AU2019299299B2

AU2019299299B2 - Method for lowering iodine value of glyceride

Info

Publication number: AU2019299299B2
Application number: AU2019299299A
Authority: AU
Inventors: Xiangyu Li; Hongrong LIU; Shuhuan LU; Fanti MA; Zhiming Wang; Liwen Zhang
Original assignee: Cabio Biotech Wuhan Co Ltd
Current assignee: Cabio Biotech Wuhan Co Ltd
Priority date: 2018-07-04
Filing date: 2019-07-04
Publication date: 2023-03-09
Anticipated expiration: 2039-07-04
Also published as: WO2020007335A1; CN108865445A; CN108865445B; AU2019299299A1; NZ772540A

Abstract

A method for lowering the iodine value of glyceride, comprising: enabling glyceride, saturated fatty acid and alkali to perform catalytic reaction under the action of lipase so as to obtain glyceride having a low iodine value. By means of sufficient quantity of saturated fatty acid residues provided by a saturated fatty acid salt formed in-situ by corresponding saturated fatty acid and alkali and the catalytic action of one-directional lipase, the reaction conditions are mild; the side reaction is rare; and the iodine value of glyceride is effectively lowered.

Description

METHOD FOR LOWERING IODINE VALUE OF GLYCERIDE FIELD OF INVENTION

[0011 This present disclosure generally relates to the technical field of synthesis and processing of glycerides, and in particular, to a method for lowering iodine value of glycerides. BACKGROUND OF INVENTION

[002] In industrial production, it is necessary to produce glycerides with low iodine value serving as raw materials for chemical production. However, existing methods to increase the saturation of glycerides are mainly carried out by chemical catalysis, and the catalysis reactions require high temperature and strict process conditions. Therefore, a simple process that can effectively lower the iodine value of glycerides is necessary. SUMMARY OF INVENTION

[003] The object of the present disclosure is to provide a method for lowering iodine value of glycerides, which can increase the content of saturated fatty acids in glycerides, thereby effectively reducing the iodine value of glycerides, under simple reaction conditions and few side reactions.

[004] The present disclosure provides the following technical solutions to solve technical issues.

[005] The present disclosure provides a method for lowering an iodine value of a glyceride, which comprises: enabling a glyceride, a saturated fatty acid, and an alkali to undergo a catalytic reaction under action of a lipase.

[006] On the basis of saturated fatty acid residues contained in the glyceride, a sufficient amount of saturated fatty acid residues are provided by the corresponding saturated fatty acid with catalysis of the lipase to achieve mild reaction conditions, few side reactions, and low iodine value of the resulting glyceride. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[007] In order to make the objectives, technical solutions, and advantages of embodiments of the present disclosure clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. If specific conditions are not specified in the embodiments or examples, it can be carried out in accordance with the conventional conditions or the conditions recommended by the manufacturer. Reagents and instruments without the manufacturer's indication are all known products that can be purchased commercially.

[008] A method for lowering an iodine value of a glyceride according to embodiments of the present disclosure is specifically described below.

[009] Some embodiments of the present disclosure provide a method of lowering the iodine value of the glyceride, which comprises: enabling a glyceride, a saturated fatty acid and an alkali to undergo a catalytic reaction under action of a lipase to obtain the glyceride with high content of saturated fatty acids.

[0010] Iodine value is an index of degree of unsaturation in an organic compound. Iodine value refers to grams of iodine that can be absorbed (added) in 1O0g of material, mainly used for the determination of oils, fatty acids, waxes and polyesters. The greater the degree of unsaturation, the higher the iodine value.

[0011] The glyceride can be monoglyceride, diglyceride, triglyceride, or a mixture of diglyceride and triglyceride.

[0012] It should be noted that the catalytic reaction includes transesterification and esterification. When the glyceride is mainly triglyceride, the transesterification is mainly carried out. When the glyceride includes part of diglyceride or part of monoglyceride, there are also esterification.

