Method for preparing stearic acid by fractionating shea butter crude oil through solvent method and obtained stearic acid

Abstract

The invention belongs to the technical field of food grease, and particularly relates to a method for preparing stearic acid through solvent-method fractionation of shea butter crude oil and the obtained stearic acid, and the method comprises the following steps: a gum separation step S1, fully stirring and mixing shea butter crude oil in a molten state and with saponin removed with an organic solvent, and separating to obtain a pectin phase and an oil phase; and S2, cooling the oil phase to crystallize, and carrying out filter pressing to obtain a stearic acid solid phase and an oleic acid liquid phase. And S3, removing the solvent, namely evaporating and removing the organic solvent in the pectin phase, the stearic acid solid phase and the oleic acid liquid phase to respectively obtain pectin, stearic acid and oleic acid. According to the method, the shea butter crude oil is fractionated by adopting the organic solvent, so that the flowability of the shea butter crude oil is greatly enhanced, the crystallization process is convenient to control, and the time for fractionating stearic acid, namely solid fat in the later period is greatly shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of food oils and fats, and particularly relates to a method for preparing stearic acid by solvent fractionation of shea butter crude oil and the obtained stearic acid. Background Art

[0002] Shea butter can be squeezed out of the nuts of the shea tree to produce a large amount of shea butter. After fractionation and crystallization, shea butter can be obtained as a vegetable oil with an ivory appearance. Its chemical composition is mainly composed of triglycerides derived from stearic acid and oleic acid. It is widely used in cosmetics as a moisturizer, ointment or lotion. Shea butter is also edible, and the chocolate industry also uses shea butter mixed with other oils as a substitute for cocoa butter. Stearic acid extracted from shea butter is used in chocolate products to extend the shelf life of the product and enhance the heat resistance of the product.

[0003] At present, the methods for preparing stearic acid from crude shea butter oil are dry method and surfactant method. The dry method takes a long time (generally 40 hours), has low efficiency, low solid fat yield (generally about 34%), and undesirable crystal form. The surfactant method has serious environmental pollution and high cost. Summary of the invention

[0004] The present invention is directed to the above technical problems and aims to provide a method for preparing stearic acid by solvent fractionation of shea butter crude oil.

[0005] The method for preparing stearic acid by solvent fractionation of shea butter crude oil of the present invention comprises the following steps:

[0006] The gelatin separation step S1 is to stir and mix the molten shea butter from which the sapodilla leaves have been removed with an organic solvent to obtain a pectin phase and an oil phase;

[0007] In the crystallization step S2, the oil phase is cooled to crystallize, and filtered to obtain a stearic acid solid phase and an oleic acid liquid phase.

[0008] In the solvent removal step S3, the organic solvent in the pectin phase, the stearic acid solid phase and the oleic acid liquid phase is evaporated and removed to obtain pectin, stearic acid and oleic acid respectively.

[0009] Optionally, in the method for preparing stearic acid by solvent fractionation of shea butter crude oil as described above, the organic solvent is acetone, n-hexane, ethanol and / or isopropanol, and the organic solvent is preferably acetone.

[0010] Optionally, in the method for preparing stearic acid by solvent extraction of shea butter crude oil as described above, in the gelatinization step S1, the usage ratio of shea butter crude oil to acetone solvent is 1-5 mL:1 g, preferably 3-4 mL:1 g, and more preferably 4 mL:1 g.

[0011] Optionally, in the method for preparing stearic acid by solvent fractionation of shea butter crude oil as described above, the method for preparing stearic acid by solvent fractionation of shea butter crude oil further comprises:

[0012] Pretreatment step S0, melting shea butter crude oil, and removing impurities and sapodilla, to obtain molten shea butter crude oil without sapodilla.

[0013] Optionally, in the method for preparing stearic acid by solvent extraction of shea butter crude oil as described above, the pretreatment step S0 comprises the following sub-steps:

[0014] In step S01, the shea butter is heated with steam at a temperature of 100° C. to 190° C. until it is completely melted;

[0015] In step S02, the melted shea butter is kept at a temperature of 50° C. to 55° C. under steam for 1 to 3 hours, and impurities are filtered out;

[0016] Step S03, the shea butter crude oil with impurities removed is maintained at 50°C to 55°C under steam, 16 degrees Baume NaOH alkali solution (i.e. theoretical alkali amount (kg) = 0.713 × acid value × oil weight (ton)) is injected according to the acid value detected by the shea butter crude oil, stirring is continued for 30 minutes to 40 minutes at a rotating speed of 10rpm to 20rpm, and then standing for 6h to 12h to fully react and precipitate and release the soap nuts, or standing for 0.5h to 1h and then separating the soap nuts by high-speed centrifugation at a rotating speed of 40000 to 50000rpm to obtain the shea butter crude oil with the soap nuts removed;

[0017] In step S04, the shea butter from which the sapodillas have been removed is heated to 70° C. to 80° C., preferably 70° C. to 75° C., under stirring at 60 to 100 rpm to crack the crystals;

[0018] In step S05, the shea butter crude oil after crystal breaking is rapidly cooled to 45°C to 50°C, preferably 50°C, and preferably cooling water is injected to rapidly cool it.

