Method for enhancing gel property of soybean protein isolate by using rice protein amyloid fiber

Abstract

The invention discloses a method for enhancing the gel property of soybean protein isolate by using rice protein amyloid fiber, and belongs to the technical field of protein modification. Comprising the following steps: mixing soybean protein isolate, rice protein amyloid fiber and deionized water, stirring to obtain a mixture, and sealing and heating to obtain soybean protein isolate gel containing the rice protein amyloid fiber; wherein in the mixture, the mass concentration of the rice protein amyloid fiber is 0-15%, and is not 0. The gel prepared by adding the rice protein amyloid fiber into the soybean protein isolate is superior to single soybean protein isolate gel, has higher viscoelasticity and thermal stability, forms a more compact gel network structure, and widens the application range of the soybean protein isolate in specific plant protein food. The operation method is simple and easy to implement, and has excellent industrialization prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of protein modification, and in particular relates to a method for enhancing the gel properties of soybean protein isolate by utilizing rice protein amyloid fibers. Background Art

[0002] Among many plant proteins, soy protein isolate is widely used in the production of plant-based foods (such as meat analogs) due to its balanced amino acid composition, low cholesterol and natural origin. Although people's interest in meat analogs is growing every year, they still have problems such as unclear fiber structure and poor juiciness. This is due to the poor gel properties of its main production raw material (soy protein isolate). Therefore, improving the gel properties of soy protein isolate is very important for designing and optimizing the texture and sensory properties of plant protein foods.

[0003] Recent studies have shown that amyloid fibers can effectively improve the gel properties of proteins. This is mainly due to the orderly and stable β-sheet structure of amyloid fibers, which gives proteins high mechanical strength and high temperature stability. In addition, amyloid fibers can spontaneously form a three-dimensional network structure to enhance the viscoelasticity of protein gels. However, there are currently no reports on the use of rice protein amyloid fibers to enhance the gel properties of soy protein isolate. Summary of the invention

[0004] In view of the above technical problems, the present invention proposes a method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers. This method not only provides a new idea for improving the gel properties of soy protein isolate gel, but also provides a potential strategy for developing foods rich in soy protein isolate in the future to meet the specific dietary needs of vegetarians.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the purposes of the present invention is to provide a method for enhancing the properties of soybean protein isolate gel by using rice protein amyloid fibers, comprising the following steps: mixing soybean protein isolate (SPI), rice protein amyloid fibers (RF) and deionized water, stirring to obtain a mixture, sealing and heating to obtain a soybean protein isolate gel containing rice protein amyloid fibers;

[0007] Wherein, in the mixture, the mass concentration of the rice protein amyloid fibers is 0-15%, and is not 0.

[0008] Rice protein has low allergenicity and high biological value (about 77%). It is rich in hydrophobic amino acids (phenylalanine, valine, etc.), which can not only supplement the deficiency of methionine in soy protein isolate, but also provide a prerequisite for the formation of amyloid fibers, and is an economical, high-quality, sustainable protein source. The present invention selects rice protein to self-assemble under high temperature and acidic environment to form rice protein amyloid fibers to enhance the gel properties of soy protein isolate.

[0009] Furthermore, the specific preparation steps of the rice protein amyloid fiber include:

[0010] The rice protein powder is dispersed in deionized water containing NaCl to obtain a rice protein solution, the pH value is adjusted to 2, the solution is stirred, heated and stirred, and then quickly placed in an ice bath for freeze drying, crushed and sieved to obtain rice protein amyloid fibers.

[0011] Furthermore, the mass concentration of rice protein in the rice protein solution is 12%.

[0012] Furthermore, the amount of NaCl added is 150 mmol / L; and / or

[0013] The stirring conditions are: stirring at 25°C for 6 hours; and / or

[0014] The solution used to adjust the pH is a 4 mol / L HCl solution; and / or

[0015] The heating and stirring conditions are: stirring at 90° C. and 300 rpm for 0-600 min, and not 0; and / or

[0016] The conditions for the crushing and screening are as follows: crush the rice protein amyloid fibers by a crusher with a rotation speed of 8000 r / min for 20-30 seconds, and then pass through an 80-mesh sieve.

