surface and inside of the fruits and vegetables, reduce the gas permeability of the preservative coating, and significantly enhance the mechanical strength of the preservative coating.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a nanocellulose-based edible preservative liquid, which includes a nanocellulose solution, beeswax, and glycerin.

[0008] This invention develops an edible and easy-to-wash preservative liquid based on nanocellulose. It employs a dip-coating method to coat fruits and vegetables, forming a micro-nano-scale preservative coating on their surface. The nanocellulose, arranged in an interlaced pattern within the coating, obstructs the diffusion paths of water vapor and other small molecules, reducing the loss of moisture and nutrients from the surface and interior of the fruits and vegetables. This also lowers the gas permeability of the coating and significantly enhances its mechanical strength. After coating and drying, beeswax forms a robust film with a certain gas barrier capability on the fruit and vegetable surface. Furthermore, beeswax's excellent hydrophobic properties reduce the coating's sensitivity to moisture, improving its water retention capacity. Glycerin acts as a plasticizer, penetrating into the nanocellulose matrix and increasing the fluidity of the nanocellulose molecular chains, thereby enhancing the coating's toughness and elasticity.

[0009] The nutrient content of fruits and vegetables gradually decreases as respiration occurs. Therefore, reducing respiration can help preserve freshness and effectively prevent nutrient loss. Lowering the oxygen content of the storage environment can slow down the respiration intensity of fruits and vegetables with vigorous respiration. After fruits and vegetables are coated with the preservative solution provided by this invention, the nanocellulose in the preservative solution gives the preservative coating a high gas barrier property, making it difficult for oxygen outside the preservative coating to penetrate into the interior of the fruits and vegetables. At the same time, the fruits and vegetables release CO2 through respiration inside the preservative coating, creating an atmosphere with high CO2 content and low O2 content on the surface of the fruits and vegetables. This inhibits the respiration activity of the preserved objects, slows down the ripening process, and achieves the purpose of modified atmosphere preservation.

[0010] Furthermore, due to the microscopic network structure of nanocellulose molecules, they have strong water retention properties. At the same time, the nanocellulose molecular chains have hydrophilic groups such as hydroxyl groups, which makes the preservative coating have a strong force on water molecules. This can slow down the evaporation of water on the surface of fruits and vegetables, reduce the quality loss of fruits and vegetables, and thus effectively adjust the air humidity and gas environment on the surface of fruits and vegetables, inhibit the water loss rate and the respiration activity of fruits and vegetables during storage, thereby reducing the respiration consumption of fruits.

[0011] Untreated fruits and vegetables often have numerous cracks and wrinkles on their surfaces, providing ample oxygen permeation channels for respiration. Simultaneously, the increased surface area due to these wrinkles leads to greater effective transpiration of water vapor, resulting in rapid moisture loss. This invention, through immersion in a preservative solution, fills and smooths these cracks and wrinkles, reducing the respiration rate and transpiration area of ​​the fruits and vegetables to some extent, thus acting as a barrier between water vapor and oxygen.

[0012] The preservative liquid provided by this invention has good affinity with the surface of fruits and vegetables. During use, it adheres well to and covers the surface of fruits and vegetables, forming a preservative coating that achieves preservation effects such as blocking gases, retaining water, and preventing nutrient loss. Furthermore, compared to some waxy coatings that are difficult or even impossible to wash off, the preservative coating provided by this invention is easily soluble in water. Before consumption, the preservative coating on the surface of fruits and vegetables can be easily removed by rinsing with water, eliminating consumers' concerns about the safety of preservative coatings.

[0013] As a preferred embodiment of the present invention, the mass fraction of the nanocellulose solution is 0.5-1.5 wt%, for example, it can be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, or 1.5 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0014] This invention specifically limits the mass fraction of the nanocellulose solution to 0.5-1.5 wt%. When the mass fraction of the nanocellulose solution is less than 0.5 wt%, the viscosity of the preservative solution is too low due to the low concentration of nanocellulose, which affects the adhesion of the preservative solution to the surface of fruits and vegetables. Therefore, it is not easy to form a complete preservative coating on the surface of fruits and vegetables by dip coating, and the preservation effect is not achieved. When the mass fraction of the nanocellulose solution is higher than 1.5 wt%, the viscosity of the preservative solution is too high due to the high concentration of nanocellulose, and the fruit and vegetable preservative solution will gel, affecting its processing performance. It is impossible to prepare a preservative coating by dip coating, and the prepared preservative coating will have uneven thickness, affecting the actual preservation effect.

