Suitably protein oxidized linoleic acid-rich bean-based nutrition powder as well as preparation method and application thereof

Abstract

The invention discloses moderate protein oxidized linoleic acid-rich bean-based nutrition powder as well as a preparation method and application thereof, and belongs to the technical field of bean product processing. According to the method, soybean milk and linoleic acid are mixed and then moderately heated, and a cold plasma technology is combined to moderately oxidize soybean flour and improve the solubility and the oxidation resistance during digestion, so that the functional characteristics and the nutritional value of the soybean-based nutritional powder are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of bean product processing, and in particular relates to a moderately protein-oxidized bean-based nutritional powder rich in linoleic acid, and a preparation method and application thereof. Background Art

[0002] Soy milk is also called soy milk or soy milk beverage. Soy milk is rich in nutrition and plant protein. It can provide the body with the necessary protein and energy for human life activities. It is rich in B vitamins and helps the body's normal metabolism. It also contains other ingredients such as plant amino acids, which can lower cholesterol and improve neurasthenia. Nowadays, soy milk has been sold overseas with its excellent quality, unique taste and excellent nutritional value.

[0003] At present, most soy milk products on the market are products with reduced sugar content, such as pumpkin powder, which is mixed into soy milk as a product auxiliary material. Or there are more developments on instant soy-based nutritional powders. Although these soy-based nutritional powder products have good functionality, nutrition and delicious taste, their efficacy is not comprehensive and their shelf life is short.

[0004] Linoleic acid is a polyunsaturated fatty acid belonging to the omega-3 fatty acid series. It is mainly found in flaxseed oil, flaxseed and some other plant foods. Linoleic acid is beneficial to human health and has anti-inflammatory, blood pressure lowering, blood lipid lowering, and cardiovascular health improvement effects. However, linoleic acid itself undergoes lipid peroxidation, and the resulting ROS free radicals and active oxidation products attack the protein main chain and amino acid side chains. Active oxygen free radicals such as •OH capture hydrogen atoms from protein molecules to form alkyl free radicals (C•) and generate alkane peroxide free radicals (COO•) in the presence of O2. They are converted into peroxide alkyl (COOH) through hydrogenation or protonation reactions and further react with superoxide free radicals (HO2•) in the system to form alkoxy free radicals (CO•). At this time, the alkoxy free radicals of the main peptide chain are prone to peptide chain cleavage through α-amidation and diamide pathways, thereby generating hydroxyl derivatives, ammonia, carboxylic acid derivatives and polypeptide fragments, causing oxidative cleavage of the main peptide chain of the protein.

[0005] Cold plasma (CP) is the fourth state of matter, consisting of a series of substances such as charged particles, ultraviolet photons, free radicals, reactive oxygen species (ROS) and reactive nitrogen species (RNS) generated by ionized gas atoms. Cold plasma has no local thermodynamic equilibrium due to its relatively low pressure and power. In addition, the existing technologies on the market all use cold plasma to directly modify proteins, and there are no reports on the treatment of combining cold plasma with nutrients such as linoleic acid to modify proteins. Summary of the invention

[0006] To address the above problems, the present invention provides a moderately protein-oxidized linoleic acid-rich soy-based nutritional powder, its preparation method, and application. Its good antioxidant properties, digestibility, and high nutritional value are suitable for various populations and have good market prospects.

[0007] The present invention provides a method for preparing a moderately protein-oxidized linoleic acid-rich soy-based nutritional powder, comprising the following steps: Add linoleic acid to soymilk, and perform combined heating and cold plasma treatment. After homogenization, concentration, and drying, a moderately protein-oxidized linoleic acid-rich soy-based nutritional powder is obtained; The addition amount of linoleic acid is 7-10%; the heating temperature is 40-50 °C, and the heating time is 15-20 min; when performing cold plasma treatment, the voltage is 10-18 KV, the treatment time is 90-150 min, and the power is 45-55 W.

[0008] Among them, 7-10% refers to the volume percentage of linoleic acid to soymilk, that is, 7-10 ml of linoleic acid is added to 100 ml of soymilk. The soymilk is obtained by mixing soy flour and water (the mass ratio of soy flour to water is 1:9-11) and steaming at 90-110 °C for 25-35 min.

