Preparation method and application of stable diglyceride oil

Abstract

The invention belongs to the field of light industry grease, and particularly relates to a preparation method and application of stable diglyceride oil. The method comprises the following steps: performing moderate glycerolysis on vegetable oil; crude diglyceride obtained through glycerolysis is firstly subjected to molecular distillation purification and then subjected to a fractionation modification process, and the diglyceride isomer composition is prepared by controlling the glycerolysis degree and the fractionation process. The oxidation stability of the hot-processing cooking oil is remarkably improved, and the production amount of risk factors is remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the field of light industry food oils and fats, and specifically relates to a preparation method and application of stable diglyceride oil. Background Art

[0002] Diacylglycerol (DAG) has attracted wide attention as a functional food ingredient. Different from triglycerides (TAG), DAG oil is believed to reduce body fat accumulation, reduce postprandial serum TAG levels, reduce obesity and cardiovascular diseases, etc. At present, DAG is mainly used in the food industry as an emulsifier, crystal modifier, and baking product regulator. During high-temperature cooking, edible oil undergoes a series of physical and chemical changes in a short period of time due to its large specific surface area, resulting in changes in its color, peroxide value, anisidine value, tocopherols and phytosterols, and is also accompanied by the production of harmful substances, such as 3-chloropropanediol esters (3-MCPDE) and glycidyl esters (GEs). In different vegetable oil systems, various substances have certain differences in their antioxidant effects on oils. Under high-temperature conditions, the antioxidant capacity of edible oil during cooking is mainly determined by its fatty acid composition and antioxidant concentration. Natural antioxidants in edible oil, such as tocotrienols and tocopherols, can effectively inhibit the oxidation process of oils to a certain extent. The oxidation of phytosterols is affected by many factors, including temperature, free radical initiators and oxygen, and the derived sterol oxides have been shown to have toxic side effects such as carcinogenicity and mutagenicity. Therefore, the oxidative stability of edible oil has an important impact on the storage and cooking process. At present, there is still much controversy about the effect of DAG on the oxidative stability of oil. It is generally believed that the thermal stability of TAG oil is much higher than that of DAG oil.

[0003] At present, the oxidative stability of DAG oil is usually enhanced by adding antioxidants, or selecting raw oil with high saturation, or by embedding and powdering DAG oil in the later stage to improve the stability during application. At present, it is generally believed in academia that the formation of 3-MCPDE and GEs during the thermal processing of oils and fats is related to TAG and some glycerides, including DAG and MAG. Studies have also shown that the concentration of 3-MCPDE is proportional to the heating temperature, but when the temperature is higher than 220°C, the generation rate of 3-MCPDE decreases. The heating time has different effects on the formation trend of 3-MCPDE and GEs. Some studies have found that a large amount of 3-MCPDE will be produced in the early stage of thermal processing. As time goes on, 3-MCPDE is in a fluctuating change, the degradation rate is higher than the generation rate, and the GEs concentration decreases with the extension of thermal processing time. In other studies, the GEs concentration is proportional to the thermal processing time. Therefore, 3-MCPDE and GEs tend to be unstable during long-term heating. In addition, the chloride content, antioxidants and oil types may be correlated with the formation of 3-MCPDE and GEs. Summary of the invention

[0004] In view of the problems that diglyceride oil has poor oxidative stability during thermal processing and product quality changes with high growth rates of risk factors such as 3-MCPDE and GEs, the purpose of the present invention is to provide a preparation method for high-stability diglyceride oil through glycerol hydrolysis and fractionation processes. The diglyceride oil obtained by the method has significantly improved oxidative stability (low growth rates of acid value AV and total oxidation value TOTOX) during thermal processing without adding antioxidants, and the growth rate of risk factors is greatly reduced.

[0005] Another object of the present invention is to provide a high-stability diglyceride oil prepared by the above method.

[0006] Another object of the present invention is to provide an application of the high-stability diglyceride oil prepared by the above method.