[0015] As a preferred embodiment of the present invention, the amount of beeswax added is 20-50 wt% based on the dry weight of nanocellulose in the nanocellulose solution. For example, it can be 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, or 50 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] This invention uses beeswax as a film-forming agent. The amount of film-forming agent added directly affects the internal structure of the preservation coating, thereby affecting its comprehensive properties such as water vapor transmission rate, oxygen transmission rate, elongation at break, and tensile strength. Because beeswax contains fatty acids, the hydroxyl groups in the nanocellulose molecular chains interact with the carboxylic acids in the fatty acids through hydrogen bonding and electrostatic interactions. This allows the nanocellulose in the preservation coating to be arranged in a tight and orderly manner, giving the coating a dense network structure and improving its oxygen barrier and water retention capabilities.

[0017] This invention specifically limits the amount of beeswax added to 20-50 wt%. When the amount of beeswax added is less than 20 wt%, it cannot enhance the water barrier and water resistance properties. When the amount of beeswax added exceeds 50 wt%, the hydrophobic and emulsifying effects of beeswax weaken the bonding between nanocellulose molecules, leading to a significant decrease in the tensile strength and elongation at break of the preservation coating. Furthermore, excessive beeswax addition causes discontinuous crystallization in the preservation coating, disrupting the three-dimensional network formed by nanocellulose and resulting in poor oxygen barrier properties. It also leads to uneven stress distribution within the preservation coating, deteriorating mechanical properties. Simultaneously, some lipids precipitate, reducing the smoothness of the preservation coating surface, ultimately resulting in a significant decrease in the tensile strength and elongation at break of the preservation coating. This invention comprehensively considers the impact of the amount of beeswax added on various properties of the preservation coating and particularly optimizes the beeswax addition amount to 20-50 wt%.

[0018] As a preferred embodiment of the present invention, the amount of glycerol added is 20-50 wt% based on the dry weight of the nanocellulose in the nanocellulose solution. For example, it can be 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, 42 wt%, 44 wt%, 46 wt%, 48 wt%, or 50 wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] The amount of glycerol added significantly affects the performance of the preservation coating. As glycerol is a small organic molecule, adding an appropriate amount can increase the interaction between nanocellulose molecules and beeswax molecules, and also fill the gaps in the nanocellulose network structure, enhancing the density of the preservation coating. This makes it difficult for moisture and oxygen to permeate the coating, further improving its water retention and oxygen barrier capabilities. Secondly, the addition of glycerol as a plasticizer allows it to penetrate into the nanocellulose matrix. The addition of glycerol reduces the intermolecular forces between nanocellulose molecular chains, activating them and making them easier to slide, increasing the fluidity of the nanocellulose molecular chains and improving the toughness and elasticity of the preservation coating. Thirdly, the hydroxyl groups in the glycerol molecules form hydrogen bonds with the carboxyl groups on the nanocellulose molecular chains, enhancing the intermolecular interactions of the preservation coating and increasing its tensile strength and elongation at break.

[0020] This invention specifically limits the amount of glycerol added to 20-50 wt%. When the amount of glycerol added is less than 20 wt%, the brittleness of nanocellulose leads to cracking of the preservative coating, rendering it ineffective for preservation. However, when the amount of glycerol added exceeds 50 wt%, the fluidity of the nanocellulose molecular chains is further enhanced, leading to increased porosity between the nanocellulose molecular chains and reduced density of the cellulose-based preservative inner layer. This, in turn, promotes increased oxygen permeability, resulting in a decrease in the oxygen barrier capacity of the cellulose-based preservative inner layer. Furthermore, excessively high amounts of glycerol enhance the softening effect of glycerol on the cellulose-based preservative inner layer, thereby weakening its rigidity and reducing its tensile strength. Considering the comprehensive impact of the amount of glycerol added on various properties of the cellulose-based preservative inner layer, this invention particularly optimizes the amount of glycerol added to 20-50 wt%.

[0021] As a preferred embodiment of the present invention, the nanocellulose solution is composed of nanocellulose and water.

[0022] In some preferred embodiments, the nanocellulose comprises cellulose nanofibers and / or cellulose nanocrystals.

[0023] As a preferred technical solution of the present invention, the nanocellulose is cellulose nanofiber and cellulose nanocrystal.

[0024] Nanocellulose includes cellulose nanofibers and cellulose nanocrystals. This invention uses a specific ratio of cellulose nanofibers and cellulose nanocrystals to effectively improve the gas barrier properties of the preservation coating and the stability of the preservation liquid.