[0009] In a preferred embodiment, the aforementioned preparation method comprises the following steps: 1) Prepare soy flour, form soymilk, and add honey, xanthan gum, sodium polyacrylate, lecithin, and vanilla syrup; 2) Add linoleic acid and perform combined heating and cold plasma treatment to obtain treated soymilk; 3) After homogenization, concentration, and drying, a moderately protein-oxidized linoleic acid-rich soy-based nutritional powder is obtained.

[0010] The steps for preparing soy flour are as follows: Mix soybeans and water at a mass ratio of 1:9-11, soak for 10-14 h, and repeat changing water 2-4 times to wash the soybeans (soak the soybeans in water for 10-14 h each time after changing water); use a blender at 20000-40000 r / min to grind the soybeans into powder to obtain soy flour.

[0011] The process of forming soymilk is as follows: Mix soy flour and water at a mass ratio of 1:9-11, steam at 90-110 °C for 25-35 min, and continuously stir to form soymilk; filter to separate the soymilk and residues; adjust the pH of the soymilk to 6.0-6.5. Under this pH condition, the soymilk is relatively stable and has a good taste.

[0012] In a preferred embodiment, 4 - 6 wt% of honey, 0.05 - 0.15 wt% of xanthan gum, 0.05 - 0.2 wt% of sodium polyacrylate, 0.03 - 0.07 wt% of lecithin, and 0.5 - 1.5 wt% of vanilla syrup are added to soy milk; more preferably, 5 wt% of honey, 0.1 wt% of xanthan gum, 0.1 wt% of sodium polyacrylate, 0.05 wt% of lecithin, and 1 wt% of vanilla syrup are added. Honey and vanilla syrup provide sweetness and aroma, xanthan gum and sodium polyacrylate increase viscosity and stability, and lecithin prevents oil - water separation, making the soy powder finer and smoother. The synergistic effect of xanthan gum and sodium polyacrylate, as well as the emulsifying property of lecithin, can effectively prevent the deterioration and separation of soy powder during storage and use. The percentages in this paragraph are: the mass percentages of each component and soy milk. The soy milk is obtained by mixing soy powder and water (the mass ratio of soy powder to water is 1:9 - 11) and then steaming at 90 - 110 °C for 25 - 35 min, that is, 4 - 6 g of honey, 0.05 - 0.15 g of xanthan gum, 0.05 - 0.2 g of sodium polyacrylate, 0.03 - 0.07 g of lecithin, and 1 g of vanilla syrup are added to 100 g of soy milk.

[0013] During homogenization, two - stage homogenization is adopted. The first - stage high - pressure homogenization sets the homogenization pressure at 20 - 30 MPa and the treatment time at 5 - 10 minutes; the second - stage low - pressure homogenization sets the homogenization pressure at 10 - 15 MPa and the treatment time at 3 - 5 minutes; more preferably, the first - stage high - pressure homogenization sets the homogenization pressure at 25 MPa and the treatment time at 8 minutes; the second - stage low - pressure homogenization sets the homogenization pressure at 12 MPa and the treatment time at 4 minutes.

[0014] During concentration, the vacuum degree is 82.6 - 98.6 KPa and the temperature is 45 - 55 °C; more preferably, the vacuum degree is 90.6 KPa, the temperature is 50 °C, and the steam pressure is less than 196 KPa.

[0015] Low - temperature spray drying is adopted. The inlet air temperature is set at 150 - 170 °C, the outlet air temperature is controlled at 80 - 90 °C, the feed concentration is adjusted to 25 - 40%, and the feed concentration refers to the mass fraction of the solid components in the treated soy milk. The atomization speed is in the range of 250 - 300 r / s; more preferably, the inlet air temperature is set at 160 °C, the outlet air temperature is controlled at 85 °C, the feed concentration is adjusted to 30%, the feed concentration refers to the mass fraction of the solid components in the treated soy milk, and the atomization speed is 270 r / s.

[0016] The present invention also discloses a moderately protein - oxidized soy - based nutritional powder rich in linoleic acid prepared by the aforementioned preparation method.

[0017] The present invention also provides the application of the aforementioned preparation method in the preparation of a soy - based nutritional powder rich in linoleic acid.

[0018] More specifically, the preparation method of the present invention includes the following steps: The soybeans are soaked in water (mass ratio of 1:9 - 11) for 12 - 14 h, and the water is changed 2 - 4 times repeatedly to wash the soybeans (after each water change, the soybeans are soaked in water for 12 - 14 h). With a long soaking time, the soybeans absorb water and swell, the cell structure becomes loose, and components such as proteins are more easily dissolved, thereby increasing the yield rate of soymilk.

