A method for preparing high-oil-loading polyunsaturated fatty acid oil microcapsules

Abstract

This invention relates to the field of microencapsulation technology, specifically providing a method for preparing high-oil-loading polyunsaturated fatty acid microcapsules. In the preparation method provided by this invention, inulin, a protein emulsifier, and water are heated to 50-68°C and stirred thoroughly for 15-40 minutes; the weight ratio of inulin to protein emulsifier is (0.4-1):1. The preparation method provided by this invention, without changing the spray drying process, ensures that the high-oil-loading microcapsule product is not over-dried, improving the product's sensory properties while guaranteeing its stability during shelf life.

Description

Technical Field

[0001] This invention relates to the field of microcapsule technology, and in particular to a method for preparing high-oil-loading polyunsaturated fatty acid oil microcapsules. Background Technology

[0002] Arachidonic acid oils and docosahexaenoic acid oils are easily oxidized due to their structure, producing unpleasant odors and affecting their function. Microencapsulation technology is often used to protect polyunsaturated fatty acid oils such as arachidonic acid oils and docosahexaenoic acid oils with encapsulating materials, thereby improving their stability and flavor.

[0003] Existing technologies have already developed methods for preparing microcapsules with high content of polyunsaturated fatty acids. For example, CN103549442A prepares DHA algal oil powder with an oil loading rate of 33-50% by optimizing the wall material components; CN102228257A improves the stability of high-content microcapsules by improving antioxidants; CN110613025A uses compound emulsifiers to reduce the surface oil of high-content microcapsules; CN110613025A microcapsule powder encapsulates 45-80% of oils such as MCT and olive oil. The applicant unexpectedly discovered that the formulation of high-oil-loading polyunsaturated fatty acid oil microcapsules, especially protein system emulsifiers, can cause discoloration and other phenomena within the shelf life. Summary of the Invention

[0004] To address the stability issue of high oil loading capacity polyunsaturated fatty acid oil microcapsules within their shelf life, this invention provides a method for preparing high oil loading capacity polyunsaturated fatty acid oil microcapsules.

[0005] In a first aspect, the method for preparing polyunsaturated fatty acid oil microcapsules provided by the present invention includes preparing a water-soluble wall material to encapsulate polyunsaturated fatty acid oil; the preparation of the water-soluble wall material includes: heating inulin, protein emulsifier and water to 50-68°C and stirring thoroughly for 15-40 min; the weight ratio of inulin to protein emulsifier is (0.4-1):1;

[0006] The mass percentage of polyunsaturated fatty acid oil in the microcapsule raw material is not less than 40%, and the content of fatty acids with a carbon chain length of more than 20 and more than 4 unsaturated double bonds in the polyunsaturated fatty acid oil is not less than 40%.

[0007] The microcapsule raw materials refer to the total amount of raw materials other than water.

[0008] In the preparation method provided by this invention, inulin accounts for 6.5-15% of the weight of the microcapsule raw materials.

[0009] In the present invention, the polyunsaturated fatty acid oil includes, but is not limited to, one or more of DHA, DPA, EPA, and ARA. For example, the DHA oil mentioned in the present invention contains DPA, EPA, and ARA in addition to DHA, but the main component is DHA.

[0010] The applicant discovered that when using protein emulsifiers as wall materials to prepare high-oil-loading polyunsaturated fatty acid microcapsules, the finished microcapsules exhibited poor stability and color changes, hindering their subsequent utilization. Research revealed that the stability issue stemmed from the fact that during the product's water preparation process, the hydrophobic oils constituted 50% or more of the system. The aqueous phase in the emulsion system tended to migrate to the surface, leading to rapid water loss during drying. This resulted in over-drying of the product, affecting not only its sensory properties but also its stability.

[0011] This invention is the first to discover that the addition of inulin, coupled with optimization of the preparation process, can effectively improve the stability of microcapsule products during their shelf life. More specifically, this invention raises the temperature to 50-68℃, causing some of the hydroxyl groups of inulin to bind with proteins, ensuring that the high-oil-loading polyunsaturated fatty acid microcapsule products are not excessively dried, while avoiding the drawbacks of inulin's hygroscopic nature.

[0012] In existing technologies, inulin is often used in microcapsules as a small-molecule prebiotic or dietary fiber, along with fillers, to enhance efficacy while providing a certain filling effect. Inulin is three times more hygroscopic than itself; adding inulin can cause it to stick to the walls during the drying process and subsequently absorb moisture. Therefore, when inulin is added as a filler, the amount used is very small.

