AU2020314346B9

AU2020314346B9 - Starch-based highly stable pickering emulsion and preparation method thereof

Info

Publication number: AU2020314346B9
Application number: AU2020314346A
Authority: AU
Inventors: Xiong FU; Qiang Huang; Songnan Li; Bin Zhang; Zixi ZHU
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2019-07-17
Filing date: 2020-04-01
Publication date: 2023-07-06
Anticipated expiration: 2040-04-01
Also published as: CN110506930A; AU2020314346B2; AU2020314346A1; WO2021008172A1; CN110506930B

Abstract

Disclosed are a high-stability starch-based Pickering emulsion and a preparation method therefor. The preparation method comprises: first formulating a starch raw material into a starch slurry with a dry basis mass fraction of 5% to 20%, gelatinizing the starch slurry in a boiling water bath, then cooling same, adding excessive ethanol dropwise thereto, then carrying out centrifugal classification to obtain a precipitate, drying the precipitate to obtain a V-shaped crystalline starch; fully mixing molten fatty acids with the V-shaped crystalline starch, then continuously stirring same, and carrying out forced air drying to obtain starch-lipid composite particles; formulating the starch-lipid composite particles into a suspension aqueous solution, mixing the suspension aqueous solution with liquid fat, and shearing same at a high speed to obtain a high-stability starch-based Pickering emulsion. The emulsification index of the emulsion can reach 100%, and emulsion droplets of the emulsion are uniformly distributed, with the average particle size thereof being 10.13 to 25.20 μm, and the emulsion does not become layered within three months of storage. The preparation method has the characteristics of having a simple process, rich raw material sources, being environmentally friendly, etc., and can be widely applied to the fields of food, cosmetics, chemical industry, medicine, etc.

Description

STARCH-BASED HIGHLY STABLE PICKERING EMULSION AND PREPARATION METHOD THEREOF

FIELD OF THE INVENTION The present invention, belonging to the field of food industry, relates to a lipid complexed V-type crystalline starch as well as an environmentally friendly preparation method using a new hydrophobically modified starch as a Pickering emulsifier, wherein the method involves a lipid complexed "green" hydrophobically modified starch, thereby obtaining a new food-grade amphiphilic Pickering emulsifier. BACKGROUND OF THE INVENTION Pickering emulsion is a new emulsion that uses solid particles adsorbed at the oil-water interface instead of surfactants as a stabilizer, having simple preparation process and excellent stability. With people's increasing consumption, the market demand for products with labels such as "environmentally friendly and green" is increasing. The Pickering emulsion stabilized by bio-based solid particles has gradually attracted people's attention, and has huge market potential in food, cosmetics, chemicals, materials, medicines, and other industries. The stability of the Pickering emulsion mainly depends on the particle size and surface wettability of the solid particles. The solid particles with amphiphilicity and a small particle size can uniformly cover the two-phase interface to form a dense film, which results in the formation of steric hindrance, thereby resisting Ostwald maturation and dispersed-phase coalescence. The formed emulsion is usually very stable and can be stored for months or even years. Starch, as a kind of resource-rich and green natural biomacromolecular material, can be used as the raw material of the bio-based Pickering emulsifier. Natural starch has strong hydrophilicity and a large particle size, and is difficult to firmly adsorb on the two-phase interface, which limits its application in Pickering emulsion. Therefore, physical or chemical methods are often used to change the properties of natural starch particles to control the particle size and surface properties, so as to stabilize the emulsion system. At present, the main modification methods focus on hydrophobically modified starch through octenyl succinic anhydride (OSA). For example, in a method for preparing a starch-based Pickering emulsion gel as disclosed in Chinese invention patent application No. 2018105557772, first octenyl succinic anhydride was used to esterify small-sized starch particles with an average particle size of 1-5 m to obtain modified small-sized starch particles with a degree of substitution of 0.028-0.100; then the modified small-sized starch particles were uniformly dispersed in distilled water with a solid-liquid mass fraction of 1% to 5%, and continuously stirred for 6-12 h to get fully hydrated to form a suspension of starch particles; and finally the obtained starch particle suspension was mixed with liquid oil, and the starch-based Pickering emulsion gel could be obtained after high-speed shearing. The starch-based Pickering emulsion gel prepared by the method of the present invention is a physical gel that neither changes the chemical properties of the oil phase nor produces trans fatty acids. It can be used to produce functional oils, and can also be used as a carrier of fat-soluble pigments and flavor substances in cosmetics, daily necessities and other fields. The Pickering emulsion was prepared with natural starch, OSA-modified starch and heat-treated starch as an emulsifier, indicating by the results that the OSA-modified starch exhibited the best storage stability with a storage period reaching more than two years (Timgren et al., 2013, Food Science & Nutrition, 1 (2), 157-171). The comparison between OSA-modified rice and OSA-modified quinoa starch particles showed that the Pickering emulsion prepared with the OSA-modified quinoa starch as an emulsifier had storage stability and a smaller droplet size (Marefati et al., 2017, Food Hydrocolloids, 63, 309-320). When the starch concentration was 4%, the oil-phase volume fraction was 50%, and the emulsion pH was 6-7, the Pickering emulsion stabilized by the OSA-modified rice starch had the best emulsion effect (Song et al., 2015, Food Hydrocolloids, 45, 256-263). However, due to the potential harm to human health caused by excessive addition of chemicals, the US Food and Drug Administration (FDA) and National Standard (GB) 28303-2012 limit the maximum amount of OSA added to the OSA-modified starch for food production to 3%, and the maximum degree of substitution to 0.02, which limit the application of this product in the food and medical fields. CONTENTS OF THE INVENTION The present invention seeks to provide an emulsion with simple process, abundant raw materials and environmental protection that uses a new hydrophobically modified starch as a Pickering emulsifier, and a method for preparing the emulsion. The resulting Pickering emulsion stabilized by starch-lipid composite particles has an emulsification index reaching 100% and uniformly distributed droplets with an average particle size of 10.13-25.20 m, and can be stored for three months without stratification, which could be widely used in food, cosmetics, chemicals, medicines, and other fields. In the present invention, first the starch raw material is fully gelatinized in a boiling water bath to get the starch molecules fully extended, excessive absolute ethanol is added to form a V-type crystalline starch-ethanol single helix structure, and the ethanol is removed by blast drying to obtain a V-type crystalline starch; then the V-type crystalline starch is blended with a molten fatty acid to form V-type crystalline starch-fatty acid composite particles, so as to achieve the