[0019] Put the washed soybeans into a wall breaker and process them at 20000 - 40000 r / min for 2 - 3 min to dry - grind the soybeans into a powder.

[0020] Cook the soybean powder with added water at 90 - 110 °C for 25 - 35 min, stirring constantly to form soymilk.

[0021] Filter and separate the soymilk and residues through a 200 - mesh sieve.

[0022] Adjust the pH of the soymilk to 6.0 - 6.5 with acetic acid or sodium hydroxide.

[0023] Add 4 - 6 wt% of honey, 0.05 - 0.15 wt% of xanthan gum, 0.05 - 0.2 wt% of sodium polyacrylate, 0.03 - 0.07 wt% of lecithin, and 0.5 - 1.5 wt% of vanilla syrup.

[0024] Add 7 - 10% of linoleic acid and carry out heat - combined cold plasma treatment. Heating temperature: 40 - 50 °C, heating time: 15 - 20 min. During the cold plasma treatment, voltage: 10 - 18 KV, treatment time: 90 - 150 min. After adding linoleic acid, heating and cold plasma treatment are carried out simultaneously, but the heating time is less than the cold plasma treatment time.

[0025] Perform secondary homogenization. The first - stage high - pressure homogenization sets the homogenization pressure at 20 - 30 MPa and the treatment time at 5 - 10 minutes; the second - stage low - pressure homogenization sets the homogenization pressure at 10 - 15 MPa and the treatment time at 3 - 5 minutes.

[0026] Concentrate the soymilk. Vacuum degree: 82.6 - 98.6 KPa, temperature: 45 - 55 °C, steam pressure less than 196 KPa.

[0027] Perform low - temperature spray drying. The inlet air temperature is set at 150 - 170 °C, the outlet air temperature is controlled at about 80 - 90 °C, the feed concentration is adjusted to 25 - 40 wt%, and the atomization rotation speed is in the range of 250 - 300 r / s.

[0028] Package the finished product.

[0029] Compared with the prior art, the beneficial effects of the present invention: The combination of heat-induced linoleic acid and cold plasma treatment, under the same degree of oxidation, results in a better solubility and antioxidant performance of the prepared soy-based nutritional powder compared to the soy-based nutritional powder treated with only heat-induced linoleic acid or only cold plasma treatment. This indicates that the heat-induced linoleic acid and cold plasma treatment can synergistically modify soy protein under certain conditions such as concentration and process parameters, thereby improving the solubility and antioxidant performance of the soy-based nutritional powder.

[0030] The reasons for the improvement of the antioxidant property of the soy powder by the combination of heat-induced linoleic acid and cold plasma treatment include: Cold plasma treatment can further enhance the antioxidant effect of linoleic acid by activating the antioxidant defense mechanism within cells, such as the Nrf2 pathway. In addition, various active substances generated by cold plasma treatment, such as reactive oxygen species (ROS), free radicals, ultraviolet photons, etc., can react with linoleic acid to generate oxidation products with specific functions, and these oxidation products have stronger antioxidant capabilities. Moreover, cold plasma treatment helps to retain or increase the antioxidant components in the soy powder, such as polyphenols, flavonoids, etc., and these components can synergistically act with the oxidation products of linoleic acid to further improve the antioxidant ability.

[0031] Cold plasma treatment generates almost no heat, which can be combined well with heat treatment to avoid the adverse effects of secondary heating on the proteins in the soy powder. The present invention effectively improves the nutritional value of the soy powder and provides high-quality protein for the human body. Description of the Drawings

[0032] Figure 1 It is the carbonyl content diagram of Examples 1-3 and Comparative Examples 1-5; Figure 2 It is the free sulfhydryl content diagram of Examples 1-3 and Comparative Examples 1-5; Figure 3 It is the solubility schematic diagram of Examples 1-3 and Comparative Examples 1-5; Figure 4 It is the DPPH diagram of Examples 1-3 and Comparative Examples 1-4; Figure 5 It is the ABTS diagram of Examples 1-3 and Comparative Examples 1-4. Detailed Embodiments

[0033] The following further illustrates the present invention with specific examples, but the present invention is not limited by the examples. All chemical reagents used in the experiments were purchased through commercial channels.