[0007] The purpose of the present invention is achieved through the following technical solutions: A method for preparing a stable diglyceride oil comprises the following steps: (1) Glycerolizing the vegetable oil, collecting the oil sample, and purifying the oil by molecular distillation to obtain the raw material diglyceride oil; (2) Dry fractionating the raw material diglyceride oil, collecting the fractionated oil (low melting point component), and obtaining the stable diglyceride oil.

[0008] The vegetable oil in step (1) is a vegetable oil with a sliding melting point ≥ 4°C, preferably peanut oil.

[0009] The glycerolysis in step (1) is enzymatic glycerolysis, the enzyme is a lipase, preferably one of the lipases LipozymeCALB, Lipozyme TL IM or Lipozyme RM IM; the mass ratio of vegetable oil to glycerol in the glycerolysis is 2:1-1:1; the amount of enzyme added is 1-5% of the mass of the substrate (vegetable oil + glycerol), the temperature of the glycerolysis reaction is 60-80°C (preferably 60-75°C), the reaction time is 30-90 min, and the vacuum degree is ≤2000 Pa.

[0010] Preferably, in the enzymatic glycerolysis in step (1), the mass ratio of vegetable oil to glycerol is 2:1, the amount of enzyme added is 2% of the mass of the substrate, the temperature of the glycerolysis reaction is 70° C., and the reaction time is 40 min.

[0011] The molecular distillation purification in step (1) obtains raw material diglyceride oil in the light phase, wherein the diglyceride content is 80-100%.

[0012] The molecular distillation of step (1) is operated according to the following parameters: distillation temperature is 180-190°C, vacuum degree is 0.5-1.0 Pa, scraper speed is 150-200 rpm, condenser temperature is 30-50°C, and feed flow rate is ≤0.5 mL / min.

[0013] The specific steps of the fractionation in step (2) are as follows: melting the raw material diglyceride oil, and then stirring and immersing it at 5-10°C for more than 90 minutes to wait for the solid matter to precipitate, with the stirring speed being less than 200 rpm; after the stirring and immersion is completed, suction filtration is performed to separate the solid part and the liquid part; the fractionated liquid oil (low melting point component) is collected, and the 1,3 diglyceride:1,2 diglyceride in the diglyceride product is controlled to be 6:4~8:2 (mass ratio), so as to obtain the stable diglyceride oil.

[0014] The diglyceride oil prepared by the method of the present invention is heated at 180° C. for 120 min, and has a total oxidation value of less than 120, a peroxide value of less than 13.0 mmol / kg, an acid value of ≤0.9 mg / g, a 3MCPDE content of less than 210 ug / kg, and a GEs content of less than 200 ug / kg. The 3MCPDE content growth rate is ≤34%; the GEs content growth rate is ≤81.4%, preferably ≤25.8%.

[0015] In order to obtain a more stable diglyceride oil, the present invention uses peanut oil as raw material, adopts an enzymatic glycerolysis process, controls the degree of acyl migration in the glycerolysis process, obtains a crude diglyceride product, and performs molecular distillation purification and fractionation on the crude diglyceride product to further obtain a diglyceride oil with a suitable isomer ratio. The diglyceride oil with a suitable isomer ratio has greatly improved oxidative stability during thermal processing and cooking compared with the diglyceride oil obtained by traditional glycerolysis, and the rate of risk factor generation is significantly reduced.

[0016] A stable diglyceride oil prepared by the method.

