阅读说明：本技术 一种玉米肽-微晶甲壳素复合物及其双重皮克林乳液制备方法 (Corn peptide-microcrystalline chitin compound and preparation method of double pickering emulsion thereof ) 是由 袁杨 雷蕾 于 2021-06-17 设计创作，主要内容包括：本发明公开了一种玉米肽-微晶甲壳素复合物及其双重皮克林乳液制备方法。本发明以玉米醇溶蛋白为原料,采用酶水解制备玉米醇溶蛋白水解物；将微晶甲壳素加入水中并均质,获得微晶甲壳素母液；向微晶甲壳素母液加水适当稀释,并调节pH值为4.8～5.5；然后加入冻干后的玉米醇溶蛋白水解物颗粒,使得微晶甲壳素与玉米醇溶蛋白水解物的质量浓度比为1：0.5～4；调节pH值为4.8～5.5；搅拌一段时间,制得所述玉米肽-微晶甲壳素复合物。该复合物可用于制备玉米肽-微晶甲壳素稳定的双重皮克林乳液,该乳液稳定性好,多内腔式结构可以用于食品营养物质的包埋。本发明拓宽了玉米肽基在食品领域的应用以及传统皮克林乳液的类型。(The invention discloses a corn peptide-microcrystalline chitin compound and a preparation method of a double pickering emulsion thereof. The invention takes zein as raw material, adopts enzyme hydrolysis to prepare zein hydrolysate; adding microcrystalline chitin into water and homogenizing to obtain microcrystalline chitin mother liquor; adding water into the microcrystalline chitin mother liquor for proper dilution, and adjusting the pH value to 4.8-5.5; then adding the freeze-dried zein hydrolysate particles to ensure that the mass concentration ratio of the microcrystalline chitin to the zein hydrolysate is 1: 0.5 to 4; adjusting the pH value to 4.8-5.5; stirring for a period of time to obtain the corn peptide-microcrystalline chitin compound. The compound can be used for preparing stable double pickering emulsion of corn peptide-microcrystalline chitin, the emulsion has good stability, and the multi-cavity structure can be used for embedding food nutrient substances. The invention widens the application of the corn peptide base in the food field and the type of the traditional pickering emulsion.)

1. The preparation method of the corn peptide-microcrystalline chitin compound is characterized by comprising the following steps of:

(1) using zein as a raw material, preparing zein hydrolysate by adopting enzyme hydrolysis, and preparing zein hydrolysate particles by freeze-drying treatment;

(2) dissolving chitin in hydrochloric acid to prepare microcrystalline chitin; then adding microcrystalline chitin into water and homogenizing to obtain microcrystalline chitin mother liquor;

(3) adding water into the microcrystalline chitin mother liquor for proper dilution, and adjusting the pH value to 4.8-5.5; then adding the freeze-dried zein hydrolysate particles to ensure that the mass concentration ratio of the microcrystalline chitin to the zein hydrolysate is 1: 0.5 to 4; adjusting the pH value of the solution to 4.8-5.5; stirring the solution for a period of time, and fully hydrating to obtain the corn peptide-microcrystalline chitin compound.

2. The method for preparing the corn peptide-microcrystalline chitin complex according to claim 1, wherein the specific steps of step (1) are as follows: fully dissolving zein aqueous solution at 50 ℃ under the condition that the pH value is more than 11, and adding enzyme for hydrolysis, wherein the mass ratio of the enzyme to a substrate is 2: 100; in the hydrolysis process, NaOH solution is used to maintain the pH of the solution at 9.0-9.3; adjusting the pH of the solution to 7.0 by using HCl when the hydrolysis degree of the zein reaches 4.5-5.5%, and inactivating the zein at 95-100 ℃ for 8-10 minutes; then centrifuging, dialyzing, and finally freeze-drying to obtain zein hydrolysate.

3. The method for preparing the zein-microcrystalline chitin composite of claim 2, wherein the concentration of the zein aqueous solution is 2.8-3.2% w/v;

the enzyme is Alcalase alkaline protease;

in the hydrolysis process, 1mol/L NaOH solution is used for maintaining the pH value of the solution at 9.0-9.3; after the hydrolysis degree of zein reaches 4.5-5.5%, adjusting the pH of the solution to 7.0 by using 1mol/L hydrochloric acid;

and after inactivation, centrifuging at 25 ℃ and 8000-10000 r/min for 20-30 min, sucking supernatant, putting the supernatant into a dialysis bag of 100Da, and dialyzing and desalting for 24h in deionized water.

