Micrococcus algal oil embedding method with starch base as wall material

Abstract

The invention discloses a method for embedding microalgae oil by taking a starch base as a wall material. The method comprises the following steps: weighing starch sodium octenylsuccinate, slowly adding the starch sodium octenylsuccinate into single distilled water, heating and stirring until the starch sodium octenylsuccinate is completely dissolved to obtain a water-phase solution; the preparation method comprises the following steps: weighing algae oil of micrococcus, absolute ethyl alcohol and fatty acid monoglyceride, mixing and stirring to obtain an oil phase solution; stirring the water phase solution under the condition that the speed is 10000 to 12000 r / min, then slowly adding the oil phase solution into the water phase solution, and then continuously stirring for 10 to 20 minutes to obtain an emulsion; freezing the emulsion at-80 DEG C for 12 hours, then carrying out vacuum freeze drying for 72 hours, then crushing to obtain microcapsule powder coated with micrococcus oil, and sealing and storing the microcapsule powder. According to the method, active substances of the micrococcus faecalis oil are not damaged, the embedding rate is good, a high-temperature environment is not used in the production process, operation is easy, and the method is suitable for large-scale processing and production.

Description

Technical Field

[0001] The invention belongs to the technical field of food microcapsules, and in particular relates to a method for embedding Nannochloropsis algae oil using starch as a wall material. Background Art

[0002] Research has found that Pseudo-Nanochloa has a strong photosynthetic capacity and can store a lot of oil, of which unsaturated fatty acids account for most of the oil. Pseudo-Nanochloa oil is rich in ω-3 polyunsaturated fatty acids, which have physiological functions such as anti-platelet aggregation, anti-inflammation, lowering blood lipids, preventing arteriosclerosis, and anti-oxidation. At the same time, research has found that the Pseudo-Nanochloa oil obtained by fermentation has a fishy smell, is easily oxidized, and is difficult to carry, transport, process, store, and purify in semi-solid state.

[0003] Microcapsule technology was discovered in the 1950s and was used in carbonless copy paper in the early days. Nowadays, the application scope of microcapsule technology has gradually expanded to the fields of medicine, food, and chemical industry. Microcapsule technology can transform different types of substances such as liquids and gases into solid particles, which is very beneficial for processing, storage, transportation, covering up bad odors, changing the color of substances, having antioxidant properties, extending shelf life, and retaining the activity of active substances. In recent years, with the continuous emergence of new wall materials and core materials, the development of microcapsule technology has gradually matured. It can be divided into physical methods, chemical methods, and physical and chemical methods. The commonly used microcapsule preparation methods mainly include spray drying, freeze drying, molecular embedding, complex coacervation, and interfacial polymerization. The shape and size of microcapsules are closely related to the core material, wall material, and production method, and their application scope, advantages and disadvantages are different. Studies have found that the use of spray drying has huge consumption, expensive facilities and equipment, high cost, and a large area of ​​facilities, which is not conducive to cleaning, disassembly and installation, and low thermal efficiency. The molecular encapsulation method has the advantages of simple operation, low production cost, and not easy to absorb moisture and aggregate. Because the core material mainly contains unsaturated fatty acids, this encapsulation method limits other core material types to a certain extent. Its microcapsule encapsulation method, core material slow release conditions, release amount and process are closely related to the core material, wall material structure and the acceptance of the external functional groups of the wall material. The microcapsule encapsulation rate and yield are relatively low during the production process, which is not conducive to large-scale processing and production. The complex coacervation method has unfavorable factors such as high drying cost, difficult operation, too many restrictions on reaction conditions, difficulty in determining the core-wall ratio, and difficulty in accurately controlling the solution ion strength and concentration. Summary of the invention

[0004] In view of the above shortcomings, the present invention discloses a method for encapsulating Pseudo-Nanochloa algae oil using starch as the wall material, which not only ensures that the active substances in the Pseudo-Nanochloa algae oil are not destroyed, but also has a good encapsulation rate. Moreover, the production process does not use a high temperature environment, the operation is simple, and it is suitable for large-scale processing and production.

[0005] The present invention is achieved by adopting the following technical solutions: A method for embedding Nannochloropsis algae oil using starch as a wall material, comprising the following steps: (1) Weigh sodium starch octenyl succinate, slowly add it to mono-distilled water, heat and stir until completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of sodium starch octenyl succinate to mono-distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix and stir to obtain an oil phase solution, wherein the mass ratio of algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; (2) stirring the aqueous solution at a speed of 10,000 to 12,000 r / min, then slowly adding the oil solution to the aqueous solution, and then continuing to stir for 10 to 20 minutes to obtain an emulsion, wherein the volume ratio of the oil solution to the aqueous solution is 1:(3 to 9); (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum-freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with the Pseudo-Nannochloropsis algae oil, and the microcapsule powder is sealed and stored.

