Coconut oil rich in diglyceride and preparation method thereof

Abstract

The invention discloses coconut oil rich in diglyceride and a preparation method thereof, and belongs to the technical field of coconut oil deep processing, and the preparation method comprises the following steps: heating coconut oil and monoglyceride as substrates, adding Novozym 435 lipase as a catalyst, and carrying out a catalytic reaction at 40-80 DEG C to obtain the coconut oil rich in diglyceride. The coconut oil and the monoglyceride are used as main raw materials, and the Novozym 435 lipase is selected as a catalyst, so that the conversion efficiency of the diglyceride is improved, the content of the diglyceride in the coconut oil is greatly increased, the nutritional characteristics of the coconut oil are combined with the functional characteristics of the diglyceride, and the nutritional value of the coconut oil is further improved. Meanwhile, the preparation method provided by the invention is mild in reaction condition, low in energy consumption and good in reaction specificity.

Description

Technical Field

[0001] The invention relates to the technical field of coconut oil deep processing, and in particular to coconut oil rich in diglyceride and a preparation method thereof. Background Art

[0002] Diacylglycerol (DAG) is formed by the esterification of one or two fatty acids with the hydroxyl groups of glycerol at different positions. It primarily exists as two isomers: 1,3-DAG and 1,2-DAG. It is a natural component of oils and fats, with taste, color, and flavor similar to triglycerides. However, it possesses unique physiological functions and can be used as an additive in a variety of applications, including food, medicine, and chemicals.

[0003] Currently, DAG is produced primarily through chemical and enzymatic methods. While the chemical method is relatively inexpensive, it requires high temperatures, strong acids and bases, and high pressure, resulting in the production of numerous harmful substances and poor controllability. Enzymatic methods, on the other hand, offer advantages such as mild reaction conditions, high specificity, and the absence of toxic byproducts. These methods are more aligned with the needs of green industrial development and are attracting widespread attention.

[0004] Coconut oil, a new edible oil, is primarily composed of medium-chain fatty acid glycerides, with lauric acid content ranging from 41% to 56%. Coconut oil, a plant oil primarily composed of medium-chain fatty acids (MCFA), has high application value in medicine, cosmetics, and regulating human metabolism and blood lipids. However, coconut oil's naturally low diacylglycerol content (typically <5%) limits its metabolic regulation. While high in triacylglycerols (TAGs), coconut oil provides a rapid energy source, excessive intake can lead to elevated blood lipid levels or visceral fat accumulation. A moderate intake of DAGs, however, produces fewer chylomicrons during metabolism than TAGs, and some fatty acids enter the liver directly through the portal vein for oxidation and energy production, reducing fat accumulation and increasing satiety. Therefore, while coconut oil is rich in medium-chain fatty acids and antioxidants, its naturally low DAG content limits its metabolic health benefits. Summary of the Invention

[0005] The present invention provides a diglyceride-rich coconut oil and a preparation method thereof, which effectively solves the technical problem of naturally low diglyceride content in current coconut oil. The present invention uses monoglyceride and coconut oil as substrates and lipase as a catalyst to react to obtain diglyceride-rich coconut oil, thereby increasing the diglyceride content in the coconut oil and fully combining the nutritional properties of coconut oil with the functional properties of diglyceride.

[0006] A first object of the present invention is to provide a method for preparing diglyceride-rich coconut oil, comprising the following steps: Coconut oil and monoglyceride are used as substrates, heated, and Novozym 435 lipase is used as a catalyst to carry out a catalytic transesterification reaction at 40℃~80℃, thereby transferring the fatty acids of triglycerides in the coconut oil to monoglycerides to form diglycerides, thereby obtaining coconut oil rich in diglycerides.

[0007] As a preferred embodiment, the molar ratio of the monoglyceride to the coconut oil is 1:1-3.

[0008] As a preferred embodiment, the amount of Novozym 435 lipase added is 1% to 6% based on the mass of the substrate.

[0009] As a preferred embodiment, the catalytic transesterification reaction is: stirring at 40°C to 80°C and 180 r / min to 220 r / min for 6h to 10h.

[0010] As a preferred embodiment, the temperature of the catalytic reaction is 60°C.

[0011] As a preferred embodiment, the heating temperature is 50°C to 70°C.

[0012] As a preferred embodiment, after the catalytic reaction is completed, a primary product is obtained, and the primary product is centrifuged at 18°C ​​to 25°C and 4000r / min to 6000r / min for 10min to 20min, and an upper oil sample is taken to obtain coconut oil rich in diglyceride.

