A chlorella protein hydrolysate-based oil gel, and a preparation method and application thereof

Abstract

The application discloses a Chlorella protein hydrolysate-based oil gel and a preparation method and application thereof in the field of plant-based food, and the preparation method comprises the following steps: using or not using a protease to hydrolyze Chlorella protein to obtain Chlorella protein hydrolysate, and dispersing the Chlorella protein hydrolysate in water to form a Chlorella protein hydrolysate suspension; after using gluconolactone to induce the Chlorella protein hydrolysate suspension to form a hydrogel, diluting the hydrogel with water, and performing one-time high-speed shearing treatment to obtain a Chlorella protein hydrolysate microgel particle dispersion; adding the Chlorella protein hydrolysate microgel particle dispersion into liquid edible vegetable oil, and performing secondary high-speed shearing treatment to obtain a coarse emulsion; adding an edible polysaccharide solution into the coarse emulsion, and performing three-time high-speed shearing treatment to obtain a Chlorella protein hydrolysate-based oil-in-water emulsion; and removing water in the Chlorella protein hydrolysate-based oil-in-water emulsion to obtain the Chlorella protein hydrolysate-based oil gel. The Chlorella protein hydrolysate-based oil gel has good texture performance and oil retention.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and food processing, and particularly relates to a Chlorella protein hydrolysate-based oil gel and a preparation method and application thereof. BACKGROUND

[0002] Due to the increasing environmental protection and consumer demand for healthy and environmentally sustainable diets, plant proteins as animal protein substitutes have attracted more and more attention as functional food ingredients. In the development of plant-based products, how to simulate animal fats to achieve similar flavor and texture is also a popular direction in the research field.

[0003] Oil gel is a common form of structuring liquid oil by forming a three-dimensional network of polymers, and has certain plasticity and mechanical strength. The common direct gel method is to disperse oil gel agents (such as beeswax, monoglyceride and ethyl cellulose, etc.) in liquid oil by self-assembly to form a network to form an oil gel structure. However, the direct gel method has the defects of limited selection of oil gel agents, high requirement for oil solubility, and easy oxidation of oil phase under high temperature conditions. For example, the Chinese patent document with the publication number CN114794251A discloses a preparation method of a plant oil gel fat substitute, which needs to use beta-sitosterol and lecithin / oryzanol as oil gel agents, and the dissolution temperature is as high as 100 DEG C. The continuous high temperature environment easily leads to the early oxidation and instability of the plant oil. The emulsion template method is an indirect gel method for preparing oil gel, which uses biopolymers to prepare emulsion, and then removes the water phase by freeze-drying to obtain uniform oil gel, which has a convenient preparation process and a wide range of applications, and can exhibit excellent physicochemical properties without changing the fatty acids of plant oil. The Chinese patent document with the publication number CN113100298A discloses a preparation method of an oil gel for replacing hydrogenated vegetable oil. Soy protein is used as raw material to prepare soy protein isolate gel by heating and adding gelling agent or crosslinking agent for secondary treatment, to obtain a microgel suspension to emulsify and stabilize plant oil to obtain an oil-in-water type Pickering emulsion, and then to obtain the oil gel by freeze-drying. However, the soy protein raw material has high allergenicity, and there is still a safety risk for special groups of people to eat.

[0004] Chlorella protein is considered one of the most potential plant proteins that can replace animal protein due to its advantages of comprehensive nutrition, low allergenicity, low resource consumption, and large-scale commercial production, and has good application prospect. SUMMARY

[0005] The present application provides a Chlorella protein hydrolysate-based oil gel and a preparation method thereof. The Chlorella protein hydrolysate-based oil gel has good texture and oil holding capacity, and realizes the structuring of plant oil.

