CN113575696B - Preparation method of structural lipid based on breast milk triglyceride composition - Google Patents

Preparation method of structural lipid based on breast milk triglyceride composition Download PDF

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CN113575696B
CN113575696B CN202110874475.3A CN202110874475A CN113575696B CN 113575696 B CN113575696 B CN 113575696B CN 202110874475 A CN202110874475 A CN 202110874475A CN 113575696 B CN113575696 B CN 113575696B
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CN113575696A (en
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邹孝强
晁仲昊
徐秀丽
姜萱
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    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
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    • A23D9/00—Other edible oils or fats, e.g. shortenings, cooking oils
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    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
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Abstract

The invention discloses a preparation method of structural lipid based on breast milk triglyceride composition, which comprises the following steps: primary acidolysis, low-temperature fractionation, regulation of sn-2 fatty acid composition of liquid oil, regulation of free fatty acid composition, regulation of triglyceride composition, and secondary acidolysis. The preparation method of the structured lipid provided by the invention can reduce the cost and the generation of harmful substances, and simultaneously realizes the purpose and controllability of substrate reaction condition screening under the condition of ensuring that the components are highly similar to those of breast milk, thereby being beneficial to obtaining products with higher similarity to breast milk fat.

Description

Preparation method of structural lipid based on breast milk triglyceride composition
Technical Field
The invention relates to the technical field of grease, in particular to a preparation method of structural lipid based on breast milk triglyceride.
Background
Breast milk provides a variety of nutrients to infants and is the best food source for infants. Breast milk contains 3-5% of fat, and provides various functional fatty acids and fat-soluble vitamins while providing energy. The content of triglycerides in the fat of breast milk is more than 98%, and these triglycerides have specific fatty acid compositions and molecular structures, and the compositions of the triglycerides are different according to the lactation stage, the eating habits of mothers, personal conditions, genetic characteristics and the like. The main fatty acids (more than 1%) in breast milk fat are oleic acid, palmitic acid, linoleic acid, stearic acid, myristic acid, lauric acid, linolenic acid, capric acid and the like, wherein more than 60% of palmitic acid is at the sn-2 position, and most unsaturated fatty acids are mainly at the sn-1 and 3 positions. The composition of the triglyceride of breast milk fat is complex, and according to the distribution of fatty acid, the main triglyceride in the breast milk fat is 1, 3-polyunsaturated fatty acid-2-palmitic acid triglyceride (UPU), and the triglyceride with the structure can enhance the absorption of fat and calcium and influence the metabolism of the triglyceride in the infant. The composition and content of triglycerides in breast milk fat is a result of long-term evolution. The infant has a poor development and has a digestive and metabolic environment different from that of an adult, wherein the gastric lipase activity of the infant is similar to that of the adult, the pancreatic lipase concentration is only 5-10% of that of the adult, the bile salt content is less than 50%, and the fatty acid desaturase and the elongase activity of the infant are low. Therefore, the triglyceride composition of oil is closely related to the digestion, absorption and metabolism of infants.
Currently, in terms of structural lipid production that mimics breast milk fat, product constraints are largely imposed on the fatty acid level due to the lack of necessary means. The commercial production of products for regulating the lipid structure of formula milk powder fat mainly takes oleic acid and palm stearin as raw materials, obtains products rich in OPO by the catalytic acidolysis of sn-1,3 lipase, and limits the products mainly from the level of fatty acid, and the concerned triglyceride is mainly the content of OPO, and lacks the attention to other triglyceride of breast milk fat. Due to the wide variety of fatty acid arrangements on the glycerol backbone, the triglyceride composition may be quite different even though the fatty acid composition and distribution are the same. Therefore, there is a need to establish new production methods and evaluation tools to produce products that are not only similar to breast milk fat at the fatty acid level, but also similar in triglycerides.
Disclosure of Invention
This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.
The present invention has been made in view of the above and/or problems with existing structured lipid products based on the composition of breast milk triglycerides.
Therefore, one of the objectives of the present invention is to overcome the disadvantages of the existing structured lipid products based on the composition of breast milk triglycerides, and to provide a method for preparing structured lipids based on the composition of breast milk triglycerides.
To solve the above technical problem, according to an aspect of the present invention, the present invention provides the following technical solutions: a method for preparing structural lipid based on breast milk triglyceride composition is characterized in that: the method comprises the following steps:
primary acidolysis: the method comprises the following steps of (1) taking palm stearin as a raw material, selecting vegetable oil fatty acid rich in oleic acid and linoleic acid as an acyl donor, taking sn-1,3 lipase as a catalyst, and reducing the content of sn-1,3 palmitic acid by one-time acidolysis in a packed bed reactor;
low-temperature fractionation: removing saturated fatty acid and saturated triglyceride by a low-temperature fractionation procedure to obtain liquid oil;
adjusting the sn-2 fatty acid composition of the liquid oil: establishing a sn-2 fatty acid mixed model, and adjusting the composition of sn-2 fatty acid of liquid oil;
modulating sn-1,3 fatty acid composition: establishing an acidolysis reaction fatty acid balance model to obtain a substrate ratio and a free fatty acid composition which meet the requirements of the composition of the breast milk fat sn-1,3 fatty acid;
adjusting the free fatty acid composition: establishing a fatty acid mixed model, and obtaining free fatty acid composition and substrate ratio which meet the regulation of sn-1,3 fatty acid composition steps;
adjusting triglyceride composition: establishing an acidolysis reaction triglyceride balance model to obtain a free fatty acid composition meeting the breast milk fat triglyceride composition;
secondary acidolysis: obtaining the product with the same composition and distribution of the fatty acid of the breast milk and the composition of the triglyceride.
As a preferred embodiment of the method for preparing structural lipids based on the composition of breast milk triglycerides according to the present invention, wherein: in the primary acidolysis, the vegetable oil rich in oleic acid is one or two of rapeseed oil and tea seed oil; the vegetable oil rich in linolenic acid is one or two of soybean oil and sunflower seed oil.
As a preferred embodiment of the method for preparing structural lipids based on the composition of breast milk triglycerides according to the present invention, wherein: in the primary acidolysis, the reaction condition is that fatty acid and palm stearin are mixed according to the ratio of 4-8: 1.
As a preferred embodiment of the method for preparing structural lipids based on the composition of breast milk triglycerides according to the present invention, wherein: the enzymes used in the primary acidolysis and the secondary acidolysis are sn-1,3 lipase, and the sn-1,3 lipase comprises one or more of Lipozyme RM IM, NS40086 and lipase DF.
As a preferred embodiment of the method for preparing structural lipids based on the composition of breast milk triglycerides according to the present invention, wherein: in the primary acidolysis and the secondary acidolysis, the temperature is set to be 50-60 ℃.
As a preferred embodiment of the method for preparing structural lipids based on the composition of breast milk triglycerides according to the present invention, wherein: in the low-temperature fractionation, heating the oil to 55-65 ℃ and maintaining for 20-30 min, then reducing the temperature to 35-40 ℃ at a speed of 4-10 ℃/h, growing crystals for 3-5 h, then reducing the temperature to 18-28 ℃ at a speed of 3-8 ℃ for 2-8 h, and filtering and separating saturated fatty acid and solid fat after fractionation and crystallization are finished to obtain liquid oil.
As a preferred embodiment of the method for preparing structural lipids based on the composition of breast milk triglycerides according to the present invention, wherein: the sn-2 fatty acid mixed model is a calculation model for establishing the sn-2 fatty acid composition of the grease according to the fatty acid composition and distribution of the vegetable oil and the composition range of the sn-2 fatty acid of breast milk fat as follows:
Figure BDA0003189883580000031
wherein sn-2 FA% is sn-2 fatty acid composition of the mixed oil, Y represents different fatty acids, and Y represents1(sn-2)And Yi(sn-2)The mole percentage of each fatty acid on the sn-2 position of the palm stearin and the selected oil respectively, XiThe molar ratio of the selected grease to the palm stearin is adopted;
by setting XiAccording to the formula, the fatty acid composition and distribution in the mixed system can be calculated, an inequality is established according to the sn-2 fatty acid range of breast milk fat, and the addition range of each oil in the range is calculated.
When mixing, the minimum amount of exogenous vegetable oil is added while satisfying the fatty acid composition at the sn-2 site of breast milk fat. The addition amount of the exogenous vegetable oil is as follows:
Figure BDA0003189883580000032
Xithe molar ratio of the selected grease to the palm stearin; m is the sum of the proportion of the selected grease. In order to ensure that the mixed oil has the maximum sn-2 palmitic acid content, on the basis of ensuring that the sn-2 fatty acid is in the fat range of breast milk, the minimum amount of exogenous oil needs to be added, and Matlab R2010a (MathWorks, Natick, MA, USA) is adopted to optimize the adding proportion of the oil;
the oil selected for adjusting the sn-2 fatty acid composition is one or more of coconut oil, palm kernel oil, soybean oil and linseed oil;
as a preferable embodiment of the method for producing structural lipids based on the composition of breast milk triglycerides of the present invention, wherein: the substrate ratio and the fatty acid ratio range required by the composition and distribution of the breast milk fatty acid are predicted by an acidolysis reaction fatty acid balance model, wherein the acidolysis reaction fatty acid balance model is as follows:
in the reaction system, the content of triglyceride is m, the content of fatty acid is h, in the reaction process, the used lipase is sn-1,3 position specific lipase, and the fatty acid accords with random distribution on sn-1,3 positions. In the whole reaction system, the fatty acid types are defined as n, different fatty acids are defined as Xi, the amount of change of sn-2 fatty acid is small by controlling acyl transfer using reaction conditions, and therefore, the change of sn-2 fatty acid can be ignored. In the system, the fatty acids participating in the reaction are mainly triglyceride sn-1,3 fatty acids and added free fatty acids. For individual fatty acids Xi, the mole percentage of Xi fatty acids in the sn-1,3 position of the triglyceride can be expressed as Msn-1/-3XiThe mole percentage of free fatty acids Xi can be expressed as MXiThus, when the system reaches the reaction equilibrium, according to the random distribution principle, the sn-1,3 content (sn-1/3Xi) of the triglyceride at the reaction equilibrium of the Xi fatty acids can be expressed as:
Figure BDA0003189883580000041
due to the fact that
Figure BDA0003189883580000042
Therefore, the temperature of the molten metal is controlled,
Figure BDA0003189883580000043
the model can be further simplified as:
Figure BDA0003189883580000044
let h/m be S, i.e. the molar ratio of free fatty acids to triglycerides is S: 1, therefore, the sn-1,3 content of triglycerides (sn-1/3Xi) at the Xi fatty acid reaction equilibrium can be further simplified to:
Figure BDA0003189883580000045
according to the composition of each fatty acid at the sn-1 and 3 positions of the mixed oil, the theoretical content of different fatty acids at the sn-1 and 3 positions after the acidolysis is balanced can be calculated.
