A method for modifying lotus root starch

Abstract

The application belongs to the technical field of food processing, and provides a modification method of lotus root starch: the lotus root powder is subjected to at least one of the following treatments: high-temperature and high-pressure treatment at 115 DEG C to 134 DEG C and 90 kPa to 115 kPa; or enzymolysis by using pullulanase. The lotus root starch is modified by physical and enzymatic treatment, the modified lotus root starch changes in amylose / amylopectin content, and further affects the properties of the starch such as water holding, oil holding, solubility, transparency and swelling degree. Thus, the lotus root starch is provided with the possibility for different application scenarios, and the use of the lotus root starch can be expanded.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology and relates to a method for modifying lotus root starch. Background Technology

[0002] Lotus root cultivation is highly seasonal, with a relatively concentrated market supply. Most lotus roots are sold fresh, but this fresh-raw sales model is susceptible to fluctuations in market supply and demand. Furthermore, lotus roots are prone to browning and spoilage during storage and sales, leading to significant losses. Therefore, developing deep processing of lotus roots is essential for ensuring the stable development of the lotus root industry.

[0003] Starch is the main component of lotus root, and processing lotus root into lotus root starch is the most effective way to develop it. Lotus root starch (LRS), also known as lotus root starch, is a starch product processed through steps such as washing, peeling, crushing, homogenizing, filtering, sedimentation, and drying. The physicochemical and functional properties of starch play a decisive role in the quality of lotus root products. Utilizing the differences in properties resulting from the modification of lotus root starch can produce foods with different characteristics, and selecting suitable starch raw materials according to the characteristics of the product can achieve effective control of lotus root starch quality, which is of great significance to the industrialization of lotus root starch in the food industry. Preparing lotus root starch into resistant starch can not only be widely used as a raw material for processing various functional foods according to its properties, but also improve its economic and social benefits through deep processing. The formation of resistant starch is determined by the starch's own structure, properties, and processing methods. Exploring a simple and effective method for modifying lotus root starch is of great significance to the development of lotus root deep processing and related industries. Summary of the Invention

[0004] To address the lack of deep processing technology for lotus root starch, this invention provides a method for modifying lotus root starch, resulting in modified lotus root starch with excellent food processing properties.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] A method for modifying lotus root starch includes the steps of: subjecting the lotus root starch to at least one of the following treatments (a) and (b): (a) High temperature and high pressure treatment at 115℃-134℃ and 90 kPa-115 kPa; (b) Enzymatic hydrolysis with pullulanase.

[0007] In the above modification method, lotus root starch suspension is used as raw material in order to obtain uniform modified starch.

[0008] In the above modification method, the amount of pullulanase added is 1000-20000 U / kg of starch dry weight. The enzymatic hydrolysis temperature is 40℃-65℃. The enzymatic hydrolysis time can be determined by at least one of the following physicochemical properties of the product: amylose content, amylopectin content, solubility, transparency, water holding capacity, oil holding capacity, swelling degree, gelatinization degree, and freeze-thaw stability.

[0009] A lotus root starch obtained by the above modification method.

[0010] The present invention has the following advantages: This invention modifies lotus root starch through physical and enzymatic treatments. The modified lotus root starch exhibits changes in its amylose / amylose content, thereby affecting its water-holding capacity, oil-holding capacity, solubility, transparency, and swelling capacity. This opens up possibilities for using lotus root starch in different application scenarios and expands its application pathways. Attached Figure Description

[0011] Figure 1 This is a graph showing the changes in the iodine-binding capacity of lotus root starch under different treatment methods; Figure 2 The water-holding and oil-holding properties of lotus root starch processed using different methods; Figure 3 The effects of different temperatures on the solubility (a) and swelling (b) of lotus root starch are shown. Detailed Implementation

[0012] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the present invention is not limited to the following embodiments.

[0013] Example 1: Preparation of modified lotus root starch Lotus root starch was prepared into a 6% starch solution. The solution was then heated in a water bath at 90℃ for 30 minutes. After cooling to room temperature, it was subjected to high temperature and high pressure treatment at 121℃ for 20 minutes. After cooling, the pH of the starch solution was adjusted to 5.5 with glacial acetic acid. Pullulanase (1000 U / g) at a starch mass ratio of 2% was added, and the solution was enzymatically hydrolyzed at 45℃ for 24 hours. The solution was then transferred to a 95℃ water bath for 5 minutes to inactivate the enzyme, and finally freeze-dried to obtain modified lotus root starch HELRS.