[0013] In some embodiments, the glyceride is glyceride with saturated fatty acid residues. Preferably, the iodine value of the glyceride is greater than 20. Preferably, at least a saturated fatty acid corresponding to saturated fatty acid residues contained in the glyceride is equivalent to the one of the saturated fatty acids added in the reaction system. On the basis of partial ester bonds with specific saturated fatty acid residues in the glyceride, a large amount of fatty acid residues are provided by specific fatty acid salts which are in-situ formed through the reaction between the specific saturated fatty acid and the alkali, thereby catalyzing transesterification and esterification reactions of the fatty acid residues by the lipase. The reactions result in mild reaction conditions, few side reactions and low iodine value of the formed glycerides.

[0014] In some embodiments, the amount of the saturated fatty acid is based on the ratio of the glyceride to the saturated fatty acid, and the ratio of saturated fatty acid residues to the total fatty acid residues in the reaction system greater than or equal to 90%, preferably greater than 92%, and more preferably greater than 95%. For example, the saturated fatty acid may be added, so that the ratio of saturated fatty acid residues to the total fatty acid residues in the reaction system is 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% etc.

[0015] In some embodiments, the molar ratio of the alkali to the saturated fatty acid is not more than 1, preferably, the molar ratio of the alkali to the fatty acid is not more than 0.025, and more preferably, the molar ratio of alkali to fatty acid ranges from 0.025 to 0.0001.

[0016] In some embodiments, the alkali is any of NaOH, KOH, NaOC 2H, KOC 2 H ,5 NaOCH 3, KOCH 3, solid base catalysts and mixtures thereof. More preferably, the alkali is NaOH or KOH. By setting the ratio of the reactants, the progress of the transesterification reaction of the esterification reaction can be fully satisfied, and thereby the reactants can be fully contacted to obtain a reaction product with a lower iodine value.

[0017] In some embodiments, the lipase may be a non-specific lipase, and its addition amount is 0.05-10% of glycerides, preferably 0.1-8% of glycerides. In a further preferred solution, the addition amount of Novozym 435 is 4-8%, the addition amount of Lipase DF "Amano" 15 ranges 0.1 to 1%, the addition amount of LipozymeTLIM is 4-8%, or the addition amount of LipaseAY30G is added in 0.1-1%. Forexample, the addition amount of the non specific lipase can be 0.05%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%. The addition amount of non-specific enzyme has an important influence on the reaction process. If the addition amount is too low, the catalytic effect cannot be achieved. If the addition amount is too high, the costs increase, and the contact between the reactants in the reaction process is affected, thereby resulting in poor reaction effect. Therefore, the addition amount of the non- specific lipase in the above range can fully achieve the catalytic effect on the reaction, so that the reaction can proceed thoroughly in the set reaction time.

[0018] In some embodiments, the lipase includes at least one of non-specific lipases and a specific lipase. Preferably, the lipase is a non-specific lipase, and the non-specific lipase includes at least one of Novozym 435, Lipase DF "Amano" 15, LipozymeTLIM and LipaseAY30G. For example, the non specific lipase can be Novozym 435 or Lipase DF "Amano" 15, or a mixture of Novozym 435 and Lipase DF "Amano" 15. Preferably, the non-specific lipase is Lipase DF "Amano" 15.

[0019] In some embodiments, the temperature of the catalytic reaction is 30-90 0 C, preferably 35-85 0 C. More preferably, the reaction temperature of the LipozymeTLIM is 65-70 0C, the reaction temperature of the Novozym 435 is 75-85 0C, the reaction temperature of Lipase DF "Amano" 15 is -40 0C, the reaction temperature of the LipaseAY30G is 35-40C.The catalytic reaction time is 0.5-9 hours, and the preferred reaction time is 1-4 hours. At this reaction temperature, the reaction temperature is lower than that of traditional chemical catalysts, and the reaction easily proceeds. The reaction temperature can be kept constant by heating in a water bath. The heating in the water bath is uniform and the effect of heat transferring effectively makes the reaction easy. Of course, other heating methods, such as furnace heating, can also be used to maintain the reaction temperature.