[0034] The cold plasma described herein is dielectric barrier discharge (DBD) cold plasma, with helium as the working medium and a power of 50W.

[0035] Example 1

[0036] The preparation method of a moderately protein-oxidized soybean-based nutritional powder rich in linoleic acid is as follows: The mass ratio of soybean to water is 1:10. Soak for 12 h, change water twice, soak for 12 h each time after changing water, and wash the soybean.

[0037] Put the washed soybean into a wall breaker and process at 30000 r / min for 2 min to grind the soybean into powder.

[0038] After mixing the soybean powder with water (the mass ratio of soybean powder to water is 1:10), cook at 100 °C for 30 min with continuous stirring to form soymilk.

[0039] Filter and separate the soymilk and residues through a 200-mesh sieve.

[0040] Adjust the pH of the soymilk to 6.5 with acetic acid or sodium hydroxide.

[0041] Add 5% honey, 0.1% xanthan gum, 0.1% sodium polyacrylate, 0.05% lecithin, and 1% vanilla syrup.

[0042] Add 8% linoleic acid and perform heat combined with cold plasma treatment. Heating temperature: 45 °C, heating time: 15 min. Voltage: 14 KV, time: 120 min.

[0043] Perform secondary homogenization. The first-stage high-pressure homogenization sets the homogenization pressure at 25 MPa and the treatment time at 8 minutes; the second-stage low-pressure homogenization sets the homogenization pressure at 12 MPa and the treatment time at 4 minutes.

[0044] Concentrate the soymilk. Vacuum degree: 90.6 KPa, temperature is 50 °C, and the steam pressure is less than 196 KPa.

[0045] Perform low-temperature spray drying. Set the inlet air temperature at 160 °C, control the outlet air temperature at 85 °C, adjust the feed concentration to 30 wt%, and the atomization speed is 270 r / s.

[0046] Package the finished product.

[0047] Example 2

[0048] The preparation method of a moderately protein-oxidized soybean-based nutritional powder rich in linoleic acid is as follows: 1) The mass ratio of soybean to water is 1:9. Soak for 12 h, change water twice, soak for 12 h each time after changing water, and wash the soybean.

[0049] 2) Put the washed soybean into a wall breaker and process at 25000 r / min for 3 min to grind the soybean into powder.

[0050] 3) Mix the soybean powder with water (the mass ratio of soybean powder to water is 1:9), and cook at 100 °C for 30 min while stirring continuously to form soymilk.

[0051] 4) Filter and separate the soymilk and residues through a 200-mesh sieve.

[0052] 5) Adjust the pH of the soymilk to 6.0 with acetic acid or sodium hydroxide.

[0053] 6) Add 4% honey, 0.15% xanthan gum, 0.15% sodium polyacrylate, 0.05% lecithin, and 1% vanilla syrup.

[0054] 7) Add 7% linoleic acid and perform heat treatment combined with cold plasma. Heating temperature: 50 °C, heating time: 15 min. Voltage: 16 KV, time: 90 min.

[0055] 8) Perform secondary homogenization. Set the homogenization pressure of the first-stage high-pressure homogenization to 20 MPa and the treatment time to 5 minutes; set the homogenization pressure of the second-stage low-pressure homogenization to 10 MPa and the treatment time to 3 minutes.

[0056] 9) Concentrate the soymilk. Vacuum degree: 82.6 KPa, temperature: 45 °C, steam pressure less than 196 KPa.

[0057] 10) Perform low-temperature spray drying. Set the inlet air temperature to 170 °C, control the outlet air temperature at 90 °C, adjust the feed concentration to 40 wt%, and the atomization speed to 250 r / s.

[0058] 11) Package the finished product.

[0059] Example 3

[0060] The preparation method of a moderately protein-oxidized linoleic acid-rich soybean-based nutritional powder is as follows: 1) The mass ratio of soybean to water is 1:11. Soak for 12 h, repeat changing water 2 times, soak for 12 h each time after changing water, and wash the soybeans.

[0061] 2) Put the washed soybeans into a wall breaker and process at 40000 r / min for 2 min to grind the soybeans into powder.

[0062] 3) Mix the soybean powder with water (the mass ratio of soybean powder to water is 1:11), and cook at 100 °C for 30 min while stirring continuously to form soymilk.