[0006] The technical scheme of the present application is as follows:

[0007] A preparation method of a Chlorella protein hydrolysate-based oil gel, comprising the following steps:

[0008] (1) enzymatically hydrolyzing Chlorella protein with or without protease to obtain Chlorella protein hydrolysate, which is dispersed in water to form a Chlorella protein hydrolysate suspension;

[0009] (2) after inducing the Chlorella protein hydrolysate suspension to form a hydrogel with gluconolactone, diluting with water, and processing with high-speed shearing once to obtain a Chlorella protein hydrolysate microgel particle dispersion;

[0010] (3) adding the Chlorella protein hydrolysate microgel particle dispersion to liquid edible vegetable oil, processing with high-speed shearing twice to obtain a coarse emulsion; adding an edible polysaccharide solution to the coarse emulsion, and processing with high-speed shearing three times to obtain a Chlorella protein hydrolysate-based oil-in-water emulsion;

[0011] (4) removing water from the Chlorella protein hydrolysate-based oil-in-water emulsion to obtain a Chlorella protein hydrolysate-based oil gel.

[0012] The present application improves the emulsifying properties of Chlorella protein by moderate hydrolysis, and realizes the structuring of vegetable oil by the combined action of Chlorella protein hydrolysate microgel particles and edible polysaccharides, and the obtained oil gel has good textural properties and oil holding capacity, the processing technology is green and mild, and the raw materials used are all derived from natural whole biomass, further expanding the application of Chlorella protein in vegetable-based oil gel.

[0013] Preferably, in step (1), the protease is papain; the addition amount of papain is 0-6% based on the mass of Chlorella protein; and the enzyme activity of papain is 100-600 U / g.

[0014] Preferably, the degree of hydrolysis of Chlorella protein hydrolysate is 0-20%; and further preferably, 0-15.5%.

[0015] Further preferably, the degree of hydrolysis of Chlorella protein hydrolysate is 1-6.5%.

[0016] The moderate hydrolysis of Chlorella protein can improve the textural properties of the oil gel. When the degree of hydrolysis of Chlorella protein hydrolysate is 1-6.5%, the droplet size of the Chlorella protein hydrolysate-based oil-in-water emulsion is smaller and more uniform, and when the degree of hydrolysis further increases, the droplet size of the oil-in-water emulsion increases and the uniformity decreases. Furthermore, when the degree of hydrolysis of Chlorella protein hydrolysate is 1-6.5%, the hardness, viscosity and chewiness of the obtained oil gel are relatively optimal, and the hardness, viscosity and chewiness of the oil gel decrease with the further increase of the degree of hydrolysis.

[0017] Most preferably, the degree of hydrolysis of the Chlorella protein hydrolysate is 3-4%.

[0018] Preferably, step (1) comprises: adjusting the Chlorella protein suspension to neutral, adding a protease, treating in a water bath at 55-60℃, inactivating the enzyme in a water bath at 95-100℃, and freeze-drying to obtain the Chlorella protein hydrolysate.

[0019] In step (2), the gluconolactone is added to the Chlorella protein hydrolysate suspension, and the mixture is left to stand at room temperature to form a hydrogel.

[0020] In step (2), the concentration of the Chlorella protein hydrolysate suspension is 5-15 g / mL; and the amount of gluconolactone added is 2-5 wt% based on the Chlorella protein hydrolysate suspension.

[0021] Within the range of 2-4 wt% gluconolactone addition, the elastic modulus of the hydrogel increases with increasing gluconolactone addition, and the elastic modulus of the hydrogel is highest when the gluconolactone addition is 4 wt%; when the gluconolactone addition is 5 wt%, the elastic modulus of the hydrogel decreases.

[0022] Further preferably, the amount of gluconolactone added is 3-4 wt% based on the Chlorella protein hydrolysate suspension.

[0023] Preferably, in step (2), the first high-speed shearing treatment is 5000-15000 rpm for 2-6 min.

[0024] The edible vegetable oil is at least one of camellia oil, soybean oil, rapeseed oil, peanut oil, sunflower seed oil, rice bran oil, corn oil, olive oil, and sesame oil.

[0025] The edible polysaccharide mainly functions to thicken. The edible polysaccharide is at least one of xanthan gum, konjac glucomannan, locust bean gum, carboxymethyl cellulose, guar gum, carrageenan, flaxseed gum, and gum arabic.

[0026] Preferably, in step (3), the volume fraction of the edible vegetable oil is 10-75% based on the Chlorella protein hydrolysate-based oil-in-water emulsion; the mass concentration of the edible polysaccharide is 0.03-0.5 wt%; and the mass concentration of the protein hydrolysate microgel particles is 1-5 wt%.