[0017] Furthermore, the stirring condition is: stirring for 3 hours at 25° C. and pH=7, wherein the pH of all solutions is adjusted to 1 mol / L NaOH solution.

[0018] Furthermore, the sealed heating condition is: the mixture is put into a sealed glass bottle and heated at 95° C. for 30 minutes.

[0019] Furthermore, in the mixture, the volume concentration of the soy protein isolate is 12%.

[0020] The second object of the present invention is to provide a soy protein isolate gel containing rice protein amyloid fibers prepared by the above method.

[0021] The third object of the present invention is to provide an application of the above-mentioned soy protein isolate gel containing rice protein amyloid fibers in the field of food processing.

[0022] Compared with the prior art, the present invention has the following advantages and technical effects:

[0023] The present invention adopts rice protein to prepare amyloid fiber, and the process is simple, easy to operate, does not need complicated equipment, and is easy to promote. The present invention adds rice protein amyloid fiber to soybean protein isolate to prepare gel, which can not only realize amino acid complementation, but also improve the current situation that single soybean protein isolate forms poor gel property.

[0024] The invention finds that when the addition amount of rice protein amyloid fiber is 5%, the hardness, viscoelasticity and thermal properties of soy protein isolate-rice protein amyloid fiber gel are improved to varying degrees. The molecular interaction results show that hydrogen bond and hydrophobic interaction are the main driving forces for the combination of soy protein isolate and rice protein amyloid fiber, and the gel network is more compact, which is more conducive to promoting the formation of protein gel.

[0025] The invention changes the secondary structure of soybean protein isolate by adding rice protein amyloid fibers, thereby enhancing its gel properties. The gel prepared by the method has strong gel hardness, thermal stability and a relatively dense structure, further improving the gel properties of soybean protein isolate. In addition, the operation method of the invention is simple and easy to operate, has excellent industrialization prospects, and is expected to be developed into a new type of soybean protein isolate-based gel food. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0027] Figure 1 A flow chart of the rice protein amyloid fiber enhancing the gel properties of soy protein isolate of the present invention;

[0028] Figure 2 The macroscopic images of the gel samples prepared in Examples 1-5 and Comparative Example 1 are, from left to right, Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Example 5;

[0029] Figure 3 ThT fluorescence images of rice protein amyloid fibers at different heating times in Examples 1-5;

[0030] Figure 4 The DSC graphs of the gel samples prepared in Examples 1-5 and Comparative Example 1;

[0031] Figure 5The rheological (storage modulus) diagram of the gel samples prepared in Examples 1-5 and Comparative Example 1;

[0032] Figure 6 The rheological (loss modulus) diagram of the gel samples prepared in Examples 1-5 and Comparative Example 1;

[0033] Figure 7 This is a comparison chart of the hardness of the gel samples prepared in Example 2 and Comparative Examples 1-8;

[0034] Figure 8 This is a comparison chart of the hardness of the gel samples prepared in Example 2 and Comparative Examples 9-13;

[0035] Fig. 9 The emulsifying activity (EAI) graph of the gel samples prepared in Examples 1-5 and Comparative Example 1;

[0036] Fig.10 This is the emulsion stability (ESI) graph of the gel samples prepared in Examples 1-5 and Comparative Example 1. DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0039] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0040] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0041] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0042] The gel prepared by adding rice protein amyloid fibers to soybean protein isolate is superior to single soybean protein isolate gel, has higher viscoelasticity and thermal stability, forms a denser gel network structure, and broadens the application range of soybean protein isolate in specific plant protein foods. The operation method of the present invention is simple and easy to operate, and has excellent industrialization prospects. The specific technical scheme is as follows:

[0043] A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers comprises the following steps:

