Preparation method of diglyceride-rich rice oil

Abstract

The invention discloses a preparation method of rice oil rich in diglyceride, and the preparation method of the rice oil rich in diglyceride comprises the following steps: mixing rice oil with monoglyceride to obtain a mixed substrate; heating the mixed substrate to 50-70 DEG C, then adding lipase into the mixed substrate, stirring at 40-80 DEG C, and carrying out a lipase catalytic reaction; and after the lipase catalytic reaction is finished, centrifuging and collecting an upper-layer oil sample to obtain the rice oil rich in diglyceride. According to the method, the rice oil and the monoglyceride are used as main raw materials, the lipase is selected as a catalyst, the conversion efficiency of the diglyceride is high, the content of the diglyceride in the rice oil can be effectively increased, the nutritional characteristics of the rice oil and the functional characteristics of the diglyceride are combined, the reaction conditions are mild, the energy consumption is low, and the reaction specificity is good.

Description

Technical Field

[0001] This invention relates to the field of rice bran oil deep processing technology, specifically to a method for preparing rice bran oil rich in diglycerides. Background Technology

[0002] Diacylglycerol (DAG), commonly known as glycerol ester, is a product formed by the esterification of one or two fatty acids with hydroxyl groups at different positions in glycerol. It mainly exists in two isomers: 1,3-DAG and 1,2-DAG. It is a naturally occurring component of fats and oils, and its taste, color, and flavor characteristics are no different from ordinary triglycerides. However, it possesses unique physiological functions; therefore, diglycerides can be added as an additive to products in the food, pharmaceutical, and chemical industries.

[0003] Currently, the preparation of DAG mainly includes chemical methods and enzymatic methods. Chemical methods have the advantage of low cost, but the reaction temperature is high, there are many by-products, and the reaction lacks specificity. Enzymatic methods for preparing DAG have attracted widespread attention because of their mild reaction conditions, less environmental pollution, no need to use large amounts of organic solvents, and high safety.

[0004] Rice bran oil is high in unsaturated fatty acids, accounting for 80-85%, and also contains phytosterols, oryzanol, and other components. These components have various nutritional and health benefits for the human body, such as lowering blood lipids and preventing cardiovascular and cerebrovascular diseases. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing rice bran oil rich in diglycerides, aiming to provide a method that can increase the diglyceride content in rice bran oil.

[0006] To achieve the above objectives, this invention proposes a method for preparing rice bran oil rich in diglycerides, comprising the following steps:

[0007] Rice bran oil and monoglycerides were mixed to obtain a mixed substrate;

[0008] The mixed substrate is heated to 50-70°C, then lipase is added to it, and the mixture is stirred at 40-80°C to carry out the lipase-catalyzed reaction.

[0009] After the lipase-catalyzed reaction is completed, the sample is centrifuged and the upper oil layer is collected to obtain rice bran oil rich in diglycerides.

[0010] Optionally, the lipase includes lipase Novozym 435.

[0011] Optionally, in the step of mixing rice bran oil with monoglycerides to obtain a mixed substrate:

[0012] The molar ratio of rice bran oil to monoglyceride is 1:0.2 to 1.

[0013] Optionally, in the step of heating the mixed substrate to 50–70°C, then adding lipase, and then stirring at 40–80°C to carry out the lipase-catalyzed reaction:

[0014] The mass of the lipase is 2-8% of the mass of the mixed substrate.

[0015] Optionally, in the step of heating the mixed substrate to 50–70°C, then adding lipase, and then stirring at 40–80°C to carry out the lipase-catalyzed reaction:

[0016] The heating temperature of the mixed substrate is 60°C.

[0017] Optionally, in the step of heating the mixed substrate to 50–70°C, then adding lipase, and then stirring at 40–80°C to carry out the lipase-catalyzed reaction:

[0018] The stirring speed is 180-200 rpm and the stirring time is 6-12 h.

[0019] Optionally, after the lipase-catalyzed reaction is complete, the step of centrifuging and collecting the upper oil sample to obtain rice bran oil rich in diglycerides is as follows:

[0020] The centrifugation temperature is 18–25°C, the centrifugation speed is 5000–6000 rpm, and the centrifugation time is 15–20 min.

[0021] Optionally, after the lipase-catalyzed reaction is complete, the step of centrifuging and collecting the upper oil sample to obtain rice bran oil rich in diglycerides is as follows:

[0022] The centrifugation temperature was 20℃, the centrifugation speed was 6000 rpm, and the centrifugation time was 15 min.

