阅读说明：本技术 一种具有良好抗氧化和抑菌性能的玫瑰天竺葵精油微胶囊的制备方法 (Preparation method of rose geranium essential oil microcapsule with good oxidation resistance and bacterial inhibition performance ) 是由 刘夫国 韩爽 马翠翠 闫晓佳 刘学波 于 2021-09-22 设计创作，主要内容包括：本发明公开了一种具有良好抗氧化和抑菌性能的玫瑰天竺葵精油微胶囊的制备方法,属于食品加工技术领域。本发明以蛋白质和多糖作为壁材,以玫瑰天竺葵精油作为芯材；采用高速剪切、高压均质使壁材与芯材共同乳化,并调节pH、添加固化剂,通过复凝聚法制得玫瑰天竺葵精油微胶囊浊液,再经过冷冻干燥制得玫瑰天竺葵精油微胶囊。本发明制备的微胶囊能够负载并保护玫瑰天竺葵精油,提高其稳定性,使其更好地发挥抗氧化性,并具有抑菌作用；同时本发明工艺简单、条件温和、成本低廉、安全无害,适用于食品、保健品、化妆品等多种领域。(The invention discloses a preparation method of a rose geranium essential oil microcapsule with good oxidation resistance and antibacterial performance, and belongs to the technical field of food processing. The invention takes protein and polysaccharide as wall materials and takes rose geranium essential oil as core materials; the wall material and the core material are emulsified together by high-speed shearing and high-pressure homogenization, the pH value is adjusted, a curing agent is added, the rose geranium essential oil microcapsule turbid liquid is prepared by a complex coacervation method, and the rose geranium essential oil microcapsule is prepared by freeze drying. The microcapsule prepared by the invention can load and protect the rose geranium essential oil, improves the stability of the rose geranium essential oil, enables the rose geranium essential oil to better exert the oxidation resistance and has the antibacterial effect; meanwhile, the invention has simple process, mild condition, low cost, safety and harmlessness, and is suitable for various fields of food, health care products, cosmetics and the like.)

1. The preparation method of the rose geranium essential oil microcapsule with good oxidation resistance and bacterial inhibition performance is characterized by comprising the following steps:

adding rose geranium essential oil into the protein dispersion liquid for carrying out primary shearing and homogenization, and then adding the polysaccharide dispersion liquid for carrying out secondary shearing and homogenization; and adjusting the pH value for the first time to react, cooling after the reaction is finished, adjusting the pH value for the second time, adding a curing agent to continue the reaction to obtain a turbid microcapsule solution, and drying to obtain the rose geranium essential oil microcapsule.

2. The preparation method of the rose geranium essential oil microcapsule with good antioxidant and antibacterial properties as claimed in claim 1, wherein the protein dispersion is obtained by dissolving protein in deionized water, and the mass fraction of the protein dispersion is 1-2%; the polysaccharide dispersion liquid is obtained by dissolving polysaccharide in deionized water, and the mass fraction of the polysaccharide dispersion liquid is 0.5-2%; the rose geranium essential oil accounts for 0.25-1% by mass.

3. The method for preparing the rose pelargonium essential oil microcapsule with good antioxidant and antibacterial properties as claimed in claim 2, wherein the protein is animal protein and/or vegetable protein; the polysaccharide is one or more of chitosan hydrochloride, carboxymethyl chitosan, Arabic gum, sodium alginate, beet pectin, hyaluronic acid and xanthan gum.

4. The method for preparing the rose pelargonium essential oil microcapsule with good antioxidant and antibacterial properties according to claim 3, wherein the animal protein is one or more of whey protein, whey protein isolate, lactoferrin, casein, egg protein, surimi protein and gelatin; the vegetable protein is one or two of soybean protein and peanut protein.

5. The method for preparing the rose geranium essential oil microcapsule with good antioxidant and antibacterial properties as claimed in claim 1, wherein the conditions of the first shearing and the second shearing are as follows: rotating at 10000-15000 rpm for 3-5 min; the conditions of the first homogenization and the second homogenization are as follows: the pressure is 50-60 MPa, and the circulation is performed for 2-3 times.

6. The method for preparing the rose geranium essential oil microcapsule with good antioxidant and antibacterial properties as claimed in claim 1, wherein the pH is adjusted to 2-7 for the first time and 5-6 for the second time.

7. The method for preparing the rose geranium essential oil microcapsule with good antioxidant and antibacterial properties as claimed in claim 1, wherein the cooling is ice water bath cooling to 0-5 ℃.