[0063] 4) Filter and separate the soymilk and residues through a 200-mesh sieve.

[0064] 5) Adjust the pH of the soymilk to 6.3 with acetic acid or sodium hydroxide.

[0065] 6) Add 5% honey, 0.1% xanthan gum, 0.1% sodium polyacrylate, 0.06% lecithin, and 1.5% vanilla syrup.

[0066] 7) Add 9% linoleic acid and perform combined heating and cold plasma treatment. Heating temperature: 40 °C, heating time: 20 min. Voltage: 10 KV, time: 150 min.

[0067] 8) Perform secondary homogenization. The first-stage high-pressure homogenization is set with a homogenization pressure of 30 MPa and a treatment time of 10 minutes; the second-stage low-pressure homogenization is set with a homogenization pressure of 15 MPa and a treatment time of 5 minutes.

[0068] 9) Concentrate the soymilk. Vacuum degree: 98.6 KPa, temperature is 55 °C, and the steam pressure is less than 196 KPa.

[0069] 10) Perform low-temperature spray drying. The inlet air temperature is set at 160 °C, the outlet air temperature is controlled at 85 °C, the feed concentration is adjusted to 25 wt%, and the atomization rotation speed is 300 r / s.

[0070] 11) Package the finished product.

[0071] Comparative Example 1 Compared with Example 1, step 7) is modified as follows: Add 8% linoleic acid, do not heat, and keep for 15 min. Others are the same as in Example 1.

[0072] Comparative Example 2 Compared with Example 1, step 7) is modified as follows: Add 8% linoleic acid and perform heating treatment; heating temperature: 45 °C, heating time: 15 min. Others are the same as in Example 1.

[0073] Comparative Example 3 Compared with Example 1, step 7) is modified as follows: Do not add linoleic acid and do not heat, only perform cold plasma treatment, cold plasma voltage is 14 KV, time: 120 min. Others are the same as in Example 1.

[0074] Comparative Example 4 Compared with Example 1, omit step 7). Others are the same as in Example 1.

[0075] Comparative Example 5 Compared with Example 1, step 7) is modified as follows: Add 12% linoleic acid and perform combined heating and cold plasma treatment. Heating temperature: 45 °C, heating time: 30 min. Voltage: 22 KV, time: 200 min.

[0076] Example 4

[0077] Carbonyl determination Test samples: Soy-based nutritional powders prepared in Examples 1-3 and Comparative Examples 1-5.

[0078] Test method: Dilute the sample concentration to 5 mg / ml with phosphate buffer (20 mmol / L, pH 6.0). Take two 0.8 mL sample solutions and put them into 5 mL centrifuge tubes. Take one portion as the treatment group and add 1600 μL of DNPH solution containing 2 mol / L (0.2%, w / v) HCl; the other group is the blank group and add 1600 μL of HCl solution (2 mol / l). React at room temperature for 30 min, add 800 μL of trichloroacetic acid (40%, w / v) to precipitate the protein. Then centrifuge (5000 g, 4 °C, 5 min). After removing the supernatant, wash the precipitate three times with 2 mL of ethanol-ethyl acetate mixture (1:1). Wash with 3 ml of 20 mmol / L phosphate buffer containing 6 mol / L guanidine hydrochloride and pH 6.5 to completely dissolve the precipitate, measure the absorbance at 370 nm, and calculate the protein carbonyl content according to the molar extinction coefficient (22,000 mmol -1 ·L·cm -1 ).

[0079] Figure 1 Figure of carbonyl content for Examples 1-3 and Comparative Examples 1-5. As Figure 1 , the carbonyl content of Comparative Example 5 is the highest, being 9 nmol / mg. The carbonyl content of Comparative Example 4 is the lowest, being 3 nmol / mg. The carbonyl contents of Examples 1, 2, and 3 are moderate, being about 7.5 nmol / mg. This shows that the degree of oxidation of soy protein in Examples 1, 2, and 3 is moderate. The addition of linoleic acid can serve as a substrate for lipoxygenase to generate a large amount of free radicals and lipid oxides; among them, free radicals can attack the side chains (especially Pro, Arg, Thr, Lys, etc.) or the main chain of proteins, resulting in an increase in the protein carbonyl content. In addition, during cold plasma treatment, some introduced free radicals can also attack the protein side chains, causing protein oxidation. After cold plasma meets lipoxygenase, its activity will be reduced, and the combined use of linoleic acid and cold plasma at appropriate concentrations and conditions will not cause excessive protein oxidation.

