Osmanthus fragrans color protection and tannin degradation technology, osmanthus fragrans jelly and preparation method of osmanthus fragrans jelly

Abstract

The invention discloses a sweet osmanthus color protection and tannin degradation process, sweet osmanthus jelly and a preparation method thereof, and relates to the technical field of food processing. The sweet osmanthus color-protecting and tannin-degrading process comprises the following steps: soaking in a color-protecting solution under a low-temperature condition; performing pulsed electric field treatment on the sweet-scented osmanthus treated by the color protection liquid; carrying out segmented pressure reduction on the sweet-scented osmanthus subjected to pulsed electric field treatment under a low-temperature condition; the preparation method comprises the following steps: loading tannase and laccase by adopting magnetic Fe3O4 and chitosan microspheres, so as to obtain an immobilized enzyme; carrying out mixed enzymolysis on the sweet-scented osmanthus subjected to pressure reduction treatment and immobilized enzyme, and meanwhile, carrying out double-frequency alternate ultrasonic-assisted enzymolysis; and dehydrating. The sweet-scented osmanthus treated by the method can keep a natural form, is stable in color and luster, is not easy to brown and has no bitter taste of tannin when being tasted, and the sweet-scented osmanthus jelly prepared from the sweet-scented osmanthus jelly can keep the elegant and natural fragrance of the sweet-scented osmanthus.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a process for protecting the color of osmanthus and degrading tannin, osmanthus jelly and a preparation method thereof. Background Art

[0002] Osmanthus is spicy and warm in taste, has the effects of dispelling cold, breaking up stagnation, resolving phlegm and relieving cough, and has a fragrant smell. It can be used in food, cosmetics, winemaking, and pharmaceutical industries.

[0003] However, since osmanthus is rich in polyphenols, these components are prone to enzymatic browning reactions after contact with oxygen. When petal cells are damaged or come into contact with water, the cell structure is destroyed, phenolic substances come into contact with polyphenol oxidase, and quinone brown polymers are generated with the participation of oxygen, causing the color to gradually change from golden to dark brown or black. Secondly, high temperature (such as sunlight) conditions will increase enzyme activity and accelerate the reaction rate; water retention can easily lead to the destruction of osmanthus cell structure and promote the contact reaction between phenolic substances and polyphenol oxidase. In addition, the bitter taste of osmanthus mainly comes from the tannins (tannic acid) it contains, which are polyphenol compounds. Fresh osmanthus has a high content of tannins, which will produce a noticeable bitter feeling when it comes into direct contact with the mouth. Tannins can combine with proteins in saliva and precipitate, reducing oral lubricity and causing astringent astringency.

[0004] In the prior art, the conventional methods for protecting the color of osmanthus are: ① vacuum or low-temperature drying can reduce oxygen contact, inhibit enzyme activity and non-enzymatic oxidation; ② quicklime drying method reduces moisture by hygroscopicity and delays browning. However, the above methods can only temporarily inhibit or delay, and cannot really solve the problem. Tannin degradation is usually carried out by acid-base treatment (degradation rate ≤ 65%, cell damage rate > 20%), which has a high cell damage rate and a low tannin degradation rate.

[0005] Therefore, there is an urgent need for an efficient enzyme inactivation, color protection and tannin degradation process for osmanthus, which can extend the shelf life of the product while maintaining the original shape and natural color of osmanthus. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a process for protecting the color of osmanthus and degrading tannin, osmanthus jelly and a preparation method thereof, by inactivating polyphenol oxidase (PPO) by targeted pulsed electric field and combining magnetic dual enzymes to synergistically degrade tannins, thereby solving the problems of browning and bitterness of osmanthus.

[0007] The present invention provides the following technical solutions:

[0008] The present invention provides a process for protecting the color of osmanthus and degrading tannin, which comprises the following steps:

[0009] S1. Soaking in color protection liquid: Soak the selected fresh osmanthus in the color protection liquid for 8-12 minutes at a pH of 4.0-4.4 and a temperature of 4-8°C;

[0010] S2, pulse electric field treatment: subjecting the sweet osmanthus treated with the color protection liquid to pulse electric field treatment;

[0011] S3, low temperature gradient decompression: the osmanthus treated with pulse electric field is subjected to stepwise decompression at 4-8°C;

[0012] S4, immobilized enzyme preparation; using magnetic Fe 3 O 4 @Chitosan microspheres loaded with tannase and laccase to obtain immobilized enzymes;

[0013] S5, ultrasound-assisted enzymatic hydrolysis; mixing the depressurized osmanthus and the immobilized enzyme at a solid-liquid ratio of 1:(13-17) (w / v), and subjecting to dual-frequency alternating ultrasound treatment for 15-25 minutes;

[0014] S6, enzymolysis; stirring the osmanthus flowers after ultrasound-assisted enzymolysis at a temperature of 38-42° C. and a pH of 5.0-5.5 for 80-100 minutes;

[0015] S7, vacuum dehydration: dehydrate the osmanthus flowers under vacuum conditions at a temperature of 45-50° C. until the moisture content is less than 15%.

