CN113647474B

CN113647474B - Preparation method of broom corn millet shell oil microcapsule

Info

Publication number: CN113647474B
Application number: CN202111002139.6A
Authority: CN
Inventors: 牛广财; 朱丹; 朱立斌; 苗欣月; 魏文毅; 贾建; 杨楠; 徐瑞航; 王思溥; 宁志雪
Original assignee: Heilongjiang Bayi Agricultural University
Current assignee: Heilongjiang Bayi Agricultural University
Priority date: 2021-08-30
Filing date: 2021-08-30
Publication date: 2023-10-03
Anticipated expiration: 2041-08-30
Also published as: CN113647474A

Abstract

The invention discloses a preparation method of broom corn millet shell oil microcapsules, relates to the technical field of agricultural product deep processing, and comprises four steps of wall material solution preparation, core material solution preparation, emulsion preparation and spray drying. The broom corn millet shell oil microcapsule prepared by the preparation method of the broom corn millet shell oil microcapsule has an embedding rate of 91.89 percent. Meanwhile, the prepared broom corn millet shell oil microcapsule has good physical and chemical indexes, the moisture content is 2.55 percent, and the bulk density is 0.38g/cm ³ The angle of repose was 38.63 °, the whiteness was 81.63%, the particle size distribution was uniform and concentrated, and the volume average particle size was 0.892 μm. Lays a certain foundation for the research of the storage stability of the follow-up broom corn millet shell oil microcapsule, the digestion and absorption characteristics of the human gastrointestinal tract, the specific application of the follow-up broom corn millet shell oil microcapsule in the food field and the like.

Description

Preparation method of broom corn millet shell oil microcapsule

Technical field:

the invention relates to the technical field of agricultural product deep processing, in particular to a preparation method of broom corn millet shell oil microcapsules.

The background technology is as follows:

broom corn millet (Panicum miliaceum l.) belongs to the genus broomcorn of the family poaceae, and is called millet after kernel peeling, and is widely distributed in asia, europe and other developing countries. Broom corn millet is taken as an important grain source, people usually eat the broom corn millet, and broom corn millet shells are not fully utilized and are often discarded. The broom corn millet shell oil is oil extracted from broom corn millet shell, contains 5 fatty acids of linoleic acid, oleic acid, palmitic acid, linolenic acid and arachidonic acid, and has unsaturated fatty acid content of 91.21%. The unsaturated fatty acid can effectively reduce the risk of cardiovascular diseases, and has the effects of reducing blood lipid, treating xerophthalmia, preventing cancer, etc. However, unsaturated fatty acids in the broom corn millet shell oil are easy to be subjected to rancidity and deterioration due to interference of external factors such as light, oxygen and the like, so that the quality and the nutritional value of the broom corn millet shell oil are reduced. The microcapsule technology is adopted to embed the grease, so that not only can the nutrition and functional components of the grease be protected, but also the oxidation resistance, water solubility and shelf life of the grease can be improved.

Microencapsulation is a process in which tiny droplets or particles are encapsulated by a thin film of polymer and do not harm the chemical nature of the core material. The microcapsules produced are typically between nano-and micro-sized. The microcapsule can protect sensitive core materials, control the release efficiency of the core materials, cover unpleasant smell of the core materials, facilitate processing and treatment, be used for diluting micro-core materials, convert liquid or gas into solid and the like through the physical barrier between the core materials and the wall materials. This technology has been applied in recent decades by those skilled in the relevant arts to various fields, such as food, biological agents, pharmaceuticals, textiles, cosmetics, agriculture, etc.

At present, the oil microencapsulation treatment in broom corn millet husks is not disclosed and reported in a similar technology. Meanwhile, the prior art for reference is not seen for the embedding effect of broom corn millet shell grease. The existing oil microcapsule is low in embedding rate and poor in structural integrity, and meanwhile, the oil microcapsule is poor in thermal stability, digestion property, storage stability and the like, so that deep research on broom corn millet shell microcapsule products is needed, and positive influence is brought to the processing, transportation and storage industries of broom corn millet shell oil microcapsule products.

The invention comprises the following steps:

the invention aims to overcome the defects in the prior art and provides a preparation method of broom corn millet shell oil microcapsules.

The invention relates to a preparation method of broom corn millet shell oil microcapsules, which comprises the following specific operation methods:

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 40-60 ℃ according to a certain proportion, placing the mixture in an ultrasonic cleaner, and carrying out ultrasonic treatment at 40-60 ℃ for 20-40 min, and stirring at constant temperature for 20-40 min by a magnetic heating stirrer to fully dissolve the wall material to obtain a wall material solution;

b. preparing a core material solution: adding a compound emulsifier into broom corn millet shell oil, and stirring for 5-15 min at 40-60 ℃ to obtain a core material solution; the addition amount of the compound emulsifier is 1.5-2.0%, the wall-core ratio is 1-5:1, and the solid mass fraction is 20-25%;

c. emulsion preparation: slowly adding the core material solution obtained in the step b into the wall material solution obtained in the step a, stirring at the constant temperature of 40-60 ℃ for 20-40 min, and homogenizing for 10-30 min under the condition of 30-50 MPa of homogenizing pressure to obtain emulsion;

d. spray drying: and c, spray-drying the emulsion obtained in the step c under the conditions of 130-170 ℃ of air inlet temperature, 70-80 ℃ of air outlet temperature, 40-60 ℃ of feeding temperature and 10.0-12.0 mL/min of feeding speed, thus obtaining the broom corn millet shell oil microcapsule.

As a further improvement of the invention, the specific operation method is as follows:

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 50 ℃ according to a certain proportion, placing the solution in an ultrasonic cleaner, carrying out ultrasonic treatment at 50 ℃ for 20min, and stirring the solution at constant temperature for 30min by a magnetic heating stirrer to fully dissolve the wall material to obtain a wall material solution;

b. preparing a core material solution: adding a compound emulsifier into broom corn millet shell oil, and stirring for 10min at 50 ℃ to obtain a core material solution; the addition amount of the compound emulsifier is 1.8%, the wall-core ratio is 3:1, and the solid mass fraction is 22%;

c. emulsion preparation: slowly adding the core material solution obtained in the step b into the wall material solution obtained in the step a, stirring for 30min at the constant temperature of 50 ℃, and homogenizing for 20min under the condition of the homogenizing pressure of 40MPa to obtain emulsion;

d. spray drying: and c, spray-drying the emulsion obtained in the step c under the conditions of 150 ℃ of air inlet temperature, 75 ℃ of air outlet temperature, 50 ℃ of feeding temperature and 11.3mL/min of feeding speed, thus obtaining the millet shell oil microcapsule.