[0020] In some embodiments, the saturated fatty acid as a reactant in the reaction is selected from at least one of palmitic acid, stearic acid, caprylic acid, capric acid, lauric acid, myristic acid and arachidic acid. Preferably, it is at least one of palmitic acid, stearic acid, myristic acid and lauric acids, and more preferably at least one of palmitic acid and stearic acid. For example, palmitic acid or stearic acid, or saturated fatty acid may also be a mixture of palmitic acid and stearic acid in a certain ratio.

[0021] In the embodiment of the present disclosure, the purpose of adding alkali is that the alkali can in-situ react with fatty acids in the reaction system to form fatty acid salts. The fatty acid salts are a type of strong alkali weak acid salt with strong ionization ability and strong fatty acid residue activity. The ability of fatty acid salts to provide fatty acid residues is much greater than that of free fatty acids or fatty acid esters, thereby accelerating the rate of the transesterification reaction, shortening the reaction time, reducing the amount of the lipase and reducing costs. According to some embodiments, the glyceride containing saturated fatty acid residues may be cocoa butter, coconut oil, palm kernel oil or palm oil. Preferably, the glyceride containing saturated fatty acid residues is palm oil.

[0022] In some embodiments, enabling undergoing the catalytic reaction specifically comprises steps of mixing glyceride with the saturated fatty acid and the alkali, adding the lipase, and stirring under a condition of introducing inert gas. The protective effect of inert gas helps to avoid the influence of outside air on the reaction, and the stirring can make the reactants fully contact to make the reaction complete and fast. Furthermore, the catalytic reaction preferably includes steps of mixing the glyceride containing saturated fatty acid residues with the saturated fatty acid salts, and then adding the non-specific lipase, and stirring under a condition of introducing inert gas. In some embodiments, the speed of stirring during the agitation reaction ranges from 300 to 600 r/min, preferably 400 to 500 r/min.

[0023] In some embodiments, the inert gas can be selected from nitrogen, neon, argon, etc. Preferably, the inert gas is nitrogen.

[0024] In some embodiments, the reaction system also comprises a solvent. By adding a solvent to the reaction system, the reactants and reaction products can be dissolved in the solvent, thereby it is beneficial to the phase flow between the reactants and mass transfer effect to achieve a desirable effect during the reaction. Moreover, the solvent can also extract the product when the reaction is completed. The solvent can be added to the reaction system together with the reactants, or gradually added to the reaction system during the reaction. In some embodiments, the solvent is n-hexane. In some embodiments, the addition amount of the solvent is 1 to 2 times to the mass of the raw material glycerides.

[0025] In some embodiments, after the catalytic reaction, the soap in the organic phase is removed by silica gel adsorption and then the concentration step can be performed. For example, after the catalytic reaction, centrifugation may be performed, and then the soap in the organic phase can be removed by silica gel adsorption. According to some embodiments, the excess fatty acids are removed after the catalytic reaction. Preferably, molecular distillation is performed to remove the excess fatty acids.

[0026] It should be noted that for calculating the addition amounts, the mass ratio of the saturated fatty acid to the glyceride can be based on the ratio of the iodine value of the glyceride to the expected iodine value of the product, so that the mass ratio of the saturated fatty acid to the glyceride is not less than the ratio of the iodine value of the glyceride to the expected iodine value of the product minus one. Some embodiments of the present disclosure provide a method for lowering the iodine value of glycerides, which comprises: enabling glycerides containing palmitic acid residues, palmitic acid and alkalis to undergo a catalytic reaction under the action of non-specific lipase to obtain tripalmitin with low iodine value. The glyceride used as raw material is triglycerides.

[0027] In some embodiments, the glyceride with low iodine value can also be used to synthesize USU-type triglycerides, such as 1,3-dioleic acid 2-palmitic acid triglyceride (OPO).

[0028] The method can be that the prepared glyceride with low iodine value and unsaturated fatty acid or unsaturated fatty acid glyceride are subjected to Sn-1.3 enzymatic directed reaction under the catalysis of sn-1,3 specific lipase to prepare USU-type triglycerides.

