Method for improving emulsification of soybean protein isolate without heat treatment

Abstract

The application relates to a method for improving the emulsification of soybean protein isolate (SPI) by using cold plasma technology and synergistically modifying the emulsification of the soybean protein isolate (SPI) with chlorogenic acid, and belongs to the technical field of protein modification processing. The method comprises the following steps: (1) pretreatment of the soybean protein isolate (SPI); (2) cold plasma treatment of the soybean protein isolate (SPI); and (3) preparation of a modified SPI and chlorogenic acid (CA) composite solution. The modification method can greatly improve the emulsification of the soybean protein isolate (SPI) and promote diversified application of the soybean protein isolate (SPI) in the food industry.

Description

Technical Field

[0001] This invention relates to the field of protein modification technology, specifically to a method for improving the emulsifying properties of soy protein isolate by utilizing cold plasma in synergistic effect with chlorogenic acid. Background Technology

[0002] Soy protein isolate is a high-purity plant protein extracted and purified from soybeans. Its protein content typically exceeds 90% and contains all eight essential amino acids. It is widely used in meat product improvement, dairy product substitution, plant protein beverage preparation, and baked goods processing. Emulsifying properties, as the core functional characteristic of soy protein isolate, directly determine its application value in oil-containing food systems. Good emulsifying ability can effectively prevent food separation and improve the product's texture, consistency, and shelf-life stability. However, the emulsifying performance of natural soy protein isolate is limited by its compact globular molecular structure, insufficient exposure of hydrophobic groups on the surface, and uneven charge distribution. Under complex environmental conditions such as high temperature, high salt, and fluctuating pH, the emulsifying stability of the system is prone to decline. This deficiency makes it difficult to support the core requirements for protein functional properties in food processing.

[0003] Cold plasma technology is a highly promising low-temperature physical modification technique. It ionizes working gases such as air and nitrogen through dielectric barrier discharge, generating high-energy reactive particles such as electrons, ions, hydroxyl radicals, and ozone. These reactive particles can act on the protein surface at room temperature, altering the protein's surface morphology, molecular weight, and active group composition through etching, oxidation, and molecular chain breakage, thereby regulating its functional properties. Cold plasma treatment offers advantages such as high processing efficiency and no chemical reagent residue, making it one of the ideal modification techniques for achieving green and efficient protein functional regulation.

[0004] Chlorogenic acid is a polyphenol widely found in natural plants such as honeysuckle and eucommia. It possesses excellent antioxidant and anti-inflammatory biological activities and can interact with proteins through hydrogen bonds and hydrophobic interactions. Currently, the field of protein modification has seen the emergence of a synergistic modification approach combining physical techniques with natural active ingredients. However, research on the synergistic enhancement of the emulsifying properties of soy protein isolate using cold plasma and chlorogenic acid is still scarce. Therefore, strengthening its emulsifying performance through targeted modification techniques has become a crucial direction that urgently needs breakthrough. Summary of the Invention

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for improving the emulsifying properties of soy protein isolate without heat treatment includes the following steps:

[0007] (1) Pretreatment of soy protein isolate (SPI): Soy protein isolate was placed in a vacuum drying oven at 45~50 ℃ and dried for 1~3 h to remove moisture to constant weight. Then it was pulverized by a high-speed pulverizer and passed through an 80-mesh sieve to obtain soy protein isolate powder.

[0008] (2) Cold plasma treatment of SPI: The pretreated SPI is subjected to cold plasma treatment with a working voltage of 70~90 KV and a frequency of 45~60 HZ for 10~25 min, and the temperature is maintained at 20~35 ℃ during the treatment.

[0009] (3) Preparation of cold plasma modified SPI and chlorogenic acid (CA) composite solution: The modified SPI was dissolved in deionized water to prepare a protein solution with a mass fraction of 1-5%. Then, chlorogenic acid (CA) powder was added to make its concentration 60-100 μmol / mL. The solution was magnetically stirred for 30-40 min until completely dissolved. The pH of the mixed solution was adjusted to 6.5-7.5 using a 0.1 mol / L sodium hydroxide or hydrochloric acid solution. After the treatment, the modified protein solution was allowed to stand at 4 ℃ for 1-2 h to obtain a highly emulsifiable soy protein isolate.

[0010] More preferably, the working voltage in step (2) is 80~90 KV.

[0011] More preferably, the frequency in step (2) is 45~55 Hz.

[0012] More preferably, the processing time in step (2) is 15~25 min and the temperature is 20~30 ℃.

[0013] More preferably, the mass fraction of soy protein isolate (SPI) in step (3) is 1-3%.

[0014] More preferably, the concentration of chlorogenic acid (CA) in step (3) is 70~90 μmol / mL.

