A comprehensive utilization method of jujube processing waste

Abstract

The application discloses a comprehensive utilization method of jujube processing waste, and belongs to the technical field of resource utilization of agricultural product processing waste. The application realizes efficient separation of jujube pulp and jujube core by adopting pectinase and cellulase complex treatment technology, and obtains pure jujube core with purity greater than or equal to 99%; the separated pure jujube core can be further processed into high-performance activated carbon particles or a capacitor material, jujube juice obtained by separation is concentrated to obtain concentrated jujube juice, or is subjected to spray drying after concentration to obtain jujube powder, and the jujube powder is used for preparation of jujube powder, beverages, yogurt and fermentation of probiotics, so that full-component and high-value resource conversion of jujube processing waste is realized. The process is simple, green and environmentally friendly, and the cost is controllable, the resource utilization rate and economic benefits of the jujube processing industry are effectively improved, environmental pollutant emissions are reduced, and the process has a significant industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization technology of agricultural product processing waste, specifically involving a comprehensive utilization method for jujube processing waste, and particularly involving a technology for separating jujube flesh and pit based on enzymatic hydrolysis and high-value utilization of jujube pit. Background Technology

[0002] Jujubes, a traditional Chinese agricultural product that is both food and medicine, are rich in polysaccharides, vitamins, minerals, and other nutrients, and have wide applications in the food, health product, and pharmaceutical industries. The jujube processing industry is large-scale, generating a significant amount of processing waste during the drying, candied fruit, and juice production processes. This waste mainly includes jujube pulp residue, pits, and mixtures of both, accounting for approximately 30%-50% of the raw jujube weight.

[0003] Currently, the disposal methods for jujube processing waste are relatively extensive. Most enterprises use methods such as stockpiling, landfilling, or incineration, which not only causes serious resource waste but also leads to environmental problems such as soil and air pollution. A few studies have attempted to utilize jujube processing waste, such as directly crushing it as feed or organic fertilizer raw material. However, because the jujube pulp and pits are not separated, the product quality is poor and the overall benefits are low. Some studies have also tried to extract active ingredients from the jujube pulp residue, but the utilization rate of the jujube pits is extremely low, and the problem of resource waste still exists.

[0004] The main components of jujube pits are cellulose, hemicellulose, and lignin, possessing excellent potential for porous structure and making them a high-quality raw material for preparing porous materials such as activated carbon and capacitor materials. However, in existing technologies, the jujube flesh and pits are tightly bound together in jujube processing waste, making efficient separation difficult and hindering the acquisition of pure jujube pits, thus limiting their high-value utilization. Traditional separation methods, such as mechanical grinding, are not only inefficient but also prone to pit breakage, affecting subsequent utilization; chemical reagent separation methods introduce harmful substances, pollute the environment, and also affect the subsequent application of the separated products.

[0005] Therefore, researching and developing a comprehensive utilization method for jujube processing waste that can achieve efficient and green separation of jujube pulp and jujube pits, and can make full-component high-value utilization of the separated jujube pit and pulp residue, has important practical significance and industrial application value. Summary of the Invention

[0006] To address the problems of low utilization rate of jujube processing waste, difficulty in separating jujube flesh from pits, and limited high-value utilization of jujube pits, the present invention aims to provide a comprehensive utilization method for jujube processing waste. This method utilizes a combined enzymatic hydrolysis technology of pectinase and cellulase to achieve efficient and green separation of jujube flesh and pits, obtaining pure jujube pits. These pure pits are then processed into activated carbon particles or capacitor materials, while simultaneously achieving the recycling of jujube flesh residue, thus realizing the goal of full-component utilization of resources.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for the comprehensive utilization of jujube processing waste, comprising the following steps: (1) Raw material enzymatic hydrolysis and separation: The waste generated from the processing of jujube juice is added to water or buffer solution to make a suspension, and then pectinase and cellulase are added for compound enzymatic hydrolysis reaction. After solid-liquid separation, pure jujube pits and jujube juice are obtained respectively. (2) High-value utilization of pure jujube kernels: The pure jujube kernels obtained in step (1) are dried and activated to prepare activated carbon particles; or they are dried, carbonized and doped to prepare capacitor materials. (3) Comprehensive processing of jujube juice: The jujube juice obtained in step (1) is concentrated to obtain concentrated jujube juice, or concentrated and then spray-dried to obtain jujube powder, which is used to prepare jujube powder, beverages, yogurt and probiotic fermentation.