[0029] The features and performance of the present disclosure will be further described in detail below in conjunction with examples.

[0030] Example 1

[0031] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 90%. 10OOg palm oil stearin and 1000ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid and sodium methoxide. The molar ratio of sodium methoxide and palmitic acid is 0.02.

[0032] Then, after nitrogen gas was introduced, the temperature of the water bath was 350 C, and the stirring speed was 400 r/min. After stirring until uniform, 5g of non-specific lipase Lipase DF "Amano" 15 was added, and the reaction was stirred for 4 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 88.5%.

[0033] Wherein, the palm oil used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 7.5.

[0034] Example 2

[0035] Palmitic acid and stearic acid were weighed out according to the amount of palmitic acid residues and stearic acid residues of palm oil to keep the ratio of palmitic acid residues and stearic acid residues to the total fatty acid residues in the reaction system was 92%. 1000g palm oil stearin and 1200ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid, stearic acid and NaOH. The molar ratio of palmitic acid, stearic acid and NaOH is 8:2:0.1. After nitrogen gas was introduced, the temperature of the water bath was 400 C, and the stirring speed was 350 r/min. After stirring until uniform, 1Og of non-specific lipase LipaseAY30G5 was added, and the reaction was stirred for 1 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 87.8%.

[0036] Wherein, the palm oil used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 7.1.

[0037] Example 3

[0038] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 94%. 1000g palm oil stearin and 1500ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid and potassium hydroxide. The molar ratio of potassium hydroxide and palmitic acid is 0.025.

[0039] Then, after nitrogen gas was introduced, the temperature of the water bath was 850 C, and the stirring speed was 500 r/min. After stirring until uniform, 50g of non-specific lipase Novozym 435 was added, and the reaction was stirred for 1 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 91.3%.

[0040] Wherein, the palm oil used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 7.3.

[0041] Example 4

[0042] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 94%. 10OOg palm oil stearin and 2000ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid and sodium ethoxide. The molar ratio of sodium ethoxide and palmitic acid is 0.00125.

[0043] Then, after nitrogen gas was introduced, the temperature of the water bath was 650 C, and the stirring speed was 400 r/min. After stirring until uniform, 40g of non-specific lipase LipozymeTLIM was added, and the reaction was stirred for 2 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 93.1%.

[0044] Wherein, the palm oil used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 5.4.

[0045] Example 5

[0046] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 96%. 1000g palm oil stearin and 2000ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid and potassium hydroxide. The molar ratio of potassium hydroxide and palmitic acid is 0.016.

[0047] Then, after nitrogen gas was introduced, the temperature of the water bath was 400 C, and the stirring speed was 380 r/min. After stirring until uniform, 1Og of non-specific lipase Lipase DF "Amano" 15 was added, and the reaction was stirred for 2 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 93.8%.

[0048] Wherein, the palm oil used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 6.2.

[0049] Example 6

[0050] Lauric acid was weighed out according to the amount of lauric acid residues of palm kernel oil to keep the ratio of lauric acid residues to the total fatty acid residues in the reaction system was 90%. 1OOOg palm kernel oil and 1000ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil dissolved, and then mixed with the lauric acid and potassium methoxide. The molar ratio of potassium methoxide and lauric acid is 0.016.

[0051] Then, after nitrogen gas was introduced, the temperature of the water bath was 850 C, and the stirring speed was 400 r/min. After stirring until uniform, 80g of non-specific lipase Novozym 435 was added, and the reaction was stirred for 0.5 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 89.5%.

[0052] Wherein, the palm kernel oil used for the reaction has an iodine value of 30, and the glyceride product obtained after the reaction has an iodine value of 7.2.

[0053] Example 7

[0054] Lauric acid was weighed out according to the amount of lauric acid residues of palm kernel oil to keep the ratio of lauric acid residues to the total fatty acid residues in the reaction system was 92%. 1OOOg palm kernel oil and 1200ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil dissolved, and then mixed with the lauric acid and potassium methoxide. The molar ratio of potassium ethoxide and lauric acid is 0.0025.