[0080] Example 5

[0081] Determination of free sulfhydryl groups Test samples: Soy-based nutritional powders prepared in Examples 1-3 and Comparative Examples 1-5.

[0082] Test method: Add 1 ml of sample solvent to 5 ml of Tris-Gly, then add 40 μl of DTNB (4 mg / ml), and react in the dark at room temperature for 30 min. Measure the absorbance of the reactant at 412 nm using a UV-visible spectrophotometer. Use the reactant without DTNB as the control group. Lipid oxidation generates ROS, extracts hydrogen atoms from the sulfhydryl groups of cysteine, causes protein cross-linking, and reduces the sulfhydryl content.

[0083] C SH = 73.53 × A 412 × D / C C SH is the free sulfhydryl content (μmol / mg).

[0084] A 412 is the absorbance value of the sample at 412 nm.

[0085] D is the dilution factor.

[0086] C is the protein concentration of the sample (mg / mL) Figure 2 is the free sulfhydryl content graph of Examples 1-3 and Comparative Examples 1-5. As Figure 2 , the free sulfhydryl content of Comparative Example 5 is the lowest, at 4.2 μmol / mg. The free sulfhydryl content of Comparative Example 4 is the highest, at 13 μmol / mg. The free sulfhydryl contents of Examples 1, 2, and 3 are moderate, at about 6 μmol / mg, indicating a moderate degree of oxidation.

[0087] Example 6

[0088] Solubility determination Test samples: Soy-based nutritional powders prepared in Examples 1-3 and Comparative Examples 1-5.

[0089] Test method: Prepare a 1 mg / ml solution with phosphate buffer (10 mmol / L, pH 7.4). Use the BCA method to determine the protein content in the supernatant. Dissolve the sample solution with 2 mol / l NaOH and determine the total protein content.

[0090] Solubility (%) = N1 / N0 × 100 N0: Total protein content.

[0091] N1: Protein content in the supernatant. Unit: mg / ml.

[0092] Figure 3Solubility diagrams for Examples 1-3 and Comparative Examples 1-5. The solubility of proteins is closely related to their functional properties. Compared with Comparative Examples 1-5, the solubilities of Examples 1, 2, and 3 are relatively high, at 82%, 80%, and 79% respectively, indicating that moderate oxidation caused by heating linoleic acid in combination with cold plasma is beneficial to the improvement of protein solubility. The solubility of Comparative Example 4 is the lowest, at 42%, indicating that the solubility of soy protein without any treatment is much lower than that of soy protein treated with heating linoleic acid in combination with cold plasma. The solubility of Comparative Example 5 is lower than that of the Examples, indicating that excessive oxidation degree causes a decrease in solubility.

[0093] In addition, the solubility of chickpea nutritional powder treated with heating linoleic acid in combination with cold plasma (prepared in the same way as Example 1, with only soybeans replaced by chickpeas during preparation) is 68%, which is lower than the solubility of soy protein under this treatment. This experiment shows that treating with heating linoleic acid in combination with cold plasma increases the solubility of soy protein, which is beneficial to the utilization of soy milk powder.

[0094] Example 7

[0095] Determination of antioxidant properties Test samples: Sample solutions after in vitro intestinal digestion of the soy-based nutritional powders prepared in Examples 1-3 and Comparative Examples 1-4, and sample solutions after in vitro intestinal digestion of chickpea nutritional powder treated with heating linoleic acid in combination with cold plasma.

[0096] Test method: The sample solution after in vitro intestinal digestion (0.5 mg / ml, 2 ml) is incubated with an equal volume of DPPH solution (0.08 mmol / L) in the dark at 25 °C for 30 min. The absorbance of the resulting solution is measured at a wavelength of 517 nm. The DPPH radical scavenging rate (%) = [1 - (A i -A j ) / A c ] × 100%. A i : Absorbance of the sample solution after adding DPPH. A j : Absorbance of the sample solution. A c : Absorbance of the DPPH solution.

