A method for preparing low-solvent residual vitamin C

Abstract

The application relates to the technical field of industrialized preparation of vitamin C, and discloses a preparation method of vitamin C with low solvent residue, which comprises the following steps: (1) corn starch hydrochloric acid hydrolysis; (2) aspergillus niger fermentation; (3) citric acid acidification treatment; (4) cation exchange resin purification; (5) reduced pressure concentration and gradient crystallization; (6) sectional vacuum drying; (7) particle grading; (8) microfiltration-ultrafiltration membrane separation; (9) ultraviolet sterilization; and (10) nitrogen filling packaging. Through optimization of hydrolysis conditions (hydrochloric acid concentration 0.8-1.0%, 50+ / -2 DEG C), fermentation control (AS3.758 strain, 30+ / -0.5 DEG C), resin purification (sulfonic acid type resin, 6.5-7.2% ammonium sulfate elution) and sectional drying process, the product has a solvent residue lower than 2 ppm, a purity greater than or equal to 99.9%, and the stability is obviously improved. The application has the advantages of environmental protection and high yield, and is suitable for the production of medical and food grade vitamin C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial preparation of vitamin C, in particular to a preparation method of vitamin C with low solvent residue. BACKGROUND

[0002] Vitamin C (ascorbic acid) is an important water-soluble vitamin, widely used in the fields of medicine, food, cosmetics, etc. The traditional preparation methods of vitamin C mainly include chemical synthesis and fermentation, among which the fermentation method has become the mainstream process due to its environmental friendliness and lower cost. However, the vitamin C products prepared by the existing fermentation method often have problems such as high solvent residue, insufficient purity, poor stability, etc., which affect its application in high-end fields.

[0003] At present, in the purification process after fermentation, the conventional process often uses organic solvents (such as methanol, ethanol) for extraction and crystallization, which makes it difficult to control the solvent residue in the final product. In addition, some processes lack effective protection measures at the sterilization and packaging links, making the vitamin C easily oxidized and degraded, reducing the product quality. Therefore, it is of great industrial value to develop a preparation method of vitamin C with low solvent residue, high purity and excellent stability. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a preparation method of vitamin C with low solvent residue, which solves the problem that some processes lack effective protection measures at the sterilization and packaging links, making the vitamin C easily oxidized and degraded, reducing the product quality.

[0005] In order to achieve the above purpose, the present application discloses a preparation method of vitamin C with low solvent residue, comprising the following steps:

[0006] Step (1) corn starch is mixed with 0.5-1.2% hydrochloric acid solution with a mass ratio of 1:5-8, and hydrolysis reaction is carried out at 45-55℃ for 1.5-2.5h, then anhydrous ethanol is added to terminate the reaction, and centrifugal separation is carried out to obtain a hydrolysate;

[0007] Step (2) the hydrolysate is inoculated into a fermenter with Aspergillus niger spores at a volume ratio of 1:0.03-0.05, the temperature is controlled at 28-32℃, sterile air is introduced to maintain the dissolved oxygen content at 20-30%, and after fermentation for 48-72h, the pH is adjusted to 6.8-7.2;

[0008] Step (3) citric acid is added to the fermentation broth to adjust the pH to 2.0-2.5, the temperature is raised to 70-80℃ and kept for 0.5-1h, and centrifugal separation is carried out to remove the mycelium and obtain a crude vitamin C solution;

[0009] Step (4) the crude product solution was passed through a cation exchange resin column, which was sequentially rinsed with deionized water, 0.1 mol / L NaOH solution and 0.05 mol / L HCl solution, and then gradient eluted with 5-8% ammonium sulfate solution;

[0010] Step (5) the eluate was collected and concentrated under reduced pressure at 40-45°C to a solid content of 50-60%, crystal seeds were added and the temperature was decreased to 4-6°C at a rate of 0.5-1°C / min, and the crystals were separated by centrifugation after crystallization for 8-12h;

[0011] Step (6) the crystals were placed in a vacuum drying oven, the vacuum degree was controlled at -0.08~-0.1 MPa, and the temperature was increased to 50°C in stages for drying for 3-4h, and then decreased to 35°C for drying for 6-8h;

[0012] Step (7) the dried product was graded through a 200-300 mesh vibrating screen, and particles with a particle size of 80-150μm were collected;

[0013] Step (8) the particles were dispersed in ultrapure water to form a 10-15% suspension, which was sequentially treated by passing through a 0.45μm microfiltration membrane and a 1000Da ultrafiltration membrane;

[0014] Step (9) the filtrate was sterilized by ultraviolet irradiation at an irradiation intensity of 30-50mW / cm² for 15-30s;

[0015] Step (10) the sterilized solution was aseptically dispensed into aluminum foil composite film packaging bags, which were sealed after being filled with nitrogen and stored in the dark.

[0016] Preferably, in step (1), the concentration of the hydrochloric acid solution is 0.8-1.0%, the mass ratio of corn starch to hydrochloric acid solution is 1:6-7, the hydrolysis temperature is 50±2°C, and the reaction time is 2-2.2h.