[0015] More preferably, the pH of the mixed solution in step (3) is adjusted to 6.8~7.2.

[0016] More preferably, the settling process in step (3) is carried out under sealed conditions.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention employs cold plasma non-thermal treatment technology, avoiding the damage to the nutritional value of soy protein isolate caused by traditional heat modification. Simultaneously, it features a short production cycle and no chemical reagent residues, ensuring product safety and meeting the demands of the modern food industry for green and safe processing technologies. It can better realize large-scale industrial production and has good application prospects and economic benefits.

[0019] 2. This invention constructs a composite system by combining physically modified soy protein isolate with chlorogenic acid. High-energy activated particles generated by cold plasma treatment act on the protein surface, providing a favorable foundation for the construction of the SPI-CA system and synergistically improving the emulsifying properties of soy protein isolate.

[0020] This invention provides a method for improving the emulsifying properties of soy protein isolate without heat treatment. Using soy protein isolate as raw material, a combination of cold plasma and chlorogenic acid complex system is used to significantly improve the emulsifying performance of soy protein isolate without destroying its nutritional value or leaving any chemical reagent residues. This method is characterized by its simple operation, low cost, and ease of industrial production. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating an embodiment of the present invention;

[0022] Figure 2 The results show the emulsifying activity and emulsifying stability of Experimental Example 1, Control Example 1, Control Example 2 and Control Example 3.

[0023] Depend on Figure 2 It can be seen that, compared with Control Examples 1, 2 and 3, the emulsifying activity and emulsifying stability of the modified SPI-CA composite solution prepared in Example 1 were improved by 2.47 times, 1.35 times and 1.55 times, respectively, and the emulsifying stability was improved by 4.12 times, 2.52 times and 1.71 times, respectively. Detailed Implementation

[0024] A method for improving the emulsifying properties of soy protein isolate without heat treatment includes the following steps:

[0025] (1) Pretreatment of soy protein isolate (SPI): Soy protein isolate was placed in a vacuum drying oven at 45~50 ℃ and dried for 1~3 h to remove moisture to constant weight. Then it was pulverized by a high-speed pulverizer and passed through an 80-mesh sieve to obtain soy protein isolate powder.

[0026] (2) Cold plasma treatment of SPI: The pretreated SPI is subjected to cold plasma treatment with a working voltage of 70~90 KV and a frequency of 45~60 HZ for 10~25 min, and the temperature is maintained at 20~35 ℃ during the treatment.

[0027] (3) Preparation of cold plasma modified SPI and chlorogenic acid (CA) composite solution: The modified SPI was dissolved in deionized water to prepare a protein solution with a mass fraction of 1-5%. Then, chlorogenic acid (CA) powder was added to make its concentration 60-100 μmol / mL. The solution was magnetically stirred for 30-40 min until completely dissolved. The pH of the mixed solution was adjusted to 6.5-7.5 using a 0.1 mol / L sodium hydroxide or hydrochloric acid solution. After the treatment, the modified protein solution was allowed to stand at 4 ℃ for 1-2 h to obtain a highly emulsifiable soy protein isolate.

[0028] In this invention, the working voltage in step (2) is 70~90 KV, preferably 80~90 KV, and more preferably 85 KV;

[0029] In this invention, the frequency in step (2) is 45~60 Hz, preferably 45~55 Hz, and more preferably 50 Hz;

[0030] In this invention, the processing time in step (2) is 10~25 min and the temperature is 20~35 ℃, preferably the processing time is 15~25 min and the solution temperature is 20~30 ℃, and more preferably the processing time is 20 min and the temperature is 25 ℃.

[0031] In this invention, the soybean protein isolate fraction in step (3) is 1-5%, preferably 1-3%, and more preferably 2%;

[0032] In this invention, the concentration of chlorogenic acid (CA) in step (3) is 60~100 μmol / mL, preferably 70~90 μmol / mL, and more preferably 80 μmol / mL;

[0033] In this invention, the pH value of the mixed solution in step (3) is adjusted to 6.5~7.5, preferably 6.8~7.2, and more preferably 7.0;

[0034] In this invention, it is further preferred that the settling process in step (3) is carried out under sealed conditions.

[0035] Unless otherwise specified, the following embodiments are all conventional methods.

[0036] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0037] All the following experiments were performed in triplicate, and the data are expressed as mean ± standard deviation.

[0038] Example 1

[0039] A method for improving the emulsifying properties of soy protein isolate without heat treatment includes the following steps:

[0040] (1) Pretreatment of soy protein isolate (SPI): Soy protein isolate was placed in a vacuum drying oven at 48 ℃ and dried for 2 hours to remove moisture to constant weight. Then it was pulverized by a high-speed pulverizer and passed through an 80-mesh sieve to obtain soy protein isolate powder.