[0017] The above-mentioned stable diglyceride oil is used as thermal processing cooking oil.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention is the first to utilize the control of the degree of glycerol hydrolysis and the fractionation process to achieve the preparation of a diglyceride isomer composition. Compared with other processes, the diglyceride oil of the present invention controls the degree of glycerol hydrolysis, the fractionation conditions, especially the diglyceride content and the 1,3 / 1,2 diglyceride ratio. As a thermally processed cooking oil, the oxidative stability is significantly improved and the production of risk factors is significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is the total oxidation value after heat treatment of the embodiments of the present invention and the comparative examples, and the change in the growth rate of the total oxidation value before and after heat treatment. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically noted, conventional techniques can be used. The lipases used in the examples were purchased from Novozymes. The peanut oil used in the examples was purchased from Golden Dragon Fish Peanut Oil of Yihai Kerry Golden Dragon Fish Cereals, Oils and Foods Co., Ltd.

[0021] The present invention aims to realize the preparation of diglyceride isomer composition by controlling the degree of glycerol hydrolysis and fractionation process. Compared with other processes, the diglyceride oil of the present invention controls the degree of glycerol hydrolysis, fractionation conditions, especially the diglyceride content and the 1,3 / 1,2 diglyceride ratio. As a hot processing cooking oil, the oxidative stability is significantly improved and the production of risk factors is significantly reduced. The experimental data and comparative test data of the characteristic analysis of the diglyceride oil are studied in the following examples, and the method is as follows: (1) Heat treatment In the static heating process, 300 mL of oil sample was heated to 180 °C in a 500 mL triangular round bottom flask. The temperature was maintained for 120 min and collected for further analysis. All samples were stored at -20 °C before measurement.

[0022] (2) Determination of diglyceride content A capillary column DB-1HT (15 m × 0.25 mm × 0.1 μm) was used from Agilent Technologies (Palo Alto, CA). The oven temperature was maintained at 380 °C and the pressure was maintained at 20.0 psi, using nitrogen as the carrier gas with a flow rate of 4.41 mL / min and a constant flow pressure of 30.0 psi. The sample was dissolved in 2 mL of n-hexane and filtered through a 0.45 μm filter. The injection and detector temperatures were set to 380 °C using a 20:1 split mode and an injection volume of 0.5 μL. The initial oven temperature was set to 50 °C for 1 min. It was then increased to 100 °C for 2 min, then to 220 °C at a rate of 80 °C / min, and finally to 380 °C at a rate of 50 °C / min for 3 min. The yield of each type of acylglycerol was expressed as a percentage of the peak area.

[0023] (3) Determination of diglyceride isomer content use 1The isomer ratio of 1,3 DAG to 1,2 DAG in the sample was determined by H-NMR technology: 20 mg of sample was weighed and 0.5 mL of CDCl was used to measure the isomer ratio of 1,3 DAG to 1,2 DAG. 3 The samples before and after purification were dissolved, and then the dissolved samples were transferred to the NMR tube for testing. The test conditions were: acquisition time 3.17 s, scan number 80, pulse width 12.76 μs, spectrum width 10330.6 Hz, temperature 25°C.

[0024] (4) Determination of acid value AV, peroxide value PV, and total oxidation value TOTOX AV, PV, and p-AV were determined according to AOCS official methods Cd 3d-63, Cd 8-53, and Cd 18-90, respectively. To determine AV, 10 g of oil sample was dissolved in a conical flask filled with a petroleum ether-ethanol mixture (1:1 v / v, 100 mL), a few drops of phenolphthalein indicator were added, and titrated with potassium hydroxide standard solution (0.1 M).

[0025] To determine PV, 5 g of oil sample was dissolved in a conical flask containing glacial acetic acid-chloroform solution (3:2 v / v, 30 mL), 0.5 mL of saturated potassium iodide solution was added and shaken, allowed to stand for 1 min, and then 30 mL of distilled water was added. Titration was performed with sodium thiosulfate solution (0.01 M).

[0026] The TOTOX value is the best indicator to measure the overall oxidation state of the oil. The calculation formula is as follows: TOTOX=4*PV+p-AV (1) Wherein, PV represents PV value (mmol / kg), p -AV indicates p-AV value.

