Arachidonic acid oil microcapsule with wall material containing soy protein peptide and preparation method thereof

Abstract

The application belongs to the technical field of food, and particularly relates to arachidonic acid oil microcapsules containing soybean protein peptides and a preparation method. The arachidonic acid oil microcapsules containing soybean protein peptides are prepared by a spray drying process, with a malt dextrin-small molecule soybean protein peptide composite system as a wall material and arachidonic acid oil as a core material. The mass ratio of the malt dextrin to the small molecule soybean protein peptide is 9:1. The mass ratio of the wall material to the core material is 2:1-5:2. The total solid content of the wall material and the core material is 30 wt%. The application changes the physical state of arachidonic acid oil, improves the convenience and applicability of the product, and delays the oxidative deterioration of oil from the source.

Description

Technical Field

[0001] This invention belongs to the field of food technology, specifically relating to an arachidonic acid oil microcapsule containing soybean protein peptides in its wall material and its preparation method. Background Technology

[0002] Arachidonic acid (ARA) is an omega-6 series long-chain polyunsaturated fatty acid and one of the essential fatty acids for the human body. It is mainly found in animal liver, fish oil, and egg yolks, but its production is far below market demand, and extraction is extremely difficult. However, the production of oils rich in arachidonic acid through microbial fermentation has been widely applied in industrial production. Arachidonic acid possesses important biological activities and nutritional functions and is widely used in food, medicine, health products, and cosmetics. It has functions such as promoting brain development in infants and young children, dilating blood vessels, participating in hematopoiesis and immune regulation, inducing and antagonizing inflammation, regulating neuroendocrine function, and promoting cell division, showing great market potential.

[0003] Oils high in arachidonic acid contain four unsaturated double bonds, making them sensitive to light and temperature. They are prone to oxidative rancidity during storage and therefore typically require storage at 2-8°C. This not only limits their storage and transportation but also affects their practical application in the food and pharmaceutical industries, potentially leading to reduced efficacy and safety risks. While adding antioxidants can extend the shelf life of arachidonic acid oils, this method is costly and lacks consumer acceptance, posing challenges to the commercial application of the product.

[0004] Microencapsulation technology is a technique that involves creating sealed or semi-permeable microcapsules from polymeric film-forming materials, and embedding functional core materials in different states within them, thereby forming sealed or partially permeable microparticles. When arachidonic acid oil is encapsulated into microcapsules, the wall material forms a protective barrier, effectively isolating it from external factors such as oxygen and light, delaying its oxidative rancidity, preventing nutrient loss and the formation of harmful substances, while also masking unpleasant flavors, improving palatability, and enhancing its physical form for easier storage and transportation, as well as improving its dispersibility in food.

[0005] Current research has included the preparation of arachidonic acid microcapsules-3 using modified starch and maltodextrin as wall materials, and the encapsulation of soybean salad oil using whey protein-glucose syrup-lactose as wall materials. Some studies have also explored the encapsulation of soybean salad oil using maltodextrin and hydrolyzed soybean protein as wall materials. However, the encapsulation technology for arachidonic acid oil with high unsaturated arachidonic acid content remains underdeveloped, hindering its widespread application in the food industry. Therefore, developing a microcapsule product for arachidonic acid oil with excellent wall material performance remains a pressing issue. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides arachidonic acid oil microcapsules containing soybean protein peptides as wall material and a preparation method thereof.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A microcapsule containing arachidonic acid oil with soybean protein peptides as the wall material is prepared by spray drying. The microcapsule product uses a maltodextrin-small molecule soybean protein peptide composite system as the wall material and arachidonic acid oil as the core material. The mass ratio of maltodextrin to small molecule soybean protein peptides is 9:1. The mass ratio of the wall material to the core material is 2:1-5:2. The total solids content of the wall material and the core material is 30 wt%.

[0008] The arachidonic acid oil is crude oil extracted from the mycelium of *Morchella alpina* obtained by fermentation using n-hexane as the extractant and Soxhlet extraction. The crude oil is then refined using traditional methods to obtain the finished arachidonic acid oil.

