CN113943605B - A method for winterization and fractionation of microbial oil - Google Patents

Abstract

The present invention provides a method for winterization and fractionation of microbial oils. The method for winterization and fractionation of microbial oils comprises the following steps: 1) winterization after adding trisaturated fatty acid glycerides to ARA desolventized oil, wherein the mass ratio of the ARA desolventized oil to the trisaturated fatty acid glycerides is 2:1 to 1.25:1; the proportion of saturated fatty acids in the trisaturated fatty acid glycerides is not less than 90%; 2) plate and frame filtration fractionation. The microbial oil winterization and fractionation method provided by the present invention can form a large amount of stable crystal forms in the ARA desolventized oil in a short time, and can maintain the particle form for a long time, which is convenient for effective separation. The ARA desolventized oil can obtain a clear and transparent oil product at low temperature after one winterization and fractionation, and the method uses commonly used winterization separation equipment, which can be repeatedly recycled, takes less time, and is suitable for large-scale production.

Description

A method for winterization and fractionation of microbial oil

Technical Field

The present invention relates to the technical field of oil separation and purification, and more specifically, to a method for winterization and fractionation of microbial oil.

Background technique

Microbial oils are mainly composed of triglycerides, each of which contains fatty acids of different chain lengths and different degrees of saturation. Various fatty acid groups are bound to the glycerol backbone through ester bonds. However, microbial oils rich in polyunsaturated fatty acids are prone to flocculent precipitation when stored at low temperatures. Such microbial oils need to be further processed to separate the solid fats that are prone to flocculent or precipitated and retain the liquid oils. Due to the large differences in the fatty acid structures of different microbial oils, there is a certain complexity in further separating the liquid oils.

Arachidonic acid oil is abbreviated as ARA. Its fatty acid composition is unique. The distribution of saturated fatty acids makes it possible to separate solid oils with a proportion of less than 20% or even less at low temperatures. In addition, since the distribution of saturated fatty acids is not symmetrical, when ARA is used in the conventional low-temperature separation of solid and liquid oils, it will appear as flocculent and condensed fine crystals, which not only requires a long condensation time, but also brings great difficulty to the subsequent filtration and separation operations, thereby affecting the stability of the obtained liquid oil during storage.

In the face of the purification problem of ARA oil, the existing technology usually uses solvent method for cooling and purification, such as adding acetone and other solvents in ZL02828043 to help the long-chain saturated fatty acids in ARA to settle, but the solvent method requires the product to be desolventized again, and it deviates from the currently advocated solvent-free extraction and purification process. At the same time, in the separation and filtration of microbial oils, plate and frame filtration is widely used in the actual production process because of its economy and high efficiency. However, in the existing technology, winterizing microbial oils and then using plate and frame filtration cannot effectively and economically obtain oil products that remain clear and transparent at low temperatures.

The urgent problem to be solved for the separation of liquid oil in ARA oil is how to make the long-chain saturated fatty acids in ARA oil with low solid fat content precipitate in a short time, and the precipitated solid fat can be beneficial to the subsequent separation plate and frame filtration process.

Summary of the invention

The object of the present invention is to provide a method for winterizing and fractionating microbial oils, which comprises the following steps:

1) adding trisaturated fatty acid glyceride to the ARA desolventized oil and then winterizing it, wherein the mass ratio of the ARA desolventized oil to the trisaturated fatty acid glyceride is 2:1 to 1.25:1; and the proportion of saturated fatty acids in the trisaturated fatty acid glyceride is not less than 90%;

2) Plate and frame filtration and fractionation;

The saturated fatty acid in the tri-saturated fatty acid glyceride is a long-chain saturated fatty acid having 14-18 carbon atoms.

The present invention has found through extensive research that after adding a certain mass ratio of trisaturated fatty acid glycerides (wherein the proportion of saturated fatty acids is not less than 90%) before the winterization step of the ARA desolventized oil that requires plate and frame filtration, a large amount of solid fat can be formed and precipitated in a short time after winterization. After one winterization and fractionation of the ARA desolventized oil, a clear and transparent oil product at low temperature can be obtained.

In the present invention, the tri-saturated fatty acid glyceride can be selected from commercially available tri-saturated fatty acid glyceride, which can be processed by conventional means, as long as the proportion of the corresponding saturated fatty acids in the tri-saturated fatty acid glyceride is ensured to be not less than 90%.