[0027] (5) Measurement of risk factors (3-MCPDE, GEs) 3-MCPDE and GEs of oil samples were analyzed according to AOCS official method Cd 29a-13. The oil samples were weighed and dissolved by adding d5-3-MCPDE standard and tert-butyl methyl ether-ethyl acetate. After that, methanol-sodium methoxide was added for hydrolysis, followed by purification using acidified sodium chloride and n-hexane. Next, ethyl acetate was added for extraction, followed by derivatization with phenylboronic acid and nitrogen drying, and then redissolved with isooctane. The samples were filtered with a membrane and analyzed by GCMS. The chromatographic conditions were: injection volume of 1 μL, nitrogen flow rate of 1.18 mL / min, column initial temperature of 80°C, and the temperature was raised to 300°C by program. The mass spectrometry conditions were: EI+SIM mode.

[0028] Example 1 (1) Weigh 100 g peanut oil and 60 g glycerol, heat and melt them until they are evenly mixed, then place them in a reactor and set the reaction temperature to 75°C. When the temperature is constant, add 2.5 g lipase Lipozyme CALB and stir with a magnetic stirrer (speed 500 r / min). The reaction is carried out under vacuum conditions (absolute pressure = 5000 Pa) with a water circulation pump to allow the oil and enzyme to fully react and complete the ester exchange. After 60 minutes of reaction, the reaction solution is centrifuged to remove the glycerol layer and lipase, and the oil sample is collected as crude diglyceride oil.

[0029] (2) Purify the crude diglyceride oil by molecular distillation: distillation temperature is 180°C, vacuum degree is 0.5 Pa, scraper speed is 200 rpm, condenser temperature is 40°C, and feed flow rate is 0.5 mL / min. Collect the light phase oil.

[0030] (3) Weigh 100 g of purified peanut diglyceride oil sample and melt it in a beaker. Immerse the beaker in a 5°C water bath and stir for 90 min until solid matter precipitates. Stir at 100 rpm and use a Buchner funnel to filter and separate the solid and liquid parts. Collect the liquid part to obtain the final diglyceride oil sample.

[0031] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride: 1,2 diglyceride = 6.5:3.5, the initial total oxidation value of the diglyceride oil is 18.08, the peroxide value is 2.87 mmol / kg, the acid value is 0.65 mg / g, the 3MCPDE content is 179 ug / kg, the GEs content = 97 ug / kg, and after heating at 180°C for 120 min, the total oxidation value = 108.5, the peroxide value = 10.7 mmol / kg, the acid value = 0.70 mg / g, the 3MCPDE content = 184ug / kg, and the GEs content = 122 ug / kg.

[0032] Example 2 This embodiment is the same as Embodiment 1 except for the following technical features: In step (1), the reaction temperature is set to 60° C. and the reaction time is 60 min.

[0033] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=6:4, the initial total oxidation value of the diglyceride oil is 17.58, the peroxide value is 2.89 mmol / kg, the acid value is 0.58 mg / g, the 3MCPDE content is 170 ug / kg, and the GEs content is 109 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 98.0, the peroxide value is 9.3 mmol / kg, the acid value is 0.90 mg / g, the 3MCPDE content is 177 ug / kg, and the GEs content is 123ug / kg.

[0034] Example 3 This embodiment is the same as Embodiment 1 except for the following technical features: In step (1), the reaction temperature is set to 80° C. and the reaction time is 60 min.

[0035] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=7.2:2.8, the initial total oxidation value of the diglyceride oil is 18.10, the peroxide value is 2.99 mmol / kg, the acid value is 0.70 mg / g, the 3MCPDE content is 133 ug / kg, and the GEs content is 102 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 108.7, the peroxide value is 7.0 mmol / kg, the acid value is 0.80 mg / g, the 3MCPDE content is 151ug / kg, and the GEs content is 185 ug / kg.

[0036] Example 4 This embodiment is the same as Embodiment 1 except for the following technical features: In step (1), the reaction temperature is set to 75° C. and the reaction is carried out for 30 min.