[0009] The small molecule soybean protein peptides are obtained by enzymatic hydrolysis of non-GMO soybean protein concentrate, and the molecular weights of different types of peptide molecules are mainly concentrated between 1000-2000 Da.

[0010] A method for preparing arachidonic acid oil microcapsules containing small molecule soybean protein peptides as the wall material includes the following steps: S1. Preparation of aqueous phase: Maltodextrin and small molecule soybean protein peptides were mixed at a mass ratio of 9:1 and dissolved in deionized water. The mixture was then stirred in a constant temperature water bath at 65℃ for 30 min to prepare the aqueous phase. S2. Oil phase preparation: Add emulsifier to the core material and stir in a 65°C constant temperature water bath until the emulsifier dissolves to prepare the oil phase; S3. Emulsion preparation: The oil phase is added to the aqueous phase and stirred at 65°C to fully mix the oil and aqueous phases. Stirring for 30 minutes yields a crude emulsion, which is then homogenized using a high-speed shear homogenizer. S4. Spray drying: The prepared emulsion is spray dried to obtain arachidonic acid oil microcapsules with a water content of 6-8%. Spray drying conditions: inlet air temperature 140-150℃, outlet air temperature 80-90℃, peristaltic pump speed 25rpm, fan frequency 35Hz.

[0011] This invention provides arachidonic acid oil microcapsules containing soybean protein peptides as wall material and a preparation method thereof, which have the following beneficial effects: 1. Modify the physical state of arachidonic acid oil to improve product convenience and applicability. Microencapsulation transforms liquid arachidonic acid oil into a powdered solid product, facilitating weighing, packaging, transportation, and uniform dispersion in food systems, overcoming the inconveniences of storing and processing liquid oils. The particle size distribution of the microcapsule product of this invention meets the requirements of the 2020 edition of the Chinese Pharmacopoeia regarding microcapsule particle size (1-250 μm), ensuring the applicability of the product in the food and pharmaceutical fields.

[0012] 2. Active chemical antioxidants slow down the oxidation and deterioration of oils at the source. Unlike traditional wall materials such as maltodextrin, which only function through physical isolation, small-molecule soybean protein peptides possess direct chemical antioxidant activity. After enzymatic hydrolysis, the hydrophobic amino acid residues and antioxidant peptides (such as peptides with molecular weights mainly concentrated in the 1000-2000 Da range) originally embedded within the protein's spatial structure are fully exposed and released. These peptides can effectively scavenge DPPH and ABTS cationic free radicals, exhibiting antioxidant activity comparable to glutathione (GSH). When arachidonic acid oil microcapsules face trace amounts of oxygen permeation during storage, the small-molecule soybean protein peptides, as components of the wall material, can actively capture and scavenge free radicals that have permeated into the wall material matrix, chemically blocking the chain-like auto-oxidation reaction of the oil. This "active chemical defense" mechanism complements the "physical isolation" barrier effect of the wall material, resulting in significantly better oxidative stability of the microcapsule products of this invention compared to existing technologies relying solely on physical encapsulation. Compared to unencapsulated arachidonic acid oil, the arachidonic acid oil microcapsule product of this invention exhibits a significantly reduced rate of oxidative rancidity under the same conditions, a smoother peroxide value change curve, and is far below the national standard limit (≤10 meq / kg), resulting in significantly enhanced storage stability and a significantly extended shelf life.

[0013] 3. Synergistic nutritional functions to achieve "functionalization of wall materials" This invention innovatively incorporates soybean small-molecule protein peptides, a bioactive component with high nutritional value, as a wall material, rather than using traditional inert wall materials. The molecular weight of the peptides in soybean small-molecule protein peptides is mainly concentrated between 1000-2000 Da. These small-molecule soybean protein peptides are not merely used as conventional wall material fillers, but rather as a multifunctional active wall material component that combines structural support, active antioxidant activity, interfacial stability, and synergistic nutrition. Soybean small-molecule protein peptides can be directly and rapidly absorbed in the small intestine without digestion, possessing independent absorption channels and not competing with free amino acids, resulting in absorption efficiency far exceeding that of free amino acids or intact proteins. Therefore, the microcapsule product of this invention provides functional arachidonic acid oils while simultaneously supplementing easily absorbed small-molecule protein peptides, achieving dual synergistic delivery of nutrition through "active oil components + small-molecule protein peptides," giving the product additional health benefits (such as aiding immune regulation and promoting tissue repair), significantly enhancing its added value as a functional food ingredient.