[0017] Preferably, in step (2), the Aspergillus niger strain is AS3.758, the fermentation temperature is controlled at 30±0.5°C, the dissolved oxygen content is 25-28%, and the fermentation period is 60-65h.

[0018] Preferably, in step (4), the cation exchange resin is a sulfonic acid type resin, the height to diameter ratio of the resin column is 6:1-8:1, the elution flow rate is 1.5-2.0BV / h, and the concentration of the ammonium sulfate solution is 6.5-7.2%.

[0019] Preferably, in step (5), the amount of crystal seeds added is 0.03-0.05% of the mass of the concentrated solution, the cooling rate is 0.8-1.0°C / min, and the crystallization end point temperature is 5±0.5°C.

[0020] Preferably, the vacuum drying in step (6) is divided into three stages: the first stage is preheating at 20-30℃ for 0.5h, the second stage is drying at 45-50℃ for 2.5-3h, and the third stage is constant temperature drying at 35℃ for 7-7.5h.

[0021] Preferably, the operating pressure of the microfiltration membrane in step (8) is 0.15-0.2MPa, the transmembrane pressure difference of the ultrafiltration membrane is 0.25-0.3MPa, and the temperature of the feed liquid is maintained at 10-15℃.

[0022] Preferably, the wavelength of the ultraviolet light in step (9) is 254nm, the irradiation intensity is 40±5mW / cm², and the suspension transmission speed is 15-20cm / s.

[0023] Preferably, the nitrogen filling purity in step (10) is ≥99.999%, the oxygen permeability of the packaging bag is ≤0.5cm³ / (m²·24h·0.1MPa), and the ambient humidity during the dispensing is ≤15%RH.

[0024] Preferably, the addition amount of citric acid in step (3) is 1.2-1.5% of the volume of the fermentation liquid, the acidification end point pH value is 2.2-2.3, and the centrifuge speed is 8000-10000r / min.

[0025] Beneficial effects:

[0026] After the hydrolysis reaction is completed, anhydrous ethanol is added to terminate the reaction, and in the subsequent separation, purification and drying processes, vacuum concentration, vacuum drying and other technologies are used to maximize the removal of solvents, thereby preparing vitamin C with low solvent residue, meeting the strict requirements of high-end fields such as medicine and food for product quality and safety.

[0027] During the preparation process, cation exchange resin columns are used for separation and purification, and by selecting appropriate resin types, column height-diameter ratios and elution conditions, impurities can be effectively removed; combined with microfiltration and ultrafiltration membrane treatment, further removal of small particles and macromolecular impurities is achieved; ultraviolet irradiation sterilization treatment ensures the microbial safety of the product. These measures work together to significantly improve the purity and quality of vitamin C products and enhance the market competitiveness of the products.

[0028] The hydrolysis reaction, fermentation process and subsequent various process parameters are accurately controlled, such as determining the suitable hydrochloric acid concentration, the starch and hydrochloric acid solution ratio, the hydrolysis temperature and time in the hydrolysis step, selecting the specific Aspergillus niger species and controlling the fermentation temperature, the dissolved oxygen content and the period in the fermentation step, so that the reaction can be more fully and efficiently carried out, the utilization rate of raw materials is improved, the production cycle is shortened, and the overall production efficiency is improved, and the production cost is reduced. The preparation method reduces the use amount and residual amount of the solvent by optimizing the process, reduces the energy consumption and cost of subsequent solvent recovery treatment, meanwhile, the segmented temperature rising drying method is used in the drying process, the energy is reasonably utilized, the waste of energy is avoided, the development trend of energy saving and environmental protection is met, and good social and economic benefits are obtained. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a process flow chart of the preparation method of the low-solvent-residual vitamin C. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0031] Embodiment 1:

[0032] Step (1): 100 kg of corn starch is mixed with 600 kg of hydrochloric acid solution with a mass concentration of 0.8%, and is placed in a hydrolysis reactor, and is heated to 50 DEG C for constant temperature hydrolysis reaction for 2 h. After the reaction is completed, 200 L of anhydrous ethanol is added to terminate the reaction, and is centrifuged at a speed of 8000 r / min for 15 min, and the supernatant is collected as a hydrolysis solution.

[0033] Step (2): The hydrolysis solution and AS3.758 Aspergillus niger spores are mixed according to a volume ratio of 1:0.04 and are introduced into a 50 m³ fermentation tank, the temperature is controlled at 30±0.5 DEG C, sterile air is introduced to maintain the dissolved oxygen content at 25%, and after 62 h of fermentation, 10% sodium hydroxide solution is used to adjust the pH to 7.0.

[0034] Step (3): 1.3% of citric acid is added to the fermentation solution, the pH is adjusted to 2.2, the temperature is raised to 75 DEG C and is kept for 45 min, and is centrifuged at a speed of 9000 r / min for 20 min to remove the mycelium, and a crude vitamin C solution is obtained.

