Preparation method of tea oil diglyceride based on program-controlled crystallization and multi-stage molecular distillation

Abstract

This invention provides a method for preparing tea oil diglycerides based on programmed crystallization and multi-stage molecular distillation, comprising the following steps: S1. Enzymatic glycerol hydrolysis reaction: S1.1. Premixing tea oil and dehydrated glycerol under high pressure microemulsification to stabilize the microemulsion; S1.2. Transferring the microemulsion to a reactor, maintaining the temperature at 60-65℃, and establishing a system vacuum; adding lipase and reacting with stirring for 6-10 hours; S1.3. After the reaction, separating and recovering the immobilized enzyme, and removing the lower glycerol phase by static separation or centrifugation to obtain crude diglyceride oil; S2. Performing programmed crystallization for primary enrichment of the crude diglyceride oil to obtain a diglyceride-rich mother liquor; S3. Performing multi-stage molecular distillation for fine separation of the diglyceride-rich mother liquor obtained in S2. This method can prepare tea oil diglycerides with high purity, high 1,3-configuration content, and high activity retention.

Description

Technical Field

[0001] This invention belongs to the field of deep processing of oils and fats, specifically involving a method for preparing high-purity tea oil diglycerides with high 1,3-configuration content and high activity retention rate by using immobilized enzyme-catalyzed glycerolysis of tea oil as the core, and through an integrated process that couples programmed crystal enrichment with multi-stage molecular distillation. Background Technology

[0002] Diacylglycerol (DAG) is a functional oil with physiological functions such as lowering blood lipids and reducing visceral fat. Diacylglycerol prepared from tea oil has higher nutritional value due to its rich content of unsaturated fatty acids such as oleic acid. Currently, the enzymatic synthesis process for diacylglycerol is relatively mature, but it still has the following drawbacks: First, existing processes generally use a near-stoichiometric glycerol ratio (oil to glycerol molar ratio 1:1–2.5:1) and a high enzyme addition (4%–10%) to pursue a high single-pass conversion rate, resulting in high levels of byproducts (such as monoglycerides and free fatty acids) and residual glycerol in the subsequent separation system, leading to a heavy purification burden. Second, regarding purification, although there are reports of using molecular distillation technology, most employ simple 1–2-stage distillation, resulting in limited separation precision. This makes it difficult to simultaneously address the deep removal of both light components (free fatty acids, monoglycerides) and heavy components (triglycerides), hindering further improvements in product purity and configuration selectivity. Third, the reaction and separation stages in the existing process are independent of each other and lack synergistic design, failing to optimize product distribution and separation efficiency from the perspective of the whole process. Fourth, the traditional glycerol enzymatic hydrolysis method requires a small amount of water (the presence of water increases hydrolysis, and the acid value of crude oleic acid will reach more than 15 mg / g), resulting in high acid value and peroxide value. For example, Chinese patent CN201110092850.5 discloses a method for preparing functional oils rich in diglycerides, which requires the addition of a small amount of water during the preparation process.

[0003] Therefore, it is of great significance to develop an integrated process that optimizes product distribution from the reaction source to overcome technical bottlenecks such as low purity, poor configuration selectivity, and low activity retention of diglyceride products. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-purity tea oil diglycerides. By optimizing the substrate ratio at the reaction end and using programmed crystal enrichment and multi-stage molecular distillation for precise cutting at the separation end, the method achieves a diglyceride purity of ≥95% and a 1,3-diglyceride content of ≥85%, while retaining the active ingredients in the oil.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] S1. Enzymatic glycerol hydrolysis reaction:

[0007] S1.1. Tea oil and dehydrated glycerin are premixed at a mass ratio of (3.5-4.5):1, and then subjected to high-pressure microemulsification at 60-65℃ and 20-30MPa (gauge pressure) to form a stable microemulsion;

[0008] S1.2. Transfer the above microemulsion into a reactor, maintain the temperature at 60-65℃, and establish a system vacuum of -0.07--0.09MPa; add 2.5%-4.0% of immobilized 1,3-position specific lipase by weight of tea oil, and react for 6-10 hours with stirring at 300-500 rpm.