[0013] The second object of the present invention is to provide a diglyceride-rich coconut oil prepared by any of the above-mentioned preparation methods.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing diglyceride-rich coconut oil. Coconut oil and monoglycerides are heated and catalyzed by Novozym 435 lipase at 40°C to 80°C. Novozym 435 lipase specifically binds to triglycerides in the coconut oil, forming an acyl-enzyme intermediate that promotes the transfer of fatty acids from the triglycerides to the monoglycerides, thereby producing diglyceride-rich coconut oil. This method uses coconut oil and monoglycerides as the primary raw materials and Novozym 435 lipase as a catalyst, improving the conversion efficiency to diglycerides and significantly increasing the diglyceride and lauric acid content in the coconut oil. This method combines the nutritional properties of coconut oil with the functional properties of diglycerides, further enhancing the nutritional value of coconut oil. By enzymatically modifying coconut oil to increase its DAG content, the present invention can upgrade it from a traditional edible oil to a new generation of functional oils that combine rapid energy supply, weight management, and cardiovascular protection, meeting the needs of the health consumer market. The preparation method provided by the invention has mild reaction conditions, low energy consumption and good reaction specificity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a comparison chart showing the effects of different types of lipase on diacylglycerol content in the present invention.

[0016] Figure 2 This is a comparison chart showing the effects of different molar ratios of monoglyceride and coconut oil (crude oil) on the content of structural esters in the diglyceride system of the present invention.

[0017] Figure 3 This is a comparison chart of the effects of different catalytic reaction times on the content of structural esters in the diglyceride system of the present invention.

[0018] Figure 4 This is a comparison chart of the effects of different catalytic reaction temperatures on the content of structural esters in the diglyceride system of the present invention.

[0019] Figure 5 This is a comparison chart of the effects of different enzyme addition amounts on the content of structural esters in the diglyceride system of the present invention.

[0020] Figure 6 The fatty acid release rates of the diglyceride oil and raw coconut oil prepared under the optimal conditions of the present invention in the in vitro digestion simulation. DETAILED DESCRIPTION

[0021] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples, but the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0022] Because coconut oil contains an extremely low natural diglyceride content (typically less than 5%), its metabolic regulation function has certain limitations. Coconut oil, while high in triglycerides (TAG), can quickly provide energy to the human body, but excessive intake can lead to elevated blood lipid levels or accumulation of visceral fat. Ingesting a certain amount of diglyceride (DAG) can produce fewer chylomicrons during metabolism in the body than during TAG metabolism, and some fatty acids enter the liver directly through the portal vein for oxidation and energy supply, reducing fat accumulation while increasing satiety. Therefore, although coconut oil is rich in medium-chain fatty acids and antioxidants, its naturally low DAG content limits its metabolic health functions. To address the technical drawbacks of natural coconut oil with a low DAG content, the present invention provides a coconut oil rich in diglycerides and a method for preparing it.

[0023] The technical solution of the present invention is described in detail below.

[0024] The present invention first provides a method for preparing coconut oil rich in diglyceride, comprising the following steps: Coconut oil and monoglyceride are used as substrates, heated, and Novozym 435 lipase is used as a catalyst to carry out a catalytic transesterification reaction at 40℃~80℃, thereby transferring the fatty acids of triglycerides in the coconut oil to monoglycerides to form diglycerides, thereby obtaining coconut oil rich in diglycerides.

[0025] In the above technical solution, during the catalytic transesterification reaction, Novozym 435 lipase specifically binds to triglycerides in coconut oil to form an acyl-enzyme intermediate, which promotes the transfer of fatty acids from triglycerides to monoglycerides, thereby converting them into diglycerides, thereby obtaining coconut oil rich in diglycerides, greatly increasing the diglyceride content in natural coconut oil.