[0023] The technical solution provided by this invention uses rice bran oil and monoglycerides as the main raw materials and selects lipase as a catalyst. It has a high conversion efficiency for diglycerides and can effectively increase the content of diglycerides in rice bran oil. This combines the nutritional characteristics of rice bran oil with the functional characteristics of diglycerides, further enhancing the nutritional value of rice bran oil. Moreover, the reaction conditions are mild, energy consumption is low, and the reaction specificity is good. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic flowchart of an embodiment of a method for preparing rice bran oil rich in diglycerides provided by the present invention.

[0026] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] This invention proposes a method for preparing rice bran oil rich in diglycerides. Using rice bran oil and monoglycerides as raw materials and lipase as a catalyst, the method effectively increases the diglyceride content in rice bran oil through enzymatic methods. Specifically, Figure 1 The illustration shows an embodiment of the method for preparing rice bran oil rich in diglycerides provided by the present invention. (See also...) Figure 1 As shown, in this embodiment, the preparation method of the diglyceride-rich rice bran oil includes the following steps:

[0029] Step S10: Mix rice bran oil with monoglycerides to obtain a mixed substrate;

[0030] Step S20: Heat the mixed substrate to 50-70°C, then add lipase to it, and stir at 40-80°C to carry out the lipase-catalyzed reaction;

[0031] Step S30: After the lipase-catalyzed reaction is completed, centrifuge and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0032] First, fresh rice bran oil and monoglycerides are mixed evenly to obtain a mixed substrate. Then, the mixture is heated to 50–70°C, and lipase is added to the mixed substrate. The mixture is then placed in a constant-temperature environment to allow the lipase-catalyzed reaction to produce diglycerides. After the reaction is complete, the upper oil sample is collected by centrifugation, thus obtaining rice bran oil rich in diglycerides. In the technical solution provided by this invention, rice bran oil and monoglycerides are used as the main raw materials, and lipase is selected as the catalyst. The reaction conditions are mild, energy consumption is low, and the reaction specificity is good, greatly improving the efficiency of the enzymatic reaction and effectively increasing the diglyceride content in rice bran oil. This combines the nutritional characteristics of rice bran oil with the functional characteristics of diglycerides, further enriching the nutritional value of rice bran oil.

[0033] Enzymatic esterification is an important route for synthesizing diglycerides. This method offers high esterification yield, high product purity, simple operation, and low pollution. Lipases are commonly used to catalyze the synthesis of diglycerides. Through extensive experimental research, the inventors discovered that using lipases to enzymatically hydrolyze rice bran oil can promote the conversion of more diglycerides from the oil, effectively increasing its content. Preferably, in some embodiments of this invention, the lipase includes the commercially available lipase Novozym 435. Compared to other commercial lipases, such as the lipase TLIM used in the published patent (CN107254495A) "Method for Preparing Diglycerides from Rice Bran Oil by Lipase Catalysis," Novozym 435 is more effective in improving the conversion rate and increasing the diglyceride content in rice bran oil. See the specific examples and comparative examples below for details. After enzymatic hydrolysis with 435, the content of diglycerides in rice bran oil can reach 40.38%-43.55%, which meets the requirement of not less than 40% stipulated in the "Announcement on Approving Seven Items Including Tea Seed Oil as New Resource Foods (No. 18 of 2009)". However, after enzymatic hydrolysis with lipase TLIM, the content of diglycerides in rice bran oil is only about 33%.

[0034] In some embodiments of the present invention, the molar ratio of rice bran oil to monoglyceride in step S10 is 1:0.2 to 1, for example, it can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, etc.

[0035] In some embodiments of the present invention, the mass of the lipase in step S20 is 2 to 8% of the mass of the mixed substrate, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, etc.

[0036] Reaction temperature has a certain impact on enzyme stability and the rate of enzymatic hydrolysis. Appropriately increasing the temperature can accelerate the reaction and shorten the reaction time. However, since enzymes are proteins, their denaturation rate also increases with temperature. Once the temperature exceeds the enzyme's optimal reaction temperature, the conformation of the enzyme's active site undergoes irreversible changes, thereby reducing or even deactivating the enzyme's catalytic activity. Therefore, reaction temperature is a crucial factor affecting enzymatic reactions. Specifically, in some embodiments of the present invention, the heating temperature of the mixture in step S20 is 50-70°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, etc.; the stirring reaction temperature after adding lipase in step S20 is 40-80°C, for example, it can be 40°C, 42°C, 44°C, 45°C, 46°C, 48°C, 50°C, 52°C, 54°C, 55°C, 56°C, 58°C, 60°C, 62°C, 64°C, 65°C, 66°C, 68°C, 70°C, 72°C, 74°C, 75°C, 76°C, 78°C, 80°C, etc. Furthermore, in some specific embodiments of the present invention, it is preferred that the heating temperature of the mixed substrate in step S20 is 60°C, under which the enzyme activity of lipase Novozym 435 reaches a better state. More preferably, the reaction temperature for the enzymatic reaction after adding lipase and stirring in step S20 can also be set to 60°C to accelerate the reaction rate to a greater extent.