[0035] Step (4): The crude product solution was passed through a sulfonic acid type cation exchange resin column (column height-diameter ratio 7:1) at a flow rate of 1.8 BV / h, and sequentially washed with 3 BV of deionized water, 2 BV of 0.1 mol / L NaOH solution and 2 BV of 0.05 mol / L HCl solution, and finally gradient eluted with 6.8% ammonium sulfate solution, and the eluate with conductivity in the range of 15-20 mS / cm was collected.

[0036] Step (5): The eluate was concentrated under reduced pressure at 42°C to a solid content of 55%, 0.04% by mass of crystal seeds were added, and the temperature was decreased to 5±0.5°C at a rate of 0.8°C / min, and the crystals were separated by centrifugation after crystallization for 10 h.

[0037] Step (6): The crystals were placed in a vacuum drying oven, and dried in three stages: preheating at 25°C for 0.5 h in the first stage, drying at 48°C for 2.8 h in the second stage, and constant temperature drying at 35°C for 7.2 h in the third stage, with a vacuum degree of -0.09 MPa.

[0038] Step (7): The dried product was classified by a 250-mesh vibrating screen, and particles with a particle size of 90-140 μm were collected.

[0039] Step (8): The particles were dispersed in ultrapure water to form a 12% suspension, passed through a 0.45 μm microfiltration membrane at an operating pressure of 0.18 MPa, and then passed through a 1000 Da ultrafiltration membrane at a transmembrane pressure difference of 0.28 MPa, with the temperature of the feed liquid controlled at 12°C.

[0040] Step (9): The filtrate was passed through a 254 nm ultraviolet sterilization system at a transmission speed of 18 cm / s, with an irradiation intensity of 42 mW / cm² and an irradiation time of 20 s.

[0041] Step (10): The sterilized solution was aseptically filled into aluminum foil composite film packaging bags (oxygen transmission rate 0.4 cm³ / (m²·24 h·0.1 MPa)) in a sterile environment with a humidity of 12% RH, sealed by heat sealing after filling with 99.999% high-purity nitrogen, and stored in the dark.

[0042] Example 2:

[0043] Step (1): 100 kg of corn starch was mixed with 700 kg of 0.9% hydrochloric acid solution, and placed in a hydrolysis reactor, heated to 52°C, and hydrolyzed at constant temperature for 2.1 h. After the reaction was completed, 220 L of anhydrous ethanol was added to terminate the reaction, and the supernatant was collected by centrifugation at 8500 r / min for 18 min as the hydrolysis solution.

[0044] Step (2): The hydrolysis solution was inoculated into a 50 m³ fermenter with AS3.758 Aspergillus niger at a volume ratio of 1:0.035, the temperature was controlled at 30±0.3 ℃, sterile air was introduced to maintain the dissolved oxygen content at 26%, and the fermentation was carried out for 63 h. Then, 10% sodium hydroxide solution was used to adjust the pH to 7.1.

[0045] Step (3): 1.4% citric acid was added to the fermentation broth to adjust the pH to 2.25, and the temperature was raised to 78 ℃ for 50 min. The mycelium was removed by centrifugation at 9500 r / min for 18 min to obtain a crude vitamin C solution.

[0046] Step (4): The crude solution was passed through a sulfonic acid type cation exchange resin column (column height to diameter ratio 7.5:1) at a flow rate of 1.7 BV / h, and sequentially washed with 3.2 BV of deionized water, 2.1 BV of 0.1 mol / L NaOH solution, and 2.1 BV of 0.05 mol / L HCl solution. Finally, gradient elution was performed using 7.0% ammonium sulfate solution, and the eluate with a conductivity of 16-21 mS / cm was collected.

[0047] Step (5): The eluate was concentrated under reduced pressure at 43 ℃ to a solid content of 58%, 0.045% of seed crystals were added, and the temperature was lowered to 5±0.3 ℃ at a rate of 0.9 ℃ / min. The crystals were separated by centrifugation after crystallization for 11 h.

[0048] Step (6): The crystals were placed in a vacuum drying oven, and the vacuum degree was controlled at -0.085 MPa. The drying was carried out in three stages: preheating at 28 ℃ for 0.5 h in the first stage, drying at 49 ℃ for 2.7 h in the second stage, and constant temperature drying at 35 ℃ for 7.3 h in the third stage.

[0049] Step (7): The dried product was graded through a 280 mesh vibrating screen, and particles with a particle size of 85-145 μm were collected.

[0050] Step (8): The particles were dispersed in ultrapure water to form a 13% suspension, and then passed through a 0.45 μm microfiltration membrane at an operating pressure of 0.17 MPa, and then passed through a 1000 Da ultrafiltration membrane at a transmembrane pressure difference of 0.29 MPa. The temperature of the feed liquid was controlled at 13 ℃.

[0051] Step (9): The filtrate was transmitted through a 254 nm ultraviolet sterilization system at a transmission speed of 17 cm / s, the irradiation intensity was 45 mW / cm², and the irradiation time was 18 s.

[0052] Step (10): The sterilized solution was divided into aluminum foil composite film packaging bags (oxygen transmission rate 0.35 cm³ / (m²·24h·0.1 MPa)) in a sterile environment with a humidity of 10% RH, and then sealed by heat sealing after filling with 99.999% high-purity nitrogen. It was stored in the dark.