As a further development of the invention, the composite wall material of step a is a mixture of whey protein isolate WPI and maltodextrin MD.

As a further improvement of the invention, the mixing ratio of the whey protein isolate WPI to the maltodextrin MD is 1-3:1.

As a further improvement of the invention, the MD/WPI is 1.2:1.

As a further improvement of the invention, the compound emulsifier is a mixture of span 60 and tween 60.

As a further improvement of the invention, the proportion of span 60 to tween 60 is as follows: span 60/Tween 60 is 2-5:7.

As a further improvement of the invention, span 60/Tween 60 is 3:7.

The broom corn millet shell oil is prepared in a laboratory, and the specific method refers to broom corn millet shell oil ultrasonic auxiliary extraction process optimization and fatty acid composition analysis published in food and machinery, 5 months in 2020, miao Xinyue and the like; the spray dryer is ADL311-A type spray dryer of YAMATO Co., ltd; the heat collecting stirrer is a DF-1 heat collecting stirrer of a factory of a gold jar hong Sheng instrument; KH-500DE type ultrasonic cleaner; the high-pressure homogenizer was a GEA type high-pressure homogenizer manufactured by Niro soavi company, italy.

The broom corn millet shell oil microcapsule prepared by the preparation method of the broom corn millet shell oil microcapsule has complete particle morphology and embedding rate of 91.89 percent. Meanwhile, the prepared broom corn millet shell oil microcapsule has good physical and chemical indexes, the moisture content is 2.55 percent, and the bulk density is 0.38g/cm ³ The angle of repose was 38.63 °, the whiteness was 81.63%, the particle size distribution was uniform and concentrated, and the volume average particle size was 0.892 μm. Meanwhile, the heat stability of the material is good under a high-temperature environment, and the material has a longer shelf life under a normal-temperature condition.

Description of the drawings:

FIG. 1 is a graph showing the effect of emulsifier addition on emulsion stability and microcapsule entrapment;

FIG. 2 is a graph showing the effect of wall-core ratio on emulsion stability and microcapsule entrapment rate;

FIG. 3 is the effect of wall material comparison on emulsion stability and microcapsule entrapment rate;

FIG. 4 is a graph showing the effect of solids fraction on emulsion stability and microcapsule entrapment rate;

FIG. 5 is a response surface plot and contour plot of the effect of emulsifier addition and wall material formulation on embedding rate;

FIG. 6 is a response surface plot and contour plot of the effect of emulsifier addition and solids fraction on entrapment;

FIG. 7 is a graph showing the effect of inlet air temperature on microcapsule entrapment rate;

FIG. 8 is a graph showing the effect of homogenization time on microcapsule entrapment rate;

FIG. 9 is a graph showing the effect of feed temperature on microcapsule entrapment rate;

FIG. 10 is a graph showing the effect of feed rate on microcapsule entrapment rate;

FIG. 11 is a response surface plot and contour plot of the effect of each factor interaction on the entrapment rate;

fig. 12 is a scanning electron microscope image of broom corn millet shell oil microcapsule particles;

FIG. 13 is a particle size distribution of broom corn millet husk oil microcapsules;

FIG. 14 shows POV value change of broom corn millet husk oil and broom corn millet husk oil microcapsules at different temperatures;

FIG. 15 is a zero-order linear regression analysis of the POV value trend of broom corn millet husk oil microcapsules at different temperatures;

FIG. 16 is a first-order linear regression analysis of the POV value trend of broom corn millet husk oil microcapsules at different temperatures;

FIG. 17 is a lnkB-1/T linear fit of POV;

fig. 18 is a TG profile of broom corn millet husk oil microcapsules;

FIG. 19 is a DSC of a broom corn millet husk oil microcapsule;

fig. 20 is an infrared spectrum of broom corn millet hull oil microcapsule and its constituent components (broom corn millet hull oil microcapsule, broom corn millet hull oil, maltodextrin, whey protein isolate are shown in the order from top to bottom in the figure).

The specific embodiment is as follows:

example 1

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 40 ℃ according to a certain proportion, placing the solution in an ultrasonic cleaner, performing ultrasonic treatment at 40 ℃ for 20min, and performing constant-temperature stirring for 20min by a magnetic heating stirrer to fully dissolve the wall material to obtain a wall material solution; the composite wall material is a mixture of whey protein isolate WPI and maltodextrin MD, and the mixing ratio of the whey protein isolate WPI to the maltodextrin MD is 1:1;

b. preparing a core material solution: adding a compound emulsifier into broom corn millet shell oil, and stirring for 5minn at 40 ℃ to prepare a core material solution; the addition amount of the compound emulsifier is 1.5%, the wall-core ratio is 1:1, and the solid mass fraction is 20%; the compound emulsifier is a mixture of span 60 and tween 60, and the proportion of span 60 to tween 60 is as follows: span 60/tween 60 is 2:7;

c. emulsion preparation: slowly adding the core material solution obtained in the step b into the wall material solution obtained in the step a, stirring for 20min at the constant temperature of 40 ℃, and homogenizing for 10min under the condition of 30MPa of homogenizing pressure to obtain emulsion;

spray drying: and c, spray-drying the emulsion obtained in the step c under the conditions of an air inlet temperature of 130 ℃, an air outlet temperature of 70 ℃, a feeding temperature of 40 ℃ and a feeding speed of 10.0mL/min, thereby obtaining the millet shell oil microcapsule.

Example 2

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 60 ℃ according to a certain proportion, placing the solution in an ultrasonic cleaner, performing ultrasonic treatment at 60 ℃ for 40min, and performing constant-temperature stirring for 40min by a magnetic heating stirrer to fully dissolve the wall material to obtain a wall material solution; the composite wall material is a mixture of whey protein isolate WPI and maltodextrin MD, and the mixing ratio of the whey protein isolate WPI to the maltodextrin MD is 3:1;

b. preparing a core material solution: adding a compound emulsifier into broom corn millet shell oil, and stirring at 60 ℃ for 15min to obtain a core material solution; 2.0% of compound emulsifier, 5:1 of wall-core ratio and 25% of solid mass fraction; the compound emulsifier is a mixture of span 60 and tween 60, and the proportion of span 60 to tween 60 is as follows: span 60/tween 60 is 5:7;

c. emulsion preparation: slowly adding the core material solution obtained in the step b into the wall material solution obtained in the step a, stirring at the constant temperature of 60 ℃ for 40min, and homogenizing for 30min under the condition of the homogenizing pressure of 50MPa to obtain emulsion;

spray drying: and c, spray-drying the emulsion obtained in the step c under the conditions of 170 ℃ of air inlet temperature, 80 ℃ of air outlet temperature, 60 ℃ of feeding temperature and 12.0mL/min of feeding speed, thus obtaining the millet shell oil microcapsule.