[0006] Furthermore, the sodium starch octenyl succinate is weighed in step (1) and slowly added to single distilled water at 70-80° C. and mixed, and then placed in a water bath at 80° C. and stirred until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution.

[0007] Furthermore, in step (1), the algae oil of Pseudochlorophyll, anhydrous ethanol and monoglycerol fatty acid ester are weighed, mixed and placed in a 55° C. water bath and stirred to obtain an oil phase solution.

[0008] Furthermore, the stirring speed in step (1) is 300 to 500 r / min.

[0009] Furthermore, the vacuum freeze-drying temperature in step (3) is -68°C and the pressure is 100 Pa.

[0010] Furthermore, in step (3), the moisture content in every 100 g of the microcapsule powder is less than 10 g.

[0011] Compared with the prior art, this technical solution has the following beneficial effects: 1. The present invention uses the algae oil of Pseudo-Nanochloa as the core material, sodium starch octenyl succinate as the wall material, and adjusts the appropriate core-to-wall ratio, emulsifier dosage, homogenization speed and homogenization time to prepare microcapsules encapsulating the algae oil of Pseudo-Nanochloa, and uses a vacuum freeze-drying method to dry the microcapsules. The microalgae oil is embedded in the internal cavity of sodium starch octenyl succinate (OSA starch) using food microcapsule technology. The formed microcapsules can effectively isolate the contact between the microalgae oil and the external environment, which is beneficial to improve the stability of the microalgae oil. The microalgae oil is encapsulated by embedding, which can slow down the oxidation of the core material. In addition, the preparation process does not pass through a high temperature environment, the active substance is not destroyed, the internal structure of the material remains unchanged, and the surface of the obtained microcapsules is smooth and the particle size is uniform.

[0012] 2. The process of the present invention is simple, easy to operate, and suitable for large-scale, automated production. In addition, the powdered microalgae oil microcapsules produced are more conducive to the storage, transportation, and application of algae oil in food processing and production. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 3 is a graph showing the relationship between the core-to-wall ratio of the microcapsules described in Experimental Example 1 and the embedding rate of the algae oil microcapsules.

[0014] Figure 2 This is a graph showing the relationship between the homogenization time and the embedding efficiency of algae oil microcapsules described in Experimental Example 2.

[0015] Figure 3 This is a graph showing the relationship between the homogenization speed and the algae oil microcapsule embedding rate described in Experimental Example 3.

[0016] Figure 4 This is a photograph of the appearance of the microcapsules obtained in Experimental Example 4.

[0017] Figure 5 This is a picture of the microcapsules obtained in Experimental Example 4 observed under an optical microscope.

[0018] Figure 6 This is a scanning electron microscope image of the sodium starch octenylsuccinate described in Experimental Example 4.

[0019] Figure 7 This is a scanning electron microscope image of the microcapsules obtained in Experimental Example 4.

[0020] Figure 8 This is a graph showing the results of the thermogravimetric analysis described in Experimental Example 4.

[0021] Fig. 9 This is the spectrum measured and analyzed by infrared spectrometer in Experimental Example 4. DETAILED DESCRIPTION

[0022] The present invention is further described by the following examples, but is not intended to be limiting of the present invention. Specific experimental conditions and methods not specified in the following examples are conventional methods commonly known to those skilled in the art.

[0023] Example 1: A method for embedding Nannochloropsis algae oil using starch as a wall material, comprising the following steps: (1) Weigh sodium starch octenyl succinate and slowly add it to 75°C distilled water and mix it, then place it in a water bath at 80°C and stir until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of the sodium starch octenyl succinate to the distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix them, place it in a water bath at 55°C and stir to obtain an oil phase solution, wherein the mass ratio of the algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; the stirring speed is 400 r / min; (2) stirring the aqueous solution at a speed of 12000 r / min, then slowly adding the oil phase solution into the aqueous solution, and then continuing to stir for 15 minutes to obtain an emulsion, wherein the volume ratio of the oil phase solution to the aqueous solution is 1:7; (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with Pseudo-Nanococcus algae oil, and the microcapsule powder is sealed and stored; the vacuum freeze-drying temperature is -68°C, the pressure is 100 Pa, and the moisture content of each 100g of the microcapsule powder is 6g.