[0053] Example 3:

[0054] Step (1): 100 kg of corn starch was mixed with 650 kg of hydrochloric acid solution with a mass concentration of 0.85%, and placed in a hydrolysis reactor, and the temperature was raised to 51°C for constant temperature hydrolysis reaction for 2.05 h. After the reaction was completed, 210 L of anhydrous ethanol was added to terminate the reaction, and centrifugation was performed at a speed of 8200 r / min for 16 min, and the supernatant was collected as the hydrolysis liquid.

[0055] Step (2): The hydrolysis liquid and AS3.758 Aspergillus niger strain were inoculated into a 50 m³ fermenter at a volume ratio of 1:0.042, the temperature was controlled at 30±0.4°C, sterile air was introduced to maintain the dissolved oxygen content at 25.5%, and after 62.5 h of fermentation, 10% sodium hydroxide solution was used to adjust the pH to 7.05.

[0056] Step (3): 1.35% of citric acid was added to the fermentation liquid to adjust the pH to 2.22, and the temperature was raised to 76°C for 48 min, and the mycelium was removed by centrifugation at a speed of 9200 r / min for 19 min to obtain a crude vitamin C solution.

[0057] Step (4): The crude product solution was passed through a sulfonic acid type cation exchange resin column (column height diameter ratio 7.2:1) at a flow rate of 1.75 BV / h, and sequentially washed with 3.1 BV of deionized water, 2.05 BV of 0.1 mol / L NaOH solution, and 2.05 BV of 0.05 mol / L HCl solution, and finally gradient eluted with 6.9% ammonium sulfate solution, and the eluate with a conductivity of 15.5-20.5 mS / cm was collected.

[0058] Step (5): The eluate was concentrated under reduced pressure at 42.5°C to a solid content of 56%, 0.042% of seed crystals were added, and the temperature was lowered to 5±0.4°C at a rate of 0.85°C / min, and the crystals were separated by centrifugation after crystallization for 10.5 h.

[0059] Step (6): The crystals were placed in a vacuum drying oven, and the vacuum degree was controlled at -0.088 MPa, and dried in three stages: the first stage was preheated at 26°C for 0.5 h, the second stage was dried at 48.5°C for 2.75 h, and the third stage was dried at 35°C for 7.25 h.

[0060] Step (7): The dried product was graded through a 260 mesh vibrating screen, and particles with a particle size of 88-142 μm were collected.

[0061] Step (8): The particles were dispersed in ultrapure water to form a 12.5% suspension, and passed through a 0.45 μm microfiltration membrane under an operating pressure of 0.175 MPa, and then passed through a 1000 Da ultrafiltration membrane under a transmembrane pressure difference of 0.285 MPa, and the temperature of the feed liquid was controlled at 12.5°C.

[0062] Step (9): The filtrate was sterilized by 254 nm UV light with a transmission speed of 17.5 cm / s, an irradiation intensity of 43 mW / cm2, and an irradiation time of 19 s.

[0063] Step (10): The sterilized solution was aseptically filled into an aluminum foil composite film packaging bag (oxygen transmission rate 0.38 cm3 / (m2·24 h·0.1 MPa) in an aseptic environment with a humidity of 11% RH, and was sealed by heat sealing after being filled with 99.999% high-purity nitrogen, and was stored in the dark.

[0064] Example 4:

[0065] Step (1): 100 kg of corn starch was mixed with 680 kg of a hydrochloric acid solution with a mass concentration of 0.95%, and was placed in a hydrolysis reactor, and was heated to 53°C for constant temperature hydrolysis reaction for 2.15 h. After the reaction was completed, 230 L of anhydrous ethanol was added to terminate the reaction, and was centrifuged at a speed of 8800 r / min for 17 min, and the supernatant was collected as a hydrolysate.

[0066] Step (2): The hydrolysate was inoculated into a 50 m3fermenter with AS3.758 Aspergillus niger at a volume ratio of 1:0.038, the temperature was controlled at 31±0.4°C, sterile air was introduced to maintain the dissolved oxygen content at 27%, and after 64 h of fermentation, 10% sodium hydroxide solution was used to adjust the pH to 7.15.

[0067] Step (3): 1.45% of citric acid was added to the fermentation broth to adjust the pH to 2.28, and the temperature was raised to 77°C for 55 min, and the mycelium was removed by centrifugation at a speed of 9800 r / min for 17 min to obtain a crude vitamin C solution.

[0068] Step (4): The crude product solution was passed through a sulfonic acid type cation exchange resin column (column height diameter ratio 7.8:1) at a flow rate of 1.85 BV / h, and was sequentially washed with 3.3 BV of deionized water, 2.15 BV of 0.1 mol / L NaOH solution, and 2.15 BV of 0.05 mol / L HCl solution, and finally gradient elution was performed using 7.1% ammonium sulfate solution, and the eluate with a conductivity of 17-22 mS / cm was collected.