[0016] Furthermore, the color protection solution comprises ascorbic acid, citric acid and CaCl in a mass ratio of (0.25-0.35): (0.08-0.12): (0.04-0.06). 2 .

[0017] Furthermore, the parameters of the pulse electric field treatment are: field intensity 32-38 kV / cm, pulse width 38-42 μs, frequency 700-900 Hz, and pulse number 15-25 times.

[0018] Preferably, the cleaned fresh osmanthus is obtained by placing the fresh osmanthus in a mesh sieve with a vibration frequency of 15-20 Hz for mechanical impurity removal for 5-8 minutes, and manually removing the remaining pedicels and foreign matter with a diameter of less than 2 mm.

[0019] Preferably, the temperature of the medium treated by the pulse electric field is ≤8°C, so as to maintain the integrity of the osmanthus cell wall.

[0020] Preferably, the pulse electric field treatment adopts an intermittent mode treatment of working for 3±1s and resting for 2±1s.

[0021] Furthermore, the stepwise pressure reduction includes three stages of pressure reduction, wherein the first stage is vacuuming to -0.08 MPa and maintaining it for 5 minutes, the second stage is maintaining it at -0.05 MPa for 5 minutes, and the third stage is restoring normal pressure.

[0022] Furthermore, the preparation method of the immobilized enzyme is as follows: the magnetic Fe 3 O 4 Chitosan microspheres and a mixed enzyme solution including tannase and laccase were mixed, pre-adsorbed at 2-6°C for 0.8-1.2h, and then glutaraldehyde was slowly added dropwise to a final concentration of 0.7-0.9%. The mixture was cross-linked at 2-6°C and 100-150rpm for 2-3h under constant temperature oscillation to obtain an immobilized enzyme.

[0023] Furthermore, the magnetic Fe 3 O 4 @The particle size of chitosan microspheres is 50-100 μm, the tannase content is 1500-2500 U / g, and the laccase content is 1200-1800 U / g.

[0024] Preferably, the tannase content is 1800-2200 U / g, and the laccase content is 1500-1700 U / g.

[0025] Preferably, the fluctuation frequency of the dual-frequency alternating ultrasonic treatment is 35-45kHz.

[0026] Furthermore, the stirring speed in step S6 is 120-180 rpm.

[0027] Preferably, the vacuum degree of the vacuum dehydration is -0.095 MPa.

[0028] The present invention also provides an osmanthus jelly, which comprises osmanthus treated by the osmanthus color protection and tannin degradation processes.

[0029] The present invention also discloses a preparation process of the above-mentioned osmanthus jelly, which comprises the following steps:

[0030] (1) dissolving vitamin C in hot water at 80-85° C. at a solid-liquid ratio of (0.015-0.025):100, filtering to obtain an osmanthus extract, and pre-soaking the osmanthus treated by the above osmanthus color protection and tannin degradation process in water for later use;

[0031] (2) A thickener is mixed and dispersed with syrup having a mass concentration of 58-60% in a mass ratio of 1:(60-120) and then dissolved in water. After the thickener swells for 10-30 minutes, it is heated to 95±1° C., the heating is stopped, and when the temperature is cooled to 70-80° C., the following components are added in parts by mass: 0.1-0.5 parts of soaked osmanthus, 1-5 parts of osmanthus extract, 5-50 parts of fruit juice and / or 10-25 parts of pulp, 0.01-0.1 parts of natural flavor, 0.01-0.03 parts of natural lutein, 0.08-0.20 parts of citric acid, 0.06-0.18 parts of sodium citrate, and 0.02-0.18 parts of vitamin C are mixed and stirred evenly, sterilized, and cooled to obtain osmanthus jelly.

[0032] Furthermore, the thickener comprises the following components in parts by weight: 0.08-0.3 parts of carrageenan, 0.08-0.2 parts of konjac flour, 0.05-0.15 parts of agar, 0.05-0.2 parts of locust bean gum, 0.1-0.3 parts of potassium chloride and 0.1-0.5 parts of calcium lactate.

[0033] Furthermore, the sterilization is pasteurization, and the sterilization parameters are temperature 85-92°C and time 10-20 minutes.

