Lotus root powder and preparation method thereof

Abstract

The invention belongs to the field of food, and particularly relates to lotus root powder and a preparation method thereof. The content of soluble dietary fibers in the lotus root powder provided by the invention is 15.46 g / 100g, the content of total phenols is 56.41 mg / 100g, and the lotus root powder is suitable for preparing functional foods rich in soluble dietary fibers and polyphenols. According to the preparation method of the lotus root powder provided by the invention, the content of soluble dietary fibers and the content of total phenols in the dietary fibers are remarkably increased by utilizing an electroporation effect of a pulsed electric field and a physical crushing effect of high-speed dispersion and homogenization, and the method solves the problems of low content of soluble dietary fibers and tedious preparation steps in a traditional process.

Description

Technical Field

[0001] The invention belongs to the field of food, and particularly relates to lotus root powder and a preparation method thereof. Background Art

[0002] Lotus root is rich in dietary fiber, polyphenols, starch, minerals and other bioactive substances. Lotus root contains more phenolic substances and has strong antioxidant and free radical scavenging activity. The dietary fiber and total phenol content in lotus root nodes are significantly higher than that in lotus root tails, lotus root heads and lotus roots. The polyphenol oxidase activity in lotus root nodes is the highest and browning occurs easily. These bioactive substances make lotus root have antioxidant and anti-inflammatory effects. Dietary fiber is widely used in many foods due to its unique functional properties, especially viscosity formation and gelling ability. Soluble dietary fiber can dissolve in water, has good adsorption properties, can regulate intestinal flora, and lower blood lipids and blood sugar.

[0003] In the existing fruit and vegetable processing technology, some traditional sterilization methods often destroy the nutrients in the food, and the soluble dietary fiber content of the lotus root products produced is less than 10%, which greatly affects its food properties such as water retention and rheology, resulting in poor solubility and taste of lotus root food, limiting its wide application in the field of food processing.

[0004] At present, some studies have been conducted to increase the dietary fiber content of lotus root powder by pulping the lotus root, separating the liquid and the residue, treating the lotus root residue separately, and then recovering and adding it to the lotus root pulp. However, this method is cumbersome, requires separate separation of components, and has a low soluble dietary fiber content. Summary of the invention

[0005] Based on the above technical problems, the object of the present invention is to provide a lotus root powder and a preparation method thereof.

[0006] To achieve the above object, the technical solution adopted by the present invention is: The present invention provides a method for preparing lotus root powder, comprising the following steps: S1. Slice fresh lotus root, dry with hot air, and grind to obtain dry powder; S2, preparing lotus root slurry by mixing dry powder and water in a mass volume ratio of 1 g: 40 mL, treating the lotus root slurry with a pulse electric field to obtain a reaction liquid, and performing high-speed dispersion and homogenization processing on the reaction liquid to obtain a treated liquid; S3, freeze-drying and grinding the treated liquid to obtain lotus root powder.

[0007] The lotus root powder preparation method provided by the present invention utilizes the instantaneous electric field energy of a pulsed electric field to exert an electroporation effect on lotus root cells, open cell channels, and enable the substances in the cells to be better released, and then utilizes high-speed dispersion and homogenization to further break up the cells, efficiently disperse molecular substances, and promote the combination of bioactive substances therein. Under the effect of this treatment method, on the one hand, the soluble dietary fiber content in the lotus root is increased, and on the other hand, the covalent interaction between the dietary fiber and polyphenols therein is promoted, and the adsorption of the dietary fiber and the soluble dietary fiber on the lotus root polyphenols is promoted, so that the finally obtained lotus root powder has a higher total phenol retention.

[0008] Furthermore, the hot air drying condition is 60° C., 15 h.

[0009] Furthermore, the treatment intensity of the pulse electric field is 4 kV / cm.

[0010] Furthermore, the flow rate of the lotus root slurry passing through the pulsed electric field is 100 mL / min.

[0011] Furthermore, the half-peak width of the pulse electric field treatment is 45 μs, and the treatment is repeated 9 times in a cycle.

[0012] Furthermore, the high-speed dispersion and homogenization processing conditions are a rotation speed of 9000 rpm / min for 30 min.

[0013] Furthermore, the freeze-drying conditions are -80°C, 24h.

[0014] The invention also provides lotus root powder prepared by the method.