[0014] 4. Excellent process adaptability, enabling quality improvement across the entire supply chain. The soybean protein peptides selected in this invention have a molecular weight concentrated in the range of 1000-2000 Da. Peptides within this molecular weight range retain sufficient reactive groups (free amino groups) to participate in the Maillard reaction, while also possessing a suitable chain length to maintain good solubility and interfacial activity. This further enhances the emulsifying activity and film-forming properties of the wall material, making the spray drying process more stable, resulting in high product yield, uniform particle size, and good dispersibility. In contrast, proteins with excessively large molecular weights have significant steric hindrance and low reactivity, while peptides with excessively small molecular weights may lack sufficient intermolecular interactions and have poor film-forming properties. Therefore, the specific selection of the soybean protein peptide molecular weight range (1000-2000 Da) and the overall process constitute a synergistic and efficient complete technical solution. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the preparation process of arachidonic acid oil microcapsules containing soybean protein peptides in wall material according to the present invention. Figure 2 The graph shows the effect of the wall-to-core ratio of each embodiment on the encapsulation efficiency of the arachidonic acid oil microcapsules prepared by the present invention. Figure 3 Particle size distribution diagram of arachidonic acid oil microcapsules provided in Example 4 of this invention; Figure 4 This is a scanning electron microscope image of the arachidonic acid oil microcapsules provided in Example 4 of the present invention; Figure 5 This is a graph showing the change trend of peroxide value of arachidonic acid oil and its microcapsules during storage, as provided in Example 4 of the present invention. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0017] Example 1 This embodiment discloses an arachidonic acid oil microcapsule containing soybean protein peptides as the wall material and its preparation method. Figure 1 Its preparation process specifically includes the following steps: S1. Preparation of aqueous phase: Weigh 18.00g of maltodextrin and 2.00g of small molecule soybean protein peptide, add 100mL of distilled water, stir in a constant temperature water bath at 65℃ for 30min to obtain the aqueous phase; S2. Oil phase preparation: Weigh 0.18g of monoglyceride and 0.36g of sodium stearoyl lactylate, add them to 10.00g of arachidonic acid oil, and stir in a constant temperature water bath at 65℃ for 30min to obtain the oil phase. In this embodiment, the mass ratio of wall material to core material is 2:1; S3. Emulsion preparation: The oil phase is added to the aqueous phase and stirred at 65°C for 30 min to fully mix the oil and aqueous phases and obtain a crude emulsion. Then, the emulsion is homogenized for 3 min at 10,000 rpm using a high-speed shear homogenizer to obtain a uniform milky white emulsion without stratification. S4. Spray drying: The prepared milky white emulsion is spray dried to obtain a light yellow powdery arachidonic acid oil microcapsule product. The spray drying conditions are: inlet air temperature 180±5℃, outlet air temperature 110±5℃, peristaltic pump speed 25rpm, and fan frequency 35Hz.

[0018] In this embodiment, arachidonic acid oil is prepared by the following method: T1. Fermentation culture: Mortierella alpina CCTCC AF 2017012 (strain purchased from China Center for Type Culture Collection, strain number CCTCC AF 2017012) was used as the fermentation strain. After activation and seed culture, it was transferred to a fermenter for deep liquid fermentation. The fermentation temperature was 25-28℃, the pH was 6.0-7.0, the stirring speed was 150-250 r / min, the aeration ratio was 1:0.5-1:1 (v / v / min), and the fermentation cycle was 5-8 days to obtain a fermentation broth containing Mortierella alpina mycelium. T2. Mycelium collection: After fermentation, the fermentation broth was vacuum filtered to obtain wet mycelium, which was washed with deionized water and dried at 50-60℃ to constant weight to obtain dry mycelium. T3. Oil extraction: The dried mycelium was crushed and placed in a Soxhlet extractor. Hexane was used as the extractant and the mixture was heated and refluxed at 68-70℃ for 6-10 hours to obtain a hexane-oil mixture. The hexane was then removed by rotary evaporation to obtain crude oil. T4. Oil refining: The crude oil is successively degummed, deacidified, decolorized and deodorized to obtain the finished arachidonic acid oil; The degumming is hydration degumming; the deacidification is alkali refining deacidification; the decolorization is adsorption decolorization using activated clay at 90-110℃ under vacuum for 20-30 minutes; and the deodorization is steam distillation deodorization at 180-200℃ under absolute pressure ≤500Pa for 60-120 minutes.