[0069] Step (5): The eluate was concentrated to a solid content of 59% at 44°C under reduced pressure, 0.048% of seed crystals were added, and the temperature was lowered to 5±0.2°C at a rate of 0.95°C / min, and the crystals were separated by centrifugation after crystallization for 11.5 h.

[0070] Step (6): The crystals were placed in a vacuum drying oven, and the vacuum degree was controlled at -0.092 MPa, and drying was carried out in three stages: preheating at 29°C for 0.5 h in the first stage, drying at 49.5°C for 2.65 h in the second stage, and constant temperature drying at 35°C for 7.35 h in the third stage.

[0071] Step (7): The dried product was classified by a 290 mesh vibrating screen, and the particles with a particle size of 82-147 μm were collected.

[0072] Step (8): The particles were dispersed in ultrapure water to form a 14% suspension, and the suspension was passed through a 0.45 μm microfiltration membrane at an operating pressure of 0.19 MPa and then through a 1000 Da ultrafiltration membrane at a transmembrane pressure difference of 0.295 MPa, with the temperature of the feed liquid controlled at 14°C.

[0073] Step (9): The filtrate was passed through a 254 nm ultraviolet sterilization system at a transmission speed of 19 cm / s, an irradiation intensity of 48 mW / cm2, and an irradiation time of 22 s.

[0074] Step (10): The sterilized solution was aseptically filled into aluminum foil composite film packaging bags (oxygen transmission rate 0.42 cm3 / (m2·24h·0.1 MPa) in an aseptic environment with a humidity of 13% RH, sealed by heat sealing after filling with 99.999% high-purity nitrogen, and stored in the dark.

[0075] Example 5:

[0076] Step (1): 100 kg of corn starch was mixed with 720 kg of a hydrochloric acid solution with a mass concentration of 1.0%, and the mixture was placed in a hydrolysis reactor, which was heated to 54°C and maintained at this temperature for 2.2 h of hydrolysis reaction. After the reaction was completed, 240 L of anhydrous ethanol was added to terminate the reaction, and the supernatant was collected by centrifugation at a speed of 9000 r / min for 16 min as the hydrolyzate.

[0077] Step (2): The hydrolyzate was inoculated into a 50 m3 fermenter with AS3.758 Aspergillus niger at a volume ratio of 1:0.048, the temperature was controlled at 31±0.5°C, sterile air was introduced to maintain the dissolved oxygen content at 28%, and the fermentation was carried out for 65 h. Then, 10% sodium hydroxide solution was used to adjust the pH to 7.2.

[0078] Step (3): 1.5% citric acid was added to the fermentation broth to adjust the pH to 2.3, and the temperature was raised to 80°C for 60 min. The broth was centrifuged at a speed of 10000 r / min for 15 min to remove the mycelium, and a crude vitamin C solution was obtained.

[0079] Step (4): The crude product solution was passed through a sulfonic acid type cation exchange resin column (column height to diameter ratio 8:1) at a flow rate of 2.0 BV / h, and then sequentially washed with 3.5 BV of deionized water, 2.2 BV of 0.1 mol / L NaOH solution, and 2.2 BV of 0.05 mol / L HCl solution. Finally, gradient elution was performed using 7.2% ammonium sulfate solution, and the eluate with a conductivity of 18-23 mS / cm was collected.

[0080] Step (5): The eluent was concentrated under reduced pressure at 45°C to a solid content of 60%, 0.05% by mass of seed crystals were added, and the temperature was decreased to 5±0.5°C at a rate of 1.0°C / min. After crystallization for 12 h, the crystals were separated by centrifugation.

[0081] Step (6): The crystals were placed in a vacuum drying oven, and dried in three stages: preheating at 30°C for 0.5 h, drying at 50°C for 3 h, and constant temperature drying at 35°C for 7.5 h, with a vacuum degree of -0.1 MPa.

[0082] Step (7): The dried product was classified by a 300-mesh vibrating screen, and particles with a particle size of 80-150 μm were collected.

[0083] Step (8): The particles were dispersed in ultrapure water to form a 15% suspension, which was passed through a 0.45-μm microfiltration membrane at an operating pressure of 0.2 MPa, and then passed through a 1000-Da ultrafiltration membrane at a transmembrane pressure difference of 0.3 MPa, with a feed liquid temperature of 15°C.

[0084] Step (9): The filtrate was passed through a 254-nm ultraviolet sterilization system at a transmission speed of 20 cm / s, an irradiation intensity of 50 mW / cm², and an irradiation time of 25 s.

[0085] Step (10): The sterilized solution was aseptically filled into aluminum foil composite film packaging bags (oxygen transmission rate 0.5 cm³ / (m²·24 h·0.1 MPa)) in a sterile environment with a humidity of 15% RH, sealed by heat sealing after filling with 99.999% high-purity nitrogen, and stored in the dark.

[0086] Comparative Example 1:

[0087] Step (1): 100 kg of corn starch was mixed with 500 kg of a hydrochloric acid solution having a mass concentration of 0.5%, and placed in a hydrolysis reaction kettle. The temperature was increased to 45°C, and the hydrolysis reaction was maintained at this temperature for 1.5 h. After the reaction was completed, 150 L of anhydrous ethanol was added to terminate the reaction. The supernatant was collected by centrifugation at a speed of 6000 r / min for 10 min, and used as the hydrolyzate.