[0009] Based on the above technical solution, further, the buffer solution in step (1) includes citrate-sodium citrate buffer and phosphate buffer, with a pH value of 4.0~7.0, and the solid-liquid ratio of jujube processing waste to water or buffer solution is 1:3-1:20 g / mL.

[0010] Based on the above technical solution, further, the amount of pectinase added in step (1) is 0.01%~1% of the amount of waste material from jujube processing, and the enzyme activity of pectinase is ≥4000 U / g; the amount of cellulase added is 0.1~2% of the amount of waste material from jujube processing, and the enzyme activity of cellulase is ≥9000 U / g.

[0011] Based on the above technical solution, further, the conditions for the compound enzymatic hydrolysis reaction in step (1) are: the reaction temperature is 30~55℃, the reaction time is 1~10h, and the stirring is continuous during the reaction with a stirring speed of 50~200 r / min.

[0012] Based on the above technical solution, further, the solid-liquid separation in step (1) adopts centrifugal separation method, with a centrifugal speed of 3000~5000 r / min and a centrifugal time of 5~30min.

[0013] The core innovation of step (1) lies in the use of a combination of pectinase and cellulase enzymatic hydrolysis technology: In the waste of jujube processing, the content of jujube skin is low, and the jujube flesh and jujube pit are connected by sticky substances such as pectin and cellulose. Pectinase can specifically decompose pectin substances, and cellulase can decompose cellulose. The combination of the two can synergistically destroy the connection structure between jujube flesh and jujube pit, so as to achieve efficient separation of jujube flesh and jujube pit. Compared with traditional mechanical or chemical separation methods, it has the advantages of high separation efficiency, good jujube pit integrity, green environmental protection and no introduction of pollutants. The purity of the separated pure jujube pit can reach ≥99%, which can meet the requirements of subsequent high-value utilization.

[0014] Based on the above technical solution, the specific process for preparing activated carbon particles in step (2) is as follows: the pure jujube kernels are dried to constant weight at 60~80℃, and then heated to 600~800℃ under inert gas protection for activation. The activation time is 1~5 h. After cooling to room temperature, the kernels are crushed to 80~120 mesh to obtain activated carbon particles.

[0015] Based on the above technical solution, the activated carbon particles further have a well-developed pore structure, a large specific surface area, and excellent adsorption performance, and can be used in wastewater treatment, air purification and other fields.

[0016] Based on the above technical solution, the inert gas mentioned in step (2) further includes nitrogen, helium, argon and neon; the heating rate is 5~10℃ / min.

[0017] Based on the above technical solution, the specific process of preparing capacitor material in step (2) is as follows: the pure jujube pit is dried to constant weight at 60~80℃, and then heated to 800~1000℃ under inert gas protection for carbonization for 2~6 h; dopant is added to the obtained carbonization product and then doped at 500~700℃ for 1~3 h. After cooling, it is crushed to 100~150 mesh to obtain capacitor material.

[0018] Based on the above technical solution, the capacitor material further exhibits good conductivity and electrochemical properties, and can be used in energy storage devices such as supercapacitors.

[0019] Based on the above technical solution, the inert gas mentioned in step (2) further includes nitrogen, helium, argon and neon; the heating rate is 5~10℃ / min.