[0044] (1) Preparation method of rice protein amyloid fibers: first, rice protein powder is dispersed in deionized water (containing NaCl, pH=2), and stirred at 25° C. for 6 h to fully hydrate it; the obtained rice protein solution is heated at 90° C. for different times, and magnetically stirred at a speed of 300 rpm, and 5 mL of sample is taken at different heating time points and quickly placed in an ice bath, and then freeze-dried using a freeze dryer, and the rice protein amyloid fibers after being crushed by a pulverizer are sieved and then stored in a desiccator;

[0045] (2) Soy protein isolate, rice protein amyloid fibers and deionized water were mixed and diluted in a certain proportion, stirred at 25°C and pH = 7 for 3 h, 10 mL of the mixture was put into a sealed glass bottle (inner diameter × height = 27 mm × 60 mm), and heated at 95°C for 30 min to prepare soy protein isolate gel containing rice protein amyloid fibers in different proportions; then, the gel was placed in a refrigerator at 4°C overnight.

[0046] In the following examples of the present invention, in step (1), the concentration of the rice protein solution is 12% (w / v).

[0047] In the following examples of the present invention, in step (1), the amount of NaCl added is 150 mmol / L; and the reagent used to adjust the pH is a 4 mol / L HCl solution.

[0048] In the following examples of the present invention, in step (1), the heating at 90° C. for different time periods refers to heating for 0 min, 120 min, 240 min, 360 min, 480 min and 600 min.

[0049] In the following examples of the present invention, in step (1), rice protein amyloid fibers are crushed by a crusher with a rotation speed of 8000 r / min for 20-30 seconds and then passed through an 80-mesh sieve.

[0050] In the following examples of the present invention, in step (2), the reagent used to adjust the pH is 1 mol / L NaOH solution.

[0051] In the following examples of the present invention, in step (2), the concentration of soy protein isolate in each mixture is 12% (w / v), and the mass concentration of rice protein amyloid fibers is 0, 3, 5, 7, 10 and 15%.

[0052] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0053] The raw materials used in the present invention are all purchased from the market.

[0054] The technical solution of the present invention is further illustrated by the following embodiments.

[0055] Figure 1 The present invention is a flow chart of enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers.

[0056] Example 1

[0057] A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers comprises the following steps:

[0058] (1) Preparation method of rice protein amyloid fiber (RF): a certain mass of rice protein powder is weighed and dissolved in deionized water (comprising 150mmol / L NaCl solution in the deionized water) to obtain a 12% (w / v) rice protein dispersion, the pH is adjusted to 2.0 with a 4mol / L HCl solution, and stirred on a magnetic stirrer at 25°C for 6h, then magnetically stirred at 90°C, 300rpm for 120min, then quickly placed in an ice bath and freeze-dried, and then pulverized with a pulverizer at a rotating speed of 8000r / min for 30s, and then passed through an 80-mesh sieve to obtain rice protein amyloid fiber;

[0059] (2) weighing 0.036 g of the rice protein amyloid fiber obtained in step (1) and 1.164 g of soy protein isolate powder (SPI) in 10 mL of deionized water to obtain a mixed solution, and stirring for 3 h under the conditions of 25 ° C and pH = 7 (using 1 mol / L NaOH solution to adjust the pH) using a magnetic stirrer to form a soy protein isolate dispersion containing 3% (w / w) rice protein amyloid fiber;

[0060] (3) The dispersion obtained in step (2) was placed in a sealed glass bottle (inner diameter × height = 27 mm × 60 mm), and heated at 95° C. for 30 min to prepare a soy protein isolate gel containing rice protein amyloid fibers. Subsequently, the gel was placed in a refrigerator at 4° C. overnight to form a soy protein isolate gel containing 3% (w / w) rice protein amyloid fibers (denoted as SPI-3% RF complex).