[0025] In improving the gas barrier properties of food preservation coatings, cellulose nanocrystals are extracted from the crystalline regions of microfibers through strong acid hydrolysis of disordered cellulose. They are highly crystalline rod-shaped structures with lengths of several hundred nanometers and diameters of less than one hundred nanometers. Cellulose nanofibers, on the other hand, are fibrous structures with high aspect ratios, ranging in length from several micrometers to tens of micrometers and diameters of less than 100 nanometers. They can form a three-dimensional network structure through physical entanglement. The porous structure within the food preservation coating is the main channel for oxygen permeation. This invention combines cellulose nanofibers and cellulose nanocrystals in a specific ratio. Through the physical entanglement of the cellulose nanofibers, a three-dimensional network structure with a certain degree of porosity is formed. The highly crystalline rod-shaped cellulose nanocrystals can be embedded within this three-dimensional network structure, thereby increasing the density of the food preservation coating. This dense network structure increases the tortuosity of gas passage within the coating, thus reducing oxygen permeability.

[0026] In terms of improving the storage stability of preservative solutions, the performance of nanocellulose in stabilizing emulsions is mainly related to its morphology and hydrophilic / hydrophobic properties. Shorter cellulose nanocrystals are more rigid and can be tightly adsorbed onto the surface of emulsion droplets during the stabilization process, but they are prone to emulsion flocculation. Longer cellulose nanofibers are more flexible and are mainly distributed in the aqueous phase in a three-dimensional network structure, which can inhibit emulsion flocculation.

[0027] This invention combines cellulose nanofibers and cellulose nanocrystals to achieve a synergistic effect. Shorter cellulose nanocrystals are tightly adsorbed at the oil / water interface, while longer cellulose nanofibers form bridging structures between adjacent emulsion droplets and create a three-dimensional network structure within the continuous phase, improving the storage stability of the preservative solution. Furthermore, cellulose nanofibers, as a matrix material, impart excellent barrier properties to the coating by forming a three-dimensional network. The high crystallinity and small size of cellulose nanocrystals allow them to fill the three-dimensional network of cellulose nanofibers as nanoscale additives, thereby reducing the free volume of the coating and enhancing its barrier properties and mechanical strength.

[0028] In some preferred embodiments, the mass ratio of the cellulose nanofibers to the cellulose nanocrystals is (1-3):1, for example, it can be 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0029] This invention further specifies that the mass ratio of cellulose nanofibers to cellulose nanocrystals is (1-3):1. When the proportion of cellulose nanocrystals added is low, the cellulose nanocrystals cannot completely coat the emulsion droplets. At this time, the emulsion droplets will aggregate, resulting in a gradual increase in particle size. Emulsion instability leads to the precipitation and stratification of the oil phase in the preservative liquid, resulting in poor stability of the preservative liquid. In addition, due to the reduced proportion of cellulose nanocrystals, the free volume of the coating increases, and the gas barrier performance deteriorates. As the proportion of cellulose nanocrystals added increases, a sufficient number of cellulose nanocrystals adsorb onto the surface of the emulsion droplets and form a dense monolayer interfacial film, thereby preventing the emulsion droplets from contacting each other. At this time, the size of the emulsion droplets will be reduced to a minimum and remain basically unchanged. As the proportion of cellulose nanocrystals added continues to increase, the cellulose nanocrystals will form a multilayer dense interfacial film on the surface of the emulsion droplets or form a gel network structure in the continuous phase, which can effectively prevent the aggregation between emulsion droplets, making the emulsion system of the preservative liquid more stable. However, when the proportion of cellulose nanocrystals added to the preservative liquid is too high, the cellulose nanocrystals in the dispersed phase of the preservative liquid are prone to agglomeration and emulsion flocculation, which leads to instability of the preservative liquid. In addition, the proportion of cellulose nanofibers decreases accordingly, resulting in a reduction of the three-dimensional network structure in the preservative coating matrix, which ultimately affects the gas barrier performance of the preservative coating.

[0030] Secondly, the present invention provides a method for preparing the nanocellulose-based edible preservative liquid described in the first aspect, the preparation method comprising:

[0031] Nanocellulose solution, beeswax, and glycerin are mixed in a certain proportion and heated until the beeswax melts to obtain a mixture; then, the mixture is stirred and emulsified to obtain a nanocellulose emulsion; finally, the nanocellulose emulsion is subjected to vacuum degassing treatment to obtain the nanocellulose-based edible preservative liquid.

[0032] This invention uses safe, non-toxic, and low-cost agricultural waste beeswax and nanocellulose to prepare a Pickering emulsion (preservative liquid) with preservation function through high-temperature emulsification. The preservative liquid is applied to the surface of fruits and vegetables by coating, impregnation, coating or spraying, and a film is formed on the surface to form a preservative coating, which can effectively extend the storage period and freshness period of fruits and vegetables.