[0019] Optionally, in the method for preparing stearic acid by solvent extraction of shea butter crude oil as described above, the gelatinization step S1 comprises the following sub-steps:

[0020] In step S11, acetone solvent is injected into the shea butter at 45° C. to 50° C., preferably 50° C., and stirred at 40 rpm to 50 rpm for 30 minutes to 40 minutes to mix thoroughly;

[0021] Step S12, then standing at 45°C to 50°C, preferably at 50°C for 3h to 6h to separate into layers to obtain pectin phase and oil phase, or standing at 45°C to 50°C, preferably at 50°C for 0.5h to 1h and then high-speed centrifuging at 40000 to 50000 rpm to obtain pectin phase and oil phase.

[0022] Optionally, in the method for preparing stearic acid by solvent fractionation of shea butter crude oil as described above, the crystallization step S2 comprises the following sub-steps:

[0023] In step S21, the separated oil phase at 45°C to 50°C, preferably 50°C, is pumped into a crystallization tank under stirring at 40 rpm to 50 rpm, first rapidly cooled to 40°C, and then slowly cooled to 5°C to 15°C, preferably 8°C to 12°C, more preferably 10°C, over 2h to 10h, preferably 6h to 10h, to crystallize and grow the crystals;

[0024] In step S22, finally, a plate and frame are used for filter pressing at a pressure of 4 kg to 6 kg to obtain a stearic acid solid phase and an oleic acid liquid phase.

[0025] Optionally, in the method for preparing stearic acid by solvent fractionation of shea butter crude oil as described above, the solvent removal step S3 comprises the following sub-steps:

[0026] In step S3a1, the stearic acid solid phase after the filter press is melted with steam at a temperature of 100° C. to 190° C.;

[0027] In step S3a2, the temperature of the melted stearic acid is maintained at 56.5°C to 65°C, preferably 58°C to 62°C, more preferably 60°C, by using steam to evaporate the acetone solvent for 30 minutes to 40 minutes to obtain a solid stearic acid product.

[0028] Optionally, in the method for preparing stearic acid by solvent fractionation of shea butter crude oil as described above, the solvent removal step S3 comprises the following sub-steps:

[0029] Solvent removal step S3b, evaporating the acetone solvent in the pectin phase to obtain food-grade pectin;

[0030] Preferably, the pectin phase is heated with steam to 56.5°C to 65°C, preferably 58°C to 62°C, more preferably 60°C, and the acetone is evaporated for 30 minutes to 40 minutes to obtain food grade pectin.

[0031] Optionally, in the method for preparing stearic acid by solvent fractionation of shea butter crude oil as described above, the solvent removal step S3 comprises the following sub-steps:

[0032] Solvent removal step S3c, evaporating the acetone solvent in the oleic acid liquid phase to obtain an oleic acid product;

[0033] Preferably, the oleic acid liquid phase is heated with steam to evaporate acetone at 56.5°C to 65°C, preferably 58°C to 62°C, more preferably 60°C for 30 minutes to 40 minutes to obtain the finished oleic acid product.

[0034] Another object of the present invention is to provide stearic acid prepared by solvent fractionation of shea butter crude oil.

[0035] The positive and progressive effects of the present invention are:

[0036] 1. The present invention adopts organic solvent to extract shea butter crude oil, so that the fluidity of shea butter crude oil is greatly enhanced, which is convenient for controlling the crystallization process and greatly shortens the time of extracting stearic acid, i.e., solidifying fat, in the later stage.

[0037] 2. The organic solvent of the present invention does not undergo any chemical reaction with the raw materials during the entire production process, but is simply converted from liquid to gas, and then from gas to liquid, and is recycled.

[0038] 3. The present invention separates out solid fat with a high content of SOS type triglyceride by solvent method, and the solid fat separation yield is as high as 42%.

[0039] 4. The present invention can effectively produce more β-crystal solid fat with an ideal crystal form to achieve properties closer to cocoa butter. Adding the fractionated solid fat of the present invention to cocoa butter for the preparation of chocolate products not only reduces costs for enterprises, but also gives the products better functional properties of inhibiting blooming, thereby extending the shelf life of the products.