[0024] Example 2: A method for embedding Nannochloropsis algae oil using starch as a wall material, comprising the following steps: (1) Weigh sodium starch octenyl succinate and slowly add it to 70°C distilled water and mix it, then place it in a water bath at 80°C and stir until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of the sodium starch octenyl succinate to the distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix them, place it in a water bath at 55°C and stir them to obtain an oil phase solution, wherein the mass ratio of the algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; the stirring speed is 300 r / min; (2) stirring the aqueous solution at a speed of 10000 r / min, then slowly adding the oil phase solution into the aqueous solution, and then continuing to stir for 10 minutes to obtain an emulsion, wherein the volume ratio of the oil phase solution to the aqueous solution is 1:3; (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with Pseudo-Nanococcus algae oil, and the microcapsule powder is sealed and stored; the vacuum freeze-drying temperature is -68°C, the pressure is 100 Pa, and the moisture content of each 100g of the microcapsule powder is 8g.

[0025] Example 3: A method for embedding Nannochloropsis algae oil using starch as a wall material, comprising the following steps: (1) Weigh sodium starch octenyl succinate and slowly add it to 78°C distilled water and mix it, then place it in a water bath at 80°C and stir until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of the sodium starch octenyl succinate to the distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix them, place it in a water bath at 55°C and stir them to obtain an oil phase solution, wherein the mass ratio of the algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; the stirring speed is 350 r / min; (2) stirring the aqueous solution at a speed of 11000 r / min, then slowly adding the oil solution into the aqueous solution, and then continuing to stir for 15 minutes to obtain an emulsion, wherein the volume ratio of the oil solution to the aqueous solution is 1:8; (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with Pseudo-Nanococcus algae oil, and the microcapsule powder is sealed and stored; the vacuum freeze-drying temperature is -68°C, the pressure is 100 Pa, and the moisture content of each 100g of the microcapsule powder is 8g.

[0026] Example 4: A method for embedding Nannochloropsis algae oil using starch as a wall material, comprising the following steps: (1) Weigh sodium starch octenyl succinate and slowly add it to 80°C distilled water and mix it, then place it in an 80°C water bath and stir until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of the sodium starch octenyl succinate to the distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix them, place it in a 55°C water bath and stir them to obtain an oil phase solution, wherein the mass ratio of the algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; the stirring speed is 500 r / min; (2) stirring the aqueous solution at a speed of 13000 r / min, then slowly adding the oil phase solution into the aqueous solution, and then continuing to stir for 20 minutes to obtain an emulsion, wherein the volume ratio of the oil phase solution to the aqueous solution is 1:9; (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with Pseudo-Nanococcus algae oil, and the microcapsule powder is sealed and stored; the vacuum freeze-drying temperature is -68°C, the pressure is 100 Pa, and the moisture content in every 100g of the microcapsule powder is 10 g.

[0027] Experimental Example 1: Microcapsule powder encapsulated with Nannochloropsis algae oil was prepared according to the method of the present invention, and the effect of the core-wall ratio on the embedding rate of algae oil microcapsules was investigated. The specific steps are as follows: (1) Weigh sodium starch octenyl succinate and slowly add it to 75°C distilled water and mix it, then place it in a water bath at 80°C and stir until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of the sodium starch octenyl succinate to the distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix them, place it in a water bath at 55°C and stir to obtain an oil phase solution, wherein the mass ratio of the algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; the stirring speed is 400 r / min; (2) stirring the aqueous solution at a speed of 12000 r / min, then slowly adding the oil phase solution into the aqueous solution, and then continuing to stir for 15 minutes to obtain an emulsion, wherein the volume ratio of the oil phase solution to the aqueous solution is 1:3, 1:5, 1:7, or 1:9; (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with Pseudo-Nanococcus algae oil, and the microcapsule powder is sealed and stored; the vacuum freeze-drying temperature is -68°C, the pressure is 100 Pa, and the moisture content of each 100g of the microcapsule powder is 6g.