[0009] S1.3. After the reaction is complete, the immobilized enzyme is recovered by centrifugation or filtration, and the lower glycerol phase is removed by standing or centrifugation to obtain crude diglyceride oil.

[0010] S2. Primary enrichment of programmable crystals:

[0011] S2.1. Heat the crude diglyceride oil obtained in S1 to 55-60℃ to completely melt and homogenize it;

[0012] S2.2. Transfer the molten material into a programmed cooling crystallizer and slowly cool it to a final crystallization temperature of 4-10℃ at a rate of 0.1-0.3℃ / min, and then maintain the temperature at this final crystallization temperature for 4-12 hours.

[0013] S2.3. At the final crystallization temperature, a filter press or centrifuge with a cooling jacket is used for solid-liquid separation, and the liquid phase, i.e., the diglyceride-rich mother liquor, is collected.

[0014] S3. Multistage molecular distillation for fine separation:

[0015] The diglyceride-rich mother liquor obtained from S2 was sequentially separated using a multi-stage molecular distillation apparatus connected in series. The operating parameters and objectives for each stage are as follows:

[0016] First stage (dehydration and light content removal): distillation temperature 80-100℃, system pressure 50-200 Pa (absolute pressure), to remove trace amounts of water, dissolved oxygen and low-boiling-point solvents from the material.

[0017] Second stage (deacidification and deodorization): Distillation temperature 120-140℃, system pressure 10-30 Pa (absolute pressure), to remove free fatty acids, aldehydes and ketones, and some monoglycerides.

[0018] Third stage (cutting light glycerides): distillation temperature 150-165℃, system pressure 3-10 Pa (absolute pressure), cut and collect residual monoglycerides and some low molecular weight DAG.

[0019] Fourth stage (main product collection): Distillation temperature 170-185℃, system pressure 1-3 Pa (absolute pressure), collect high-purity diglyceride main fraction.

[0020] Preferably, in step S1.1, the mass ratio of tea oil to glycerin is 4:1.

[0021] Preferably, the amount of immobilized lipase added in step S1.2 is 3.0% of the mass of tea oil.

[0022] Preferably, in step S2.2, the cooling rate is 0.2℃ / min, the final crystallization temperature is 8℃, and the crystal growth time is 8 hours.

[0023] Preferably, the distillation conditions for each stage in step S3 are: first stage 95℃, 150 Pa; second stage 130℃, 20 Pa; third stage 160℃, 5 Pa; fourth stage 175℃, 2 Pa.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The process does not require external water addition and does not require separate dehydration. After the reaction, the content of diglycerides in the crude diglyceride oil can reach more than 60%, the acid value of crude oleic acid is less than 5 mg / g, and the peroxide value is less than 2 mmol / kg. This provides convenience for subsequent purification. Moreover, the DAG yield (>60%) is comparable to that of the traditional high enzyme amount process with only 3% low enzyme amount, which reduces enzyme cost. The traditional glycerol hydrolysis method requires a small amount of water and has a higher acid value and peroxide value. (2) Multi-stage molecular distillation is used for fine separation. Each stage has a clear and specific separation target, which overcomes the shortcomings of the traditional 1-2 stage distillation "one-size-fits-all" approach. It achieves full-dimensional fine separation of complex systems, so that the final product has a DAG purity of ≥95% and a 1,3-DAG ratio of ≥85%. (3) The high purity of the reaction product provides easy-to-handle material for crystallization. Crystallization removes triglycerides significantly, reducing the material load and viscosity of molecular distillation, forming a synergistic cycle of "the previous step reduces the burden on the next step, and the next step refines the previous step". The core separation temperature (fourth stage ≤185℃) is lower than that of conventional processes, and the retention rate of active ingredients such as vitamin E is >80%; multi-stage distillation effectively avoids risky substances such as glycidyl esters and 3-chloropropanol esters. Attached Figure Description

[0026] Figure 1 This is the state before separation after the reaction in Example 1. The upper layer is crude diglyceride oil, and the lower layer is glycerol. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0028] The tea oil described in the following examples has a molecular weight of 630. The immobilized lipase IM-NE100 was produced by Weifang Kangdian Biotechnology Co., Ltd.