As a preferable embodiment of the method for producing structural lipids based on the composition of breast milk triglycerides of the present invention, wherein: obtaining the required vegetable oil fatty acid proportion within the fatty acid proportion range predicted by an acidolysis reaction fatty acid balance model, and realizing the vegetable oil fatty acid proportion by a fatty acid mixing model, wherein the fatty acid mixing model is as follows:
Figure BDA0003189883580000046
wherein, Y1Is the molar ratio of the individual fatty acids in the free fatty acids, X1In terms of the molar ratio of free fatty acids, YiRespectively the mole percentage of each fatty acid of the selected grease, XiThe molar ratio of the selected oil and fat.
The vegetable oil selected in the fatty acid mixing model is one or more of coconut oil, tea seed oil, sunflower seed oil, palm kernel oil, rapeseed oil, soybean oil and linseed oil;
as a preferable embodiment of the method for producing structural lipids based on the composition of breast milk triglycerides of the present invention, wherein: determining the proportion of fatty acids satisfying the composition of the breast milk triglyceride through an acidolysis reaction triglyceride balance model, wherein the acidolysis reaction triglyceride balance model is as follows:
in the whole reaction system, the content of triglyceride is m, the content of fatty acid is h, the types of fatty acid are n, and different fatty acids are Xi. For individual fatty acids Xi, the molar percentage of Xi in the sn-1,3 position of the triglyceride can be expressed as Msn-1/3XiThe mole percentage of Xi at sn-2 position can be expressed as Msn-2XiThe mole percentage of free fatty acids Xi may be expressed as MXiThus, when the system reaches equilibrium, the probability of three arbitrary fatty acids Xs, Xj and Xk at the triglyceride position can be expressed as follows according to the random distribution principle:
Figure BDA0003189883580000051
the model can be further simplified as:
Figure BDA0003189883580000052
let h/m be S, i.e. the molar ratio of free fatty acids to triglycerides is S: 1, therefore, the above model is further simplified to:
Figure BDA0003189883580000061
thus, after the acidolysis reaction has reached equilibrium, the ratio of triglyceride molecules contained is:
Figure BDA0003189883580000062
according to the invention, saturated fatty acid and saturated triglyceride are separated and removed by adopting a low-temperature procedure between two acidolysis reactions, so that free fatty acid in the system can be recycled, and meanwhile, the procedures of high-temperature deacidification are reduced, thus being beneficial to reducing the cost and reducing the generation of harmful substances; by establishing a sn-2 fatty acid mixed model, the composition of the sn-2 fatty acid of an intermediate product is adjusted before secondary acidolysis, so that the consistency of the sn-2 fatty acid of a final product and breast milk fat is ensured; by establishing an acidolysis reaction fatty acid and triglyceride balance model, the substrate ratio and free fatty acid composition which meet the requirements of the composition and distribution of the fatty acid of the breast milk and the composition range of the triglyceride under acidolysis balance are obtained, the purpose and controllability of substrate reaction condition screening are improved, and the method is favorable for obtaining products with higher similarity to breast milk fat.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below with reference to examples of the specification.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
The method for detecting C52 triglyceride is carried out according to the method in national food safety standard GB30604-2015 food nutrition enhancer 1,3 dioleate-2-palmitic acid triglyceride.
The compositions of the volumes of breast milk fat as given in the examples below include the compositions in tables 1 and 2.
TABLE 1 composition ranges of fatty acids, sn-2 fatty acids and sn-1,3 fatty acids of breast milk fat
Figure BDA0003189883580000071
Table 2 breast milk fat triglyceride composition (%)
TAG min max TAG min max
CaLaLa 0.02 1.33 MOL 1.27 16.19
MLaCa 0.00 0.94 LaOO 0.29 4.29
CaLaL 0.01 0.69 POLa 3.38 12.11
CaLaO 0.00 2.73 POL 15.17 31.32
LaLaM 0.05 2.05 PPL 1.45 7.12
LaLaO 0.07 3.74 MPO 0.61 3.35
CaPL 0.22 9.10 OOO 0.95 2.82
LLL 0.5 3.93 POO 5.69 30.42
LaOL 0.01 10.23 PPO 1.12 8.91
CaPO 1.12 10.00 SOO 0.04 4.13
OLL 0.81 13.79 POS 0.05 6.23
PLL 2.03 15.02 PPS 0.18 1.38
Example 1.
58-degree palm stearin is selected as a raw material, the palmitic acid content is 70.3%, the sn-2 palmitic acid content is 58.3%, and the fatty acid composition and distribution are shown in the following table. Palm stearin lacks linoleic acid, linolenic acid, and medium chain fatty acids in the total fatty acid composition compared to breast milk fat; palm stearin lacks medium chain fatty acids and linolenic acid in the sn-2 fatty acid composition; the sn-1,3 fatty acid has high palmitic acid content, lacks medium-carbon chain fatty acid, linoleic acid and linolenic acid, and simultaneously, the relative content of sn-2 palmitic acid of the palm stearin is far lower than that of breast milk fat. Therefore, the palm stearin can be subjected to acidolysis by selecting a proper proportion of mixed fatty acid to reduce the content of sn-1,3 palmitic acid, regulate the composition of other fatty acid, remove saturated fatty acid and saturated triglyceride in the mixed oil through low-temperature crystallization, regulate the sn-2 fatty acid composition of the oil through physical mixing of the oil and fat, and finally regulate the sn-1,3 fatty acid composition through proper acidolysis reaction of the mixed fatty acid, so that a structured lipid product with the fatty acid composition and distribution and the triglyceride composition consistent with breast milk fat can be finally obtained.
Therefore, in order to improve the structure of the palm stearin, firstly, rapeseed oil rich in oleic acid and soybean oil fatty acid rich in linoleic acid are selected as acyl donors, the ratio of the soybean oil to the rapeseed oil fatty acid is 1:3, the substrate ratio of the fatty acid to the palm stearin is 4:1(mol/mol), and the acidolysis reaction is carried out in a packed bed reactor by taking Lipozyme RM IM as a catalyst. Before the grease enters the packed bed reactor, firstly introducing nitrogen into the packed bed reactor, replacing air in the packed bed reactor with the nitrogen, mixing fatty acid with palm stearin, heating the mixed grease to 50 ℃, keeping the temperature for 40min to completely melt the mixed grease, then introducing the mixed grease into the packed bed reactor, keeping the temperature of the packed bed at 60 ℃, keeping the retention time of the grease in the packed bed at 2h, and obtaining an acidolysis product after the reaction is finished. After the reaction, possible impurities were removed by filtration or centrifugation, and the fatty acid composition and distribution of the obtained primary acid hydrolysis product were as shown in the following table.
TABLE 3 fatty acid composition and distribution of palm stearin and primary acidolysis product
Figure BDA0003189883580000081
The% sn-2PA represents the relative percentage content of sn-2 palmitic acid and is calculated by the formula: sn-2 palmitic acid/(3X Total palmitic acid). times.100%
As can be seen from the above table, after one-time acidolysis, the% sn-2PA of the acidolysis product is improved, but is not in the range of breast milk fat, and the content of palmitic acid is much higher than that of breast milk fat, so that the product needs to be subjected to secondary acidolysis. Separating and removing palmitic acid, tripalmitin and partial glyceride in the primary acidolysis product by using a low-temperature program, wherein the separation condition is that the oil is heated to 65 ℃ and maintained for 20min, the temperature is reduced to 35 ℃ at the speed of 4 ℃/h, crystal growth is carried out for 4h, the temperature is reduced to 18 ℃ at the speed of 8 ℃/h, crystal growth is carried out for 5h, the rotating speed is 30 r/min, and after the separation and crystallization are finished, saturated fatty acid and solid fat are filtered and separated to obtain liquid oil. The fatty acid composition and distribution of the liquid oil are shown in the table below.
TABLE 3 compositional characteristics of liquid oils after fractionation
Figure BDA0003189883580000091
Because partial saturated triglyceride and saturated fatty acid are removed at low temperature, the ratio of triglyceride to fatty acid in the system is changed, and the molar ratio of fatty acid to triglyceride in the system is 3.6:1.
compared with breast milk fat, the liquid oil sn-2 fatty acid lacks medium-carbon fatty acid, has higher oleic acid content and lower lauric acid content, so that in order to make the sn-2 fatty acid composition of the final product consistent with that of breast milk fat, partial vegetable oil needs to be added into the liquid oil to adjust the sn-2 fatty acid composition. Coconut oil rich in medium-chain fatty acids, soybean oil rich in linoleic acid, and linseed oil rich in linolenic acid were selected to mix with the liquid oil and to adjust its sn-2 fatty acid composition to be within the range of breast milk fat, the fatty acid composition and distribution of the selected oil are shown in the following table. And calculating the proportion of the vegetable oil required to be added into the liquid oil by establishing a sn-2 bit physical mixing model of the oil. Meanwhile, in order to ensure that the mixed oil has the highest sn-2 palmitic acid content, the amount of the vegetable oil and fat which are added externally is minimum.