[0027] Preferably, in step (3), the second high-speed shearing treatment is 8000-15000 rpm for 2-5 min; and the third high-speed shearing treatment is 8000-15000 rpm for 1-5 min.

[0028] Step (4) comprises freezing and vacuum freeze-drying the Chlorella protein hydrolysate-based oil-in-water emulsion to remove water.

[0029] The application further provides a Chlorella protein hydrolysate-based oil gel prepared by the preparation method.

[0030] The application further provides application of the Chlorella protein hydrolysate-based oil gel in the field of plant-based food.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] (1) The Chlorella protein hydrolysate-based oil gel system of the application uses Chlorella protein, vegetable oil, natural edible polysaccharide, gluconolactone and protease as raw materials, and all are of plant origin, thereby realizing construction of a pure plant-based oil gel food.

[0033] (2) The emulsifying capacity of the Chlorella protein hydrolysate is improved to some extent through partial hydrolysis of Chlorella protein by the protease, and the application field of the Chlorella protein hydrolysate in an emulsion system is further expanded.

[0034] (3) The Chlorella protein hydrolysate-based oil-in-water emulsion and oil gel are prepared by a mild and simple method, have good texture performance and oil holding capacity, and further broaden the application scenario of Chlorella protein in plant-based food. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a flowchart of the preparation method of the Chlorella protein hydrolysate-based oil gel of the application.

[0036] Figure 2 It is oscillation frequency scanning data in rheological testing of Chlorella protein hydrolysate-based hydrogels formed by different amounts of papain under different amounts of gluconolactone, wherein (A) is that the amount of papain added is 0% of the mass of Chlorella protein in the solution (control group), and the amount of gluconolactone added is 2wt%, 3wt%, 4wt% and 5wt% in the solution respectively; (B) is that the amount of papain added is 1% of the mass of Chlorella protein in the solution, and the amount of gluconolactone added is 2wt%, 3wt%, 4wt% and 5wt% in the solution respectively; (C) is that the amount of papain added is 2% of the mass of Chlorella protein in the solution, and the amount of gluconolactone added is 2wt%, 3wt%, 4wt% and 5wt% in the solution respectively; (D) is that the amount of papain added is 2% of the mass of Chlorella protein in the solution, and the amount of gluconolactone added is 2wt%, 3wt%, 4wt% and 5wt% in the solution respectively; G' is the elastic modulus, and G" is the viscous modulus.

[0037] Figure 3The oscillation frequency scanning data in the rheological test of the acid-induced Chlorella protein hydrolysate-based hydrogel with different amounts of added papain are shown in the following table. The amounts of added papain are 0% (control group), 1%, 2%, and 4% of the mass of Chlorella protein in the solution, respectively, and the amount of added gluconolactone is 4 wt% in the solution. G' is the elastic modulus, and G" is the viscous modulus.

[0038] Figure 4 The microstructure and particle size distribution of the Chlorella protein hydrolysate-based emulsion with different amounts of added papain are shown in the following figures. The amounts of added papain in (A)-(D) are 0% (control group), 1%, 2%, and 4% of the mass of Chlorella protein in the solution, respectively, and the polysaccharide thickening agent selected is xanthan gum, with a concentration of 0.5 wt% in the mixed solution.

[0039] Figure 5 The oil retention data of the Chlorella protein hydrolysate-based oil gel with different amounts of added papain are shown in the following table. Control-O, 1% Pa-O, 2% Pa-O, and 4% Pa-O represent the amounts of added papain as 0% (control group), 1%, 2%, and 4% of the mass of Chlorella protein in the solution, respectively, and the polysaccharide thickening agent selected is xanthan gum, with a concentration of 0.5 wt% in the mixed solution. DETAILED DESCRIPTION

[0040] The application will be further described in detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate understanding of the application and do not limit it in any way.

[0041] The test methods involved in the following examples are as follows:

[0042] 1. The method for determining the degree of hydrolysis of Chlorella protein hydrolysate is determined by OPA method, and the total nitrogen content in Chlorella protein is detected by Kjeldahl nitrogen determination method, and reference is made to the national food safety standard GB 5009.5-2016.