[0040] 5. In the fractionation process of the present invention, the pectin in the shea butter is dissolved in the organic solvent, and food-grade pectin can be obtained after subsequent fractionation, thereby obtaining natural food-grade pectin, thereby increasing the added value of the product and increasing additional income. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The disclosure of the present invention will become more apparent with reference to the accompanying drawings, which are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0042] Figure 1 Schematic diagram showing the effect of the liquid-to-solid ratio on the comprehensive score of solid fat in Example 5 of the present invention;

[0043] Figure 2 Schematic diagram of the effect of fractionation temperature on the comprehensive score of solid fat in Example 5 of the present invention;

[0044] Figure 3 This is a schematic diagram showing the effect of extraction time on the comprehensive score of solid fat in Example 5 of the present invention;

[0045] Figure 4 Solid fat content curve of each oil in Example 7 of the present invention;

[0046] Figure 5 The XRD patterns of shea butter, fractionated solid fat and cocoa butter in Example 7 of the present invention are as follows;

[0047] Figure 6Schematic diagram of DSC curves of cocoa butter, shea butter and fractionated solid fat thereof in Example 9 of the present invention. DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0049] It should be noted that the following embodiments and features therein may be combined with each other if there is no conflict.

[0050] Examples 1 to 3

[0051] The present embodiment provides a method for preparing stearic acid by solvent fractionation of shea butter crude oil, which specifically comprises the following steps:

[0052] Shea butter crude oil pretreatment step S0

[0053] Step S01: sending a volume of V of shea butter into a carburizing tank, and inputting a temperature T into the carburizing tank coil. S01 The steam is used to heat the shea butter until it is completely melted.

[0054] Step S02: melted shea butter is put into a sedimentation tank at a temperature T S02 Let it stand for a while (standing time t S02 ), and filter out impurities.

[0055] Step S03: pump the impurity-free shea butter into an alkali refining pot, and maintain the temperature T by inputting steam into the alkali refining pot coil. S03 , inject M amount of NaOH solution, at V S031 Continuous stirring at a speed (stirring time t S031 ), then use method ① to let it stand (standing time t S032a ) fully react and precipitate and release the saponins or adopt method ② to pump into a continuous production centrifuge and S032b The soap nuts are separated by high-speed centrifugation at a rotation speed to obtain shea butter without the soap nuts.

[0056] Step S04: pump the shea butter from which the soapberry is removed into a solvent mixing tank, inject steam into the mixing tank coil, and mix the shea butter in a solvent mixing tank. S04 Heat to temperature T while stirring at a high speed S04 To crack the crystal.

[0057] Step S05, by injecting cooling water into the mixing tank coil, the shea butter after crystal breaking is rapidly cooled to a temperature T S05 .

[0058] The glue separation process step S1 includes the following steps:

[0059] Step S11, at temperature T S11 The acetone solvent is injected into the shea butter crude oil, and the amount ratio of the shea butter crude oil to the acetone solvent is m 毛油 :m 丙酮 , and at V S11 Stir and mix thoroughly at the speed (stirring time t S11 ).

[0060] Step S12: pump the mixed solution into the degumming pot, and then adopt method ③ to heat the mixture at a temperature T S12a Stand at constant temperature (standing time t S121a ) to obtain pectin phase and oil phase by separation, or by using method ④ at temperature T S12b Pump down at V S12b High-speed centrifugation at a speed of 10000rpm was used to obtain the pectin phase and the oil phase.

[0061] The crystallization step S2 comprises the following sub-steps: Sub-step S21, pumping the oil phase after removing pectin into a crystallization tank, and the crystallization tank is set at V S21 Under continuous stirring at a high speed, first rapidly cool down (inject cooling water into the coil to rapidly cool down) to T S211 , then at t S21 Cool down to temperature T S212 To crystallize and grow crystals.

[0062] Step S22, using a fully enclosed plate and frame filter press plate frame P S22 The stearic acid solid phase and the oleic acid liquid phase were obtained by filtration.

[0063] The solvent removal step S3 includes the following sub-steps in no particular order:

[0064] The solvent removal step S3a, the stearic acid solid phase after the filter press is heated to T S3a1 The molten stearic acid is melted by steam, and the melted stearic acid is pumped into the distillation tank and the temperature is maintained at T by steam. S3a2 The acetone solvent is evaporated and recovered to obtain a solid stearic acid product, i.e., solid fat.

[0065] The solvent is removed in sub-step S3b (this step can also be performed directly after sub-step S12), the pectin phase is pumped into a distillation tank, and heated to T with steam. S3b The acetone is evaporated and recovered to obtain food grade pectin.