[0037] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=7:3, the initial total oxidation value of the diglyceride oil is 16.22, the peroxide value is 2.73mmol / kg, the acid value is 0.72mg / g, the 3MCPDE content is 153 ug / kg, and the GEs content is 111 ug / kg. The diglyceride oil is heated at 180°C for 120min, the total oxidation value is 85.5, the peroxide value is 8.9 mmol / kg, the acid value is 0.90 mg / g, the 3MCPDE content is 189ug / kg, and the GEs content is 121ug / kg.

[0038] Example 5 This embodiment is the same as Embodiment 1 except for the following technical features: In step (1), the reaction temperature is set to 75° C. and the reaction time is 90 min.

[0039] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=7.9:2.1, the initial total oxidation value of the diglyceride oil is 19.21, the peroxide value is 3.08 mmol / kg, the acid value is 0.69 mg / g, the 3MCPDE content is 141 ug / kg, and the GEs content is 155 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 96.5, the peroxide value is 7.5 mmol / kg, the acid value is 0.80 mg / g, the 3MCPDE content is 154ug / kg, and the GEs content is 182ug / kg.

[0040] Example 6 This embodiment is the same as embodiment 1 except for the following technical features: the fractionation temperature in step (3) is 10°C.

[0041] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=6.2:3.8, the initial total oxidation value of the diglyceride oil is 21.00, the peroxide value is 3.1 mmol / kg, the acid value is 0.60 mg / g, the 3MCPDE content is 156 ug / kg, and the GEs content is 100 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 98.0, the peroxide value is 9.1 mmol / kg, the acid value is 0.7 mg / g, the 3MCPDE content is 188 ug / kg, and the GEs content is 118 ug / kg.

[0042] Example 7 This embodiment is the same as Embodiment 1 except for the following technical features: In step (1), the lipase is Lipozyme RM IM.

[0043] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=6.5:3.5, the initial total oxidation value of the diglyceride oil is 22.09, the peroxide value is 2.82 mmol / kg, the acid value is 0.54 mg / g, the 3MCPDE content is 151 ug / kg, and the GEs content is 166 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 120.0, the peroxide value is 8.2 mmol / kg, the acid value is 0.6 mg / g, the 3MCPDE content is 167ug / kg, and the GEs content is 199ug / kg.

[0044] Example 8 This embodiment is the same as Embodiment 1 except for the following technical features: The extraction time in step (3) is 120 min.

[0045] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=7.1:2.9, the initial total oxidation value of the diglyceride oil is 19.19, the peroxide value is 2.28 mmol / kg, the acid value is 0.71 mg / g, the 3MCPDE content is 101 ug / kg, and the GEs content is 156 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 111.0, the peroxide value is 11.5 mmol / kg, the acid value is 0.9 mg / g, the 3MCPDE content is 110ug / kg, and the GEs content is 160 ug / kg.

[0046] Example 9 This embodiment is the same as Embodiment 1 except for the following technical features: In step (1), the amount of lipase added is 5 g.

[0047] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=8:2, the initial total oxidation value of the diglyceride oil is 19.90, the peroxide value is 2.97 mmol / kg, the acid value is 0.61 mg / g, the 3MCPDE content is 94 ug / kg, and the GEs content is 124 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 107.0, the peroxide value is 11.4 mmol / kg, the acid value is 0.7 mg / g, the 3MCPDE content is 100.5ug / kg, and the GEs content is 154 ug / kg.

[0048] Example 10 This embodiment is the same as Embodiment 1 except for the following technical features: In step (1), the amount of glycerol added is 100 g.

[0049] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=6.2:3.8, the initial total oxidation value of the diglyceride oil is 19.22, the peroxide value is 2.88 mmol / kg, the acid value is 0.60 mg / g, the 3MCPDE content is 144 ug / kg, and the GEs content is 113 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 120.0, the peroxide value is 8.6 mmol / kg, the acid value is 0.7 mg / g, the 3MCPDE content is 193ug / kg, and the GEs content is 128ug / kg.

