阅读说明：本技术 一种糜子壳油微胶囊的制备方法 (Preparation method of broom corn millet shell oil microcapsule ) 是由 牛广财 苗欣月 朱丹 魏文毅 朱立斌 贾建 杨楠 徐瑞航 王思溥 宁志雪 于 2021-08-30 设计创作，主要内容包括：本发明的一种糜子壳油微胶囊的制备方法,涉及本发明涉及农产品深加工技术领域,其分为壁材溶液制备、芯材溶液制备、乳液制备和喷雾干燥四个步骤。利用本发明的一种糜子壳油微胶囊的制备方法,制得的糜子壳油微胶囊,其包埋率可达91.89％。同时,所制备的糜子壳油微胶囊的理化指标较好,其水分含量为2.55％,堆积密度为0.38g/cm～(3),休止角为38.63°,白度为81.63％,粒径分布均匀且集中,其体积平均粒径为0.892μm。为后续糜子壳油微胶囊的储藏稳定性、模拟人体胃肠道的消化吸收特性及其在食品领域的具体应用等研究奠定了一定的基础。(The invention discloses a preparation method of a broom corn millet shell oil microcapsule, relates to the technical field of deep processing of agricultural products, and comprises four steps of wall material solution preparation, core material solution preparation, emulsion preparation and spray drying. The embedding rate of the prepared broom corn millet shell oil microcapsule can reach 91.89 percent by using the preparation method of the broom corn millet shell oil microcapsule. Meanwhile, the prepared broom corn millet shell oil microcapsule has good physical and chemical indexes, the water content is 2.55 percent, and the bulk density is 0.38g/cm 3 The angle of repose was 38.63 ℃ and 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 subsequent researches on the storage stability of the chylomicron shell oil microcapsule, the digestive absorption characteristic of the simulated human gastrointestinal tract, the specific application of the chylomicron shell oil microcapsule in the food field and the like.)

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

a. preparing a wall material solution: dissolving a compound wall material in deionized water at 40-60 ℃ according to a certain proportion, placing the mixture in an ultrasonic cleaner, carrying out ultrasonic treatment at 40-60 ℃ for 20-40 min, and stirring the mixture 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 the broom corn millet shell oil, and stirring for 5-15 min at 40-60 ℃ to prepare 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 mass fraction of solid is 20-25%;

c. preparing an emulsion: 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 under the homogenizing pressure of 30-50 MPa for 10-30 min to obtain an emulsion;

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

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

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 50 ℃ according to a certain proportion, placing the mixture in an ultrasonic cleaner, performing ultrasonic treatment at 50 ℃ for 20min, and stirring the mixture at constant temperature for 30min by using 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 the broom corn millet shell oil, and stirring for 10min at 50 ℃ to prepare a core material solution; the addition amount of the compound emulsifier is 1.8 percent, the wall-core ratio is 3:1, and the mass fraction of the solid is 22 percent;

c. preparing an emulsion: 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 50 ℃ for 30min, and homogenizing under the homogenizing pressure of 40MPa for 20min to obtain an emulsion;

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

3. The method for preparing broom corn millet shell oil microcapsule according to claim 1, wherein the composite wall material of step a is a mixture of Whey Protein Isolate (WPI) and Maltodextrin (MD).

4. The method for preparing broom corn millet shell oil microcapsule according to claim 3, wherein the Whey Protein Isolate (WPI) and Maltodextrin (MD) are mixed in the following ratio: the MD/WPI is 1-3: 1.

5. The method for preparing broom corn millet shell oil microcapsules according to claim 4, characterized in that the MD/WPI is 1.2: 1.

6. The preparation method of the broom corn millet shell oil microcapsule according to claim 1, characterized in that the compound emulsifier is: a mixture of span 60 and tween 60.

7. The method for preparing broom corn millet shell oil microcapsule according to claim 6, wherein the ratio of span 60 to tween 60 is: span 60/Tween 60 is 2-5: 7.

8. The method for preparing broom corn millet shell oil microcapsule according to claim 1, wherein the ratio of span 60/tween 60 is 3: 7.

The technical field is as follows:

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

Background art:

broom corn millet (Panicum Miliaceum L.) belongs to Panicum of Gramineae, and its grain is called yellow rice after peeling, and is widely distributed in Asia and Europe in some developing countries. Broom corn millet is an important grain source, people usually eat broom corn millet, and the broom corn millet shells cannot be fully utilized and are usually discarded. The minced meat shell oil is oil extracted from broom corn millet shells, contains 5 fatty acids of linoleic acid, oleic acid, palmitic acid, linolenic acid and arachidonic acid, and has an unsaturated fatty acid content of 91.21%. The unsaturated fatty acid can effectively reduce the risk of cardiovascular diseases, and also has the effects of reducing blood fat, treating xerophthalmia, preventing cancer and the like. However, unsaturated fatty acids in the broom corn millet shell oil are easily disturbed by external factors such as light and oxygen to cause rancidity and deterioration, so that the quality and the nutritional value of the broom corn millet shell oil are reduced. The oil is embedded by adopting a microcapsule technology, so that the nutrition and functional components of the oil can be protected, and the oxidation resistance, water solubility and quality guarantee period of the oil can be improved.