[0014] Example 2: Preparation of modified lotus root starch Lotus root starch was prepared into a 6% starch solution, gelatinized in a water bath at 90℃ for 30 min, cooled to room temperature, and then subjected to high temperature and high pressure treatment at 121℃ for 20 min, followed by freeze drying to obtain modified lotus root starch HLRS.

[0015] Example 3: Preparation of Modified Lotus Root Starch Lotus root starch was prepared into a 6% starch solution. After cooling, the solution was heated in a water bath at 90℃ for 30 min. The pH of the starch solution was adjusted to 5.5 with glacial acetic acid. Pullulanase (1000 U / g) at a starch mass ratio of 2% was added and the solution was enzymatically hydrolyzed at 45℃ for 24 h. The solution was then transferred to a 95℃ water bath for 5 min to inactivate the enzyme. Finally, the solution was freeze-dried to obtain modified lotus root starch ELRS.

[0016] Example 4: Physicochemical properties of modified lotus root starch The modified starches obtained in Examples 1-3 were subjected to physicochemical property determination, with unmodified lotus root starch (LRS) as a control.

[0017] 1. Iodine binding power determination The iodine-binding capacity of starch is determined by spectrophotometry, which is an important indicator of the strength of starch's iodine-binding ability. The absorbance value reflects the relative concentration level of amylose. Different treatment methods will affect the maximum absorption wavelength of the iodine-binding spectrum of starch. The specific method is as follows: Weigh 100 mg of sample and dissolve it in 10 mL of DMSO, then dilute with water to 50 mL. Take 5 mL of sample, add 1 mL of iodine reagent (0.2% I₂ + 2.0% KI), and make up to 50 mL with distilled water. Vortex mix and let stand for 15 min, then perform a full-band scan from 450 nm to 800 nm.

[0018] The results are as follows Figure 1 As shown, the maximum absorption wavelengths of the four starches are concentrated between 585 nm and 600 nm. The maximum absorption wavelength of LRS and HLRS is at 597 nm, with maximum absorbance values ​​of 0.662 and 0.672, respectively. The maximum absorption wavelength of ELRS and HELS is at 589 nm, with maximum absorbance values ​​of 0.989 and 0.968, respectively. After enzymatic hydrolysis and enzymatic hydrolysis followed by pressure heating, the iodine-binding spectra of lotus root starch were improved to varying degrees compared with the untreated starch. The iodine-binding spectra of lotus root starch treated by pressure heating were slightly improved. After enzymatic hydrolysis, the iodine-binding spectra of ELRS and HELS were much higher than those of HLRS and LRS, indicating that ELRS and HELS contain a higher content of soluble amylose.

[0019] 2. Water-holding and oil-holding properties of starch Water-holding capacity and oil-holding capacity represent the ability of starch to absorb water and oil when dispersed in cold water and oil phases, respectively, and are important indicators for evaluating starch that swells in cold water. The specific determination method is as follows: 1.00 g of starch is thoroughly mixed with 10 mL of distilled water / soybean oil in a centrifuge tube and stored at room temperature for 24 h. Centrifuge at 10000 r / min for 5 min, discard the supernatant, weigh the precipitate, and calculate the water-holding capacity / oil-holding capacity of the starch using the following formula: Water-holding capacity / oil-holding capacity = (sediment mass / starch mass).

[0020] The results of starch water-holding and oil-holding properties are shown in [the table below]. Figure 2 After treatment, the water-holding and oil-holding properties of lotus root starch were significantly increased. The water-holding capacity of modified lotus root starch was significantly increased, and the water-holding effects of the three modification methods were not significantly different. Before modification, the oil-holding capacity of lotus root starch was better than its water-holding capacity; after modification, the water-holding capacity of all lotus root starches was better than their oil-holding capacity, and the oil-holding capacity of the modified lotus root starches showed significant differences.