[0034] The present invention has the following technical effects:

[0035] The invention uses a color protection liquid to chelate metal ions, inhibit PPO active precursors, and reduce cell membrane permeability; uses a pulse electric field to induce PPO protein conformational changes, destroy active centers, and selectively denature enzyme molecules to keep cell walls intact; uses low-temperature gradient pressure reduction to avoid cell rupture caused by sudden pressure changes, and maintains the microstructure of petals; cross-links the amino groups of chitosan with enzyme molecules, and simultaneously achieves rapid separation due to magnetic responsiveness, thereby improving the retention rate of immobilized enzymes; uses magnetic double enzymes to synergistically degrade osmanthus tannins, tannin enzymes hydrolyze ester bonds to generate gallic acid, and laccases oxidize phenolic hydroxyls to generate quinones, thereby synergistically degrading tannin macromolecules; uses ultrasound-assisted enzymolysis to achieve cavitation effects to enhance enzyme-substrate contact efficiency, and uses an intermittent mode to prevent local overheating; and uses vacuum low-temperature dehydration to fix the osmanthus in a fixed form, thereby preventing the activity of PPO from reviving during the rehydration process. The osmanthus treated by the invention has stable color, maintains stable color within a shelf life of 9 months, does not undergo browning, and has no tannin bitterness when tasted. The osmanthus jelly prepared by the invention can retain the elegant and natural aroma of the osmanthus and has a good sweet and sour taste. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0037] Figure 1 This is a diagram showing the appearance of sweet osmanthus treated in Example 2 of the present invention after being stored at room temperature for 180 days.

[0038] Figure 2 This is the appearance of the jelly prepared in Example 2.

[0039] Figure 3 This is the appearance of the jelly prepared in Example 3.

[0040] Figure 4 This is the appearance of the jelly prepared in Example 1.

[0041] Figure 5 This is the appearance of the jelly prepared in Example 1 after being stored at room temperature for 9 months. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0044] In order to more fully understand the technical content of the present invention, the technical solution of the present invention is further introduced and illustrated in conjunction with specific embodiments below.

[0045] Example 1

[0046] A process for protecting the color of sweet osmanthus and degrading tannins, comprising the following steps:

[0047] S1. Raw material pretreatment

[0048] Fresh osmanthus flowers are placed in a machine vibrating mesh sieve for mechanical impurity removal, and residual peduncles and foreign objects with a diameter of less than 2 mm are manually removed to obtain clean osmanthus flowers.

[0049] S2, soak in color protection liquid

[0050] The cleaned osmanthus flowers were immersed in a color protection solution at pH 4.2 and 4°C for 10 minutes; wherein the color protection solution comprises ascorbic acid, citric acid and CaCl in a mass ratio of 0.3:0.1:0.05. 2 ;

[0051] S3. Pulsed electric field treatment

[0052] The osmanthus flowers treated with the color protection solution were subjected to pulse electric field treatment under the parameters of field strength 35 kV / cm, pulse width 40 μs, frequency 800 Hz, pulse number 20 times, and medium temperature 6°C.

[0053] S4, low temperature gradient decompression

[0054] The pulsed electric field treated osmanthus was depressurized in three stages: the first stage was pumped to -0.08MPa for 5 minutes, the second stage was -0.05MPa for 5 minutes, and the third stage was restored to normal pressure.

[0055] S5. Preparation of immobilized enzyme

[0056] Take magnetic Fe with a particle size of 80 μm 3 O 4 @ Chitosan microspheres and mixed enzyme solution including 2000U / g tannase and 1500U / g laccase were measured by magnetic Fe 3 O 4 @Chitosan microspheres: mixed enzyme solution = 1g:5mL ratio, pre-adsorbed at 4℃ for 1h, slowly add glutaraldehyde to a final mass concentration of 0.8%, and crosslink at 4℃ and 120rpm for 2h to obtain immobilized enzyme;

[0057] S6, Ultrasound-assisted enzymatic hydrolysis

[0058] The depressurized osmanthus was mixed with the immobilized dual enzyme complex at a ratio of 1:15 (w / v), and injected into a 40kHz dual-frequency alternating ultrasonic field with a power density of 120W / L, using a 3-second working / 2-second intermittent mode for a total of 20 minutes;

[0059] S7, dynamic enzymatic reaction

[0060] The system was adjusted to pH 5.2 and temperature 40°C, and the reaction was carried out at a constant temperature of 150 rpm for 90 minutes;

[0061] S8, vacuum low temperature dehydration

[0062] The product after the dynamic enzymatic hydrolysis reaction was dried under the conditions of vacuum degree -0.095MPa and 45°C until the moisture content was less than 15%;

[0063] S9. Finished product packaging

[0064] It is sealed in aluminum foil bags, filled with nitrogen, and stored at room temperature away from light.