[0028] See attached Figure 1 With the increase of the wall material ratio, the embedding rate of the microalgae oil microcapsules increased rapidly to the highest point and then slowly decreased. When the core-to-wall ratio was 1:7, the embedding rate reached the maximum value, which was 96.05%; with the further increase of the core-to-wall ratio, the embedding rate began to decrease. This is because when the core-to-wall ratio was 1:7, the utilization rate of the microalgae oil on the internal cavity of sodium starch octenyl succinate was the highest, which was exactly the optimal loading amount. The microcapsules formed by this ratio had the highest stability and embedding rate; with the change of different core-to-wall ratios, excessive sodium starch octenyl succinate and microalgae oil did not participate in the embedding process, and were easy to agglomerate with other substances to form block deposits or adhere to the surface of microcapsule particles, increasing the oil content on the particle surface, thereby reducing the embedding rate, which to a certain extent can increase the difficulty of forming microcapsule particles and drying microcapsule solutions.

[0029] Experimental Example 2: Microcapsule powder coated with Nannochloropsis algae oil was prepared according to the method of the present invention, and the effect of homogenization time on the preparation of microalgae oil microcapsules was investigated. The specific steps are as follows: (1) Weigh sodium starch octenyl succinate and slowly add it to 75°C distilled water and mix it, then place it in a water bath at 80°C and stir until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of the sodium starch octenyl succinate to the distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix them, place it in a water bath at 55°C and stir to obtain an oil phase solution, wherein the mass ratio of the algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; the stirring speed is 400 r / min; (2) stirring the aqueous solution at a speed of 10000 r / min, then slowly adding the oil phase solution into the aqueous solution, and then continuing to stir for 5 min, 10 min, 15 min or 20 min to obtain an emulsion, wherein the volume ratio of the oil phase solution to the aqueous solution is 1:7; (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with Pseudo-Nanococcus algae oil, and the microcapsule powder is sealed and stored; the vacuum freeze-drying temperature is -68°C, the pressure is 100 Pa, and the moisture content of each 100g of the microcapsule powder is 6g.

[0030] See attached Figure 2 When the homogenization time of microcapsules was prolonged, the embedding rate curve of microcapsules increased rapidly at first and then decreased. When the homogenization time was 15 min, the embedding rate was 91.63%, reaching the highest. With the extension of homogenization time, the embedding rate gradually decreased. When the homogenization time was 25 min, the embedding rate was 65.68%. This is because the homogenization time is closely related to the binding reaction between the microalgae oil in the microcapsule solution and the sodium starch octenyl succinate. If the time is too short, the chemical bonds between the microcapsule components are not stable. If the time is too long, the microalgae oil can overflow through the surface gaps of the sodium starch octenyl succinate. Therefore, the optimal homogenization time is 15 min.

[0031] Experimental Example 3: Microcapsule powder coated with Nannochloropsis algae oil was prepared according to the method of the present invention, and the effect of homogenization speed on the preparation of microalgae oil microcapsules was investigated. The specific steps are as follows: (1) Weigh sodium starch octenyl succinate and slowly add it to 75°C distilled water and mix it, then place it in a water bath at 80°C and stir until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of the sodium starch octenyl succinate to the distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix them, place it in a water bath at 55°C and stir to obtain an oil phase solution, wherein the mass ratio of the algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; the stirring speed is 400 r / min; (2) stirring the aqueous solution at a speed of 8000 r / min, 10000 r / min, 12000 r / min, and 14000 r / min, then slowly adding the oil phase solution to the aqueous solution, and then continuing to stir for 15 minutes to obtain an emulsion, wherein the volume ratio of the oil phase solution to the aqueous solution is 1:7; (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with Pseudo-Nanococcus algae oil, and the microcapsule powder is sealed and stored; the vacuum freeze-drying temperature is -68°C, the pressure is 100 Pa, and the moisture content of each 100g of the microcapsule powder is 6g.

[0032] See attached Figure 3 As the homogenization speed increases, the embedding rate curve of the microcapsules increases slowly first and then decreases rapidly. At 12000r / min, the embedding rate is 94.95%, reaching the highest. Subsequently, the homogenization speed is increased to 13000r / min, and it is found that the microcapsule embedding rate decreases. This is because the homogenization speed is too high, which easily breaks up the particles that successfully embed the microcapsules, and the hydrophobic and hydrogen bonding forces between the microalgae oil and the sodium starch octenyl succinate make them appear broken and fail to form complete microcapsule particles. The dispersed microalgae oil and sodium starch octenyl succinate aggregate or exist independently, resulting in an increase in the surface oil content and a decrease in the embedding rate. Reducing the homogenization speed may lead to uneven distribution of the microalgae oil in the microcapsule solution and incomplete dispersion of the successfully embedded microcapsule particles, resulting in a microcapsule product with a heavy powdery granular feel and more lumps.