[0033] Compared with other physical or chemical preservation materials, the biomass material preservation liquid provided by this invention has excellent biodegradability. The preparation process does not require the addition of toxic or harmful chemical reagents, making it environmentally friendly and in line with the development concept of green chemistry.

[0034] The preservation coating formed by the edible preservation liquid provided by this invention has selective air permeability and anti-permeability, which can prevent the migration of moisture and nutrients on the surface and inside of fruits and vegetables, thus preventing food spoilage. This extends the storage and freshness period of fruits and vegetables, and improves their oxygen-barrier and water-retention capacity. Fruits and vegetables coated with the preservation liquid provided by this invention can still retain an intact preservation coating after being soaked in water for 24 hours. Therefore, the preservation liquid provided by this invention can be used in fruit and vegetable preservation application scenarios under extreme conditions of high relative humidity.

[0035] Furthermore, the preservative coating formed on the surface of fruits and vegetables can improve their mechanical strength, thereby enhancing their safety during production, storage, and transportation. This prevents damage and spoilage caused by bumps and knocks, reducing the rate of spoiled fruit. Simultaneously, the preservative liquid provided by this invention can also serve as a carrier for food additives (such as preservatives, pigments, flavorings, and antioxidants), allowing the active ingredients in these additives to exert their effects on the surface of fruits and vegetables and controlling the diffusion rate of these additives to achieve a slow-release effect.

[0036] As a preferred technical solution of the present invention, the heating temperature is 80-90℃, for example, it can be 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃ or 90℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] In some preferred embodiments, the stirring and emulsification time is 1-10 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] Thirdly, the present invention provides a method for using the nanocellulose-based edible preservative liquid described in the first aspect, the method comprising:

[0039] Soak the fruits and vegetables to be preserved in a nanocellulose-based edible preservative solution at least once. After soaking, remove the fruits and vegetables and let them air dry naturally to form a preservative coating on the surface of the fruits and vegetables.

[0040] As a preferred technical solution of the present invention, the single soaking time is 5-60s, for example, it can be 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s or 60s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In some preferred embodiments, the number of soakings is 2 to 5 times, for example, 2, 3, 4 or 5 times, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] This invention develops an edible and easy-to-wash preservative liquid based on nanocellulose. It employs a dip-coating method to coat fruits and vegetables, forming a micro-nano-scale preservative coating on their surface. The nanocellulose, arranged in an interlaced pattern within the coating, obstructs the diffusion paths of water vapor and other small molecules, reducing the loss of moisture and nutrients from the surface and interior of the fruits and vegetables. This also lowers the gas permeability of the coating and significantly enhances its mechanical strength. After coating and drying, beeswax forms a robust film with a certain gas barrier capability on the fruit and vegetable surface. Furthermore, beeswax's excellent hydrophobic properties reduce the coating's sensitivity to moisture, improving its water retention capacity. Glycerin acts as a plasticizer, penetrating into the nanocellulose matrix and increasing the fluidity of the nanocellulose molecular chains, thereby enhancing the coating's toughness and elasticity.

[0044] The nutrient content of fruits and vegetables gradually decreases as respiration occurs. Therefore, reducing respiration can help preserve freshness and effectively prevent nutrient loss. Lowering the oxygen content of the storage environment can slow down the respiration intensity of fruits and vegetables with vigorous respiration. After fruits and vegetables are coated with the preservative solution provided by this invention, the nanocellulose in the preservative solution gives the preservative coating a high gas barrier property, making it difficult for oxygen outside the preservative coating to penetrate into the interior of the fruits and vegetables. At the same time, the fruits and vegetables release CO2 through respiration inside the preservative coating, creating an atmosphere with high CO2 content and low O2 content on the surface of the fruits and vegetables. This inhibits the respiration activity of the preserved objects, slows down the ripening process, and achieves the purpose of modified atmosphere preservation.

[0045] Furthermore, due to the microscopic network structure of nanocellulose molecules, they have strong water retention properties. At the same time, the nanocellulose molecular chains have hydrophilic groups such as hydroxyl groups, which makes the preservative coating have a strong force on water molecules. This can slow down the evaporation of water on the surface of fruits and vegetables, reduce the quality loss of fruits and vegetables, and thus effectively adjust the air humidity and gas environment on the surface of fruits and vegetables, inhibit the water loss rate and the respiration activity of fruits and vegetables during storage, thereby reducing the respiration consumption of fruits.