[0065] Example 2

[0066] A process for protecting the color of sweet osmanthus and degrading tannins, comprising the following steps:

[0067] S1. Raw material pretreatment

[0068] Fresh osmanthus flowers are placed in a machine vibrating mesh sieve for mechanical impurity removal, and residual peduncles and foreign objects with a diameter of less than 2 mm are manually removed to obtain clean osmanthus flowers.

[0069] S2, soak in color protection liquid

[0070] The cleaned osmanthus flowers were immersed in a color protection solution at pH 4 and 8°C for 12 minutes; wherein the color protection solution included ascorbic acid, citric acid and CaCl in a mass ratio of 0.25:0.12:0.04. 2 ;

[0071] S3. Pulsed electric field treatment

[0072] The osmanthus flowers treated with the color protection solution were subjected to pulse electric field treatment under the parameters of field strength 38 kV / cm, pulse width 42 μs, frequency 700 Hz, pulse number 25 times, and medium temperature 8°C.

[0073] S4, low temperature gradient decompression

[0074] The pulsed electric field treated osmanthus was depressurized in three stages: the first stage was pumped to -0.08MPa for 5 minutes, the second stage was -0.05MPa for 5 minutes, and the third stage was restored to normal pressure.

[0075] S5. Preparation of immobilized enzyme

[0076] Take magnetic Fe with a particle size of 100 μm 3 O 4 @ Chitosan microspheres and mixed enzyme solution including 2500U / g tannase and 1800U / g laccase were measured by magnetic Fe 3 O 4 @Chitosan microspheres: mixed enzyme solution = 1g:4mL ratio, pre-adsorbed at 6℃ for 0.8h, slowly add glutaraldehyde to a final mass concentration of 0.7%, and crosslinked at 6℃ and 150rpm for 2.5h to obtain immobilized enzyme;

[0077] S6, Ultrasound-assisted enzymatic hydrolysis

[0078] The depressurized osmanthus was mixed with the immobilized dual enzyme complex at a ratio of 1:15 (w / v), and injected with a 35kHz dual-frequency alternating ultrasonic field with a power density of 100W / L, and ultrasonic treatment was performed in a 3s working / 2s intermittent mode for a total of 25 minutes;

[0079] S7, dynamic enzymatic reaction

[0080] The system was adjusted to pH 5.0 and temperature 42°C, and the reaction was carried out at a constant temperature of 120 rpm for 100 minutes;

[0081] S8, vacuum low temperature dehydration

[0082] The product after the dynamic enzymatic hydrolysis reaction was dried under the conditions of vacuum degree -0.095MPa and 50°C until the moisture content was less than 15%;

[0083] S9. Finished product packaging

[0084] It is sealed in aluminum foil bags, filled with nitrogen, and stored at room temperature away from light.

[0085] Example 3

[0086] A process for protecting the color of sweet osmanthus and degrading tannins, comprising the following steps:

[0087] S1. Raw material pretreatment

[0088] Fresh osmanthus flowers are placed in a machine vibrating mesh sieve for mechanical impurity removal, and residual peduncles and foreign objects with a diameter of less than 2 mm are manually removed to obtain clean osmanthus flowers.

[0089] S2, soak in color protection liquid

[0090] The cleaned osmanthus flowers were immersed in a color-protecting solution at pH 4.4 and 8°C for 8 minutes; wherein the color-protecting solution comprises ascorbic acid, citric acid and CaCl in a mass ratio of 0.35:0.08:0.06. 2 ;

[0091] S3. Pulsed electric field treatment

[0092] The osmanthus flowers treated with the color protection solution were subjected to pulse electric field treatment under the parameters of field strength 32 kV / cm, pulse width 38 μs, frequency 900 Hz, pulse number 15 times, and medium temperature 8°C.

[0093] S4, low temperature gradient decompression

[0094] The pulsed electric field treated osmanthus was depressurized in three stages: the first stage was pumped to -0.08MPa for 5 minutes, the second stage was -0.05MPa for 5 minutes, and the third stage was restored to normal pressure.