[0066] The solvent removal step S3c is to pump the oleic acid liquid phase into a distillation tank and heat it with steam at T S3cThe acetone is evaporated and recovered to obtain the finished oleic acid.

[0067] The extraction parameters of Examples 1 to 3 are shown in Table A, and the extraction results are shown in Table B.

[0068] Table A: Extraction parameters of Examples 1 to 3

[0069]

[0070]

[0071]

[0072] Table B Fractionation results of Examples 1 to 3

[0073] Example 1 Example 2 Example 3 Extraction time 10 hours 8 hours 6 hours Solid fat melting point 37.5℃ 36.4℃ 35.2℃ Solid fat yield 42％ 40％ 38％ Solid fat crystal β-form β-form β-form

[0074] Conclusion: the solvent method shea butter fractionation of the invention, the fractionation crystallization temperature in step S21 is 10 ℃, and the fractionation time (time of decreasing from 40 ℃ to 10 ℃) is 6~10 hours. Through the fractionation time of 6~10 hours, it is enough to realize that the crystal particle shape and the crystal form of stearic acid in the oil phase are complete, which are all beta crystals, and can meet the fractionation requirements. Compared with the 40 hours fractionation crystallization time of dry fractionation, the crystallization time is greatly saved, and the solid fat yield is up to 42%. Compared with the 34% of the solid fat yield of traditional dry fractionation, the present invention adopts the solvent method to fractionate the solid fat yield high.

[0075] Example 4 Comparison of different organic solvents

[0076] The present embodiment adopts acetone, n-hexane, ethanol and isopropanol 4 kinds of organic solvents to extract shea butter crude oil to prepare stearic acid for comparison, and adopts the method of embodiment 1, adopts the above-mentioned 4 kinds of different organic solvents to extract solid fat respectively in the sub-step S11 of the gel separation treatment step S1. It can be understood by those skilled in the art that the temperature for evaporating and recovering the organic solvent in each sub-step in the solvent removal step S3 should be higher than the boiling point temperature of the corresponding organic solvent.

[0077] In the present embodiment, the comprehensive score of shea butter oil fractionation and solid fat extraction is used as an evaluation index. The higher the score, the better the solvent is considered to be for shea butter oil fractionation.

[0078] 1. Determination of melting point: Determine in accordance with GB / T 12766-2008.

[0079] 2. Determination of data inspection value

[0080] This embodiment will investigate the two indicators of shea butter solid fat yield (Y) and solid fat melting point (Tm). The melting point of solid fat will affect the final taste of the product, and the yield will affect the economic benefits of the enterprise. Therefore, the melting point factor weight is set higher than the yield factor weight, and the solid fat yield and melting point weights are set to 0.4 and 0.6 respectively. The score calculation formula is 0.4*Y+0.6*(28.1-|36.0-Tm|).

[0081] Table 1 Effect of different solvents on the comprehensive score of solid fat

[0082]

[0083] As can be seen from the results in Table 1, acetone solvent has the best effect as the fractionation of solid fat in shea butter. Grease is as non-polar molecule, and the dielectric constant of normal ethane is minimum, and the solubility of grease is large, but the solid fat fusing point isolated is lower and compared with other solvents, and normal ethane needs lower crystallization temperature and the formation rate of crystallization is slow, and acetone is good to the solid fat separation performance of shea butter crude oil. Therefore, acetone is preferably used as the fractionation solvent of shea butter crude oil solid fat.

[0084] Example 5 Single Factor Test

[0085] 1. The influence of liquid-to-solid ratio on the comprehensive score of solid fat fractionation:

[0086] The liquid-to-solid ratio (amount ratio) of shea butter and acetone solvent of 1-5mL:1g was compared, and the process of Example 1 was adopted, and 1mL:1g, 2mL:1g, 3mL:1g, 4mL:1g and 5mL:1g were used in the sub-step S11 of the gel separation treatment step S1, and 5 different liquid-to-solid ratios were used for fractionation and solid fat extraction respectively. Among them, the fractionation crystallization temperature in the sub-step S21 of the selected crystallization step S2 was 10°C, and the fractionation time was 6h.

[0087] from Figure 1 It can be seen that, along with the increase of liquid-to-material ratio, the trend of first rising and then falling appears in the shea butter fractionation solid fat melting point, and the fractionation solid fat yield then presents a trend of constantly decreasing. Cause its comprehensive score to appear the trend of first increasing and then decreasing, and when the liquid-to-material ratio is 4mL:1g, the comprehensive score is 40.88 points at most, this is because along with the increase of liquid-to-material ratio, the crystal form in the shea butter is converted into metastable β' type and α-type crystal form by the most stable β type, causes the increase of the adsorption amount of the crystal to the liquid phase oil, causes the fractionation solid fat melting point to appear the trend of first rising and then falling, and presents a trend of constantly decreasing to the solid fat yield. Therefore, the preferred liquid-to-material ratio is 4mL:1g as the best liquid-to-material ratio of this experiment.