8. The method for preparing the rose geranium essential oil microcapsule with good antioxidant and antibacterial properties as claimed in claim 1, wherein the curing agent is glutamine transaminase, and the addition amount is 0.25-0.3% of the total mass of the system.

9. The method for preparing the rose pelargonium essential oil microcapsule with good antioxidant and antibacterial properties as claimed in claim 1, wherein the drying is vacuum freeze drying.

10. A rose geranium essential oil microcapsule prepared by the preparation method of any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of food processing, in particular to a preparation method of a rose geranium essential oil microcapsule with good oxidation resistance and antibacterial performance.

Background

The rose geranium essential oil is extracted from rose geranium with the most rose fragrance, is often used as a substitute for expensive rose essential oil, and is called "poor rose oil", suitable for mass use and mass production. The rose geranium essential oil can be added into various high-grade perfumed soaps, perfumes and perfume products, can be used for preventing and treating mosquitoes, can be used as a natural antibacterial agent in food and the like, and has the effects of diminishing inflammation, benefiting gallbladder, preventing and resisting cancers and the like due to higher contents of monoterpene alcohols and sesquiterpenes. The rose geranium essential oil is non-toxic, non-irritant and free of side effects, so that the rose geranium essential oil is widely applied to the industries of spices, cosmetics, foods and pharmacy. However, the rose geranium essential oil is fat-soluble liquid like most of plant essential oils, is almost insoluble in water, has high volatility and poor stability, and greatly limits the further application of the rose geranium essential oil in human bodies and clinics. Therefore, new delivery or encapsulation technologies need to be explored to reduce the limitations of their testing and application and to ensure biological activity in their actual environment.

The microcapsule technology is an encapsulation protection technology for applying a polymer coating on a solid, liquid or gas material to form a microcapsule, can form a microenvironment in a capsule, control the interaction between the microenvironment and the outside to protect sensitive components in the capsule, reduce the influence of external factors on the microcapsule, facilitate the further modification of the surface of a core material, effectively improve the problems of difficult dissolution, low bioavailability, poor stability and the like of functional components in the processing process, and increase the bioactivity of an embedded substance to a certain extent. The common methods for preparing the microcapsules at present comprise emulsion polymerization, spray drying, layer-by-layer self-assembly, complex coacervation and the like, wherein the most common embedding method is the spray drying method, and the spray drying method is adopted for preparing the lavender essential oil microcapsules such as a luscious lavender essential oil and the like, so that the stability of the lavender essential oil is improved, and the release of the lavender essential oil is delayed. However, the high temperature operation in spray drying is not favorable for embedding heat-sensitive substances such as essence, and the application of the spray drying has certain limitation.

In the complex coacervation method emerging in recent years, two or more than two water-soluble polymer electrolytes with opposite charges are used as embedding materials, and the pH value is adjusted to neutralize the charges to cause the aggregation of wall materials, so that the method for embedding the core material has the advantages of simple operation, mild reaction conditions, high yield of finished products, good stability and the like. And for some oils which can not be heated, freeze drying can be further adopted to remove water so as to avoid the high temperature of spray drying and ensure the biological activity of functional components. The turui and the like take protein and polysaccharide as wall materials, green coffee oil microcapsules are prepared through complex coacervation, and researches find that the microcapsules can well load green coffee oil and obviously improve the thermal stability of the microcapsules. However, the existing research is often only to optimize the reaction pH, neglects the problems of wall material type, addition amount and proportion, core material addition amount and the like which have the same influence on the product performance, and is not sufficient for researching whether the core material can maintain the functional characteristics, such as oxidation resistance and antibacterial activity. Therefore, it is necessary to develop an essential oil microcapsule with good antioxidant and antibacterial properties.

Disclosure of Invention

The invention aims to provide a preparation method of a rose geranium essential oil microcapsule with good oxidation resistance and bacterial inhibition performance, so as to solve the problems that the core material has poor thermal stability, the functional characteristics are to be improved and the like. The invention adopts a method combining complex coacervation and vacuum freeze drying, prepares the rose geranium microcapsule product by optimizing the pH and the core wall material, and improves the activity and the efficacy to the maximum extent.

In order to achieve the purpose, the invention provides the following scheme:

one of the purposes of the invention is to provide a preparation method of a rose geranium essential oil microcapsule with good oxidation resistance and antibacterial performance, which comprises the following steps:

adding rose geranium essential oil into the protein dispersion liquid for carrying out primary shearing and homogenization, and then adding the polysaccharide dispersion liquid for carrying out secondary shearing and homogenization; adjusting pH for the first time to enable the protein and polysaccharide to have a complex coacervation reaction, cooling after reacting for 30min, adjusting the pH value for the second time, adding a curing agent, reacting for 3h to obtain a turbid microcapsule solution, and drying to obtain the rose geranium essential oil microcapsule.