[0095] S5. Preparation of immobilized enzyme

[0096] Take magnetic Fe with a particle size of 50 μm 3 O 4 @ Chitosan microspheres and mixed enzyme solution including 1500U / g tannase and 1200U / g laccase were magnetically Fe 3 O 4@Chitosan microspheres: mixed enzyme solution = 1g: 6mL ratio, pre-adsorbed at 2℃ for 1.2h, slowly add glutaraldehyde to a final mass concentration of 0.9%, and crosslink at 2℃ and 100rpm for 3h to obtain immobilized enzyme;

[0097] S6, Ultrasound-assisted enzymatic hydrolysis

[0098] The depressurized osmanthus was mixed with the immobilized dual enzyme complex at a ratio of 1:15 (w / v), and injected into a 45kHz dual-frequency alternating ultrasonic field with a power density of 140W / L, using a 3-second working / 2-second intermittent mode for a total of 15 minutes;

[0099] S7, dynamic enzymatic reaction

[0100] Adjust the system to pH 5.5 and temperature 38°C, and oscillate at a constant temperature of 180 rpm for 80 minutes;

[0101] S8, vacuum low temperature dehydration

[0102] The product after the dynamic enzymatic hydrolysis reaction was dried under the conditions of vacuum degree -0.095MPa and 48°C until the moisture content was less than 15%;

[0103] S9. Finished product packaging

[0104] It is sealed in aluminum foil bags, filled with nitrogen, and stored at room temperature away from light.

[0105] To illustrate the technical effect of the present invention, the following tests were performed based on Examples 1-3:

[0106] (I) Test of treatment effects of different pulse electric field parameters

[0107] Comparative Example and Comparative Example 2 are set as follows on the basis of Example 1:

[0108] Comparative Example 1

[0109] The only difference between this comparative example and Example 1 is that the field intensity of the pulse electric field is 25 kV / cm and the number of pulses is 15.

[0110] Comparative Example 2

[0111] The only difference between this comparative example and Example 1 is that the field intensity of the pulse electric field is 45 kV / cm and the number of pulses is 25.

[0112] The cell damage rate of the osmanthus flowers treated in Example 1 and Comparative Examples 1 and 2 was observed under a scanning electron microscope (SEM), the PPO inactivation rate was tested by catechol colorimetric spectrophotometry, and the color change test was performed by a colorimeter ΔE value determination method. At the same time, the browning index was tested after being stored at room temperature for 180 days. The test results are shown in Table 1 below:

[0113] Table 1 Test results of treatment effects of different pulse electric field parameters

[0114] Examples Cell damage rate PPO inactivation rate ΔE value Browning Index Example 1 1.2％ 87.3％ 1.8 0.28 Example 2 2.7％ 99.5％ 0.9 0.12 Example 3 8.5％ 99.8％ 2.3 0.15

[0115] As shown in Table 1, when the parameters of the pulse electric field treatment of the present invention are changed, it is impossible to meet the product requirements of reducing the PPO activity by more than 99% and maintaining the browning index of the product below 0.15 after 180 days of storage at room temperature while maintaining the original morphology (cell damage rate <3%) and natural color (ΔE <1.5) of osmanthus.

[0116] (II) Storage stability test

[0117] Five groups of osmanthus flowers treated in Example 2 were randomly selected for storage stability test. The browning index, anthocyanin retention rate and total bacterial count were tested at room temperature (25° C.) for 0 days, 90 days and 180 days, respectively. The browning index, anthocyanin retention rate and total bacterial count were tested at low temperature (4° C.) for 180 days, 360 days and 540 days, respectively. The morphology of osmanthus flowers after 180 days of storage at room temperature is as follows: Figure 1 The test results are shown in Table 2 below:

[0118] Table 2 Storage stability test results

[0119]

[0120] As shown in Table 2, the browning index of the osmanthus treated by the technical solution of the present invention is still lower than 0.15 after being stored at room temperature for 180 days and at low temperature for 540 days, the anthocyanin retention rate is above 95%, and the total bacterial count also meets the use requirements.

[0121] (III) Test of treatment effects of different preparation processes

[0122] Comparative Examples 3-6 were prepared based on Example 1 as follows:

[0123] Comparative Example 3

[0124] The difference between this comparative example and Example 1 is that the magnetic Fe 3 O 4 @Chitosan microspheres were loaded with mixed enzyme solution, i.e., free enzyme was used to replace the immobilized enzyme, and ultrasound-assisted enzymolysis was not performed in this comparative example, and the enzymolysis reaction time was 180 min.

[0125] Comparative Example 4

[0126] The difference between this comparative example and Example 1 is that no ultrasonic treatment is performed and the reaction time is 120 min.

[0127] Comparative Example 5

[0128] The difference between this comparative example and Example 1 is that only a single tannase is used for direct enzymolysis (ie, no fixation is performed and no ultrasound-assisted enzymolysis is used), and the reaction time is 120 minutes.