Example 3

A preparation method of broom corn millet shell oil microcapsule comprises the following specific operation method:

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 50 ℃ according to a certain proportion, placing the solution in an ultrasonic cleaner, carrying out ultrasonic treatment at 50 ℃ for 20min, and stirring the solution at constant temperature for 30min by a magnetic heating stirrer to fully dissolve the wall material to obtain a wall material solution; the composite wall material is a mixture of whey protein isolate WPI and maltodextrin MD, and the mixing proportion of the whey protein isolate WPI and the maltodextrin MD is as follows: MD/WPI is 1.2:1;

b. preparing a core material solution: adding a compound emulsifier into broom corn millet shell oil, and stirring for 10min at 50 ℃ to obtain a core material solution; the addition amount of the compound emulsifier is 1.8%, the wall-core ratio is 3:1, and the solid mass fraction is 22%; the compound emulsifier is a mixture of span 60 and tween 60, and the proportion of span 60 to tween 60 is as follows: span 60/tween 60 is 3:7;

spray drying: and c, spray-drying the emulsion obtained in the step c under the conditions of 150 ℃ of air inlet temperature, 75 ℃ of air outlet temperature, 50 ℃ of feeding temperature and 11.3mL/min of feeding speed, thus obtaining the millet shell oil microcapsule.

The physicochemical and functional tests of the broom corn millet husk oil microcapsules prepared by the method described in example 3 were carried out as follows:

1. the measurement method is as follows:

1. emulsion stability determination method

The centrifugal speed is 8000r/min and the centrifugal speed is 10min. A certain amount of emulsion is filled into a centrifuge tube with scales, centrifuged, and the free water layer volume is read to calculate the stability of the emulsion system. Emulsion stability is calculated according to formula (1).

2. Determination of broom corn millet shell oil microcapsule embedding rate

(1) Microcapsule surface oil determination method

With reference to the method of Zhang Min and with minor modifications, the supernatant was obtained by centrifugation, and the filtrate was evaporated with a rotary evaporator to obtain broom corn millet hull oil. Weigh 2.000g (m) ₀ ) The prepared broom corn millet husk oil microcapsule is placed in a 50mL test tube with a plug, 30mL petroleum ether (boiling range is 30-60 ℃) is added, vortex oscillation is carried out for 2min, centrifugation is carried out for 20min under the condition of 5000r/min, supernatant fluid is taken, 15mL petroleum ether is added for cleaning bottom residues, centrifugation is carried out, supernatant fluid is collected, and the operation is repeated. The combined supernatants were placed in rotavapor bottles (m) ₁ ) Rotary evaporation is performed. Then transferred to a drying oven at 105+/-1 ℃ to be dried to constant weight (m ₂ )。

Each sample was subjected to 3 replicates. The oil content of the microcapsule surface is calculated according to formula (2).

(2) Method for measuring total oil and embedding rate of microcapsule

Weigh 2g (to 0.001, m ₀ ) Placing broom corn millet shell oil microcapsule in a beaker, adding 60deg.C hot water 10mL, stirring to dissolve sample completely, adding 1.25mL ammonia water, mixing, heating in water bath at 60deg.C for 10min, shaking for 2min, adding 10mL absolute ethanol, cooling with cold water, adding 20mL diethyl ether, shaking for 30s, adding 20mL petroleum ether, shaking for 30s, placing in a separating funnel, standing for layering, collecting supernatant, and placing in a rotary evaporation bottle (m ₁ ) Rotary evaporation is performed. Then transferred to a drying oven at 105+/-1 ℃ to be dried to constant weight (m ₂ ). Each sample was subjected to 3 replicates. The total oil content of the microcapsules and the embedding rate are calculated according to formulas (3) and (4).

3. Single factor experiment for preparing broom corn millet shell oil microcapsule emulsion formula

(1) Influence of the amount of emulsifier added on emulsion stability and entrapment

Under the conditions that the wall-core ratio is 3:1 and the MD/WPI is 2:1, and the solid mass fraction is 20%, the influence on the emulsion stability of broom corn millet shell oil and the embedding rate of broom corn millet shell oil microcapsules is examined when the addition amount of the emulsifier is 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% respectively.

(2) Influence of wall-core ratio on emulsion stability and entrapment Rate

Under the condition that the MD/WPI is 2:1 and the solid mass fraction is 20% and the addition amount of the emulsifier is 2.0%, the influence on the emulsion stability of broom corn millet shell oil and the embedding rate of broom corn millet shell oil microcapsules is examined when the wall core ratio is 1:2, 1:1, 2:1, 3:1 and 4:1 respectively.

(3) Influence of MD/WPI on emulsion stability and entrapment Rate

Under the condition that the wall-core ratio is 3:1, the addition amount of the emulsifier is 2.0 percent and the solid matter mass fraction is 20 percent, the influence on the emulsion stability of broom corn millet shell oil and the embedding rate of broom corn millet shell oil microcapsules is examined when the MD/WPI is 1:1, 2:1, 3:1, 4:1 and 5:1 respectively.

(4) Influence of the solids mass fraction on emulsion stability and entrapment

When the wall-core ratio is 3:1, the addition amount of the emulsifier is 2.0%, the MD/WPI is 2:1, and the mass fractions of solid matters are 5%, 10%, 15%, 20% and 25%, respectively, the influence on the stability of the broom corn millet shell oil emulsion and the embedding rate of the broom corn millet shell oil microcapsule is examined.

4. Response surface optimization test for preparing broom corn millet shell oil microcapsule emulsion

On the basis of a single-factor experiment, 4 factors such as the addition amount of an emulsifier A, the wall-core ratio B, the mass fraction of a C MD/WPI and a D solid substance are selected, the embedding rate of the broom corn millet shell oil microcapsule is taken as a response value, and a Box-Behnken design is adopted to carry out an optimization experiment on the preparation process of the broom corn millet shell oil microcapsule emulsion, wherein the factor level is shown in Table 1.