Further, the protein dispersion liquid is obtained by dissolving protein in deionized water, and the mass fraction of the protein dispersion liquid is 1-2%, preferably 1%.

Further, the polysaccharide dispersion is obtained by dissolving polysaccharide in deionized water, and the mass fraction of the polysaccharide dispersion is 0.5-2%, preferably 0.5-1%.

Further, the protein dispersion liquid and the polysaccharide dispersion liquid are prepared by respectively dissolving the protein and the polysaccharide in deionized water, and stirring at 600rpm for 6h at room temperature to fully hydrate the protein dispersion liquid and the polysaccharide dispersion liquid.

Further, the mass fraction of the rose geranium essential oil is 0.25-1%.

Further, the protein is animal protein and/or plant protein;

further, the animal protein is one or more of whey protein, whey protein isolate, lactoferrin, casein, egg protein, surimi protein and gelatin; the vegetable protein is one or two of soybean protein and peanut protein; the protein is preferably whey protein isolate.

Further, the polysaccharide is one or more of chitosan hydrochloride, carboxymethyl chitosan, gum arabic, sodium alginate, beet pectin, hyaluronic acid and xanthan gum, and the polysaccharide is preferably chitosan hydrochloride or carboxymethyl chitosan.

Further, the conditions of the first shearing and the second shearing are as follows: rotating at 10000-15000 rpm for 3-5 min; the conditions may further preferably be: rotation speed 10000rpm, time 3 min.

Further, the conditions of the first homogenization and the second homogenization are as follows: circulating for 2-3 times under the pressure of 50-60 MPa; the conditions may further preferably be: the pressure is 50MPa, and the circulation is carried out for 3 times.

Further, the pH value of the first adjustment is adjusted to 2-7, preferably 4-7, by using sodium hydroxide or hydrochloric acid, and the pH value of the second adjustment is adjusted to 5-6, preferably 6, by using sodium hydroxide or hydrochloric acid.

Further, the cooling is that the temperature of the ice water bath is reduced to 0-5 ℃.

Further, the curing agent is glutamine transaminase (abbreviated as TG enzyme, the enzyme activity is 100U), and the addition amount is 0.25-0.3% of the total mass of the system, preferably 0.25%.

Further, the drying is vacuum freeze drying.

The invention also aims to provide the rose geranium essential oil microcapsule prepared by the preparation method.

In the present invention, all the raw materials are conventional commercially available raw materials.

The invention discloses the following technical effects:

(1) the rose pelargonium essential oil microcapsule prepared by the invention takes protein and polysaccharide as wall materials and rose pelargonium essential oil as core materials, has a structure of 'inner hydrophobicity and outer hydrophilicity', solves the problem that the rose pelargonium essential oil is insoluble in water, widens the application range of the rose pelargonium essential oil microcapsule, and improves the application value of the rose pelargonium essential oil microcapsule.

(2) The microcapsule is prepared by complex coacervation reaction and vacuum freeze drying technology, the reaction condition is mild, the chemical change between core wall materials is not involved in the generation process, and the effective functional components in the rose geranium essential oil are effectively retained.

(3) The microcapsule prepared by the invention can better exert the inoxidizability of the rose geranium essential oil, and the microcapsule product has good antibacterial performance, is suitable for industries such as food, medicine, health care products and cosmetics, and has wide application value.

(4) The materials used in the invention are food-grade macromolecular raw materials, do not contain organic reagents, are safe and harmless, and have simple preparation process and easy popularization; meanwhile, the selected rose geranium essential oil has the fragrance of rose, has a series of biological activities, is relatively cheap compared with expensive essential oil such as rose essential oil and the like, can meet the requirement of industrial large-scale production, and is accepted by consumers.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 shows the encapsulation efficiency of the microcapsules prepared in example 1 for rose geranium essential oil;

FIG. 2 is a scanning electron micrograph of the microcapsules prepared in example 2;

FIG. 3 is a Fourier infrared spectrum of a microcapsule prepared in example 2;

FIG. 4 is a graph of DPPH radical scavenging efficiency for microcapsules prepared in example 2;

FIG. 5 is a graph showing the effect of microcapsules prepared in example 2 on the growth of E.coli (a) and S.aureus (b);

FIG. 6 shows the encapsulation efficiency of the microcapsules prepared in example 3 for rose geranium essential oil;

FIG. 7 is a scanning electron micrograph of a microcapsule prepared according to example 4;

FIG. 8 is a Fourier infrared spectrum of a microcapsule prepared in example 4;

FIG. 9 is a graph of DPPH radical scavenging efficiency for microcapsules prepared in example 4;

FIG. 10 is a graph showing the effect of microcapsules prepared in example 4 on the growth of Escherichia coli (a) and Staphylococcus aureus (b).