[0029] Example 1

[0030] S1: Take 4.0 kg of refined tea oil and 1.0 kg of dehydrated glycerol (mass ratio 4:1), and perform high-pressure microemulsification at 25 MPa to form a stable microemulsion. Transfer the microemulsion to a reactor, maintain the temperature at 63℃, and establish a system vacuum of -0.08 MPa. Add 120 g of immobilized lipase IM-NE100 (3.0% of the tea oil mass), and react for 8 hours with stirring at 400 rpm. After the reaction, filter and recover the immobilized enzyme, such as... Figure 1 As shown, the upper layer is crude diglyceride oil, and the lower layer is glycerol. Centrifugation removed the lower glycerol phase, yielding 4.8 kg of crude diglyceride oil. Analysis revealed the following composition of the crude product: 28.5% triglycerides, 61.8% diglycerides (of which 1,3-diglycerides accounted for 73.5%), 7.2% monoglycerides, crude oleic acid value 4.6 mg / g, and peroxide value 1.6 mmol / kg.

[0031] S2: The crude product was heated to 58°C until completely melted and homogenized. It was then transferred to a programmed cooling crystallizer and slowly cooled to 8°C at a rate of 0.2°C / min, and maintained at this temperature for 8 hours. At the final crystallization temperature, a filter press with a cooling jacket was used for solid-liquid separation, and 3.5 kg of the liquid phase (DAG-rich mother liquor) was collected. Analysis showed that the DAG-rich mother liquor consisted of: 11.2% triglycerides, 79.5% diglycerides, and 6.5% monoglycerides.

[0032] S3: Pass the DAG-rich mother liquor sequentially through a four-stage short-path molecular distillation apparatus connected in series, with the following conditions for each stage:

[0033] First stage: Distillation temperature 95℃, system pressure 150 Pa, discard the light fraction;

[0034] Second stage: Distillation temperature 130℃, system pressure 20 Pa, collect the light fraction with higher acid value;

[0035] Third stage: Distillation temperature 160℃, system pressure 5 Pa, collect monoglyceride enriched fraction;

[0036] Fourth stage: Distillation temperature 175℃, system pressure 2 Pa, main product collected 1.82 kg.

[0037] Product testing results:

[0038] Total diglyceride content: 96.3%

[0039] 1,3-Diglycerides accounted for 87.5% of total diglycerides.

[0040] Acid value: 0.3 mg KOH / g

[0041] Peroxide value: 0.8 mmol / kg

[0042] Vitamin E retention rate: 82.1%

[0043] Glycidyl esters: Not detected (<0.05 mg / kg)

[0044] Comparative Example 1 (Traditional Two-Stage Distillation)

[0045] Take 3.5 kg of the same batch of S2 DAG-rich mother liquor and perform only two-stage distillation (first stage: 150℃ / 100Pa; second stage: 210℃ / 100Pa). 1.70 kg of product was obtained.

[0046] Total DAG content: 90.5%

[0047] 1,3-DAG percentage: 76.8%

[0048] Vitamin E retention rate: 65.4%

[0049] Glycidyl esters: 0.8 mg / kg (qualified)

[0050] Comparative studies have shown that four-stage distillation has significant advantages in purity, configuration selectivity, and safety.

[0051] Comparative Example 2

[0052] S1: 6.0 kg of refined tea oil and 1.0 kg of dehydrated glycerol (mass ratio 6:1) were subjected to high-pressure microemulsification at 25 MPa to form a stable microemulsion. The microemulsion was transferred to a reactor, and the temperature was maintained at 63℃ with a system vacuum of -0.08 MPa. 120 g of immobilized lipase IM-NE100 was added, and the reaction was carried out at 400 rpm for 8 hours. After the reaction, the immobilized enzyme was recovered by filtration, and the lower glycerol phase was removed by centrifugation to obtain 6.8 kg of crude diglyceride oil. The composition of the crude product was as follows: triglycerides 53.4%, diglycerides 40.4% (of which 1,3-diglycerides accounted for 68.9% of the diglycerides), and monoglycerides 6.2%, according to GB / T 26636-2011.