According to the fatty acid composition and distribution of vegetable oil and the composition range of the sn-2 fatty acid of breast milk fat, a calculation model of the sn-2 fatty acid composition of the oil is established as follows:
Figure BDA0003189883580000092
wherein sn-2 FA% is sn-2 fatty acid composition of the mixed oil, Y represents different fatty acids, and Y represents1(sn-2)And Yi(sn-2)The mole percentage of each fatty acid on the sn-2 position of the palm stearin and the selected oil respectively, XiThe molar ratio of the selected grease to the palm stearin;
by setting XiAccording to the formula, the fatty acid composition and distribution in the mixed system can be calculated, an inequality is established according to the sn-2 fatty acid range of breast milk fat, and the addition range of each oil in the range is calculated.
During the mixing process, the sn-2 position of the triglyceride needs to contain more palmitic acid as much as possible, so that the nutritional value of the structural fat is ensured. Therefore, at the time of mixing, a minimum amount of exogenous plant oil is added while satisfying the fatty acid composition at the sn-2 site of breast milk fat. The addition amount of the exogenous vegetable oil is as follows:
Figure BDA0003189883580000101
Xithe molar ratio of the selected grease to the palm stearin; m is the sum of the proportion of the selected grease. In order to ensure the maximum sn-2 palmitic acid content of the mixed oil and fat, the minimum amount of exogenous oil and fat needs to be added on the basis of ensuring the sn-2 fatty acid in the fat range of breast milk, and Matlab R2010a (MathWorks, Natick, MA, USA) is adopted to optimize the addition ratio of the oil and fat.
The composition of the total fatty acids and sn-1,3 fatty acids is also obtained as follows.
Figure BDA0003189883580000102
Figure BDA0003189883580000103
Wherein FA% is fatty acid composition of mixed oil, sn-1,3 FA% is sn-1,3 fatty acid composition of mixed oil, and Y1And YiThe mole percentages of the respective fatty acids of the palm stearin and the selected oil are respectively.
TABLE 4 fatty acid composition and distribution of selected vegetable oils
Figure BDA0003189883580000104
Assuming that soybean oil is X1, coconut oil is X2, and linseed oil is X3, an inequality is established by a mixed model according to the composition of sn-2 fatty acid of breast milk as shown below.
Sn-2 C6:0 0.01≦0.57X2/(1+X1+X2+X3)≦0.11
sn-2C8:0 0.03≦1.43X2/(1+X1+X2+X3)≦1.08
sn-2C10:0 0.36≦3.46X2/(1+X1+X2+X3)≦1.62
sn-2C12:0 1.95≦76.42X2/(1+X1+X2+X3)≦13.69
sn-2C14:0 3.29≦(0.4+9.35X2)/(1+X1+X2+X3)≦18.55
sn-2C16:0 37.02≦(56.7+3.56X1+3.01X2+5.18X3)/(1+X1+X2+X3)≦66.33
sn-2C18:0 1.18≦(3.5+1.94X1+0.87X2+2.38X3)/(1+X1+X2+X3)≦3.43
sn-2C18:1 5.41≦(26.1+24.44X1+3.62X2+31.7X3)/(1+X1+X2+X3)≦23.27
sn-2C18:2 2.59≦(12.6+65.38X1+1.27X2+27.46X3)/(1+X1+X2+X3)≦17.4
sn-2C18:3 0.55≦(0.7+4.68X1+33.28X3)/(1+X1+X2+X3)≦2.78
M＝X1+X2+X3
By Matlab R2010 optimization calculations, the fatty acid composition and distribution of triglycerides in liquid oil is as follows, when the ratio of triglycerides to soybean oil, coconut oil and linseed oil in liquid oil is 1:0.02:0.15:0.01, the main fatty acid at sn-2 position in the product is within the range of breast milk fat, and the amount of exogenous oil added is the lowest.
TABLE 5 fatty acid composition and distribution of liquid oil triglycerides
General assembly sn-2 sn-1,3
C6:0 0.08 0.07 0.08
C8:0 0.73 0.18 1.00
C10:0 0.71 0.44 0.84
C12:0 5.99 9.71 4.13
C14:0 2.96 1.53 3.68
C16:0 37.76 48.54 32.37
C18:0 5.49 3.13 6.67
C18:1ω-9 27.87 23.26 30.18
C18:2ω-6 15.10 12.18 16.56
C18:3ω-3 3.32 0.95 4.50
After mixing, the molar ratio of fatty acids to triglycerides in the system was 3.6:1.18, i.e. 3: 1. The sn-2 fatty acid of the mixed fat is in the range of breast milk fat, but the sn-1,3 fatty acid composition is greatly different from that of breast milk fat, and it is predicted that the triglyceride is also greatly different from that of breast milk fat. Thus, by selecting an appropriate acyl donor, the sn-1,3 fatty acid composition of triglycerides is adjusted by means of a sn-1,3 lipase catalyzed acidolysis reaction. And establishing an acidolysis reaction fatty acid balance model according to the composition of the fatty acid at the sn-1 and 3 positions of the breast milk fat and the composition of the triglyceride, so as to predict the substrate ratio and the free fatty acid ratio which meet the composition of the fatty acid at the sn-1 and 3 positions of the breast milk fat and the composition of the triglyceride.
In the reaction system, the content of triglyceride is m, the content of fatty acid is h, in the reaction process, the used lipase is sn-1,3 position specific lipase, and the fatty acid accords with random distribution on sn-1,3 positions. In the whole reaction system, the fatty acid types are n, different fatty acids are defined as Xi, the acyl transfer is controlled by the reaction conditions, the variation of sn-2 fatty acid is small, and therefore, the variation of sn-2 fatty acid can be ignored. In the system, the fatty acids participating in the reaction are mainly triglyceride sn-1,3 fatty acids and added free fatty acids. For individual fatty acids Xi, the mole percentage of Xi fatty acids in the sn-1,3 position of the triglyceride can be expressed as Msn-1/-3XiThe mole percentage of free fatty acids Xi can be expressed as MXiThus, when the system reaches equilibrium, the sn-1,3 content (sn-1/3Xi) of the triglyceride at the equilibrium of the Xi fatty acid reaction can be expressed as:
Figure BDA0003189883580000121
due to the fact that
Figure BDA0003189883580000122
Therefore, the temperature of the molten metal is controlled,
Figure BDA0003189883580000123
the model can be further simplified as:
Figure BDA0003189883580000124
let h/m be S, i.e. the molar ratio of free fatty acids to triglycerides is S: 1, therefore, the sn-1,3 content of triglycerides (sn-1/3Xi) at the Xi fatty acid reaction equilibrium can be further simplified to:
Figure BDA0003189883580000125
according to the composition of each fatty acid at the sn-1 and 3 positions of the mixed oil, the theoretical content of different fatty acids at the sn-1 and 3 positions after the acidolysis is balanced can be calculated.
In order to further determine the composition of triglyceride in a system after reaction equilibrium, a triglyceride composition equilibrium model under an enzyme catalysis condition is established by utilizing a fatty acid random distribution theory: in the whole reaction system, the content of triglyceride is m, the content of fatty acid is h, the types of fatty acid are n, and different fatty acids are Xi. For individual fatty acids Xi, the molar percentage of Xi at the sn-1,3 position of the triglyceride may be expressed as Msn-1/3XiThe mole percentage of Xi at sn-2 position can be expressed as Msn-2XiThe mole percentage of free fatty acids Xi can be expressed as MXiThus, when the system reaches equilibrium, the probability of three arbitrary fatty acids Xs, Xj and Xk at the triglyceride position can be expressed as follows according to the random distribution principle:
Figure BDA0003189883580000131
the model can be further simplified as:
Figure BDA0003189883580000132
let h/m be S, i.e. the molar ratio of free fatty acids to triglycerides is S: 1, therefore, the above model is further simplified to:
Figure BDA0003189883580000133
thus, after the acidolysis reaction has reached equilibrium, the triglyceride molecules are contained in the following proportions:
Figure BDA0003189883580000134
the proportion of free fatty acids required to reach the sn-1,3 fatty acid range of breast milk fat under different substrate ratios can be calculated by an acidolysis reaction fatty acid equilibrium model as follows:
TABLE 6 theoretical values of the individual fatty acids required to reach the sn-1,3 fatty acid range of breast milk fat
Figure BDA0003189883580000135
Figure BDA0003189883580000141
From the above table, the proportion of free fatty acids required to meet the reference range of fatty acids in the sn-1,3 position of breast milk fat can be obtained as follows:
TABLE 7 proportions of the respective fatty acids required to satisfy the sn-1,3 fatty acid range of breast milk fat at different substrate ratios
Figure BDA0003189883580000142
Coconut oil fatty acid rich in medium-chain fatty acid, tea-seed oil fatty acid rich in oleic acid, sunflower seed oil fatty acid rich in linoleic acid and linseed oil fatty acid rich in linolenic acid are selected to be mixed with the mixed oil, the mixing proportion of the fatty acids is determined by establishing a fatty acid mixing model, and the fatty acid mixing model is shown as follows.
Figure BDA0003189883580000143
Wherein Y is1Is the molar ratio of the individual fatty acids in the free fatty acids, X1In terms of the molar ratio of free fatty acids, YiRespectively the mole percentage of each fatty acid of the selected grease, XiThe molar ratio of the selected oil and fat.