[0046] Untreated fruits and vegetables often have numerous cracks and wrinkles on their surfaces, providing ample oxygen permeation channels for respiration. Simultaneously, the increased surface area due to these wrinkles leads to greater effective transpiration of water vapor, resulting in rapid moisture loss. This invention, through immersion in a preservative solution, fills and smooths these cracks and wrinkles, reducing the respiration rate and transpiration area of ​​the fruits and vegetables to some extent, thus acting as a barrier between water vapor and oxygen.

[0047] The preservative liquid provided by this invention has good affinity with the surface of fruits and vegetables. During use, it adheres well to and covers the surface of fruits and vegetables, forming a preservative coating that achieves preservation effects such as blocking gases, retaining water, and preventing nutrient loss. Furthermore, compared to some waxy coatings that are difficult or even impossible to wash off, the preservative coating provided by this invention is easily soluble in water. Before consumption, the preservative coating on the surface of fruits and vegetables can be easily removed by rinsing with water, eliminating consumers' concerns about the safety of preservative coatings. Attached Figure Description

[0048] Figure 1 Microscopic images of emulsion droplets of the preservative solution provided in Embodiment 1 of the present invention;

[0049] Figure 2 This is a droplet size distribution curve of the preservative solution provided in Embodiment 1 of the present invention;

[0050] Figure 3 The images show the appearance of bananas used in the banana preservation test provided in Embodiment 1 and the comparative example of the present invention. Detailed Implementation

[0051] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0052] Example 1

[0053] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid, the preparation method specifically including the following steps:

[0054] A nanocellulose solution, beeswax, and glycerin were mixed in a specific ratio and heated to 80°C until the beeswax melted to obtain a mixture. The nanocellulose solution had a mass fraction of 0.5 wt%, and the mass ratio of cellulose nanofibers to cellulose nanocrystals in the nanocellulose solution was 1:1. Based on the dry weight of the nanocellulose in the nanocellulose solution, the amount of beeswax added was 20 wt%, and the amount of glycerin added was 20 wt%.

[0055] The mixture was emulsified at high speed for 1 minute using a high-speed blender to obtain a nanocellulose emulsion; subsequently, the nanocellulose emulsion was subjected to vacuum degassing treatment to obtain the nanocellulose-based edible preservative liquid.

[0056] This embodiment also provides a method for using a nano-cellulose-based edible preservative liquid, the method specifically including the following steps:

[0057] Freshly picked bananas are soaked twice in a nanocellulose-based edible preservative solution for 60 seconds each time. After soaking, the bananas are removed and air-dried naturally to form a preservative coating on the banana surface.

[0058] The preservative solution prepared in Example 1 was subjected to microscopic observation and photographs, and the results were as follows: Figure 1 The image shown is a micrograph of the emulsion; the particle size distribution of the emulsion droplets in the preservative solution was tested, and the results are as follows. Figure 2 The emulsion droplet size distribution curve shown is combined with... Figure 1 and Figure 2 It can be seen that the droplet size of the emulsion in the preservation liquid prepared in this embodiment is mainly concentrated in the range of 2.2-2.3 μm.

[0059] Example 2

[0060] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid, the preparation method specifically including the following steps:

[0061] A nanocellulose solution, beeswax, and glycerin were mixed in a specific ratio and heated to 82°C until the beeswax melted to obtain a mixture. The nanocellulose solution had a mass fraction of 0.8 wt%, and the mass ratio of cellulose nanofibers to cellulose nanocrystals in the nanocellulose solution was 1.5:1. Based on the dry weight of the nanocellulose in the nanocellulose solution, the amount of beeswax added was 30 wt%, and the amount of glycerin added was 30 wt%.

[0062] The mixture was ultrasonically stirred and emulsified for 2 minutes using an ultrasonic crusher to obtain a nanocellulose emulsion; subsequently, the nanocellulose emulsion was subjected to vacuum degassing treatment to obtain the nanocellulose-based edible preservative liquid.

[0063] This embodiment also provides a method for using a nano-cellulose-based edible preservative liquid, the method specifically including the following steps:

[0064] Freshly picked bananas are soaked three times in a nanocellulose-based edible preservative solution for 40 seconds each time. After soaking, the bananas are removed and air-dried naturally to form a preservative coating on the surface of the bananas.

[0065] Example 3

[0066] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid, the preparation method specifically including the following steps:

[0067] A nanocellulose solution, beeswax, and glycerin were mixed in a specific ratio and heated to 85°C until the beeswax melted to obtain a mixture. The nanocellulose solution had a mass fraction of 1 wt%, and the mass ratio of cellulose nanofibers to cellulose nanocrystals in the nanocellulose solution was 2:1. Based on the dry weight of the nanocellulose in the nanocellulose solution, the amount of beeswax added was 35 wt%, and the amount of glycerin added was 35 wt%.