[0033] According to the experimental data in Experimental Examples 1 to 3, the response surface methodology was used to optimize the experiment. The three factors of core-to-wall ratio, homogenization time, and homogenization speed were set as independent variables, and the embedding rate and surface oil content were used as response values. A three-factor and three-level response surface experiment was designed to optimize the preparation process of microalgae oil microcapsules. The experimental factors and levels are shown in Table 1, and the response surface analysis results are shown in Table 2.

[0034] Table 1 Factor levels of response surface experiment

[0035] Table 2 Response surface analysis results

[0036] According to the factor level table in Table 1, the experiment has 3 single factors and 9 experimental points are designed. The results are shown in Table 2. Taking the embedding rate as an indicator, it can be seen from Table 2 that in the orthogonal test, (A) the core-to-wall ratio has the greatest impact on the embedding rate, R (A) is 1.523; (C) the homogenization time has the second greatest impact on the embedding rate, R (C) is 0.160; (B) the homogenization speed has the least impact on the embedding rate, R (B) is 0.386; therefore, the influence of factors on the test results can be ranked as follows: (A) > (C) > (B). The range of the error column is 0.306, which is not greater than the maximum factor range and is in the middle range. Therefore, it can be shown that there is no ignored interaction between the factors and no important factors affecting the test results are ignored. From the attached Figure 1 It can be seen that with the increase of core-to-wall ratio, the embedding rate first increases and then decreases; Figure 2 It can be seen that with the increase of homogenization time, the embedding first increases slowly and then decreases rapidly; Figure 3 It can be seen that with the increase of homogenization speed, the embedding rate changes from a rapid decline to a slow decline. Therefore, taking the embedding rate as an indicator, the optimal factor level is: A2B3C3, that is, the core-wall ratio is 1:7, the homogenization time is 15 min, and the homogenization speed is 12000 r / min.

[0037] The method for determining the embedding efficiency and surface oil of the microcapsule powder described in Experimental Examples 1 to 3 is as follows: weigh 0.2 g (M) of microcapsule sample and place it in a straight bottle, add 3 mL of petroleum ether, shake it gently for 1 min to mix it evenly, then transfer it to filter paper for filtration, take 3 mL of petroleum ether several times to wash the straight bottle and filter paper, wash twice in total, and collect the filtrate into a clearly marked beaker (M 1 ) and dried in an electric drying oven at 105°C until constant weight (M 2 ).

[0038] The surface oil content is calculated as follows: Surface oil content = (M 2 -M 1 ) / M×100%, where M is the mass of microalgae oil microcapsules (g); M 1 is the mass of the empty beaker at a constant weight (g); M 2 is the mass (g) of the beaker and the oil (excluding the microcapsule residue) after constant weight drying.

[0039] The embedding efficiency of microalgae oil microcapsules was calculated by the following formula: EF = (T-Y) / T × 100%, where EE is the embedding efficiency of microcapsules (%); T is the total oil content (%); and Y is the surface oil content (%).

[0040] Each experiment was performed in triplicate, and the results were expressed as mean ± standard deviation. Origin Pro was used to process and plot the data.

[0041] Experimental Example 4: Microcapsules encapsulated with Pseudochlorophyll algae oil were prepared according to the method described in Example 1, and the sensory, physicochemical properties, microstructure, thermal stability and spectrum of the obtained microcapsules were measured respectively. Each group of experiments was conducted in parallel three times, and the results were expressed as mean ± standard deviation. Microsoft Excel and Origin Pro were used to process and plot the data, and SPSS Statistics was used for statistical analysis. The specific steps are as follows: S1. Use the sensory requirements in "QB / T 5632-2021 Docosahexaenoic acid oil powder" to conduct sensory evaluation of microcapsules. The sensory evaluation table of microcapsules is shown in Table 3 and Attachment Figure 4 The obtained microcapsules have a yellow-green appearance, are in powder form, have a relatively fine powder quality, have no large lumps, and have a slight seaweed smell.

[0042] Table 3 Sensory evaluation of microcapsules

[0043] S2. The physical and chemical properties of the microcapsules were measured according to the following steps. The specific results are shown in Table 4: S21. Weigh 0.1 g of microcapsule powder, add 10 ml of distilled water, stir and dilute, so that the microcapsules are evenly distributed in the distilled water, use a dropper to absorb the sample solution and slowly inject it into the sample pool. The optimal sampling method is to take a small sampling amount, increase the sampling times, and take multi-point sampling. The particle size of sodium starch octenylsuccinate and microcapsules is measured by laser particle size analyzer.