"green" hydrophobic modification of the V-type crystalline starch; and finally the V-type crystalline

starch-fatty acid composite particles are applied to the Pickering emulsion to obtain a highly stable Pickering emulsion. The present invention relates to the following: A method for preparing a starch-based highly stable Pickering emulsion is provided, comprising the following steps and process conditions: (1) preparing starch raw materials into a starch slurry with a dry basis mass fraction of 5% to %, then gelatinizing in a boiling water bath for 1-2 h while stirring, cooling to 30°C to 50°C, then adding excessive absolute ethanol dropwise while continuous stirring, then centrifuging to obtain a precipitate, and then blast-drying the precipitate to obtain a V-type crystalline starch; (2) melting a fatty acid, and continuously stirring for 1-2 h to form the fluid fatty acid; (3) mixing the fluid fatty acid obtained in step (2) fully with the V-type crystalline starch obtained in step (1), then continuously stirring for 1-2 h, and then blast-drying to obtain starch lipid composite particles; and (4) preparing the starch-lipid composite particles obtained in step (3) into a suspension aqueous solution with a dry basis mass fraction of 2% to 6%, then mixing the suspension aqueous solution with liquid oil, and then shearing at a high speed to produce a starch-based highly stable Pickering emulsion. In one aspect, in step (1), the starch raw material is corn starch, potato starch or tapioca starch; the dry basis mass fraction of the starch slurry is 5% to 15%; the time for gelatinizing in a boiling water bath is 1-2 h; and the cooling temperature is 30°C to 50°C.

In another aspect, in step (1), in terms of volume fraction, the amount of the added starch slurry is 1 part, and the amount of the added absolute ethanol is 2-5 parts; the blast-drying temperature is 40°C to 60°C, and the drying time is 12-24 h.