[0013] In the preparation method provided by this invention, if the reaction conditions between inulin and protein emulsifier are too harsh, such as higher temperature or longer reaction time, the Maillard reaction will occur, causing changes in the system. In order to keep the properties of the raw materials unchanged, this invention needs to prevent the Maillard reaction from occurring.

[0014] Specifically, the method for preparing polyunsaturated fatty acid oil microcapsules provided by the present invention includes:

[0015] (1) Heat inulin, protein emulsifier and water to 60-68℃ and stir for 15-40 minutes until fully stirred;

[0016] (2) Add filler and antioxidant and stir thoroughly to dissolve to obtain an aqueous phase;

[0017] (3) Add the polyunsaturated fatty acid oil to the aqueous phase obtained in step (2) and shear it to obtain an emulsion;

[0018] (4) The emulsion obtained in step (3) is homogenized under high pressure and then dried;

[0019] (5) Add an anti-caking agent and dry mix.

[0020] Preferably, step (2) further includes a pH adjuster and / or a chelating agent.

[0021] In the preparation method of polyunsaturated fatty acid oil microcapsules provided by the present invention, the drying in step (4) is spray drying, with an inlet air temperature of 160-180℃ and an outlet air temperature of 60-80℃.

[0022] In the preparation method of polyunsaturated fatty acid oil microcapsules provided by the present invention, the protein emulsifier is one or more of sodium caseinate, whey protein, soy protein, and pea protein; preferably, the protein emulsifier is sodium caseinate and / or whey protein.

[0023] The antioxidants include, but are not limited to, one or more of the following: sodium ascorbate, ascorbic acid, ascorbyl palmitate, vitamin E, and phospholipids; the preferred components listed in this invention are those more suitable for infant formula, but in actual application, they can be selected according to component requirements.

[0024] The anti-caking agents include, but are not limited to, one or more of tricalcium phosphate, silicon dioxide, microcrystalline cellulose, and magnesium stearate; the preferred components listed in this invention are those more suitable for infant formula, but in actual application, they can be selected according to component requirements.

[0025] The fillers include, but are not limited to, one or two of solid corn syrup and maltodextrin. The preferred components listed in this invention are those more suitable for infant formula, but in practical applications, selection can be made according to component requirements.

[0026] In step (2), the pH adjuster and / or chelating agent are selectively added depending on the raw materials. In one specific embodiment of the invention, the pH can be kept at its natural state, and the chelating agent may be omitted.

[0027] During the preparation process, the process parameters, as well as the conditions such as shear rate, homogenization pressure, and solid content, are all handled in accordance with treatment schemes well known to those skilled in the art, so that the liquid can be completely emulsified and smoothly sprayed out.

[0028] As a specific embodiment of the present invention, the method for preparing polyunsaturated fatty acid oil microcapsules provided by the present invention includes:

[0029] (1) Inulin, sodium caseinate, whey protein and water are stirred at 60-68℃ for 15-40 minutes. Then, solid corn syrup as filler and sodium VC as antioxidant are added and stirred thoroughly to dissolve, thus obtaining an aqueous phase.

[0030] (2) Add the polyunsaturated fatty acid oil to the above aqueous phase and shear it for 5-10 minutes at 10000-20000 r / min. The solid content is 45%.

[0031] (3) The above emulsions are homogenized 2-3 times using a high-pressure homogenizer at 800-1000 bar;

[0032] (4) Spray drying conditions are: air inlet temperature 160-180℃, air outlet temperature 60-80℃, and a certain air inlet volume and feeding speed are maintained.

[0033] (5) Add tricalcium phosphate and dry mix to obtain high oil-carrying polyunsaturated fatty acid oil microcapsules.

[0034] The present invention also provides the application of the above-described preparation method in improving the stability of high-oil-loaded polyunsaturated fatty acid oil microcapsules.

[0035] Secondly, the present invention provides polyunsaturated fatty acid oil microcapsules prepared by the above preparation method.

[0036] By weight, the proportion of protein emulsifier in the microcapsule raw material provided by this invention is 10-25%; and the proportion of inulin is 6.5-15%.

[0037] The polyunsaturated fatty acid oil microcapsules provided by this invention have a moisture content of 2-4%.

[0038] Thirdly, the present invention provides a high-oil-loading polyunsaturated fatty acid oil microcapsule, wherein the water content in the microcapsule is 2-4% by weight; apart from water, the raw material of the microcapsule comprises, by weight, 40-55% polyunsaturated fatty acid oil, 6-15% sodium caseinate, 4-10% whey protein, 6.5-15% inulin, 3-6% antioxidant, 0.2-1% anti-caking agent, and the remainder being filler, pH adjuster and / or chelating agent.