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The room temperature referred to in the present invention is the indoor temperature, which is well known to those skilled in the art and will not be described herein; in particular, it is to be noted that the room temperature referred to in the present invention is 25 ℃.

Example 1

The rose pelargonium essential oil microcapsule is prepared by a complex coacervation method by using Whey Protein Isolate (WPI) and Chitosan Hydrochloride (CH) as wall materials and rose pelargonium essential oil with different concentrations as core materials according to the following method:

(1) respectively dissolving whey protein isolate and chitosan hydrochloride in deionized water, stirring at 600rpm at room temperature for 6h to fully hydrate the whey protein isolate and the chitosan hydrochloride to respectively obtain whey protein isolate dispersion and chitosan hydrochloride dispersion with mass fractions of 1%.

(2) Adding a proper amount of rose geranium essential oil into the whey protein isolate dispersion liquid obtained in the step (1) to obtain mixed liquid of which the mass fraction of the whey protein isolate is 1 percent and the mass fractions of the rose geranium essential oil are 0.25 percent, 0.5 percent, 0.75 percent and 1.0 percent respectively.

(3) Shearing and homogenizing the mixed liquor obtained in the step (2): the shearing speed is 10000rpm, and the shearing time is 3 min; homogenizing under 50MPa, and circulating for 3 times; then adding the chitosan hydrochloride dispersion liquid obtained in the step (1) into the chitosan hydrochloride dispersion liquid.

(4) Shearing and homogenizing the mixed liquor obtained in the step (3): the shearing speed is 10000rpm, and the shearing time is 3 min; homogenizing under 50MPa, and circulating for 3 times; a mixture of 0.5 wt.% WPI +0.25 wt.% rosehip essential oil +0.5 wt.% CH, 0.5 wt.% WPI +0.5 wt.% rosehip essential oil +0.5 wt.% CH, 0.5 wt.% WPI +0.75 wt.% rosehip essential oil +0.5 wt.% CH, 0.5 wt.% WPI +1.0 wt.% rosehip essential oil +0.5 wt.% CH was obtained.

(5) And (3) slowly adding sodium hydroxide dropwise to adjust the pH value of each mixed solution obtained in the step (4) to 6.7, so that complex coacervation reaction is carried out, and after the reaction is carried out for 30min, cooling the system to 5 ℃ by using an ice water bath.

(6) Adjusting the pH value of each system in the step (5) to 6, adding TG enzyme (the enzyme activity is 100U) with the mass fraction of 0.25% to carry out curing reaction for 3 hours to obtain microcapsule turbid liquid; and carrying out vacuum freeze drying to obtain the rose geranium essential oil microcapsule powder.

The encapsulation efficiency of the microcapsules obtained in example 1 for the rose geranium essential oil was determined as follows:

a. the embedding rate of the microcapsules is tested by using an ultraviolet spectrophotometry, a regression equation of the absorbance on the concentration of the ethanol solution of the rose geranium essential oil is formulated, and the specific method is as follows:

transferring 10 mu L of rose geranium essential oil into a 10mL volumetric flask, and shaking up with 95% ethanol to a constant volume to prepare an essential oil mother solution with the concentration of 1 mu L/mL. Transferring 400 mu L to a 10mL volumetric flask from the mother liquor, and shaking up with 95% ethanol to constant volume to prepare an essential oil standard sample with the concentration of 0.04 mu L/mL. And carrying out full-band scanning on the standard sample between 200 and 500nm to obtain the maximum absorption wavelength of the rose geranium essential oil.