Microencapsulation is a process in which tiny droplets or particles are encapsulated by a thin film of polymer without compromising the chemical properties of the core material. The microcapsules produced are typically between nanometers and micrometers. The microcapsule can achieve the purposes of protecting sensitive core materials, controlling the release efficiency of the core materials, covering unpleasant odor of the core materials, facilitating processing, diluting a trace amount of the core materials, converting liquid or gas state into solid state and the like through a physical barrier between the core materials and the wall materials. The technology has been applied to various fields such as food, biological agents, pharmaceuticals, textiles, cosmetics, agriculture, and the like by those skilled in the related art for decades.

At present, no similar technical disclosure and report is found for microencapsulation treatment of oil in broom corn millet shells. Meanwhile, the embedding effect of the broom corn millet shell grease is not referred to in the prior art. However, the existing oil microcapsules generally have the phenomena of low embedding rate, poor structural integrity, poor thermal stability, digestion characteristic, storage stability and the like, so that the intensive research on broom corn millet shell microcapsule products is needed, and positive influence is brought to the processing, transportation and storage industries of the broom corn millet shell oil microcapsule products.

The invention content is as follows:

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

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

a. preparing a wall material solution: dissolving a compound wall material in deionized water at 40-60 ℃ according to a certain proportion, placing the mixture in an ultrasonic cleaner, carrying out ultrasonic treatment at 40-60 ℃ for 20-40 min, and stirring the mixture 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 the broom corn millet shell oil, and stirring for 5-15 min at 40-60 ℃ to prepare 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 mass fraction of solid is 20-25%;

c. preparing an emulsion: 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 under the homogenizing pressure of 30-50 MPa for 10-30 min to obtain an emulsion;

d. spray drying: and c, spray drying the emulsion obtained in the step c under the conditions of air inlet temperature of 130-170 ℃, air outlet temperature of 70-80 ℃, feeding temperature of 40-60 ℃ and feeding speed of 10.0-12.0 mL/min to obtain the chyme 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 mixture in an ultrasonic cleaner, performing ultrasonic treatment at 50 ℃ for 20min, and stirring the mixture at constant temperature for 30min by using 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 the broom corn millet shell oil, and stirring for 10min at 50 ℃ to prepare a core material solution; the addition amount of the compound emulsifier is 1.8 percent, the wall-core ratio is 3:1, and the mass fraction of the solid is 22 percent;

c. preparing an emulsion: 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 50 ℃ for 30min, and homogenizing under the homogenizing pressure of 40MPa for 20min to obtain an emulsion;

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

As a further improvement 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 and 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 ratio of span 60 to tween 60 is as follows: span 60/Tween 60 is 2-5: 7.

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

The broom corn millet shell oil used in the invention is self-made in a laboratory, and the specific method refers to ' optimization of an ultrasonic auxiliary extraction process of the broom corn millet shell oil and analysis of fatty acid components ' published in food and machinery ' 2020, 5 months, Miao Yue and the like; the spray dryer is an ADL311-A spray dryer of YAMATO, Inc., Japan; the heat collection stirrer is a factory DF-1 type heat collection stirrer of a gold jar rainbow instrument; KH-500DE ultrasonic cleaner; the high-pressure homogenizer was a model GEA high-pressure homogenizer from Niro soavi, Italy.

The broom corn millet shell oil microcapsule prepared by the preparation method of the broom corn millet shell oil microcapsule has complete particle shape and embedding rate of 91.89%. Meanwhile, the prepared broom corn millet shell oil microcapsule has good physical and chemical indexes, the water content is 2.55 percent, and the bulk density is 0.38g/cm³The angle of repose was 38.63 ℃ and 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 product is good in high-temperature environment, and the product has a long shelf life under normal temperature.

Description of the drawings:

FIG. 1 shows the effect of the addition of emulsifier on emulsion stability and microcapsule embedding rate;

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

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

FIG. 4 shows the effect of solid mass fraction on emulsion stability and microcapsule embedding rate;

FIG. 5 is a response surface diagram and a contour diagram of the influence of the addition amount of the emulsifier and the ratio of the wall materials on the embedding rate;

FIG. 6 is a response surface diagram and a contour diagram of the influence of the addition amount of the emulsifier and the mass fraction of the solid matter on the embedding rate;

FIG. 7 is a graph showing the effect of inlet air temperature on the encapsulation efficiency of microcapsules;

FIG. 8 is a graph of the effect of homogenization time on the encapsulation efficiency of microcapsules;

FIG. 9 is a graph of the effect of feed temperature on the encapsulation efficiency of microcapsules;

FIG. 10 is a graph of the effect of feed rate on the encapsulation efficiency of microcapsules;

FIG. 11 is a graph of a response surface and a contour plot of the effect of interaction of factors on embedding 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 chylomicron shell oil microcapsules;

FIG. 14 shows the POV value variation of the broom corn millet shell oil and the broom corn millet shell oil microcapsules at different temperatures;

FIG. 15 is a zero-order reaction linear regression analysis of the variation trend of POV values of the chylomicron shell oil microcapsules at different temperatures;

FIG. 16 is a first order reaction linear regression analysis of the variation trend of POV values of the chylomicron shell oil microcapsules at different temperatures;

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

FIG. 18 is a TG plot of chylomicron shell oil microcapsules;

FIG. 19 is a DSC of broom corn millet shell oil microcapsules;

fig. 20 is an infrared spectrogram of the minced meat shell oil microcapsule and the components thereof (in the figure, the spectrogram from top to bottom is broom corn millet shell oil microcapsule, broom corn millet shell oil, maltodextrin and whey protein isolate in sequence).