In a preferred embodiment of the present invention, the trisaturated fatty acid glyceride used in the present invention is prepared from glycerol and saturated fatty acids under metal base catalysis. The specific preparation method is preferably: glycerol, saturated fatty acids and metal base catalysts are mixed in a molar ratio of 1: (3-5): (3-5), nitrogen is introduced at 180-190 ° C and stirred for 24-48h, cooled to 80-85 ° C, water is added and stirred for 1-3h, and then stratified, the supernatant is added with silicon dioxide, and after stirring at 80-85 ° C for 1-3h, filtered. Wherein, the amount of water added is preferably 50-100% of the total mass of oil in the reaction system. The amount of silicon dioxide added is preferably 4-8% of the total mass of oil in the reaction system. Wherein, the metal base catalyst is preferably one of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide.

In the present invention, unless otherwise specified, "%" means mass percentage.

In the present invention, the saturated fatty acid in the trisaturated fatty acid glyceride is preferably palmitic acid, and the trisaturated fatty acid glyceride is preferably tripalmitin, wherein the proportion of palmitic acid is not less than 90%. In a preferred embodiment of the present invention, the preparation method of tripalmitin used in the present invention comprises the following steps: mixing glycerol, palmitic acid and a catalyst in a molar ratio of 1:(3-5):(3-5), introducing nitrogen at 180-190°C and stirring for 24-48h, cooling to 80-85°C, adding water and stirring for 1-3h, and then standing for stratification, taking the supernatant and adding silicon dioxide, stirring at 80-85°C for 1-3h, and filtering.

In a preferred embodiment of the present invention, the specific steps of winterization include:

The ARA desolventized oil was heated to 80-85°C under nitrogen protection, trisaturated fatty acid glycerides were added according to the mass ratio, stirred and mixed, cooled to the crystallization temperature at an average rate of 0.4-3°C/h while stirring, and kept warm for more than 16 hours.

In order to further improve the fractionation effect, the average cooling rate is preferably 0.4-1°C/h.

In a preferred embodiment of the present invention, the specific steps of "plate and frame filtration fractionation" in step 2) include:

The liquid oil is collected by filtering with a plate-and-frame machine at a filtering pressure of 1 to 3 bar, wherein the filter cloth of the plate-and-frame machine is preferably 3000 mesh.

In this method, due to the addition of trisaturated fatty acid glycerides of a specific mass ratio (wherein the proportion of saturated fatty acids is not less than 90%), the filtration pressure can be effectively reduced, and preferably, the solid esters can be separated smoothly at 1-1.5 bar. The obtained product begins to have a cloud point at least after 100 hours. Under this pressure, the filter cake layer is well formed, and other fine solid fats can be intercepted, and the soft fat permeability is better. The higher the pressure, the fine solid fats will penetrate, affecting the clarity level of the oil.

After filtering through the plate and frame, the liquid oil is collected to obtain the ARA oil after winterization and fractionation, which can be subjected to subsequent product processing, such as deodorization, according to production needs. The solid fat remaining in the plate and frame is the trisaturated fatty acid glyceride (preferably tripalmitin) used in the method of the present invention, which can be reused many times after simple treatment. In the actual operation process, in order to make the reused trisaturated fatty acid glyceride more purified, the solid fat in the plate and frame can be returned to 40°C and maintained for 8 hours, and then the melted oil can be blown out by nitrogen for subsequent deodorization to produce other products. The solid fat remaining in the plate and frame is the purified trisaturated fatty acid glyceride.

The ARA desolventized oil in the present invention is a triglyceride rich in arachidonic acid obtained by a fermentation method. It is well known to those skilled in the art that the ARA desolventized oil is usually obtained by extracting dry bacteria to obtain crude oil, and then hydrating, alkali refining, decolorizing, and desolventizing.

The method provided by the present invention is particularly suitable for ARA desolvated oil whose solid fat content is not higher than 20% at room temperature and low temperature (usually below 10°C), that is, in a preferred embodiment of the present invention, the solid fat content in the ARA desolvated oil is not higher than 20%.

Another object of the present invention is to provide a tri-saturated fatty acid glyceride that reduces the difficulty of winterization and fractionation of microbial oils and fats, and the preparation method of the tri-saturated fatty acid glyceride comprises the following steps:

Glycerol, saturated fatty acid and metal base catalyst are mixed in a molar ratio of 1:(3-5):(3-5), nitrogen is introduced at 180-190°C and stirred for 24-48 hours, the temperature is lowered to 80-85°C, water is added, stirred for 1-3 hours, and then allowed to stand for stratification, silicon dioxide is added to the supernatant, stirred at 80-85°C for 1-3 hours, and then filtered.