Respectively sucking 0, 100, 200, 300, 400 and 500 mu L of essential oil mother liquor into a 10mL volumetric flask, then using 95% ethanol to fix the volume and shake up the solution to prepare standard solutions of 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 mu L/mL of essential oil. And measuring the absorbance value of the series of standard solutions under the maximum absorption wavelength, and drawing an essential oil standard curve by taking the concentration of the rose geranium essential oil as a horizontal coordinate and the absorbance value as a vertical coordinate.

b. Determination of the embedding rate:

leaching 0.01g of the microcapsule powder obtained by the method with 95% ethanol, and measuring the absorbance of the filtrate to obtain the content of the unencapsulated rose geranium essential oil; adding 0.01g microcapsule powder into 50mL ethanol, treating with 600w ultrasonic wave for 10min, stirring at 350rpm for 2h to completely extract oil from the capsule, filtering to remove insoluble substances in the mixed solution, and measuring absorbance of the solution with spectrophotometer to obtain total oil content in the sample. The embedding rate calculation formula is as follows:

as shown in FIG. 1, the encapsulation efficiency of the microcapsules obtained in example 1 for the rose geranium essential oil is shown. 0.25%, 0.5%, 0.75%, 1.0% of the cross-axis represent microcapsules of 0.5 wt.% WPI +0.25 wt.% rose geranium essential oil +0.5 wt.% CH, 0.5 wt.% WPI +0.5 wt.% rose geranium essential oil +0.5 wt.% CH, 0.5 wt.% WPI +0.75 wt.% rose geranium essential oil +0.5 wt.% CH, 0.5 wt.% WPI +1.0 wt.% rose geranium essential oil +0.5 wt.% CH, respectively. It can be seen that the core material concentration is within the range of 0.25-1%, the embedding rate of the microcapsule is increased and then decreased, and when the core material concentration is 0.5%, the embedding rate reaches 83.28%. It can be seen that the rose geranium essential oil can be encapsulated to form microcapsules, wherein the group of 0.5 wt.% WPI +0.5 wt.% rose geranium essential oil +0.5 wt.% CH works best.

Example 2

The rose pelargonium essential oil microcapsule is prepared by a complex coacervation method by using Whey Protein Isolate (WPI) and Chitosan Hydrochloride (CH) as wall materials and rose pelargonium essential oil as core materials according to the following method:

(1) respectively dissolving whey protein isolate and chitosan hydrochloride in deionized water, stirring at 600rpm at room temperature for 6h to fully hydrate the whey protein isolate and the chitosan hydrochloride to respectively obtain whey protein isolate dispersion and chitosan hydrochloride dispersion with mass fractions of 1%.

(2) Adding 0.5 mass percent of rose geranium essential oil into the whey protein isolate dispersion liquid obtained in the step (1) to obtain a mixed liquid.

(3) Shearing and homogenizing the mixed solution obtained in the step (2): the shearing speed is 12000rpm, and the shearing time is 3 min; homogenizing under 55MPa, and circulating for 3 times; then adding the chitosan hydrochloride dispersion liquid obtained in the step (1) into the chitosan hydrochloride dispersion liquid.

(4) Shearing and homogenizing the mixed solution obtained in the step (3): the shearing speed is 12000rpm, and the shearing time is 3 min; homogenizing under 55MPa, and circulating for 3 times; a mixture of 0.5 wt.% WPI +0.5 wt.% rose geranium essential oil +0.5 wt.% CH was obtained.

(5) And (3) slowly dropwise adding sodium hydroxide to adjust the pH of the mixed solution obtained in the step (4) to 4, so that the mixed solution is subjected to complex coacervation reaction, and after the reaction is carried out for 30min, cooling the system to 0 ℃ by using an ice water bath.

(6) Adjusting the pH value of each system in the step (5) to 5, adding TG enzyme (the enzyme activity is 100U) with the mass fraction of 0.3%, and carrying out curing reaction for 3h to obtain microcapsule turbid liquid; and carrying out vacuum freeze drying to obtain the rose geranium essential oil microcapsule powder.

The microscopic image of the microcapsules prepared in example 2 was measured as follows:

the microstructure of the microcapsules was observed using a biolaser confocal microscope (CLSM). The oil phase was stained with 3. mu.L of Nile Red (0.1 wt% in dimethyl sulfoxide) and the protein was stained with 3. mu.L of Fast Green (0.1 wt% in distilled water). mu.L of the sample was dropped onto a glass slide and stained with a mixture of two stains, with excitation wavelengths of 633nm and 488nm selected, and CLSM images were obtained at 40X, where the protein was stained red and the oil phase green.

Shown in fig. 2 is a microscopic image of 0.5 wt.% WPI +0.5 wt.% rose geranium essential oil +0.5 wt.% CH microcapsules obtained in example 2, in which the protein was excited to appear red at a wavelength of 633nm after fast green dyeing, and the rose geranium essential oil was excited to appear green at a wavelength of 488nm after nile red dyeing. It can be seen that the red water phase surrounds the green oil phase to form microcapsules, which are spherical, have a size of about 10 μm and good morphology.