[0053] S2: The crude product was heated to 58°C until completely melted and homogenized. It was then transferred to a programmed cooling crystallizer and slowly cooled to 8°C at a rate of 0.2°C / min, and maintained at this temperature for 8 hours. At the final crystallization temperature, a filter press with a cooling jacket was used for solid-liquid separation, and 3.2 kg of the liquid phase (DAG-rich mother liquor) was collected. Analysis showed that the DAG-rich mother liquor composition was: triglycerides 35.8%, diglycerides 54.6%, and monoglycerides 9.6%.

[0054] S3: Pass the DAG-rich mother liquor sequentially through a four-stage short-path molecular distillation apparatus connected in series, with the following conditions for each stage:

[0055] First stage: Distillation temperature 95℃, system pressure 150 Pa, discard the light fraction;

[0056] Second stage: Distillation temperature 130℃, system pressure 20 Pa, collect the light fraction with higher acid value;

[0057] Third stage: Distillation temperature 160℃, system pressure 5 Pa, collect monoglyceride enriched fraction;

[0058] Fourth stage: Distillation temperature 175℃, system pressure 2 Pa, collect 1.6 kg of main product.

[0059] Product testing results:

[0060] Total diglyceride content: 92.1%

[0061] 1,3-Diglycerides accounted for 81.5% of total diglycerides.

[0062] Acid value: 0.5 mg KOH / g

[0063] Peroxide value: 1.2 mmol / kg

[0064] Vitamin E retention rate: 78.3%

[0065] Glycidyl esters: Not detected (<0.05 mg / kg).

[0066] Results Analysis: Comparative Example 2, using a higher oil-to-oil ratio (6:1), further suppressed monoglyceride formation, but the DAG conversion rate (40.4%) was significantly lower than that of Example 1 (61.8%). Despite undergoing the same purification steps, the final product DAG purity (92.1%) and 1,3-configuration ratio (81.5%) were both lower than those of Example 1, demonstrating that a higher oil-to-oil ratio is not always better; 4:1 was more optimized in this system.

[0067] Example 2

[0068] S1: 4.0 kg of refined tea oil and 1.0 kg of dehydrated glycerol (mass ratio 4:1) were subjected to high-pressure microemulsification at 25 MPa to form a stable microemulsion. The microemulsion was transferred to a reactor, and the temperature was maintained at 63℃ with a system vacuum of -0.08 MPa. 120 g of immobilized lipase IM-NE100 (3.0% of the tea oil mass) was added, and the reaction was carried out at 400 rpm for 6 hours. After the reaction, the immobilized enzyme was recovered by filtration, and the lower glycerol phase was removed by centrifugation to obtain 4.7 kg of crude diglyceride oil. The composition of the crude product was as follows: triglycerides 35.2%, diglycerides 55.1% (of which 1,3-diglycerides accounted for 72.0% of the diglycerides), monoglycerides 8.5%, free fatty acids and others 1.2%.

[0069] S2: The crude product was heated to 60℃ and completely melted and homogenized. It was then transferred to a programmed cooling crystallizer and slowly cooled to 8℃ at a rate of 0.2℃ / min, and maintained at this temperature for 8 hours. At the final crystallization temperature, a filter press with a cooling jacket was used for solid-liquid separation, and 3.1 kg of the liquid phase (DAG-rich mother liquor) was collected. Analysis showed that the DAG-rich mother liquor consisted of: 18.5% triglycerides, 71.8% diglycerides, 8.9% monoglycerides, and 0.8% free fatty acids and others.