In the above scheme, a preferred method is a tripalmitin glyceride that reduces the difficulty of winterization and fractionation of microbial oils and fats, and the preparation method of the tripalmitin glyceride comprises the following steps:

Glycerol, palmitic acid and a metal catalyst are mixed in a molar ratio of 1:(3-5):(3-5), nitrogen is introduced at 180-190°C and stirred for 24-48 hours, the temperature is lowered to 80-85°C, water is added, stirred for 1-3 hours, and then allowed to stand for stratification, silicon dioxide is added to the supernatant, and the mixture is stirred at 80-85°C for 1-3 hours and filtered to obtain the product.

In the above scheme, the amount of water added is preferably 50-100% of the total mass of the oil in the reaction system. The amount of silicon dioxide added is preferably 4-8% of the total mass of the oil in the reaction system. Among them, the metal base catalyst can be specifically preferably sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide.

The present invention provides a method for winterization and fractionation of microbial oils, which is particularly suitable for ARA desolventized oils with a solid fat content of no more than 20% at room temperature. The method can form a large amount of stable crystal forms in the ARA desolventized oil in a short time, and can maintain the particle form for a long time, which is convenient for effective separation. It is a method for purifying oils that can effectively reduce the difficulty of subsequent plate-frame filtration fractionation. ARA desolventized oil can obtain a clear and transparent oil product at low temperature after winterization fractionation once, and the method uses a commonly used winterization separation equipment, which can be repeatedly recycled, takes less time, and is suitable for large-scale production. The oil product obtained by the method of the present invention has excellent clarity, high antifreeze quality, and is easy to industrialize.

Detailed ways

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Unless otherwise specified, the preparation method of tripalmitin (PPP) prepared in the embodiment of the present invention is:

(1) Glycerol and palmitic acid were used to prepare high-purity tripalmitin (PPP) under metal base catalysis. The two raw materials (glycerol and palmitic acid) were mixed with a metal base catalyst in a molar ratio of 1:3:3, and nitrogen was introduced at 180°C for 24 hours under stirring.

(2) Cool down to 80°C, add 85°C pure water which is 50% (w:w) of the mixed oil by weight, stir at 80-85°C for 1 hour, and then let stand to separate the layers.

(3) The supernatant in step (2) was added with 5% (w:w) silica by weight of oil, and stirred at 80-85° C. for 1 h. The PPP was filtered to obtain tripalmitin PPP, with a PPP content of 92%, and the mixture was set aside.

Example 1

In the blending tank, 800 kg ARA refined desolventized oil (18% solid fat) at an oil temperature of 85°C was added with 640 kg prepared PPP at 80-85°C at a rotation speed of 100 rpm and mixed for 1 hour. Then it was transferred to a ² m3 winterization tank and cooled at an average rate of 2°C/h at a rotation speed of 15 rpm. When it dropped to 0°C, the rotation speed was maintained at 15 rpm for 16 hours of crystal growth.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate steadily decreases and the filtration pressure needs to be increased.

(2) At the highest filtration pressure of 1.5 bar, 650 kg of liquid oil was collected. 5 g was taken and placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, and placed in 0°C water for testing. After 168 hours of observation, the oil in the bottle began to have a cloud point; the solid fat extracted in the previous extraction was hard and difficult to soften at room temperature, and the particle size test was 150-250 μm.

Example 2

The method provided in this embodiment is substantially the same as the method in Embodiment 1, except that in this embodiment, the average cooling rate during crystallization is adjusted to 1° C./h.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate is stable and slightly attenuated, and there is no need to increase the filtration pressure.

(2) Under the highest filtration pressure of 1 bar, 544 kg of liquid oil was collected, 5 g of which was put into a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, and placed in 0°C water for testing. No cloud point appeared after 168 hours of observation; the solid fat extracted in the previous extraction was hard and difficult to soften at room temperature, and the particle size was detected to be 240-300 μm.

Example 3

In the blending tank, add 800 kg ARA refined desolventized oil (18% solid fat) at 85°C and 400 kg PPP at 80-85°C at 100 rpm and mix for 1 hour. Then transfer it to a ² m3 winterization tank and cool it at an average rate of 1°C/h at 15 rpm. When it drops to 0°C, keep the speed at 15 rpm for 16 hours of crystal growth.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate is stable and slightly attenuated, and there is no need to increase the filtration pressure.

(2) At the highest filtration pressure of 1 bar, 636 kg of liquid oil was collected, 5 g of which was placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, and placed in 0°C water for testing. No cloud point appeared after 168 hours of observation; the solid fat extracted in the previous extraction was hard and difficult to soften at room temperature, and the particle size was detected to be 200-270 μm.