In another aspect, in step (2), the fatty acid is lauric acid, palmitic acid, and stearic acid; the melting temperature is 55C to 75C; and the stirring method is magnetic stirring or mechanical

stirring. In another aspect, in step (3), in terms of volume fraction, the amount of the fluid fatty acid obtained in step (2) is 1-3 parts, and the amount of the V-type crystalline starch obtained in step (1) is 5-10 parts; and the mixing method is direct mixing or atomizing mixing. In another aspect, in step (3), the blast-drying temperature is 40'C to 60'C, and the drying

time is 12-24 h. In another aspect, in step (4), in terms of dry basis mass fraction, the amount of the starch-lipid composite particles in the suspension aqueous solution is 2-6 parts, and the amount of distilled water is 100 parts. In another aspect, in step (4), in terms of volume fraction, in the mixture of the suspension aqueous solution and the liquid oil, the amount of the suspension aqueous solution is 30-60 parts, and the amount of the liquid oil is 70-40 parts; and the liquid oil is soybean oil, corn oil or palm oil. In another aspect, in step (4), the rotational speed of the high-speed shearing is 5000-25000 rpm, and the time of the high-speed shearing is 1-5 min. The starch-based highly stable Pickering emulsion prepared by the above method has an emulsification index reaching 100% and uniformly distributed droplets with an average particle size of 10.13-25.20 [m, and can be stored for three months without stratification. The present invention uses starch and fatty acids from different sources as raw materials, and introduces fatty acid molecules into the V-type crystalline starch to form the starch-lipid composite particles to improve the hydrophobicity of starch particles, thereby obtaining a new food-grade amphiphilic starch-based Pickering emulsifier, which can be used without restriction in the fields of food and medicine. The Pickering emulsion stabilized by the starch-lipid composite particles obtained in the present invention has an emulsification index reaching 100% and uniformly distributed droplets with an average particle size of 10.13-25.20 [m, and can be stored for three months without stratification, widely used in food, cosmetics, chemicals, medicines, and other fields. The present invention has the following advantages compared with the prior art: 1) The fatty acid used in the present invention is a food-grade raw material, and has no restriction on the maximum addition amount in the food field; and the starch-lipid composite particles can be adjusted in hydrophilicity and hydrophobicity according to the type of fatty acid, chain length, compounding rate and the like, and is more widely used in the food field than the OSA starch with the maximum OSA addition amount of 3%. 2) The present invention, different from the traditional preparation of the OSA-modified starch, is a method of physically modified starch, wherein the fatty acid molecules are physically mixed with the V-type crystalline starch, so that the fatty acid molecules can enter the single helix cavity of the V-type crystalline starch to form a V-type starch-lipid composite particles, thus changing the hydrophilicity and hydrophobicity of the starch. Compared with chemically modified starch such as the OSA-modified starch, the modification process of the present invention does not involve the excessive use of organic and alkaline reagents, and is thus simpler and greener; the source of starch raw materials is more abundant, not limited to starch particles with a small particle size, and thereby a starch-based Pickering emulsifier with excellent emulsification performance can be obtained. 3) In the method of the present invention on the lipid complexed "green" hydrophobically-modified V-type crystalline starch, absolute ethanol is added dropwise to the gelatinized starch paste to obtain a V-type crystalline starch-ethanol single helix structure, and then ethanol is removed by drying to obtain a V-type crystalline starch; then the molten fatty acid is compounded with the V-type crystalline starch to form starch-lipid composite particles with improved hydrophobicity, thereby obtaining a new food-grade amphiphilic starch-based Pickering emulsifier. 4) The Pickering emulsion stabilized by the starch-lipid composite particles obtained in the present invention has an emulsification index reaching 100% and uniformly distributed droplets with an average particle size of 10.13-25.20 [m, and can be stored for three months without stratification, widely used in food, cosmetics, chemicals, medicines, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an appearance photo of a Pickering emulsion stabilized by a V-type crystalline starch prepared in a comparative example. Fig. 2 is a micrograph of the Pickering emulsion stabilized by the V-type crystalline starch prepared in the comparative example. Fig. 3 shows the particle size distribution of the Pickering emulsion stabilized by the V-type crystalline starch prepared in the comparative example. Fig. 4 is an appearance photo of a Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 1. Fig. 5 is a micrograph of the Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 1. Fig. 6 shows the particle size distribution of the Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 1. Fig. 7 is an appearance photo of a Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 2. Fig. 8 is a micrograph of the Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 2. Fig. 9 shows the particle size distribution of the Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 2. Fig. 10 is an appearance photo of a Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 3.