[0044] S22, weigh 2.0 g of microalgae oil microcapsules, transfer them to a measuring cylinder, tap them gently to make them sink naturally, read and record the volume (V1) value of the microcapsules, and calculate the density of the microcapsules per unit volume; based on the experimental operation of loose density, tap them gently again, repeat the above operation until the volume value before and after tapping remains unchanged, read and record the volume (V2) of the microcapsules, and calculate the density of the microcapsules per unit volume; The density is calculated as: 1 (loose density) = m / V1; P 2 (shock density) = m / V2, Where P 1 is the loose density of the microcapsules (g / cm 3 );P 2 is the tap density of the microcapsules (g / cm 3); m is the mass of microcapsules (g); V1 is the volume of the first microcapsules (mL); V2 is the volume of the second microcapsules (mL); The loose density and the tapped density can be used to calculate the Carr index (C) and Hausner ratio (HR) of the microcapsules to evaluate the fluidity of the microcapsules. The calculation formula is: Carr index (C) = (P 2 -P 1 ) / P 1 ×100; Hausner Ratio (HR) = P 2 / P 1 , where P 1 is the compacted density of microcapsules (g / cm 3 );P 2 is the loose density of microcapsules (g / cm 3 ).

[0045] S23, weigh 0.5g of microalgae oil microcapsules, add 20mL of distilled water and stir to dissolve, transfer the solution to a centrifuge tube, set the basic parameters of the centrifuge as temperature: 4℃; speed: 6000 r / min; time: 10 min, after the centrifugation, remove the supernatant, repeat the above steps until the supernatant is clear, wash the precipitate with a little distilled water into an evaporating dish, and dry it at 105℃ to constant weight; the solubility calculation formula of the microcapsule is: S= (m 2 -m 1 ) / m×100%, where S is the solubility of the sample (%); m is the mass of the microcapsule in grams (g); m 1 is the mass of the evaporating dish in grams (g); m 2 is the mass of the evaporating dish and microcapsules after drying, in grams (g).

[0046] S24, take a dry and constant weight weighing bottle, weigh 2.0 g of microalgae oil microcapsules, place the weighing bottle containing the microcapsules in a vacuum drying oven at 105 ℃ and heat and dry for 6 hours. The bottle cap should be tilted and the edge of the bottle mouth. After drying, it should be immediately moved into a dryer to cool for 0.5 hours and weigh. Each drying time is reduced to half of the previous drying time. Repeat the above operation. The difference in mass between the two weighings before and after drying does not exceed 2 mg, that is, constant weight is reached; the moisture content in the microcapsules is calculated as follows: X = (m 1 -m 2 ) / (m 1 -m 3 )×100%, where X is the water content in the microcapsule (%); m 1 is the mass of the weighing bottle and the sample (g); m 2 is the mass of the weighing bottle and the sample after drying (g); m 3 is the mass of the weighing bottle (g).

[0047] S25. Weigh 1.0 g of microcapsules, transfer them to a clean and dry crucible, burn them on a low fire in an electric furnace to completely carbonize the microcapsules in the crucible to a smokeless state, transfer them to a 550°C high-temperature furnace and burn them for 5 h. When the temperature drops to 200°C, transfer them to a dryer to cool for 30 min and weigh them. The ash content of microcapsules is calculated by the formula: X 2 =(m 1 -m 2 ) / (m 3 -m 2 )×100%, where X 2 is the ash content in the sample (%); m 1 is the mass of the crucible and ash (g); m 2 is the mass of the crucible (g); m 3 is the mass of the crucible and the sample (g).

[0048] Table 4 Physical and chemical properties of microcapsules

[0049] The results of various physical and chemical indexes in Table 4 show that the solubility of the microalgae oil microcapsules prepared by the present invention is high, and the moisture content, ash content, House sodium ratio and fluidity level are low, indicating that the product dissolves quickly at room temperature and has high dissolution properties; the moisture content inside the microcapsules is low, which is conducive to storage; the proportion of organic matter in the microcapsules is much higher than that of inorganic matter; the microcapsules have good fluidity and slightly higher viscosity; the above physical and chemical index values ​​can prove that the microalgae oil microcapsules have high practical value.