[0020] Based on the above technical solution, further, the dopant in step (2) is one or a mixture of two of phosphorus source dopant and nitrogen source dopant, wherein the phosphorus source dopant is ammonium dihydrogen phosphate and the nitrogen source dopant is urea; the amount of dopant added is 5%-15% of the mass of the carbonization product.

[0021] Based on the above technical solution, further, the concentration ratio of the jujube juice in step (3) is 1 to 3 times.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. Achieving efficient and green separation of jujube flesh and pit: This invention innovatively adopts a combined enzymatic hydrolysis technology of pectinase and cellulase to specifically decompose the connecting substances (pectin and cellulose) between jujube flesh and pit, achieving high separation efficiency, with the purity of the jujube pit reaching ≥99% and good pit integrity; the entire separation process does not require the use of harmful chemical reagents, is green and environmentally friendly, has no pollutant emissions, and the separation products can be directly used for subsequent high-value utilization.

[0023] 2. Achieving high-value utilization of all components of jujube processing waste: This invention not only processes the separated pure jujube pits into high-value activated carbon particles or capacitor materials, but also comprehensively utilizes the separated jujube juice to prepare jujube powder and jujube fermentation products, achieving full-component, zero-waste utilization of jujube processing waste and significantly improving resource utilization rate.

[0024] 3. Simple process and controllable cost: The enzyme preparation used in this invention is readily available, the reaction conditions are mild, and there is no need for complex equipment or harsh conditions such as high temperature and high pressure. The process is simple and easy to operate, making it suitable for large-scale industrial production. At the same time, the raw material is waste from jujube processing, which is inexpensive and significantly improves the economic benefits of the jujube processing industry.

[0025] 4. Significant environmental benefits: This invention effectively solves the environmental problems caused by the accumulation and landfilling of jujube processing waste, reduces pollutant emissions, and realizes "turning waste into treasure", which is in line with the concept of green development and has good environmental and social benefits. Attached Figure Description

[0026] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0027] Figure 1 This is a process flow diagram of the comprehensive utilization method for jujube processing waste according to the present invention. Detailed Implementation

[0028] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0029] Example 1: Preparation of activated carbon particles This embodiment provides a method for the comprehensive utilization of jujube processing waste, including the following steps: (1) Raw material collection: Collect the waste generated during the processing of jujube juice (jujube pulp residue, jujube pits and a mixture of the two), and avoid introducing other impurities during the collection process; (2) Enzymatic hydrolysis: The jujube waste from step (1) was added to a citrate-sodium citrate buffer solution (pH=4.8) to prepare a suspension with a solid-liquid ratio of 1:10 (g / mL); 0.3% pectinase (enzyme activity 6000 U / g) and 0.5% cellulase (enzyme activity 12000 U / g) by weight of the jujube waste particles were added to the suspension; the mixture was placed in a 50℃ constant temperature water bath and stirred at 150 r / min for 3 h; after enzymatic hydrolysis, the mixture was centrifuged at 4000 r / min for 15 min to obtain a pure jujube juice supernatant and a precipitate (jujube pits and a small amount of jujube peel); the precipitate was resuspended in water and the supernatant was discarded to obtain pure jujube pits. Sensory and microscopic observation showed that the purity of the pure jujube pits was 99.2%; (3) Preparation of activated carbon particles: The pure jujube pits from step (2) were dried to constant weight at 70℃, then placed in an activation furnace under nitrogen protection, and heated to 700℃ at a rate of 8℃ / min for 2 h. After cooling to room temperature, they were pulverized to 100 mesh to obtain activated carbon particles. The specific surface area of ​​these activated carbon particles was measured to be 1250 m². 2 / g.