[0015] The present invention also provides application of the lotus root powder in preparing a food rich in soluble dietary fiber, wherein the content of soluble dietary fiber in the food rich in soluble dietary fiber is 15.46 g / 100 g.

[0016] The present invention also provides application of the lotus root powder in preparing a polyphenol-rich food, wherein the polyphenol content of the polyphenol-rich food is 56.41 mg / 100 g.

[0017] The present invention has the following beneficial effects: The present invention effectively improves the soluble dietary fiber content in lotus root powder and the binding effect of dietary fiber on polyphenols through pulse electric field treatment and coupled high-speed dispersion homogenization processing, so that the soluble dietary fiber content in lotus root powder accounts for about 24% of the total dietary fiber content, and the total phenol content in the dietary fiber is 56.41 mg / 100 g, which is 49.3% higher than that of untreated lotus root powder, wherein the total phenol content in the soluble dietary fiber reaches 63.26 mg / 100 g, which is 236.3% higher than that of untreated lotus root powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a sample picture of lotus root powder.

[0019] Figure 2 This is a comparison chart of dietary fiber content in lotus root powder under different processing methods.

[0020] Figure 3 This is a graph showing the results of soluble dietary fiber and insoluble dietary fiber content in lotus root powder under different high-speed dispersion and homogenization treatment conditions.

[0021] Figure 4 This is the result graph of total phenol content in lotus root powder dietary fiber, soluble dietary fiber and insoluble dietary fiber under different high-speed dispersion homogenization treatment conditions. DETAILED DESCRIPTION

[0022] The present invention is described in detail with respect to specific examples below, but it should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0023] Embodiment 1: lotus root powder preparation method.

[0024] 1. Preparation steps of lotus root powder.

[0025] 1. Take fresh lotus root, wash and peel it, slice it, dry it with hot air at 60℃ for 15h, and sieve it through 100 mesh to obtain dry powder.

[0026] 2. Prepare lotus root slurry with dry powder and water in a ratio of 1g:40ml. Pass the mixture through a pulse electric field of 4kV / cm, a flow rate of 100mL / min, and a half-peak width of 45μs. Repeat the treatment for 9 times to obtain a reaction solution. Disperse and homogenize the reaction solution at a high speed of 9000rpm / min for 30min to obtain a treated solution.

[0027] 3. Freeze-dry the treated solution at -80°C for 24 hours and then sieve through a 100-mesh sieve to obtain lotus root powder. The lotus root powder sample is as follows: Figure 1 shown.

[0028] Verification example 1: The influence of different pulse electric field coupling treatment methods on the preparation of lotus root powder.

[0029] 1. Experimental setup.

[0030] In order to demonstrate the effect of different pulse electric field coupling treatments on the preparation of lotus root powder, the following settings were made: (1) Enzymatic hydrolysis: Cellulase with an activity of 10000 U / g was added to the reaction solution in a mass volume ratio of 1 g:99 mL and reacted at 50° C. for 2 h to obtain a treated solution.

[0031] (2) High-pressure homogenization: The reaction solution was subjected to high-pressure homogenization at 100 Bar and a flow rate of 100 mL / min, and the treatment was repeated three times to obtain a treated solution.

[0032] (3) Magnetic induction electric field: The reaction solution is placed in a magnetic induction electric field of 100 V and 50 kHz for 30 min to obtain a treated solution.

[0033] (4) High-speed dispersion and homogenization: The reaction liquid is treated at a speed of 100,000 rpm / min for 30 min to obtain a treated liquid.

[0034] The untreated group was not subjected to the other treatment methods of pulse electric field coupling, and the remaining steps were the same as those in Example 1.

[0035] 2. Detection method.

[0036] Detection of soluble and insoluble dietary fiber content in lotus root dietary fiber: Mix lotus root powder and 0.05 mol / L MES-TRIS buffer in a beaker at a mass volume ratio of 1g:40ml, add 40μL of α-amylase with a concentration of 120000U / mL, react at 95℃ for 1h, cool to 60℃, add 1mL of alkaline protease with a concentration of 400U / mL and stir for 2h, then adjust the solution pH to 4.5, add 0.4ml of glucoamylase with a concentration of 3300U / mL, stir and react for 30min to obtain enzymolysis solution. Then filter the enzymolysis solution, separate the filtrate for use, wash the filter residue and dry it at 105℃ for 8h to measure the insoluble dietary fiber content. Add 4 times the volume mass fraction of 95% ethanol to the filtrate, precipitate overnight at room temperature, and dry the residue after filtration to measure the soluble dietary fiber content.