[0026] In order to further increase the diglyceride content in coconut oil and prevent excessive impurities from affecting the purity of coconut oil, the molar ratio of monoglyceride to coconut oil is 1:1 to 3. When this molar ratio is less than the 1:3 specified herein, since the transesterification reaction is a reversible reaction, the excessive coconut oil content will result in an excessively high triglyceride content in the system, thereby inhibiting the forward reaction and ultimately resulting in a low diglyceride yield. It also increases the reaction time and separation difficulty while generating more impurities, such as free fatty acids and unseparated triglycerides. When this molar ratio is greater than 1:1 as defined herein, the monoglyceride content is too high. Since monoglyceride contains free hydroxyl groups and is highly polar, an excessive amount can increase the viscosity of the product system, affecting its fluidity (e.g., making it difficult to disperse evenly during food processing) and even forming a colloidal structure, which reduces application performance and leads to poor oxidative stability. Furthermore, due to the excessively high monoglyceride content, the stability of the final product (e.g., a food additive or cosmetic raw material) is reduced, making it prone to rancidity or deterioration. Therefore, the present invention limits the molar ratio of monoglyceride to coconut oil to 1:1 to 3.

[0027] In order to further increase the diglyceride content in coconut oil, the amount of Novozym 435 lipase added is 1% to 6% based on the mass of the substrate. When the amount of Novozym 435 lipase added is less than the 1% specified herein, that is, the amount of Novozym 435 lipase used is small, the catalytic efficiency will be insufficient, the amount of diglyceride generated will decrease significantly as the amount of enzyme decreases, and the products will be mainly unreacted triglycerides and monoglycerides. When the amount of Novozym 435 lipase added is greater than the 6% specified herein, the diglyceride content will first increase due to reaction acceleration, and after exceeding the critical value, it will tend to stabilize or slightly decrease due to equilibrium limitations and side reactions, and the cost will increase.

[0028] To enhance the catalytic activity of Novozym 435 lipase, the catalytic transesterification reaction is performed at 40°C to 80°C and stirring at 180 rpm to 220 rpm for 6 to 10 hours. Temperatures below 40°C significantly reduce diacylglycerol yield and prolong reaction time due to low enzyme activity and poor mass transfer. The need to maintain low temperatures also increases production costs. Temperatures above 80°C rapidly deactivate the enzyme and increase side reactions, resulting in decreased diacylglycerol yield, increased impurities, and safety and cost risks.

[0029] In order to further improve the catalytic activity of Novozym 435 lipase and promote the conversion rate of diglyceride to reach an optimal value, the temperature of the catalytic reaction is 60°C.

[0030] To further improve the conversion rate of diglyceride, the heating temperature is 50°C to 70°C. When the temperature is lower than 50°C, the reaction rate is slow and the DAG yield is low; when the temperature is higher than 70°C, the enzyme is inactivated and more by-products are produced. In addition to DAG, the product contains more impurities and hazardous substances.

[0031] In order to obtain coconut oil with higher purity, after the catalytic reaction is completed, a primary product is obtained, and the primary product is centrifuged at 18° C. to 25° C. and 4000 r / min to 6000 r / min for 10 min to 20 min, and an upper oil sample is taken to obtain coconut oil rich in diglyceride.

[0032] The present invention will be described in detail below through the following examples and comparative examples.

[0033] Example 1 A method for preparing diglyceride-rich coconut oil comprises the following steps: Fresh monoglyceride and coconut oil were mixed uniformly in a molar ratio of 1:1.5 to obtain a mixed substrate. The mixed substrate was heated to 60°C, and then lipase Novozym 435 accounting for 3% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 60°C and stirred at a stirring rate of 200 r / min for catalytic reaction for 8 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil rich in diglyceride.

[0034] Example 2 A method for preparing diglyceride-rich coconut oil comprises the following steps: Fresh monoglyceride and coconut oil were mixed uniformly in a molar ratio of 1:2 to obtain a mixed substrate. The mixed substrate was heated to 60°C, and then lipase Novozym 435 accounting for 4% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 70°C and stirred at a stirring rate of 200 r / min for catalytic reaction for 10 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil rich in diglyceride.

[0035] Example 3 A method for preparing diglyceride-rich coconut oil comprises the following steps: Fresh coconut oil and monoglyceride were mixed uniformly in a molar ratio of 1:1 to obtain a mixed substrate. The mixed substrate was heated to 70°C, and then 2% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 50°C and stirred at a stirring rate of 200 r / min for a catalytic reaction for 6 hours. After the reaction was completed, the mixture was centrifuged at a rate of 5000 r / min for 15 minutes at a temperature of 20°C, and the upper oil sample was collected to obtain coconut oil rich in diglyceride.