[0039] The beneficial effects of this invention are as follows:

[0040] This invention, through the addition of inulin and adjustment of the aqueous phase preparation method, ensures that the high oil-load microcapsule product is not over-dried while maintaining the spray drying process, thereby improving the product's sensory properties and ensuring its stability during its shelf life. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. In a specific embodiment, the polyunsaturated fatty acid oil is a DHA oil derived from algae, wherein the DHA content is 45%, and the total content of fatty acids with four or more unsaturated double bonds, including DHA / EPA / DPA / ARA, is 60%.

[0042] Example 1

[0043] In this embodiment, apart from water, the raw material for high-oil-loaded DHA oil microcapsules contains: DHA oil: 50%, sodium caseinate: 10%, whey protein: 10%, sodium vitamin C: 5%, solid corn syrup: 14.4%, inulin: 10%, and tricalcium phosphate: 0.6%.

[0044] The preparation method of the high oil-loading DHA lipid microcapsules in this embodiment is as follows:

[0045] (1) Weigh water-soluble wall materials inulin, sodium caseinate, whey protein and water in a mass ratio of 1:1:1:7, heat to 60℃ and stir thoroughly for 15 minutes, add filler solid corn syrup and antioxidant sodium VC, stir thoroughly to dissolve and obtain the aqueous phase;

[0046] (2) Add DHA oil to the above aqueous phase with a solid content of 45%, and shear at 10000 r / min for 10 min;

[0047] (3) The above emulsions were homogenized twice by a high-pressure homogenizer at 800 bar;

[0048] (4) The spray drying conditions are: air inlet temperature 180℃, air outlet temperature 80℃, and a certain air inlet volume and feeding speed.

[0049] (5) Add tricalcium phosphate and dry mix to obtain high oil-carrying DHA oil microcapsules.

[0050] Example 2

[0051] In this embodiment, apart from water, the raw material for the high-oil-loaded DHA oil microcapsules contains: DHA oil: 50%, sodium caseinate: 7.5%, whey protein: 7.5%, sodium vitamin C: 5%, solid corn syrup: 14.4%, inulin: 15%, and tricalcium phosphate: 0.6%.

[0052] The preparation method of the high oil-loading DHA lipid microcapsules in this embodiment is as follows:

[0053] (1) Weigh water-soluble wall materials inulin, sodium caseinate, whey protein and water in a mass ratio of 2:1:1:6, heat to 60℃ and stir thoroughly for 20 minutes, add filler solid corn syrup and antioxidant sodium VC, stir thoroughly to dissolve and obtain the aqueous phase;

[0054] (2) Add DHA oil to the above aqueous phase and shear for 10 min at 10000 r / min. The solid content is 45%.

[0055] (3) The above emulsions were homogenized twice by a high-pressure homogenizer at 800 bar;

[0056] (4) The spray drying conditions are: air inlet temperature 180℃, air outlet temperature 80℃, and a certain air inlet volume and feeding speed.

[0057] (5) Add tricalcium phosphate and dry mix to obtain high oil-carrying DHA oil microcapsules.

[0058] Example 3

[0059] In this embodiment, apart from water, the raw material for high-oil-loaded DHA oil microcapsules contains: DHA oil: 50%, sodium caseinate: 10.7%, whey protein: 10.7%, sodium vitamin C: 5%, solid corn syrup: 14.4%, inulin: 8.6%, and tricalcium phosphate: 0.6%.

[0060] The preparation method of the high oil-loading DHA lipid microcapsules in this embodiment is as follows:

[0061] (1) Weigh water-soluble wall materials inulin, sodium caseinate, whey protein and water in a mass ratio of 0.8:1:1:7, heat to 60℃ and stir thoroughly for 15 minutes, add filler solid corn syrup and antioxidant sodium VC, stir thoroughly to dissolve and obtain the aqueous phase;

[0062] (2) Add DHA oil to the above aqueous phase and shear for 10 min at 10000 r / min. The solid content is 45%.

[0063] (3) The above emulsions are homogenized 2-3 times using a high-pressure homogenizer at 800 bar;

[0064] (4) Spray drying conditions are: air inlet temperature 160-180℃, air outlet temperature 60-80℃, and a certain air inlet volume and feeding speed are maintained.

[0065] (5) Add tricalcium phosphate and dry mix to obtain high oil-carrying DHA oil microcapsules.