[0088] Step (2): The hydrolyzate and ordinary Aspergillus niger spores were inoculated into a 50-m³ fermenter at a volume ratio of 1:0.03. The temperature was controlled at 28°C, sterile air was introduced to maintain a dissolved oxygen content of 20%, and the fermentation was carried out for 48 h. Then, 10% sodium hydroxide solution was used to adjust the pH to 6.8.

[0089] Step (3): 1.0% by volume of citric acid was added to the fermentation liquor to adjust the pH to 2.0. The temperature was increased to 70°C, and the mixture was maintained at this temperature for 30 min. The mycelium was removed by centrifugation at a speed of 7000 r / min for 10 min, and a crude vitamin C solution was obtained.

[0090] Step (4): The crude product solution was passed through a general cation exchange resin column (column height-diameter ratio 5:1) at a flow rate of 1.0 BV / h, and was sequentially washed with 2 BV of deionized water, 1 BV of 0.1 mol / L NaOH solution and 1 BV of 0.05 mol / L HCl solution, and finally gradient eluted with 5% ammonium sulfate solution. The eluate with a conductivity of 10-15 mS / cm was collected.

[0091] Step (5): The eluate was concentrated under reduced pressure at 40°C to a solid content of 50%, 0.02% by mass of crystal seeds were added, and the temperature was decreased to 4°C at a rate of 0.5°C / min. After crystallization for 8 h, the crystals were centrifuged and separated.

[0092] Step (6): The crystals were placed in a vacuum drying oven, the vacuum degree was controlled at -0.08 MPa, and the temperature was directly increased to 50°C for drying for 4 h.

[0093] Step (7): The dried product was graded through a 200-mesh vibrating screen, and particles with a particle size of 70-180 μm were collected.

[0094] Step (8): The particles were dispersed in ultrapure water to form a 10% suspension, passed through a 0.45-μm microfiltration membrane at an operating pressure of 0.1 MPa, and then passed through a 1000-Da ultrafiltration membrane at a transmembrane pressure difference of 0.2 MPa, with the temperature of the feed liquid controlled at 5°C.

[0095] Step (9): The filtrate was passed through a 254-nm ultraviolet sterilization system at a transmission speed of 10 cm / s, the irradiation intensity was 30 mW / cm², and the irradiation time was 10 s.

[0096] Step (10): The sterilized solution was aseptically filled into general aluminum foil packaging bags (oxygen transmission rate 1.0 cm³ / (m²·24 h·0.1 MPa)) in a sterile environment with a humidity of 20% RH, filled with 99.9% nitrogen, heat-sealed, and stored in the dark.

[0097] Comparative Example 2:

[0098] Step (1): 100 kg of corn starch was mixed with 800 kg of a hydrochloric acid solution with a mass concentration of 1.2%, and placed in a hydrolysis reactor, which was heated to 55°C and maintained at this temperature for hydrolysis reaction for 2.5 h. After the reaction was completed, 300 L of anhydrous ethanol was added to terminate the reaction, and the supernatant was collected by centrifugation at a speed of 10,000 r / min for 20 min as the hydrolyzate.

[0099] Step (2): The hydrolyzate and AS3.758 Aspergillus niger spores were inoculated into a 50-m³ fermenter at a volume ratio of 1:0.05, the temperature was controlled at 32°C, sterile air was introduced to maintain the dissolved oxygen content at 30%, and after fermentation for 72 h, 10% sodium hydroxide solution was used to adjust the pH to 7.2.

[0100] Step (3): 2.0% (volume ratio) citric acid was added to the fermentation broth, the pH was adjusted to 2.5, and the temperature was raised to 80°C for 60 min. The mycelium was removed by centrifugation at 12000 r / min for 25 min to obtain a crude vitamin C solution.

[0101] Step (4): The crude solution was passed through a sulfonic acid type cation exchange resin column (column height to diameter ratio 10:1) at a flow rate of 3.0 BV / h. The column was sequentially washed with 5 BV of deionized water, 3 BV of 0.1 mol / L NaOH solution, and 3 BV of 0.05 mol / L HCl solution. Finally, gradient elution was performed using 10% ammonium sulfate solution, and the eluate with a conductivity of 25-30 mS / cm was collected.

[0102] Step (5): The eluate was concentrated under reduced pressure at 50°C to a solid content of 70%. 0.1% (mass) of seed crystals were added, and the temperature was lowered to 6°C at a rate of 2.0°C / min. After crystallization for 15 h, the crystals were separated by centrifugation.

[0103] Step (6): The crystals were placed in a vacuum drying oven, the vacuum degree was controlled at -0.12 MPa, and the temperature was directly raised to 60°C for drying for 2 h.

[0104] Step (7): The dried product was classified by a 350-mesh vibrating screen, and particles with a particle size of 50-200 μm were collected.