TABLE 8 composition of fatty acids of selected oils and fats
Figure BDA0003189883580000144
Figure BDA0003189883580000151
Setting the coconut oil fatty acid ratio as X1, the tea seed oil fatty acid ratio as X2, the sunflower seed oil fatty acid ratio as X3, the linseed oil fatty acid ratio as X4, and selecting fatty acids according to the ratio of the added fatty acids predicted by the model based on the range of the required fatty acids in different ratios: triglyceride is 8:1, and the inequality established is as follows:
sn-1,3C6:0 0.62X1/6≦0.21
sn-1,3C8:0 5.71X1/6≦1.54
sn-1,3C10:0 5.56X1/6≦4.14
sn-1,3C12:0 1.39≦47.12X1/6≦12.17
sn-1,3C14:0 3.93≦(0.4*3+19.30X1/6)≦8.09
sn-1,3C16:0 (6.3*3+9.92X1+5.72X2+6.53X3+5.32X4)/6≦7.73
sn-1,3C18:0 0.95≦(4.6*3+3X1+3.68X2+3.44X3+3.66X4)/6≦14.25
sn-1,3C18:1 30.76≦(54.5*3+7.03X1+68.71X2+31.25X3+19.45X4)/6≦58.38
sn-1,3C18:2 16.85≦(27.2*3+1.74X1+21.89X2+58.78X3+16.23X4)/6≦45.62
sn-1,3C18:3 0.29≦(6.8*3++54.30X4)/6≦2.74
by calculation, when the free fatty acid: coconut oil fatty acid: tea seed oil fatty acid: when the fatty acid of the sunflower seed oil is 3, (0.25-2), (0-4) and (0.75-3), the main fatty acid in the mixed fatty acid is within the range.
TABLE 9 composition ranges for fatty acids at different mixing ratios
Minimum value Maximum value
C6:0 0.02 0.16
C8:0 0.18 1.43
C10:0 0.17 1.39
C12:0 1.47 11.78
C14:0 0.75 4.98
C16:0 6.22 7.37
C18:0 3.77 3.98
C18:1ω-9 33.91 57.94
C18:2ω-6 26.71 32.68
C18:3ω-3 2.55 2.55
Through the above proportions, the composition of triglyceride in the product under different substrate ratios and different fatty acid ratios can be predicted and calculated by using an acidolysis reaction equilibrium model, so that the difference between the obtained product and breast milk fatty triglyceride can be predicted, and the substrate ratio and the fatty acid ratio in the reaction process are optimized.
According to the prediction model of triglyceride in acidolysis reaction, assuming that the molar content of free fatty acid Ca in the reaction system is X1, La is X2, M is X3, P is X4, S is X5, O is X6, L is X7 and the ratio of free fatty acid to triglyceride is S, based on the composition and distribution of triglyceride in liquid oil, the content of different fatty acids in triglyceride sn-1,3 and the composition of main triglyceride (without considering isomer) under the condition of different substrate ratios and different free fatty acid compositions after reaction equilibrium can be calculated.
TABLE 10 theoretical content of different fatty acids in sn-1,3
Fatty acids Abbreviations Ratio of sn-2 Sn-1/3
C12:0 Ca X1 0.44 (2*0.84+SX1)/(2+S)
C14:0 La X2 9.71 (2*4.13+SX2)/(2+S)
C16:0 M X3 1.53 (2*3.68+SX3)/(2+S)
C18:0 P X4 48.54 (2*32.37+SX4)/(2+S)
C18:1ω-9 S X5 3.13 (2*6.67+SX5)/(2+S)
C18:2ω-6 O X6 23.26 (2*30.18+SX6)/(2+S)
C12:0 L X7 12.18 (2*16.56+SX7)/(2+S)
TABLE 11 theoretical composition of triglycerides in the post reaction equilibrium system
Figure BDA0003189883580000161
Figure BDA0003189883580000171
Combining a fatty acid distribution and triglyceride composition model under an acidolysis balance condition, solving under the condition that the substrate ratio of fatty acid to triglyceride is 8:1 to obtain a fatty acid ratio which meets the requirements of main fatty acid distribution and triglyceride composition in the range of breast milk fat as free fatty acid: coconut oil fatty acid: tea seed oil fatty acid: the fatty acid composition of sunflower oil under these conditions is as follows:
TABLE 12 Mixed fatty acid composition in liquid oils
Fatty acids Maximum value
C6:0 0.08
C8:0 0.71
C10:0 0.70
C12:0 5.89
C14:0 2.56
C16:0 6.74
C18:0 3.88
C18:1ω-9 46.31
C18:2ω-6 30.59
C18:3ω-3 2.55
Under the condition, the main triglyceride in the reaction system is predicted to be in the range of breast milk fat by a triglyceride balance model in acidolysis balance, and the theoretical value is as follows:
TABLE 13 predicted composition of product triglycerides at acidolysis equilibrium
TAG min max Content (wt.) TAG min max Content (c) of
CaLaLa 0.02 1.33 0.03 MOL 1.27 16.19 1.32
MLaCa 0.00 0.94 0.01 LaOO 0.29 4.29 2.91
CaLaL 0.01 0.69 0.05 POLa 3.38 12.11 3.61
CaLaO 0.00 2.73 0.10 POL 15.17 31.32 14.40
LaLaM 0.05 2.05 0.07 PPL 1.45 7.12 3.37
LaLaO 0.07 3.74 0.53 MPO 0.61 3.35 1.48
CaPL 0.22 9.10 0.25 OOO 0.95 2.82 4.32
LLL 0.5 3.93 0.94 POO 5.69 30.42 11.39
LaOL 0.01 10.23 3.62 PPO 1.12 8.91 5.29
CaPO 1.12 10.00 1.39 SOO 0.04 4.13 1.47
OLL 0.81 13.79 8.84 POS 0.05 6.23 2.42
PLL 2.03 15.02 4.55 PPS 0.18 1.38 0.56
Therefore, the substrate ratio and the fatty acid composition are selected to carry out acidolysis reaction, the oil is heated to 50 ℃ and kept for 40min, then the oil is introduced into a packed bed reactor, the temperature of the packed bed is kept at 50 ℃, the retention time of the oil in the packed bed is 4h, after the reaction is finished, possible impurities are removed through filtration or centrifugation, and free fatty acid is removed through reduced pressure distillation, so that a final product is obtained.
TABLE 14 fatty acid composition and distribution of final product
Figure BDA0003189883580000181
Figure BDA0003189883580000191
TABLE 15 triglyceride composition of the final product
TAG Content (c) of TAG Content (wt.)
CaLaLa 0.02 MOL 1.12
MLaCa 0.01 LaOO 3.00
CaLaL 0.05 POLa 3.29
CaLaO 0.09 POL 15.90
LaLaM 0.06 PPL 2.76
LaLaO 0.50 MPO 1.38
CaPL 0.22 OOO 5.09
LLL 1.24 POO 11.57
LaOL 3.82 PPO 4.27
CaPO 0.35 SOO 1.46
OLL 10.95 POS 2.05
PLL 4.80 PPS 0.37
C52 34.32
The obtained product is evaluated through a similarity evaluation model, and the calculation formula of the evaluation model is as follows:
Figure BDA0003189883580000192
Figure BDA0003189883580000193
Figure BDA0003189883580000194
wherein G isFA/sn-2FA/TAGSimilarity of the breast milk substitute fat to human milk fat in terms of fatty acid composition, sn-2 fatty acid relative content or triglyceride composition; ei(FA/sn-2FA/TAG)Is the similarity that the fatty acid composition, the sn-2 fatty acid relative content or the triglyceride composition in the breast milk substitute fat are deducted outside the corresponding index content range of the breast milk fat respectively;
Figure BDA0003189883580000201
is the relative value of the fatty acid, sn-2 fatty acid or triglyceride composition of breast milk fat and the total content thereof; ci(FA/sn-2FA/TAG)Is the coefficient of variation, which depends on the total fatty acid content, the relative content of sn-2 fatty acids or the triglyceride composition of the breast milk substitute fat; bi(FA/sn-2FA/TAG)Is the total fatty acid content, the sn-2 relative fatty acid content or the triglyceride content of the breast milk substitute fat; a. thei(FA/sn-2FA/TAG)Is the total fatty acid, sn-2 relative fatty acid content or triglyceride composition of the corresponding breast milk fat; when B is higher than A, A selects the upper limit; when B is smaller than A, A selects a lower limit; if B is within the range of A, C is 0.
Similarity between the obtained mixed oil and the ester exchange product and the human milk fat in the composition of fatty acid, sn-2 fatty acid and triglyceride is shown in the following table through similarity model evaluation:
TABLE 16 similarity of product to breast milk fat
Degree of similarity (%) Acid hydrolysis product
GFA 100
Gsn-2FA 96.4
GTAG 90.1
By comparing the similarity between the acidolysis product and the breast milk fat by using an evaluation model, the obtained product has the fatty acid composition and distribution consistent with those of the breast milk fat, and is also highly similar to the breast milk fat in triglyceride composition.