[0050] Embodiment 11 This embodiment is the same as Embodiment 1 except for the following technical features: The distillation temperature in step (2) is 190°C.

[0051] It has been calculated that the diglyceride content in the diglyceride oil product is 92%, of which 1,3 diglyceride:1,2 diglyceride=6.6:3.4, the initial total oxidation value of the diglyceride oil is 29.22, the peroxide value is 2.9 mmol / kg, the acid value is 0.63 mg / g, the 3MCPDE content is 155 ug / kg, and the GEs content is 102 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 100.5, the peroxide value is 8.7 mmol / kg, the acid value is 0.7 mg / g, the 3MCPDE content is 171ug / kg, and the GEs content is 123ug / kg.

[0052] Comparative Example 1 This comparative example is the same as Example 1 except for the following technical features: In step (2), the reaction temperature is set at 50° C. and the reaction is carried out for 60 min.

[0053] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride: 1,2 diglyceride = 5.5:4.5, the initial total oxidation value of the diglyceride oil is 21.22, the peroxide value is 2.93 mmol / kg, the acid value is 0.60 mg / g, the 3MCPDE content is 155 ug / kg, and the GEs content is 120 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value = 138.0, the peroxide value = 17.3 mmol / kg, the acid value = 1.3 mg / g, the 3MCPDE content = 370ug / kg, and the GEs content = 300 ug / kg.

[0054] Comparative Example 2 This comparative example is the same as Example 1 except for the following technical features: Step (1) the reaction temperature is set to 55°C and the reaction is carried out for 60 minutes.

[0055] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=5.9:4.1, the initial total oxidation value of the diglyceride oil is 20.96, the peroxide value is 3.11 mmol / kg, the acid value is 0.71 mg / g, the 3MCPDE content is 148 ug / kg, and the GEs content is 150 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 158.7, the peroxide value is 19.0 mmol / kg, the acid value is 1.8 mg / g, the 3MCPDE content is 350 ug / kg, and the GEs content is 285 ug / kg.

[0056] Comparative Example 3 This comparative example is the same as Example 1 except for the following technical features: Step (1) the reaction temperature is set to 75°C and the reaction is carried out for 10 minutes.

[0057] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=4:6, the initial total oxidation value of the diglyceride oil is 28.88, the peroxide value is 3.09 mmol / kg, the acid value is 0.62 mg / g, the 3MCPDE content is 168 ug / kg, and the GEs content is 110 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 230.0, the peroxide value is 19.9 mmol / kg, the acid value is 1.9 mg / g, the 3MCPDE content is 489ug / kg, and the GEs content is 310 ug / kg.

[0058] Comparative Example 4 This comparative example is the same as Example 1 except for the following technical features: Step (1) the reaction temperature is set to 75°C and the reaction is carried out for 120 minutes.

[0059] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=8.2:1.8, the initial total oxidation value of the diglyceride oil is 31.00, the peroxide value is 3.22mmol / kg, the acid value is 0.60mg / g, the 3MCPDE content is 159 ug / kg, and the GEs content is 101 ug / kg. The diglyceride oil is heated at 180°C for 120min, the total oxidation value is 136.5, the peroxide value is 17.5 mmol / kg, the acid value is 1.2 mg / g, the 3MCPDE content is 354ug / kg, and the GEs content is 182 ug / kg.

[0060] Comparative Example 5 This comparative example is the same as Example 1 except for the following technical features: the fractionation temperature in step (3) is 15°C.

[0061] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride: 1,2 diglyceride = 5.5:4.5, the initial total oxidation value of the diglyceride oil is 28.10, the peroxide value is 2.77 mmol / kg, the acid value is 0.55 mg / g, the 3MCPDE content is 144 ug / kg, and the GEs content is 112 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value = 148.0, the peroxide value = 19.1 mmol / kg, the acid value = 1.7 mg / g, the 3MCPDE content = 380ug / kg, and the GEs content = 218 ug / kg.