[0105] Step (8): The particles were dispersed in ultrapure water to form a 20% suspension, which was passed through a 0.45 μm microfiltration membrane under an operating pressure of 0.3 MPa, and then passed through a 1000 Da ultrafiltration membrane under a transmembrane pressure difference of 0.5 MPa. The temperature of the feed liquid was controlled at 25°C.

[0106] Step (9): The filtrate was passed through a 254 nm ultraviolet sterilization system at a transmission speed of 30 cm / s, the irradiation intensity was 60 mW / cm², and the irradiation time was 40 s.

[0107] Step (10): The sterilized solution was divided into sterile aluminum foil packaging bags (oxygen transmission rate 0.2 cm³ / (m²·24h·0.1 MPa)) in a sterile environment with a humidity of 5% RH, filled with 99.99% nitrogen, and heat sealed. It was stored in the dark.

[0108] Comparative Example 3:

[0109] Step (1): 100 kg of corn starch was mixed with 600 kg of 0.8% hydrochloric acid solution, and placed in a hydrolysis reactor. The temperature was raised to 50°C for hydrolysis reaction for 2 h. After the reaction was completed, 200 L of anhydrous ethanol was added to terminate the reaction. The supernatant was collected by centrifugation at 8000 r / min for 15 min, and used as the hydrolysis solution.

[0110] Step (2): The hydrolysis solution was inoculated into a 50 m³ fermenter with AS3.758 Aspergillus niger at a volume ratio of 1:0.04, the temperature was controlled at 30±0.5 ℃, sterile air was introduced to maintain the dissolved oxygen content at 25%, and after 62 h of fermentation, 10% sodium hydroxide solution was used to adjust the pH to 7.0.

[0111] Step (3): 1.3% citric acid was added to the fermentation broth to adjust the pH to 2.2, and the temperature was raised to 75 ℃ for 45 min, then centrifuged at 9000 r / min for 20 min to remove the mycelium, and a crude vitamin C solution was obtained.

[0112] Step (4): The crude solution was directly concentrated under reduced pressure to a solid content of 55%, 0.04% of crystal seeds were added, and the temperature was lowered to 5±0.5 ℃ at a rate of 0.8 ℃ / min, and the crystals were separated by centrifugation after crystallization for 10 h.

[0113] Step (5): The crystals were placed in a vacuum drying oven, the vacuum degree was controlled at-0.09 MPa, and the drying was carried out in three stages: the first stage was preheated at 25 ℃ for 0.5 h, the second stage was dried at 48 ℃ for 2.8 h, and the third stage was dried at 35 ℃ for 7.2 h.

[0114] Step (6): The dried product was graded by a 250 mesh vibrating screen, and particles with a particle size of 90-140 μm were collected.

[0115] Step (7): The particles were dispersed in ultrapure water to form a 12% suspension, and the suspension was filtered through a 0.45 μm microfiltration membrane at an operating pressure of 0.18 MPa, and then filtered through a 1000 Da ultrafiltration membrane at a transmembrane pressure difference of 0.28 MPa, and the temperature of the feed liquid was controlled at 12 ℃.

[0116] Step (8): The filtrate was transmitted through a 254 nm ultraviolet sterilization system at a transmission speed of 18 cm / s, the irradiation intensity was 42 mW / cm², and the irradiation time was 20 s.

[0117] Step (9): The sterilized solution was divided into aluminum foil composite film packaging bags (oxygen transmission rate 0.4 cm³ / (m²·24h·0.1 MPa)) in a sterile environment with a humidity of 12% RH, filled with 99.999% high-purity nitrogen, and heat-sealed for light-proof storage.

[0118] Performance test and data analysis:

[0119] The key performance indicators of the vitamin C products prepared in Examples 1-5 and Comparative Examples 1-3 were tested, and the results are shown in Tables 1 and 2.

[0120] Table 1 Comparison of quality indicators of vitamin C products

[0121]

[0122] Table 2 Comparison of production process parameters

[0123]

[0124] 1. As can be seen from Table 1, the vitamin C products prepared in Examples 1-5 are significantly superior to the products of Comparative Examples in key indicators such as purity, solvent residue, heavy metal content and microbial contamination. In particular, the solvent residue is controlled below 2 ppm in Examples, while Comparative Examples 1-3 reach 15 ppm, 8 ppm and 25 ppm respectively. This is mainly due to the optimized resin purification process and the segmented drying technology in Examples.

[0125] 2. The data in Table 2 shows that the overall yield of Examples 1-5 is between 75.3%-78.4%, significantly higher than 55.1%-65.8% of Comparative Examples 1-3. Among them, although Comparative Example 3 adopts similar hydrolysis and fermentation processes as Examples, it omits the ion exchange resin purification step, resulting in a decrease of about 10 percentage points in overall yield and a significant increase in solvent residue, proving that the resin purification step has a key impact on product quality and yield.

[0126] 3. By comparing Example 5 and Comparative Example 2, it can be found that although both of them adopt more extreme process parameters, Example 5 achieves a better balance between product quality and yield by precisely controlling the parameter range of each step (such as hydrolysis temperature 54℃ vs 55℃, ammonium sulfate concentration 7.2% vs 10%, etc.), which shows that the optimized combination of process parameters is more important than the extreme value of a single parameter.