[0037] 3. Experimental results.

[0038] The results are as follows Figure 2 As shown, compared with the untreated group, the four treatment methods of pulse-coupled enzymatic hydrolysis, pulse-coupled high-pressure homogenization, pulse-coupled magnetic induction electric field, and pulse-coupled high-speed dispersion homogenization all increased the soluble dietary fiber content in lotus root powder and decreased the insoluble dietary fiber content, that is, increased the proportion of soluble dietary fiber in dietary fiber. Among them, the effect of pulse electric field coupled high-speed dispersion homogenization treatment was the most significant, with the soluble dietary fiber content reaching 15.46g / 100g, an increase of 99.2% compared with the untreated group. This may be because the electroporation effect of the pulsed electric field greatly increases the permeability of the cell membrane, opens the transmission channel of substances inside and outside the cell membrane, and then uses high-speed dispersion homogenization to further break up the cells, efficiently disperse molecular substances, and promote the binding of bioactive substances therein. Therefore, the pulse electric field coupled high-speed dispersion homogenization treatment step was selected for the next step of verification.

[0039] Verification example 2: Optimization of high-speed dispersion and homogenization processing conditions of lotus root powder.

[0040] 1. Experimental setup.

[0041] In order to demonstrate the effect of different high-speed dispersing and homogenizing treatment conditions on the preparation of lotus root powder, the following settings were made: Table 1 High-speed dispersion and homogenization processing conditions The remaining steps are the same as in Example 1.

[0042] 2. Content detection.

[0043] 1. Dietary fiber content detection: Mix lotus root powder and 0.05 mol / L MES-TRIS buffer in a beaker at a mass volume ratio of 1 g:40 mL, add 40 μL of 120000 U / mL α-amylase, react at 95 ° C for 1 hour, cool to 60 ° C, add 1 mL of 400 U / mL alkaline protease and stir for 2 hours, then adjust the solution pH to 4.5, add 0.4 ml of 3300 U / mL glucoamylase, stir for 30 minutes to obtain an enzymolyte, mix the enzymolyte and 95% ethanol at a volume ratio of 1:4, and precipitate overnight. The precipitate is freeze-dried and crushed to obtain lotus root modified dietary fiber powder, and the weight is the dietary fiber content.

[0044] 2. The steps for detecting the soluble and insoluble dietary fiber content in lotus root dietary fiber are the same as those in Verification Example 1.

[0045] 3. Detection of polyphenol content: Take 50mg lotus root modified dietary fiber powder and mix it with 10ml 40% ethanol by mass, extract it in a 100W ultrasonic field for 40min, centrifuge it at 10000rpm / min for 15min, separate 200μL of supernatant, add 800μL water and 125μL of Folin phenol reagent, mix it and react it at 25℃ in the dark for 6min, then add 1.25mL of 7% Na2CO3 solution, add water to 3mL, mix it and react it at 25℃ in the dark for 90min. The blank control group follows the above steps except that no sample is added. Finally, the absorbance Y of the sample and the absorbance Y0 of the blank control group are measured at 760nm.

[0046] Preparation of gallic acid standard series concentrations: Prepare gallic acid standard solutions of 0μg / mL, 2.5μg / mL, 5.0μg / mL, 10.0μg / mL, 20.0μg / mL, 30.0μg / mL, 40.0μg / mL, 60.0μg / mL, 80.0μg / mL, and 100.0μg / mL. Take 200μL of gallic acid standard solution and add 800μL of water and 125μL of Folin phenol reagent respectively, mix well and react in the dark, add 1.25mL of 7% Na2CO3 solution, add water to 3mL, mix well and react in the dark, and measure the absorbance at 760nm. The blank control group was operated according to the above steps except that no sample was added. With concentration as the horizontal axis (μg / mL) and absorbance value A as the vertical axis, draw the standard curve: y=0.007x+0.0198, R²=0.999.

[0047] Substitute the sample absorbance into the standard curve to determine the total phenol concentration C in the sample and the blank control group C0, and calculate the polyphenol content X according to the following formula.

[0048] X=[(C-C0)×V×f] / (m×1000).