[0061] Example 2

[0062] A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers comprises the following steps:

[0063] (1) Preparation method of rice protein amyloid fiber (RF): a certain mass of rice protein powder is weighed and dissolved in deionized water (comprising 150mmol / L NaCl solution in the deionized water) to obtain a 12% (w / v) rice protein dispersion, the pH is adjusted to 2.0 with a 4mol / L HCl solution, and stirred on a magnetic stirrer at 25°C for 6h, then magnetically stirred at 90°C, 300rpm for 240min, then quickly placed in an ice bath for freeze drying, and then pulverized the rice protein amyloid fiber with a pulverizer at a rotating speed of 8000r / min for 30s, and then passed through an 80-mesh sieve to obtain the rice protein amyloid fiber;

[0064] (2) weighing 0.06 g of the rice protein amyloid fiber obtained in step (1) and 1.14 g of soy protein isolate powder in 10 mL of deionized water to obtain a mixed solution, and stirring for 3 h under the conditions of 25 ° C and pH = 7 (using 1 mol / L NaOH solution to adjust the pH) using a magnetic stirrer to form a soy protein isolate dispersion containing 5% (w / w) rice protein amyloid fiber;

[0065] (3) The dispersion obtained in step (2) was placed in a sealed glass bottle (inner diameter × height = 27 mm × 60 mm), and heated at 95° C. for 30 min to prepare a soy protein isolate gel containing rice protein amyloid fibers. Subsequently, the gel was placed in a refrigerator at 4° C. overnight to form a soy protein isolate gel containing 5% (w / w) rice protein amyloid fibers (denoted as SPI-5% RF complex).

[0066] Example 3

[0067] A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers comprises the following steps:

[0068] (1) Preparation method of rice protein amyloid fiber (RF): a certain mass of rice protein powder is weighed and dissolved in deionized water (comprising 150mmol / L NaCl solution in the deionized water) to obtain a 12% (w / v) rice protein dispersion, the pH is adjusted to 2.0 with a 4mol / L HCl solution, and stirred on a magnetic stirrer at 25°C for 6h, then magnetically stirred at 90°C, 300rpm for 360min, then quickly placed in an ice bath for freeze drying, and then pulverized the rice protein amyloid fiber with a pulverizer at a rotating speed of 8000r / min for 30s, and then passed through an 80-mesh sieve to obtain the rice protein amyloid fiber;

[0069] (2) weighing 0.084 g of the rice protein amyloid fiber obtained in step (1) and 1.116 g of soy protein isolate powder in 10 mL of deionized water to obtain a mixed solution, and stirring for 3 h under the conditions of 25 ° C and pH = 7 (using 1 mol / L NaOH solution to adjust the pH) using a magnetic stirrer to form a soy protein isolate dispersion containing 7% (w / w) rice protein amyloid fiber;

[0070] (3) The dispersion obtained in step (2) was placed in a sealed glass bottle (inner diameter × height = 27 mm × 60 mm), and heated at 95° C. for 30 min to prepare a soy protein isolate gel containing rice protein amyloid fibers. Subsequently, the gel was placed in a refrigerator at 4° C. overnight to form a soy protein isolate gel containing 7% (w / w) rice protein amyloid fibers (denoted as SPI-7% RF complex).

[0071] Example 4

[0072] A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers comprises the following steps:

[0073] (1) Preparation method of rice protein amyloid fiber (RF): a certain mass of rice protein powder is weighed and dissolved in deionized water (the deionized water contains 150 mmol / L NaCl solution) to obtain a 12% (w / v) rice protein dispersion, the pH is adjusted to 2.0 with 4 mol / L HCl solution, and stirred on a magnetic stirrer at 25° C. for 6 h, then magnetically stirred at 90° C. and 300 rpm for 480 min, then quickly placed in an ice bath for freeze drying, and then pulverized the rice protein amyloid fiber using a pulverizer with a rotation speed of 8000 r / min for 30 s, and then passed through an 80-mesh sieve to obtain rice protein amyloid fiber;

[0074] (2) weighing 0.12 g of the rice protein amyloid fiber obtained in step (1) and 1.08 g of soy protein isolate powder in 10 mL of deionized water to obtain a mixed solution, and stirring for 3 h under the conditions of 25 ° C and pH = 7 (using 1 mol / L NaOH solution to adjust the pH) using a magnetic stirrer to form a soy protein isolate dispersion containing 10% (w / w) rice protein amyloid fiber;

[0075] (3) The dispersion obtained in step (2) was placed in a sealed glass bottle (inner diameter × height = 27 mm × 60 mm), and heated at 95° C. for 30 min to prepare a soy protein isolate gel containing rice protein amyloid fibers. Subsequently, the gel was placed in a refrigerator at 4° C. overnight to form a soy protein isolate gel containing 10% (w / w) rice protein amyloid fibers (denoted as SPI-10% RF complex).