[0088] 2. The influence of fractionation temperature on the comprehensive score of fractionation and solid fat

[0089] The process of Example 1 was adopted, and 0°C, 5°C, 10°C, 15°C and 20°C, 5 different fractionation temperatures were used in sub-step S21 of the crystallization step S2 to fractionate and crystallize the solid fat. The liquid-to-material ratio of shea butter crude oil to acetone in sub-step S11 of the gel separation treatment step S1 was selected to be 4mL:1g, and the fractionation time in sub-step S21 of the crystallization step S2 was 6h.

[0090] from Figure 2 It can be seen that with the increase of fractionation temperature, the comprehensive score of fractionation solid fat is close when it is lower than 10℃, and its score gradually decreases when it is higher than 10℃. This is because when the fractionation temperature is low, some oils with low melting points are crystallized, which increases the amount of crystallization accordingly; when the crystallization temperature is too low, the viscosity of the system will increase, and it will be difficult for the molecules to move, resulting in the growth of crystals being hindered, and some crystals will also form metastable crystal forms, which will affect the fractionation effect. In addition, if the crystallization temperature is too low, the solid fat will wrap more liquid oil, which will also make the fractionation effect worse; when the fractionation temperature is too high, shea butter crude oil has few opportunities to crystallize, and only some high-melting-point triglycerides will crystallize, resulting in low solid fat content, and then low comprehensive score of fractionation solid fat. Finally, considering the comprehensive score of fractionation solid fat and production cost, 10℃ is preferred as the optimal fractionation temperature for this experiment.

[0091] 3. The influence of fractionation time on the comprehensive score of fractionation and solid fat

[0092] The process of Example 1 was adopted, and 2h, 4h, 6h, 8h and 10h were used in the sub-step S21 of the crystallization step S2, and 5 different extraction times were used to extract the solid fat. Among them, the liquid-to-material ratio of shea butter crude oil to acetone in the sub-step S11 of the gel separation treatment step S1 was selected to be 4mL:1g, and the extraction temperature in the sub-step S21 of the crystallization step S2 was 10°C.

[0093] from Figure 3 It can be seen that with the continuous extension of the crystal growth time, the fractionation and solid fat score shows a trend of first rising and then falling. When the fractionation time is 8h, the fractionation and solid fat comprehensive score is the highest, which is 44.54 points. As for the solid fat yield of shea butter crude oil, it will decrease. This may be because the fractionation time is too long, resulting in the destruction of the crystal nucleus, so there is an optimal value for the crystal growth time. Therefore, 8h is preferred as the optimal fractionation time for this experiment.

[0094] Example 6 Orthogonal test results analysis

[0095] On the basis of known optimal fractionation solvent, the influence of three factors, namely, liquid-to-solid ratio (A), fractionation temperature (B) and fractionation time (C), on the comprehensive score of shea butter stearin was studied. Therefore, the process of embodiment 1 was adopted, and orthogonal test was performed on the above three factors, and L (33) was taken to perform orthogonal test, and the optimal fractionation process was selected by scoring formula, and the level table was shown in Table 2, and the results were shown in Table 3.

[0096] Table 2 Orthogonal experimental design level table

[0097]

[0098] Table 3 Orthogonal test results

[0099]

[0100] Table 3 uses intuitive analysis method to compare the range values ​​of each factor. The maximum range value of B is 7.637, and the minimum range value of C is 0.669. Therefore, it can be concluded that the extraction temperature has the greatest influence on the comprehensive score of cocoa butter-like in solvent-extracted shea butter, and the extraction time has the least influence, that is, extraction temperature>liquid-to-solid ratio>extraction time.

[0101] The fractionation process obtained by the range method is A 1 B 2 C 3 That is, the fractionation temperature is 10°C, the liquid-to-solid ratio is 3:1, and the fractionation time is 10h. The comprehensive score obtained based on this process is 44.462 points, which is less than 45.263 points.

[0102] Therefore, the process conditions of Experiment No. 5, i.e., the fractionation temperature of 10° C., the liquid-to-solid ratio (crude shea butter: acetone) of 4:1 (mL / g), and the fractionation time of 10 h were selected as the optimal fractionation conditions of the present invention.