[0066] Example 4

[0067] In this embodiment, apart from water, the raw material for high-oil-loaded DHA oil microcapsules contains: DHA oil: 50%, sodium caseinate: 9.1%, whey protein: 9.1%, sodium vitamin C: 5%, solid corn syrup: 14.4%, inulin: 11.8%, and tricalcium phosphate: 0.6%.

[0068] The preparation method of the high oil-loading DHA lipid microcapsules in this embodiment is as follows:

[0069] (1) Weigh water-soluble wall materials inulin, sodium caseinate, whey protein and water in a mass ratio of 1.3:1:1:7, heat to 50℃ and stir thoroughly for 30 minutes, add filler solid corn syrup and antioxidant sodium VC, stir thoroughly to dissolve and obtain the aqueous phase;

[0070] (2) Add DHA oil to the above aqueous phase and shear at 10000r / min for 5-10min, with a solid content of 45%;

[0071] (3) The above emulsions are homogenized 2-3 times using a high-pressure homogenizer at 800 bar;

[0072] (4) Spray drying conditions are: air inlet temperature 160-180℃, air outlet temperature 60-80℃, and a certain air inlet volume and feeding speed are maintained.

[0073] (5) Add tricalcium phosphate and dry mix to obtain high oil-carrying DHA oil microcapsules.

[0074] Comparative Example 1 without inulin

[0075] In this comparative example, apart from water, the raw material for the high-oil-loaded DHA lipid microcapsules contains: DHA lipids: 50%, sodium caseinate: 15%, whey protein: 15%, sodium vitamin C: 5%, solid corn syrup: 14.4%, and tricalcium phosphate: 0.6%. In this comparative example, the mass ratio of sodium caseinate to whey protein to water in the aqueous phase preparation is 1:1:8.

[0076] The preparation method of this comparative example is the same as that of Example 1.

[0077] Comparative Example 2 (excluding heating and stirring)

[0078] This comparative example is the same as Example 1, except that in this comparative example, when preparing the aqueous phase, inulin, sodium caseinate, whey protein and water are weighed at room temperature in a mass ratio of 1:1:1:7, and solid corn syrup as filler and sodium VC as antioxidant are added and stirred.

[0079] Comparative Example 3: Different Amounts of Inulin Added

[0080] In this comparative example, apart from water, the raw material for the high-oil-loaded DHA oil microcapsules contains 50% DHA oil, 10% sodium caseinate, 10% whey protein, 5% sodium vitamin C, 14.4% solid corn syrup, 5% inulin, and 0.6% tricalcium phosphate. The preparation method is the same as in Example 1.

[0081] Comparative Example 4: Stir at 40℃ for 15 min

[0082] This comparative example is the same as Example 2, except that in this comparative example, when preparing the aqueous phase, inulin, sodium caseinate, whey protein and water were weighed at 40°C according to the corresponding amounts, and the filler solid corn syrup and antioxidant sodium VC were added and stirred.

[0083] Comparative Example 5

[0084] The comparative example is prepared using the same method as Example 2, except that the raw material for the high-oil-loaded DHA oil microcapsules contains: DHA oil: 50%, sodium caseinate: 10%, whey protein: 10%, sodium vitamin C: 5%, inulin: 20%, tricalcium phosphate: 0.6%, and the remainder is solid corn syrup.

[0085] Experimental Example

[0086] This experiment tested the surface tension of the high oil-loaded DHA oil microcapsule emulsion, the moisture content of the microcapsule powder, and the stability after 3 months of storage in the examples and comparative examples. The results are shown in Table 1.

[0087] The surface tension of the emulsion was measured using an automatic tension meter; the moisture content of the microcapsule powder was measured using a Karl Fischer moisture meter.

[0088] Table 1. Stability test results of microcapsule products

[0089]

[0090]

[0091] As shown in Comparative Example 1, in the absence of inulin, using only protein emulsifiers, the stability of high-oil-carrying DHA lipid microcapsules is poor, and the product color changes from white to pink within the shelf life.

[0092] As shown in Comparative Example 2, if inulin is added and the aqueous preparation method is not improved, the stability of the resulting microcapsule product still does not meet the requirements, and it still changes from white to pink within 3 months.

[0093] As shown in Comparative Example 3, if the amount of inulin added is too small, it cannot improve the stability of the microcapsule product. Furthermore, if the stirring temperature is too low or too high after adding inulin, it will not improve the stability of the product. Specifically, if the temperature is too high, the inulin and the protein emulsifier will undergo a Maillard reaction, resulting in a change in the product color. If the temperature is too low, as shown in Comparative Example 4, the appearance and color of the obtained microcapsule product are unstable within the 3-month shelf life, and color changes will occur.