[0097] 7 mmol / L ABTS and 2.45 mmol / L potassium persulfate are added to 4 ml of deionized water and diluted 40 times in the dark for 8 - 12 hours to obtain the ABTS solution. 4 ml of the ABTS solution is mixed with 50 μl of the sample solution in the dark for 10 min. The absorbance of the resulting solution is measured at a wavelength of 734 nm. Deionized water is used as the blank. The ABTS radical scavenging rate (%) = [1 - (A i -A j ) / A c ] × 100%. Ai : Absorbance of the sample solution after adding ABTS. A j : Absorbance of the sample solution. A c : Absorbance of the ABTS solution.

[0098] Figure 4 Figure showing the DPPH radical scavenging rates of Examples 1 - 3 and Comparative Examples 1 - 4. Compared with Comparative Examples 1 - 4, the DPPH values (i.e., DPPH radical scavenging rates) of Examples 1, 2, and 3 are high, being 78%, 76%, and 75% respectively, indicating that moderate oxidation caused by heating linoleic acid in combination with cold plasma is beneficial to the increase of the DPPH value of proteins. The DPPH value of Comparative Example 4 is the lowest, being 44%, indicating that the DPPH value of soy protein without any treatment is much smaller than that of soy protein treated with heating linoleic acid in combination with cold plasma.

[0099] Figure 5 Figure showing ABTS of Examples 1 - 3 and Comparative Examples 1 - 4. The ABTS value (i.e., ABTS radical scavenging rate) of Example 1 is the highest, being 69%. The ABTS values of Examples 1, 2, and 3 are close, being 69%, 68%, and 67.5% respectively. The ABTS value of Comparative Example 4 is the lowest, being 30%, indicating that the ABTS value of soy protein without any treatment is much smaller than that of soy protein treated with heating linoleic acid in combination with cold plasma.

[0100] Among them, for soy protein, after being treated with heating linoleic acid in combination with cold plasma (Example 1), compared with soy protein without any treatment (Comparative Example 4), its DPPH and ABTS values increased by 34% and 39% respectively (the data of Example 1 minus the data of Comparative Example 4). For chickpea protein, after being treated with heating linoleic acid in combination with cold plasma (soybean in Example 1 was replaced with chickpea, and the preparation process was referred to that described in Example 1), compared with chickpea protein without any treatment (soybean in Comparative Example 4 was replaced with chickpea, and the preparation process was referred to that described in Comparative Example 4), its DPPH and ABTS values increased by 25% and 30% respectively. It can be seen that the effect of the treatment of heating linoleic acid in combination with cold plasma in the examples on antioxidant activity is also related to the type of protein. The modification of soy protein by heating linoleic acid in combination with cold plasma has a more obvious improvement on the final antioxidant activity.

[0101] Example 8

[0102] Comparison of solubility and antioxidant activity under the same degree of oxidation Prepare soy-based nutritional powders with only heat-induced linoleic acid treatment or only cold plasma treatment with the same degree of oxidation.

[0103] The preparation of the soy-based nutritional powder treated only with heat-induced linoleic acid is basically the same as that of Comparative Example 2, except that the addition amount of linoleic acid is 12%, and the treatment time of linoleic acid is extended to 40 min. The carbonyl and free sulfhydryl groups were measured with reference to Example 4 and Example 5 respectively, and the results were 7.4 nmol / mg and 5.9 μmol / mg respectively, which were comparable to the carbonyl and free sulfhydryl group measurement results of Example 1, which were 7.5 nmol / mg and 6 μmol / mg.

[0104] The preparation of the soy-based nutritional powder treated only with cold plasma is basically the same as that of Comparative Example 3, except that the voltage is increased to 25 KV, and at the same time the plasma treatment time is extended to 200 min. The carbonyl and free sulfhydryl groups were measured with reference to Example 4 and Example 5 respectively, and the results were 7.3 nmol / mg and 5.8 μmol / mg respectively, which were comparable to the carbonyl and free sulfhydryl group measurement results of Example 1, which were 7.5 nmol / mg and 6 μmol / mg.

[0105] The solubility was measured with reference to Example 6. The measurement results of the soy-based nutritional powder treated only with heat-induced linoleic acid and the soy-based nutritional powder treated only with cold plasma were 50% and 48% respectively, which were inferior to those of Example 1. It can be seen that the dissolution performance of the soy-based nutritional powder treated only with heat-induced linoleic acid or only with cold plasma with the same degree of oxidation is inferior to that of Example 1.