[0037] In some embodiments of the present invention, the stirring speed in step S20 is 180 to 200 rpm, for example, 180 rpm, 185 rpm, 190 rpm, 195 rpm, 200 rpm, etc. In some specific embodiments of the present invention, the stirring speed is preferably 200 rpm; the stirring time is 6 to 12 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.

[0038] In some embodiments of the present invention, the centrifugation temperature in step S30 is 18-25°C, for example, it can be 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, etc.; the centrifugation speed is 5000-6000 rpm, for example, it can be 5000 rpm, 5100 rpm, 5200 rpm, 5300 rpm, 5400 rpm, 5500 rpm, 5600 rpm, 5700 rpm, 5800 rpm, 5900 rpm, 6000 rpm, etc.; the centrifugation time is 15-20 min, for example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, etc.

[0039] Furthermore, through experimental comparison and research, in some specific embodiments of the present invention, the centrifugation parameters in step S30 are preferably set as follows: centrifugation temperature is 20°C, centrifugation speed is 6000 rpm, and centrifugation time is 15 min.

[0040] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0041] Example 1

[0042] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:1.

[0043] (2) Heat the mixed substrate to 60°C, then add 6% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 60°C and stir at 200 rpm for 8 h.

[0044] (3) After the reaction is complete, centrifuge at 6000 rpm for 15 min at 20℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0045] Example 2

[0046] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.5.

[0047] (2) Heat the mixed substrate to 60°C, then add lipase Novozym 435 at 8% of its mass to the mixed substrate, and then place it in a constant temperature water bath shaker set to 80°C and stir at 200 rpm for 10 h.

[0048] (3) After the reaction is complete, centrifuge at 6000 rpm for 15 min at 20℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0049] Example 3

[0050] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.2.

[0051] (2) Heat the mixed substrate to 70°C, then add 5% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 60°C and stir at a stirring rate of 200 rpm for 8 h.

[0052] (3) After the reaction is complete, centrifuge at 6000 rpm for 15 min at 20℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0053] Example 4

[0054] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.3.

[0055] (2) Heat the mixed substrate to 65°C, then add 7% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 70°C and stir at a stirring rate of 190 rpm for 9 h.

[0056] (3) After the reaction is complete, centrifuge at 5800 rpm for 16 min at 18℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0057] Example 5

[0058] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.4.

[0059] (2) Heat the mixed substrate to 55°C, then add 4% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 40°C and stir at 180 rpm for 12 h.

[0060] (3) After the reaction is complete, centrifuge at 5600 rpm for 17 min at 22℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0061] Example 6

[0062] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.6.

[0063] (2) Heat the mixed substrate to 50°C, then add 3% of its mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 50°C and stir at a stirring rate of 185 rpm for 12 h.

[0064] (3) After the reaction is complete, centrifuge at 5500 rpm for 18 min at 24℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0065] Example 7

[0066] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.7.

[0067] (2) Heat the mixed substrate to 62°C, then add 2% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 55°C and stir at a stirring rate of 195 rpm for 7 h.

[0068] (3) After the reaction is complete, centrifuge at 5400 rpm for 19 min at 25°C and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0069] Example 8

[0070] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.8.

[0071] (2) Heat the mixed substrate to 58°C, then add 6% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 65°C and stir at 200 rpm for 6 h.

[0072] (3) After the reaction is complete, centrifuge at 5200 rpm for 20 min at 21℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0073] Example 9

[0074] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:0.9.

[0075] (2) Heat the mixed substrate to 64°C, then add 6% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 70°C and stir at 200 rpm for 10 h.

[0076] (3) After the reaction is complete, centrifuge at 5000 rpm for 20 min at 23℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0077] Example 10

[0078] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:1.

[0079] (2) Heat the mixed substrate to 56°C, then add 6% by mass of lipase Novozym 435 to the mixed substrate, and then place it in a constant temperature water bath shaker set to 75°C and stir at 200 rpm for 8 h.

[0080] (3) After the reaction is complete, centrifuge at 6000 rpm for 20 min at 19℃ and collect the upper oil sample to obtain rice bran oil rich in diglycerides.

[0081] Comparative Example 1

[0082] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:1.