[0019] This study employs a low-temperature deodorization process of 180-200℃ to ensure effective deodorization while maximizing the preservation of the structural integrity of ARA. The Soxhlet extraction temperature is 68-70℃: the boiling point of n-hexane is 68-70℃, ensuring extraction efficiency while avoiding oil oxidation caused by excessively high temperatures. The refined oil quality indicators are: acid value ≤1.5mgKOH / g, peroxide value ≤5.0meq / kg, ensuring the core material is in a low-oxidation state before microencapsulation.

[0020] Example 2 The similarities between this embodiment and Embodiment 1 will not be repeated here. The difference is that in this embodiment, 20.25g of maltodextrin, 2.25g of small molecule soybean protein peptide and 7.50g of arachidonic acid oil are weighed, that is, the mass ratio of wall material to core material is 3:1.

[0021] Example 3 The similarities between this embodiment and Embodiment 1 will not be repeated here. The difference is that in this embodiment, 21.60g of maltodextrin, 2.40g of small molecule soybean protein peptide and 6.00g of arachidonic acid oil are weighed, that is, the mass ratio of wall material to core material is 4:1.

[0022] Example 4 The similarities between this embodiment and Embodiment 1 will not be repeated here. The difference is that in this embodiment, 22.50g of maltodextrin, 2.50g of small molecule soybean protein peptide and 5.00g of arachidonic acid oil are weighed, that is, the mass ratio of wall material to core material is 5:1.

[0023] Example 5 The similarities between this embodiment and Embodiment 1 will not be repeated here. The difference is that in this embodiment, 19.26g of maltodextrin, 2.14g of small molecule soybean protein peptides and 8.60g of arachidonic acid oil are weighed, that is, the mass ratio of wall material to core material is 5:2.

[0024] Figure 2 The effect of the wall-to-core ratio on the encapsulation efficiency of the arachidonic acid oil microcapsules prepared according to this invention is shown in the examples. Figure 2 It can be seen that as the mass ratio of wall material to core material gradually increases from 2:1 to 5:1, the encapsulation rate rises continuously from 70.26% to a peak of 90.84%. However, when the mass ratio is further adjusted to 5:2, the encapsulation rate decreases to 83.77%. This trend may be because, within the mass ratio range of 2:1 to 5:1, as the proportion of wall material (maltodextrin and soybean protein peptides) increases, more wall material can fully encapsulate the arachidonic acid oil in the core material, reducing the probability of core material exposure or loss, thus improving the encapsulation effect. However, when the mass ratio reaches 5:2, an excessively high proportion of wall material may lead to an overly viscous or unevenly dispersed wall material system, making it difficult to uniformly encapsulate the core material. This can even result in wall material aggregation and insufficient core material encapsulation, ultimately leading to a decrease in the encapsulation rate. This also indicates that a wall-to-core ratio of 5:1 is a better ratio that balances wall material encapsulation capacity and system stability in this system.

[0025] Figure 3 This is a particle size distribution diagram of the arachidonic acid oil microcapsules provided in Example 4 of the present invention. From... Figure 3 It can be seen that the particle size range of the arachidonic acid oil microcapsules is 2.67-42.9 μm, with an average particle size of 22.2 μm, which meets the requirements of the 2020 edition of the Chinese Pharmacopoeia for microcapsule particle size (1-250 μm). The multi-peaked particle size distribution of the arachidonic acid oil microcapsules indicates that the microcapsule particle size is not uniform, which may be caused by the unstable pressure of the atomizer during the spray drying process.