[0062] Comparative Example 6 This comparative example is the same as Example 1 except for the following technical features: in step (1), the catalyst is NaOH, the addition amount is 0.5% of the substrate mass, the reaction temperature is 180° C., and the reaction time is 120 min.

[0063] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride:1,2 diglyceride=7:3, the initial total oxidation value of the diglyceride oil is 29.05, the peroxide value is 2.60mmol / kg, the acid value is 0.60mg / g, the 3MCPDE content is 149 ug / kg, and the GEs content is 110 ug / kg. The diglyceride oil is heated at 180°C for 120min, the total oxidation value = 210.0, the peroxide value = 25.2 mmol / kg, the acid value = 1.1 mg / g, the 3MCPDE content = 575ug / kg, and the GEs content = 490 ug / kg.

[0064] Comparative Example 7 This comparative example is the same as Example 1 except for the following technical features: step (3) is not subjected to fractionation.

[0065] It has been calculated that the diglyceride content in the diglyceride oil product is 85%, of which 1,3 diglyceride: 1,2 diglyceride = 6.5:3.5, the initial total oxidation value of the diglyceride oil is 28.80, the peroxide value is 3.00 mmol / kg, the acid value is 0.62 mg / g, the 3MCPDE content is 168 ug / kg, and the GEs content is 158 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value = 138.5, the peroxide value = 17.0 mmol / kg, the acid value = 1.2 mg / g, the 3MCPDE content = 642ug / kg, and the GEs content = 900 ug / kg.

[0066] Comparative Example 8 This comparative example is the same as Example 1 except for the following technical features: In step (1), the amount of lipase added is 10 g.

[0067] It has been calculated that the diglyceride content in the diglyceride product is 85%, of which 1,3 diglyceride: 1,2 diglyceride = 8.2:1.8, the initial total oxidation value of the diglyceride oil is 28.88, the peroxide value is 3.09 mmol / kg, the acid value is 0.60 mg / g, the 3MCPDE content is 147 ug / kg, and the GEs content is 110 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value = 218.0, the peroxide value = 14.4 mmol / kg, the acid value = 0.9 mg / g, the 3MCPDE content = 400 ug / kg, and the GEs content = 354 ug / kg.

[0068] Comparative Example 9 This comparative example is the same as Example 1 except for the following technical features: In step (1), the amount of glycerol added is 30 g.

[0069] It has been calculated that the diglyceride content in the diglyceride product is 85%, of which 1,3 diglyceride: 1,2 diglyceride = 4.8:5.2, the initial total oxidation value of the diglyceride oil is 30.05, the peroxide value is 2.82 mmol / kg, the acid value is 0.52 mg / g, the 3MCPDE content is 160 ug / kg, and the GEs content is 160 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value = 130.0, the peroxide value = 19.6 mmol / kg, the acid value = 1.0 mg / g, the 3MCPDE content = 593ug / kg, and the GEs content = 428 ug / kg.

[0070] Comparative Example 10 This embodiment is the same as Embodiment 1 except for the following technical features: The distillation temperature in step (2) is 170°C.

[0071] It has been calculated that the diglyceride content in the diglyceride product is 73%, of which 1,3 diglyceride:1,2 diglyceride=6.6:3.4, the initial total oxidation value of the diglyceride oil is 28.88, the peroxide value is 3.01 mmol / kg, the acid value is 0.60 mg / g, the 3MCPDE content is 149 ug / kg, and the GEs content is 144 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 153.0, the peroxide value is 15.7 mmol / kg, the acid value is 0.7 mg / g, the 3MCPDE content is 371ug / kg, and the GEs content is 323 ug / kg.

[0072] Comparative Example 11 This embodiment is the same as Embodiment 1 except for the following technical features: The distillation temperature in step (2) is 210°C.