[0103] Example 7 Analysis of the properties of the fractionation products

[0104] 1. Determination of solid fat content (SFC) of oils and fats

[0105] For cocoa butter-like products, solid fat content (SFC) is an important physical and chemical property index, which affects the unique taste and physical and chemical properties of cocoa products. Among them, the hardness of oil products under refrigerated conditions mainly depends on the value of SFC at 10°C, the rheological properties of oil products depend on the value of SFC at 20°C, and SFC at 35°C is an important index that determines the meltability of oil products. Therefore, the solid fat content of oil at 35°C needs to be as low as possible to prevent the sandy and rough feeling in the oil products.

[0106] In this embodiment, unfractionated shea butter, shea butter fractionated solid fat obtained by the process of Example 1 combined with the optimal fractionation conditions of Example 6, shea butter fractionated liquid fat (i.e., shea butter fractionated oleic acid) and natural cocoa butter were subjected to SFC determination.

[0107] The SFC values ​​of the above four samples were determined according to the IUPAC2.15 method. The specific process is: first turn on the MQC (benchtop nuclear magnetic resonance analyzer) and preheat for 12 hours; turn on the water bath and adjust the temperature to 80°C; add the raw materials into a beaker and water bath; the accurate raw materials (about 2.5g) are kept at a constant temperature of 80°C for 0.5h (to eliminate memory crystallization); kept at a constant temperature of 0°C for 1.5h (to promote nucleus formation); kept at a constant temperature of 26°C (to stabilize the crystal form) for 40h; kept at a constant temperature of 0°C (to maintain the crystal form) for 1.5h; then kept at a gradient temperature of 0, 5, 10, 15, 20, 25, 30, 35, and 40°C for 30min, then quickly wipe off the water droplets outside the oil sample tube, and immediately put it into the sample slot of the nuclear magnetic resonance instrument to determine the SFC value and record the results.

[0108] from Figure 4 It can be seen that the basic trend is that the SFC values ​​of the four samples gradually decrease with increasing temperature, and the SFC values ​​of shea butter fractionated solid fat and natural cocoa butter are relatively close. The fractionated solid fat obtained after shea butter fractionation has similar crystal structure, triglyceride composition and melting properties as natural cocoa butter, indicating that fractionation of shea butter is beneficial. In a lower temperature range, the SFC value of natural cocoa butter is slightly higher than that of fractionated solid fat. In the temperature range of 30-35℃, the SFC of both decreases rapidly, but relatively speaking, the downward trend of the SFC value of fractionated solid fat is not as good as that of cocoa butter. At 35℃, the SFC value of fractionated solid fat still maintains a high content. This is mainly because the fractionated solid fat contains a certain amount of high melting point triglycerides such as PSS and SSS, and the melting points of some monoglycerides and diglycerides in the fractionated solid fat are higher than 35℃. These factors make it difficult for the fractionated solid fat to melt at this temperature.

[0109] 2. Determination of oil crystal form (XRD)

[0110] XRD is often used to study the long spacing and short spacing of oil crystals. The long spacing can be used to determine the interlayer stacking mode of oil crystals, and the short spacing can be used to determine the crystal form of oil crystals.

[0111] α-type, β'-type, and β-type crystal forms are the main crystal forms of oils and fats, and the stability of the three crystal forms gradually increases. For the short-spacing spectrum, the characteristic peak of the α-type short-spacing usually appears around 4.15A, the characteristic peak of the β'-type short-spacing usually appears around 4.20A and 3.80A, and the characteristic peak of the β-type short-spacing usually appears around 4.60A.

[0112] In this embodiment, unfractionated shea butter, shea butter fractionated solid fat obtained by combining the process of Example 1 with the optimal fractionation conditions of Example 6, and natural cocoa butter were subjected to XRD measurement.

[0113] The specific process of XRD determination is: weigh a certain amount of solid fat sample and spread it in the square hole on the glass sheet, and then use X-ray diffraction instrument to determine the crystal form of the solid fat sample. The conditions are set as working environment of 25°C, Cu target, working voltage of 40kV, current of 40mA, emission and anti-reflection slits of 1.0mm, receiving slit of 0.1mm, scanning range 2θ from 1.0° to 30.0°, scanning speed of 0.5 seconds / step, and step length of 0.02° (2θ).

[0114] from Figure 5 It can be seen that the shea butter has a very weak diffraction peak at about 4.60A before fractionation, indicating that although there is β crystal in the shea butter, its content is very small. In the chocolate industry, it is difficult to directly use it to produce stable β crystal products. Natural cocoa butter and fractionated solid fat have a strong diffraction peak at about 4.60A, indicating that there is a high content of β crystal in the oil. At the same time, there are also diffraction peaks at about 3.82A, indicating that the oil system also contains β' crystal, but the β crystal is dominant in the oil system. Therefore, fractionated solid fat can have the oil structure of forming a stable β crystal like natural cocoa butter, which promotes a smoother product texture.