Example 2
The 52-degree palm stearin extract is selected as a raw material, the palmitic acid content is 82.4%, the sn-2 palmitic acid content is 75.5%, and the fatty acid composition and distribution are shown in the following table. Compared with breast milk fat, in the total fatty acid composition, the palm stearin is lack of linoleic acid, linolenic acid and medium-carbon chain fatty acid, in the sn-2 fatty acid composition, the palm stearin is lack of medium-chain fatty acid and linolenic acid, in the sn-1,3 fatty acid, the palmitic acid content is higher, and the medium-carbon chain fatty acid, linoleic acid and linolenic acid are lack, and meanwhile, the relative content of the sn-2 palmitic acid of the palm stearin is far lower than that of the breast milk fat. Therefore, the palm stearin can be subjected to acidolysis by selecting a proper proportion of mixed fatty acid to reduce the content of sn-1,3 palmitic acid, regulate the composition of other fatty acid, remove saturated fatty acid and saturated triglyceride in the mixed oil through low-temperature crystallization, regulate the sn-2 fatty acid composition of the oil through physical mixing of the oil and fat, and finally regulate the sn-1,3 fatty acid composition through proper acidolysis reaction of the mixed fatty acid, so that a structured lipid product with the fatty acid composition and distribution and the triglyceride composition consistent with breast milk fat can be finally obtained.
Therefore, in order to improve the structure of the palm stearin, firstly, tea seed oil rich in oleic acid and sunflower seed fatty acid rich in linoleic acid are selected as acyl donors, the ratio of the tea seed oil to the sunflower seed fatty acid is 2:1, the substrate ratio of the fatty acid to the palm stearin is 6:1(mol/mol), and NS40086 is used as a catalyst to carry out acidolysis reaction in a packed bed reactor. Before the grease enters the packed bed reactor, firstly introducing nitrogen into the packed bed reactor, replacing air in the packed bed reactor with nitrogen, mixing fatty acid with palm stearin, heating the mixed grease to 55 ℃, keeping the temperature for 30min to completely melt the mixed grease, then introducing the mixed grease into the packed bed reactor, keeping the temperature of the packed bed at 50 ℃, keeping the retention time of the grease in the packed bed at 5h, and obtaining an acidolysis product after the reaction is finished. After the reaction, possible impurities were removed by filtration or centrifugation, and the fatty acid composition and distribution of the obtained primary acid hydrolysis product were as shown in the following table.
TABLE 17 fatty acid composition and distribution of palm stearin and primary acidolysis product
Figure BDA0003189883580000211
As can be seen from the above table, after one-time acidolysis, the% sn-2PA of the acidolysis product is improved, but is not in the range of breast milk fat, and the content of palmitic acid is much higher than that of breast milk fat, so that the product needs to be subjected to secondary acidolysis. Separating and removing palmitic acid, tripalmitin and partial glyceride in the primary acidolysis product by using a low-temperature program, wherein the separation condition is that the oil is heated to 60 ℃ and maintained for 25min, the temperature is reduced to 40 ℃ at the speed of 10 ℃/h, crystal growth is carried out for 3h, the temperature is reduced to 24 ℃ at the speed of 3 ℃/h, crystal growth is carried out for 8h, the rotating speed is 40 rpm, and after the separation and crystallization are finished, saturated fatty acid and solid fat are filtered and separated to obtain liquid oil. The fatty acid composition and distribution of the liquid oil are shown in the table below.
TABLE 18 compositional characteristics of liquid oils after fractionation
Figure BDA0003189883580000212
Figure BDA0003189883580000221
Because partial saturated triglyceride and saturated fatty acid are removed at low temperature, the ratio of triglyceride to fatty acid in the system is changed, and the molar ratio of fatty acid to triglyceride in the system is 5.7: 1.
compared with breast milk fat, the liquid oil sn-2 fatty acid is lack of medium carbon chain fatty acid and linolenic acid, so in order to make the final product consistent with the breast milk fat in terms of sn-2 fatty acid composition, partial vegetable oil needs to be added to adjust the sn-2 fatty acid composition. Selecting palm kernel oil rich in medium-chain fatty acid and linseed oil rich in linolenic acid to blend the palm kernel oil and the linseed oil, selecting tea seed oil rich in oleic acid and sunflower seed oil rich in linoleic acid to mix liquid oil, and adjusting the sn-2 fatty acid composition of the liquid oil to be within the range of breast milk fat. And calculating the proportion of the vegetable oil required to be added into the liquid oil by establishing a sn-2 bit physical mixing model of the oil. Meanwhile, in order to ensure that the mixed oil has the highest sn-2 palmitic acid content, the amount of the vegetable oil and fat which are added externally is minimum. The fatty acid composition and distribution of the selected vegetable oils are as follows:
TABLE 19 fatty acid composition and distribution of selected vegetable oils
Figure BDA0003189883580000222
The method comprises the steps of setting sunflower seed oil as X1, palm kernel oil as X2, linseed oil as X3 and tea seed oil as X4, and establishing an inequality through a mixing model according to the composition of sn-2 fatty acid of breast milk as shown in the following.
Sn-2 C6:0 0.01≦0.05X2/(1+X1+X2+X3+X4)≦0.11
sn-2C8:0 0.03≦1.78X2/(1+X1+X2+X3+X4)≦1.08
sn-2C10:0 0.36≦2.89X2/(1+X1+X2+X3+X4)≦1.62
sn-2C12:0 1.95≦61.38X2/(1+X1+X2+X3+X4)≦13.69
sn-2C14:0 3.29≦(0.5+18.98X2)/(1+X1+X2+X3+X4)≦18.55
sn-2C16:0 37.02≦(73.4+4.62X1+4.65X2+5.18X3+5.18X4)/(1+X1+X2+X3+X4)≦66.33
sn-2C18:0 1.18≦(2.4+2.24X1+0.84X2+2.38X3+2.11X4)/(1+X1+X2+X3+X4)≦3.43
sn-2C18:1 5.41≦(17.7+22.8X1+7.51X2+31.7X3+52.62X4)/(1+X1+X2+X3+X4)≦23.27
sn-2C18:2 2.59≦(6+70.16X1+1.92X2+27.46X3+40.06X4)/(1+X1+X2+X3+X4)≦17.4
sn-2C18:3 0.55≦(33.28X3)/(1+X1+X2+X3+X4)≦2.78
M＝X1+X2+X3+X4
In order to ensure that the mixed oil has the maximum sn-2 palmitic acid content, Matlab R2010a (MathWorks, Natick, MA, USA) is adopted to optimize the adding proportion of the oil, on the basis of ensuring the sn-2 fatty acid in the fat range of breast milk, the minimum exogenous oil is added,
it was calculated that when the ratio of triglyceride in the liquid oil to palm kernel oil and linseed oil was 1:0.1:0.025, the major fatty acid at sn-2 position in the product was within the range of breast milk fat, and the amount of exogenous oil added was the lowest, under which conditions the fatty acid composition and distribution of triglyceride in the liquid oil were as follows.
TABLE 20 fatty acid composition and distribution of mixed oil triglycerides
General assembly sn-2 sn-1,3
C6:0 0.02 0.01 0.02
C8:0 0.27 0.16 0.32
C10:0 0.28 0.26 0.29
C12:0 4.19 5.46 3.56
C14:0 2.02 2.12 1.96
C16:0 40.61 65.77 28.02
C18:0 3.43 2.26 4.01
C18:1ω-9 31.42 17.11 38.58
C18:2ω-6 16.50 6.11 21.69
C18:3ω-3 1.21 0.74 1.44
After mixing, the molar ratio of fatty acids to triglycerides in the system was 5.7: 1.125, i.e. 5: 1. The main fatty acid at the sn-2 position of the mixed fat is in the range of breast milk fat, but the difference between the sn-1 and sn-3 fatty acid compositions and breast milk fat is large, and it is predicted that the difference between the triglyceride and breast milk fat is also large. Thus, by selecting an appropriate acyl donor, the sn-1,3 fatty acid composition of triglycerides is adjusted by means of a sn-1,3 lipase catalyzed acidolysis reaction. And establishing an acidolysis reaction fatty acid balance model according to the composition of the sn-1 and 3 site fatty acids and the composition of the triglyceride of the breast milk fat, so as to predict a substrate ratio and a free fatty acid ratio which meet the composition of the sn-1 and 3 site fatty acids and the composition of the triglyceride of the breast milk fat.
The proportion of free fatty acids required to reach the sn-1,3 fatty acid range of breast milk fat under different substrate ratios can be calculated by an acidolysis reaction fatty acid equilibrium model as follows:
TABLE 20 proportions of the respective fatty acids required to reach the sn-1,3 fatty acid range of the maternal milk fat at different substrate ratios
Figure BDA0003189883580000241
Mixing palm kernel oil fatty acid rich in medium-carbon chain fatty acid, rapeseed oil fatty acid rich in oleic acid, soybean oil fatty acid rich in linoleic acid and linseed oil fatty acid rich in linolenic acid with the mixed oil, wherein the mixing proportion of the fatty acids is determined by establishing a fatty acid mixing model.
TABLE 20 fatty acid composition of selected oils and fats
Fatty acids Palm kernel oil Rapeseed oil Soybean oil Linseed oil
X1 X2 X3 X4
C6:0 0.20
C8:0 2.99
C10:0 3.17
C12:0 47.14
C14:0 16.39
C16:0 8.83 4.45 8.99 5.32
C18:0 2.29 1.76 4.60 3.66
C18:1ω-9 16.25 64.61 23.52 19.45
C18:2ω-6 2.71 21.09 56.02 16.23
C18:3ω-3 8.10 6.86 54.30
Setting the fatty acid ratio of palm kernel oil as X1, the fatty acid ratio of rapeseed oil as X2, the fatty acid ratio of soybean oil as X3, the fatty acid ratio of linseed oil as X4, and selecting the fatty acids according to the ratio of the added fatty acids predicted by the model based on the range of the required fatty acids in different ratios: triglyceride is 6:1, and the inequality established is as follows:
sn-1,3C6:0 0.01≦0.2X1/6≦0.23
sn-1,3C8:0 2.99X1/6≦1.80
sn-1,3C10:0 0.05≦3.17X1/6≦4.54
sn-1,3C12:0 1.4≦47.14X1/6≦12.89
sn-1,3C14:0 4.52≦(0.1*5+16.39X1/6)≦8.96
sn-1,3C16:0 (7.4*5+8.83X1+4.45X2+8.99X3+5.32X4)/6≦7.54
sn-1,3C18:0 1.45≦(4.3*5+2.29X1+1.76X2+4.60X3+3.66X4)/6≦15.64
sn-1,3C18:1 27.99≦(55.6*5+16.25X1+64.61X2+23.52X3+19.45X4)/6≦57.46
sn-1,3C18:2 15.16≦(32.5*5+2.71X1+21.09X2+56.02X3+16.23X4)/6≦45.85
sn-1,3C18:3 1.03≦(8.10X2+6.86X3+54.30X4)/6≦2.92
by calculation, when the free fatty acid: palm kernel oil fatty acids: rapeseed oil fatty acid: soybean oil fatty acid: when the linseed oil fatty acid is 5 (0.2-0.7): (0.1-0.35): (0.1-0.35) (0.1-0.2), the main fatty acid in the mixed fatty acid is in the range.
