Method for improving functional properties of soybean protein by combining heat denaturation and high pressure homogenization

Abstract

The application belongs to the field of food processing, and particularly relates to a method for improving the functional properties of soybean protein by combining heat denaturation and high-pressure homogenization treatment. The application is realized by the following method: first, a soybean protein dispersion is prepared at room temperature, the pH value is adjusted, and the soybean protein dispersion is fully dispersed by fully stirring, then the treated soybean protein dispersion is evenly divided into two parts; one part of the soybean protein dispersion is subjected to high-pressure homogenization treatment after heat denaturation; the other part is subjected to heat denaturation treatment after high-pressure homogenization treatment; and the treated parts are combined. The treatment method provided by the application increases the surface hydrophobicity of the protein, induces the formation of soluble aggregates, and finally improves the solubility and emulsifying properties, thereby providing important technical support for the industrial production of soybean protein with high solubility and high emulsifying properties.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of food processing, in particular relates to a method for improving the functional properties of soy protein by combining heat denaturation and high pressure homogenization. BACKGROUND

[0002] Soy protein isolate (SPI) contains more than 90% protein, mainly composed of globulin (11S) and concomitant glycinin (7S). Due to its excellent nutritional value and health benefits (containing physiological components beneficial to reducing cholesterol, hyperlipidemia and cardiovascular disease risk), SPI is widely used in food. However, due to its compact structure, soy protein usually exhibits poor functional properties. Therefore, proper SPI modification has the potential to improve its functional properties, especially its emulsification characteristics.

[0003] Physical treatment methods such as heat treatment and high pressure homogenization (HPH) have been widely applied in the industrial production of soy protein processing. HPH is a non-thermal technology widely used in the food industry to improve the emulsification properties of food proteins. HPH can induce the synthesis and destruction of chemical bonds and molecular interactions through the high shear force, turbulence and cavitation generated, thereby improving the functional properties of soy protein. Liu et al. also found that HPH treatment led to an increase in solubility, which resulted in protein aggregation at the oil-water interface, reducing the surface tension of the protein, thereby improving the emulsification. Bi et al. reported that HPH helped form a stable three-dimensional network structure in the gel, thereby improving the functionality of the emulsion gel. HPH reduced the particle size of hazelnut protein, increased the solubility, and improved the emulsification and rheological properties of the protein. In addition, heat treatment is one of the most common modification and pretreatment methods for proteins, which has been proven to be effective in improving emulsification capacity. Peng et al. studied the effect of heat treatment on the emulsification performance of pea protein and showed that heat treatment increased the protein adsorption rate in the protein emulsion, thereby improving the emulsification activity. Dissanayake and Vasiljevic showed that heat treatment unfolded some proteins, improving their interfacial properties, thereby improving emulsification. After heating soy protein to 95℃ for 30 minutes, the adsorption of protein at the oil / water interface was enhanced, significantly improving the emulsification performance.

[0004] Although heat treatment and HPH alone improve the functional properties of soy protein, their effects on protein structure are relatively limited. For example, high pressure treatment mainly affects non-covalent bonds such as hydrogen bonds, ionic bonds and hydrophobic interactions. HPH treatment will destroy or form these bonds, improving functional properties by changing hydrophobic groups. In contrast, heat treatment causes intense molecular motion, leading to the breaking or formation of covalent and non-covalent bonds. There is still limited research in the prior art on how the sequence of high pressure homogenization and heat treatment affects the conformation and emulsification properties of soy protein. SUMMARY

[0005] In view of the technical blank in the prior art, the application provides a method for improving the functional characteristics of soybean protein by combining heat denaturation and high-pressure homogenization.