[0030] A methylene blue solution (initial concentration 500 mg / L, ensuring adsorption saturation) was selected, and the pH was adjusted to adsorption pH=6 using acid-base methods. 0.05 g of activated carbon granules (m=) were accurately weighed and placed in a 50 mL stoppered conical flask. V=50 mL of the prepared methylene blue solution was added, and the flask was placed in a constant temperature shaking water bath at 25±1℃ and shaken at 150 r / min for 4 h to ensure complete adsorption saturation. After adsorption equilibrium, the mixture was centrifuged at 8000 r / min for 10 min, and the supernatant was collected. The absorbance was measured at 664 nm, and the adsorption concentration was calculated based on the standard curve. The calculated adsorption capacity of the activated carbon granules for methylene blue was 280 mg / g. (4) Concentrated jujube juice: The supernatant of the pure jujube juice in step (2) is concentrated to 1 / 2 of the original volume to obtain concentrated jujube juice (derived from the hydrolysis of jujube pulp, rich in polysaccharides, proteins and other nutrients), or concentrated and spray-dried to obtain jujube powder, which is used to prepare jujube beverages or jujube powder and jujube probiotics.

[0031] Example 2: Preparation of Capacitor Materials This embodiment provides a method for the comprehensive utilization of jujube processing waste, including the following steps: (1) Raw material collection: Collect the waste generated during the processing of jujube juice (jujube pulp residue, jujube pits and a mixture of the two), and avoid introducing other impurities during the collection process; (2) Enzymatic hydrolysis and separation: The jujube waste from step (1) was added to a citrate-sodium citrate buffer (pH=4.5) to prepare a suspension with a solid-liquid ratio of 1:8 (g / mL); 0.2% pectinase (enzyme activity 5000 U / g) and 0.6% cellulase (enzyme activity 10000 U / g) by weight of jujube waste particles were added to the suspension; the mixture was placed in a 48℃ constant temperature water bath and stirred at 120 r / min for 3.5 h; after enzymatic hydrolysis, it was centrifuged at 3500 r / min for 18 min to obtain pure jujube pits and supernatant; the purity of the pure jujube pits was 99.1% according to sensory and microscopic observation. (3) Preparation of capacitor material: The pure jujube pits from step (2) were dried to constant weight at 65°C, placed in a carbonization furnace, protected by argon gas, and heated to 900°C at a heating rate of 6°C / min for 3 h; 10% urea (based on the mass of the carbonization product) was added to the carbonization product, mixed evenly, and then placed in a tube furnace. The temperature was raised to 600°C under argon gas protection and the doping treatment was carried out for 1.5 h; after cooling to room temperature, the material was pulverized to 120 mesh to obtain the capacitor material.

[0032] A three-electrode system and an electrochemical workstation were used to test the performance of the capacitor material using the constant current charge-discharge method. Acetylene black, polytetrafluoroethylene (PTFE), and the capacitor material were mixed uniformly in a mass ratio of 1:1:8, and water was added to form a slurry. This slurry was then uniformly coated onto a 1 square centimeter layer of nickel foam using the dip-coating method, dried, and compacted at 10 MPa to prepare the supercapacitor electrode. An electrochemical testing system was constructed, consisting of the prepared electrode as the working electrode, a platinum or graphite electrode as the counter electrode, and a reference electrode adapted to the corresponding electrolyte. A deoxygenated and defoamed electrolyte was added to the electrolytic cell, immersing all electrodes. The test primarily used constant current charge-discharge (GCD) with cyclic voltammetry (CV) as a supplement. The GCD test was set with a potential window of 0–0.8 V and a charge-discharge current density of 1–10 A / g, and data from the stable plateau was collected after 5–10 cycles. The CV test was set with a scan rate of 5–50 mV / s and the same potential window, with the curve exhibiting an approximately rectangular shape to verify the capacitor behavior. The capacitor material was tested and found to have a specific capacitance of 250 F / g, and a capacitance retention rate of 92% after 10,000 cycles. (4) Concentrated jujube juice: The supernatant of the pure jujube juice in step (2) is concentrated to 1 / 2 of the original volume to obtain concentrated jujube juice (derived from the hydrolysis of jujube pulp, rich in polysaccharides, proteins and other nutrients), or concentrated and spray-dried to obtain jujube powder, which is used to prepare jujube beverages or jujube powder and jujube probiotics.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for comprehensive utilization of jujube processing waste, characterized in that, Includes the following steps: (1) Raw material enzymatic hydrolysis and separation: The waste generated from the processing of jujube juice is added to water or buffer solution to make a suspension, and then pectinase and cellulase are added for compound enzymatic hydrolysis reaction. After solid-liquid separation, pure jujube pits and jujube juice are obtained respectively. (2) High-value utilization of pure jujube kernels: The pure jujube kernels obtained in step (1) are dried and activated to prepare activated carbon particles; or they are dried, carbonized and doped to prepare capacitor materials. (3) Comprehensive processing of jujube juice: The jujube juice obtained in step (1) is concentrated to obtain concentrated jujube juice, or concentrated and then spray-dried to obtain jujube powder, which is used to prepare jujube powder, beverages, yogurt and probiotic fermentation.