Fig. 11 is a micrograph of the Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 3. Fig. 12 shows the particle size distribution of the Pickering emulsion stabilized by the starch-lipid composite particles prepared in Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS In order to get better understood, the present invention will be further described in conjunction with drawings and examples, but the scope of protection of the present invention is not limited thereto. The method for testing the Pickering emulsion in the examples is as follows: Amphiphilicity determination of Pickering emulsifier: The amphiphilicity of the Pickering emulsifier is characterized by the three-phase contact angle 0 of the Pickering emulsifier at the oil-water interface. When 0 is less than 900, the Pickering emulsifier is hydrophilic; when 0 is close to 90°, the Pickering emulsifier is amphiphilic, and has the largest adsorption energy at the oil-water interface and the best emulsifying effect; and when 0 is greater than 90°, the Pickering emulsifier exhibits hydrophobicity. The test steps are as follows: Making Pickering emulsifier powder into a tablet (with a thickness of 2 mm and a diameter of 13 mm) by a tablet press, and then immersing the tablet in the soybean-oil sample stage of an OCA 20 device; using a high-precision syringe system to drop a water droplet of 5 L on the surface of the tablet, then using a high-speed camera mounted on the OCA 20 device to record the evolution of the droplet shape at a rate of 10 frames per second, and then automatically fitting the profile data of the droplet into the LaPlace-Young equation to determine the contact angle of particles. Appearance and storage stability test of emulsion: Pipetting 10 mL of the prepared Pickering emulsion into a serum bottle and storing at room temperature, and observing the appearance of the emulsion and taking electronic photos within the storage period of 3 months. Determination of emulsification index: The emulsification index (EI) is an index used for evaluating the emulsifying ability of an emulsifier and reflecting the emulsifying effect of the same. The higher the El value is, the stronger the emulsifying ability and the better the emulsifying effect will be. Pipetting 10 mL of the prepared Pickering emulsion into a serum bottle, then placing the serum bottle at room temperature for 2 h, then respectively measuring the height of the emulsified layer and the total height of the emulsion, and then calculating according to the following formula: Emulsification index (El, %)= (HE/HT) X 100 where HE is the height of the emulsified layer (mm), and HT is the total height of the emulsion

(mm). Microscopic observation of emulsion droplet: Dropping a droplet of the prepared Pickering emulsion on a glass slide and covering the droplet with a cover glass, and then placing the glass on a loading stage to observe the shape of the emulsion droplet with an optical microscope and take a micrograph. Particle size test of emulsion droplet: Adding the prepared Pickering emulsion dropwise to a laser particle-size analyzer for analysis, and then stirring the sample at a rotational speed of 2500 r/min to make it dispersed uniformly; the refractive index of water as a dispersant is set to 1.33, and the refractive index and absorptivity of starch particles are 1.52 and 0.01, respectively. Comparative example A method for preparing a Pickering emulsion stabilized by V-type crystalline starch was provided, characterized in that the method comprised the following steps and process conditions: (1) preparing corn starch into a starch slurry with a dry basis mass fraction of 5%, then gelatinizing in a boiling water bath for 2 h while stirring, then cooling to 30°C, then adding 3-time volume fraction of absolute ethanol dropwise while continuous stirring, then centrifuging to obtain a precipitate, and then blast-drying the precipitate at 60°C for 12 h to obtain a V-type