[0006] The technical scheme adopted by the application to achieve the above-mentioned purpose is:

[0007] The application provides a method for improving the functional characteristics of soybean protein by combining heat denaturation and high-pressure homogenization, comprising the following steps:

[0008] (1) A soybean protein dispersion liquid is prepared at room temperature, the pH value is adjusted, and the soybean protein dispersion liquid is fully dispersed by fully stirring, and then the treated soybean protein dispersion liquid is evenly divided into two parts;

[0009] (2) One part of the soybean protein dispersion liquid is heated and then treated by heat preservation, and then high-pressure homogenization treatment is performed, and the temperature is cooled to room temperature;

[0010] (3) The other part of the soybean protein dispersion liquid is treated by high-pressure homogenization, and then heated and treated by heat preservation, and the temperature is cooled to room temperature;

[0011] (4) The two parts of the treated soybean protein dispersion liquid are combined.

[0012] Further, in step (1), the concentration of the soybean protein dispersion liquid prepared at room temperature is 4%-9% (w / v); the pH value is 7; and the stirring is stirring at 1000-2000 r / min for 30-60 min.

[0013] Further, in step (1), the pH value is adjusted by using 2 mol / L hydrochloric acid or 2 mol / L sodium hydroxide solution.

[0014] Further, in step (2), the heat preservation treatment is keeping at 90-100 DEG C for 5-15 min.

[0015] Further, in step (2), the high-pressure homogenization treatment is homogenized 1-2 times under the condition of 10-90 MPa.

[0016] Further, in step (3), the high-pressure homogenization treatment is homogenized 1-2 times under the condition of 10-90 MPa.

[0017] Further, in step (3), the heat preservation treatment is keeping at 90-100 DEG C for 5-15 min.

[0018] The application has the following beneficial effects:

[0019] (1) The treatment method provided by the application provides a new option for the industrialized manufacturing of high-emulsifying soybean protein;

[0020] (2) The processing method provided by the application increases the surface hydrophobicity of the protein, induces the formation of soluble aggregates, and finally improves the solubility and emulsification performance, thereby providing important technical support for the industrial production of high-solubility and high-emulsification soybean protein. DETAILED DESCRIPTION

[0021] The application will be further described in conjunction with the examples, but the protection scope of the application is not limited to the content described.

[0022] Example 1

[0023] (1) A soybean protein dispersion solution with a concentration of 7% (w / v) is prepared at room temperature, and the pH is adjusted to 7.0. The soybean protein dispersion solution is fully dispersed by stirring at 1500 r / min for 45 minutes using a mechanical stirrer, and then the soybean protein dispersion solution is evenly divided into two parts.

[0024] (2) One of the two parts of the soybean protein dispersion solution is heated to 90 DEG C and kept for 10 minutes, and then homogenized twice at 20 MPa, and cooled to room temperature.

[0025] (3) The other part of the soybean protein dispersion solution is first homogenized twice at 20 MPa, and then heated to 90 DEG C and kept for 10 minutes, and cooled to room temperature.

[0026] (4) The two parts of the treated soybean protein dispersion solution are combined.

[0027] Example 2

[0028] (1) A soybean protein dispersion solution with a concentration of 4% (w / v) is prepared at room temperature, and the pH is adjusted to 7.0. The soybean protein dispersion solution is fully dispersed by stirring at 1500 r / min for 30 minutes using a mechanical stirrer.

[0029] (2) The soybean protein dispersion solution is heated to 95 DEG C and kept for 15 minutes, and then homogenized twice at 50 MPa, and cooled to room temperature.

[0030] (3) The other part of the soybean protein dispersion solution is first homogenized twice at 50 MPa, and then heated to 95 DEG C and kept for 15 minutes, and cooled to room temperature.

[0031] (4) The two parts of the treated soybean protein dispersion solution are combined.

[0032] Example 3

[0033] (1) A soybean protein dispersion solution with a concentration of 9% (w / v) is prepared at room temperature, and the pH is adjusted to 7.0. The soybean protein dispersion solution is fully dispersed by stirring at 1500 r / min for 60 minutes using a mechanical stirrer.