[0094] Meanwhile, if too much inulin is added, and the ratio of inulin to sodium caseinate exceeds 1:1, the inulin cannot react completely with the sodium caseinate. The unreacted inulin is prone to absorbing moisture in subsequent stability tests, causing the powder to turn yellow. If, after adding inulin, the stirring time at 50-68℃ exceeds 40 minutes, the excessive reaction between inulin and the protein emulsifier will also cause the microcapsule product to turn reddish.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing polyunsaturated fatty acid oil microcapsules, characterized in that, Preparation of water-soluble wall materials encapsulating polyunsaturated fatty acid oils; including: (1) Heat inulin, sodium caseinate, whey protein and water to 50-68℃ and stir for 15-40 minutes to ensure thorough mixing; (2) Add filler and antioxidant and stir thoroughly to dissolve, obtaining an aqueous phase; (3) Add the polyunsaturated fatty acid oil to the aqueous phase obtained in step (2) and shear it to obtain an emulsion; (4) The emulsion obtained in step (3) is subjected to high-pressure homogenization and then spray-dried; (5) Add an anti-caking agent and dry mix; The moisture content of the microcapsules is 2-4%; apart from water, by mass, the raw materials of the microcapsules contain 40-55% polyunsaturated fatty acid oil, 6-15% sodium caseinate, 4-10% whey protein, 6.5-15% inulin, 3-6% antioxidant, 0.2-1% anti-caking agent, and the remainder is filler. The weight ratio of inulin to the sum of sodium caseinate and whey protein is (0.4-1):

1. The content of fatty acids with a carbon chain length of 20 or more and 4 or more unsaturated double bonds in the polyunsaturated fatty acid oil is not less than 40%.

2. The preparation method according to claim 1, characterized in that, The conditions for spray drying in step (4) are an inlet air temperature of 160-180℃ and an outlet air temperature of 60-80℃.

3. The preparation method according to claim 1 or 2, characterized in that, The antioxidants include one or more of sodium ascorbate, ascorbic acid, ascorbyl palmitate, vitamin E, and phospholipids; The anti-caking agent includes one or more of tricalcium phosphate, silicon dioxide, microcrystalline cellulose, and magnesium stearate; The filler includes one or both of solid corn syrup and maltodextrin.

4. A method for preparing polyunsaturated fatty acid oil microcapsules, characterized in that, Preparation of water-soluble wall materials encapsulating polyunsaturated fatty acid oils; including: (1) Heat inulin, sodium caseinate, whey protein and water to 50-68℃ and stir for 15-40 minutes to ensure thorough mixing; (2) Add filler, antioxidant, pH adjuster and / or chelating agent, stir thoroughly to dissolve, and obtain aqueous phase; (3) Add the polyunsaturated fatty acid oil to the aqueous phase obtained in step (2) and shear it to obtain an emulsion; (4) The emulsion obtained in step (3) is subjected to high-pressure homogenization and then spray-dried; (5) Add an anti-caking agent and dry mix; The moisture content of the microcapsules is 2-4%; apart from water, by mass, the microcapsule raw materials contain 40-55% polyunsaturated fatty acid oil, 6-15% sodium caseinate, 4-10% whey protein, 6.5-15% inulin, 3-6% antioxidant, 0.2-1% anti-caking agent, and the remainder are fillers, pH adjusters and / or chelating agents; The weight ratio of inulin to the sum of sodium caseinate and whey protein is (0.4-1):

1. The content of fatty acids with a carbon chain length of 20 or more and 4 or more unsaturated double bonds in the polyunsaturated fatty acid oil is not less than 40%.

5. The preparation method according to claim 4, characterized in that, The conditions for spray drying in step (4) are an inlet air temperature of 160-180℃ and an outlet air temperature of 60-80℃.

6. The preparation method according to claim 4 or 5, characterized in that, The antioxidants include one or more of sodium ascorbate, ascorbic acid, ascorbyl palmitate, vitamin E, and phospholipids; The anti-caking agent includes one or more of tricalcium phosphate, silicon dioxide, microcrystalline cellulose, and magnesium stearate; The filler includes one or both of solid corn syrup and maltodextrin.

7. The application of the preparation method according to any one of claims 1-6 in improving the stability of high oil-carrying polyunsaturated fatty acid oil microcapsules.

8. A polyunsaturated fatty acid oil microcapsule, characterized in that, It is obtained using the preparation method described in any one of claims 1-6.

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