The specific implementation mode is as follows:

example 1

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

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 40 ℃ according to a certain proportion, placing the mixture in an ultrasonic cleaner, performing ultrasonic treatment at 40 ℃ for 20min, and stirring the mixture at constant temperature for 20min by using 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 the 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 percent, the wall-core ratio is 1:1, and the mass fraction of the solid is 20 percent; 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. preparing an emulsion: 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 ℃ for 20min, and homogenizing under the homogenizing pressure of 30MPa for 10min to obtain an emulsion;

spray drying: and d, spray drying the emulsion obtained in the step c under the conditions of air inlet temperature of 130 ℃, air outlet temperature of 70 ℃, feeding temperature of 40 ℃ and feeding speed of 10.0mL/min to obtain the minced shell oil microcapsule.

Example 2

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

a. preparing a wall material solution: dissolving a compound wall material in deionized water at 60 ℃ according to a certain proportion, placing the mixture in an ultrasonic cleaner, performing ultrasonic treatment at 60 ℃ for 40min, and stirring the mixture at constant temperature for 40min by using 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 the broom corn millet shell oil, and stirring for 15min at 60 ℃ to prepare a core material solution; the addition amount of the compound emulsifier is 2.0 percent, the wall-core ratio is 5:1, and the mass fraction of solid is 25 percent; 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. preparing an emulsion: 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 under the homogenizing pressure of 50MPa for 30min to obtain an emulsion;

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

Example 3

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

a. preparing a wall material solution: dissolving the compound wall material in deionized water at 50 ℃ according to a certain proportion, placing the mixture in an ultrasonic cleaner, performing ultrasonic treatment at 50 ℃ for 20min, and stirring the mixture at constant temperature for 30min by using 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 as follows: MD/WPI is 1.2: 1;

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

c. preparing an emulsion: 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 50 ℃ for 30min, and homogenizing under the homogenizing pressure of 40MPa for 20min to obtain an emulsion;

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

Physicochemical and functional tests were carried out on the broom corn millet shell oil microcapsules prepared by the method described in example 3 as follows:

the measuring method comprises the following steps:

1. method for measuring emulsion stability

The centrifugal speed is 8000r/min, and the centrifugation is carried out for 10 min. And (3) putting a certain amount of the emulsion into a centrifugal tube with scales, centrifuging, reading the volume of a free water layer, and calculating the stability of the emulsion system. The emulsion stability is calculated according to equation (1).

2. Determination of embedding rate of chyme shell oil microcapsules

(1) Method for measuring microcapsule surface oil

According to the method of the tensor sensitive method and with slight modification, a supernatant is obtained by a centrifugal method, and a filtrate is evaporated by a rotary evaporator to obtain the minced shell oil. 2.000g (m) are weighed₀) And placing the prepared broom corn millet shell oil microcapsule into a 50mL test tube with a plug, adding 30mL petroleum ether (boiling range is 30-60 ℃), performing vortex oscillation for 2min, centrifuging for 20min under the condition of 5000r/min, taking supernatant, adding 15mL petroleum ether to clean bottom residues, centrifuging, collecting supernatant, and repeating the operation. The combined supernatants were placed in a rotary evaporator (m) of constant weight₁) Rotary evaporation was performed. Then transferring the mixture to an oven at 105 +/-1 ℃ for drying to constant weight (m)₂)。

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

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

Weighing 2g (to the nearest 0.001, m)₀) Placing the minced shell oil microcapsule in a beaker, adding 10mL of hot water at 60 ℃, stirring to fully dissolve a sample, adding 1.25mL of ammonia water for uniformly mixing, after 10min of water bath at 60 ℃, shaking for 2min while hot, adding 10mL of absolute ethyl alcohol for shaking uniformly, cooling with cold water, adding 20mL of diethyl ether for shaking for 30s, adding 20mL of petroleum ether for shaking for 30s, placing in a separating funnel, standing for layering, collecting supernatant, and placing in a rotary evaporation bottle (m is constant weight) (m is a constant weight) with constant weight₁) Rotary evaporation was performed. Then transferring the mixture to an oven at 105 +/-1 ℃ for drying to constant weight (m)₂). Each sample was run in 3 replicates. The total oil content and the embedding rate of the microcapsules are calculated according to the formulas (3) and (4).

3. Single-factor experiment for preparing formula of chyme shell oil microcapsule emulsion

(1) Influence of addition amount of emulsifier on emulsion stability and embedding rate

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

(2) Influence of wall-core ratio on emulsion stability and embedding rate

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

(3) Effect of MD/WPI on emulsion stability and entrapment efficiency

Under the conditions that the wall-core ratio is 3:1, the addition amount of the emulsifier is 2.0%, and the solid matter content is 20%, the influences of MD/WPI of 1:1, 2:1, 3:1, 4:1 and 5:1 on the stability of the broom corn millet shell oil emulsion and the embedding rate of the broom corn shell oil microcapsules are examined.

(4) Influence of solid mass fraction on emulsion stability and embedding rate

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

4. Response surface optimization test for preparing chyme 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 of B, the mass fraction of C MD/WPI and D solid are selected, the embedding rate of the broom corn millet shell oil microcapsule is taken as a response value, a Box-Behnken design is adopted, and an optimization test is carried out on the preparation process of the broom corn shell oil microcapsule emulsion, wherein the factor level is shown in Table 1.