The fourier infrared spectrum of the microcapsules prepared in example 2 was measured as follows:

taking a proper amount of microcapsule powder subjected to vacuum freeze drying, adding 50-100 times of KBr of the mass of a sample, grinding, putting into a die, performing vacuum compression by using a tablet press, dropwise adding the rose geranium essential oil on the KBr tablet, and measuring, wherein a blank KBr tablet is selected as a background. Placing the sample and the blank tablet on an infrared spectrometer at 400-4000 cm^-1Scanning within the range, the scanning times are 32 times, and the resolution is 4cm^-1。

FIG. 3 shows the IR spectrum of the rose pelargonium essential oil and the microcapsules obtained in example 2. It can be seen that the microcapsules are 1063cm^-1And 1406cm^-1The absorption peak is strong, which is the influence of citronellol, aromatic ether, olefin and other substances in the rose geranium essential oil, and the rose geranium essential oil is embedded in the microcapsule and then is 2926cm^-1The peak of C-H absorption of stretching vibration and 1717cm^-1、1445cm^-1、1369cm^-1The intensity of the characteristic peak of (a) is reduced. The infrared spectrum of the rose geranium essential oil microcapsule does not find special peak values which do not exist in the rose geranium essential oil, but the peak values are weakened or strengthened in different degrees, possibly caused by substance mixing, which indicates that no new chemical bond is generated in the microencapsulation process, no other chemical reaction occurs, and the integrity and the bioactivity of the core material are favorably ensured.

The oxidation resistance of the microcapsules prepared in example 2 was measured as follows:

dissolving WPI and CH in deionized water at equal ratio, stirring at room temperature at 600rpm for 6h to obtain WPI-CH dispersion solution with total mass fraction of 1%, adjusting pH to 6.7 to form a complex polymer, and vacuum freeze drying to obtain complex polymer powder. 0.01g of the essential oil, the composite polymer powder and the microcapsule powder are respectively added into 50mL of ethanol, treated by 600w of ultrasonic waves for 10min and then kept at 25 ℃ for 12 h. Adding 1mL of the extractive solution and 2mL of 0.1mM DPPH solution (dissolved in ethanol) into a centrifuge tube, vortexing, mixing thoroughly, incubating at room temperature in the dark for 30min, measuring absorbance at 517nm, and preparing blank, control and test groups respectively as shown in Table 1:

TABLE 1 DPPH radical scavenging methods and amounts of reagents added

DPPH radical clearance was calculated according to the following formula:

DPPH radical clearance rate ═ 1- (A)₁－A₂)/A₀×100％

As shown in the DPPH radical scavenging graph of FIG. 4, the horizontal axes WPI-CH, Essential oil, and WPI-CH-oil represent WPI-CH complex, Pelargonium roseum Essential oil, 0.5 wt.% WPI +0.5 wt.% Pelargonium roseum Essential oil +0.5 wt.% CH microcapsule, respectively. It can be seen that the radical scavenging rate of the 0.2mg/mL wall material complex is very low (1.178%), indicating that the complex alone has little anti-oxidation effect under this condition. The radical scavenging rate of the rose geranium essential oil is only 5.60 percent, because the essential oil is volatile and unstable, is lost in the experimental process, and the untreated essential oil cannot well play an anti-oxidation role at a lower concentration. The free radical clearance rate of the corresponding microcapsule reaches 54.55 percent, which shows that the microcapsule can well protect the core material and can better exert the oxidation resistance.

The bacteriostatic activity of the microcapsules prepared in example 2 was determined as follows:

taking out the frozen escherichia coli and staphylococcus aureus from a refrigerator at the temperature of-80 ℃, streaking on a nutrient agar plate, and culturing at the temperature of 37 ℃ for 24h to obtain a single colony. Single colonies on nutrient agar plates were picked up in 30mL nutrient broth and shake-cultured overnight (130rpm, 37 ℃). The overnight culture was collected in a 50mL centrifuge tube, the cells were washed twice with sterile phosphate buffer (8000 Xg, 5min, 4 ℃) and resuspended in nutrient broth, adjusting the OD 600nm of the suspension to the appropriate value for use. And then adding the bacterial suspension into a 96-well plate, diluting the composite polymer solution and the rose geranium essential oil microcapsules to the concentration range of 12.5-200 mu L/mL, and determining the absorbance value of each well. The plate was then incubated at 37 ℃ for 24 hours, the absorbance value of each well after incubation was measured again, and the difference in absorbance before and after incubation was calculated. The minimum concentration corresponding to the difference of the two is less than 0.05, namely the minimum inhibitory concentration, and the inhibitory capacity of the compound rose geranium essential oil microcapsule is obtained according to the change of absorbance.