[0129] Comparative Example 6

[0130] The difference between this comparative example and Example 1 is that the magnetic Fe 3 O 4 @Chitosan microspheres loaded with mixed enzyme solution, that is, free enzyme was used to replace immobilized enzyme, and the reaction time was 120min.

[0131] Three groups of osmanthus flowers obtained after treatment in Example 1 and Comparative Examples 3-6 were selected to test their tannin degradation rate, cell damage rate, and residual enzyme activity rate of tannase and / or laccase. The test results are shown in Table 3 below:

[0132] Table 3 Test results of different preparation process treatment effects

[0133] Examples Tannin degradation rate Cell damage rate Residual enzyme activity Reaction time Comparative Example 3 68.2±2.1％ 12.3±1.5％ - 180min Comparative Example 4 72.5±1.8％ 5.7±0.9％ 82.1％ 120min Example 1 87.6±1.2％ 3.2±0.5％ 85.3％ 90min Comparative Example 5 61.4±1.7％ 4.1±0.6％ 79.8％ 120min Comparative Example 6 75.8±1.9％ 6.7±1.0％ - 120min

[0134] As shown in Table 3, compared with other processes, the present invention adopts magnetic Fe 3 O 4 @Chitosan microspheres immobilize tannin enzyme (activity retention rate>85%) and laccase, and convert tannin into low molecular weight phenolic acid (such as gallic acid) through enzymatic hydrolysis. Ultrasonic wave-assisted enzymatic hydrolysis intermittent treatment is used to promote the penetration of enzyme molecules into the osmanthus tissue, which can shorten the reaction time by more than 20 minutes compared with other processes. Therefore, the present invention can completely retain the osmanthus morphology and active ingredients while achieving a tannin degradation rate of>87%, and the technical indicators are significantly better than the traditional acid-base treatment method (degradation rate ≤65%, cell damage rate>20%).

[0135] (IV) Test on the performance of reusable immobilized enzyme

[0136] The immobilized enzyme of Example 1 was repeatedly used to test the enzyme activity retention rate, microsphere breakage rate, magnetic recovery rate and tannin degradation rate of sweet osmanthus after being used once, five times and ten times. The test results are shown in Table 4 below.

[0137] Table 4 Immobilized enzyme repeatability test results

[0138] Use times Tannin degradation rate Enzyme activity retention Microsphere breakage rate Magnetic recovery rate 1 87.6％ 100％ 0％ 99.2％ 5 85.1％ 93.4％ 1.8％ 97.5％ 10 82.3％ 86.7％ 4.5％ 94.1％

[0139] As shown in Table 4, the immobilized enzyme of the present invention can still maintain a high tannin degradation rate after multiple uses, and the enzyme activity retention rate of the immobilized enzyme can still be maintained at more than 85% after multiple uses, the microsphere breakage rate is less than 5%, and the magnetic recovery rate is more than 90%. Therefore, the immobilized enzyme of the present invention can be recycled for multiple times, further reducing the process cost.

[0140] (V) Osmanthus quality index test

[0141] The untreated fresh osmanthus was tested for tannin content, anthocyanin retention rate and bitterness value (quinine equivalent), and its cell integrity was observed under SEM; the fresh osmanthus was then treated according to the technical scheme of Example 2, and its tannin content, anthocyanin retention rate, bitterness value (quinine equivalent) and cell integrity were tested. The test results are shown in Table 5 below.

[0142] Table 5 Osmanthus quality index test results

[0143] index Before treatment Example 2 After treatment Tannin content (mg / g) 12.3±0.5 1.5±0.2 Anthocyanin retention rate 100％ 99.4±0.3％ Cell integrity (SEM) Intact cells 98% Intact cells 94% Bitterness value (quinine equivalent) 0.15g / L 0.02g / L

[0144] As shown in Table 5, after being treated by the process of the present invention, the tannin content and bitterness value of osmanthus are significantly reduced, and anthocyanin retention rate and cell integrity can be maintained at a very high level.

[0145] (VI) Osmanthus jelly preparation test

[0146] To further illustrate the technical effect of the present invention, the osmanthus flowers treated in the above Examples 1-3 were used to prepare osmanthus jelly using the following preparation methods.

[0147] Example 1

[0148] A preparation process of the above-mentioned osmanthus jelly comprises the following steps:

[0149] (1) dissolving vitamin C in hot water at 85° C. at a solid-liquid ratio of 0.020:100, filtering to obtain an osmanthus extract, and pre-soaking the osmanthus treated in Example 1 in water for later use;

[0150] (2) The thickener is mixed and dispersed with syrup with a mass concentration of 59% in a mass ratio of 1:100 and then dissolved in water. After the thickener swells for 30 minutes, it is heated to 95°C. The heating is stopped and the temperature is cooled to 75°C. The following components are added in parts by mass: 0.3 parts of soaked osmanthus, 3 parts of osmanthus extract, 12 parts of yellow peach pulp, 0.01 parts of natural flavor, 0.1 parts of natural lutein, 0.1 parts of citric acid, 0.12 parts of sodium citrate, and 0.10 parts of vitamin C. After mixing and evenly stirring, fill the mixture, pasteurize at 90°C for 15 minutes, cool, and seal to obtain osmanthus jelly.