TABLE 1 response surface test factor level coding table

5. Single factor test of spray drying process of chylomicron shell oil microcapsule

On the basis of the response surface optimization test prepared by the broom corn millet shell oil microcapsule emulsion 4, the following test is carried out under the homogenizing pressure of 40MPa according to the process conditions of the optimal emulsifier adding amount, the wall-core ratio, the MD/WPI and the solid matter mass fraction.

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

And (3) under the conditions of homogenizing time of 20min, feeding temperature of 50 ℃ and feeding speed of 11.3mL/min, observing the influence of the inlet air temperatures of 120, 130, 140, 150 and 160 ℃ on the embedding rate of the broom corn millet shell oil microcapsules.

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

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

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

Under the conditions of 10 ℃ of air inlet temperature, 20min of homogenization time and 11.3mL/min of feeding speed, the influence of the feeding temperatures of 40, 45, 50, 55 and 60 ℃ on the embedding rate of the minced shell oil microcapsules is examined.

(5) Influence of feed rate on embedding rate of broom corn millet shell oil microcapsules

Under the conditions that the air inlet temperature is 150 ℃, the feeding temperature is 50 ℃ and the homogenizing time is 20min, the influence of the 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 microcapsules is examined.

6. Response surface optimization test of spray drying process of chyme shell oil microcapsule

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

TABLE 2 response surface test factor level coding table

7. Surface morphology observation of chylomicron shell oil microcapsules

The surface morphology of the minced shell oil microcapsule is observed by a Scanning Electron Microscope (SEM). And (3) sprinkling the minced shell oil microcapsule on a sample table adhered with a double-sided adhesive, blowing off redundant powder, then carrying out gold spraying treatment on the sample, and observing the microstructure of the minced shell oil microcapsule by using an SEM (scanning Electron microscope) under the accelerating voltage of 5.0KV within a short time.

8. Determination of basic physicochemical indexes of minced shell oil microcapsule

(1) Determination of moisture content of microcapsules

Using a sample plate (mass m)₀) Accurately weighing 2.000g of broom corn millet shell oil micro-gelCapsule sample (total weight of sample and sample dish is m)₁) Drying in an oven at 105 deg.C for 3 hr, cooling in a desiccator, weighing, drying the microcapsule sample in the oven for 1 hr, cooling, weighing, repeating the operation until the mass difference between the samples is less than 0.001g, and recording the mass (m) of the sample and the sample plate₂) The moisture content is calculated according to formula (5).

(2) Determination of microcapsule bulk Density

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

(3) Determination of the flowability of microcapsules

Accurately weighing 10g of broom corn millet shell oil microcapsule sample in a funnel, naturally dropping the sample onto a horizontal circular plate through the funnel, stacking to a certain height, measuring the height H of a powder pile and the covering 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 microcapsule whiteness

And pouring the prepared microcapsule sample into a flat dish, flatly paving the microcapsule sample to a certain thickness, correcting the microcapsule sample by a color difference meter, measuring the L, a and b color values of the microcapsule sample, and calculating the whiteness according to a formula (7).

In the formula, L represents brightness, a represents red-green degree, and b represents yellow-blue degree.

9. Measurement 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 chart.

10. Data processing

Design-Expert 8.0.6 was used for response surface test Design and analysis, SPSS 25.0 and Origin 8.5 software was used for statistical analysis and mapping of data, each set of experiments was repeated 3 times, and the experimental data are presented as mean ± standard deviation.

11. Storage test and shelf life test

Placing the minced meat shell oil and the broom corn millet shell oil microcapsules in incubators with the temperature of 25 ℃, 35 ℃ and 45 ℃ respectively, placing for 2 months, measuring the POV values of the minced meat shell oil and the broom corn millet shell oil microcapsules every 5-7 days, researching the storage stability of the minced meat shell oil and the broom corn millet shell oil microcapsules under different temperature conditions, fitting an oxidation kinetic equation of the POV values of the minced meat shell oil microcapsules and predicting the shelf life of the minced meat shell oil and the broom corn millet shell oil microcapsules.

12. Thermogravimetric (TG) analysis

Accurately weighing a certain amount of broom corn millet shell oil microcapsules, and analyzing the thermogravimetry of the product by a thermogravimetric analyzer. Controlling the heating rate to be 10 ℃/min, the nitrogen flow rate to be 30mL/min, and the scanning temperature range to be 0-650 ℃.

13. DSC (differential scanning calorimeter) analysis

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

Second, results and analysis

1. Single factor test for preparation of chyme shell oil microcapsule emulsion formula

(1) Influence of addition amount of emulsifier on emulsion stability and microcapsule embedding rate

As can be seen from FIG. 1, the amount of the emulsifier added is in the range of 0.5 to 1.5%, the emulsion stability rises rapidly, and the emulsion stability does not rise much when the amount of the emulsifier is continuously increased. The reason is that the emulsifier reaches the critical micelle concentration when the dosage is 1.5 percent, the emulsifier can be completely attached to the surface of emulsified emulsion shell oil particles, the oil-water interfacial tension is reduced, the emulsification stability is rapidly improved, and the embedding rate of the microcapsule reaches the maximum value of 86.94 percent. The amount of the emulsifier is continuously increased, and the redundant emulsifier exists in the solution in the form of micelle, so that the interfacial tension of oil and 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 redundant emulsifier increment can cause the size of the liquid drop to be enlarged, and the liquid drop is further coalesced. Too much emulsifier can increase the viscosity of the emulsion, which is not beneficial to the combination of the core material and the wall material, and reduces the embedding rate. Therefore, the optimum amount of emulsifier to be added is selected to be 1.5%.