[0115] Example 8 Analysis of triglyceride composition content of oils and fats

[0116] In this embodiment, unfractionated shea butter, shea butter fractionation solid fat obtained by the process of Example 1 in combination with the optimal fractionation conditions of Example 6, shea butter fractionation liquid fat (i.e. shea butter fractionation oleic acid) and natural cocoa butter are analyzed for content.

[0117] As shown in Table 4, after the shea butter crude oil is fractionated, the C52 type triglyceride content in the fractionated solid fat of the product increases significantly, while the POP and POS type triglycerides that are easy to form β' type crystals decrease significantly. The results are consistent with the β-type and β' type absorption peak intensities of the fractionated solid fat and cocoa butter in the X-diffraction pattern, indicating that the fractionation of shea butter crude oil is effective.

[0118] Table 4 Triglyceride composition of cocoa butter, shea butter, shea butter fractionation solid fat and fractionation liquid fat (%)

[0119]

[0120] Note: ECN is the equivalent carbon number (ECN = CN-2DB, CN is the number of carbon atoms, DB is the number of double bonds). During liquid chromatography separation, the peaks are separated in order from small to large according to ECN. P, palmitic acid; S, stearic acid; O, oleic acid; L, linoleic acid; A, arachidic acid; the results are expressed as mean ± SD; different letters abcd indicate significant differences between groups (P < 0.05)

[0121] Example 9 Melting and Crystallization Curve Analysis of Oils and Fats

[0122] In this embodiment, the melting and crystallization curves of unfractionated shea butter, shea butter fractionated solid fat obtained by the process of Example 1 combined with the optimal fractionation conditions of Example 6, and natural cocoa butter were analyzed.

[0123] like Figure 6 As shown in the figure, from the DSC curve of natural cocoa butter, it can be seen that a strong narrow and steep absorption peak appears at 34.93℃, which is because cocoa butter has good single crystals and its main triglycerides (POP, POS and SOS) show good compatibility; while the DSC curve of fractionated solid fat shows a strong absorption peak at 35.13℃ that lags behind natural cocoa butter, but the absorption peak is wider and not as sharp as the former. This is because the fractionated solid fat contains a higher content of long-chain saturated fatty acids, and the triglyceride composition is relatively complex than that of natural cocoa butter, which makes the absorption peak shifted and wider. The melting absorption peak of the fractionated solid fat shows narrower and steeper characteristics than the melting absorption peak of shea butter, indicating that the solvent method for fractionating shea butter has a significant effect.

[0124] Each experiment in the above embodiments of the present invention was repeated 3 times, and the experimental data results were expressed as Mean ± SD. The data were plotted using Origin8.0, and the experimental data were subjected to one-way analysis of variance using SPSS20.0. Duncan multiple comparisons were performed, and P < 0.05 was considered to be significantly different. The orthogonal experiment was expressed using range analysis.

[0125] The comprehensive scores / scores in the above-mentioned embodiments of the present invention are all calculated using the score calculation formula in Embodiment 4.

[0126] The present invention is described in detail above in conjunction with the embodiments of the accompanying drawings. A person skilled in the art can make various variations of the present invention according to the above description. Therefore, some details in the embodiments should not be construed as limiting the present invention, and the present invention shall be protected by the scope defined by the attached claims.

Claims

1. A method for preparing stearic acid by solvent fractionation of shea butter crude oil, characterized in that The steps include: The gelatin separation step S1 is to stir and mix the molten shea butter from which the sapodilla leaves have been removed with an organic solvent to obtain a pectin phase and an oil phase; Crystallization step S2, cooling the oil phase to crystallize, and filtering to obtain a stearic acid solid phase and an oleic acid liquid phase; In the solvent removal step S3, the organic solvent in the pectin phase, the stearic acid solid phase and the oleic acid liquid phase is evaporated and removed to obtain pectin, stearic acid and oleic acid respectively.

2. the method for preparing stearic acid by solvent separation of shea butter crude oil as claimed in claim 1, is characterized in that The organic solvent is acetone, n-hexane, ethanol and / or isopropanol, and the organic solvent is preferably acetone.

3. the method for preparing stearic acid by solvent separation of shea butter crude oil as claimed in claim 2, is characterized in that In the gelatin separation step S1, the usage ratio of shea butter crude oil to acetone solvent is 1-5 mL:1 g, preferably 3-4 mL:1 g, and more preferably 4 mL:1 g.