Example 4

The method provided in this embodiment is substantially the same as the method in embodiment 3, except that in this embodiment, the average cooling rate during crystallization is adjusted to 0.4° C./h.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate is stable and slightly attenuated, and there is no need to increase the filtration pressure.

(2) At the highest filtration pressure of 1 bar, 628 kg of liquid oil was collected, 5 g of which was placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, and placed in 0°C water for testing. No cloud point appeared after 168 hours of observation; the solid fat extracted in the previous extraction was hard and difficult to soften at room temperature, and the particle size was detected to be 280-310 μm.

Example 5

The method provided in this embodiment is basically the same as the method in Example 3, except that the tripalmitin PPP used in this embodiment is commercially available tripalmitin PPP, and is extracted by a solvent method so that the proportion of palmitic acid is >90%.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate is stable and slightly attenuated, and there is no need to increase the filtration pressure.

(2) At the highest filtration pressure of 1 bar, 628 kg of liquid oil was collected. 5 g was taken and placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, placed in 0°C water for testing, and no cloud point appeared after 168 hours of observation; the solid fat extracted in the previous extraction was hard and not easy to soften at room temperature, and the particle size test was 220-300 μm.

Example 6

The method provided in this embodiment is basically the same as the method in Example 3, except that the tripalmitin PPP used in this embodiment is commercially available tripalmitin PPP, which is extracted by a solvent method so that the proportion of palmitic acid is 83%.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate steadily decreases and the filtration pressure needs to be increased.

(2) At the highest filtration pressure of 1.5 bar, 635 kg of liquid oil was collected, 5 g of which was placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, placed in 0°C water for testing, and the cloud point was observed after 120 hours; the solid fat extracted in the previous extraction was hard and difficult to soften at room temperature, and the particle size was detected to be 180-260 μm.

Example 7

The tristearin sss used in this embodiment is commercially available tristearin, which is fractionated by a solvent method so that the proportion of stearic acid is greater than 90%.

800 kg of ARA refined desolventized oil (18% solid fat) at an oil temperature of 90°C and 400 kg of SSS were transferred into a ² m3 winterization tank, and the temperature was directly reduced at an average rate of 1°C/h at a speed of 15 rpm. When the temperature dropped to 0°C, the speed was maintained at 15 rpm for 16 hours of crystal growth.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate is stable and slightly attenuated, and there is no need to increase the filtration pressure.

(2) Under the highest filtration pressure of 1.0 bar, 560 kg of liquid oil was collected. 5 g was taken and placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, placed in 0°C water for testing, and no cloud point appeared after 168 hours of observation; the solid fat extracted in the previous extraction was hard and difficult to soften at room temperature, and the particle size test was 200-250 μm.

Example 8

The method provided in this embodiment is substantially the same as the method in Embodiment 1, except that in this embodiment, the average cooling rate during crystallization is adjusted to 3° C./h.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate decays rapidly in the early stage of separation, and the filtration pressure needs to be increased.

(2) Under the maximum filtration pressure of 2 bar, 685 kg of liquid oil was collected, 5 g of which was placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, and placed in 0°C water for testing. After 5 minutes of observation, the oil in the bottle began to show a cloud point; the solid fat extracted from the previous extraction was soft and easy to melt at room temperature, and the particle size was detected to be 10 to 70 μm.

Comparative Example 1

800 kg of ARA refined desolventized oil (18% solid fat) at 85°C in the blending tank was transferred into a ² m3 winterization tank, and directly cooled at an average rate of 1°C/h at a speed of 15 rpm. When it dropped to 0°C, the speed was maintained at 15 rpm for 16 hours of heat preservation and crystal growth.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate steadily decreases and the filtration pressure needs to be increased.

(2) At the maximum filtration pressure of 2.5 bar, 650 kg of liquid oil was collected, 5 g of which was placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, and placed in 0°C water for testing. After 5 minutes of observation, the oil in the bottle began to show a cloud point; the separated solid fat was soft and easy to melt at room temperature, and the particle size was detected to be 10 to 70 μm.

Comparative Example 2

In the blending tank, 800 kg of ARA refined desolventized oil (20% solid fat content) at an oil temperature of 85°C and 40 kg of prepared PPP were transferred into a ² m3 winterization tank, and directly cooled at an average rate of 0.4°C/h at a speed of 15 rpm. When it dropped to 0°C, the speed was maintained at 15 rpm for 16 hours of crystal growth.