TABLE 21 ranges of Mixed fatty acids
Fatty acids Minimum value Maximum value
C6:0 0.01 0.02
C8:0 0.10 0.35
C10:0 0.11 0.37
C12:0 1.57 5.50
C14:0 0.63 2.00
C16:0 7.51 7.33
C18:0 4.02 4.09
C18:1ω-9 50.02 52.34
C18:2ω-6 28.96 31.94
C18:3ω-3 1.15 1.78
Based on the composition and distribution of triglycerides in the liquid oil, the content of different fatty acids in triglycerides sn-1,3 and the composition of the major triglycerides can be calculated after the equilibrium of the reaction under conditions of 6:1 (fatty acids/triglycerides) as substrate and different free fatty acid compositions according to the acidolysis reaction triglyceride prediction model. Combining a fatty acid distribution and triglyceride composition model under an acidolysis balance condition, solving under the condition that the substrate ratio of fatty acid to triglyceride is 6:1 to obtain a fatty acid ratio which meets the main fatty acid distribution and triglyceride composition within the breast milk fat range as free fatty acid: palm kernel oil fatty acids: rapeseed oil fatty acid: soybean oil fatty acid: linseed oil fatty acid composition is 5:0.5:0.2:0.2:0.1, under which conditions the fatty acid composition in liquid oil is as follows:
TABLE 22 fatty acid composition
Figure BDA0003189883580000251
Figure BDA0003189883580000261
Under the condition, when in acidolysis balance, the main triglyceride in the reaction system is predicted to be in the range of breast milk fat by a triglyceride balance model, and the theoretical value is as follows:
TABLE 23 predicted composition of product triglycerides at acidolysis equilibrium
TAG min max Content (wt.) TAG min max Content (wt.)
CaLaLa 0.02 1.33 0.01 MOL 1.27 16.19 0.81
MLaCa 0.00 0.94 0.01 LaOO 0.29 4.29 1.88
CaLaL 0.01 0.69 0.01 POLa 3.38 12.11 3.42
CaLaO 0.00 2.73 0.03 POL 15.17 31.32 19.59
LaLaM 0.05 2.05 0.01 PPL 1.45 7.12 4.74
LaLaO 0.07 3.74 0.23 MPO 0.61 3.35 1.32
CaPL 0.22 9.10 0.12 OOO 0.95 2.82 3.92
LLL 0.5 3.93 0.54 POO 5.69 30.42 17.12
LaOL 0.01 10.23 2.06 PPO 1.12 8.91 8.19
CaPO 1.12 10.00 0.21 SOO 0.04 4.13 1.18
OLL 0.81 13.79 6.72 POS 0.05 6.23 2.99
PLL 2.03 15.02 5.60 PPS 0.18 1.38 0.70
Therefore, the substrate ratio and the fatty acid composition are selected to carry out acidolysis reaction, the oil is heated to 55 ℃ and kept for 30min, and then the oil is introduced into a packed bed reactor, the temperature of the packed bed is kept at 55 ℃, and the retention time of the oil in the packed bed is 3 h. After the reaction is finished, possible impurities are removed through filtration or centrifugation, and free fatty acid is removed through reduced pressure distillation, so that a final product is obtained.
TABLE 24 fatty acid composition and distribution of final product
Figure BDA0003189883580000262
Figure BDA0003189883580000271
TABLE 25 triglyceride composition of the final product
TAG Content (wt.) TAG Content (wt.)
CaLaLa 0.01 MOL 0.82
MlaCa 0.01 LaOO 2.04
CaLaL 0.01 POLa 2.98
CaLaO 0.03 POL 20.12
LaLaM 0.01 PPL 3.38
LaLaO 0.23 MPO 1.11
CaPL 0.11 OOO 4.91
LLL 0.76 POO 17.08
LaOL 2.31 PPO 5.70
CaPO 0.19 SOO 1.32
OLL 9.14 POS 2.82
PLL 5.92 PPS 0.47
C52 45.94
Through similarity model evaluation, the similarity of the obtained final product to human milk fat in the composition of fatty acid, sn-2 fatty acid and triglyceride is shown in the following table:
TABLE 26 similarity of product to breast milk fat
Degree of similarity (%) Final product
GFA 99.2
Gsn-2FA 95.3
GTAG 92.7
By comparing the similarity between the acidolysis product and the breast milk fat by using an evaluation model, the obtained product has the fatty acid composition and distribution consistent with those of the breast milk fat, and is also highly similar to the breast milk fat in triglyceride composition.
Example 3
The 58-degree palm stearin extract is selected as a raw material, the palmitic acid content is 91.2%, the sn-2 palmitic acid content is 84.3%, and the fatty acid composition and distribution are shown in the following table. Compared with breast milk fat, in the total fatty acid composition, the palm stearin is lack of oleic acid, linoleic acid, linolenic acid and medium-carbon chain fatty acid, in the sn-2 fatty acid composition, the palm stearin is lack of medium-chain fatty acid, linoleic acid and linolenic acid, in the sn-1,3 fatty acid, the palmitic acid content is higher, and the medium-carbon chain fatty acid, oleic acid, linoleic acid and linolenic acid are lack, and meanwhile, the relative content of the sn-2 palmitic acid of the palm stearin is far lower than that of the breast milk fat. Therefore, the palm stearin can be subjected to acidolysis by selecting a proper proportion of mixed fatty acid to reduce the content of sn-1,3 palmitic acid, regulate the composition of other fatty acid, remove saturated fatty acid and saturated triglyceride in the mixed oil through low-temperature crystallization, regulate the sn-2 fatty acid composition of the oil through physical mixing of the oil and fat, and finally regulate the sn-1,3 fatty acid composition through proper acidolysis reaction of the mixed fatty acid, so that a structured lipid product with the fatty acid composition and distribution and the triglyceride composition consistent with breast milk fat can be finally obtained.
Therefore, in order to improve the structure of the palm stearin, firstly rapeseed oil rich in oleic acid and sunflower oil fatty acid rich in linoleic acid are selected as acyl donors, the ratio of the sunflower oil to the rapeseed oil fatty acid is 1:1, the substrate ratio of the fatty acid to the palm stearin is 8:1(mol/mol), and an acidolysis reaction is carried out in a packed bed reactor by taking lipase DF as a catalyst. Before the grease enters the packed bed reactor, firstly introducing nitrogen into the packed bed reactor, replacing air in the packed bed reactor with the nitrogen, mixing fatty acid with palm stearin, heating the mixed grease to 60 ℃, keeping the temperature for 20min to completely melt the mixed grease, then introducing the mixed grease into the packed bed reactor, keeping the temperature of the packed bed at 55 ℃, keeping the retention time of the grease in the packed bed at 3h, and obtaining an acidolysis product after the reaction is finished. After the reaction, possible impurities were removed by filtration or centrifugation, and the fatty acid composition and distribution of the obtained primary acid hydrolysis product were as shown in the following table.
TABLE 27 fatty acid composition and distribution of palm stearin and primary acidolysis product
Figure BDA0003189883580000281
As can be seen from the above table, after one-time acidolysis, the% sn-2PA of the acidolysis product is improved, but is not in the range of breast milk fat, and the content of palmitic acid is much higher than that of breast milk fat, so that the product needs to be subjected to secondary acidolysis. Separating and removing palmitic acid, tripalmitin and partial glyceride in the primary acidolysis product by using a low-temperature program, wherein the separation condition is that the oil is heated to 55 ℃ and maintained for 30min, the temperature is reduced to 37 ℃ at the speed of 8 ℃ per hour, crystal growth is carried out for 5h, the temperature is reduced to 28 ℃ at the speed of 5 ℃ per hour, crystal growth is carried out for 2h at the rotating speed of 50 r/min, and after the separation and crystallization are finished, saturated fatty acid and solid fat are filtered and separated to obtain liquid oil. The fatty acid composition and distribution of the liquid oil are shown in the table below.
TABLE 28 compositional characteristics of liquid oils after fractionation
Figure BDA0003189883580000291
Because partial saturated triglyceride and saturated fatty acid are removed at low temperature, the ratio of triglyceride to fatty acid in the system is changed, and the molar ratio of fatty acid to triglyceride in the system is 8.8: 1.
compared with human milk fat, the sn-2 fatty acid of liquid oil is lack of medium-chain fatty acid and linolenic acid. Therefore, in order to make the final product conform to breast milk fat in terms of sn-2 fatty acid composition, it is necessary to add a portion of vegetable oil thereto, which is adjusted in its sn-2 fatty acid composition. Coconut oil rich in medium-chain fatty acid and linseed oil rich in linolenic acid are selected to be mixed with liquid oil, and the sn-2 fatty acid composition of the coconut oil and the linseed oil is adjusted to be within the range of breast milk fat. And calculating the proportion of the vegetable oil required to be added into the liquid oil by establishing a sn-2 bit physical mixing model of the oil. Meanwhile, in order to ensure that the mixed oil has the highest sn-2 palmitic acid content, the amount of the vegetable oil and fat which are added externally is minimum.