crystalline starch; and (2) preparing the V-type crystalline starch obtained in step (1) into a suspension aqueous solution with a dry basis mass fraction of 3%, then mixing the suspension aqueous solution with soybean oil according to a water-oil volume fraction of 40%, and then shearing at a high rotational speed of 20000 rpm for 2 min to produce the corresponding Pickering emulsion. The obtained V-type crystalline starch was tested to have a contact angle of 32, indicating that it had strong hydrophilicity. The Pickering emulsion of the V-type crystalline starch prepared in step (2) had an emulsification index of 0%; the obvious oil-water stratification phenomenon could be seen in the appearance photo of the emulsion (Fig. 1); according to the microscopic observation of the emulsion, there were emulsion droplets with an ultra-large particle size in the emulsion (Fig. 2); according to the particle size test results, the average particle size of these emulsion droplets was 91.31 m (Fig. 3), which was caused by the aggregation of emulsion droplets due to the instability of the emulsion system, indicating that the V-type crystalline starch uncompounded with fatty acids had insufficient emulsification performance and was unsuitable for the preparation of Pickering emulsion. Example 1 A method for preparing a starch-based highly stable Pickering emulsion was provided, characterized in that the method comprised the following steps and process conditions:

(1) preparing corn starch into a starch slurry with a dry basis mass fraction of 5%, then gelatinizing in a boiling water bath for 2 h while stirring, then cooling to 30°C, then adding 3-time volume fraction of absolute ethanol dropwise while continuous stirring, then centrifuging to obtain a precipitate, and then blast-drying the precipitate at 60°C for 12 h to obtain a V-type

crystalline starch; (2) melting lauric acid at 60°C, and continuously stirring for 1 h to form the fluid lauric acid;

(3) mixing 1 part of the fluid lauric acid obtained in step (2) fully with 10 parts of the V-type crystalline starch obtained in step (1), then continuously stirring for 1 h, and then blast-drying at °C for 24 h to obtain starch-lauric acid composite particles; and

(4) preparing the starch-lauric acid composite particles obtained in step (3) into a suspension aqueous solution with a dry basis mass fraction of 3%, then mixing the suspension aqueous solution with soybean oil according to a water-oil volume fraction of 40%, and then shearing at a high rotational speed of 20000 rpm for 2 min to produce the corresponding Pickering emulsion. The obtained starch-lauric acid composite particles were tested to have a contact angle of 94.6°, indicating that they were amphiphilic. The Pickering emulsion of the starch-lauric acid composite particles prepared in step (4) had an emulsification index of 100%; there was no oil-water stratification phenomenon found in the appearance photo of the emulsion (Fig. 4); according to the microscopic observation of the emulsion, emulsion droplets were uniformly distributed in the emulsion, and there was no emulsion droplet with a large particle size in the emulsion (Fig. 5); according to the particle size test results, the average particle size of these emulsion droplets was 10.13 m (Fig. 6); and there was no oil-water stratification phenomenon in the emulsion after three months of storage. Compared with the test results of the comparative example (Figs. 1-3), the test results of Example 1 can show that the emulsification performance of the starch-lauric acid composite particles was excellent, the introduction of lauric acid significantly improved the amphiphilicity of the V-type crystalline starch, and the Pickering emulsion thus obtained was highly stable. Compared with the invention patent No. 2018105557772, the method of the present invention was a method of physically modified starch, wherein the fatty acid molecules were physically mixed with the V-type crystalline starch, so that the fatty acid molecules could enter the single helix cavity of the V-type crystalline starch to form a V-type starch-lipid composite particles, thus changing the hydrophilicity and hydrophobicity of the starch (this could be proved by the contact angle data). Compared with chemically modified starch such as OSA-modified starch, the modification process of the present invention did not involve the excessive use of organic and alkaline reagents, and was thus simpler and greener; the source of starch raw materials was more abundant, not limited to starch particles with a small particle size, and thereby a starch-based Pickering emulsifier with excellent emulsification performance could be obtained. More importantly, the fatty acid used in the present invention was a food-grade raw material, and had no restriction on the maximum addition amount in the food field; and the starch-lipid composite particles could be adjusted in hydrophilicity and hydrophobicity according to the type of fatty acid, chain length, compounding rate, and the like, and was more widely used in the food field than the OSA starch with the maximum OSA addition amount of 3%. The Pickering emulsion obtained in this example had a uniform particle size distribution with the average particle size of the emulsion droplets at 10.13 m (Fig. 5), which was smaller than the average particle size of the traditional Pickering emulsion (50-270 mi, Timgren et al., 2013, Food Science & Nutrition, 1(2), 157-171; 30.6-33.4 kmi, Marefati et al., 2017, Food Hydrocolloids, 63, 309-320). In addition, the Pickering emulsion obtained in this example had excellent stability, and had no oil-water stratification phenomenon after three months of storage, thus especially suitable for applications in the cosmetics field requiring high emulsion stability or in the food field requiring long emulsion shelf life. Example 2 A method for preparing a starch-based highly stable Pickering emulsion was provided, characterized in that the method comprised the following steps and process conditions: (1) preparing potato starch into a starch slurry with a dry basis mass fraction of 10%, then gelatinizing in a boiling water bath for 1 h while stirring, then cooling to 30°C, then adding 2-time volume fraction of absolute ethanol dropwise while continuous stirring, then centrifuging to obtain a precipitate, and then blast-drying the precipitate at 60°C for 12 h to obtain a V-type crystalline starch; (2) melting palmitic acid at 65C, and continuously stirring for 2 h to form the fluid palmitic acid; (3) mixing 1 part of the fluid palmitic acid obtained in step (2) fully with 5 parts of the V-type crystalline starch obtained in step (1), then continuously stirring for 1 h, and then blast-drying at 50°C for 24 h to obtain starch-palmitic acid composite particles; and (4) preparing the starch-palmitic acid composite particles obtained in step (3) into a suspension aqueous solution with a dry basis mass fraction of 3%, then mixing the suspension aqueous solution with corn oil according to a water-oil volume fraction of 50%, and then shearing at a high rotational speed of 15000 rpm for 1 min to produce the corresponding Pickering emulsion. The obtained starch-palmitic acid composite particles were tested to have a contact angle of