TABLE 1 response surface test factor level encoding table

5. Single factor test of broom corn millet shell oil microcapsule spray drying process

Based on the response surface optimization test of the preparation of the 4-broom corn millet shell oil microcapsule emulsion, the following test is carried out under the homogenizing pressure of 40Mpa according to the optimal process conditions of the addition amount of the emulsifier, the wall core ratio, the MD/WPI and the solid mass fraction.

(1) Influence of air inlet temperature on embedding rate of broom corn millet shell oil microcapsule

And under the conditions of homogenizing time of 20min, feeding temperature of 50 ℃ and feeding speed of 11.3mL/min, the influence of air inlet temperatures of 120, 130, 140, 150 and 160 ℃ on the embedding rate of the millet shell oil microcapsule is examined.

(2) Influence of homogenization time on the embedding rate of broom corn millet hull oil microcapsules

Under the conditions of 150 ℃ of air inlet temperature, 50 ℃ of feeding temperature and 11.3mL/min of feeding speed, the influence of homogenizing time of 10, 15, 20, 25 and 30min on the embedding rate of the millet shell oil microcapsule is examined.

(3) Influence of the feeding temperature on the coating rate of broom corn millet shell oil microcapsules

And under the conditions of air inlet temperature of 10 ℃, homogenizing time of 20min and feeding speed of 11.3mL/min, the influence of feeding temperatures of 40, 45, 50, 55 and 60 ℃ on the embedding rate of the millet shell oil microcapsule is examined.

(5) Influence of the feed rate on the coating rate of broom corn millet husk oil microcapsules

Under the conditions of 150 ℃ of air inlet temperature, 50 ℃ of feeding temperature and 20min of homogenizing time, the influence of feeding speeds of 5.2, 8.2, 11.3, 14.4 and 17.7mL/min on the embedding rate of the broom corn millet shell oil microcapsule is examined.

6. Response surface optimization test of broom corn millet shell oil microcapsule spray drying process

On the basis of a single factor experiment, 4 factors of an air inlet temperature A, a homogenizing time B, a feeding temperature C and a feeding speed D are selected as investigation objects, the embedding rate of the broom corn millet shell oil microcapsule is taken as a response value, and a Box-Behnken design is adopted to carry out an optimization test on the spray drying process parameters of the broom corn millet shell oil microcapsule. The factor levels are shown in Table 2.

TABLE 2 response surface test factor level encoding tables

7. Surface morphology observation of broom corn millet shell oil microcapsules

The surface morphology of the broom corn millet shell oil microcapsule is observed by a Scanning Electron Microscope (SEM). And scattering the broom corn millet shell oil microcapsule on a sample table stuck with double faced adhesive tape, blowing off excessive powder, then performing metal spraying treatment on the sample, and observing the microstructure of the broom corn millet shell oil microcapsule by using SEM in a short time under the acceleration voltage of 5.0 KV.

8. Determination of essential physicochemical index of broom corn millet shell oil microcapsule

(1) Determination of the moisture content of microcapsules

With sample trays (mass m) ₀ ) Accurately weighing 2.000g of broom corn millet husk oil microcapsule sample (total weight of sample and sample tray is m ₁ ) Drying in a 105 deg.C oven for 3 hr, cooling in a dryer, weighing, drying microcapsule sample in the oven again for 1 hr, cooling, weighing, repeating the operation until the mass difference between the last two samples is less than 0.001g, recording the mass (m ₂ ) The moisture content is calculated according to formula (5).

(2) Determination of microcapsule bulk Density

Accurately weighing broom corn millet shell oil microcapsules with the mass of 3.000g by an electronic analytical balance, slowly and uniformly loading the broom corn millet shell oil microcapsules into a graduated plugged measuring cylinder through a funnel, horizontally shaking the measuring cylinder on a test bed for 30 times to enable the broom corn millet shell oil microcapsules to naturally sink, reading the volume after the stacking surface of a sample is horizontal, and calculating the mass of a unit volume of the sample to obtain the stacking density of the broom corn millet shell oil microcapsules. Each sample was assayed in 3 replicates.

(3) Measurement of microcapsule flowability

Accurately weighing 10g of broom corn millet husk oil microcapsule samples in a funnel, enabling the samples to naturally fall onto a horizontal circular plate through the funnel, stacking the samples to a certain height, measuring the height H of a powder pile and the coverage radius R of the powder pile at the moment, and calculating the repose angle theta according to a formula (6).

θ＝arctan(H/R) (6)

(4) Measurement of whiteness of microcapsules

And pouring the prepared microcapsule sample into a plate, tiling to a certain thickness, correcting by a color colorimeter, measuring the L, a, b color values of the microcapsule sample, and calculating the whiteness according to a formula (7).

Wherein L represents luminance, a represents red-green, and b represents yellow-blue.

9. Determination of microcapsule particle size distribution

Taking a small amount of microcapsules, adding a certain amount of distilled water, stirring to fully dissolve the microcapsules, measuring the particle size distribution of the microcapsules by using a laser particle size analyzer, and drawing a particle size distribution curve graph.

10. Data processing

Response surface test Design and analysis were performed using Design-Expert 8.0.6, data were statistically analyzed and plotted using SPSS 25.0 and Origin 8.5 software, each set of tests was repeated 3 times, and experimental data were expressed as mean.+ -. Standard deviation.

11. Storage and shelf life tests

Placing broom corn millet shell oil and broom corn millet shell oil microcapsules in an incubator at 25 ℃,35 ℃ and 45 ℃ respectively, standing for 2 months, measuring POV values of broom corn millet shell oil and broom corn millet shell oil microcapsules every 5-7d, exploring storage stability of broom corn millet shell oil and broom corn millet shell oil microcapsules under different temperature conditions, fitting an oxidation dynamics equation of the POV values of the broom corn millet shell oil microcapsules and predicting shelf life of the broom corn millet shell oil microcapsules.

12. Thermogravimetric (TG) analysis

And accurately weighing a certain amount of broom corn millet shell oil microcapsules, and analyzing the thermal weight of the product by a thermal weight analyzer. The heating rate is controlled to be 10 ℃/min, the nitrogen flow rate is controlled to be 30mL/min, and the scanning temperature range is 0-650 ℃.

13. DSC (differential scanning calorimeter) analysis

Accurately weighing a certain amount of broom corn millet shell oil microcapsule samples in an aluminum box, sealing by a press, and then placing the samples in DSC for measurement. The DSC heating range is-20-250 ℃, the heating rate is 10 ℃/min, and the nitrogen flow rate is 20mL/min.