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

As can be seen from fig. 2, the emulsion stability tended to increase with the increase in the wall-core ratio, and the embedding rate first increased and then decreased. When the wall-core ratio is 3:1, the embedding rate is up to 86.67 percent, 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 use amount of the wall material is continuously increased, the emulsion stability is not greatly changed, and the water in the core material and the wall material is difficult to volatilize to form a cavity of the wall material in the spray drying process due to the excessively thick wall, 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) Effect of MD/WPI on emulsion stability and microencapsulation embedding rate

As can be seen from FIG. 3, the emulsion stability and the entrapment rate are highest at 2:1 MD/WPI, because WPI has good film-forming property and emulsifying property, and higher content of WPI is beneficial to better wrapping the chyme shell oil. When the MD/WPI is within the range of 2: 1-3:1, the emulsion stability and the microcapsule embedding rate both tend to decrease, because the emulsifying capacity of the emulsion is reduced due to the decrease of the WPI content, the emulsifying stability of the emulsion is weakened, so that the film forming property of the chyle shell oil microcapsule emulsion in the spray drying process is reduced, and the embedding rate of the chyle shell oil microcapsule is reduced. Therefore, the optimum composite wall material ratio (MD/WPI) was selected to be 2: 1.

(4) Influence of solid mass fraction on emulsion stability and embedding rate

The solid matter mass fraction is within 5-20%, the emulsion stability and the microcapsule embedding rate are both obviously improved, mainly because the solid matter concentration is increased, the solution viscosity is increased, and the Brownian motion of molecules is slowed down, so that the stability is enhanced; the mass fraction of the solid is increased, the water required to be evaporated in the spray drying process is reduced, the capsule wall is formed quickly, the thickness is increased, and therefore the embedding rate is gradually increased. When the mass fraction of the solid substance continues to increase, the stability of the emulsion changes slowly, and the viscosity of the solution increases, so that the atomization effect is weakened, and the embedding rate is reduced. Bear yueqin also indicates that when the concentration of the solid matter is too high, the atomization speed in the spray drying process is reduced, the material stagnation time is prolonged, the loss of low-boiling-point substances is increased, and the embedding rate is reduced. Therefore, the optimum solid mass fraction was selected to be 20%.

2. Response surface optimization test prepared by emulsion formula of chyme shell oil microcapsule

(1) Box-Behnken experimental design and results

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

TABLE 3Box-Behnken test design and results

Performing regression fitting on the test result of the response surface 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-4.53A²-4.95B²-3.61C²-4.41D²

(2) response surface experimental analysis of variance

As can be seen from Table 4, the regression model is extremely significant (P)<0.01), the mismatching term P is 0.0754>0.05 was not significant. Regression coefficient R²0.9738, the model correlation is good, i.e. the predicted value of the regression model can be well matched with the actual value. Model A, B, C, D, A²、B²、C²、D²The influence of AC and AD is very obvious (P is less than 0.01); BC. BD, CD, AB did not significantly affect (P)>0.05). The influence of the embedding rate of the chylomicron shell oil microcapsule is as follows in sequence: wall material ratio > emulsifier addition amount > wall core ratio > solid mass fraction.

TABLE 4 regression model analysis of variance

Note: p <0.05, significant difference; p <0.01, the difference was very significant.

Different factors interactively influence the response surface graph and the contour graph of the embedding rate of the chylomicron shell oil microcapsule, as shown in fig. 5 and fig. 6. As can be seen from FIG. 5, the embedding rate of the chylomicron shell oil microcapsule firstly increases and then decreases along with the increase of the addition amount of the emulsifier and the increase of the MD/WPI ratio, the slope of the curved surface graph is steep, and the contour graph is elliptic, which shows that the interaction between the addition amount of the emulsifier and the MD/WPI composite ratio is remarkable. As can be seen from fig. 6, when the amount of the emulsifier is constant, the embedding rate of the broom corn millet shell oil microcapsules increases and then decreases as the mass fraction of the solid matter increases; when the solid matter mass fraction is constant, the embedding rate of the broom corn millet shell oil microcapsule also shows a trend that the embedding rate is increased firstly and then reduced along with the increase of the addition amount of the emulsifier, and the contour line is elliptic, which shows that the interaction effect of the two factors is obvious.

(3) Verification test for optimization of emulsion process of chyme shell oil microcapsule

After being analyzed by Design-Expert 8.0.6 software, the optimal parameter conditions of the obtained minced shell oil microcapsule emulsion are as follows: the addition amount of the emulsifier is 1.82 percent, the wall-core ratio is 3.2:1, the MD/WPI is 1.16:1, and the mass fraction of solid is 22.10 percent. The theoretical value of the embedding rate of the broom corn millet shell oil microcapsules under the condition is 89.81% through the analysis of the software. Considering the convenience of actual operation, the process for preparing the emulsion of the chylomicron shell oil microcapsule 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, and the mass fraction of the solid matter is 22%. Meanwhile, the embedding rate of the broom corn millet shell oil microcapsule under the condition is higher than the maximum embedding rate of 87.40% of a response surface test in the table 3, which shows that the model is correct and can be suitable for optimizing the emulsion process of the broom corn millet shell oil microcapsule.