[0055] Then, after nitrogen gas was introduced, the temperature of the water bath was 350 C, and the stirring speed was 300 r/min. After stirring until uniform, 1Og of non-specific lipase Lipase DF "Amano" 15 was added, and the reaction was stirred for 2 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 91.4%.

[0056] Wherein, the palm kernel oil used for the reaction has an iodine value of 30, and the glyceride product obtained after the reaction has an iodine value of 6.4.

[0057] Example 8

[0058] Lauric acid was weighed out according to the amount of lauric acid residues of palm kernel oil to keep the ratio of lauric acid residues to the total fatty acid residues in the reaction system was 97%. 1OOOg palm kernel oil and 2000ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil dissolved, and then mixed with the lauric acid and NaOH. The molar ratio of NaOH and lauric acid is 0.0001.

[0059] Then, after nitrogen gas was introduced, the temperature of the water bath was 400 C, and the stirring speed was 350 r/min. After stirring until uniform, 1Og of non-specific lipase Lipase DF "Amano" 15 was added, and the reaction was stirred for 5 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 95.4%.

[0060] Wherein, the palm kernel oil used for the reaction has an iodine value of 30, and the glyceride product obtained after the reaction has an iodine value of 5.1.

[0061] Example 9

[0062] Stearic acid was weighed out according to the amount of stearic acid residues of cacao butter to keep the ratio of stearic acid residues to the total fatty acid residues in the reaction system was 93%. 10OOg cacao butter and 1500ml n-hexane were placed into four-necked flask with heating in a water bath until the cacao butter dissolved, and then mixed with the stearic acid and solid acid catalyst (CAS: 534-59-8). The molar ratio of solid acid catalyst and stearic acid is 0.016.

[0063] Then, after nitrogen gas was introduced, the temperature of the water bath was 400 C, and the stirring speed was 400 r/min. After stirring until uniform, 5g of non-specific lipase Lipase DF "Amano" 15 was added, and the reaction was stirred for 2 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 91.1%.

[0064] Wherein, the cacao butter used for the reaction has an iodine value of 28, and the glyceride product obtained after the reaction has an iodine value of 5.8.

[0065] Example 10

[0066] Stearic acid was weighed out according to the amount of stearic acid residues of cacao butter to keep the ratio of stearic acid residues to the total fatty acid residues in the reaction system was 93%. 1000g cacao butter and 1500ml n-hexane were placed into four-necked flask with heating in a water bath until the cacao butter dissolved, and then mixed with the stearic acid and potassium hydroxide. The molar ratio of potassium hydroxide and stearic acid is 0.001.

[0067] Then, after nitrogen gas was introduced, the temperature of the water bath was 750 C, and the stirring speed was 440 r/min. After stirring until uniform, 60g of non-specific lipase Novozym 435 was added, and the reaction was stirred for 1 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 92.3%.

[0068] Wherein, the cacao butter used for the reaction has an iodine value of 28, and the glyceride product obtained after the reaction has an iodine value of 6.0.

[0069] Example 11

[0070] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil stearin to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 85%. 1000g palm oil stearin and 2000ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid and potassium hydroxide. The molar ratio of potassium hydroxide and palmitic acid is 0.016.

[0071] Then, after nitrogen gas was introduced, the temperature of the water bath was 400 C, and the stirring speed was 380 r/min. After stirring until uniform, 1Og of non-specific lipase Lipase DF "Amano" 15 was added, and the reaction was stirred for 2 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 80.4%.

[0072] Wherein, the palm oil stearin used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 19.

[0073] Example 12

[0074] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil stearin to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 94%. 1OOOg palm oil stearin was placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid and potassium hydroxide. The molar ratio of potassium hydroxide and palmitic acid is 0.025.