Through the plate and frame machine with a filtration area of 10㎡ and a 3000 mesh filter cloth:

(1) When using a filtration pressure of 1 bar, the oil filtration rate steadily decreases and the filtration pressure needs to be increased.

(2) At the highest filtration pressure of 1.5 bar, 642 kg of liquid oil was collected, 5 g of which was placed in a glass bottle with a sealed lid, filled with nitrogen for protection and sealed with a lid, placed in 0°C water for testing, and the cloud point was observed for about 18 hours; the solid fat extracted in the previous extraction was hard but easy to soften at room temperature, and the particle size was detected to be 70-250 μm.

In Example 1, the yield of the soft fat product is 81.3%, and the maximum filtration pressure of 1.5 bar is required for fractionation. Solid fat is mixed in the product, and its antifreeze property is not strong; the yield of the soft fat product in Example 2 is 68%, and the yield of the product is reduced due to the large amount of PPP added, but there is no solid fat that can be formed at 0°C in the product, and its antifreeze property is strong; the yield of the soft fat product in Example 3 is 79.5%, the solid fat crystals are large and easy to filter, and the fractionation only requires a maximum filtration pressure of 1 bar, and its antifreeze property is strong. The yield of the soft fat product in Example 4 is 78.5%. Although the product also has the characteristics of strong antifreeze property, the slow cooling rate affects the working hours and production capacity. The effect of the method provided in Example 5 is slightly worse than that of Examples 3 and 4. The tripalmitin added in Example 6 has a lower purity, and the crystals are small during winterization, and the pressure needs to be increased to effectively filter. Example 7 uses stearic acid> 90% of tristearin sss, which is slightly worse than tripalmitin. The yield of the soft fat product in Example 8 was 104.4%. Due to the presence of fine solid fat crystals, the maximum filtration pressure of 2 bar was required for separation, and solid fat was mixed in the product, and its antifreeze property was poor. In Comparative Example 1, the crystals were small, and a higher pressure was required for separation, and the separation effect was poor, resulting in a cloud point in the antifreeze test. The yield of the soft fat product in Comparative Example 2 was 80.3%. Due to the presence of fine solid fat crystals, the maximum filtration pressure of 1.5 bar was required for separation, and a small amount of solid fat was mixed in the product, and its antifreeze property was average.

Finally, the method of the present invention is only a preferred embodiment and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. The winterization and fractionation method for the microbial oil is characterized by comprising the following steps of:

1) Adding trisaturated fatty glyceride into ARA desolventized oil, and then wintering, wherein the mass ratio of the ARA desolventized oil to the trisaturated fatty glyceride is 2:1-1.25:1; the ratio of saturated fatty acid in the trisaturated fatty acid glyceride is not less than 90%; the winterization method specifically comprises the following steps:

heating ARA desolventized oil to 80-85 ℃ under the protection of nitrogen, adding the trisaturated fatty glyceride according to the mass ratio, stirring and mixing, cooling to the crystallization temperature while stirring at the average speed of 0.4-1 ℃/h, and preserving the temperature for more than 16 hours;

2) Filtering and separating the plate frames;

wherein the saturated fatty acid in the tri-saturated fatty acid glyceride is palmitic acid; the trisaturated fatty acid glyceride is tripalmitin.

2. The method according to claim 1, wherein the trisaturated fatty acid glyceride is produced from glycerin and a saturated fatty acid under the catalysis of a metal base.

3. The method according to claim 2, wherein the method for preparing the trisaturated fatty acid glyceride comprises the steps of:

mixing glycerol, saturated fatty acid and metal base catalyst according to the mole ratio of 1 (3-5), introducing nitrogen at 180-190 ℃ to stir and react for 24-48h, cooling to 80-90 ℃, adding water to stir for 1-3h, standing and layering, taking supernatant, adding silicon dioxide, stirring for 1-3h at 80-90 ℃, and filtering.

4. A method according to claim 3, wherein the water is added in an amount of 50 to 100% of the total mass of oil in the reaction system, and the silica is added in an amount of 4 to 8% of the total mass of oil in the reaction system.

5. The method according to claim 3 or 4, wherein the metal base catalyst is one or more of sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide.

6. The method of claim 1, wherein the ARA desolventizing oil has a fat solids fraction of no more than 20%.

7. The method according to claim 1, wherein the specific step of "plate-and-frame filtration fractionation" in step 2) comprises:

and filtering by using a plate frame machine under the highest filtering pressure of 1-3 bar, and collecting liquid oil.

8. The method of claim 7, wherein the filter cloth of the frame machine is 3000 mesh.