[0070] S3: Pass the DAG-rich mother liquor sequentially through a four-stage short-path molecular distillation apparatus connected in series, with the following conditions for each stage:

[0071] First stage: Distillation temperature 95℃, system pressure 150 Pa, discard the light fraction;

[0072] Second stage: Distillation temperature 130℃, system pressure 20 Pa, collect the light fraction with higher acid value;

[0073] Third stage: Distillation temperature 160℃, system pressure 5 Pa, collect monoglyceride enriched fraction;

[0074] Fourth stage: Distillation temperature 175℃, system pressure 2 Pa, collect 1.75 kg of main product.

[0075] Product testing results:

[0076] Total diglyceride content: 94.7%

[0077] 1,3-Diglycerides accounted for 85.2% of total diglycerides.

[0078] Acid value: 0.4 mg KOH / g

[0079] Peroxide value: 1.0 mmol / kg

[0080] Vitamin E retention rate: 80.5%

[0081] Glycidyl esters: Not detected (<0.05 mg / kg).

[0082] Results analysis: Shortening the reaction time to 6 hours resulted in a decrease in DAG conversion rate (55.1% vs 61.8%), leading to a slightly lower final product yield and purity (94.7%) compared to Example 1, but still significantly better than Comparative Example 1, demonstrating that this process can obtain high-quality products within a wide reaction time window.

[0083] Example 3

[0084] S1: The steps are the same as in Example 1, but the reaction time is 10 hours (extended reaction time). 4.8 kg of crude diglyceride oil was obtained. Analysis showed that the crude product composition was: triglycerides 25.8%, diglycerides 63.5% (of which 1,3-diglycerides accounted for 74.1% of the diglycerides), monoglycerides 8.5%, free fatty acids and others 2.2%.

[0085] S2: The steps are the same as in Example 1. 3.6 kg of DAG-rich mother liquor was obtained. Analysis showed that the composition of the DAG-rich mother liquor was: triglycerides 9.8%, diglycerides 80.2%, monoglycerides 8.8%, free fatty acids and others 1.2%.

[0086] S3: The steps are the same as in Example 1. Collect 1.85 kg of the main product.

[0087] Product testing results:

[0088] Total diglyceride content: 96.8%

[0089] 1,3-Diglycerides accounted for 87.9% of total diglycerides.

[0090] Acid value: 0.3 mg KOH / g

[0091] Peroxide value: 0.7 mmol / kg

[0092] Vitamin E retention rate: 82.5%

[0093] Glycidyl esters: Not detected (<0.05 mg / kg).

[0094] Results analysis: Extending the reaction time to 10 hours slightly improved the DAG conversion rate, and also slightly improved the purity and configuration ratio of the final product, proving that the reaction tends to reach equilibrium within 8-10 hours, and that the process has good stability.

[0095] Example 4

[0096] S1: The steps are the same as in Example 1.

[0097] S2: The crude product was heated to 58℃ until completely melted and homogenized. It was then transferred to a programmed cooling crystallizer and slowly cooled to 6℃ at a rate of 0.15℃ / min, maintaining this temperature for 12 hours (adjusting the crystallization program). At the final crystallization temperature, a filter press with a cooling jacket was used for solid-liquid separation, collecting 3.3 kg of the liquid phase (DAG-rich mother liquor). Analysis showed that the DAG-rich mother liquor composition was: triglycerides 9.5%, diglycerides 80.8%, monoglycerides 8.5%, free fatty acids and others 1.2%.

[0098] S3: The steps are the same as in Example 1. Collect 1.80 kg of the main product.

[0099] Product testing results:

[0100] Total diglyceride content: 96.5%

[0101] 1,3-Diglycerides accounted for 87.0% of total diglycerides.

[0102] Acid value: 0.3 mg KOH / g

[0103] Peroxide value: 0.8 mmol / kg

[0104] Vitamin E retention rate: 83.0%

[0105] Glycidyl esters: Not detected (<0.05 mg / kg)

[0106] Results analysis: Using a slower cooling rate (0.15℃ / min), a lower final crystallization temperature (6℃), and a longer crystal growth time (12 hours), the crystallization and oil removal effect was comparable to that under the optimal conditions (0.2℃ / min, 8℃, 8h), and the product indicators were similar. This indicates that the program crystallization control parameters are adjustable within a certain range and can effectively serve subsequent distillation.