2. The method for comprehensive utilization of jujube processing waste according to claim 1, characterized in that, The buffer solution mentioned in step (1) includes citrate-sodium citrate buffer and phosphate buffer, with a pH value of 4.0~7.0, and the solid-liquid ratio of jujube processing waste to water or buffer solution is 1:3-1:20 g / mL.

3. The method for comprehensive utilization of jujube processing waste according to claim 1, characterized in that, The amount of pectinase added in step (1) is 0.01%~1% of the amount of waste material from jujube processing, and the enzyme activity of pectinase is ≥4000 U / g; the amount of cellulase added is 0.1~2% of the amount of waste material from jujube processing, and the enzyme activity of cellulase is ≥9000 U / g.

4. The method for comprehensive utilization of jujube processing waste according to claim 1, characterized in that, The conditions for the compound enzymatic hydrolysis reaction in step (1) are: reaction temperature of 30~55℃, reaction time of 1~10h, continuous stirring during the reaction, stirring speed of 50~200 r / min; the solid-liquid separation adopts centrifugation separation method, centrifugation speed of 3000~5000 r / min, centrifugation time of 5~30min.

5. The method for comprehensive utilization of jujube processing waste according to claim 1, characterized in that, The specific process for preparing activated carbon particles in step (2) is as follows: the pure jujube kernels are dried to constant weight at 60~80℃, and then heated to 600~800℃ under inert gas protection for activation. The activation time is 1~5 h. After cooling to room temperature, the kernels are pulverized to 80~120 mesh to obtain activated carbon particles.

6. The method for comprehensive utilization of jujube processing waste according to claim 5, characterized in that, The inert gas mentioned in step (2) includes nitrogen, helium, argon and neon; the heating rate is 5~10℃ / min.

7. The method for comprehensive utilization of jujube processing waste according to claim 1, characterized in that, The specific process for preparing the capacitor material in step (2) is as follows: the pure jujube pits are dried to constant weight at 60~80℃, and then heated to 800~1000℃ under inert gas protection for carbonization for 2~6 h; dopant is added to the carbonized product and then doped at 500~700℃ for 1~3 h. After cooling, the product is pulverized to 100~150 mesh to obtain the capacitor material.

8. The method for comprehensive utilization of jujube processing waste according to claim 7, characterized in that, The inert gas mentioned in step (2) includes nitrogen, helium, argon and neon; the heating rate is 5~10℃ / min.

9. The method for comprehensive utilization of jujube processing waste according to claim 7, characterized in that, The dopant in step (2) is one or a mixture of two of the following: phosphorus source dopant and nitrogen source dopant. The phosphorus source dopant is ammonium dihydrogen phosphate, and the nitrogen source dopant is urea. The amount of dopant added is 5%-15% of the mass of the carbonization product.

10. The method for comprehensive utilization of jujube processing waste according to claim 1, characterized in that, The concentration factor of the jujube juice mentioned in step (3) is 1 to 3 times.

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