2. Results and analysis

1. Single factor test for preparing broom corn millet shell oil microcapsule emulsion formula

(1) Influence of the amount of emulsifier added on emulsion stability and microcapsule entrapment

As can be seen from FIG. 1, the amount of the emulsifier added was in the range of 0.5 to 1.5%, and the emulsion stability increased rapidly, while the amount of the emulsifier added was further increased, and the emulsion stability did not increase greatly. The emulsifier is completely adhered to the surface of emulsified broom corn millet shell oil particles, so that the oil-water interfacial tension is reduced, the emulsion stability is rapidly improved, and the embedding rate of the microcapsule reaches the maximum value and is 86.94%. The amount of the emulsifier is continuously increased, the redundant emulsifier exists in the solution in the form of a micelle, the interfacial tension of oil water is not continuously reduced, and the stability change is slow, which is consistent with the result of Dickinson and the like, namely when a proper amount of the emulsifier is wrapped on the surface of the liquid drop, the size of the liquid drop is possibly increased due to the increment of the redundant emulsifier, and the coalescence is further generated. Too much emulsifier can increase the viscosity of the emulsion, which is unfavorable for the combination of the core material and the wall material, and reduces the embedding rate. Therefore, the optimum amount of the emulsifier to be added was 1.5%.

(2) Influence of wall-core ratio on emulsion stability and microcapsule entrapment

As can be seen from fig. 2, the emulsion stability tends to increase with increasing wall-core ratio, and the embedding rate increases and then decreases. When the wall-core ratio is 3:1, the embedding rate is 86.67% at the highest, because the wall material content is properly increased, the thickness of the microcapsule wall is increased, and the release of the core material can be effectively inhibited. When the wall material consumption is continuously increased, the emulsion stability is not greatly changed, and the core material and the water in the wall material are difficult to volatilize in the spray drying process to form a wall cavity due to the fact that the wall is too thick, so that the loss of the core material is caused, and the embedding rate is reduced. The optimum wall to core ratio was chosen to be 3:1.

(3) Influence of MD/WPI on emulsion stability and microcapsule entrapment Rate

As can be seen from FIG. 3, the emulsion stability and the embedding rate of the MD/WPI reach the highest values at the ratio of 2:1, because the WPI has good film forming property and emulsifying property, and the broom corn millet shell oil is better wrapped by the WPI with higher content. When the MD/WPI is in the range of 2:1-3:1, the emulsion stability and the microcapsule embedding rate are both reduced, because the emulsification capacity of the emulsion is reduced due to the reduction of the WPI content, the emulsion stability is weakened, so that the film forming property of the broom corn millet shell oil microcapsule emulsion in the spray drying process is reduced, and the embedding rate of the broom corn millet shell oil microcapsule is reduced. Therefore, the optimum composite wall material ratio (MD/WPI) was chosen to be 2:1.

(4) Influence of the solids mass fraction on emulsion stability and entrapment

The mass fraction of the solid matters is in the range of 5-20%, the emulsion stability and the microcapsule embedding rate are obviously improved, the stability is enhanced mainly because the concentration of the solid matters is increased, the viscosity of the solution is increased, and the Brownian movement of the molecules is slowed down, so that the stability is enhanced; the amount of solid matter is increased, the water required to evaporate in the spray drying process is reduced, the capsule wall is formed faster, the thickness is increased, and the embedding rate is gradually increased. And when the solid matter weight fraction continues to increase, the emulsion stability changes slowly, and the solution viscosity increases, so that the liquid drops are unevenly atomized, the atomization effect is weakened, and the embedding rate is reduced. Xiong Yueqin it is also pointed out that when the solids concentration is too high, the atomization rate during spray drying is reduced, the material dead time is prolonged, the loss of low boiling substances is increased, and the entrapment rate is reduced. Therefore, the optimum solid mass fraction was selected to be 20%.

2. Response surface optimization test for preparing broom corn millet shell oil microcapsule emulsion formula

(1) Box-Behnken experimental design and results

According to a single-factor experimental result, selecting the embedding rate of the broom corn millet shell oil microcapsule as a response value, and adopting a Box-Behnken experimental design to perform a response surface optimization experiment on the broom corn millet shell oil microcapsule emulsion preparation process. And selecting the addition amount of the emulsifier A, the wall-core ratio B and the mass fraction of the CMD/WPI and the solid matter D as investigation factors. Box-Behnken test designs and results are shown in Table 3.

TABLE 3Box-Behnken test design and results

And carrying out regression fitting on the response surface test result according to Design-Expert 8.0.6 data analysis software to obtain a regression fitting equation:

Y＝86.71+2.48A+1.72B-4.29C+1.63D-0.17AB-2.38AC+3.12AD-0.80BC-0.80BD-0.29CD-4.53A ² -4.95B ² -3.61C ² -4.41D ²

(2) Response surface experimental analysis of variance

As can be seen from Table 4, the regression model was very significant (P<0.01 A) the mismatch term p= 0.0754>0.05 was not significant. Regression coefficient R ² 0.9738, it shows that the model correlation is good, that is, the predicted value and the actual value of the regression model can be well matched. A, B, C, D, A in the model ² 、B ² 、C ² 、D ² The effects of AC and AD are extremely remarkable (P < 0.01); BC. BD, CD, AB effects were insignificant (P>0.05). The size and sequence of the influence of the embedding rate of the broom corn millet shell oil microcapsule are as follows: wall material ratio > emulsifier addition amount > wall core ratio > solid mass fraction.

TABLE 4 regression model analysis of variance

Note that: * P <0.05, significant differences; * P <0.01, the difference is very significant.

The response surface diagram and the contour diagram of the embedding rate of the broom corn millet hull oil microcapsule are interactively influenced by different factors, as shown in fig. 5 and 6. As can be seen from fig. 5, the embedding rate of the broom corn millet husk oil microcapsule increases and decreases with the increase of the emulsifier addition amount and the increase of the MD/WPI ratio, the slope of the curved surface graph is steep, and the contour graph is elliptical, which indicates that the interaction between the emulsifier addition amount and the MD/WPI compounding ratio is remarkable. As can be seen from fig. 6, when the amount of the emulsifier added is fixed, the embedding rate of the broom corn millet shell oil microcapsule increases and then decreases with the increase of the solid matter mass fraction; when the mass fraction of the solid matters is fixed, the embedding rate of the broom corn millet shell oil microcapsule also shows a tendency of rising and then reducing along with the increase of the addition amount of the emulsifier, and the contour line is elliptical, so that the interaction effect of the two factors is obvious.