3. Single factor test of spray drying process of chylomicron shell oil microcapsule

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

As can be seen from FIG. 7, when the air inlet temperature is in the range of 120-150 ℃, the embedding rate of the broom corn millet shell oil microcapsules is remarkably increased and reaches the 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 formation is accelerated along with the increase of the inlet air temperature, and the core material is not easy to lose; however, when the temperature of the inlet air is too high, the water loss speed is too high, the microcapsule structure becomes loose, the core material is not protected, and the embedding rate is reduced. Wanghong also indicates that the rising of the air inlet temperature breaks the balance between the water evaporation rate on the surface of the liquid drop and the film forming, so that cracks are generated on the surface of the microcapsule powder, and grease is oozed out. Therefore, the optimum intake air temperature was selected to be 150 ℃.

(2) Effect of homogenization time on microencapsulation embedding Rate

As can be seen from fig. 8, when the homogenization time is in the range of 10-15min, the embedding rate of the broom corn millet shell oil microcapsules increases and reaches a maximum value of 91.11%, which may be because the stability of the emulsion is already in an optimal state when the homogenization time is 15min, and when the homogenization time continues to increase, the embedding rate of the microcapsules tends to decrease because the original stable system of the emulsion is destroyed by the too long homogenization time, so that the embedding rate decreases. Therefore, the optimum homogenization time was selected to be 15 min.

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

As can be seen from fig. 9, as the feed temperature increased, the microencapsulation entrapment rate increased first and then decreased. The highest microencapsulation encapsulation efficiency was 89.77% at a feed temperature of 50 ℃. When the feeding temperature is increased continuously, the embedding rate of the microcapsules is reduced remarkably, which is probably because the microcapsules are easy to be gelatinized by heat under the high-temperature condition due to the overhigh feeding temperature, so that the embedding rate is reduced. Therefore, the optimum feed temperature was selected to be 50 ℃.

(4) Effect of feed Rate on the encapsulation efficiency of microcapsules

As can be seen from FIG. 10, when the feeding speed is in the range of 5.2-11.3mL/min, the embedding rate of the microcapsules increases significantly, but when the feeding speed is increased continuously, the embedding rate of the microcapsules decreases significantly, because when the feeding speed is too high, the evaporation time of the material is insufficient, the complete capsule wall cannot be formed, the product particles are larger, and the embedding rate is reduced. Furthermore, the effect of the feed rate on peony seed oil microcapsules was also noted in the study of the bang-bang of liu: when the feeding speed is too low, the energy consumption is too high, the efficiency is not high, and the method is allowed in the actual industrial production; and too high a feed rate can also result in a lower or unstable outlet temperature for spray drying. Therefore, the optimum feed rate was selected to be 11.3 mL/min.

4. Response surface optimization test of spray drying process of chyme shell oil microcapsule

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

TABLE 5 Box-Behnken test design and results

TABLE 6 regression model analysis of variance

Note: p <0.05, significant difference; p <0.01, the difference was very significant.

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

Y＝90.69-0.95A-0.25B+0.86C-0.099D-0.64AB-0.22AC+0.80AD+1.95BC+1.89BD+2.53CD-5.73A²-1.49B²-1.60C²-2.58D² (6)

as can be seen from Table 6, the regression model had a very significant effect (P)<0.01), the simulation loss term P is 0.1814>0.05 was not significant. Regression coefficient R²0.9764, the model correlation is good, i.e. the predicted value of the regression model can be well matched with the actual value. The primary term A, C in the model has extremely significant influence (P < 0.01) and influences the factor A>C; the interactive items BC, BD and CD have extremely obvious influence (P is less than 0.01), and the AD has obvious influence (P is less than 0.05); second order term A²、B²、C²、D²The effect is very significant (P < 0.01). The response surface and contour plot of the effect of the interaction of the factors on the embedding rate is shown in fig. 11.

5. Response surface optimization verification test of spray drying process of chylomicron shell oil microcapsule

After being analyzed by Design-Expert 8.0.6 software, the optimal process conditions for preparing the minced shell oil microcapsule by the spray drying method are as follows: the air inlet temperature is 148.98 ℃, the homogenizing time is 20min, the feeding temperature is 55 ℃, the feeding speed is 13.84mL/min, and the embedding rate theoretical value is as follows: 92.01 percent. And properly adjusting the process parameters of the model optimization by combining the practical situation as follows: the air inlet temperature is 150 ℃, the homogenizing time is 20min, the feeding temperature is 55 ℃, the feeding speed is 14.4mL/min, and the average embedding rate of the minced shell oil microcapsule is 91.89% and is close to the predicted value through experiments under the condition.

6. Surface morphology observation of chylomicron shell oil microcapsules

Fig. 12 is an external structural view of the broom corn millet shell oil microcapsule amplified 3200 times, and it can be seen that the particle surface of the broom corn millet shell oil microcapsule is smooth and continuous and has no cracks. The surface of a few particles has concave or irregular shapes, which may be instantaneous water evaporation in the process of wall material solidification in the spray drying process, so that the water evaporation in the microcapsules and external air flow form a pressure difference to form concave parts at parts with smaller thickness and hardness. In addition, during the process of spraying gold on a scanning electron microscope, the phenomenon is also aggravated by the excessively high vacuum. From the whole view, the prepared broom corn millet shell oil microcapsule has a smooth surface and good encapsulation property. It can effectively protect the minced shell oil and prevent the minced shell oil from being oxidized, thereby improving the storage stability of the minced shell oil.