Claims

1. A method for preparing tea oil diglyceride based on program-controlled crystallization and multi-stage molecular distillation, characterized in that, The steps are as follows: S1. Enzymatic glycerol hydrolysis reaction: S1.

1. Tea oil and dehydrated glycerin are premixed at a mass ratio of (3.5-4.5):1, and then subjected to high-pressure microemulsification at 60-65℃ and 20-30 MPa to form a stable microemulsion. S1.

2. Transfer the above microemulsion into a reactor, maintain the temperature at 60-65℃, and establish a system vacuum of -0.07 to -0.09 MPa; add 2.5% to 4.0% of immobilized 1,3-position specific lipase by weight of tea oil, and react for 6 to 10 hours with stirring at 300 to 500 rpm. S1.

3. After the reaction is complete, the immobilized enzyme is recovered by centrifugation or filtration, and the lower glycerol phase is removed by standing or centrifugation to obtain crude diglyceride oil; S2. The crude diglyceride oil is subjected to primary enrichment by controlled crystallization to obtain a diglyceride-rich mother liquor; S3. The diglyceride-rich mother liquor obtained in S2 is subjected to multi-stage molecular distillation for fine separation.

2. The method for preparing tea oil diglyceride based on program control crystallization and multi-stage molecular distillation according to claim 1, characterized in that, The steps of the primary enrichment of the controlled crystal in step S2 are as follows: S2.

1. Heat the crude diglyceride oil obtained in S1 to 55-60℃ to completely melt and homogenize it; S2.

2. Transfer the molten material into a programmed cooling crystallizer and cool it to a final crystallization temperature of 4-10℃ at a rate of 0.1-0.3℃ / min, and then maintain the temperature at this final crystallization temperature for 4-12 hours. S2.

3. At the final crystallization temperature, a filter press or centrifuge with a cooling jacket is used for solid-liquid separation, and the liquid phase, i.e., the diglyceride-rich mother liquor, is collected.

3. The method for preparing tea oil diglyceride based on program control crystallization and multi-stage molecular distillation according to claim 1, characterized in that, In step S3, the specific method for the multi-stage molecular distillation fine separation is as follows: the diglyceride-rich mother liquor obtained in S2 is sequentially passed through a series of multi-stage molecular distillation devices for separation, and the operating parameters for each stage are as follows: First stage: Distillation temperature 80-100℃, system pressure 50-200 Pa; Second stage: Distillation temperature 120-140℃, system pressure 10-30 Pa; Third stage: Distillation temperature 150-165℃, system pressure 3-10 Pa; Fourth stage: Distillation temperature 170-185℃, system pressure 1-3 Pa.

4. The method for preparing tea oil diglycerides based on programmed crystallization and multi-stage molecular distillation according to claim 1, characterized in that, In step S1.1, the mass ratio of tea oil to glycerin is 4:

1.

5. The method for preparing tea oil diglyceride based on programmed crystallization and multi-stage molecular distillation according to claim 1, characterized in that, In step S1.2, the amount of immobilized lipase added is 3.0% of the mass of tea oil.

6. The method for preparing tea oil diglycerides based on programmed crystallization and multi-stage molecular distillation according to claim 2, characterized in that, In step S2.2, the cooling rate is 0.2℃ / min, the final crystallization temperature is 8℃, and the crystal growth time is 8 hours.

7. The method for preparing tea oil diglyceride based on programmed crystallization and multi-stage molecular distillation according to claim 3, characterized in that, The distillation conditions for each stage in step S3 are as follows: first stage 95℃, 150 Pa; second stage 130℃, 20 Pa; third stage 160℃, 5 Pa; fourth stage 175℃, 2 Pa.

Images