[0083] (2) Heat the mixed substrate to 60°C, then add 6% of the mass of lipase Lipozyme RMIM to the mixed substrate, and then place it in a constant temperature water bath shaker set to 60°C and stir at a stirring rate of 200 rpm for 8 h.

[0084] (3) After the reaction is complete, the mixture is centrifuged at 6000 rpm for 15 min at 20℃, and the upper oil sample is collected to obtain rice bran oil containing diglycerides.

[0085] Comparative Example 2

[0086] (1) Take fresh rice bran oil and monoglyceride and mix them evenly to obtain a mixed substrate, wherein the molar ratio of rice bran oil to monoglyceride is 1:1.

[0087] (2) Heat the mixed substrate to 60°C, then add 6% of the mass of lipase Lipozyme TLIM to the mixed substrate, and then place it in a constant temperature water bath shaker set to 60°C and stir at a stirring rate of 200 rpm for 8 h.

[0088] (3) After the reaction is complete, the mixture is centrifuged at 6000 rpm for 15 min at 20℃, and the upper oil sample is collected to obtain rice bran oil containing diglycerides.

[0089] The content of diglycerides in the products obtained in each example and comparative example was tested separately. The test methods and results are as follows:

[0090] Determination of diglyceride content: The composition of the reaction products was analyzed using a normal-phase HPLC system equipped with a differential detector (10A-SPD 20A) and a silica gel column (5 μm, 250 mm × 4.6 mm). The mobile phase consisted of n-hexane, isopropanol, and formic acid (volume ratio 15:1:0.003). The column oven temperature was 30 °C, and the flow rate was 1 mL / min. Qualitative analysis was performed by comparing the retention times of each component with standards, and quantitative analysis was performed using the area normalization method.

[0091] The test results are shown in Table 1 below. In Table 1, the superscript letters indicate the significance of the differences between each group of data (p < 0.05).

[0092] Table 1. Diglyceride content in the examples and comparative examples.

[0093]

[0094]

[0095] As shown in Table 1, compared with the lipases Lipozyme RMIM and Lipozyme TLIM used in the comparative examples, the lipase Novozym 435 used in the embodiments of the present invention has a higher diglyceride conversion rate, which can more significantly increase the diglyceride content in rice bran oil. Moreover, the diglyceride content in all embodiments is not less than 40%, which meets the relevant provisions in the "Announcement on Approving Seven Items Including Tea Seed Oil as New Resource Foods (No. 18 of 2009)".

[0096] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A method for preparing a glycerol diester-rich rice oil, characterized by, The preparation method of the glyceride-rich rice oil comprises the following steps: rice oil is mixed with monoglyceride to obtain a mixed substrate; the mixed substrate is heated to 50-70℃, then lipase is added, and stirring is performed at 40-80℃ to conduct lipase catalysis; after the lipase catalysis is completed, the upper oil sample is collected by centrifugation to obtain glyceride-rich rice oil.

2. The method of producing a diglyceride-enriched rice oil according to claim 1, wherein The lipase comprises lipase Novozym 435.

3. The method of producing a diglyceride-enriched rice oil according to claim 1, wherein In the step of mixing rice oil with monoglyceride to obtain a mixed substrate: The molar ratio of the rice oil to the monoglyceride is 1:0.2-1.

4. The method of producing a diglyceride-enriched rice oil according to claim 1, wherein In the step of heating the mixed substrate to 50-70℃, then adding lipase, and stirring at 40-80℃ to conduct lipase catalysis: The mass of the lipase is 2-8% of the mass of the mixed substrate.

5. The method of producing a diglyceride-enriched rice oil according to claim 1, wherein In the step of heating the mixed substrate to 50-70℃, then adding lipase, and stirring at 40-80℃ to conduct lipase catalysis: The heating temperature of the mixed substrate is 60℃.

6. The method of producing a diglyceride-enriched rice oil according to claim 1, wherein In the step of heating the mixed substrate to 50-70℃, then adding lipase, and stirring at 40-80℃ to conduct lipase catalysis: The stirring speed is 180-200rpm, and the stirring time is 6-12h.

7. The method of producing a diglyceride-enriched rice oil according to claim 1, wherein In the step of centrifuging and collecting the upper oil sample after the lipase catalysis is completed to obtain glyceride-rich rice oil: The centrifugation temperature is 18-25℃, the centrifugation speed is 5000-6000rpm, and the centrifugation time is 15-20min.

8. The method of producing a diglyceride-enriched rice oil according to claim 1, wherein In the step of centrifuging and collecting the upper oil sample after the lipase catalysis is completed to obtain glyceride-rich rice oil: The centrifugation temperature is 20℃, the centrifugation speed is 6000rpm, and the centrifugation time is 15min.

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