[0068] The mixture was homogenized and emulsified for 5 minutes using a handheld homogenizer to obtain a nanocellulose emulsion; subsequently, the nanocellulose emulsion was subjected to vacuum degassing treatment to obtain the nanocellulose-based edible preservative liquid.

[0069] This embodiment also provides a method for using a nano-cellulose-based edible preservative liquid, the method specifically including the following steps:

[0070] Freshly picked bananas were soaked in a nanocellulose-based edible preservative solution four times, for 30 seconds each time. After soaking, the bananas were removed and air-dried naturally to form a preservative coating on the surface of the bananas.

[0071] Example 4

[0072] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid, the preparation method specifically including the following steps:

[0073] A nanocellulose solution, beeswax, and glycerin were mixed in a specific ratio and heated to 88°C until the beeswax melted to obtain a mixture. The nanocellulose solution had a mass fraction of 1.2 wt%, and the mass ratio of cellulose nanofibers to cellulose nanocrystals in the nanocellulose solution was 2.5:1. Based on the dry weight of the nanocellulose in the nanocellulose solution, the amount of beeswax added was 40 wt%, and the amount of glycerin added was 40 wt%.

[0074] The mixture was emulsified at high speed for 7 minutes using a high-speed blender to obtain a nanocellulose emulsion; subsequently, the nanocellulose emulsion was subjected to vacuum degassing treatment to obtain the nanocellulose-based edible preservative liquid.

[0075] This embodiment also provides a method for using a nano-cellulose-based edible preservative liquid, the method specifically including the following steps:

[0076] Freshly picked bananas were soaked in a nanocellulose-based edible preservative solution four times, for 10 seconds each time. After soaking, the bananas were removed and air-dried naturally to form a preservative coating on the surface of the bananas.

[0077] Example 5

[0078] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid, the preparation method specifically including the following steps:

[0079] A nanocellulose solution, beeswax, and glycerin were mixed in a specific ratio and heated to 90°C until the beeswax melted to obtain a mixture. The nanocellulose solution had a mass fraction of 1.5 wt%, and the mass ratio of cellulose nanofibers to cellulose nanocrystals in the nanocellulose solution was 3:1. Based on the dry weight of the nanocellulose in the nanocellulose solution, the amount of beeswax added was 50 wt%, and the amount of glycerin added was 50 wt%.

[0080] The mixture was ultrasonically stirred and emulsified for 10 minutes using an ultrasonic crusher to obtain a nanocellulose emulsion; subsequently, the nanocellulose emulsion was subjected to vacuum degassing treatment to obtain the nanocellulose-based edible preservative liquid.

[0081] This embodiment also provides a method for using a nano-cellulose-based edible preservative liquid, the method specifically including the following steps:

[0082] Freshly picked bananas are soaked in a nanocellulose-based edible preservative solution five times, for five seconds each time. After soaking, the bananas are removed and air-dried naturally to form a preservative coating on the banana surface.

[0083] Example 6

[0084] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that the mass fraction of the nanocellulose solution is adjusted to 0.3 wt%, while the other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0085] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0086] Example 7

[0087] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that the mass fraction of the nanocellulose solution is adjusted to 1.8 wt%, while the other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0088] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0089] Example 8

[0090] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and Example 1 is that the amount of beeswax added is adjusted to 15 wt%, while other process parameters and operating steps are exactly the same as in Example 1.

[0091] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0092] Example 9

[0093] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and Example 1 is that the amount of beeswax added is adjusted to 55 wt%, while other process parameters and operating steps are exactly the same as in Example 1.

[0094] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0095] Example 10

[0096] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that the amount of glycerol added is adjusted to 15 wt%, while the other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0097] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0098] Example 11

[0099] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that the amount of glycerol added is adjusted to 55 wt%, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0100] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0101] Example 12

[0102] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that the mass ratio of cellulose nanofibers to cellulose nanocrystals is adjusted to 0.5:1, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0103] This embodiment also provides a method for using a nanocellulose-based edible preservative liquid. Freshly picked bananas are dipped in the preservative liquid provided in this embodiment, and the treatment process is the same as in Example 1.

[0104] Example 13

[0105] This embodiment provides a method for preparing a nanocellulose-based edible preservative liquid. The difference between this method and that of Embodiment 1 is that the mass ratio of cellulose nanofibers to cellulose nanocrystals is adjusted to 5:1, while other process parameters and operating steps are exactly the same as those of Embodiment 1.