As shown in FIG. 5, (a) and (b) are the effects of the complex and the microcapsule of example 2 on the growth of Escherichia coli and Staphylococcus aureus, respectively. The WPI-CH composite polymer has certain inhibition capacity on escherichia coli, but the effect is poor, and the inhibition effect on staphylococcus aureus is not obvious; when the concentration of the microcapsule reaches 100 mu L/mL, the growth of escherichia coli and staphylococcus aureus is obviously inhibited, and the inhibition effect of further increasing the concentration is more obvious. The essential oil can destroy the cell membrane of bacteria, meanwhile, the phenolic substances rich in the essential oil can penetrate through a phospholipid bilayer of the bacteria and be combined with proteins to prevent the bacteria from performing normal functions, and the microcapsule can slowly release the rose pelargonium essential oil in a system, so that the growth and the reproduction of the bacteria are inhibited for a long time, and the bacteriostatic action is realized.

Example 3

The rose pelargonium essential oil microcapsule is prepared by a complex coacervation method by using Whey Protein Isolate (WPI) and carboxymethyl chitosan (CMCS) as wall materials and rose pelargonium essential oil with different concentrations as core materials according to the following method:

(1) respectively dissolving whey protein isolate and carboxymethyl chitosan in deionized water, stirring at 600rpm at room temperature for 6h to fully hydrate the whey protein isolate and carboxymethyl chitosan to respectively obtain whey protein isolate dispersion and carboxymethyl chitosan dispersion with mass fractions of 1%.

(2) Adding a proper amount of rose geranium essential oil into the whey protein isolate dispersion liquid obtained in the step (1) to obtain mixed liquid of which the mass fraction of the whey protein isolate is 1 percent and the mass fractions of the rose geranium essential oil are 0.25 percent, 0.5 percent, 0.75 percent and 1.0 percent respectively.

(3) Shearing and homogenizing the mixed liquor obtained in the step (2): the shearing speed is 10000rpm, and the shearing time is 3 min; homogenizing under 50MPa, and circulating for 3 times; and then adding the carboxymethyl chitosan dispersion liquid obtained in the step (1) into the mixture.

(4) Shearing and homogenizing the mixed liquor obtained in the step (3): the shearing speed is 10000rpm, and the shearing time is 3 min; homogenizing under 50MPa, and circulating for 3 times; a mixture of 0.5 wt.% WPI +0.25 wt.% rose geranium essential oil +0.5 wt.% CMCS, 0.5 wt.% WPI +0.5 wt.% rose geranium essential oil +0.5 wt.% CMCS, 0.5 wt.% WPI +0.75 wt.% rose geranium essential oil +0.5 wt.% CMCS, 0.5 wt.% WPI +1.0 wt.% rose geranium essential oil +0.5 wt.% CMCS was obtained.

(5) And (4) slowly dropwise adding hydrochloric acid to adjust the pH value of each mixed solution obtained in the step (4) to 5.6, so that the mixed solution is subjected to complex coacervation reaction, and after the reaction is carried out for 30min, cooling the system to 2 ℃ by using an ice water bath.

(6) Adjusting the pH value of each system in the step (5) to 6.0, adding TG enzyme (the enzyme activity is 100U) with the mass fraction of 0.25%, and carrying out curing reaction for 3h to obtain microcapsule turbid liquid; and carrying out vacuum freeze drying to obtain the rose geranium essential oil microcapsule powder.

The encapsulation efficiency of the microcapsules obtained in example 3 for the rose geranium essential oil was determined in the same manner as in example 1:

FIG. 6 shows the encapsulation efficiency of the microcapsules obtained in example 3 for the rose geranium essential oil. 0.25%, 0.5%, 0.75%, 1.0% horizontal axis represents microcapsules of 0.5 wt.% WPI +0.25 wt.% rose geranium essential oil +0.5 wt.% CMCS, 0.5 wt.% WPI +0.5 wt.% rose geranium essential oil +0.5 wt.% CMCS, 0.5 wt.% WPI +0.75 wt.% rose geranium essential oil +0.5 wt.% CMCS, 0.5 wt.% WPI +1.0 wt.% rose geranium essential oil +0.5 wt.% CMCS, respectively. Similar to example 1, the core concentration was in the range of 0.25% to 1%, and the embedding rate of the microcapsules was increased and then decreased, and when the core concentration was 0.75%, the embedding rate reached 80.30%. It can be seen that the rose geranium essential oil can be encapsulated by two wall materials to form microcapsules, and in this example the 0.5 wt.% WPI +0.75 wt.% rose geranium essential oil +0.5 wt.% CMCS group works best.