[0050] S3. Take a small amount of microcapsules and dissolve them in 1 mL of single distilled water and stir evenly. Draw a small amount of solution with a dropper and drop it on the center of the glass slide. Cover it with a coverslip and observe it under an optical microscope. At the same time, take a small amount of microcapsules and OSA starch samples and place them on the conductive glue respectively. Blow away the excess sample powder on the sample platform with an ear-cleaning bulb. After the sample platform is treated with gold by an ion sputtering instrument, place it in the sample chamber of the scanning electron microscope. After the sample chamber is evacuated and the sample in the chamber is subjected to high-voltage treatment, adjust the sample stage to a suitable position and observe the sample image through the system display interface. According to the attached Figures 5 to 7As shown in the figure, the shape and size of the microcapsules are similar. Affected by the interaction force of the long chains in sodium octenyl succinate starch, the microalgae oil microcapsules are spherical or ellipsoidal in shape, and there is agglomeration between the microcapsule particles. Compared with sodium octenyl succinate starch without microalgae oil, the viscosity between sodium octenyl succinate starch increases after adding microalgae oil. The reason for the increased viscosity is that the electrostatic and hydrophobic interaction between sodium octenyl succinate starch in the solution and the unembedded microalgae oil is enhanced, thereby reducing the oil-water interfacial tension and increasing the thickness of the interfacial film, making the microcapsule interfacial film not easy to break, and promoting more microalgae oil to be embedded. In the electron microscope image of the microalgae oil microcapsules, it can be seen that there are large irregular blocks. This is because the homogenization speed and time are insufficient, resulting in the failure of oil and starch to disperse in time, and sodium octenyl succinate starch and microalgae oil are tightly agglomerated together through electrostatic action. By adjusting the parameters of the electron microscope, it can be observed from the electron microscope that the surface of the microcapsule particles is relatively smooth, without obvious pits and gaps on the surface, indicating that the solute in the solution has a strong water-holding capacity during the drying process. The effective ingredients in the solute will be entangled with each other through van der Waals forces, which will promote the drying speed of the microcapsule solution and form a smooth protective film at the same time, reducing the contact between the core material inside the microcapsule and the external environment, thereby maintaining the stability of the active substances in the core material during storage.

[0051] S4. Accurately weigh a certain amount of microalgae oil microcapsules and place them in a container. Set the nitrogen flow rate of the thermogravimetric analyzer to 20 mL / min, the heating rate to 10 °C / min, and the heating range to 50-600 °C. Obtain the weight change of the microcapsules as the instrument setting parameters change. Thermogravimetric analysis (TGA) of microcapsules. Thermogravimetric analysis (TGA) refers to the program heating of a sample under specific conditions to measure the curve of the sample mass changing with temperature. It can be used to analyze the thermal degradation process of the sample and its thermal stability. This experiment examined the TGA curves of sodium starch octenyl succinate, microalgae oil, and algae oil microcapsules. Figure 8It can be seen from the TGA curves in that when the temperature range is 50-150 ℃, the mass changes of the three samples are slow, mainly due to water evaporation, volatile substances and some small molecules escaping. At this stage, the mass of algae oil microcapsules decreases by 7.8%; at the same time, algae oil has a small gradient decline curve at 150 ℃, indicating that some volatile substances in algae oil escape; in the curve of microcapsules, the curve remains stable in the range of 120-150 ℃ and is basically consistent with the TGA curve of OSA starch, indicating that there is no obvious volatilization of algae oil in the microcapsule particles except free water; when the temperature is in the range of 150-350 ℃, the TGA curve drops sharply, and the mass of microcapsules loses 75.36% at this stage. The main reason is that most of the wall materials begin to undergo thermal decomposition, the chemical bonds in the sodium octenyl succinate starch molecules break to produce volatile gases, and the core material also cracks and evaporates. When the temperature is greater than 350 When the temperature reaches 180℃, the change of microcapsule quality slows down, mainly because the remaining sample is completely carbonized and the thermal decomposition is basically completed; the above results show that the structure of algae oil microcapsules is relatively stable before 180℃, and the thermal stability is good. The embedding of sodium octenyl succinate starch helps to reduce the volatilization of algae oil within a certain temperature range, making it suitable for food processing and production operations. S5. Take a small amount of dry and dispersed sodium octenyl succinate starch and microalgae oil microcapsule powder, move it directly to the measurement optical platform of the Fourier infrared spectrometer for measurement, set its instrument parameters, and scan the range of 500~4000 cm -1 , scanning frequency is 2cm -1 , the number of scans is 32; the infrared spectra of sodium octenyl succinate starch raw material and sodium octenyl succinate starch in microalgae oil microcapsules were measured by Fourier infrared spectroscopy, and the position changes of the functional groups of the two were analyzed, thereby effectively understanding the embedding effect of microalgae oil microcapsules. Fig. 9 It can be obtained that sodium starch octenylsuccinate is 1010.52 cm -1 、1347.03 cm -1 、1647.88 cm -1 、2926.45 cm -1 、3311.66 cm -1 The characteristic peaks are formed at 2926.45 cm-1, and the sodium starch octenyl succinate is generated by CH stretching and stretching vibration respectively. -1 、3311.66 cm -1 The characteristic peaks at 1347.03 cm-1 are caused by CO and C=O. -1 、1647.88 cm -1The characteristic peak formed by stretching at 1015.82 cm-1 was obtained by stretching the microalgae oil microcapsules and sodium octenyl succinate starch. The absorption peaks of the microalgae oil microcapsules and sodium octenyl succinate starch were in the same characteristic spectral band, indicating that the properties of the microalgae oil were not changed after being embedded into microcapsules by sodium octenyl succinate starch. Compared with the characteristic peak of sodium octenyl succinate starch, the absorption peak of the microalgae oil microcapsules at 1015.82 cm-1 was obtained by stretching the microalgae oil microcapsules and sodium octenyl succinate starch. -1 、1350.89 cm -1 、1740.44 cm -1 、2927.41 cm -1 、3337.69 cm -1 The characteristic peak is weakened and shifted due to the vibration of chemical bonds, which significantly indicates that sodium starch octenyl succinate successfully encapsulates microalgae oil molecules. It is found that the microalgae oil microcapsules have a peak at 3337.69 cm -1 The characteristic peak area produced is smaller than that produced by sodium starch octenyl succinate at this point. This is because the starch in the microcapsule solution does not undergo covalent cross-linking reaction with the oil, the oil has been completely encapsulated, and the remaining sodium starch octenyl succinate does not participate too much in the reaction to produce new chemical bonds; the change in the characteristic absorption peaks of the functional groups related to sodium starch octenyl succinate in the spectrum of microalgae oil microcapsules shows that sodium starch octenyl succinate has successfully encapsulated microalgae oil as a wall material.