[0036] Example 4 A method for preparing diglyceride-rich coconut oil comprises the following steps: Fresh monoglyceride and coconut oil were mixed uniformly in a molar ratio of 1:2.5 to obtain a mixed substrate. The mixed substrate was heated to 65°C, and then lipase Novozym 435 accounting for 3.6% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 60°C and stirred at a stirring rate of 200 r / min for a catalytic reaction for 9 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil rich in diglyceride.

[0037] In order to further illustrate the effect of the present invention, the present invention also provides a comparative example, which is as follows: Comparative Example 1 Compared with Example 1, the difference is that the lipase Novozym 435 is replaced by the lipase Lipozyme RMIM.

[0038] A method for preparing diglyceride-rich coconut oil comprises the following steps: Fresh monoglyceride and coconut oil were mixed uniformly in a molar ratio of 1:1.5 to obtain a mixed substrate. The mixed substrate was heated to 60°C, and then lipase Lipozyme RM IM accounting for 3% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 60°C and stirred at a stirring rate of 200 r / min for catalytic reaction for 8 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil rich in diglyceride.

[0039] Comparative Example 2 Compared with Example 1, the difference is that the lipase Novozym 435 is replaced by the lipase Lipozyme TLIM.

[0040] A method for preparing diglyceride-rich coconut oil comprises the following steps: Fresh monoglyceride and coconut oil were mixed uniformly in a molar ratio of 1:1.5 to obtain a mixed substrate. The mixed substrate was heated to 60°C, and then lipase Lipozyme TL IM accounting for 3% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 60°C and stirred at a stirring rate of 200 r / min for catalytic reaction for 8 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil rich in diglyceride.

[0041] Comparative Example 3 Compared with Example 4, the difference is that the monoglyceride is replaced by an equal molar amount of glycerol.

[0042] A method for preparing coconut oil containing diglyceride comprises the following steps: Fresh glycerol and coconut oil were mixed uniformly in a molar ratio of 1:2.5 to obtain a mixed substrate. The mixed substrate was heated to 65°C, and then lipase Novozym 435 accounting for 3.6% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 60°C and stirred at a stirring rate of 200 r / min for a catalytic reaction for 9 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil containing diglyceride.

[0043] Comparative Example 4 Compared with Example 1, the difference is that the monoglyceride is replaced by an equal molar amount of glycerol.

[0044] A method for preparing coconut oil containing diglyceride comprises the following steps: Fresh glycerol and coconut oil were mixed uniformly in a molar ratio of 1:1.5 to obtain a mixed substrate. The mixed substrate was heated to 60°C, and then lipase Novozym 435 accounting for 3% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 60°C and stirred at a stirring rate of 200 r / min for catalytic reaction for 8 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil containing diglyceride.

[0045] Comparative Example 5 Compared with Example 2, the difference is that the monoglyceride is replaced by an equal molar amount of glycerol.

[0046] A method for preparing coconut oil containing diglyceride comprises the following steps: Fresh glycerol and coconut oil were mixed uniformly in a molar ratio of 1:2 to obtain a mixed substrate. The mixed substrate was heated to 60°C, and then lipase Novozym 435 accounting for 4% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 70°C and stirred at a stirring rate of 200 r / min for catalytic reaction for 10 hours. After the reaction was completed, the mixture was centrifuged at a temperature of 20°C and a speed of 5000 r / min for 15 minutes, and the upper oil sample was collected to obtain coconut oil containing diglyceride.

[0047] Comparative Example 6 Compared with Example 3, the difference is that the monoglyceride is replaced by an equal molar amount of glycerol.

[0048] A method for preparing coconut oil containing diglyceride comprises the following steps: Fresh glycerol and coconut oil were mixed uniformly in a molar ratio of 1:1 to obtain a mixed substrate. The mixed substrate was heated to 70°C, and then 2% of the mass of the mixed substrate was added to the mixed substrate. The mixture was then placed in a constant temperature water bath oscillator set at 50°C and stirred at a stirring rate of 200 r / min for a catalytic reaction for 6 hours. After the reaction was completed, the mixture was centrifuged at a rate of 5000 r / min at a temperature of 20°C for 15 minutes, and the upper oil sample was collected to obtain coconut oil containing diglyceride.

[0049] The results of the test on the diglyceride content in the products of Examples 1 to 4 and Comparative Examples 1 to 6 are shown in Table 1.

[0050] Table 1 Diaceryl content in Examples of the present invention and Comparative Examples Note: The superscript letters a~j are significant differences obtained through analysis by data processing software SPSS, indicating that the inter-group differences between these data have reached a significant level, and P <0.05.