7. Physicochemical index of minced shell oil microcapsule

The moisture content, bulk density, angle of repose, whiteness, etc. of the microcapsules 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 undesirable microbial activity in the environment is inhibited, and the storage property of the product is improved; when the moisture content is high, the phenomena of mildew, caking and the like occur, and the product quality is reduced. The microcapsules have a greater bulk density, indicating that they can be stored in a smaller volume in a greater amount, reducing the amount of oxygen in the interstitial spaces of the particles, and slowing down oxidation. The angle of repose is an important index for measuring the flowability of powder products, and the smaller the angle of repose is, the flowability of the products isThe better. Generally, the fluidity of the powder is good when the angle of repose is less than or equal to 30 ℃; the product has good fluidity when the angle of repose is 30-45 degrees; when the angle of repose is 45-60 degrees, the fluidity of the product is general; the fluidity of the product is poor when the angle of repose is more than or equal to 60 DEG^[13]. The whiteness of the microcapsule can be used for measuring the embedding effect of the microcapsule, the whiteness value is higher, the oil can be fully wrapped by the wall material, the surface oil is less, and the higher whiteness value also indicates that the oil is not oxidized due to overhigh temperature in the spray drying process. As can be seen from table 7, the moisture content of the broom corn millet shell oil microcapsule is 2.55%, which is substantially the same as that of other microcapsule powders, indicating that the moisture evaporation of the microcapsule is complete during the spray drying process, the product is fully dried, the bad activity of external microorganisms can be effectively inhibited, and the storage stability is improved. The bulk density was 0.38g/cm³The product is shown to slow oxidation. The angle of repose is 38.63 degrees, which shows that the product has better fluidity and can be conveniently used. The whiteness of the minced shell oil microcapsule is 81.63%, which shows that the embedding effect of the oil after spray drying is better.

TABLE 7 physicochemical indices of the chylomicron shell oil microcapsules

8. Particle size distribution of chylomicron 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 better dispersibility. From the application point of view, the microcapsule with too large particles may cause uncomfortable taste, and the microcapsule with small particle size is easier to be absorbed by human body. Fig. 13 is a particle size distribution diagram of the chylomicron shell oil microcapsules. The equivalent diameters of the largest particles at cumulative distributions of 10%, 50% and 90% in the distribution curve are D_X(10)＝0.559μm、D_X(50)＝0.843μm、D_X(90) The maximum particle size, which indicates a cumulative distribution of 90%, is 1.407 μm. As can be seen from FIG. 7, the particle size distribution of the broom corn millet shell oil microcapsule is normal and relatively narrow, and the particle size isMost of them were concentrated in the range of 0.3 to 3 μm, and only one peak was observed in this particle size range, and the volume average particle size was 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 of POV during storage

As can be seen from fig. 14, the POV of both the broom corn millet shell oil and the broom corn millet shell microcapsules changed slowly before 12 days of storage, and the oxidation rates of the broom corn millet shell oil at 25 ℃ and the broom corn millet shell oil microcapsules at 45 ℃ tended to increase with the increase of the number of days of storage. This may be due to the fact that the deteriorated components (aldehydes, ketones, alcohols, low-molecular fatty acids, etc.) in the cream shell oil are less in the initial stage of storage; with the increase of storage days, the deterioration components increase, and the peroxide value rapidly rises under the combined action of oxygen and temperature. As can be seen from fig. 14: the POV value of the minced-millet-shell oil microcapsule stored at 45 ℃ is obviously higher than that of the minced-millet-shell oil microcapsule stored at 25 ℃ and 35 ℃, which indicates that the minced-millet-shell oil microcapsule is required to avoid a high-temperature environment as much as possible in the storage process. In addition, the change of the peroxide value of the microcapsule of the minced shell oil stored at 25 ℃ is the slowest and is obviously lower than the POV value of the minced shell oil at the same temperature, which indicates that the whey protein isolate and the maltodextrin are used as a compound wall material to effectively embed the minced shell oil and slow down the oxidation speed of the minced shell oil.

(2) Oxidation kinetics research and shelf life prediction of POV (polyester pre-oriented tension) value of broom corn millet shell oil microcapsule

Using zero order reaction equations, respectively

C＝C₀-*kt

And first order reaction equation

lnC＝lnC₀-kt

And performing linear regression analysis on the POV value changes of the broom corn millet shell oil and the broom corn millet shell oil microcapsules.

TABLE 8 Linear regression analysis of POV value variation for chylomicron shell oil microcapsules

As can be seen from table 8, the difference between the regression coefficient of the first order reaction at 25 ℃ and the regression coefficient of the zero order is not large, and the regression coefficients of the first order reaction at 35 ℃ and 45 ℃ are both larger than the regression coefficient of the zero order, i.e., the degree of fitting to the first order oxidation reaction is higher than that of 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 fig. 16). The minced meat shell oil microcapsules are stored at the temperature of 25 ℃, 35 ℃ and 45 ℃, and the change constants k of pov along with time are 0.0112, 0.0199 and 0.0362 respectively. According to the arrhenius equation:

lnk＝lnk₀-Ea/RT

a linear fit was made to lnk- -1/T, see Table 9 and FIG. 17.