4. the method for preparing stearic acid by solvent separation of shea butter crude oil as claimed in claim 1, is characterized in that The method further comprises: Pretreatment step S0, melting shea butter crude oil, and removing impurities and sapodilla, to obtain molten shea butter crude oil without sapodilla.

5. the method for preparing stearic acid by solvent separation of shea butter crude oil as claimed in claim 4, is characterized in that The pre-processing step S0 comprises the following sub-steps: In step S01, the shea butter is heated with steam at a temperature of 100° C. to 190° C. until it is completely melted; In step S02, the melted shea butter is kept at a temperature of 50° C. to 55° C. under steam for 1 to 3 hours, and impurities are filtered out; Step S03, maintaining the decontaminated shea butter at 50°C to 55°C under steam, injecting 16 degrees Baume NaOH alkali solution calculated according to the acid value detected by the shea butter, stirring continuously for 30 minutes to 40 minutes at a speed of 10rpm to 20rpm, and then standing for 6h to 12h to fully react and precipitate and release the saponins, or standing for 0.5h to 1h and then centrifuging at a speed of 40000 to 50000rpm to separate the saponins, to obtain the shea butter with the saponins removed; In step S04, the shea butter from which the sapodillas have been removed is heated to 70° C. to 80° C., preferably 70° C. to 75° C., under stirring at 60 to 100 rpm to crack the crystals; In step S05, the shea butter crude oil after crystal breaking is rapidly cooled to 45°C to 50°C, preferably 50°C, and preferably cooling water is injected into the coil to rapidly cool it.

6. the method for preparing stearic acid by solvent separation of shea butter crude oil as claimed in claim 3, is characterized in that The glue dispensing step S1 includes the following sub-steps: In step S11, acetone solvent is injected into the shea butter at 45° C. to 50° C., preferably 50° C., and stirred at 40 rpm to 50 rpm for 30 minutes to 40 minutes to mix thoroughly; Step S12, then standing at 45°C to 50°C, preferably at 50°C for 3h to 6h to separate into layers to obtain pectin phase and oil phase, or standing at 45°C to 50°C, preferably at 50°C for 0.5h to 1h and then high-speed centrifuging at 40000 to 50000 rpm to obtain pectin phase and oil phase.

7. The method for preparing stearic acid by solvent fractionation of shea butter crude oil as claimed in claim 1, wherein: The crystallization step S2 comprises the following sub-steps: In step S21, the separated oil phase at 45°C to 50°C, preferably 50°C, is pumped into a crystallization tank under stirring at 40 rpm to 50 rpm, first rapidly cooled to 40°C, and then slowly cooled to 5°C to 15°C, preferably 8°C to 12°C, more preferably 10°C, over 2h to 10h, preferably 6h to 10h, to crystallize and grow the crystals; In step S22, finally, a plate and frame are used for filter pressing at a pressure of 4 kg to 6 kg to obtain a stearic acid solid phase and an oleic acid liquid phase.

8. The method for preparing stearic acid by solvent fractionation of shea butter crude oil as claimed in claim 1, wherein: The solvent removal step S3 comprises the following sub-steps: In step S3a1, the stearic acid solid phase after the filter press is melted with steam at a temperature of 100° C. to 190° C.; In step S3a2, the temperature of the melted stearic acid is maintained at 56.5°C to 65°C, preferably 58°C to 62°C, more preferably 60°C, by using steam to evaporate the acetone solvent for 30 minutes to 40 minutes to obtain a solid stearic acid product.

9. The method for preparing stearic acid by solvent fractionation of shea butter crude oil as claimed in claim 1, wherein: The solvent removal step S3 comprises the following sub-steps: Solvent removal step S3b, evaporating the acetone solvent in the pectin phase to obtain food-grade pectin; Preferably, the pectin phase is heated with steam to 56.5°C to 65°C, preferably 58°C to 62°C, more preferably 60°C, and the acetone is evaporated for 30 minutes to 40 minutes to obtain food grade pectin.

10. The method for preparing stearic acid by solvent fractionation of shea butter crude oil as claimed in claim 1, characterized in that The solvent removal step S3 comprises the following sub-steps: Solvent removal step S3c, evaporating the acetone solvent in the oleic acid liquid phase to obtain an oleic acid product; Preferably, the oleic acid liquid phase is heated with steam to evaporate acetone at 56.5°C to 65°C, preferably 58°C to 62°C, more preferably 60°C for 30 minutes to 40 minutes to obtain the finished oleic acid product.

11. Stearic acid prepared according to the method according to any one of claims 1 to 10.

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