[0076] Example 5

[0077] A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers comprises the following steps:

[0078] (1) Preparation method of rice protein amyloid fiber (RF): a certain mass of rice protein powder is weighed and dissolved in deionized water (the deionized water contains 150mmol / L NaCl solution) to obtain a 12% (w / v) rice protein dispersion, the pH is adjusted to 2.0 with 4mol / L HCl solution, and stirred on a magnetic stirrer at 25°C for 6h, then magnetically stirred at 90°C and 300rpm for 600min, then quickly placed in an ice bath for freeze drying, and then pulverized the rice protein amyloid fiber with a rotation speed of 8000r / min for 30s, and then passed through an 80-mesh sieve to obtain rice protein amyloid fiber;

[0079] (2) weighing 0.18g of the rice protein amyloid fiber obtained in step (1) and 1.02g of soy protein isolate powder in 10mL deionized water to obtain a mixed solution, utilizing a magnetic stirrer to stir for 3h under the condition of 25°C, pH=7 (using 1mol / L NaOH solution to adjust the pH), to form a soy protein isolate dispersion containing 15% (w / w) rice protein amyloid fiber;

[0080] (3) The dispersion obtained in step (2) was placed in a sealed glass bottle (inner diameter × height = 27 mm × 60 mm), and heated at 95° C. for 30 min to prepare a soy protein isolate gel containing rice protein amyloid fibers. Subsequently, the gel was placed in a refrigerator at 4° C. overnight to form a soy protein isolate gel containing 15% (w / w) rice protein amyloid fibers (denoted as SPI-15% RF complex).

[0081] Comparative Example 1

[0082] A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers comprises the following steps:

[0083] (1) 1.2 g of soy protein isolate powder was weighed and mixed with 10 mL of deionized water, and stirred for 3 h at 25° C. and pH 7 (pH was adjusted with 1 mol / L NaOH solution) using a magnetic stirrer to form a soy protein isolate dispersion containing 12% (w / w);

[0084] (2) The dispersion obtained in step (1) was placed in a sealed glass bottle (inner diameter × height = 27 mm × 60 mm), and heated at 95° C. for 30 min to prepare a soy protein isolate gel containing rice protein amyloid fibers. Subsequently, the gel was placed in a refrigerator at 4° C. overnight to form a 12% (w / w) soy protein isolate gel (denoted as SPI) having a concentration of no rice protein amyloid fibers.

[0085] Comparative Example 2

[0086] The same as Example 2, except that rice protein amyloid fibers were replaced by OF (ovalbumin amyloid fibers), to obtain a soy protein isolate gel containing 5% (w / w) ovalbumin amyloid fibers (denoted as SPI-OF complex).

[0087] Comparative Example 3

[0088] The same as Example 2, except that the rice protein amyloid fibers were replaced with HF (hemp seed protein amyloid fibers), to obtain a soy protein isolate gel containing 5% (w / w) hemp seed protein amyloid fibers (denoted as SPI-HF complex).

[0089] Comparative Example 4

[0090] The same as Example 2, except that the rice protein amyloid fibers were replaced with PF (peanut protein amyloid fibers), to obtain a soy protein isolate gel containing 5% (w / w) peanut protein amyloid fibers (denoted as SPI-PF complex).

[0091] Comparative Example 5

[0092] The same as Example 2, except that the rice protein amyloid fibers are replaced by OPF (oat protein amyloid fibers), to obtain a soy protein isolate gel containing 5% (w / w) oat protein amyloid fibers (denoted as SPI-OPF complex).

[0093] Comparative Example 6

[0094] Same as Example 2, except that rice protein amyloid fibers were replaced with PSF (pumpkin seed protein amyloid fibers), to obtain a soy protein isolate gel containing 5% (w / w) pumpkin seed protein amyloid fibers (denoted as SPI-PSF complex).