96.5, indicating that they were amphiphilic. The Pickering emulsion of the starch-palmitic acid composite particles prepared in step (4) had an emulsification index of 100%; there was no oil-water stratification phenomenon found in the appearance photo of the emulsion (Fig. 7); according to the microscopic observation of the emulsion, emulsion droplets were uniformly distributed in the emulsion, and there was no emulsion droplet with a large particle size in the emulsion (Fig. 8); according to the particle size test results, the average particle size of these emulsion droplets was 13.62 m (Fig. 9); and there was no oil-water stratification phenomenon in the emulsion after three months of storage. Compared with the test results of the comparative example (Figs. 1-3), the test results of Example 2 can show that the emulsification performance of the starch-palmitic acid composite particles was excellent, the introduction of palmitic acid significantly improved the amphiphilicity of the V-type crystalline starch, and the Pickering emulsion thus obtained was highly stable. Example 3 A method for preparing a starch-based highly stable Pickering emulsion was provided, characterized in that the method comprised the following steps and process conditions: (1) preparing tapioca starch into a starch slurry with a dry basis mass fraction of 15%, then gelatinizing in a boiling water bath for 2 h while stirring, then cooling to 30°C, then adding 4-time volume fraction of absolute ethanol dropwise while continuous stirring, then centrifuging to obtain a precipitate, and then blast-drying the precipitate at 60°C for 12 h to obtain a V-type

crystalline starch; (2) melting stearic acid at 70°C, and continuously stirring for 1 h to form the fluid stearic

acid; (3) mixing 2 part of the fluid stearic acid obtained in step (2) fully with 9 parts of the V-type crystalline starch obtained in step (1), then continuously stirring for 1 h, and then blast-drying at °C for 24 h to obtain starch-stearic acid composite particles; and