4. The method for preparing the compound of corn peptide-microcrystalline chitin according to claim 1, wherein the specific steps of step (2) are as follows: dissolving weighed chitin in hydrochloric acid, carrying out boiling water bath for 1.5-2 h, then carrying out centrifugal treatment for 20min at 6000r/min, washing with water, centrifuging again, taking out precipitate, adding the precipitate into water with the same volume as the initial hydrochloric acid, and carrying out high-pressure homogenization for 5min at 30MPa to obtain microcrystalline chitin mother liquor.

5. The method for preparing the corn peptide-microcrystalline chitin complex according to claim 1, wherein the concentration of the mother solution of microcrystalline chitin in step (2) is 8-10 mg/mL.

6. The method for preparing the corn peptide-microcrystalline chitin complex according to claim 1, wherein the stirring time in step (3) is 2 h;

in the step (3), 1mol/L HCl and 1mol/L NaOH solution are used for adjusting the pH value.

7. A corn peptide-microcrystalline chitin complex made by the method of any one of claims 1-6.

8. A stable double pickering emulsion of a corn peptide-microcrystalline chitin compound is characterized by comprising the following preparation steps: the stable double pickering emulsion of the corn peptide-microcrystalline chitin compound is prepared by adding the corn peptide-microcrystalline chitin compound of claim 7 into an oil phase and homogenizing by a two-step shearing homogenization method.

9. The stabilized double pickering emulsion of corn peptide-microcrystalline chitin complex according to claim 8, wherein said oil phase is vegetable oil; the mass ratio of the oil phase in the system is 68-73%.

10. The stable double pickering emulsion of corn peptide-microcrystalline chitin complex according to claim 8, wherein said two-step shear homogenization method comprises: homogenizing for 25-35 s at 4800-5000 rpm to mix the two phases thoroughly, homogenizing for 55-70 s at 7800-8500 rpm to disperse the emulsion further into smaller emulsion droplets, and finally obtaining the stable double pickering emulsion of the corn peptide-microcrystalline chitin complex.

Technical Field

The invention belongs to the technical field of food, and particularly relates to a corn peptide-microcrystalline chitin compound and a preparation method of a double pickering emulsion thereof.

Background

Double emulsions are a simple multiple emulsion, the most common double emulsion being a water-oil-water (W/O/W) emulsion, which is an ideal delivery system for encapsulating hydrophobic and hydrophilic bioactive substances of different polarities due to the compartmentalization of its internal structure. Double emulsions are widely regarded in the food industry as a method of reducing the amount of fat in emulsified food products without affecting the texture of the mouth (e.g. chocolate) and for encapsulating and protecting water-soluble ingredients (e.g. nutrients, flavors, natural colors, and probiotics) and substances highly sensitive to the environment (pressure, temperature, light, and others) in food products, due to their potential applications in various fields of the food industry, cosmetics, pharmaceuticals, and materials synthesis. In addition, the pickering emulsion has obvious advantages in the aspects of stability, preparation simplicity and the like, and is a research hotspot in the field of food emulsion at present.

Zein Hydrolysate (ZH) is a natural amphiphilic polypeptide, also called corn peptide, and the zein hydrolysate is rich in hydrophobic amino acid, contains a large amount of proline, and has good water solubility, thereby not only solving the problem of difficult water solubility, but also having the physiological activities of resisting oxidation, preventing aging, reducing blood pressure and the like. Researches show that ZH has good amphiphilic property and shows self-assembly property, namely, ZH is very valuable as a delivery carrier in nutrition delivery.

Chitin (Chitin, CTI) is known as β - (1,4) -2-acetamido-2-deoxy-D-glucose, and is prepared by condensing N-acetamido glucose with β - (1,4) glycosidic bond. The nano-crystalline Cellulose (CNW) is obtained after hydrolysis, and has the characteristics of reproducibility, hydrophilicity, low thermal expansion coefficient, embellishment, large specific surface area and the like, so that the nano-crystalline cellulose becomes a functional nano-material with great development potential. In addition, the potential as an oil-in-water Pickering stabilizer is shown due to its unique properties (e.g., delayed lipid digestion) and successful application as building blocks for new biomaterial design.

At present, researchers at home and abroad can construct a compound by using corn peptide and other raw materials to stabilize emulsion: 2018, Raney horse and the like report that corn peptide-calcium phosphate is used as an emulsifier to construct a water-in-oil-in-water double pickering emulsion; related studies on the use of corn peptide-citrus fiber complexes to stabilize high internal phase emulsions and study their physical and frictional properties were reported by renqijun et al in 2019; wang Yonghui et al in 2020 reported the use of corn peptide as an emulsifier to improve the stabilization of soy protein isolate as an oil-in-water pickering emulsion. But there has been little research on the construction of complexes of corn peptide-nanofibers to stabilize dual (water-in-oil-in-water) pickering emulsions. In addition, because the molecular weight of the polypeptide is small, and the double emulsion drives the coalescence or diffusion of internal water drops to external water phase due to osmotic potential and chemical potential, the long-term good physical stability is difficult to realize, and the type of the pickering emulsion is traditionally single at present, so the development of the polypeptide and other nutrient substances is limited, and the application of the polypeptide and other nutrient substances in commercial food is influenced. By combining the current research situations at home and abroad, the literature and patent report of the stable dual (water-in-oil-in-water) pickering emulsion of the corn peptide-nanofiber composite are not found.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention aims to provide a preparation method of a corn peptide-microcrystalline chitin compound, namely a zein hydrolysate-microcrystalline chitin compound.

Another object of the present invention is to provide a stable double (water-in-oil-in-water) pickering emulsion of the corn peptide-microcrystalline chitin complex.

The reported preparation technology of double (water-in-oil-in-water) pickering emulsion stabilized by corn peptide and other substances is relatively insufficient, the diversified application development of polypeptide is limited, and the stability of the traditional emulsion is poor. The stable double (water-in-oil-in-water) pickering emulsion of the corn peptide-microcrystalline chitin compound provided by the invention has good stability, and the multi-cavity structure of the emulsion can be used for embedding food nutrient substances. The invention widens the application of the corn peptide base in the food field and the type of the traditional pickering emulsion.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a corn peptide-microcrystalline chitin compound comprises the following steps:

(1) using zein as a raw material, preparing Zein Hydrolysate (ZH) by adopting enzyme hydrolysis, and preparing zein hydrolysate particles by freeze-drying treatment;

(2) dissolving chitin in hydrochloric acid to prepare microcrystalline Chitin (CNW); then adding microcrystalline chitin into water and homogenizing to obtain microcrystalline chitin mother liquor;

(3) adding water into the microcrystalline chitin mother liquor for proper dilution, and adjusting the pH value to 4.8-5.5; then adding the freeze-dried zein hydrolysate particles to ensure that the mass concentration ratio of the microcrystalline chitin to the zein hydrolysate is 1: 0.5 to 4; adjusting the pH value of the solution to 4.8-5.5; stirring the solution for a period of time, and fully hydrating to obtain the corn peptide-microcrystalline chitin compound.

Further, the specific steps of the step (1) are as follows: fully dissolving zein (zein) aqueous solution at 50 ℃ under the condition that the pH value is more than 11, and adding enzyme for hydrolysis, wherein the mass ratio of the enzyme to a substrate (zein) is 2: 100; in the hydrolysis process, NaOH (sodium hydroxide) solution is used to maintain the pH of the solution at 9.0-9.3; adjusting the pH of the solution to 7.0 by using HCl (hydrochloric acid) when the hydrolysis degree of the zein reaches 4.5-5.5%, and inactivating the zein at the temperature of 95-100 ℃ for 8-10 minutes; then centrifuging, dialyzing, and finally freeze-drying to obtain zein hydrolysate particles. The lyophilized samples were stored at 4 ℃ until use.

Furthermore, the concentration of the zein water solution is 2.8-3.2% w/v.

Further, the enzyme is Alcalase alkaline protease.

Furthermore, in the hydrolysis process, 1mol/L NaOH solution is used for maintaining the pH value of the solution at 9.0-9.3; after the hydrolysis degree reaches 4.5-5.5%, the pH value of the solution is adjusted to 7.0 by using 1mol/L hydrochloric acid.

Further, after inactivation, centrifuging at 25 ℃ and 8000-10000 r/min for 20-30 min, sucking supernatant, putting the supernatant in a dialysis bag of 100Da, and dialyzing and desalting for 24h in deionized water.

Further, the specific steps of the step (2) are as follows: dissolving weighed chitin in hydrochloric acid, carrying out boiling water bath for 1.5-2 h, then carrying out centrifugal treatment for 20min at 6000r/min, washing with water, centrifuging again, taking out precipitate, adding the precipitate into water with the same volume as the initial hydrochloric acid, and carrying out high-pressure homogenization for 5min at 30MPa (300bar) to obtain microcrystalline chitin mother liquor. And (4) placing the homogenized CNW mother liquor into a refrigerator at 4 ℃ for storage for later use.

Further, the concentration of the hydrochloric acid is 3 mol/L.

Further, the concentration of the mother liquor of the microcrystalline chitin in the step (2) is 8-10 mg/mL.

Further, the stirring time in the step (3) is 2 hours. The solution is stirred for 2 hours, so that the microcrystalline chitin and the zein hydrolysate are fully reacted (namely fully hydrated).

Further, in the step (3), 1mol/L HCl and 1mol/L NaOH solution are used for adjusting the pH value.

Further, in the step (3), water is added into the microcrystalline chitin mother liquor to dilute the microcrystalline chitin mother liquor so that the mass concentration of the microcrystalline chitin is 0.5%.

A corn peptide-microcrystalline chitin compound prepared by the method.

A stable double pickering emulsion of a corn peptide-microcrystalline chitin compound comprises the following preparation steps: adding the corn peptide-microcrystalline chitin compound prepared by the method into an oil phase, and homogenizing by a two-step shearing homogenization method to prepare the stable double pickering emulsion of the corn peptide-microcrystalline chitin compound.

Further, the oil phase is preferably a vegetable oil (e.g., corn oil, etc.).

Furthermore, the mass ratio of the oil phase in the system (oil phase and the corn peptide-microcrystalline chitin complex) is 68-73%.

Further, the two-step shearing homogenization method specifically comprises the following steps: homogenizing for 25-35 s at 4800-5200 rpm to mix the two phases thoroughly, homogenizing for 55-70 s at 7800-8500 rpm to disperse the emulsion further into smaller emulsion droplets, and finally obtaining the stable double pickering emulsion (ZH-CNW double pickering emulsion) of the corn peptide-microcrystalline chitin complex.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) different from the previous reports, the invention firstly discloses that the zein hydrolysate and the microcrystalline chitin are utilized to construct the compound, the hydrolysis degree of the zein is 4.5-5.5%, and the zein is in a flocculation state in a pH5 solution.

(2) The invention utilizes zein hydrolysate and microcrystalline chitin to construct a compound to prepare the pickering emulsion with better viscoelasticity and stability.

(3) The pickering emulsion obtained by the invention has a layered double structure of water-in-oil-in-water.

(4) The composite pickering emulsion obtained by the invention is superior to the traditional single microcrystalline chitin emulsion and corn peptide emulsion.

(5) The embedding rate of the composite emulsion grease obtained by the invention is as high as 85-90%, which is superior to the traditional microcrystalline chitin emulsion.

Drawings

Fig. 1 is a turbidity and potential diagram of ZH-CNW composites prepared in examples 1 to 5 and CNW particles prepared in comparative example 1.

FIG. 2 is an optical microscope image and color appearance image of the ZH-CNW dual pickering emulsions prepared in examples 1-5 and the dual CNW pickering emulsion prepared in comparative example 1.

FIGS. 3-5 are rheological representations of ZH-CNW dual pickering emulsions prepared in examples 1-5 and CNW dual pickering emulsions prepared in comparative example 1, FIG. 3 is an amplitude strain scan; FIG. 4 is an amplitude frequency scan, and FIG. 5 is an apparent viscosity map; wherein: CNW0.5, CNW ZH 0.5:0.25, CNW ZH ═ 0.5:0.5, CNW, ZH 0.5:1.0, CNW, ZH 0.5:1.5, CNW, ZH is 0.5:2.0 represent, in order, the CNW double pickering emulsion prepared in comparative example 1 and the ZH-CNW double pickering emulsions prepared in examples 1 to 5.

FIG. 6 shows the oil and fat entrapment ratios of the ZH-CNW double pickering emulsions prepared in examples 1-5 and the CNW double pickering emulsion prepared in comparative example 1, wherein 0, 0.25, 0.5, 1.0, 1.5, and 2.0 represent the double CNW pickering emulsion prepared in comparative example 1 and the ZH-CNW double pickering emulsions prepared in examples 1-5, respectively.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto. The raw materials related to the invention can be directly purchased from the market. For process parameters not specifically noted, reference may be made to conventional techniques.

Example 1

(1) Preparation of microcrystalline Chitin (CNW):

preparation of 3mol/L hydrochloric acid, HCl H₂O is 1: 3, adding 75mL of concentrated hydrochloric acid into 225mL of water; weighing 3g of chitin, dissolving in hydrochloric acid, carrying out boiling water bath for 1.5h, then carrying out centrifugal treatment for 20min at 6000r/min, washing with water for 3 times, carrying out centrifugation again, taking out precipitate, adding the precipitate into water with the same volume as the initial hydrochloric acid, and carrying out high-pressure homogenization for 5min at 30MPa (300bar) to obtain 10mg/mL CNW mother liquor.

(2) Preparation of Zein Hydrolysate (ZH):

after the zein (zein) aqueous solution (3% w/v) was fully dissolved at 50 ℃ and pH > 11, Alcalase alkaline protease (from Novicat, China) was added for hydrolysis, enzyme: substrate 2:100 (mass ratio). The pH of the solution was maintained at 9.0 during the hydrolysis using a 1mol/L NaOH solution. When the degree of hydrolysis reached 5%, the solution was adjusted to pH 7.0 with 1mol/L HCl (hydrochloric acid) and left to inactivate at 95 ℃ for 8 minutes. Centrifuging at 25 deg.C and 10000r/min for 20min, sucking supernatant, placing in 100Da dialysis bag, dialyzing in deionized water for 24h to remove salt, lyophilizing to obtain zein hydrolysate granule, and storing lyophilized sample at 4 deg.C.

And (3) monitoring the hydrolysis degree of Zein in the enzymolysis process, and determining the proteolysis Degree (DH) by a pH-Stat method. According to the consumption of NaOH in the enzymolysis process, calculating the DH:

DH(％)＝B×N_b×α^-1×(M)^-1×(h_tot)^-1×100

wherein B is the consumption volume (mL) of sodium hydroxide; n is a radical of_bThe concentration of the sodium hydroxide is 1 mol/L; alpha is alpha^-1Is the average dissociation constant of alpha amino group at pH 9.0 and 50 deg.CNumber (1.01); h is_totThe total number of peptide bonds (9.2mmol/g) for zein.

(3) Preparation of zein hydrolysate-microcrystalline chitin (ZH-CNW) compound:

7.5mL of the CNW mother liquor (10mg/mL) obtained in step (1) was diluted to 5mg/mL (volume 15mL) with 7.5mL of distilled water, and the pH was adjusted to 5 with 1mol/L HCl and 1mol/L NaOH solutions. Adding 37.5mg of the freeze-dried ZH granules prepared in the step (2) to make the final mass concentration ratio (wt%) of CNW to ZH 0.5:0.25, and adjusting the final pH of the solution to 5; and then dispersing and stirring the solution for 2 hours to ensure full hydration to obtain a CNW-ZH compound solution.

(4) Preparing a zein hydrolysate-microcrystalline chitin double pickering emulsion:

weighing 4.5g of the CNW-ZH compound solution in the step (3), adding into a centrifuge tube, and adding 10.5g of corn oil, wherein the mass ratio of the oil phase in the system is 70%. Homogenizing by two-step shearing homogenizing method, homogenizing at 5000rpm for 30s to mix the two phases, homogenizing at 8000rpm for 1min to disperse the emulsion into smaller emulsion droplets, and finally obtaining ZH-CNW double pickering emulsion.

The potential and color appearance of the zein hydrolysate-microcrystalline chitin (ZH-CNW) composite prepared in this example is 29.93mV, which is positively charged, as shown in FIG. 1 (example 1). The solution was relatively clear and no flocculation occurred.

The color appearance and laser confocal microscope of the zein hydrolysate-microcrystalline chitin (ZH-CNW) double pickering emulsion prepared in this example are shown in fig. 2 (example 1), the emulsion appearance is milky white, and the particle size under the microscope is uniform and the dispersion is uniform. And shows the structure of a double pickering emulsion.

Example 2

(1) Preparation of microcrystalline Chitin (CNW): the preparation procedure was the same as in example 1, to obtain 10mg/mL of CNW mother liquor.

(2) Preparation of Zein Hydrolysate (ZH): the preparation procedure was the same as in example 1, and the lyophilized zein hydrolysate pellets were stored in a 4 ℃ freezer for further use.

(3) Preparation of zein hydrolysate-microcrystalline chitin (ZH-CNW) compound:

7.5mL of the CNW mother liquor (10mg/mL) obtained in step (1) was diluted to 5mg/mL (volume 15mL) with 7.5mL of distilled water, and the pH was adjusted to 5 with 1mol/L HCl and 1mol/L NaOH solutions. Adding 75mg of the freeze-dried ZH particles prepared in the step (2) to ensure that the final mass concentration ratio (wt%) of CNW to ZH is 0.5:0.5, and adjusting the final pH of the solution to 5; and then dispersing and stirring the solution for 2 hours to ensure full hydration to obtain a CNW-ZH compound solution.

(4) Preparing a zein hydrolysate-microcrystalline chitin double pickering emulsion:

weighing 4.5g of the CNW-ZH compound solution in the step (3), adding into a centrifuge tube, and adding 10.5g of corn oil, wherein the mass ratio of the oil phase in the system is 70%. Homogenizing by two-step shearing homogenizing method, homogenizing for 30s at 5000rmp to mix the two phases thoroughly, homogenizing at 8000rmp for 1min to disperse the emulsion into smaller emulsion droplets, and finally obtaining ZH-CNW double pickering emulsion.

The potential and color appearance of the zein hydrolysate-microcrystalline chitin (ZH-CNW) composite prepared in this example are 27.80mV, and are positively charged, as shown in FIG. 1 (example 2). The solution was relatively clear and no flocculation occurred.

The color appearance and laser confocal microscope of the zein hydrolysate-microcrystalline chitin (ZH-CNW) double pickering emulsion prepared in this example are shown in fig. 2 (example 2), the emulsion appearance is milky white, and the particle size under the microscope is uniform and the dispersion is uniform. And shows the structure of a double pickering emulsion.

Example 3

(1) Preparation of microcrystalline Chitin (CNW): the preparation procedure was the same as in example 1, to obtain 10mg/mL of CNW mother liquor.

(2) Preparation of Zein Hydrolysate (ZH): the preparation procedure was the same as in example 1, and the lyophilized zein hydrolysate pellets were stored in a 4 ℃ freezer for further use.

(3) Preparation of zein hydrolysate-microcrystalline chitin (ZH-CNW) compound:

7.5mL of the CNW mother liquor (10mg/mL) obtained in step (1) was diluted to 5mg/mL (volume 15mL) with 7.5mL of distilled water, and the pH was adjusted to 5 with 1mol/L HCl and 1mol/L NaOH solutions. Adding 150mg of the freeze-dried ZH particles prepared in the step (2) to make the final mass concentration ratio (wt%) of CNW to ZH 0.5:1.0, and adjusting the final pH of the solution to 5; and then dispersing and stirring the solution for 2 hours to ensure full hydration to obtain a CNW-ZH compound solution.

(4) Preparing a zein hydrolysate-microcrystalline chitin double pickering emulsion:

weighing 4.5g of the CNW-ZH compound solution in the step (3), adding into a centrifuge tube, and adding 10.5g of corn oil, wherein the mass ratio of the oil phase in the system is 70%. Homogenizing by two-step shearing homogenizing method, homogenizing at 5000rpm for 30s to mix the two phases, homogenizing at 8000rpm for 1min to disperse the emulsion into smaller emulsion droplets, and finally obtaining ZH-CNW double pickering emulsion.

The potential and color appearance of the zein hydrolysate-microcrystalline chitin (ZH-CNW) composite prepared in this example is 16.53mV, positively charged, and the solution slightly flocculated as shown in fig. 1 (example 3).

The color appearance and laser confocal microscope of the zein hydrolysate-microcrystalline chitin (ZH-CNW) double pickering emulsion prepared in this example are shown in fig. 2 (example 3), the emulsion appearance is milky white, and the particle size under the microscope is uniform and the dispersion is uniform. And shows the structure of a double pickering emulsion.

Example 4

(1) Preparation of microcrystalline Chitin (CNW): the preparation procedure was the same as in example 1, to obtain 10mg/mL of CNW mother liquor.

(2) Preparation of Zein Hydrolysate (ZH): the preparation procedure was the same as in example 1, and the lyophilized zein hydrolysate pellets were stored in a 4 ℃ freezer for further use.

(3) Preparation of zein hydrolysate-microcrystalline chitin (ZH-CNW) compound:

7.5mL of the CNW mother liquor (10mg/mL) obtained in step (1) was diluted to 5mg/mL (volume 15mL) with 7.5mL of distilled water, and the pH was adjusted to 5 with 1mol/L HCl and 1mol/L NaOH solutions. Adding 225mg of the lyophilized ZH particles prepared in the step (2) so that the final mass concentration ratio (wt%) of CNW to ZH is 0.5:1.5, and adjusting the final pH of the solution to 5; and then dispersing and stirring the solution for 2 hours to ensure full hydration to obtain a CNW-ZH compound solution.

(4) Preparing a zein hydrolysate-microcrystalline chitin double pickering emulsion:

weighing 4.5g of the CNW-ZH compound solution in the step (3), adding into a numbered centrifuge tube, and adding 10.5g of corn oil, wherein the mass ratio of the oil phase in the system is 70%. Homogenizing by two-step shearing homogenizing method, homogenizing at 5000rpm for 30s to mix the two phases, homogenizing at 8000rpm for 1min to disperse the emulsion into smaller emulsion droplets, and finally obtaining ZH-CNW double pickering emulsion.

The potential and color appearance of the zein hydrolysate-microcrystalline chitin (ZH-CNW) composite prepared in this example is 17.67mV, positively charged, and the solution slightly flocculated as shown in fig. 1 (example 4).

The color appearance and laser confocal microscope of the zein hydrolysate-microcrystalline chitin (ZH-CNW) double pickering emulsion prepared in this example are shown in fig. 2 (example 4), the emulsion appearance is milky white, the particle size under the microscope is not uniform, but the structure of the double pickering emulsion is still shown.

Example 5

(1) Preparation of microcrystalline Chitin (CNW): the preparation procedure was the same as in example 1, to obtain 10mg/mL of CNW mother liquor.

(2) Preparation of Zein Hydrolysate (ZH): the preparation procedure was the same as in example 1, and the lyophilized zein hydrolysate pellets were stored in a 4 ℃ freezer for further use.

(3) Preparation of zein hydrolysate-microcrystalline chitin (ZH-CNW) compound:

7.5mL of the CNW mother liquor (10mg/mL) obtained in step (1) was diluted to 5mg/mL (volume 15mL) with 7.5mL of distilled water, and the pH was adjusted to 5 with 1mol/L HCl and 1mol/L NaOH solutions. Adding 300mg of the freeze-dried ZH particles prepared in the step (2) to make the final mass concentration ratio (wt%) of CNW to ZH 0.5:2.0, and adjusting the final pH of the solution to 5; and then dispersing and stirring the solution for 2 hours to ensure full hydration to obtain a CNW-ZH compound solution.

(4) Preparing a zein hydrolysate-microcrystalline chitin double pickering emulsion:

weighing 4.5g of the CNW-ZH compound solution in the step (3), adding into a centrifuge tube, and adding 10.5g of corn oil, wherein the mass ratio of the oil phase in the system is 70%. Homogenizing by two-step shearing homogenizing method, homogenizing at 5000rpm for 30s to mix the two phases, homogenizing at 8000rpm for 1min to disperse the emulsion into smaller emulsion droplets, and finally obtaining ZH-CNW double pickering emulsion

The potential and color appearance of the zein hydrolysate-microcrystalline chitin (ZH-CNW) composite prepared in this example is 15.17mV, positively charged, and the solution is significantly flocculated, as shown in fig. 1 (example 5).

The color appearance and laser confocal microscope of the zein hydrolysate-microcrystalline chitin (ZH-CNW) double pickering emulsion prepared in this example are shown in fig. 2 (example 5), the emulsion appearance is milky white, and under the microscope, the particle size is not uniform, the dispersion is not uniform, but the structure of the double pickering emulsion is still shown.

Comparative example 1

(1) Preparation of microcrystalline Chitin (CNW):

CNW preparation procedure was the same as in example 1, and 10mg/mL of CNW mother liquor was prepared. Adding 7.5mL of distilled water into 7.5mL of CNW mother liquor (10mg/mL), diluting to 5mg/mL (volume 15mL), adjusting pH to 5 with 1mol/L HCl and 1mol/L NaOH solution, and dispersing and stirring for 2h to ensure full hydration to obtain a CNW particle solution.

(2) Preparing the double pickering emulsion of the microcrystalline chitin:

and (2) adding 4.5g of the CNW particle solution obtained in the step (1) into a centrifuge tube, and adding 10.5g of corn oil, wherein the mass ratio of the oil phase in the system is 70%. Homogenizing by two-step shearing homogenizing method, homogenizing at 5000rpm for 30s to mix the two phases thoroughly, homogenizing at 8000rpm for 1min to further homogenize and disperse the emulsion into smaller emulsion droplets, and finally obtaining the CNW double-pickering emulsion with pH of 5.

The potential and color appearance of the microcrystalline Chitin (CNW) complex prepared in this example is 34.62mV, positively charged, and the solution is clear and clear as shown in fig. 1 (comparative example 1).

The appearance of the microcrystalline Chitin (CNW) double pickering emulsion prepared in this example and a laser confocal microscope are shown in fig. 2 (comparative example 1), which shows that the particles are large and the dispersion is not uniform, but shows the structure of the double pickering emulsion.

And (3) determination:

(1) rheological characterization of zein hydrolysate-microcrystalline chitin double pickering emulsion:

the rheological properties of the emulsion were determined using oscillatory and frequency sweeps of an MCR92 rheometer and the apparent viscosity. Using a CP50-1 probe, 3mL of the ZH-CNW double pickering emulsion of examples 1-5 and the CNW double pickering emulsion of comparative example 1 were spread on a plate at room temperature. Amplitude frequency sweep selection for measuring storage modulus (G ') and loss modulus (G'), amplitude strain sweep selection for measuring storage modulus (G ') and loss modulus (G') in the range of 0.01-100Hz, and apparent viscosity selection for measuring storage modulus (G ') and loss modulus (G'), shear rate of 0.01-100s^-1The storage modulus (G ') and loss modulus (G'), and apparent viscosity of the sample were measured under the conditions described above. The test results are shown in FIGS. 3-5.

As shown in fig. 3, the elasticity modulus (G') and viscosity modulus (G ″) of ZH-CNW composite pickering emulsion of all samples are significantly higher than the CNW emulsion alone with increasing shear stress under amplitude strain sweep, indicating greater gel strength of the composite group. After the shear stress is increased continuously, the two curves are crossed, and the shear stress corresponding to the intersection point is called yield stress. At this point, the structure of the emulsion changes. As shown in FIG. 4, under the same stress under amplitude frequency scanning, except that the crossing point of the complex group and the blank group at high concentration causes structural damage, the G 'of the other complex groups is always larger than the G', which indicates that the complex group emulsion has better elastic colloid property. FIG. 5 shows a decrease in apparent viscosity as shear rate increases, indicating that the emulsion is a non-Newtonian fluid.

The above results demonstrate that ZH-CNW dual pickering emulsions can improve and enhance the rheological properties of conventional CNW emulsions.

(2) Characterization and determination of oil embedding rate of zein hydrolysate-microcrystalline chitin double pickering emulsion:

1g of the ZH-CNW double pickering emulsions of examples 1 to 5 and the CNW double pickering emulsion of comparative example 1 were weighed out exactly and laid out on a plate. Each was filled into a 2mL centrifuge tube of known weight. Respectively adding 1mL of n-hexane, and shaking up to extract the corn oil which is not embedded; centrifuging at 5000g for 5min, removing organic phase, washing with distilled water, centrifuging, and removing water phase; after three repeated washes, the weight was recorded and oven dried at 70 ℃ to constant weight. All samples were tested in three groups in parallel, and the oil entrapment rate was calculated as follows:

EE(％)＝MW/MD*100％

where MW refers to the weight (mg) of the sample after removal of non-embedded oil and moisture, and MD refers to the weight (mg) of the sample after removal of moisture.

The test results are shown in FIG. 6, in which 0, 0.25, 0.5, 1.0, 1.5, 2.0 represent the CNW double pickering emulsion prepared in comparative example 1 and the ZH-CNW double pickering emulsions prepared in examples 1 to 5, respectively, in this order.

As can be seen from the figure, the embedding rate of oil in ZH-CNW double pickering emulsion prepared in example 1 was 87.05%, the embedding rate of oil in ZH-CNW double pickering emulsion prepared in example 2 was 89.69%, and the embedding rate of oil in ZH-CNW double pickering emulsion prepared in example 3 was 88.38%. The embedding rate of grease in the ZH-CNW double pickering emulsion prepared in example 4 is 78.46%, and the embedding rate of grease in the ZH-CNW double pickering emulsion prepared in example 5 is 79.06%, which is obviously superior to the embedding rate of grease in the CNW emulsion alone (comparative example 1) (75%), but the complex group at too high concentration is easy to destabilize, so that the embedding rate is not obviously superior to the CNW emulsion.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.