[0095] Comparative Example 7

[0096] The same as Example 2, except that the rice protein amyloid fibers were replaced with CSF (cottonseed protein amyloid fibers), to obtain a soy protein isolate gel containing 5% (w / w) cottonseed protein amyloid fibers (denoted as SPI-CSF complex).

[0097] Comparative Example 8

[0098] Same as Example 2, except that rice protein amyloid fibers are replaced with PPF (potato protein amyloid fibers), to obtain a soy protein isolate gel containing 5% (w / w) potato protein amyloid fibers (denoted as SPI-PPF complex).

[0099] Comparative Example 9

[0100] The same as Example 2, except that the mass of soy protein isolate was replaced by PP (pea protein), and a pea protein gel containing 5% (w / w) rice protein amyloid fibers (denoted as PP-RF complex) was obtained.

[0101] Comparative Example 10

[0102] The same as Example 2, except that the mass of soy protein isolate was replaced by WP (whey protein), and a whey protein gel containing 5% (w / w) rice protein amyloid fibers (denoted as WP-RF complex) was obtained.

[0103] Comparative Example 11

[0104] The same as Example 2, except that the mass of soy protein isolate was replaced by WHP (wheat protein), and a wheat protein gel containing 5% (w / w) rice protein amyloid fibers (referred to as WHP-RF complex) was obtained.

[0105] Comparative Example 12

[0106] Same as Example 2, except that the mass of soy protein isolate was replaced by PEP (peanut protein), to obtain a peanut protein gel containing 5% (w / w) rice protein amyloid fibers (denoted as PEP-RF complex).

[0107] Comparative Example 13

[0108] The same as Example 2, except that the mass of soy protein isolate was replaced by CP (zein), and a zein gel containing 5% (w / w) rice protein amyloid fibers (denoted as CP-RF complex) was obtained.

[0109] Figure 2 The macroscopic images of the gel samples prepared in Examples 1-5 and Comparative Example 1 are shown in FIG. Figure 2 It can be clearly seen that when the addition amount of rice protein amyloid fiber reaches 5%, the hardness of the soy protein isolate gel is significantly improved, exceeding the gel hardness of the soy protein isolate, and forming a stable protein gel.

[0110] Test Example 1

[0111] The maximum fluorescence intensity of ThT (thioflavin T) of rice protein amyloid fibers under different heating times was tested. The specific method was as follows: ThT solution (0.016 g / L, pH=7.0) was mixed with the gel sample solution, reacted in the dark for 120 s, and scanned with a fluorescence spectrophotometer at an excitation wavelength of 440 nm and an emission wavelength of 490 nm.

[0112] Figure 3 ThT fluorescence images of rice protein amyloid fibers at different heating times in Examples 1-5, from Figure 3 As can be seen in the figure, as the heating time increases, the maximum fluorescence intensity of ThT continues to rise, indicating that the rice protein amyloid fibers are gradually formed in an orderly manner and the structure is more stable. When the heating time is extended to 360 minutes, the fluorescence intensity reaches the maximum value, which may be due to the increase in β-sheet content. This phenomenon shows that the fibrillation degree of rice protein amyloid fibers is the best at 360 minutes.

[0113] Test Example 2

[0114] DSC test of rice protein amyloid fiber-soy protein isolate gel was performed as follows: freeze-dried SPI-RF complex (3 mg) was weighed into a standard aluminum crucible, and then the sample was heated from 30°C to 250°C at a rate of 10°C / min. The peak temperature (T m ) and enthalpy change (ΔH) data were obtained using TA analysis software.

[0115] Figure 4 Table 1 is the DSC graph of the gel samples prepared in Examples 1-5 and Comparative Example 1. Table 1 is the characteristic temperature (T m ) and enthalpy change (ΔH).

[0116] Table 1

[0117]

[0118] Note: Different lowercase letters (a, b, c, d) in the same column indicate significant differences (P<0.05).