[0073] It has been calculated that the diglyceride content in the diglyceride product is 80%, of which 1,3 diglyceride:1,2 diglyceride=6.6:3.4, the initial total oxidation value of the diglyceride oil is 31.01, the peroxide value is 3.09 mmol / kg, the acid value is 0.69 mg / g, the 3MCPDE content is 168 ug / kg, and the GEs content is 120 ug / kg. The diglyceride oil is heated at 180°C for 120 min, the total oxidation value is 123.0, the peroxide value is 14.0 mmol / kg, the acid value is 0.9 mg / g, the 3MCPDE content is 292ug / kg, and the GEs content is 300 ug / kg.

[0074] Table 1 Comparative data of peroxide value and acid value after heat treatment of the embodiments and comparative examples used in the present invention Table 2 Comparison of thermal stability characteristics of examples and comparative examples Conclusion: After moderate glycerolysis of peanut oil to obtain peanut oil diglyceride oil, diglyceride oil is obtained after molecular distillation purification and fractionation modification. Compared with other processes, the diglyceride oil of the present invention controls the degree of glycerolysis, molecular distillation purification and fractionation conditions, especially the diglyceride content and its 1,3 / 1,2 diglyceride ratio. As a thermal processing cooking oil, the oxidative stability is significantly improved and the production of risk factors is significantly reduced.

[0075] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a stable diglyceride oil, characterized in that: The following steps are involved: (1) Glycerolizing the vegetable oil, collecting the oil sample, and purifying the oil by molecular distillation to obtain the raw material diglyceride oil; (2) Dry fractionating the raw material diglyceride oil, collecting the fractionated liquid oil, and obtaining the stable diglyceride oil.

2. The method for preparing a stable diglyceride oil according to claim 1, wherein: The vegetable oil in step (1) is a vegetable oil with a sliding melting point ≥ 4°C, preferably peanut oil.

3. The method for preparing a stable diglyceride oil according to claim 1, characterized in that: The glycerolysis in step (1) is enzymatic glycerolysis, the enzyme is one of lipase LipozymeCALB, LipozymeTL IM or Lipozyme RM IM; the mass ratio of vegetable oil to glycerol in the glycerolysis is 2:1-1:1; the amount of enzyme added is 1-5% of the substrate mass, the temperature of the glycerolysis reaction is 60-80°C, and the reaction time is 30-90 min.

4. The method for preparing a stable diglyceride oil according to claim 1, wherein: The molecular distillation purification in step (1) obtains raw material diglyceride oil in the light phase, wherein the diglyceride content is 80-100%.

5. The method for preparing a stable diglyceride oil according to claim 1, characterized in that: The molecular distillation of step (1) is operated according to the following parameters: distillation temperature is 180-190°C, vacuum degree is 0.5-1.0 Pa, scraper speed is 150-200 rpm, condenser temperature is 30-50°C, and feed flow rate is ≤0.5 mL / min.

6. The method for preparing a stable diglyceride oil according to claim 1, characterized in that: The specific steps of the fractionation in step (2) are as follows: melting the raw material diglyceride oil, and then stirring and immersing it at 5-10°C for more than 90 minutes to allow solid matter to precipitate, and after the stirring and immersion is completed, filtering to separate the solid part and the liquid part; and collecting the fractionated liquid oil.

7. The method for preparing a stable diglyceride oil according to claim 1, characterized in that: In the stable diglyceride oil, the mass ratio of 1,3 diglyceride to 1,2 diglyceride is 6:4-8:

2.

8. A stable diglyceride oil prepared according to the method according to any one of claims 1 to 7.

9. The stable diglyceride oil according to claim 8, characterized in that: After the stable diglyceride oil is heated, the 3MCPDE content growth rate is ≤34%; the GEs content growth rate is ≤81.4%, preferably ≤25.8%.

10. Use of the stable diglyceride oil according to claim 8 or 9 as thermal processing cooking oil.

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