Example 4

The rose pelargonium essential oil microcapsule is prepared by a complex coacervation method by using Whey Protein Isolate (WPI) and carboxymethyl chitosan (CMCS) as wall materials and rose pelargonium essential oil as core materials according to the following method:

(1) respectively dissolving whey protein isolate and carboxymethyl chitosan in deionized water, stirring at 600rpm at room temperature for 6h to fully hydrate the whey protein isolate and carboxymethyl chitosan to respectively obtain whey protein isolate dispersion and carboxymethyl chitosan dispersion with mass fractions of 1%.

(2) Adding 0.75 mass percent of rose geranium essential oil into the whey protein isolate dispersion liquid obtained in the step (1) to obtain a mixed liquid.

(3) Shearing and homogenizing the mixed solution obtained in the step (2): the shearing speed is 15000rpm, and the shearing time is 3 min; homogenizing under 60MPa, and circulating for 3 times; and then adding the carboxymethyl chitosan dispersion liquid obtained in the step (1) into the mixture.

(4) Shearing and homogenizing the mixed solution obtained in the step (3): the shearing speed is 15000rpm, and the shearing time is 3 min; homogenizing under 60MPa, and circulating for 3 times; a mixture of 0.5 wt.% WPI +0.75 wt.% rose geranium essential oil +0.5 wt.% CMCS was obtained.

(5) And (4) slowly dropwise adding hydrochloric acid to adjust the pH value of each mixed solution obtained in the step (4) to 2, so that complex coacervation reaction is carried out, and after 30min of reaction, cooling the system to 3 ℃ by using an ice water bath.

(6) Adjusting the pH value of each system in the step (5) to 6.0, adding TG enzyme (the enzyme activity is 100U) with the mass fraction of 0.25%, and carrying out curing reaction for 3h to obtain microcapsule turbid liquid; and carrying out vacuum freeze drying to obtain the rose geranium essential oil microcapsule powder.

The microscopic image of the microcapsule obtained in example 4 was measured in the same manner as in example 2:

a microscopic image of the microcapsules obtained in example 4 is shown in fig. 7. It can also be seen that the red water phase forms microcapsules around the green oil phase, the microcapsules being spherical and about 20 μm in size. The microcapsules prepared in example 2 were larger and more rounded in particle size due to the relatively more oil phase addition.

The Fourier infrared spectrum of the microcapsules obtained in example 4 was measured in the same manner as in example 2:

FIG. 8 shows the IR spectra of the rose pelargonium essential oil and the microcapsules obtained in example 4. The enhancement and the weakening of the absorption peak of the infrared spectrum of the formed microcapsule are similar to those in the example 1, which shows that no new chemical bond is generated in the process of preparing the capsule by using different wall materials, no other chemical reaction occurs, and the integrity and the biological activity of the core material are ensured.

The microcapsules obtained in example 4 were measured for oxidation resistance in the same manner as in example 2:

as shown in the DPPH radical clearance chart of FIG. 9, the horizontal axes WPI-CMCS, Essential oil, and WPI-CMCS-oil represent WPI-CMCS complex, Rose Pelargonium Essential oil, 0.5 wt.% WPI +0.75 wt.% Rose Pelargonium Essential oil +0.5 wt.% CMCS microcapsule, respectively. It can be seen that the free radical scavenging rate of the wall material composite polymer of 0.2mg/mL is also very low (3.067%), while the free radical scavenging rate of the microcapsule reaches 53.11%, which indicates that the microcapsule can well protect the core material and can make the antioxidant capacity of the microcapsule better exert.

The bacteriostatic activity of the microcapsules obtained in example 4 was determined in the same manner as in example 2:

as shown in FIG. 10, (a) and (b) are the effects of the complex and the microcapsule of example 4 on the growth of Escherichia coli and Staphylococcus aureus, respectively. The WPI-CMCS complex has no obvious inhibition effect on escherichia coli and staphylococcus aureus; the microcapsule has obvious inhibition effect on escherichia coli when the concentration reaches 100 mu L/mL, and no longer grows after reaching 200 mu L/mL, but has relatively weak inhibition capability on staphylococcus aureus. In general, the addition of the rose geranium essential oil enables the microcapsule to well inhibit the growth of gram-negative bacteria escherichia coli and gram-positive bacteria staphylococcus aureus, and provides a basis for the rose geranium essential oil as a stable natural food antibacterial agent.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.