[0119] from Figure 4 As can be seen from Table 1, SPI gel m The endothermic peak appears at 118.07℃, and ΔH is 187.6J / g. Compared with SPI gel, except for SPI-15%RF, the T m These results indicate that the addition of an appropriate amount of RF makes the network structure highly ordered and compact, and denaturation requires more energy. Adding 5% RF to SPI can increase T m and ΔH increased by 3.20% and 24.63%, respectively. This result is attributed to the fact that the addition of 5% RF promoted the formation of hydrogen bonds and hydrophobic interactions inside the gel, thus producing a more heat-resistant gel.

[0120] Test Example 3

[0121] The rheological properties of rice protein amyloid fiber-soy protein isolate gel were tested by using a DHR-3 rheometer equipped with a 40 mm plate to measure the rheological behavior of the SPI-RF solution (the gel solution was fully stirred for 3 h before heating). In order to reduce the impact of the environment on the sample, the sample was sealed with a thin layer of glycerol. The storage modulus (G') and loss modulus (G") of the sample were then measured to evaluate the effect of angular frequency changes on the rheological properties of the gel.

[0122] Figure 5 The rheological (storage modulus) diagram of the gel samples prepared in Examples 1-5 and Comparative Example 1;

[0123] Figure 6 The rheological (loss modulus) diagram of the gel samples prepared in Examples 1-5 and Comparative Example 1.

[0124] from Figure 5 and Figure 6 It can be seen that during the entire test process, G' was observed to be greater than G", indicating that all samples showed elastic behavior and formed a gel structure. Compared with the SPI gel, the addition of 5% RF significantly increased G', indicating that 5% RF can significantly improve the elasticity of the gel. When the RF content increased from 7% to 15%, the G' value gradually decreased, and the G' value of SPI-15% RF was lower than that of SPI gel. This phenomenon is due to the fact that the further increase in RF concentration enhances the electrostatic repulsion, resulting in a weakened network structure.

[0125] Test Example 4

[0126] The gel hardness test of different types of protein amyloid fibers-soy protein isolate gel and rice protein amyloid fibers-different types of protein gel is as follows: the hardness of the gel is measured using a P / 0.5 probe in a texture analyzer.

[0127] Figure 7 This is a comparison chart of the hardness of the gel samples prepared in Example 2 and Comparative Examples 1-8. Figure 7 It can be seen that in the whole test process, it is observed that compared with pure soy protein isolate gel, adding different types of amyloid fibers at the same content all improves the hardness of soy protein isolate gel, among which adding rice protein amyloid fibers (RF) can significantly improve the hardness of soy protein isolate gel, and has the highest gel hardness. The reason for this phenomenon is that the extremely high aspect ratio and high order of RF enhance the gelling ability of soy protein isolate. In addition, the appropriate amount of RF (5%) increases the interaction between protein molecules and enhances the orderly arrangement of the network in SPI-RF gel.

[0128] Figure 8 This is a comparison chart of the hardness of the gel samples prepared in Example 2 and Comparative Examples 9-13. Figure 8 It can be seen that when the same amount of rice protein amyloid fibers are added to different proteins, the gel hardness varies greatly. Among them, the gel hardness of rice protein amyloid fibers added to soy protein isolate is the highest, which effectively improves the gel properties. However, the gel hardness of rice protein amyloid fibers added to pea protein, whey protein, wheat protein, peanut protein and corn protein does not reach the effect of soy protein isolate. This may be related to the characteristics of each protein itself, such as differences in amino acids, surface hydrophobicity, protein solubility and molecular weight, which leads to different gel hardness.

[0129] In summary, adding rice protein amyloid fibers to soy protein isolate can significantly improve the gel properties of soy protein isolate.