[0021] 3. Hydration characteristics of starch Prepare a 2% (w / w) starch suspension from the sample, heat in a 90℃ water bath for 30 min, cool to room temperature, and centrifuge at 10000 r / min for 5 min. Pour off the supernatant and freeze-dry it to determine the mass of the soluble starch; simultaneously, weigh the starch in the lower layer after centrifugation. Calculate the starch solubility, swelling capacity, and water absorption capacity using the following formulas: Solubility S (%) = (Dry weight of starch in supernatant / Dry weight of sample) × 100% Starch swelling degree B (%) = Wet weight of lower sediment starch / [Dry weight of sample × (1-S)] × 100% The water absorption capacity of starch, C = (wet weight of starch in the lower sediment / dry weight of the sample) × 100%.

[0022] Table 1. Hydration characteristics of different lotus root starches Note: Data are expressed as mean ± standard deviation; different letters in the same column indicate significant differences (P < 0.05).

[0023] Compared with untreated lotus root starch, the water absorption capacity and hydration characteristics of treated lotus root starch showed significant differences. As shown in Table 1, HLRS had the highest water absorption capacity (2.847±0.028) and swelling degree (21.766±0.747%), which is consistent with the results of starch water holding capacity testing; HELRS had a significantly higher solubility (63.555±2.197%) than other groups.

[0024] The solubility and swelling of starch at different temperatures were determined using a similar method: 50 mL of starch suspension with a mass fraction of 2.0% was heated and stirred in a water bath at 30, 40, 50, 60, 70, 80, and 90°C for 30 min, respectively, centrifuged at 3000 rmin for 20 min, the supernatant was evaporated to dryness in a water bath at 90°C, and the precipitate was dried in a drying oven at 105°C and weighed to obtain the mass of dissolved starch and the mass of precipitate. The solubility and swelling of starch were then calculated.

[0025] from Figure 3 As can be seen, the solubility of starch generally increases with increasing temperature. The solubility of lotus root starch increases slowly before 60℃, with the solubility ranking as HELRS > ELRS > HLRS > LRS. After 60℃, the solubility increases rapidly. When the heating temperature exceeds 70℃, the solubility of lotus root starch increases rapidly, and the solubility of HELRS is significantly higher than the other three starches. Figure 3 As shown in b, the swelling degree of starch increases slowly with increasing temperature. Before 60℃, HLRS has the highest swelling degree and LRS has the lowest swelling degree. After 60℃, the order of increase in swelling degree is: HLRS > LRS > ELRS > HELRS. Among them, HLRS has the highest swelling degree, while the swelling degree of HELRS shows the slowest increasing trend, which is related to its higher solubility.

[0026] 4. Transparency, degree of gelatinization, and freeze-thaw stability of starch paste (1) Transparency of starch paste: Weigh a certain amount of starch sample, add an appropriate amount of purified water to prepare a starch suspension with a mass fraction of 1%, gelatinize in a boiling water bath for 30 min, and then cool to room temperature. Use a UV-Vis spectrophotometer at a wavelength of 620 nm, with purified water as a blank control, to determine the transparency of the starch paste.

[0027] (2) Degree of gelatinization of starch paste: Dissolve 0.2 g of sample powder in 98 mL of distilled water, add 2 mL of 10 mol / L potassium hydroxide solution, stir for 5 min, centrifuge at 5000 r / min for 5 min, take 1 mL of supernatant, add 0.4 mL of 0.5 mol / L hydrochloric acid, add distilled water to 10 mL, and finally add 0.1 mL of iodine solution (1 g of iodine and 4 g of potassium iodide dissolved in 100 mL of distilled water), mix well, and measure absorbance A1 at 600 nm. Replace the volumes of distilled water and potassium hydroxide solution with 95 mL and 5 mL, respectively, and replace the volume of hydrochloric acid with 1 mL, and keep the other steps the same, and measure absorbance A2. The ratio of A1 to A2 multiplied by 100% is the degree of gelatinization of starch.