[0075] Then, after nitrogen gas was introduced, the temperature of the water bath was 850 C, and the stirring speed was 500 r/min. After stirring until uniform, 50g of non-specific lipase Novozym 435 was added, and the reaction was stirred for 1 hours with heat preservation. After extraction with 2000mL n-hexane, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 88.2%.

[0076] Wherein, the palm oil stearin used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 20.3.

[0077] Example 13

[0078] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 96%. 1000g palm oil stearin and 2000ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid and potassium hydroxide. The molar ratio of potassium hydroxide and palmitic acid is 0.016. Then, after nitrogen gas was introduced, the temperature of the water bath was 650 C, and the stirring speed was 380 r/min. After stirring until uniform, 60g of immobilized 1, 3 specific lipase Lipozyme RMIM was added, and the reaction was stirred for 2 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 76.6%.

[0079] Wherein, the palm oil used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 19.2.

[0080] Example 14

[0081] The only difference between Example 14 and Example 5 is that the amount of the non-specific lipase Lipase DF "Amano" 15 added is 0.5 g. The iodine value of the glyceride product obtained after the reaction was 13.1.

[0082] Example 15

[0083] The only difference between Example 15 and Example 5 is that the amount of the non-specific lipase Lipase DF "Amano" 15 added is 100 g. The iodine value of the glyceride product obtained after the reaction was 6.0.

[0084] Example 16

[0085] The only difference between Example 16 and Example 5 is that the temperature of the water bath for the catalytic reaction is 300 C. The iodine value of the glyceride product obtained after the reaction was 14.2.

[0086] Example 17

[0087] The only difference between Example 17 and Example 5 is that the temperature of the water bath for the catalytic reaction is 900 C. The iodine value of the glyceride product obtained after the reaction was 30.4.

[0088] Comparative example 1

[0089] 30kg palmitic acid stearin was weighed out and placed into a 100L pilot reactor, 5kg sodium palmitate was added, heated and stirred while nitrogen gas introduced. The reaction temperature was kept at 1800 C, and the stirring speed was 300 r/min. The reaction was stirred for 12 hours. Then the reaction system was cooled down to 50°C. N-hexane was added to dissolve solid. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption. Light yellow solid was obtained by concentration process. The palmitic acid content at the sn-2 position is 63.6%.

[0090] Wherein, the palm oil stearin used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 24.8.

[0091] Comparative example 2

[0092] 30kg palmitic acid stearin was weighed out and placed into a 100L pilot reactor, 5kg sodium palmitate was added, heated and stirred while nitrogen gas introduced. The reaction temperature was kept at 1850 C, and the stirring speed was 400 r/min. The reaction was stirred for 20 hours. Then the reaction system was cooled down to 50°C. N-hexane was added to dissolve solid, and water was added to adsorb soap, then the mixture was filtered. The soap in the organic phase was removed by silica gel adsorption. Light yellow solid was obtained by concentration process. The palmitic acid content at the sn-2 position is 64.2%.

[0093] Wherein, the palm oil stearin used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 23.2.

[0094] Comparative example 3

[0095] Palmitic acid was weighed out according to the amount of palmitic acid residues of palm oil to keep the ratio of palmitic acid residues to the total fatty acid residues in the reaction system was 96%. 1000g palm oil stearin and 1500ml n-hexane were placed into four-necked flask with heating in a water bath until the palm oil stearin dissolved, and then mixed with the palmitic acid. Then, after nitrogen gas was introduced, the temperature of the water bath was 400 C, and the stirring speed was 380 r/min. After stirring until uniform, 10g of non-specific lipase Lipase DF "Amano" 15 was added, and the reaction was stirred for 1.5 hours with heat preservation. The supernatant of the organic phase was obtained by centrifugation, the soap in the organic phase was removed by silica gel adsorption, and free fatty acids were removed by molecular distillation to obtain a light yellow solid. The palmitic acid content at the sn-2 position is 78%.

[0096] Wherein, the palm oil used for the reaction has an iodine value of 35, and the glyceride product obtained after the reaction has an iodine value of 17.