[0026] Figure 4 This is a scanning electron microscope image of the arachidonic acid oil microcapsules provided in Example 4 of the present invention. From... Figure 4 The microcapsule powder particles were clearly observed to have a regular spherical structure. Some sample particles also showed some wrinkles or depressions, but no obvious cracks or fissures, which better protected the core material. The wrinkles in the particles may be a result of the microcapsules shrinking due to the rapid evaporation of moisture during spray drying. Furthermore, the arachidonic acid oil microcapsule powder particles were uneven in size, which is related to the particle size distribution (…). Figure 3 The results are consistent.

[0027] Figure 5This is a graph showing the peroxide value changes of the arachidonic acid oil provided by this invention and the arachidonic acid oil microcapsules provided in Example 4 during storage. At storage day 0, the peroxide values ​​of the arachidonic acid oil and its microcapsules were 4.46 meq / kg and 4.80 meq / kg, respectively, indicating that the arachidonic acid oil was not significantly oxidized during the emulsification and spray drying stages. At storage temperature of 30°C, the peroxide value of the arachidonic acid oil and its microcapsules increased slowly. After 35 days of storage, the peroxide value of the arachidonic acid oil slowly increased to 12.67 meq / kg, while the peroxide value of the arachidonic acid oil microcapsules was only 8.70 meq / kg, indicating that the oxidation rate of the arachidonic acid oil microcapsules was very slow. After only 5 days of storage at 70℃, the peroxide value of arachidonic acid oil rapidly increased to 38.93 meq / kg, indicating severe rancidity. This exceeded the peroxide value limit set by the National Health Commission for arachidonic acid oil (≤0.25g / 100g, i.e., 10 meq / kg), rendering it unsuitable for use and unsafe for consumption. In contrast, the peroxide value change curve of the arachidonic acid oil microcapsules during storage at 70℃ was relatively gentle, indicating a lower degree of oxidation. This suggests that the dense structure formed by the wall material effectively encapsulated the arachidonic acid oil, preventing contact between oxygen, moisture, and heat with the core material, thus slowing down the oxidation rate of the arachidonic acid oil in the core material.

[0028] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A microcapsule containing arachidonic acid oil and soybean protein peptides as the wall material, characterized in that, Microcapsule products were prepared by spray drying using a maltodextrin-small molecule soybean protein peptide composite system as the wall material and arachidonic acid oil as the core material. The mass ratio of maltodextrin to small molecule soybean protein peptide was 9:1; the mass ratio of wall material to core material was 2:1-5:2; and the total solids content of the wall material and core material was 30wt%.

2. The arachidonic acid oil microcapsule containing soybean protein peptides as a wall material according to claim 1, characterized in that: The arachidonic acid oil is crude oil extracted from the mycelium of *Morchella alpina* obtained by fermentation using n-hexane as the extractant and Soxhlet extraction. The crude oil is then refined using traditional methods to obtain the finished arachidonic acid oil.

3. The arachidonic acid oil microcapsule containing soybean protein peptides as a wall material according to claim 1, characterized in that: The small molecule soybean protein peptides are obtained by enzymatic hydrolysis of non-GMO soybean protein concentrate, and the molecular weights of different types of peptide molecules are mainly concentrated between 1000-2000 Da.

4. A method for preparing arachidonic acid oil microcapsules containing soybean protein peptides as a wall material according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Aqueous phase preparation: Weigh a certain amount of wall material and dissolve it in deionized water. Stir in a constant temperature water bath at 65℃ for 30 minutes to prepare the aqueous phase. S2. Oil phase preparation: Add emulsifier to the core material and stir in a 65°C constant temperature water bath until the emulsifier dissolves to prepare the oil phase; S3. Emulsion preparation: The oil phase is added to the aqueous phase and stirred at 65°C for 30 min to fully mix the oil and aqueous phases, and finally a crude emulsion is obtained. Then, the emulsion is homogenized using a high-speed shear homogenizer. S4. Spray drying: The prepared emulsion is spray dried to obtain arachidonic acid oil microcapsules with a water content of 6-8%; the spray drying conditions are: inlet air temperature 140-150℃, outlet air temperature 80-90℃, peristaltic pump speed 25rpm, and fan frequency 35Hz.

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