[0034] (2) The soy protein dispersion solution was divided into two portions, one of which was heated to 90°C for 5 minutes and then homogenized once at 90 MPa. It was cooled to room temperature.

[0035] (3) The other portion was first homogenized once at 90 MPa and then heated to 90°C for 5 minutes and cooled to room temperature.

[0036] Comparative Example 1

[0037] (1) A soy protein dispersion solution having a concentration of 7% (w / v) was prepared at room temperature, and its pH was adjusted to 7.0 using 2 mol / L hydrochloric acid or 2 mol / L sodium hydroxide solution. It was stirred for 45 minutes at 1000-2000 r / min using a mechanical stirrer to achieve sufficient dispersion.

[0038] (2) The soy protein dispersion solution was first homogenized twice at 20 MPa and then heated to 90°C for 10 minutes and cooled to room temperature.

[0039] Comparative Example 2:

[0040] (1) A soy protein dispersion solution having a concentration of 4% (w / v) was prepared at room temperature, and its pH was adjusted to 7.0 using 2 mol / L hydrochloric acid or 2 mol / L sodium hydroxide solution. It was stirred for 30 minutes at 1000-2000 r / min using a mechanical stirrer to achieve sufficient dispersion.

[0041] (2) The soy protein dispersion solution was first homogenized twice at 50 MPa and then heated to 95°C for 15 minutes and cooled to room temperature.

[0042] Comparative Example 3

[0043] (1) A soy protein dispersion solution having a concentration of 9% (w / v) was prepared at room temperature, and its pH was adjusted to 7.0 using 2 mol / L hydrochloric acid or 2 mol / L sodium hydroxide solution. It was stirred for 60 minutes at 1000-2000 r / min using a mechanical stirrer to achieve sufficient dispersion.

[0044] (2) The soy protein dispersion solution was first homogenized once at 90 MPa and then heated to 90°C for 5 minutes and cooled to room temperature.

[0045] Effect Example

[0046] The products prepared in Examples 1-3 and Comparative Examples 1-3 were taken, and their solubility and emulsifiability were measured, respectively.

[0047] Solubility was determined according to the method provided in the literature "Structural and emulsifying properties of soy protein isolate subjected to acid and alkaline pH-shifting processes".

[0048] Emulsifying activity index and emulsion stability index were determined according to the method provided in the literature "Effect of enzymatic hydrolysis followed after extrusion pretreatment on the structure and emulsibility of soybean protein".

[0049] The results are reported in Table 1.

[0050] Table 1 Solubility and emulsifying properties of soy protein

[0051] .

Claims

1. A method for improving the functional properties of soy protein by combining heat denaturation with high pressure homogenization, characterized in that, The method comprises the following steps: (1) preparing a soybean protein dispersion at room temperature, adjusting pH value, fully stirring to make it fully dispersed, then evenly dividing the treated soybean protein dispersion into two parts; (2) heating one part of the soybean protein dispersion and then performing heat preservation treatment, then performing high-pressure homogenization treatment, and cooling to room temperature; (3) performing high-pressure homogenization treatment on the other part of the soybean protein dispersion, then heating and performing heat preservation treatment, and cooling to room temperature; (4) combining the two parts of the treated soybean protein dispersion; In step (1), the concentration of the soybean protein dispersion prepared at room temperature is 4%-9%, w / v; and the pH value is 7; In steps (2) and (3), the heat preservation treatment is performed at 90-100℃ for 5-15 minutes; In steps (2) and (3), the high-pressure homogenization treatment is performed 1-2 times under the condition of 10-90 MPa.

2. The method of claim 1, wherein, In step (1), the stirring is performed at 1000-2000 r / min for 30-60 min.

3. The method according to claim 1 or 2, characterized in that, In step (1), the pH value is adjusted by using 2 mol / L hydrochloric acid or 2 mol / L sodium hydroxide solution.