[0051] The results in Table 1 show that compared to the lipases Lipozyme RM IM and Lipozyme TL IM used in Comparative Example 1 and Comparative Example 2, respectively, the lipase Novozym 435 employed in the present invention achieved a higher diglyceride conversion rate, significantly increasing the diglyceride content in coconut oil. The optimal process conditions obtained in Example 4 were a substrate ratio of 1:2.5, a reaction time of 9 hours, a temperature of 65°C, and an enzyme dosage of 3.6%. The coconut oil obtained by this method had a diglyceride content of 52.92%. Furthermore, in an in vitro digestion simulation experiment, the coconut diglyceride oil obtained after enzymatic hydrolysis exhibited a higher fatty acid release rate during intestinal digestion than the raw coconut oil, making it suitable for the industrial production of functional oils.

[0052] Figure 1 This is a comparison chart of the effects of different types of lipase on diacylglycerol content. Figure 1 It can be seen that compared with Comparative Example 1 using lipase Lipozyme RM IM and Comparative Example 2 using lipase Lipozyme TL IM, the content of diglyceride in the coconut oil prepared by using lipase Novozym 435 in the present invention is higher.

[0053] Figure 2 The figure is a comparison chart of the effects of different molar ratios of monoglyceride and glycerol substrates on the content of structural esters in the diglyceride system of the present invention. Figure 2 It can be seen that compared with other molar ratios, the content of diglyceride obtained when the molar ratio of monoglyceride to coconut oil used in the present invention is 1:1~3 is at a higher level.

[0054] Figure 3 This is a comparison chart of the effects of different catalytic reaction times on the content of structural esters in the diglyceride system of the present invention. Figure 3 It can be seen that, compared with other catalytic reaction times, the content of diglyceride obtained under the catalytic reaction time of 8h~10h adopted in the present invention is at a higher level.

[0055] Figure 4 The figure is a comparison chart of the effects of different catalytic reaction temperatures on the content of structural esters in the diglyceride system of the present invention. Figure 4 It can be seen that compared with other reaction temperatures, the content of diglyceride obtained at the reaction temperature of 50°C to 70°C adopted in the present invention is at a higher level.

[0056] Figure 5 The figure is a comparison chart of the effects of different enzyme addition amounts on the content of structural esters in the diglyceride system of the present invention. Figure 5 It can be seen that, compared with other enzyme addition amounts, the diacylglycerol content obtained when the addition amount of Novozym 435 lipase used in the present invention is 1% to 6% is at a higher level.

[0057] Figure 6 The fatty acid release rate of coconut oil diglyceride oil and raw coconut oil prepared under the optimal conditions of the present invention in the in vitro digestion simulation. Figure 6 It can be seen that the fatty acid release rate of diglyceride oil is the highest at 48.19%, which is higher than the highest 36.99% in original coconut oil, reflecting good digestibility.

[0058] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing diglyceride-rich coconut oil, characterized in that: The following steps are involved: Coconut oil and monoglyceride are used as substrates, heated, and Novozym 435 lipase is used as a catalyst to carry out a catalytic transesterification reaction at 40℃~80℃, thereby transferring the fatty acids of triglycerides in the coconut oil to monoglycerides to form diglycerides, thereby obtaining coconut oil rich in diglycerides.

2. The preparation method according to claim 1, characterized in that The molar ratio of the monoglyceride to the coconut oil is 1:1-3.

3. The preparation method according to claim 1, characterized in that The amount of Novozym435 lipase added is 1% to 6% based on the mass of the substrate.

4. The preparation method according to claim 1, characterized in that The catalytic transesterification reaction is as follows: stirring at 40° C. to 80° C. and a rotation speed of 180 r / min to 220 r / min for 6 h to 12 h.

5. The preparation method according to claim 4, characterized in that The temperature of the catalytic reaction is 60°C.

6. The preparation method according to claim 1, characterized in that The heating temperature is 50°C to 70°C.

7. The preparation method according to claim 1, characterized in that After the catalytic reaction is completed, a primary product is obtained, and the primary product is centrifuged at 18° C. to 25° C. and 4000 r / min to 6000 r / min for 10 min to 20 min, and an upper oil sample is taken to obtain coconut oil rich in diglyceride.

8. A diglyceride-rich coconut oil, characterized in that The preparation method according to any one of claims 1 to 7 is used to prepare the compound.

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