(3) Verification test for process optimization of broom corn millet shell oil microcapsule emulsion

After analysis by Design-Expert 8.0.6 software, the optimal parameter conditions for obtaining the broom corn millet shell oil microcapsule emulsion are as follows: the addition amount of the emulsifier is 1.82%, the wall-core ratio is 3.2:1, the MD/WPI is 1.16:1, and the solid mass fraction is 22.10%. The theoretical value of the embedding rate of the millet shell oil microcapsule under the condition is 89.81 percent. Considering the convenience of actual operation, the process for preparing the millet shell oil microcapsule emulsion is determined as follows: the addition amount of the emulsifier is 1.8%, the wall-core ratio is 3:1, the MD/WPI is 1.2:1, the solid mass fraction is 22%, under the condition, 3 groups of experiments are repeated for verification, the average embedding rate of the broom corn millet shell oil microcapsule is 90.10%, and the average embedding rate basically accords with the predicted value. Meanwhile, the embedding rate of the broom corn millet shell oil microcapsule under the condition is higher than the maximum embedding rate 87.40% of the response surface test in table 3, which shows that the model is correct and can be suitable for optimizing the broom corn millet shell oil microcapsule emulsion process.

3. Single factor test of broom corn millet shell oil microcapsule spray drying process

(1) Influence of air inlet temperature on microcapsule embedding rate

As can be seen from fig. 7, when the inlet air temperature is in the range of 120-150 ℃, the embedding rate of the broom corn millet shell oil microcapsule is obviously increased and reaches a maximum value of 90.26%; the air inlet temperature is continuously increased, and the embedding rate is obviously reduced. The microcapsule embedding rate is improved because the capsule wall is formed faster and the core material is not easy to lose along with the increase of the air inlet temperature; however, when the air inlet temperature is too high, the water dissipation speed is too high, the microcapsule structure becomes loose, the core material is not protected, and the embedding rate is reduced. Wang Hongye it is pointed out that the increase of the inlet air temperature breaks the balance between the evaporation rate of water on the surface of the liquid drop and film formation, so that cracks are generated on the surface of the microcapsule powder, and grease seeps out. Therefore, the optimum inlet air temperature was selected to be 150 ℃.

(2) Effect of homogenization time on microcapsule encapsulation Rate

As shown in fig. 8, when the homogenization time is within the range of 10-15min, the encapsulation efficiency of the broom corn millet husk oil microcapsule increases and reaches the maximum value of 91.11%, which is probably because the emulsion stability reaches the optimal state when the homogenization time is 15min, and when the homogenization time is continuously increased, the encapsulation efficiency of the microcapsule tends to decrease because the original stable system of the emulsion is damaged due to the excessive homogenization time, and the encapsulation efficiency decreases. Therefore, the optimal homogenization time was chosen to be 15min.

(3) Influence of the feed temperature on the encapsulation efficiency of the microcapsules

As can be seen from fig. 9, the microcapsule embedding rate increases and then decreases with increasing feed temperature. The microcapsule embedding rate is highest at the feeding temperature of 50 ℃, and is 89.77%. As the feed temperature continues to rise, the microcapsule entrapment rate drops significantly, probably because the feed temperature is too high and the microcapsules are susceptible to thermal gelatinization at high temperature conditions, resulting in a drop in entrapment rate. Thus, the optimum feed temperature was chosen to be 50 ℃.

(4) Influence of the feed rate on the encapsulation efficiency of microcapsules

As can be seen from fig. 10, when the feeding rate is in the range of 5.2-11.3mL/min, the microcapsule embedding rate is significantly increased, but the feeding rate is further increased, and the microcapsule embedding rate is significantly decreased, because when the feeding rate is too high, the material evaporation time is insufficient, the complete capsule wall cannot be formed, the product particles are larger, and the embedding rate is decreased. Furthermore, liu Chengxiang also points out in studying the effect of feed rate on peony seed oil microcapsules: when the feeding speed is too low, the energy consumption is too large, the efficiency is low, and the method is allowed in actual industrial production; and too high a feed rate can also lead to a phenomenon in which the outlet temperature of the spray drying is low or unstable. Thus, the optimal feed rate was selected to be 11.3mL/min.

4. Response surface optimization test of broom corn millet shell oil microcapsule spray drying process

According to a single-factor experimental result, selecting the embedding rate of the broom corn millet shell oil microcapsule as a response value, and adopting a Box-Behnken experimental design to carry out a response surface optimization test on the spray drying process parameters of the broom corn millet shell oil microcapsule. And selecting the air inlet temperature A, the homogenizing time B, the feeding temperature C and the feeding speed D as investigation factors. Box-Behnken test designs and results are shown in Table 5, and regression model analysis of variance is shown in Table 6.

TABLE 5 Box-Behnken test design and results

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TABLE 6 regression model analysis of variance

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Y＝90.69-0.95A-0.25B+0.86C-0.099D-0.64AB-0.22AC+0.80AD+1.95BC+1.89BD+2.53CD-5.73A ² -1.49B ² -1.60C ² -2.58D ² (6)

as can be seen from table 6, the regression model was extremely significant (P<0.01 A) the mismatch term p= 0.1814>0.05 was not significant. Regression coefficient R ² 0.9764, it shows that the model correlation is good, that is, the predicted value and the actual value of the regression model can be well matched. The primary term A, C in the model affects very significantly (P < 0.01), and affects factor A>C, performing operation; the interaction terms BC, BD and CD have extremely remarkable influence (P < 0.01), and the AD has remarkable influence (P < 0.05); quadratic term A ² 、B ² 、C ² 、D ² The effect is extremely remarkable (P < 0.01). The response surface and contour plot of the effect of each factor interaction on the entrapment rate is shown in figure 11.

5. Response surface optimization verification test of broom corn millet shell oil microcapsule spray drying process

After analysis by Design-Expert 8.0.6 software, the best technological conditions for preparing broom corn millet shell oil microcapsules by a spray drying method are as follows: inlet air temperature 148.98 ℃, homogenizing time 20min, feeding temperature 55 ℃, feeding speed 13.84mL/min, and embedding rate theoretical value as follows: 92.01%. The process parameters optimized by the model are properly adjusted to be as follows in combination with the actual situation: the average embedding rate of the broom corn millet shell oil microcapsule obtained through experiments under the condition is 91.89 percent and is close to a predicted value.