[0106] The antioxidant properties were measured with reference to Example 7. The DPPH measurement results of the soy-based nutritional powder treated only with heat-induced linoleic acid and the soy-based nutritional powder treated only with cold plasma were 53% and 55% respectively. The ABTS measurement results of the soy-based nutritional powder treated only with heat-induced linoleic acid and the soy-based nutritional powder treated only with cold plasma were 52% and 48% respectively. It can be seen that the antioxidant properties of the soy-based nutritional powder treated only with heat-induced linoleic acid or only with cold plasma with the same degree of oxidation are inferior to those of Example 1.

[0107] Finally, it should be noted that the above embodiments do not limit the present invention in any form. Those skilled in the art can make some modifications and improvements based on the present invention.

Claims

1. A preparation method of a linoleic acid-rich soy-based nutritional powder with moderate protein oxidation, characterized in that, It includes the following steps: Add linoleic acid to soymilk, heat and combine with cold plasma treatment, and obtain moderately protein-oxidized linoleic acid-rich soy-based nutritional powder through homogenization, concentration, and drying. The addition amount of linoleic acid is 7 - 10%; the heating temperature is 40 - 50 °C, and the heating time is 15 - 20 min; when performing cold plasma treatment, the voltage is 10 - 18 KV, the treatment time is 90 - 150 min, and the power is 45 - 55 W.

2. The preparation method of a moderately protein-oxidized linoleic acid-rich soybean-based nutritional powder according to claim 1, characterized in that, It includes the following steps: 1) Prepare soybean powder, form soymilk, and add honey, xanthan gum, sodium polyacrylate, lecithin, and vanilla syrup. 2) Add linoleic acid and perform heating combined with cold plasma treatment to obtain treated soymilk. 3) Obtain moderately protein-oxidized linoleic acid-rich soy-based nutritional powder through homogenization, concentration, and drying.

3. The preparation method of a moderately protein-oxidized linoleic acid-rich soy-based nutritional powder according to claim 2, characterized in that, The steps for preparing soybean powder are as follows: Mix soybeans and water at a mass ratio of 1:9 - 11, soak for 10 - 14 h, and wash; use a blender at 20000 - 40000 r / min to grind soybeans into powder to obtain soybean powder.

4. The preparation method of a linoleic acid-rich soy-based nutritional powder with moderate protein oxidation according to claim 2, characterized in that, The process of forming soymilk is as follows: Mix soybean powder and water at a mass ratio of 1:9 - 11, cook at 90 - 110 °C, stir continuously to form soymilk; filter and separate soymilk from residues; adjust the pH of soymilk to 6.0 - 6.

5.

5. The preparation method of a moderately protein-oxidized linoleic acid-rich soy-based nutritional powder according to claim 2, characterized in that, Add 4 - 6 wt% of honey, 0.05 - 0.15 wt% of xanthan gum, 0.05 - 0.2 wt% of sodium polyacrylate, 0.03 - 0.07 wt% of lecithin, and 0.5 - 1.5 wt% of vanilla syrup to soymilk.

6. The preparation method of a moderately protein-oxidized linoleic acid-rich soybean-based nutritional powder according to claim 1, characterized in that, Use two-stage homogenization. The first-stage high-pressure homogenization sets the homogenization pressure at 20 - 30 MPa and the treatment time at 5 - 10 minutes; the second-stage low-pressure homogenization sets the homogenization pressure at 10 - 15 MPa and the treatment time at 3 - 5 minutes.

7. The preparation method of a moderately protein-oxidized linoleic acid-rich soybean-based nutritional powder according to claim 1, characterized in that, During concentration, the vacuum degree is 82.6 - 98.6 KPa, the temperature is 45 - 55 °C, and the steam pressure is less than 196 KPa.

8. The preparation method of a linoleic acid-rich soy-based nutritional powder with moderate protein oxidation according to claim 1, characterized in that, Use low-temperature spray drying. Set the inlet air temperature at 150 - 170 °C, control the outlet air temperature at 80 - 90 °C, adjust the feed concentration to 25 - 40%, where the feed concentration refers to the mass fraction of solid components in the treated soymilk, and the atomization speed is in the range of 250 - 300 r / s.

9. Moderately protein-oxidized linoleic acid-rich soy-based nutritional powder prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the preparation method according to any one of claims 1 - 8 in the preparation of linoleic acid-rich soy-based nutritional powder.

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