TABLE 9 Fit constants for POV values for chylomicron shell oil microcapsules

The linear expression of the Arrhenius equation from fig. 17 is lnk ═ -5560/T +14.149, R²＝0.9981，-Ea/R＝-5560，lnk₀14.149, the calculated activation energy Ea is 46.00KJ/mol 46000J/mol, k₀1395830. The POV initial value is 2.61mmol/kg, the national limit for common vegetable oil is specified (the peroxide value is less than or equal to 10.0m mol/kg), and according to a shelf life prediction model of POV:

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

10. Thermogravimetric analysis (TG) of chylomicron shell oil microcapsules

Fig. 18 is a TG curve of the broom corn millet shell oil microcapsule, when the temperature range is 35-100 ℃, the loss of the broom corn millet shell oil microcapsule is about 2.2%, and as can be seen from a DSC curve (fig. 19), the broom corn millet shell oil microcapsule starts to be dissolved endothermically in the temperature range, the quality of the microcapsule loss is mainly free water in the microcapsule sample, and the curve shows a small-amplitude decreasing trend due to the lower moisture content; when the temperature range is 100-160 ℃, the curve tends to be gentle and almost no weight loss phenomenon exists. And the microcapsule starts to be rapidly degraded at 160 ℃ until the degradation is basically finished at 410 ℃, the mass loss at this stage is excessive and is about 80%, the slope of the curve is large, the microcapsule structure is seriously damaged, the chemical bond is broken, the 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 nearly 84%. According to the graph of fig. 18, when the microcapsule starts to decompose after 160 ℃, it is shown that the microcapsule product can maintain good thermal stability in the environment below 160 ℃, i.e. can maintain stability in the general production process.

11. DSC chart of chylomicron shell oil microcapsule

As shown in fig. 19, the broom corn millet shell oil microcapsule starts endothermic dissolution at 61.05 ℃ and reaches a peak at 117.97 ℃, and the glass transition temperature of the microcapsule is 117.97 ℃ because the first endothermic peak temperature occurring during the heating of the substance is called glass transition temperature (Tg). The reaction at this stage is a heat absorption phenomenon that the wall material components of the microcapsule are heated and swelled at high temperature, and the ordered crystal is converted into an unordered crystal structure. When the temperature is increased to 200 ℃, the 2 nd absorption peak is 216 ℃, and the micro-capsule starts to be rapidly degraded at 160-410 ℃ by combining with a thermogravimetric analysis curve (figure 18), which indicates that the micro-capsule components start to be subjected to thermal decomposition reaction at the stage. Because the microcapsule is in a glass state before 117.97 ℃, the morphological structure of the broom corn millet shell oil microcapsule can not be changed during room temperature storage and general production and processing, the stability of a core material can be ensured, and the thermal stability is better.

12. FTIR analysis of Infrared Spectroscopy

Fig. 20 is an infrared spectrum of broom corn millet shell oil microcapsule, broom corn millet shell oil, maltodextrin and whey protein isolate. Wherein the whey protein isolate and maltodextrin are present at 3700-3300cm^-1All are inExhibits a broad absorption peak due to stretching vibration of the N-H bond of whey protein isolate and the-OH bond of maltodextrin, and the microcapsules have this property, and also exhibit a strong absorption peak in this range. 2961.67cm^–1And 2924.56cm^–1The absorption peaks at the positions are the stretching vibration of the C-H bond of the whey protein isolate and the maltodextrin respectively. Whey protein isolate 1645.65cm^–1The peak is the vibration peak of amide I with carbonyl. Maltodextrin 1642.13cm^–1The position is a characteristic absorption peak of an olefin double bond and a characteristic absorption peak of-OH in a saccharide molecule. The minced shell oil is 3010.94cm^–1The absorption peak is generated by stretching vibration of C-H bond on unsaturated fatty acid ester of broom corn millet shell oil. 2926.51cm^–1And 2855.73cm^–1The absorption peak at is-CH₂The C-H bond on the middle saturated carbon atom generates antisymmetric stretching vibration and symmetric stretching vibration. 1747.15cm^-1The characteristic absorption peak of C ═ O of the fatty acid ester carbonyl group is in the vicinity. The minced shell oil is 723.61cm^-1Is in more than 4 CH₂The deformation vibration peak of the C-H surface of (2) is a vibration peak of a carbon chain skeleton of the oil.

The chyle shell oil microcapsule, whey protein isolate and maltodextrin are 3700-3300cm^-1Similar absorption peaks exist on the positions, and the broom corn millet shell oil has no absorption peak on the positions, which indicates that the broom corn millet shell oil microcapsule contains two compound wall materials of whey protein isolate and maltodextrin. The minced meat shell oil and the broom corn millet shell oil microcapsule are 3010.94, 2926.51, 2855.73, 1747.15 and 723.61cm^–1Absorption peaks are found nearby, and whey protein isolate and maltodextrin have no obvious absorption peaks nearby the positions, which indicates that the minced shell oil microcapsule contains the minced shell oil. But the absorption peak of the microcapsule product is weaker than that of the emulsion shell seed oil, which shows that the emulsion shell oil is wrapped by the wall material, the stretching vibration is not obvious, and the formation of the microcapsule structure is proved.