[0106] Comparative Example

[0107] This comparative example uses freshly picked bananas, without any preservation treatment.

[0108] The water vapor permeability and oxygen permeability of the preservation coatings provided in Examples 1-13 were tested, and the specific test steps are as follows:

[0109] (1) Water vapor transmission coefficient of the preservation coating

[0110] The water vapor barrier properties of the food preservation coating were tested in accordance with the national standard GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Films and Sheets - Cup Weight Gain and Weight Loss Method".

[0111] (2) Oxygen permeability coefficient of the preservation coating

[0112] The oxygen barrier performance was tested using an oxygen permeation meter. The specific method was as follows: one side of the coating film was filled with pure oxygen, and the other side was evacuated. Due to the osmotic pressure difference between the two sides of the film, oxygen permeated through the pure oxygen side of the film into the vacuum side. The oxygen barrier performance of the preservation coating could be obtained by monitoring the pressure change on the vacuum side.

[0113] The test results are shown in Table 1.

[0114] Appearance is crucial for the sale of fruits and vegetables, directly affecting their commercial value. This invention uses banana preservation as an example. After harvesting, bananas gradually soften, the peel changes from green to yellow, then turns brown with spots, and the flesh softens until it rots and spoils. This invention uses the preservation solutions provided in Example 1 and the comparative example to treat freshly picked bananas by immersion, and observes and photographs the appearance of the bananas every one day.

[0115] The appearance of bananas before and after preservation treatment provided in Example 1 and the comparative example are as follows: Figure 3 As shown, by the 5th day of storage, the bananas in the comparative example began to brown on the surface, developing numerous large patches of black spots. In contrast, the bananas in Example 1, treated with the preservative solution, only showed a few black spots and maintained a good appearance and quality. By the 9th day of storage, the bananas in the comparative example were completely browned, softened, and began to rot, rendering them inedible. While the bananas in Example 1, treated with the preservative solution, showed some browning, they did not show obvious signs of rotting and remained edible.

[0116] The weight loss rate, vitamin C content, and firmness of the bananas provided in Examples 1-13 and the comparative examples were tested. The specific test steps are as follows:

[0117] (1) Weight loss rate

[0118] The weight was measured during storage. The bananas were weighed and recorded as m0 on day 0 of storage. After 9 days of storage in a constant temperature and humidity environment (ambient temperature 25℃, relative humidity 50%), the bananas were weighed and recorded as m0. n The weight loss rate w (%) is calculated using the following formula:

[0119]

[0120] (2) Vitamin C content

[0121] The vitamin C content in bananas was determined according to the third method of the national standard GB 5009.86-2016 "National Food Safety Standard - Determination of Ascorbic Acid in Food" - 2,6-dichlorophenolindophenol titration method.

[0122] (3) Hardness

[0123] The hardness of bananas before and after preservation treatment during storage was determined using a GY-4 digital fruit hardness tester. A 5mm diameter planar probe was inserted into 5 circumferential positions at the largest longitudinal section of the banana to obtain 5 sets of hardness values, and the average value was taken.

[0124] The test results are shown in Table 1.

[0125] Table 1

[0126] <![CDATA[Water vapor transmission coefficient kg·m / (s·m 2 ·Pa)]]> <![CDATA[Oxygen Permeability Coefficient cm 3 ·μm / (m 2 ·day·kPa)]]> Weight loss rate % Vitamin C content (mg / 100g) Hardness N Example 1 <![CDATA[9.8×10 -12 ]]> 150 9.8 12.6 12.8 Example 2 <![CDATA[8.3×10 -12 ]]> 145 8.2 13.2 15.2 Example 3 <![CDATA[6.1×10 -12 ]]> 136 6.6 14.5 16.3 Example 4 <![CDATA[5.3×10 -12 ]]> 118 5.3 15.8 17.7 Example 5 <![CDATA[7.4×10 -12 ]]> 130 7.3 15.2 14.5 Example 6 <![CDATA[13.3×10 -12 ]]> 168 13.5 10.3 10.5 Example 7 <![CDATA[9.7×10 -12 ]]> 146 12.3 11.5 11.8 Example 8 <![CDATA[12.8×10 -12 ]]> 162 12.8 9.5 10.3 Example 9 <![CDATA[10.3×10 -12 ]]> 153 11.2 10.7 11.2 Example 10 <![CDATA[12.1×10 -12 ]]> 160 12.5 9.8 10.5 Example 11 <![CDATA[11.4×10 -12 ]]> 158 11.7 10.2 10.7 Example 12 <![CDATA[10.5×10 -12 ]]> 157 11.5 10.5 11.0 Example 13 <![CDATA[10.0×10 -12 ]]> 155 10.2 12.0 12.5 Comparative Example - - 14.2 8.1 9.2

[0127] As can be seen from the test data provided in Examples 1-5 and the comparative examples, the water vapor transmission coefficient of the preservation coating prepared by the present invention is 5 × 10⁻⁶. -12 -10×10 -12 kg·m / (s·m 2 Within the range of Pa, the oxygen permeability coefficient is 110-150 cm⁻¹. 3 ·μm / (m 2 The reading (·day·kPa) indicates that the preservation coating prepared by this invention has excellent oxygen barrier and water retention capabilities.