[0043] 2. The elastic modulus G' and viscous modulus G" of the Chlorella protein hydrolysate-based hydrogel are determined by MCR302 rheometer, using a 25 mm diameter flat plate, performing oscillation frequency scanning at 25°C, with a strain of 0.1%, and the scanning range parameters are 0.1-10 Hz.

[0044] 3. The micro-morphology of the Chlorella protein hydrolysate-based emulsion is observed by optical microscope.

[0045] 4. The texture test of the Chlorella protein hydrolysate-based oil gel is performed by TA.XT Plus texture analyzer, selecting the second cycle compression mode, using P / 50 probe, setting the test speed to 1 mm / s, the deformation value to 50%, and the trigger force to 3g.

[0046] 5, Chlorella protein hydrolysate-based oil gel oil holding capacity test: about 1 g of the oil gel was weighed into a centrifuge tube of known mass and centrifuged at a speed of 8000 rpm for 15 min. The mass of the centrifuge tube was measured after the leaked vegetable oil was absorbed. The oil holding rate was calculated according to the formula: oil holding rate (%) = 100 x (1 - mass of leaked oil / mass of oil gel).

[0047] Examples 1-4

[0048] A method for preparing a chlorella protein hydrolysate, comprising the following steps:

[0049] (1) Preparation of chlorella protein suspension: a chlorella protein suspension with a mass fraction of 5% was prepared (5 g of chlorella protein was dissolved in 100 mL of deionized water), and the pH of the suspension was adjusted to 7 using 0.1 mol / L HCl or NaOH. The suspension was placed in a refrigerator at 4°C overnight to allow the protein to fully hydrate.

[0050] (2) Papain enzymatic hydrolysis of chlorella protein: the chlorella protein suspension of step (1) was heated to a constant temperature of 55°C, and 1%, 2%, 4%, and 6% of papain with a protein mass fraction was added in Examples 1-4, respectively. The amount of papain added was 100 U / g-600 U / g. After 2 h of 55°C water bath treatment, the enzyme was inactivated by 95°C water bath for 15 min. The chlorella protein hydrolysate powder was obtained by freeze-drying.

[0051] The degrees of hydrolysis of chlorella protein hydrolysates obtained by different amounts of papain addition are shown in Table 1.

[0052] Table 1 Change of degree of hydrolysis of chlorella protein hydrolysate with different amounts of papain addition

[0053]

[0054] Note: Different lowercase letters indicate significant differences, p<0.05.

[0055] As shown in Table 1, the degree of hydrolysis of chlorella protein hydrolysate gradually increased with the increase of papain addition amount, but when the papain addition amount was 6% of the protein mass fraction, the degree of hydrolysis no longer increased significantly, which may be due to the limitation of substrate concentration. Subsequently, the properties of chlorella protein hydrolysates obtained by 1%, 2%, and 4% of papain enzymatic hydrolysis of chlorella protein with a protein mass fraction and chlorella protein were further explored.

[0056] Examples 5-8

[0057] A method for preparing a chlorella protein hydrolysate-based hydrogel, comprising the following steps:

[0058] (1) Preparation of Chlorella protein hydrolysate suspension: Chlorella protein hydrolysate of Example 1-3 was prepared into 10wt% Chlorella protein hydrolysate suspension respectively (10g Chlorella protein hydrolysate was dissolved in 100ml deionized water), and the pH of the suspension was adjusted to 7 with 0.1mol / L HCl or NaOH;

[0059] (2) Preparation of GDL-induced hydrogel: 2wt%, 3wt%, 4wt% and 5wt% GDL was added into the Chlorella protein hydrolysate suspension obtained in step (1) respectively, and stirred for 30min to make it fully dissolved, and then the sample was transferred to a 4℃ refrigerator for storage overnight to obtain the hydrogel sample.

[0060] Table 2 Effect of different papain and GDL addition amount on the pH value of Chlorella protein hydrolysate hydrogel

[0061]

[0062] As can be seen from Table 2, because the initial pH value of the Chlorella protein hydrolysate dispersion is 7, after adding the same amount of GDL, the pH values of the Chlorella protein hydrolysate-based hydrogel systems with different degrees of hydrolysis are similar, but the pH value of the hydrogel system gradually decreases with the increase of the addition amount of GDL.