[0151] The thickener includes the following components in parts by weight: 0.1 part of carrageenan, 0.1 part of konjac flour, 0.15 part of agar, 0.05 part of locust bean gum, 0.2 part of potassium chloride and 0.3 part of calcium lactate.

[0152] Example 2

[0153] A preparation process of the above-mentioned osmanthus jelly comprises the following steps:

[0154] (1) dissolving vitamin C in hot water at 80° C. at a solid-liquid ratio of 0.025:100, filtering to obtain an osmanthus extract, and pre-soaking the osmanthus treated in Example 2 in water for later use;

[0155] (2) The thickener is mixed and dispersed with syrup with a mass concentration of 58% in a mass ratio of 1:60 and then dissolved in water. After the thickener swells for 10 minutes, it is heated to 96°C, and the heating is stopped. When the temperature is cooled to 80°C, the following components are added in parts by mass: 0.1 parts of soaked osmanthus, 1 part of osmanthus extract, 10 parts of yellow peach pulp, 0.02 parts of natural flavor, 0.01 parts of natural lutein, 0.2 parts of citric acid, 0.06 parts of sodium citrate, and 0.02 parts of vitamin C are mixed and stirred evenly, filled, pasteurized at 92°C for 10 minutes, and sealed after cooling to obtain osmanthus jelly.

[0156] The thickener includes the following components in parts by mass: 0.08 parts of carrageenan, 0.2 parts of konjac flour, 0.05 parts of agar, 0.2 parts of locust bean gum, 0.1 parts of potassium chloride and 0.1 parts of calcium lactate.

[0157] Example 3

[0158] A preparation process of the above-mentioned osmanthus jelly comprises the following steps:

[0159] (1) dissolving vitamin C in hot water at 83° C. at a solid-liquid ratio of 0.015:100, filtering to obtain an osmanthus extract, and pre-soaking the osmanthus treated in Example 1 in water for later use;

[0160] (2) The thickener is mixed and dispersed with syrup with a mass concentration of 58% in a mass ratio of 1:120 and then dissolved in water. After the thickener swells for 20 minutes, it is heated to 94°C. The heating is stopped and the temperature is cooled to 70°C. The following components are added in parts by mass: 0.5 parts of soaked osmanthus, 5 parts of osmanthus extract, 25 parts of yellow peach juice, 0.1 parts of natural flavor, 0.03 parts of natural lutein, 0.08 parts of citric acid, 0.18 parts of sodium citrate, and 0.18 parts of vitamin C. After mixing and evenly stirring, fill the mixture, pasteurize at 85°C for 20 minutes, cool, and seal to obtain osmanthus jelly.

[0161] The thickener includes the following components in parts by mass: 0.3 parts of carrageenan, 0.08 parts of konjac flour, 0.10 parts of agar, 0.1 parts of locust bean gum, 0.3 parts of potassium chloride and 0.5 parts of calcium lactate.

[0162] The sensory test of the osmanthus jelly prepared in the above examples 1-3 was conducted, and the osmanthus jelly tasted free of tannin bitterness, had the elegant and natural aroma of osmanthus, and had a good sweet and sour taste.

[0163] The osmanthus jelly prepared in the above-mentioned embodiment 2 and embodiment 3 is respectively as follows Figure 2 and Figure 3 As shown in the figure, it can be seen that the osmanthus jelly is prepared by using the osmanthus treated by the present invention, and the osmanthus inside can maintain the shape and color of fresh osmanthus, and the appearance is natural and beautiful.

[0164] The osmanthus jelly prepared in Example 1 was stored at room temperature for 9 months, and its appearance was compared. The appearance of the osmanthus jelly after 0 month and 9 months of storage was as follows: Figure 4 and Figure 5 As shown in the figure, after being stored at room temperature for 9 months, the color of the osmanthus jelly remained stable without browning, indicating that the osmanthus jelly prepared from the osmanthus treated by the present invention had a stable color and could maintain a natural appearance during the shelf life.