The coconut oil was set to X1 and linseed oil was set to X2, and the inequality was established by a mixed model according to the composition of the fatty acid of breast milk sn-2, as shown below.
Sn-2 C6:0 0.01≦0.57X1/(1+X1+X2)≦0.11
sn-2C8:0 0.03≦1.43X1/(1+X1+X2)≦1.08
sn-2C10:0 0.36≦3.46X1/(1+X1+X2)≦1.62
sn-2C12:0 1.95≦76.42X1/(1+X1+X2)≦13.69
sn-2C14:0 3.29≦(0.4+9.35X1)/(1+X1+X2)≦18.55
sn-2C16:0 37.02≦(42.4+3.01X1+5.18X2)/(1+X1+X2)≦66.33
sn-2C18:0 1.18≦(2.3+0.87X1+2.38X2)/(1+X1+X2)≦3.43
sn-2C18:1 5.41≦(28.7+3.62X1+31.7X2)/(1+X1+X2)≦23.27
sn-2C18:2 2.59≦(24.4+1.27X1+27.46X2)/(1+X1+X2)≦17.4
sn-2C18:3 0.55≦(1.9+33.28X2)/(1+X1+X2)≦2.78
M＝X1+X2
In order to ensure that the mixed oil has the maximum sn-2 palmitic acid content, Matlab R2010a (MathWorks, Natick, MA, USA) is adopted to optimize the adding proportion of the oil, on the basis of ensuring the sn-2 fatty acid in the fat range of breast milk, the minimum exogenous oil is added,
it was calculated that when the ratio of triglycerides to coconut oil and linseed oil in the liquid oil was 1:0.2:0.02, the major fatty acid at sn-2 position in the product was within the range of breast milk fat, and the amount of exogenous oil added was the lowest, under which conditions the fatty acid composition and distribution of triglycerides in the liquid oil were as follows.
TABLE 29 fatty acid composition and distribution of mixed oil triglycerides
General assembly sn-2 sn-1,3
C6:0 0.10 0.09 0.11
C8:0 0.94 0.23 1.29
C10:0 0.91 0.57 1.08
C12:0 7.72 12.53 5.32
C14:0 3.47 1.94 4.23
C16:0 36.44 67.22 21.05
C18:0 2.41 2.97 2.13
C18:1ω-9 24.97 9.31 32.81
C18:2ω-6 20.56 4.26 28.71
C18:3ω-3 2.42 0.87 3.19
After mixing, the molar ratio of fatty acids to triglycerides in the system was 8.8: 1.22, i.e. 7.21: 1. The main fatty acid at the sn-2 position of the mixed fat is in the range of breast milk fat, but the difference between the sn-1 and sn-3 fatty acid compositions and breast milk fat is large, and it is predicted that the difference between the triglyceride and breast milk fat is also large. Thus, by selecting an appropriate acyl donor, the sn-1,3 fatty acid composition of triglycerides is adjusted by means of a sn-1,3 lipase catalyzed acidolysis reaction. And establishing an acidolysis reaction equilibrium model according to the fatty acid composition and triglyceride composition of the sn-1 and 3 site of the breast milk fat, so as to predict a substrate ratio and a free fatty acid ratio which meet the requirements of the sn-1 and 3 site fatty acid composition and triglyceride composition of the breast milk fat.
The proportion of free fatty acids required to reach the sn-1,3 fatty acid range of breast milk fat under different substrate ratios can be calculated by an acidolysis reaction fatty acid equilibrium model as follows:
TABLE 30 proportions of the respective fatty acids required to reach the sn-1,3 fatty acid range of the maternal milk fat at different substrate ratios
Figure BDA0003189883580000301
Figure BDA0003189883580000311
Coconut oil fatty acid rich in medium-chain fatty acid, tea seed oil fatty acid rich in oleic acid, sunflower seed oil fatty acid rich in linoleic acid and linseed oil fatty acid rich in linolenic acid are selected to be mixed with the mixed oil, and the mixing proportion of the fatty acids is determined by establishing a fatty acid mixing model. The fatty acid composition of the selected oils and fats is as follows:
TABLE 31 fatty acid composition of selected oils and fats
Fatty acids Coconut oil Tea seed oil Sunflower seed oil Linseed oil
X1 X2 X3 X4
C6:0 0.62
C8:0 5.71
C10:0 5.56
C12:0 47.12
C14:0 0.2 19.3
C16:0 7.1 9.92 5.72 6.53 5.32
C18:0 2.0 3 3.68 3.44 3.66
C18:1ω-9 41.0 7.03 68.71 31.25 19.45
C18:2ω-6 44.3 1.74 21.89 58.78 16.23
C18:3ω-3 5.5 54.30
Setting the coconut oil fatty acid ratio as X1, the tea seed oil fatty acid ratio as X2, the sunflower oil fatty acid ratio as X3, the linseed oil fatty acid ratio as X4, and selecting the fatty acids according to the required fatty acid range predicted by the model and the fatty acid addition ratio predicted by the model based on the required fatty acid range in different ratios: triglyceride is 8:1, and the inequality established is as follows:
sn-1,3C6:0 0.62X1/8≦0.2
sn-1,3C8:0 5.71X1/8≦1.47
sn-1,3C10:0 5.56X1/8≦4.08
sn-1,3C12:0 1.1≦47.12X1/8≦11.87
sn-1,3C14:0 3.79≦(0.2*7.21+19.3X1)/8≦7.96
sn-1,3C16:0 (7.1*7.21+9.92X1+5.72X2+6.53X3+5.32X4)/8≦10.56
sn-1,3C18:0 2.08≦(2*7.21+3X1+3.68X2+3.44X3+3.66X4)/8≦15.38
sn-1,3C18:1 30.1≦(41*7.21+7.03X1+68.71X2+31.25X3+19.45X4)/8≦57.72
sn-1,3C18:2 13.81≦(44.3*7.21+1.74X1+21.89X2+58.78X3+16.23X4)/8≦42.59
sn-1,3C18:3 0.62≦(5.5*7.21+54.30X4)/8≦2.74
by calculation, when the free fatty acid: coconut oil fatty acid: tea seed oil fatty acid: when the fatty acid of the sunflower seed oil is 7.21 (0.2-0.7) to 0.05-0.2 (0.05-0.34), the main fatty acid in the mixed fatty acid is in the range.
TABLE 32 range of Mixed fatty acids
Fatty acids Minimum value Maximum value
C6:0 0.05 0.02
C8:0 0.50 0.14
C10:0 0.49 0.14
C12:0 4.12 1.18
C14:0 1.87 0.66
C16:0 7.34 7.10
C18:0 2.11 2.14
C18:1ω-9 38.15 40.60
C18:2ω-6 40.51 43.15
C18:3ω-3 4.96 4.96
Based on the composition and distribution of triglycerides in the liquid oil, the content of different fatty acids in the triglycerides sn-1,3 and the composition of the main triglycerides can be calculated after the equilibrium of the reaction under conditions of 8:1 (fatty acids/triglycerides) as substrate and different free fatty acid composition according to the acidolysis reaction triglyceride prediction model. Combining a fatty acid distribution and triglyceride composition model under an acidolysis balance condition, solving under the condition that the substrate ratio of fatty acid to triglyceride is 8:1 to obtain a fatty acid ratio which meets the requirements of main fatty acid distribution and triglyceride composition in the range of breast milk fat as free fatty acid: coconut oil fatty acid: tea seed oil fatty acid: the fatty acid composition of the sunflower oil is 7.21:0.5:0.15:0.14, and under the condition, the fatty acid composition of the liquid oil is as follows:
TABLE 33 fatty acid composition
Fatty acids Content (wt.)
C6:0 0.04
C8:0 0.36
C10:0 0.35
C12:0 2.95
C14:0 1.39
C16:0 7.24
C18:0 2.12
C18:1ω-9 39.23
C18:2ω-6 41.47
C18:3ω-3 4.96
Under the condition, the main triglyceride in the reaction system is predicted to be in the range of breast milk fat by a triglyceride balance model in acidolysis balance, and the theoretical value is as follows:
TABLE 34 predicted composition of product triglycerides at acidolysis equilibrium
TAG min max Content (wt.) TAG min max Content (wt.)
CaLaLa 0.02 1.33 0.01 MOL 1.27 16.19 0.78
MLaCa 0.00 0.94 0.00 LaOO 0.29 4.29 2.02
CaLaL 0.01 0.69 0.07 POLa 3.38 12.11 2.87
CaLaO 0.00 2.73 0.07 POL 15.17 31.32 20.47
LaLaM 0.05 2.05 0.02 PPL 1.45 7.12 5.55
LaLaO 0.07 3.74 0.35 MPO 0.61 3.35 1.26
CaPL 0.22 9.10 0.32 OOO 0.95 2.82 1.32
LLL 0.5 3.93 0.62 POO 5.69 30.42 10.26
LaOL 0.01 10.23 3.97 PPO 1.12 8.91 5.51
CaPO 1.12 10.00 0.32 SOO 0.04 4.13 0.57
OLL 0.81 13.79 2.52 POS 0.05 6.23 1.35
PLL 2.03 15.02 10.20 PPS 0.18 1.38 0.34
Therefore, the substrate ratio and the fatty acid composition are selected to carry out acidolysis reaction, the oil is heated to 60 ℃, the temperature is maintained for 20min, then the oil is introduced into a packed bed reactor, the temperature of the packed bed is maintained at 60 ℃, the retention time of the oil in the packed bed is 2h, after the reaction is finished, possible impurities are removed through filtration or centrifugation, and the free fatty acid is removed through reduced pressure distillation to obtain the final product.