[0097] According to Example 1 to Example 10, it can be proved that the purity of the trisaturated fatty acid glycerides prepared by the embodiments of the present disclosure is all over 80% with mild reaction conditions and few side reactions. Through the comparison of Example 5 and Example 11, the addition amount of saturated fatty acid has a greater impact on the purity of the obtained trisaturated fatty acid glycerides. When the addition amount makes the ratio of saturated fatty acid residues to the total fatty acid residues in the reaction system was 90%, products with higher purity can be obtained. By comparing Example 3 and Example 12, adding a solvent into the reaction system is beneficial to the effect of catalyzing the reaction and improving the purity of the product. According to the comparison between Example 5 and Example 13, the non-specific lipase has a better catalytic effect than the specific lipase in the method of the embodiments of the present disclosure. By comparing Example 5 with Examples 14 and 15, it is not that the more lipase is added, the lower the iodine value of the products is. By comparing Example 5 with Example 16 and Example 17, the catalytic reaction effect will be significantly worsened if the temperature is too high or too low. According to Examples 1-10 with Comparative Examples 1-3, compared with the production of trisaturated fatty acid glycerides only under the chemical catalysis of fatty acid salts or the action of lipase, the method in the embodiments of the present disclosure has milder reaction conditions, few side reactions, and greatly improved purity.

[0098] In summary, on the basis of saturated fatty acid residues contained in the glyceride, a sufficient amount of saturated fatty acid residues are provided by the saturated fatty acid salt in-situ formed by the corresponding saturated fatty acid and the alkali with catalysis of the lipase to achieve mild reaction conditions, few side reactions, and low iodine value of the resulting glyceride.

[0099] The embodiments described above are part of the embodiments of the present disclosure, rather than all of the embodiments. The detailed description of the embodiments of the disclosure is not intended to limit the scope of the claims, but merely represents selected embodiments of the disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present disclosure.

Claims

What is claimed is: 1. A method for lowering an iodine value of a glyceride, comprising: enabling a glyceride, a saturated fatty acid, and an alkali to undergo a catalytic reaction under action of a lipase, wherein a ratio of saturated fatty acid residues to total fatty acid residues in a reaction system of the glyceride and the saturated fatty acid is greater than or equal to 90%, an addition amount of the lipase ranges from 0.05 to 10% of the glyceride, and the lipase is a non-specific lipase.
2. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein temperature of the catalytic reaction ranges from 30 to 90°C, and time of the catalytic reaction ranges from 0.5 to 9 hours.
3. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein the glyceride is a glyceride containing a saturated fatty acid residue.
4. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein the iodine value of the glyceride is greater than 20.
5. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein at least a saturated fatty acid corresponding to saturated fatty acid residues contained in the glyceride is equivalent to the saturated fatty acid.
6. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein the glyceride is at least one of monoglyceride, diglyceride and triglyceride.
7. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein the saturated fatty acid is selected from at least one of palmitic acid, stearic acid, caprylic acid, capric acid, lauric acid, myristic acid and arachidic acid.
8. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein a molar ratio of the alkali to the saturated fatty acid is not greater than 1.
9. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein enabling undergoing the catalytic reaction comprises steps of mixing the glyceride with the saturated fatty acid and the alkali, adding the lipase, and stirring under a condition of introducing inert gas.
10. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein the reaction system further comprises a solvent.
11. The method for lowering the iodine value of the glyceride as claimed in claim , wherein the solvent is n-hexane.
12. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein a ratio of saturated fatty acid residues to total fatty acid residues in a reaction system of the glyceride and the saturated fatty acid is greater than 92%.
13. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein a ratio of saturated fatty acid residues to total fatty acid residues in a reaction system of the glyceride and the saturated fatty acid is greater than 95%.
14. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein an addition amount of the lipase ranges from 0.1 to 8% of the glyceride.
15. The method for lowering the iodine value of the glyceride as claimed in claim 1, wherein temperature of the catalytic reaction ranges from 35 to 85°C, and the time of catalytic reaction ranges from 1 to 4 hours.