[0128] As shown in Table 1, the weight loss rate of bananas after 9 days of storage was 8-10%, far lower than that of the comparative example. The vitamin C content of bananas after 9 days of storage was 12-17 mg / 100g, and the firmness was 12-18 N, both significantly higher than the comparative example. Observation of the bananas' appearance revealed that applying the preservative solution provided in this invention to bananas for immersion preservation can extend their shelf life by 4-6 days.

[0129] The test data provided in Examples 1, 6, and 7 show that in Example 6, the mass fraction of the nanocellulose solution was too low, resulting in a low viscosity of the preservative solution, which affected the adhesion of the preservative solution to the surface of fruits and vegetables. Therefore, it was not easy to form a complete preservative coating on the surface of fruits and vegetables by dip coating, which ultimately affected the preservation effect on bananas. In Example 7, the mass fraction of the nanocellulose solution was too high, which caused the fruit and vegetable preservative solution to gel, affecting its processing performance. The preservative coating prepared by dip coating was uneven in thickness, which affected the actual preservation effect.

[0130] The test data provided in Examples 1, 8, and 9 show that in Example 8, the amount of beeswax added was too low, which failed to enhance the moisture barrier and water resistance properties, ultimately affecting the preservation effect on bananas. In Example 9, the amount of beeswax added was too high, resulting in discontinuous crystallization of beeswax in the preservation coating, which damaged the three-dimensional network formed by nanocellulose, leading to poor oxygen barrier properties and ultimately affecting the preservation effect on bananas.

[0131] The test data provided in Examples 1, 10, and 11 show that in Example 10, the amount of glycerol added was too low, causing the preservative coating to crack and failing to achieve a preservation effect. In Example 11, the amount of glycerol added was too high, reducing the density of the preservative coating and thus promoting oxygen permeability, which decreased the oxygen barrier capacity of the preservative coating and ultimately affected the preservation effect on bananas.

[0132] The test data provided in Examples 1, 12, and 13 show that in Example 12, the proportion of cellulose nanofibers was relatively low, resulting in a reduction in the three-dimensional network structure composed of cellulose nanofibers in the preservation coating, which worsened the barrier properties of the preservation coating and ultimately affected the preservation effect on bananas. In Example 13, the proportion of cellulose nanocrystals was relatively low, resulting in a larger free volume of the coating, which worsened the gas barrier properties and ultimately affected the preservation effect on bananas.

[0133] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A nanocellulose-based edible preservative liquid, characterized in that, The nanocellulose-based edible preservative liquid comprises a nanocellulose solution, beeswax, and glycerin; the nanocellulose solution has a mass fraction of 0.5-1.5 wt%. The amount of beeswax added is 20-50 wt% based on the dry weight of the nanocellulose in the nanocellulose solution. The amount of glycerol added is 20-50 wt% based on the dry weight of the nanocellulose in the nanocellulose solution. The nanocellulose solution is composed of nanocellulose and water; The nanocellulose is composed of cellulose nanofibers and cellulose nanocrystals; the mass ratio of the cellulose nanofibers to the cellulose nanocrystals is (1-3):

1. The preparation method of the nanocellulose-based edible preservative liquid includes: Nanocellulose solution, beeswax, and glycerin are mixed in a certain proportion and heated until the beeswax melts to obtain a mixture; then, the mixture is stirred and emulsified to obtain a nanocellulose emulsion; finally, the nanocellulose emulsion is subjected to vacuum degassing treatment to obtain the nanocellulose-based edible preservative liquid. The heating temperature is 80-90℃; The stirring and emulsification time is 1-10 minutes; The method of using the nanocellulose-based edible preservative liquid includes: Soak the fruits and vegetables to be preserved in nanocellulose-based edible preservative solution at least once. After soaking, remove the fruits and vegetables and let them air dry naturally to form a preservative coating on the surface of the fruits and vegetables. The soaking time for a single soak is 5-60 seconds; The soaking is performed 2-5 times.

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