TABLE 35 fatty acid composition and distribution of final product
Fatty acid (mol%) General assembly sn-2 sn-1,3
C6:0 0.06 0.06 0.06
C8:0 0.57 0.18 0.77
C10:0 0.57 0.48 0.61
C12:0 6.86 12.03 4.27
C14:0 2.32 1.35 2.81
C16:0 29.72 62.05 13.56
C18:0 2.25 2.64 2.06
C18:1n-9 28.65 12.83 36.56
C18:2n-6 26.23 7.65 35.52
C18:3 2.76 0.73 3.78
％sn-2PA* 69.6
C18:2/C18:3 9.49
TABLE 36 triglyceride composition of the final product
Figure BDA0003189883580000331
Figure BDA0003189883580000341
Through similarity model evaluation, the similarity of the obtained final product to human milk fat in the composition of fatty acid, sn-2 fatty acid and triglyceride is shown in the following table:
TABLE 37 similarity of product to breast milk fat
Degree of similarity (%) Acid hydrolysis product
GFA 98.7
Gsn-2FA 98.5
GTAG 92.57
By comparing the similarity between the acidolysis product and the breast milk fat by using an evaluation model, the obtained product has the fatty acid composition and distribution consistent with those of the breast milk fat, and is also highly similar to the breast milk fat in triglyceride composition.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims (6)

1. A method for preparing structural lipid based on breast milk triglyceride composition is characterized in that: the method comprises the following steps:
primary acidolysis: the method comprises the following steps of (1) taking palm stearin as a raw material, selecting vegetable oil fatty acid rich in oleic acid and linoleic acid as an acyl donor, taking sn-1,3 lipase as a catalyst, and reducing the content of sn-1,3 palmitic acid by one-time acidolysis in a packed bed reactor;
low-temperature fractionation: removing saturated fatty acid and saturated triglyceride by a low-temperature fractionation procedure to obtain liquid oil;
adjusting the sn-2 fatty acid composition of the liquid oil: establishing a sn-2 fatty acid mixed model, and adjusting the composition of sn-2 fatty acid of liquid oil;
modulating sn-1,3 fatty acid composition: establishing an acidolysis reaction fatty acid balance model to obtain a substrate ratio and a free fatty acid composition which meet the requirements of the composition of the breast milk fat sn-1,3 fatty acid;
adjusting the free fatty acid composition: establishing a fatty acid mixed model, and obtaining free fatty acid composition and substrate ratio required by the sn-1,3 fatty acid composition step;
modulation of triglyceride composition: establishing an acidolysis reaction triglyceride balance model to obtain a free fatty acid composition meeting the breast milk fat triglyceride composition;
secondary acidolysis: obtaining a product which is consistent with the composition and distribution of the fatty acid of the breast milk and the composition of triglyceride;
the sn-2 fatty acid mixed model is a calculation model for establishing the sn-2 fatty acid composition of the grease according to the fatty acid composition and distribution of the vegetable oil and the composition range of the sn-2 fatty acid of breast milk fat, and the calculation model comprises the following steps:
Figure FDA0003688780070000011
wherein sn-2 FA% is sn-2 fatty acid composition of the mixed oil, Y represents different fatty acids, and Y represents1(sn-2)And Yi(sn-2)The mole percentage of each fatty acid on the sn-2 position of the palm stearin and the selected oil respectively, XiThe molar ratio of the selected grease to the palm stearin is adopted;
by setting XiAccording to the formula, the fatty acid composition and distribution in the mixed system are calculated, an inequality is established according to the sn-2 fatty acid range of breast milk fat, and the addition range of each oil in the range is calculated;
when mixing, the minimum amount of exogenous vegetable oil is added while the fatty acid composition at the sn-2 site of breast milk fat is satisfied; the addition amount of the exogenous vegetable oil is as follows:
Figure FDA0003688780070000012
Xithe molar ratio of the selected grease to the palm stearin is adopted; m is the sum of the proportions of the selected oils, the mixed oil has the maximum sn-2 palmitic acid content, the minimum exogenous oil needs to be added on the basis of ensuring the sn-2 fatty acid in the fat range of breast milk, and MatlabR2010a (MathWorks, Natick, MA, USA) is adopted to optimize the addition proportion of the oil;
the oil selected for adjusting the sn-2 fatty acid composition is one or more of coconut oil, palm kernel oil, soybean oil and linseed oil;
the substrate ratio and the fatty acid ratio range required by the composition and distribution of the breast milk fatty acid are predicted by an acidolysis reaction fatty acid balance model, wherein the acidolysis reaction fatty acid balance model is as follows:
in the reaction system, the content of triglyceride is m, the content of fatty acid is h, in the reaction process, the used lipase is sn-1,3 position specific lipase, and the fatty acid accords with random distribution on the sn-1,3 position; in the whole reaction system, the fatty acid types are n, and different fats areThe acid is defined as Xi, the acyl transfer is controlled by using the reaction condition, the change amount of the sn-2 fatty acid is small, and therefore, the change of the sn-2 fatty acid is ignored; in the system, the fatty acids participating in the reaction are mainly the triglyceride sn-1,3 fatty acids and the free fatty acids added, and for the individual fatty acids Xi, the molar percentage of Xi fatty acids in the position sn-1,3 of the triglyceride is expressed as Msn-1/-3XiThe molar percentage of free fatty acids Xi is expressed as MXiThus, when the system reaches equilibrium, the sn-1,3 content (sn-1/3Xi) of the triglycerides at equilibrium for the Xi fatty acid reaction is expressed as:
Figure FDA0003688780070000021
due to the fact that
Figure FDA0003688780070000022
Therefore, the number of the first and second electrodes is increased,
Figure FDA0003688780070000023
the model is further simplified as:
Figure FDA0003688780070000024
let h/m be S, i.e. the molar ratio of free fatty acids to triglycerides is S: 1, therefore, the sn-1,3 content (sn-1/3Xi) of triglycerides at the Xi fatty acid reaction equilibrium is further simplified to:
Figure FDA0003688780070000025
according to the composition of each fatty acid at the sn-1 and 3 positions of the mixed oil, calculating the theoretical content of different fatty acids at the sn-1 and 3 positions after the acidolysis is balanced;
obtaining the required vegetable oil fatty acid proportion within the fatty acid proportion range predicted by an acidolysis reaction fatty acid balance model, and realizing the vegetable oil fatty acid proportion by a fatty acid mixing model, wherein the fatty acid mixing model is as follows:
Figure FDA0003688780070000031
wherein, Y1Is the molar ratio of the individual fatty acids in the free fatty acids, X1In terms of mole ratio of free fatty acids, YiRespectively the mole percentage of each fatty acid of the selected grease, XiThe molar ratio of the selected grease;
the fatty acid selected in the fatty acid mixing model is derived from one or more of coconut oil, tea seed oil, sunflower seed oil, palm kernel oil, rapeseed oil, soybean oil and linseed oil;
determining the proportion of fatty acid meeting the composition of the breast milk triglyceride through an acidolysis reaction triglyceride balance model, wherein the acidolysis reaction triglyceride balance model is as follows:
in the whole reaction system, the content of triglyceride is M, the content of fatty acid is h, the types of fatty acid are n, the different fatty acids are Xi, and the molar percentage of Xi on the sn-1,3 position of triglyceride is expressed as M for the individual fatty acid Xisn-1/3XiThe molar percentage of Xi in the sn-2 position is expressed as Msn-2XiThe molar percentage of free fatty acids Xi is expressed as MXiThus, when the system reaches equilibrium, the probability of three arbitrary fatty acids Xs, Xj and Xk at the triglyceride position, according to the random distribution principle, is expressed as follows:
Figure FDA0003688780070000032
the model is further simplified as:
Figure FDA0003688780070000033
let h/m be S, i.e. the molar ratio of free fatty acids to triglycerides is S: 1, therefore, the above model is further simplified to:
Figure FDA0003688780070000041
thus, after the acidolysis reaction has reached equilibrium, the ratio of triglyceride molecules contained is:
Figure FDA0003688780070000042
2. the method for preparing structural lipids based on the composition of breast milk triglycerides as claimed in claim 1, characterized in that: in the primary acidolysis, the vegetable oil rich in oleic acid is one or two of rapeseed oil and tea seed oil; the vegetable oil rich in linoleic acid is one or two of soybean oil and sunflower seed oil.
3. The method for preparing structural lipids based on the triglyceride composition of breast milk according to claim 1, wherein: in the primary acidolysis, the reaction condition is that fatty acid and palm stearin are mixed according to the ratio of 4-8: 1.
4. The method for preparing structural lipids based on the composition of breast milk triglycerides as claimed in claim 1, characterized in that: the enzymes used in the primary acidolysis and the secondary acidolysis are sn-1,3 lipase, and the sn-1,3 lipase comprises one or more of Lipozyme RM IM, NS40086 and lipase DF.
5. The method for preparing structural lipids based on the composition of breast milk triglycerides as claimed in claim 1, characterized in that: in the primary acidolysis and the secondary acidolysis, the temperature is set to be 50-60 ℃.
6. The method for preparing structural lipids based on the composition of breast milk triglycerides as claimed in claim 1, characterized in that: in the low-temperature fractionation, heating the grease to 55-65 ℃ and maintaining for 20-30 min, then reducing the temperature to 35-40 ℃ at a speed of 4-10 ℃/h, growing crystals for 3-5 h, then reducing the temperature to 18-28 ℃ at a speed of 3-8 ℃ for 2-8 h, rotating at 30-50 rpm, and filtering and separating saturated fatty acid and solid fat after fractionation and crystallization are finished to obtain the liquid oil.
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