6. Surface morphology observation of broom corn millet shell oil microcapsules

Fig. 12 is an external structure diagram of the broom corn millet shell oil microcapsule with 3200 times magnification, and it can be seen that the surface of the broom corn millet shell oil microcapsule particle is smoother and continuous, and has no cracks. The surface of a few particles has depressions or irregular shapes, which may be the instantaneous evaporation of water during the solidification of the wall material during spray drying, so that the evaporation of water inside the microcapsules forms a pressure difference with the external air flow, and depressions are formed in the portions with smaller thickness and hardness. In addition, in the metal spraying treatment process of the scanning electron microscope, the phenomenon is aggravated by excessively high vacuum pumping. The surface of the prepared broom corn millet shell oil microcapsule is smoother and has good encapsulation performance. The broom corn millet shell oil can be effectively protected and prevented from being oxidized, so that the storage stability of the broom corn millet shell oil can be improved.

7. Physicochemical index of broom corn millet shell oil microcapsule

The moisture content, bulk density, angle of repose, whiteness, etc. of the microcapsules can affect the final quality of the microcapsule product and its characteristics during storage. When the moisture content of the microcapsule is lower than 5%, the adverse microorganism activity in the environment is inhibited, and the storability of the product is improved; when the water content is high, the phenomena of mildew, caking and the like can occur, and the product quality is reduced. The microcapsules have a greater bulk density, indicating a greater amount of storage in a smaller space, reducing the amount of oxygen in the interstices of the particles, and slowing oxidation. The angle of repose is an important indicator for measuring the flowability of a powder product, and the smaller the angle of repose, the better the flowability of the product. In general, the powder has good fluidity when the repose angle is less than or equal to 30 degrees; the fluidity of the product is better when the repose angle is 30-45 degrees; the fluidity of the product is general at an angle of repose of 45-60 degrees; while the repose angle is more than or equal to 60 DEG, the fluidity of the product is poor ^[13] . The whiteness of the microcapsule can be used for measuring the embedding effect of the microcapsule, the whiteness value is higher, the grease can be fully wrapped by wall materials, the surface oil is less, and the higher whiteness value also indicates that the grease is not oxidized due to overhigh temperature in the spray drying process. From Table 7, the content of water in the broom corn millet husk oil microcapsule is 2.55%, which is basically the same as that of other microcapsule powder, so that the water evaporation of the microcapsule is complete in the spray drying process, the product is fully dried, the adverse activities of external microorganisms can be effectively inhibited, and the storage stability of the microcapsule is improved. Bulk density of 0.38g/cm ³ Indicating that the product can slow down oxidation. The repose angle is 38.63 degrees, which indicates that the product has better fluidity and can be used conveniently. The whiteness of the broom corn millet shell oil microcapsule is 81.63%, which shows that the embedding effect of the oil after spray drying is better.

Table 7 physicochemical index of broom corn millet husk oil microcapsule

8. Particle size distribution of broom corn millet shell oil microcapsules

The particle size and distribution of the microcapsules are important parameters of the microcapsule product. The microcapsule with uniform particle size distribution has good dispersibility. From the application point of view, the microcapsule particles are too large, which may cause uncomfortable taste, while the microcapsules with small particle size are easier to be absorbed by human body. Fig. 13 is a particle size distribution diagram of broom corn millet shell oil microcapsules. The equivalent diameters of the largest particles in the distribution curves at 10%, 50% and 90% of the cumulative distribution are D _X (10)＝0.559μm、D _X (50)＝0.843μm、D _X (90) =1.407 μm, indicating that the maximum particle size at which the cumulative distribution reaches 90% is 1.407 μm. As can be seen from fig. 7, the particle size distribution of the broom corn millet husk oil microcapsule exhibits a normal distribution and is relatively narrow, the particle size is mostly concentrated to 0.3 to 3 μm, only one peak occurs in the particle size range, and the volume average particle size thereof is 0.892 μm. Therefore, the particle size distribution of the prepared broom corn millet shell oil microcapsule is uniform and concentrated.

9. Storage test of broom corn millet shell oil microcapsules at different temperatures

(1) Change in POV during storage

As can be seen from fig. 14, the POV of the broom corn millet hull oil and broom corn millet hull microcapsules changed slowly before the storage, and the oxidation rates of the broom corn millet hull oil and broom corn millet hull oil microcapsules increased at 25 ℃ and 45 ℃ with the increase of the storage days. This may be that the deterioration components in the broom corn millet hull oil are less (aldehydes, ketones, alcohols, low molecular fatty acids, etc.) at the initial stage of storage; as the number of days of storage increases, the deterioration component increases, and the peroxide value increases rapidly under the combined action of oxygen and temperature. As can be seen from fig. 14: the broom corn millet shell oil microcapsule has POV value stored at 45 deg.c higher than 25 deg.c and 35 deg.c, and this means that the broom corn millet shell oil microcapsule needs to avoid high temperature environment during storing. In addition, the change of the peroxide value of the broom corn millet shell oil microcapsule stored at 25 ℃ is the slowest, and the change is obviously lower than the POV value of the broom corn millet shell oil at the same temperature, which indicates that the broom corn millet shell oil can be effectively embedded by taking whey protein isolate and maltodextrin as the compound wall material, and the oxidation speed of the broom corn millet shell oil is slowed down.

(2) Oxidation kinetics research and shelf life prediction of broom corn millet shell oil microcapsule POV value

Using the zero-order reaction equation respectively

C＝C ₀ -*kt

And a first order reaction equation

lnC＝lnC ₀ -kt

Linear regression analysis is carried out on POV value change of broom corn millet shell oil and broom corn millet shell oil microcapsules.

Table 8 linear regression analysis of changes in POV values of broom corn millet husk oil microcapsules

As can be seen from table 8, the regression coefficients of the first-order reaction at 25 ℃ and the zero-order reaction are not greatly different, and the regression coefficients of the first-order reaction at 35 ℃ and 45 ℃ are both larger than the regression coefficients of the zero-order reaction, i.e. the fitting degree to the first-order oxidation reaction is higher than that to the zero-order oxidation reaction, so that the oxidation reactions of the broom corn millet shell oil and the broom corn millet shell oil microcapsules belong to the first-order oxidation kinetic reaction (fig. 15 and 16). The broom corn millet shell oil microcapsule is stored at 25, 35 and 45 ℃ and the change constant k of pov with time is 0.0112, 0.0199 and 0.0362 respectively. According to the Arrhenius equation:

lnk＝lnk ₀ -Ea/RT

linear fitting was performed on lnk-1/T, see Table 9 and FIG. 17.