[0063] Figure 2 and Figure 3 The rheological scanning data of the obtained hydrogel are shown in Table 3. Wherein Figure 2 The elastic modulus (G') and viscous modulus (G") of the Chlorella protein hydrolysate-based hydrogel with different degrees of hydrolysis induced by different addition amounts of GDL are shown in Table 4. In the linear viscoelastic region, the elastic modulus of all the hydrogels is greater than the viscous modulus, which proves the formation of gel form. Within the range of 2wt% to 4wt% GDL addition amount, the elastic modulus of the hydrogel increases with the increase of the addition amount of GDL, and the elastic modulus of the hydrogel is the highest when the GDL addition amount is 4wt%; when the GDL addition amount is 5wt%, the elastic modulus of the hydrogel decreases instead. Figure 3 The oscillation scanning graph of the Chlorella hydrolysate-based hydrogel with different degrees of hydrolysis under the condition of 4wt% GDL addition amount is shown in Table 5. With the increase of the addition amount of papain leading to the increase of the degree of hydrolysis of Chlorella protein hydrolysate, the elastic modulus (G') and viscous modulus (G") of the formed hydrogel both decrease.

[0064] Examples 9-12

[0065] A method for preparing a Chlorella protein hydrolysate-based oil-in-water emulsion, comprising the following steps:

[0066] (1) Preparation of Chlorella protein hydrolysate microgel particle: 4 wt% glucolactone-induced hydrogel (0%, 1%, 2%, 4% papain addition) obtained in Example 5-8 was added with equal volume of deionized water, and high-speed shearing at 12000 rpm for 5 min to obtain Chlorella protein microgel particle dispersion;

[0067] (2) Preparation of 1 wt% xanthan gum solution;

[0068] (3) Preparation of Chlorella protein hydrolysate-based emulsion: 5 wt% Chlorella microgel particle dispersion was mixed with camellia oil in proportion, and high-speed dispersed at 12000 rpm for 3 min at room temperature, then 1 wt% xanthan gum solution was added with equal volume of Chlorella microgel particle dispersion, and high-speed dispersed at 12000 rpm for 2 min at room temperature to obtain oil-in-water (O / W) emulsion with final oil phase fraction of 75% (abbreviated as: Control-E (Example 9), 1%Pa-E (Example 10), 2%Pa-E (Example 11) and 4%Pa-E (Example 12)).

[0069] Figure 4 For the optical microscope images of the microstructure of Example 9-12, it can be observed that compared with the control group (Control-E, Example 9), when the degree of hydrolysis of Chlorella protein hydrolysate is 3.16±0.08% (1% papain addition), the droplet size of the oil-in-water emulsion stabilized by Chlorella protein hydrolysate microgel particles (1%Pa-E, Example 10) is smaller and more uniform, indicating an increase in emulsifying capacity; when the degree of hydrolysis is further increased (2% and 4% papain addition, Example 11 and Example 12), the droplet size of the oil-in-water emulsion increases, and the uniformity also decreases, indicating that further hydrolysis leads to a decrease in the emulsifying capacity of the microgel particles.

[0070] Example 13-16

[0071] A method for preparing Chlorella protein hydrolysate-based oil gel, comprising the following steps:

[0072] In Example 13-16, the emulsions obtained in Example 9-12 were respectively pre-frozen in a-80℃ refrigerator for 48 h, and then freeze-dried at-60℃ under vacuum condition (<5 Pa) for 48 h to remove water to obtain oil gel samples (abbreviated as: Control-O, 1%Pa-O, 2%Pa-O and 4%Pa-O, respectively).

[0073] The texture data of the oil gel is as follows Table 3:

[0074] Table 3 Change of texture of Chlorella protein hydrolysate-based oil gel with different papain addition

[0075]

[0076] Note: Different lowercase letters indicate significant differences, p < 0.05.