[0052] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for embedding Nannochloropsis algae oil using starch as the wall material, Features: The following steps are involved: (1) Weigh sodium starch octenyl succinate, slowly add it to mono-distilled water, heat and stir until completely dissolved to obtain an aqueous phase solution, wherein the mass ratio of sodium starch octenyl succinate to mono-distilled water is 2:12; weigh algae oil of Pseudo-Nanochloa spp., anhydrous ethanol and monoglycerol fatty acid ester, mix and stir to obtain an oil phase solution, wherein the mass ratio of algae oil, anhydrous ethanol and monoglycerol fatty acid ester is 10:50:1; (2) stirring the aqueous solution at a speed of 10,000 to 12,000 r / min, then slowly adding the oil solution to the aqueous solution, and then continuing to stir for 10 to 20 minutes to obtain an emulsion, wherein the volume ratio of the oil solution to the aqueous solution is 1:(3 to 9); (3) The emulsion is frozen at -80°C for 12 hours, and then vacuum-freeze-dried for 72 hours, and then crushed to obtain microcapsule powder encapsulated with the Pseudo-Nannochloropsis algae oil, and the microcapsule powder is sealed and stored.

2. The method for embedding Nannochloropsis algae oil using starch as the wall material according to claim 1, Features: In step (1), sodium starch octenyl succinate is weighed and slowly added to single distilled water at 70-80° C. and mixed, and then placed in a water bath at 80° C. and stirred until the sodium starch octenyl succinate is completely dissolved to obtain an aqueous phase solution.

3. The method for embedding Nannochloropsis algae oil using starch as the wall material according to claim 1, Features: In step (1), the algae oil of Pseudochlorophyll, anhydrous ethanol and monoglycerol fatty acid ester are weighed, mixed and placed in a 55° C. water bath and stirred to obtain an oil phase solution.

4. The method for embedding Nannochloropsis algae oil using starch as the wall material according to claim 1, Features: The stirring speed in step (1) is 300-500 r / min.

5. The method for embedding Nannochloropsis algae oil using starch as the wall material according to claim 1, Features: The vacuum freeze-drying temperature in step (3) is -68°C and the pressure is 100 Pa.

6. The method for embedding Nannochloropsis algae oil using starch as the wall material according to claim 1, Features: In step (3), the moisture content in every 100 g of the microcapsule powder is less than 10 g.

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