[0041] (2) Cold plasma treatment of SPI: The pretreated SPI is subjected to cold plasma treatment at a working voltage of 85KV and a frequency of 50HZ for 20 min, and the temperature is maintained at 25℃ during the treatment.

[0042] (3) Preparation of cold plasma modified SPI and chlorogenic acid (CA) composite solution: The modified SPI was dissolved in deionized water to prepare a protein solution with a mass fraction of 2%. Then, chlorogenic acid (CA) was added to make its concentration 80 μmol / mL. The solution was magnetically stirred for 35 min until completely dissolved. The pH of the mixed solution was adjusted to 7.0 using a 0.1 mol / L sodium hydroxide or hydrochloric acid solution. After the treatment, the modified protein solution was allowed to stand at 4 ℃ for 1.5 h to obtain a highly emulsifiable soy protein isolate.

[0043] Soy protein isolate and soybean oil were mixed at a 3:1 (v / v) ratio and emulsified at 8000 rpm for 1 min using a high-speed homogenizer. Then, 50 μL of the emulsion was collected from 1 cm below the bottom of the core tube at 0 min and 10 min, respectively, and mixed with 1% SDS solution. After mixing, the absorbance was measured at 500 nm using a spectrophotometer. The emulsion activity index (EAI) and emulsion stability index (ESI) were calculated using the Eqs formula.

[0044]

[0045]

[0046] Where D is the emulsion dilution factor and C is the concentration of SPI (g / mL). A0 represents the proportion of the oil phase volume to the total emulsion volume, while A10 and A10 represent the absorbance at 0 min and 10 min after emulsification, respectively.

[0047] Compare with Example 1

[0048] Pretreatment of soy protein isolate powder: Soy protein isolate was dried in a vacuum drying oven at 48 ℃ for 2 h to remove moisture to constant weight. It was then pulverized using a high-speed pulverizer and passed through an 80-mesh sieve to obtain soy protein isolate powder. Preparation of soy protein isolate solution: The pretreated soy protein isolate powder was dissolved in deionized water and magnetically stirred for 35 min until completely dissolved (mass fraction 2%). The pH of the solution was adjusted to 7.0 using a 0.1 mol / L sodium hydroxide and 0.1 mol / L hydrochloric acid solution. The pH-adjusted SPI solution was allowed to stand at 4 ℃ for 1.5 h to obtain the original pure SPI solution.

[0049] Soy protein isolate and soybean oil were mixed at a 3:1 (v / v) ratio and emulsified at 8000 rpm for 1 min using a high-speed homogenizer. Then, 50 μL of the emulsion was collected from 1 cm below the bottom of the core tube at 0 min and 10 min, respectively, and mixed with 1% SDS solution. After mixing, the absorbance was measured at 500 nm using a spectrophotometer. The emulsion activity index (EAI) and emulsion stability index (ESI) were calculated using the Eqs formula.

[0050]

[0051]

[0052] Where D is the emulsion dilution factor, C is the concentration of SPI (g / mL), 𝜑 is the proportion of the oil phase volume to the total emulsion volume, and A0 and A10 are the absorbance at 0 min and 10 min after emulsification, respectively.

[0053] Compare with Example 2

[0054] (1) Pretreatment of soy protein isolate (SPI): Soy protein isolate was placed in a vacuum drying oven at 48 ℃ and dried for 2 hours to remove moisture to constant weight. Then it was pulverized by a high-speed pulverizer and passed through an 80-mesh sieve to obtain soy protein isolate powder.

[0055] (2) Cold plasma treatment of SPI: The pretreated SPI is subjected to cold plasma treatment at a working voltage of 85KV and a frequency of 50HZ for 20 min, and the temperature is maintained at 25℃ during the treatment.

[0056] (3) Cold plasma-treated soy protein isolate powder was dissolved in deionized water and magnetically stirred for 35 min until completely dissolved (mass fraction 2%). The pH of the solution was adjusted to 7.0 using a 0.1 mol / L sodium hydroxide and a 0.1 mol / L hydrochloric acid solution. The pH-adjusted SPI solution was allowed to stand at 4 ℃ for 1.5 h to obtain the cold plasma-treated SPI solution.

[0057] Soy protein isolate and soybean oil were mixed at a 3:1 (v / v) ratio and emulsified at 8000 rpm for 1 min using a high-speed homogenizer. Then, 50 μL of the emulsion was collected from 1 cm below the bottom of the core tube at 0 min and 10 min, respectively, and mixed with 1% SDS solution. After mixing, the absorbance was measured at 500 nm using a spectrophotometer. The emulsion activity index (EAI) and emulsion stability index (ESI) were calculated using the Eqs formula.