[0127] 4. The stability test results show that the content retention rate of Example products is higher than 99.5% for 12 months, while the content retention rate of Comparative Example products is generally lower than 98%. This is mainly due to the comprehensive protection measures such as ultraviolet sterilization and nitrogen packaging used in Examples, which effectively delay the oxidative degradation of vitamin C.

[0128] In summary, the low-solvent-residue vitamin C preparation method provided in this patent realizes the simultaneous improvement of product quality and yield through the synergistic optimization of process parameters at each step, especially the innovative combination of key technologies such as hydrolysis condition control, strain selection, resin purification and segmented drying, and the solvent residue is significantly lower than that of conventional preparation methods.

[0129] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application, and that such changes, modifications, substitutions and alterations are intended to fall within the scope of the application.

Claims

1. A method for preparing vitamin C with low solvent residue, characterized in that: Includes the following steps: Step (1) Mix corn starch with hydrochloric acid solution with a mass concentration of 0.5-1.2% at a mass ratio of 1:5-8, and hydrolyze at 45-55℃ for 1.5-2.5h. After the reaction is completed, add anhydrous ethanol to terminate the reaction and centrifuge to obtain the hydrolysate. Step (2) Introduce the hydrolysate and Aspergillus niger strain into the fermenter at a volume ratio of 1:0.03-0.05, control the temperature at 28-32℃, introduce sterile air to maintain dissolved oxygen at 20-30%, and adjust the pH to 6.8-7.2 after fermentation for 48-72 hours; the Aspergillus niger strain is AS3.

758. Step (3) Add citric acid to the fermentation broth to adjust the pH to 2.0-2.5, heat to 70-80℃ and keep warm for 0.5-1h, centrifuge to remove mycelium and obtain crude vitamin C solution; Step (4) The crude product solution is passed through a cation exchange resin column and washed sequentially with deionized water, 0.1 mol / L NaOH solution and 0.05 mol / L HCl solution, followed by gradient elution with 5-8% ammonium sulfate solution; the cation exchange resin is a sulfonic acid type resin with a column height-to-diameter ratio of 6:1-8:1 and an elution flow rate of 1.5-2.0 BV / h; Step (5) Collect the eluent and concentrate it under reduced pressure at 40-45℃ to a solid content of 50-60%. Add seed crystals and cool it to 4-6℃ at a rate of 0.5-1℃ / min. After crystallization for 8-12 hours, centrifuge to separate the crystals. Step (6) Place the crystal in a vacuum drying oven, control the vacuum degree to -0.08~-0.1MPa, heat it up to 50℃ in stages for 3-4 hours, and then cool it down to 35℃ for 6-8 hours. The vacuum drying is divided into three stages: the first stage is preheating at 20-30℃ for 0.5 hours, the second stage is drying at 45-50℃ for 2.5-3 hours, and the third stage is constant temperature drying at 35℃ for 7-7.5 hours. Step (7) The dried product is classified by a 200-300 mesh vibrating sieve, and particles with a diameter of 80-150 μm are collected; Step (8) Disperse the particles in ultrapure water to form a 10-15% suspension, and then pass it through a 0.45μm microfiltration membrane and a 1000Da ultrafiltration membrane in sequence; Step (9) The filtrate is sterilized by ultraviolet irradiation with an intensity of 30-50 mW / cm². 2 Irradiation time: 15-30 seconds; Step (10) Dispense the sterilized solution into aluminum foil composite film packaging bags in a sterile environment, seal them with nitrogen, and store them away from light.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of hydrochloric acid solution is 0.8-1.0%, the mass ratio of corn starch to hydrochloric acid solution is 1:6-7, the hydrolysis temperature is 50±2℃, and the reaction time is 2-2.2h.

3. The preparation method according to claim 1, characterized in that: In step (5), the amount of seed crystals added is 0.03-0.05% of the mass of the concentrate, the cooling rate is 0.8-1.0℃ / min, and the crystallization endpoint temperature is 5±0.5℃.

4. The preparation method according to claim 1, characterized in that: In step (8), the microfiltration membrane operating pressure is 0.15-0.2 MPa, the ultrafiltration membrane transmembrane pressure difference is 0.25-0.3 MPa, and the feed temperature is maintained at 10-15℃.

5. The preparation method according to claim 1, characterized in that: In step (9), the ultraviolet wavelength is 254 nm and the irradiation intensity is 40 ± 5 mW / cm². 2 The suspension transport speed is 15-20 cm / s.

6. The preparation method according to claim 1, characterized in that: In step (10), the nitrogen purity is ≥99.999%, and the oxygen permeability of the packaging bag is ≤0.5cm. 3 / (m 2 • 24h • 0.1MPa), and the humidity of the packaging environment is ≤15%RH.

7. The preparation method according to claim 1, characterized in that: In step (3), the amount of citric acid added is 1.2-1.5% of the fermentation liquid volume, the pH value at the acidification endpoint is 2.2-2.3, and the centrifuge speed is 8000-10000 r / min.

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