(4) preparing the starch-stearic acid composite particles obtained in step (3) into a suspension aqueous solution with a dry basis mass fraction of 5%, then mixing the suspension aqueous solution with palm oil according to a water-oil volume fraction of 50%, and then shearing at a rotational speed of 20000 rpm for 1 min to produce the corresponding Pickering emulsion. The obtained starch-stearic acid composite particles were tested to have a contact angle of 99.5°, indicating that they were amphiphilic. The Pickering emulsion of the starch-stearic acid composite particles prepared in step (4) had an emulsification index of 100%; there was no oil-water stratification phenomenon found in the appearance photo of the emulsion (Fig. 10); according to the microscopic observation of the emulsion, emulsion droplets were uniformly distributed in the emulsion, and there was no emulsion droplet with a large particle size in the emulsion (Fig. 11); according to the particle size test results, the average particle size of these emulsion droplets was 25.20 m (Fig. 12); and there was no oil-water stratification phenomenon in the emulsion after three months of storage. Compared with the test results of the comparative example (Figs. 1-3), the test results of Example 3 can show that the emulsification performance of the starch-stearic acid composite particles was excellent, the introduction of stearic acid significantly improved the amphiphilicity of the V-type crystalline starch, and the Pickering emulsion thus obtained was highly stable. The present invention is not limited to the above examples, and any other alterations, modifications, replacements, combinations, and simplifications made without departing from the spirit and principle of the present invention should all be equivalent substitutions and included in the scope of protection of the present invention. It will be understood that the terms "comprise" and "include" and any of their derivatives (e.g. comprises, comprising, includes, including) as used in this specification, and the claims that follow, is to be taken to be inclusive of features to which the term refers, and is not meant to exclude the presence of any additional features unless otherwise stated. Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such prior art forms part of the common general knowledge.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method for preparing a starch-based highly stable Pickering emulsion, wherein the method comprises the following steps and process conditions: (1) preparing starch raw materials into a starch slurry with a dry basis mass fraction of 5% to %, then gelatinizing in a boiling water bath for 1-2 h while stirring, then cooling to 30°C to 50°C, then adding excessive absolute ethanol dropwise while continuous stirring, then centrifuging to obtain a precipitate, and then blast-drying the precipitate to obtain a V-type crystalline starch; (2) melting a fatty acid, and continuously stirring for 1-2 h to form the fluid fatty acid; (3) mixing the fluid fatty acid obtained in step (2) fully with the V-type crystalline starch obtained in step (1), then continuously stirring for 1-2 h, and then blast-drying to obtain starch lipid composite particles; and (4) preparing the starch-lipid composite particles obtained in step (3) into a suspension aqueous solution with a dry basis mass fraction of 2% to 6%, then mixing the suspension aqueous solution with liquid oil, and then shearing at a high speed to produce a starch-based highly stable Pickering emulsion.
2. The preparation method according to claim 1, wherein: in step (1), the starch raw material is corn starch, potato starch or tapioca starch; the dry basis mass fraction of the starch slurry is 5% to 15%; the time for gelatinizing in a boiling water bath is 1-2 h; and the cooling temperature is °C to 50°C.
3. The preparation method according to claim 1 or claim 2, wherein: in step (1), in terms of volume fraction, the amount of the added starch slurry is 1 part, and the amount of the added absolute ethanol is 2-5 parts; the blast-drying temperature is 40°C to 60°C, and the drying time is

12-24 h.
4. The preparation method according to any one of claims 1-3, wherein: in step (2), the fatty acid is lauric acid, palmitic acid and stearic acid; the melting temperature is 55C to 75C; and the

stirring method is magnetic stirring or mechanical stirring.
5. The preparation method according to any one of claims 1-4, wherein: in step (3), in terms of volume fraction, the amount of the fluid fatty acid obtained in step (2) is 1-3 parts, and the amount of the V-type crystalline starch obtained in step (1) is 5-10 parts; and the mixing method is direct mixing or atomizing mixing.
6. The preparation method according to any one of claims 1-5, wherein: in step (3), the blast drying temperature is 40°C to 60°C, and the drying time is 12-24 h.
7. The preparation method according to any one of claims 1-6, wherein: in step (4), in terms of dry basis mass fraction, the amount of the starch-lipid composite particles in the suspension aqueous solution is 2-6 parts, and the amount of distilled water is 100 parts.
8. The preparation method according to any one of claims 1-7, wherein: in step (4), in terms of volume fraction, in the mixture of the suspension aqueous solution and the liquid oil, the amount of the suspension aqueous solution is 30-60 parts, and the amount of the liquid oil is 70-40 parts; and the liquid oil is soybean oil, corn oil or palm oil.
9. The preparation method according to any one of claims 1-8, wherein: in step (4), the rotational speed of the high-speed shearing is 5000-25000 rpm, and the time of the high-speed shearing is 1-5 min.
10. A starch-based highly stable Pickering emulsion, wherein: it is prepared by the method according to any one of claims 1-9, has an emulsification index reaching 100% and uniformly distributed droplets with an average particle size of 10.13-25.20 [m, and can be stored for three months without stratification.

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