[0028] (3) Water separation rate of starch paste: Weigh a certain amount of starch sample, prepare a starch milk with a mass fraction of 6%, place it in a 100 mL centrifuge tube, heat it in a boiling water bath to gelatinize it, and after the solution cools to room temperature, cover the centrifuge tube and freeze it in a -18℃ refrigerator for 24 h, and then thaw it naturally at room temperature for 3 h. Centrifuge it at 3500 r / min for 20 min, discard the supernatant, weigh the mass of the precipitate in the centrifuge tube, and calculate the water separation rate as follows: Water separation rate D (%) = (mass of starch paste - mass of sediment) / mass of starch paste × 100%.

[0029] Table 2. Analysis of transparency and water separation rate of lotus root starch under different treatment methods Note: Data are expressed as mean ± standard deviation; different letters in the same column indicate significant differences (P < 0.05).

[0030] Higher starch transparency indicates less stagnation, a significant factor in food processing. Table 2 shows the transparency of lotus root starch paste. High-temperature, high-pressure (HLRS, 4.667±0.044%) treatment reduced the transparency, while enzymatic hydrolysis (ELRS, 11.867±0.111%) increased it. Lotus root starch treated with HLRS followed by enzymatic hydrolysis had the lowest transparency (HELRS, 0.717±0.011%). All treatments improved the gelatinization degree of lotus root starch, with HLRS (71.7%) showing the highest gelatinization. The lowest water separation rate was observed in LRS (16.827±2.269%), followed by HELRS (71.473±0.679%), and then ELRS (55.176±0.732%). HLRS (14.3±2.13%) had the lowest water separation rate, indicating that its freeze-thaw properties were better than those of LRS before treatment (16.827±2.269%). The water separation rates of ELRS (24.496±1.864%) and HELRS (22.016±1.282%) increased after enzymatic hydrolysis treatment, proving that their freeze-thaw properties were not as good as those of LRS.

[0031] 5. Starch gel properties Starch was prepared into a 6% (w / w) starch slurry, heated in a 90℃ water bath for 30 min, cooled, and then molded. The starch was then refrigerated at 4℃ for 24 h, removed, and cut into starch gel blocks of equal length, width, and volume. Texture analysis was performed using a texture analyzer. Test conditions: Two-stage compression (TPA) mode was selected, probe P / 0.5, compression distance was 3 mm, and the pre-test, during-test, and post-test speeds were all 1 mm / s. Each sample was tested three times, and the average value was taken.

[0032] The textural properties of starch gels obtained by different treatment methods vary. Hardness represents the strength of the starch gel under pressure. Compared with LRS, the hardness of starch gels from HLRS and ELRS shows a decreasing trend, indicating a weakening of the strength of resistant starch gels. The hardness of HELRS increases, indicating an increase in the gel strength of starch. Elasticity represents the viscoelastic properties of starch gels. The data in the table show that the elasticity of modified starches decreased to varying degrees, with HELRS exhibiting the lowest elasticity. Cohesion represents the strength of the binding force between molecules within the starch gel. The cohesion of modified starches decreased, which may be due to the rearrangement and recombination of amylose to form a denser gel network structure. Viscosity depends on the interaction between cohesive and adhesive forces.

[0033] Table 3 Properties of starch gel Note: Data are expressed as mean ± standard deviation; different letters in the same column indicate significant differences (P < 0.05).

[0034] Table 3 shows that compared to LRS, the viscosity of starch in HLRS and ELRS decreased, while the viscosity of HELRS increased. After modification, the resilience of HELRS increased, while that of HLRS and ELRS decreased. The increased amylose content in modified HELRS resulted in greater gel hardness and elasticity. The reduced viscosity and cohesiveness of HLRS and ELRS gels made the starch products more palatable and less sticky.

Claims

1. The application of a modified lotus root starch in improving food processing performance, characterized in that, The food processing properties are water retention, solubility, and transparency. The modification method consists of the following steps: lotus root starch suspension is subjected to a water bath at 90°C for 30 minutes, cooled to room temperature, and then subjected to high temperature and high pressure treatment at 121°C for 20 minutes. After cooling, the pH of the starch solution is adjusted to 5.5 with glacial acetic acid, pullulanase at a starch mass ratio of 2% (1000 U / g) is added, and the enzyme is hydrolyzed at 45°C for 24 hours. The enzyme is then inactivated in a water bath at 95°C for 5 minutes, and finally freeze-dried.

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