[0058]

[0059]

[0060] Where D is the emulsion dilution factor and C is the concentration of SPI (g / mL). It is the ratio of the oil phase volume to the total emulsion volume in the emulsion, A0 and A 10 These are the absorbance values ​​at 0 min and 10 min after emulsification, respectively.

[0061] Compare with Example 3

[0062] (1) Pretreatment of soy protein isolate (SPI): Soy protein isolate was placed in a vacuum drying oven at 48 ℃ and dried for 2 hours to remove moisture to constant weight. Then it was pulverized by a high-speed pulverizer and passed through an 80-mesh sieve to obtain soy protein isolate powder.

[0063] (2) The pretreated SPI was dissolved in deionized water to prepare a 2% (w / w) protein solution. Chlorogenic acid (CA) was then added to achieve a concentration of 80 μmol / mL. The solution was magnetically stirred for 35 min until completely dissolved. The pH of the mixed solution was adjusted to 7.0 using a 0.1 mol / L sodium hydroxide or hydrochloric acid solution. After treatment, the modified protein solution was allowed to stand at 4 °C for 1.5 h to obtain the SPI-CA solution.

[0064] Soy protein isolate and soybean oil were mixed at a 3:1 (v / v) ratio and emulsified at 8000 rpm for 1 min using a high-speed homogenizer. Then, 50 μL of the emulsion was collected from 1 cm below the bottom of the core tube at 0 min and 10 min, respectively, and mixed with 1% SDS solution. After mixing, the absorbance was measured at 500 nm using a spectrophotometer. The emulsion activity index (EAI) and emulsion stability index (ESI) were calculated using the Eqs formula.

[0065]

[0066]

[0067] Where D is the emulsion dilution factor and C is the concentration of SPI (g / mL). It is the ratio of the oil phase volume to the total emulsion volume in the emulsion, A0 and A 10 These are the absorbance values ​​at 0 min and 10 min after emulsification, respectively.

Claims

1. A method for improving the emulsifying properties of soy protein isolate without heat treatment, characterized in that, Includes the following steps: (1) Pretreatment of soy protein isolate (SPI): Soy protein isolate was placed in a vacuum drying oven at 45~50 ℃ and dried for 1~3 h to remove moisture to constant weight. Then it was pulverized by a high-speed pulverizer and passed through an 80-mesh sieve to obtain soy protein isolate powder. (2) Cold plasma treatment of SPI: The pretreated SPI is subjected to cold plasma treatment with a working voltage of 70~90KV and a frequency of 45~60 HZ for 10~25 min, and the temperature is maintained at 20~35 ℃ during the treatment. (3) Preparation of cold plasma modified SPI and chlorogenic acid (CA) composite solution: SPI was dissolved in deionized water to prepare a protein solution with a mass fraction of 1-5%, and then chlorogenic acid (CA) was added to make its concentration 60-100 μmol / mL. The solution was magnetically stirred for 30-40 min until completely dissolved. The pH of the mixed solution was adjusted to 6.5-7.5 using a 0.1 mol / L sodium hydroxide or hydrochloric acid solution. After the treatment, the modified protein solution was allowed to stand at 4 ℃ for 1-2 h to obtain a highly emulsifiable soy protein isolate.

2. The method for improving the emulsifying properties of soy protein isolate without heat treatment according to claim 1, characterized in that, The operating voltage mentioned in step 2 is 80~90 kV.

3. The method for improving the emulsifying properties of soy protein isolate without heat treatment according to claim 1, characterized in that, The frequency mentioned in step 2 is 45~55 Hz.

4. The method for improving the emulsifying properties of soy protein isolate without heat treatment according to claim 1, characterized in that, The processing time in step 2 is 15-25 minutes, and the temperature is 20-30 ℃.

5. The method for improving the emulsifying properties of soy protein isolate without heat treatment according to claim 1, characterized in that, The soybean protein isolate in step 3 has a protein content of 1-3%.

6. The method for improving the emulsifying properties of soy protein isolate without heat treatment according to claim 1, characterized in that, The concentration of chlorogenic acid (CA) in step 3 is 70~90 μmol / mL.

7. The method for improving the emulsifying properties of soy protein isolate without heat treatment according to claim 1, characterized in that, The pH of the mixed solution in step 3 is adjusted to 6.8-7.

2.

8. The method for improving the emulsifying properties of soy protein isolate without heat treatment according to claim 1, characterized in that, The settling process described in step 3 is carried out under sealed conditions.

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