[0165] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A process for protecting the color of sweet osmanthus and degrading tannin, characterized in that: The following steps are involved: S1. Soaking in color protection liquid: Soak the selected fresh osmanthus in the color protection liquid for 8-12 minutes at a pH of 4.0-4.4 and a temperature of 4-8°C; S2, pulse electric field treatment: subjecting the sweet osmanthus treated with the color protection liquid to pulse electric field treatment; S3, low temperature gradient decompression: the osmanthus treated with pulse electric field is subjected to stepwise decompression at 4-8°C; S4, preparation of immobilized enzymes: magnetic Fe3O4@chitosan microspheres were used to load tannase and laccase to obtain immobilized enzymes; S5, ultrasound-assisted enzymatic hydrolysis; mixing the depressurized osmanthus and the immobilized enzyme at a solid-liquid ratio of 1:(13-17) (w / v), and subjecting to dual-frequency alternating ultrasound treatment for 15-25 minutes; S6, enzymolysis; stirring the osmanthus flowers after ultrasound-assisted enzymolysis at a temperature of 38-42° C. and a pH of 5.0-5.5 for 80-100 minutes; S7, vacuum dehydration: dehydrate the osmanthus flowers under vacuum conditions at a temperature of 45-50°C.

2. The process for protecting the color of sweet osmanthus and degrading tannins as claimed in claim 1, characterized in that: The color protecting liquid comprises ascorbic acid, citric acid and CaCl2 in a mass ratio of (0.25-0.35):(0.08-0.12):(0.04-0.06).

3. The process for protecting the color of sweet osmanthus and degrading tannins as claimed in claim 1, characterized in that: The parameters of the pulse electric field treatment are: field intensity 32-38 kV / cm, pulse width 38-42 μs, frequency 700-900 Hz, pulse number 15-25 times, medium temperature ≤8°C.

4. The process for protecting the color of sweet osmanthus and degrading tannins as claimed in claim 1, characterized in that: The pulse electric field treatment adopts an intermittent mode treatment of working for 3±1s and resting for 2±1s.

5. The process for protecting the color of sweet osmanthus and degrading tannins as claimed in claim 1, characterized in that: The stepwise pressure reduction includes three stages of pressure reduction. The first stage is to evacuate to -0.08 MPa and maintain it for 5 minutes. The second stage is to maintain it at -0.05 MPa for 5 minutes. The third stage is to restore to normal pressure.

6. The process for protecting the color of sweet osmanthus and degrading tannins as claimed in claim 1, characterized in that: The particle size of the magnetic Fe3O4@chitosan microspheres is 50-100 μm, the content of tannase is 1500-2500 U / g, and the content of laccase is 1200-1800 U / g.

7. The process for protecting the color of sweet osmanthus and degrading tannins as claimed in claim 1, characterized in that: The preparation method of the immobilized enzyme is as follows: magnetic Fe3O4@chitosan microspheres and a mixed enzyme solution including tannase and laccase are mixed at a ratio of 1 g: (4-6) mL, pre-adsorbed at 2-6°C for 0.8-1.2 hours, glutaraldehyde is slowly added dropwise to a final concentration of 0.7-0.9%, and cross-linked at a constant temperature of 2-6°C and 100-150 rpm for 2-3 hours to obtain the immobilized enzyme.

8. An osmanthus jelly, characterized in that: The invention comprises osmanthus flowers treated by the osmanthus flower color protection and tannin degradation process as described in any one of claims 1 to 7.

9. The process for preparing osmanthus jelly according to claim 8, characterized in that: The following steps are involved: (1) dissolving vitamin C in hot water at 80-85° C. at a solid-liquid ratio of (0.015-0.025):100, filtering to obtain an osmanthus extract, and pre-soaking the osmanthus treated by the osmanthus color protection and tannin degradation process according to any one of claims 1 to 6 in water for later use; (2) A thickener is mixed and dispersed with a syrup having a mass concentration of 58-60% in a mass ratio of 1:(60-120) and then dissolved in water. After the thickener swells for 10-30 minutes, it is heated to 95±1° C., the heating is stopped, and when the temperature is cooled to 70-80° C., the soaked osmanthus, osmanthus extract, fruit juice and / or pulp, natural essence, natural lutein, citric acid, sodium citrate, and vitamin C are added, mixed and stirred evenly, and then sterilized and cooled to obtain osmanthus jelly.

10. The process for preparing osmanthus jelly according to claim 9, characterized in that: The thickener comprises the following components in parts by weight: 0.08-0.3 parts of carrageenan, 0.08-0.2 parts of konjac flour, 0.05-0.15 parts of agar, 0.05-0.2 parts of locust bean gum, 0.1-0.3 parts of potassium chloride and 0.1-0.5 parts of calcium lactate.

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