[0049] Where: X is the content of total polyphenols in the sample, in mg / g; C is the concentration of total polyphenols in the sample, in μg / mL; C0 is the concentration of total polyphenols in the blank, in μg / mL; V is the volume of the added extract, in mL; f is the dilution factor; m is the mass of the weighed sample, in g.

[0050] 3. Experimental results.

[0051] like Figure 3 As shown in the figure, the soluble dietary fiber content of T1 was slightly higher than that of the untreated group, increasing by 12.5%, while the insoluble dietary fiber decreased. As the high-speed dispersion homogenization treatment time increased, the soluble dietary fiber content further increased, reaching a peak at T3, and then decreased. As the soluble dietary fiber increased, the insoluble dietary fiber content decreased, which may be due to the decomposition and conversion of some insoluble dietary fiber into soluble dietary fiber. From the results of dietary fiber content, it can be seen that the dietary fiber extraction amount under treatment from T1 to T5 increased. Compared with the untreated group, the soluble dietary fiber content in the lotus root powder treated from T1 to T5 increased significantly, and the insoluble dietary fiber content decreased, indicating that the lotus root powder obtained by pulse electric field coupling high-speed dispersion homogenization can effectively increase the soluble dietary fiber content in the total dietary fiber. The soluble dietary fiber content in condition 3 was 15.46g / 100g, an increase of 37% compared with the untreated lotus root powder.

[0052] like Figure 4As shown in the figure, from the results of total phenol content, it can be seen that with the extension of high-speed dispersion homogenization time, the total phenol content in soluble dietary fiber gradually increases. The total phenol content of dietary fiber and soluble dietary fiber after T1-T5 treatment is significantly higher than that of the untreated group, among which the total phenol content of dietary fiber in T3 reaches 56.41 mg / 100g. The total phenol content of soluble dietary fiber in T5 is as high as 63.26 mg / 100g. This also shows that the lotus root powder prepared by pulse electric field coupling high-speed dispersion homogenization can not only increase the content of soluble dietary fiber in total dietary fiber, but also effectively improve the total phenol adsorption of dietary fiber and soluble dietary fiber. This is mainly because there is a covalent phase interaction between dietary fiber, soluble dietary fiber and polyphenols, and physical field processing promotes this effect, so that dietary fiber adsorbs more total phenols, thereby effectively improving the retention of total phenols.

[0053] Therefore, T3 was determined to be the optimal treatment condition. The highest content of soluble dietary fiber in dietary fiber during T3 treatment was 15.46g / 100g, which was 37% higher than that of untreated lotus root powder. At this time, the total phenol content of dietary fiber also reached the optimal value of 56.41mg / 100g, and the total phenol content of soluble dietary fiber reached 44.04mg / 100g. Soluble dietary fiber has better physiological activity and function than insoluble dietary fiber, and total phenol has good antioxidant and anti-inflammatory effects. Therefore, the lotus root powder obtained by T3 treatment has greatly improved the content of soluble dietary fiber and total phenol in its dietary fiber, and the obtained dietary fiber also has better physiological activity.

[0054] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

Claims

1. A method for preparing lotus root powder, characterized in that: The following steps are involved: S1. Slice fresh lotus root, dry with hot air, and grind to obtain dry powder; S2, preparing lotus root slurry by mixing dry powder and water in a mass volume ratio of 1 g: 40 mL, treating the lotus root slurry with a pulse electric field to obtain a reaction liquid, and performing high-speed dispersion and homogenization processing on the reaction liquid to obtain a treated liquid; S3, freeze-drying and grinding the treated liquid to obtain lotus root powder.

2. The method for preparing lotus root powder according to claim 1, characterized in that: The hot air drying condition is 60° C., 15 h.

3. The method for preparing lotus root powder according to claim 1, characterized in that: The treatment intensity of the pulse electric field is 4 kV / cm.

4. The method for preparing lotus root powder according to claim 1, characterized in that: The flow rate of the lotus root slurry passing through the pulsed electric field is 100 mL / min.

5. The method for preparing lotus root powder according to claim 1, characterized in that: The half-peak width of the pulse electric field treatment was 45 μs, and the treatment was repeated 9 times in a cycle.

6. The method for preparing lotus root powder according to claim 1, characterized in that: The high-speed dispersing and homogenizing processing conditions are a rotation speed of 9000 rpm / min for 30 min.

7. The method for preparing lotus root powder according to claim 1, characterized in that: The freeze-drying conditions are -80°C, 24h.

8. A lotus root powder, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

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