[0130] Test Example 5

[0131] Rice protein amyloid fiber-soy protein isolate emulsifying performance test, including emulsifying activity (EAI) and emulsifying stability (ESI) index determination. The specific method is: the gel samples prepared by Examples 1-5 and Comparative Example 1 are dissolved in deionized water for 12 hours under stirring at room temperature. 20% (w / w) soybean oil and 80% (w / w) SPI / RF composite solution are homogenized at 13000rpm for 2min (3 times, 5s intervals, 40s each time) with a high-speed homogenizer. Then, sodium azide (0.01% w / w) is added to all samples to prevent microbial growth. The concentration of gel in the final emulsion is 0.5% w / w, and the sample is always in an ice-water bath during the entire homogenization process. After the emulsion is prepared, let it stand for 1 min, take 50 μL of the emulsion from the bottom of the beaker and add it to 5 mL of 1.0 g / L SDS, mix well and measure the absorbance of the solution at 500 nm, which is recorded as A1; after 60 min, take 50 μL of the emulsion from the bottom of the beaker and perform the same operation, and the absorbance is recorded as A 60 Calculate EAI (m according to formula (1) and (2) 2 / g) and ESI (%).

[0132]

[0133] ESI / % = A 60 / A1×100(2);

[0134] In the formula: T is the conversion coefficient, which is 2.303; N is the dilution factor, which is 201; is the volume fraction of the dispersed phase, which is 0.25; ρ is the protein concentration before emulsification, which is 20 g / L.

[0135] Fig. 9 The emulsifying activity (EAI) graph of the gel samples prepared in Examples 1-5 and Comparative Example 1;

[0136] Fig.10 This is the emulsion stability (ESI) graph of the gel samples prepared in Examples 1-5 and Comparative Example 1.

[0137] from Fig. 9 and Fig.10 It can be seen that compared with the soy protein isolate emulsion, the addition of rice protein amyloid fibers improves the emulsifying activity and stability of soy protein isolate; indicating that SPI modified with rice protein amyloid fibers is more likely to form an interfacial film on the surface of oil droplets, thereby promoting the dispersion of oil droplets and stabilizing the emulsion oil droplets.

[0138] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers, characterized in that: The following steps are involved: The soy protein isolate, rice protein amyloid fibers and deionized water are mixed, stirred to obtain a mixture, and sealed and heated to obtain a soy protein isolate gel containing rice protein amyloid fibers; Wherein, in the mixture, the mass concentration of the rice protein amyloid fibers is 0-15%, and is not 0.

2. The method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers according to claim 1, wherein: The specific preparation steps of the rice protein amyloid fiber include: The rice protein powder is dispersed in deionized water containing NaCl to obtain a rice protein solution, the pH value is adjusted to 2, the solution is stirred, heated and stirred, and then quickly placed in an ice bath for freeze drying, crushed and sieved to obtain rice protein amyloid fibers.

3. The method for utilizing rice protein amyloid fibers to enhance the gel properties of soy protein isolate according to claim 2, characterized in that: The mass concentration of rice protein in the rice protein solution is 12%.

4. The method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers according to claim 2, characterized in that: During the preparation of rice protein amyloid fibers, The amount of NaCl added is 150 mmol / L; and / or The stirring conditions are: stirring at 25°C for 6 hours; and / or The solution used to adjust the pH is 4 mol / L HCl solution; and / or The heating and stirring conditions are: stirring at 90° C. and 300 rpm for 0-600 min, and not 0; and / or The conditions for the crushing and screening are as follows: crush the rice protein amyloid fibers by a crusher with a rotation speed of 8000 r / min for 20-30 seconds, and then pass through an 80-mesh sieve.

5. The method for utilizing rice protein amyloid fibers to enhance the gel properties of soy protein isolate according to claim 1, characterized in that: The stirring conditions are: stirring for 3 hours at 25° C. and pH=7, wherein the pH of all solutions is adjusted to 1 mol / L NaOH solution.

6. The method for enhancing the gel properties of soy protein isolate by using rice protein amyloid fibers according to claim 1, characterized in that: The sealed heating conditions are as follows: the mixture is placed in a sealed glass bottle and heated at 95° C. for 30 min.

7. A soy protein isolate gel containing rice protein amyloid fibers prepared by the method described in any one of claims 1 to 6.

8. Use of the soy protein isolate gel containing rice protein amyloid fibers as claimed in claim 7 in the field of food processing.

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