Table 9 fitting constant of the POV values of broom corn millet husk oil microcapsules

The linear expression of the Arrhenius equation from fig. 17 is lnk= -5560/t+14.149, r ² ＝0.9981，-Ea/R＝-5560，lnk ₀ = 14.149, the calculated activation energy ea=46.00 KJ/mol=46000J/mol, k ₀ = 1395830.POV initial value is 2.61mmol/kg, the national limit value of common vegetable oil is regulated (peroxide value is less than or equal to 10.0m mol/kg), and according to the shelf life prediction model of POV:

shelf life was predicted to be 110d at 25 ℃,60 d at 35 ℃ and 34d at 45 ℃.

10. Thermogravimetric analysis (TG) of broom corn millet husk oil microcapsules

FIG. 18 is a graph of TG curve of broom corn millet husk oil microcapsule with about 2.2% loss at 35-100deg.C, combined with DSC curve (FIG. 19), where broom corn millet husk oil microcapsule begins to dissolve endothermically, the mass lost by the microcapsule is mainly free water in the microcapsule sample, the curve shows a small decrease trend due to lower moisture content; when the temperature is in the range of 100-160 ℃, the curve tends to be flat and almost no weight loss occurs. The microcapsule starts to degrade rapidly at 160 ℃ until the degradation is basically completed at 410 ℃, the mass loss is excessive at this stage, about 80%, and the slope of the curve is larger, which indicates that the microcapsule structure is seriously damaged, the chemical bond is broken, maltodextrin is gelatinized, and meanwhile, the whey protein isolate is thermally denatured. When the temperature reaches 500 ℃, the weight loss curve becomes flatter, which indicates that the decomposition process is basically finished, and the overall weight loss of the sample is approximately 84%. According to the graph of fig. 18, when the microcapsules begin to decompose after 160 ℃, it is shown that the microcapsule product can maintain good thermal stability in an environment below 160 ℃, i.e. can be stable during normal production and processing.

11. DSC graph of broom corn millet shell oil microcapsule

As shown in FIG. 19, the broom corn millet husk oil microcapsules begin to dissolve endothermically at 61.05℃and peak at 117.97 ℃and the microcapsule glass transition temperature is 117.97 ℃because the first endothermically peak temperature occurring during heating of the material is known as the glass transition temperature (Tg). The reaction at this stage is that the microcapsule wall material component swells under high temperature, the ordered crystal is converted into disordered crystal structure, and the endothermic phenomenon occurs. When the temperature was raised to 200 ℃, the 2 nd absorption peak appeared, the peak was 216 ℃, and in combination with thermogravimetric analysis curve (fig. 18), the microcapsule began to degrade rapidly at 160-410 ℃, indicating that the microcapsule components began to undergo thermal decomposition reaction at this stage. The microcapsule belongs to a glassy state before 117.97 ℃, which shows that the morphological structure of the broom corn millet shell oil microcapsule cannot be changed in the storage at room temperature and the common production and processing, so that the stability of core materials can be ensured, and the microcapsule has better thermal stability.

12. FTIR analysis of infrared spectra

Fig. 20 shows infrared spectra of broom corn millet husk oil microcapsule, broom corn millet husk oil, maltodextrin and whey protein isolate, respectively. Wherein the whey protein isolate and maltodextrin are 3700-3300cm ^-1 The positions of (2) exhibit a broad absorption peak due to the N-H bond of whey protein isolate and-OH bond of maltodextrin stretching vibration, and the microcapsules also have the characteristic and exhibit a strong absorption peak in this range. 2961.67cm ^–1 And 2924.56cm ^–1 The absorption peaks at the positions are the stretching vibration of C-H bonds of whey protein isolate and maltodextrin, respectively. Whey protein isolate 1645.65cm ^–1 The vibration peak of amide I band carbonyl is shown. Maltodextrin 1642.13cm ^–1 Is the characteristic absorption peak of olefin double bond and the characteristic absorption peak of-OH in saccharide molecule. Broom corn millet shell oil of 3010.94cm ^–1 The absorption peak is generated by stretching and vibrating C-H bonds on unsaturated fatty acid ester of millet shell oil. 2926.51cm ^–1 And 2855.73cm ^–1 The absorption peak at this point is-CH ₂ The C-H bond on the medium saturated carbon atom is generated by antisymmetric stretching vibration and symmetrical stretching vibration. 1747.15cm ^-1 The vicinity is a characteristic absorption peak of c=o of the fatty acid ester carbonyl group. Broom corn millet shell oil of 723.61cm ^-1 At more than 4 CH ₂ The C-H surface deformation vibration peak is the carbon chain of greaseRack vibration peak.

Broom corn millet shell oil microcapsule, whey protein isolate and maltodextrin with a concentration of 3700-3300cm ^-1 Similar absorption peaks exist at the positions, and no absorption peak exists at the positions of the broom corn millet shell oil, so that the broom corn millet shell oil microcapsule contains two compound wall materials of whey protein isolate and maltodextrin. Broom corn millet shell oil and broom corn millet shell oil microcapsules of 3010.94, 2926.51, 2855.73, 1747.15 and 723.61cm ^–1 The absorption peaks are all nearby, and the whey protein isolate and maltodextrin have no obvious absorption peaks nearby the positions, which indicates that the broom corn millet husk oil microcapsule contains broom corn millet husk oil. However, the absorption peak of the microcapsule product is weaker than that of broom corn millet shell seed oil, which indicates that broom corn millet shell oil is wrapped by wall materials, and the telescopic vibration is not obvious, thus proving the formation of microcapsule structure.

Claims

1. A preparation method of broom corn millet shell oil microcapsule comprises the following specific operation method:

b. preparing a core material solution: adding a compound emulsifier into broom corn millet shell oil, and stirring for 5-15 min at 40-60 ℃ to obtain a core material solution; the addition amount of the compound emulsifier is 1.8%, the wall-core ratio is 1-5:1, and the solid mass fraction is 20% -25%;

d. spray drying: spray drying the emulsion obtained in the step c under the conditions of 130-170 ℃ of air inlet temperature, 70-80 ℃ of air outlet temperature, 40-60 ℃ of feeding temperature and 10.0-12.0 mL/min of feeding speed, thus obtaining broom corn millet shell oil microcapsules;

the compound emulsifier is as follows: a mixture of span 60 and tween 60; span 60/Tween 60 is 3:7;

the composite wall material in the step a is a mixture of Whey Protein Isolate (WPI) and Maltodextrin (MD); the MD/WPI is 1.2:1.

2. The preparation method of the broom corn millet husk oil microcapsule according to claim 1, which is characterized by comprising the following specific operation method: