Low oil internal phase emulsion gels based on regenerated silk fibroin and methods of making the same

Abstract

The application discloses a low-oil internal phase emulsion gel based on regenerated silk fibroin and a preparation method thereof, and the preparation method comprises the following steps: (1) dissolving regenerated silk fibroin and xanthan gum in water to prepare an aqueous solution, and adjusting the pH of the aqueous solution to 7; (2) mixing plant oil and the aqueous solution in step (1) and performing homogenization, and standing, since plant oil droplets are embedded in a gel matrix to form a self-supporting structure, a low-oil internal phase emulsion gel based on regenerated silk fibroin is obtained. The preparation method can gelate the regenerated silk fibroin under simple emulsification conditions, and a low-oil internal phase emulsion gel with a compact structure, excellent mechanical properties and stability is obtained, and the emulsion gel can be widely applied in the fields of medicine, food, cosmetics and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of colloidal materials, and particularly relates to a low-oil internal phase emulsion gel based on regenerated silk fibroin and a preparation method thereof. BACKGROUND

[0002] An emulsion gel is a semi-solid material in which oil droplets are dispersed in a gel matrix. According to the state of the droplets in the gel matrix, emulsion gels can be roughly divided into two types: emulsion-filled gels and emulsion-aggregated gels. Generally speaking, for O / W emulsions, the droplets of low-oil internal phase emulsions are filled into the gel matrix to form emulsion-filled gels, while the droplets of high internal phase emulsions containing a higher volume fraction of oil tend to aggregate to form emulsion-aggregated gels. Low-oil internal phase emulsion gels conform to the principle of green living and have attracted widespread attention from researchers.

[0003] In the process of food processing, low-oil internal phase emulsions can often form a gel network by adding a crosslinking agent, heat, acid or enzyme induction, etc.

[0004] A preparation method of a rice bran protein emulsion gel is disclosed in Chinese Patent No. CN112063002A, in which a stable network structure of rice bran protein emulsion is formed by ultrasonic induction. Du Yuhun et al. (Du Yuhun et al. Whey protein isolate-glucose Maillard reaction products and their application in algal oil emulsion gel [J]. China Food Additives, 2023, 34) used whey protein isolate and glucose as raw materials to prepare an emulsion gel loaded with algal oil by crosslinking using Maillard reaction.

[0005] However, these methods for preparing low-oil internal phase emulsion gels are very complex, which limits their application in industrial production. Therefore, it is crucial to develop a simple method for preparing low-oil internal phase emulsion gels for large-scale production. SUMMARY

[0006] The present application provides a low-oil internal phase emulsion gel based on regenerated silk fibroin and a preparation method thereof, which has a high gel strength and good elasticity, cohesiveness, chewiness, adhesiveness, water-holding capacity and stability.

[0007] The technical solution of the present application is as follows:

[0008] A preparation method of a low-oil internal phase emulsion gel based on regenerated silk fibroin, comprising the following steps:

[0009] (1) Dissolve regenerated silk fibroin and a thickening agent in water to prepare an aqueous solution, and adjust the pH of the aqueous solution to 7;

[0010] (2) mixing the plant oil with the aqueous solution in step (1) and homogenizing, and standing, to obtain a low-oil internal phase emulsion gel based on regenerated silk fibroin, since the plant oil droplets are embedded in the gel matrix to form a self-supporting structure.

[0011] Preferably, in the aqueous solution in step (1), the mass ratio of the thickening agent to regenerated silk fibroin is 1:20-50. The solubilization temperature of regenerated silk fibroin and the thickening agent is 10-40℃.

[0012] The thickening agent plays a thickening role in the emulsion gel, and can prevent phase separation of the emulsion during gelation.

[0013] The thickening agent can be one or more of xanthan gum, pectin, konjac glucomannan, and carrageenan.

[0014] The higher the concentration of regenerated silk fibroin, the darker the color of the emulsion gel, and the shorter the gelation time; when the concentration of regenerated silk fibroin is too low, it is difficult to form a gel.

[0015] Preferably, in the aqueous solution in step (1), the concentration of regenerated silk fibroin is 2-10%.

[0016] Preferably, the preparation method of the regenerated silk fibroin comprises:

[0017] (1-1) mixing the silk fibroin powder after degumming of silk with a CaCl2 / H2O / C2H5OH ternary solution, heating to perform salt dissolution;

[0018] (1-2) centrifuging the salt-dissolved solution in step (1-1), taking the supernatant; dialyzing the supernatant, collecting the dialysate and freeze-drying to obtain regenerated silk fibroin.

[0019] In the CaCl2 / H2O / C2H5OH ternary solution, the molar ratio of CaCl2, H2O and C2H5OH is 1:8:2.

[0020] Preferably, the mass ratio of the silk fibroin powder to the CaCl2 / H2O / C2H5OH ternary solution is 1:10-20.

[0021] Preferably, in step (1-2), the centrifugation temperature is 20-25℃, the rotation speed is 4000-8000 rpm, and the centrifugation time is 20-30 min.

[0022] Preferably, in step (2), the plant oil is one or more of soybean oil, rapeseed oil, peanut oil, sunflower oil, camellia oil, sesame oil, corn oil, wheat germ oil, olive oil, hempseed oil, canola oil, palm oil, palm olein, palm kernel oil, coconut oil, palm stearin, cocoa butter, shea fractionated stearin, sal butter, mango kernel oil, illipe butter, coconut stearin.

[0023] The more the plant oil is added, the greater the hardness of the emulsion gel; too much plant oil can cause emulsion demulsification and other adverse effects.

[0024] Preferably, in step (2), the volume ratio of plant oil to aqueous solution of step (1) is 5-30:100.

[0025] The application also provides a low-oil internal phase emulsion gel prepared by the above preparation method.

[0026] The low-oil internal phase emulsion gel prepared by the application can replace solid fat and be used for preparing sausages, artificial meat, etc.

[0027] Compared with the prior art, the application has the following advantages and beneficial effects:

[0028] (1) The regenerated silk fibroin prepared by the application is mainly extracted from natural silk. At present, there is no report on the rapid formation of gel under the condition of only physical change of silk fibroin, so the application opens up new possibilities for scientific research and practical application of silk fibroin.

[0029] (2) The preparation method of the low-oil internal phase emulsion gel has mild reaction conditions, and the liquid protein-polysaccharide solution can be converted into a solid gel through simple emulsification and standing. Meanwhile, the obtained gel has a dense structure, excellent mechanical properties and stability, meets the concept of green and sustainable development, and has a broad application prospect in the fields of food, cosmetics, medical treatment, etc. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Schematic diagram for preparing an emulsion gel from camellia oil and xanthan gum and regenerated silk fibroin.

[0031] Figure 2 The apparent morphology diagram of the regenerated silk fibroin emulsion gel / solution prepared in Examples 1-5 and Comparative Example 1 is shown from left to right as Comparative Example 1, Examples 1-5.

[0032] Figure 3 The liquid holding capacity diagram of the regenerated silk fibroin emulsion gel prepared in Examples 1-5 is shown.

[0033] Figure 4 The confocal image of the regenerated silk fibroin emulsion gel prepared in Examples 1-5 is shown, A-E being Examples 1-5, respectively.

[0034] Figure 5 The diagram of the relationship between the storage modulus G' and the loss modulus G" and the strain of the regenerated silk fibroin emulsion gel prepared in Examples 1-5 is shown, the scanning frequency being 0.1 Hz, C-5, C-10, C-15, C-20, C-25 being Examples 1-5, respectively.

[0035] Figure 6 Storage modulus G' and loss modulus G" of the regenerated silk fibroin emulsion gel prepared in Examples 1-5 versus frequency, strain is 0.1%, C-5, C-10, C-15, C-20, C-25 are Examples 1-5 respectively.

[0036] Figure 7 Shear rate versus viscosity of the regenerated silk fibroin emulsion gel prepared in Examples 1-5, strain is 0.1%, C-5, C-10, C-15, C-20, C-25 are Examples 1-5 respectively.

[0037] Figure 8 Changes in oil peroxide value in the regenerated silk fibroin emulsion gel prepared in Examples 1-5 over 14 days of storage, C-5, C-10, C-15, C-20, C-25 are Examples 1-5 respectively. DETAILED DESCRIPTION

[0038] The application will be further described in conjunction with the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate the understanding of the application and do not limit the application in any way.

[0039] The silk fibroin raw material used in the following examples and comparative examples was provided by Hangzhou Linran Biotechnology Co., Ltd. The remaining reagents or instruments used without specifying the manufacturer are considered to be conventional products that can be purchased on the market.

[0040] The schematic diagram of preparing the emulsion gel using camellia oil, xanthan gum and regenerated silk fibroin according to the application is shown in Figure 1 .

[0041] Example 1

[0042] A certain amount of silk fibroin powder was weighed and added to a CaCl2 / H2O / C2H5OH ternary solution (molar ratio of CaCl2 / H2O / C2H5OH is 1:8:2) according to the solid-liquid mass ratio of 1:20. Salt dissolution was performed at 95℃ for 2h. After cooling, the salt-dissolved solution was centrifuged, and the supernatant was transferred to a dialysis bag for dialysis for 48h. The dialysate was collected and freeze-dried to obtain regenerated silk fibroin powder.

[0043] 5g of regenerated silk fibroin and 0.2g of xanthan gum were dissolved in 100mL of deionized water to form a solution, and the pH of the aqueous solution was adjusted to 7 using NaOH solution and HCl solution. 5mL of camellia oil was mixed with the xanthan gum and regenerated silk fibroin aqueous solution, and then homogenized. After standing for 12h, a regenerated silk fibroin emulsion gel was obtained.

[0044] Example 2

[0045] The method for preparing the regenerated silk fibroin powder is the same as that in Example 1.

[0046] 5 g of regenerated silk fibroin and 0.2 g of xanthan gum were dissolved in 100 mL of deionized water to form a solution, and the pH of the aqueous solution was adjusted to 7 using NaOH solution and HCl solution. 10 mL of camellia oil was mixed with the xanthan gum and regenerated silk fibroin aqueous solution, and then homogenized. After standing for 12 h, a regenerated silk fibroin emulsion gel was obtained.

[0047] Example 3

[0048] The method for preparing the regenerated silk fibroin powder is the same as that in Example 1.

[0049] 5 g of regenerated silk fibroin and 0.2 g of xanthan gum were dissolved in 100 mL of deionized water to form a solution, and the pH of the aqueous solution was adjusted to 7 using NaOH solution and HCl solution. 15 mL of camellia oil was mixed with the xanthan gum and regenerated silk fibroin aqueous solution, and then homogenized. After standing for 12 h, a regenerated silk fibroin emulsion gel was obtained.

[0050] Example 4

[0051] The method for preparing the regenerated silk fibroin powder is the same as that in Example 1.

[0052] 5 g of regenerated silk fibroin and 0.2 g of xanthan gum were dissolved in 100 mL of deionized water to form a solution, and the pH of the aqueous solution was adjusted to 7 using NaOH solution and HCl solution. 20 mL of camellia oil was mixed with the xanthan gum and regenerated silk fibroin aqueous solution, and then homogenized. After standing for 12 h, a regenerated silk fibroin emulsion gel was obtained.

[0053] Example 5

[0054] The method for preparing the regenerated silk fibroin powder is the same as that in Example 1.

[0055] 5 g of regenerated silk fibroin and 0.2 g of xanthan gum were dissolved in 100 mL of deionized water to form a solution, and the pH of the aqueous solution was adjusted to 7 using NaOH solution and HCl solution. 25 mL of camellia oil was mixed with the xanthan gum and regenerated silk fibroin aqueous solution, and then homogenized. After standing for 12 h, a regenerated silk fibroin emulsion gel was obtained.

[0056] Comparative Example 1

[0057] The method for preparing the regenerated silk fibroin powder is the same as that in Example 1.

[0058] 5 g of regenerated silk fibroin and 0.2 g of xanthan gum were dissolved in 100 mL of deionized water to form a solution, and the pH of the aqueous solution was adjusted to 7 using NaOH solution and HCl solution. The xanthan gum and regenerated silk fibroin aqueous solution were mixed, and then homogenized. After standing for 12 h, a regenerated silk fibroin emulsion gel was obtained.

[0059] Figure 1 Schematic diagram of the formation mechanism of regenerated silk fibroin emulsion gel.

[0060] As shown in Figure 2 , the xanthan gum alone and the regenerated silk fibroin aqueous solution cannot form a gel. In Examples 1-5, the plant oil droplets are embedded in the gel matrix to form a self-supporting structure, and further generate the regenerated silk fibroin emulsion gel, which does not flow in the inverted sample bottle and is in the form of a gel-like solid. It is shown that the presence of oil is a necessary condition for forming a gel. The silk fibroin solution is brownish yellow, while the emulsion gel is ivory white, and as the mass fraction of oil in the emulsion gel gradually increases from 5% to 25%, the whiteness of the emulsion gel continuously increases, which shows that the addition of oil has a positive effect on the whiteness of the emulsion gel.

[0061] Figure 3 The liquid holding capacity of the regenerated silk fibroin emulsion gel prepared in Examples 1-5, from Figure 3 , it can be seen that the emulsion gel all shows excellent liquid holding capacity, more than 85%.

[0062] Figure 4 When the oil phase is dyed with Nile red (red) and the protein is dyed with Nile blue (green), the confocal images of the regenerated silk fibroin emulsion gel prepared in Examples 1-5, from Figure 4 , it can be seen that the oil droplets are uniformly distributed in the emulsion gel matrix, and no phase separation occurs. As the oil content increases, the particle size of the oil droplets also increases.

[0063] Figure 5 The relationship diagram of the storage modulus G' and the loss modulus G" of the regenerated silk fibroin emulsion gel prepared in Examples 1-5 with strain, the scanning frequency is 0.1 Hz, from Figure 5 , it can be seen that the linear viscoelastic region of the emulsion gel is 0.1-10 Hz.

[0064] Figure 6 The relationship diagram of the storage modulus G' and the loss modulus G" of the regenerated silk fibroin emulsion gel prepared in Examples 1-5 with frequency, the strain is 0.1%, from Figure 6 , it can be seen that in the linear viscoelastic region (0.1-10 Hz), the G' value of all samples is greater than the G" value, which confirms that the emulsion gel mainly shows elastic behavior. As the oil content in the emulsion gel increases from 5% to 15%, the G' value gradually increases to 9770 Pa, which shows that the structure of the emulsion gel is more solid.

[0065] Figure 7 The relationship diagram of the shear rate and the viscosity of the regenerated silk fibroin emulsion gel prepared in Examples 1-5, the strain is 0.1%, from Figure 7 , it can be seen that when the shear rate increases from 0.1 s -1 to 10 s-1 The viscosity of regenerated silk fibroin emulsion gels with different oil contents gradually decreased, indicating that they were non-Newtonian fluids. When the shear rate was 0.1 s -1 When the oil content increased from 5% to 15%, the viscosity of the emulsion gel increased from 292 to 1733 Pa·s, which was probably due to the shorter distance between the oil droplets causing greater interaction.

[0066] Figure 8 The change in the oil peroxide value of the regenerated silk fibroin emulsion gel prepared in Example 1-5 was plotted against the storage time of 14 days, from which Figure 8 It can be seen that the peroxide value increased sharply with the increase in storage time. When the oil content increased from 5% to 15%, the peroxide value of the emulsion gel decreased from 2419.3 μmol / kg to 839.9 μmol / kg, indicating that the internal structure of the emulsion gel was enhanced, which could effectively isolate the oxidation of oil caused by heat and air.

[0067] The above examples have described the technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, supplement and equivalent replacement within the principle range of the present application should be included in the protection scope of the present application.

Claims

1. A method for the preparation of a low oil internal phase emulsion gel based on regenerated silk fibroin, characterized in that, The method comprises the following steps: (1) dissolving regenerated silk fibroin and thickening agent in water to prepare an aqueous solution, and adjusting the pH of the aqueous solution to 7; the thickening agent is xanthan gum; in the aqueous solution, the mass ratio of the thickening agent to regenerated silk fibroin is 1:20-50, and the concentration of regenerated silk fibroin ranges from 2% to 10%; (2) mixing vegetable oil with the aqueous solution in step (1) and performing homogenization, and standing; since the vegetable oil droplets are embedded in the gel matrix to form a self-supporting structure, a low-oil internal phase emulsion gel based on regenerated silk fibroin is obtained; the vegetable oil is camellia oil; The volume ratio of the vegetable oil to the aqueous solution in step (1) is 5-30:

100.

2. The method for preparing a low oil internal phase emulsion gel based on regenerated silk fibroin according to claim 1, characterized in that, The preparation method of the regenerated silk fibroin comprises: (1-1) mixing silk fibroin powder after degumming of silk with a CaCl2 / H2O / C2H5OH ternary solution, heating to perform salt dissolution; (1-2) centrifuging the salt-dissolved solution in step (1-1), taking the supernatant; dialyzing the supernatant, collecting the dialysate, and freeze-drying to obtain regenerated silk fibroin.

3. The method for preparing a low oil internal phase emulsion gel based on regenerated silk fibroin according to claim 2, characterized in that, In the CaCl2 / H2O / C2H5OH ternary solution, the molar ratio of CaCl2, H2O and C2H5OH is 1:8:

2.

4. The method for preparing a low oil internal phase emulsion gel based on regenerated silk fibroin according to claim 2, characterized in that, The mass ratio of the silk fibroin powder to the CaCl2 / H2O / C2H5OH ternary solution is 1:10-20.

5. The method for preparing a low oil internal phase emulsion gel based on regenerated silk fibroin according to claim 2, characterized in that, In step (1-2), the centrifugation temperature is 20-25 ℃, the rotation speed is 4000-8000 rpm, and the centrifugation time is 20-30 min.

6. A low oil internal phase emulsion gel based on regenerated silk fibroin, characterized in that, The regenerated silk fibroin is prepared by using the preparation method in any one of claims 1-5.

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