[0077] As shown in Table 3, the different degrees of hydrolysis of Chlorella protein hydrolysate caused by different amounts of papain addition had a significant effect on the hardness, viscosity, elasticity and chewiness of the oil gel. The 1% Pa-O oil gel had the highest hardness, viscosity and chewiness, and the hardness, viscosity and chewiness of the oil gel decreased with further increase in the degree of hydrolysis (papain addition increased to 2% and 4%), indicating that a certain degree of hydrolysis could improve the textural properties of the oil gel.

[0078] Figure 5 For the oil retention test results of Examples 13-16, it can be seen that all the oil gel samples had good oil retention rate (> 60%), among which the 1% Pa-O oil gel with the highest hardness also had the highest oil retention rate (76.27 ± 0.23%), and further increase in the degree of hydrolysis of Chlorella protein hydrolysate reduced the oil retention of the oil gel, which was consistent with the trend of the above-mentioned hardness and other texture data.

[0079] In summary, a certain degree of enzymolysis (degree of hydrolysis 3.16 ± 0.08%) caused by the addition of a certain amount of papain (1% of the protein mass fraction) could improve the emulsifying capacity of Chlorella protein hydrolysate, thereby forming an oil-in-water emulsion with smaller and more uniform oil droplet size, and after freeze-drying, a more uniform and dense network structure was formed, thereby forming an oil gel with more excellent texture and oil retention.

[0080] The above examples have described the technical solutions and beneficial effects of the present application in detail, and 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 of preparing a Chlorella protein hydrolysate-based oil gel, characterized by, The method comprises the following steps: (1) using protease to hydrolyze Chlorella protein to obtain Chlorella protein hydrolysate, which is dispersed in water to form a Chlorella protein hydrolysate suspension; the degree of hydrolysis of the Chlorella protein hydrolysate is 1-6.5%; (2) using gluconolactone to induce the Chlorella protein hydrolysate suspension to form a hydrogel, then diluting with water, and obtaining a Chlorella protein hydrolysate microgel particle dispersion through one-time high-speed shearing treatment; the concentration of the Chlorella protein hydrolysate suspension is 5-15 g / mL; the addition amount of gluconolactone is 2-5 wt% based on the Chlorella protein hydrolysate suspension; (3) adding the Chlorella protein hydrolysate microgel particle dispersion into liquid edible vegetable oil, and obtaining a coarse emulsion through two-time high-speed shearing treatment; adding an edible polysaccharide solution into the coarse emulsion, and obtaining a Chlorella protein hydrolysate-based oil-in-water emulsion through three-time high-speed shearing treatment; the volume fraction of the edible vegetable oil is 10-75% based on the Chlorella protein hydrolysate-based oil-in-water emulsion; the mass concentration of the edible polysaccharide is 0.03-0.5%; and the mass concentration of the protein hydrolysate microgel particle is 1-5%; (4) removing water in the Chlorella protein hydrolysate-based oil-in-water emulsion to obtain a Chlorella protein hydrolysate-based oil gel.

2. The method of preparing a Chlorella protein hydrolysate-based oil gel according to claim 1, characterized in that, In step (1), the protease is papain; the addition amount of papain is 0-6% based on the mass of Chlorella protein; and the enzyme activity of papain is 100-600 U / g.

3. The method of preparing a Chlorella protein hydrolysate-based oil gel according to claim 1, characterized in that, The addition amount of gluconolactone is 3-4 wt% based on the Chlorella protein hydrolysate suspension.

4. The method of preparing a Chlorella protein hydrolysate-based oil gel according to claim 1, characterized by, The one-time high-speed shearing treatment is 5000-15000 rpm for 2-6 min; the two-time high-speed shearing treatment is 8000-15000 rpm for 2-5 min; and the three-time high-speed shearing treatment is 8000-15000 rpm for 1-5 min.

5. The method of preparing a Chlorella protein hydrolysate-based oil gel according to claim 1, characterized in that, Step (4) comprises freezing the Chlorella protein hydrolysate-based oil-in-water emulsion and removing water through vacuum freeze-drying.

6. A Chlorella protein hydrolysate-based oil gel, characterized in that, The Chlorella protein hydrolysate-based oil gel is prepared by the preparation method in any one of claims 1-5.

7. Use of the Chlorella protein hydrolysate-based oil gel in claim 6 in the field of plant-based food.

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