Two types of IV-type canna edulis resistant starch as well as preparation method, optimization method and application thereof

Abstract

The invention discloses two types of IV-type canna resistant starch as well as a preparation method, an optimization method and application thereof. The two types of IV-type canna resistant starch are esterified starch prepared from OSA and crosslinked starch prepared from STPP and STMP. Two types of IV-type resistant starch, namely esterified starch and cross-linked starch, are successfully prepared by utilizing an optimized parameter combination, the yield of the resistant starch is high, the substitution degree of the prepared esterified starch reaches 0.0174, the content of the resistant starch in the measured cross-linked starch is 73.1%, and the method can be used for preparing the IV-type canna resistant starch; the provided preparation and optimization method is simple and easy to operate, mild in condition, safe and effective, low in requirements on instruments and equipment and suitable for industrial production; no toxic and harmful raw materials and products are generated, and the prepared resistant starch has no potential safety hazard and can be applied to health-care foods and medicines.

Description

Technical Field

[0001] The invention relates to the technical field of resistant starch, in particular to two types of IV banana and taro resistant starches and preparation, optimization methods and applications thereof. Background Art

[0002] Resistant starch (RS) is a recognized dietary fiber that cannot be degraded and absorbed by the human small intestine, but can be fermented and utilized by physiological bacteria in the colon. RS can be divided into five categories according to their source, structure, digestive characteristics and application: RS1, RS2, RS3, RS4 and RS5. RS4 refers to chemically modified starch, including modifications such as esterification, etherification or cross-linking.

[0003] Studies have shown that RS has physiological functions such as stimulating the growth of beneficial bacteria, regulating blood sugar, lowering blood lipids and colon cancer incidence, and controlling body weight. Intake of RS4 can improve dyslipidemia and body composition. Eating dietary starch esterified with OSA can reduce the area under the blood glucose and insulin curves. The octenyl group of OSA-esterified high-amylose corn starch interacts hydrophobically with other hydrophobic substances in the digestive tract, which helps to remove these substances, including toxins, and enhances intestinal health. High-amylose starch with a high degree of cross-linking promotes the abundance of uniform Bacteroides and bromorumencoccus, and effectively controls the fermentation rate. After consuming cross-linked starch phosphate, the glucose uptake rate is low.

[0004] Canna edulis is a herbaceous plant of the genus Canna in the family Cannaceae. According to the Chinese Materia Medica, Canna edulis is sweet in taste and cool in nature, and has the effects of clearing away heat and dampness, and detoxifying. It is not strict with soil requirements, has strong adaptability, is drought-resistant, and has high yield. According to records, even if the farmland is managed extensively, the per mu yield can reach more than 5,000 catties. It is one of the crops used for extracting starch that are planted more in rural areas of Guangdong, my country. Therefore, a method for preparing type IV resistant starch using Canna edulis starch is provided, which is of great significance for promoting the development and utilization of Canna edulis starch, expanding the market for agricultural products, and increasing farmers' income. However, there is no report on producing modified starch using Canna edulis starch. Summary of the invention

[0005] The purpose of the present invention is to provide two types of IV-type banana and taro resistant starches and preparation, optimization methods and applications thereof, so as to fill the gap of the current lack of IV-type resistant starch using banana and taro starch as raw materials, provide a type IV banana and taro resistant starch that is simple to operate, safe and non-toxic, and promote the development and utilization of banana and taro starch.

[0006] To achieve the above objectives, the present invention provides two types of IV banana and taro resistant starches and preparation, optimization methods and applications thereof. The two types of IV banana and taro resistant starches are esterified starch prepared from OSA and cross-linked starch prepared from STPP and STMP.

[0007] The preparation methods of the two types of IV banana and taro resistant starches as described above include the following steps:

[0008] S1. Preparation of esterified starch

[0009] Disperse banana and taro starch in water, incubate in a water bath, adjust the pH to 8.5, then slowly add OSA, stirring while adding, stabilize the pH at 8.5-9.0 for 3-6 hours, then adjust the pH to 6.5, centrifuge to obtain the precipitate, wash the precipitate with a large amount of distilled water, and dry it at 40°C for 24 hours;

[0010] S2. Preparation of cross-linked starch

[0011] Add banana and cantaloupe starch dispersion water to an aqueous solution containing STMP, STPP and sodium sulfate, stir the mixture at a certain temperature for a certain period of time, adjust the pH to 8.0-12, and adjust the pH to 6.5 after a certain period of reaction. Centrifuge to obtain the precipitate, wash with a large amount of deionized water, and dry at 40°C overnight.

[0012] Preferably, in the banana and taro starch dispersion in step S1, the banana and taro starch accounts for 35% of the dispersion mass, the water bath incubation temperature is 30-45° C.; the slow addition of OSA means that the addition is completed within 1 hour, and the added mass of OSA is 3% of the dry banana and taro starch; the centrifugation conditions are 4000r, 10min.

[0013] Preferably, in the banana-taro starch dispersion in step S2, the banana-taro starch accounts for 35% of the mass of the dispersion; the concentrations of STMP, STPP and sodium sulfate in the aqueous solution containing STMP, STPP and sodium sulfate are 50 g / L, 0.5 g / L and 40 g / L respectively; the stirring temperature is 30-50°C and the stirring time is 30 min; the reaction is carried out at pH 11 for 3-5 h; and the centrifugation conditions are 4000 r for 10 min.

[0014] Preferably, the washing with a large amount of distilled water / deionized water means adding 1 volume of distilled water / deionized water to the precipitate, resuspending the precipitate and centrifuging at 4000r for 10min, and repeating the above washing process 2-3 times.

[0015] The optimization method for preparing the two types of IV banana taro resistant starch as described above comprises the following steps:

[0016] 1) Conduct preliminary experiments with reference to the preparation methods of resistant starch from other sources;

[0017] 2) performing substitution degree determination or resistant starch content determination;

[0018] 3) Conduct a single factor study

[0019] For the preparation of esterified starch, four factors including different OSA addition amount, reaction temperature, reaction time and pH were selected for single factor investigation;

[0020] For the preparation of cross-linked starch, three factors, pH, reaction temperature and reaction time, were selected for single factor investigation;

[0021] 4) Perform response surface optimization

[0022] Based on the results of single factor experiments, three factors, namely reaction temperature, reaction time and pH, and the interval around the merit values ​​of the three factors obtained in the single factor experiments were selected for optimization. The preparation process parameters were optimized by response surface design using the substitution degree determination results / resistant starch content as indicators.

[0023] 5) Data analysis to obtain the optimal parameter combination;

[0024] 6) Evaluate the optimal parameter combination by determining the degree of substitution or the resistant starch content.

[0025] Preferably, in the single factor investigation of the preparation of esterified starch in the step 3), different OSA addition amounts are 2%, 3%, 4%, 5%, and 6%, different reaction temperatures are 25°C, 30°C, 35°C, 40°C, and 45°C, different reaction times are 2h, 3h, 4h, 5h, and 6h, and different pH values ​​are 7.5, 8.0, 8.5, 9.0, and 9.5; in the single factor investigation of the preparation of cross-linked starch, different pH values ​​are 7, 8, 9, 10, and 11, different reaction temperatures are 35°C, 40°C, 45°C, 50°C, and 55°C, and different reaction times are 1h, 2h, 3h, 4h, and 5h.

[0026] The resistant starch prepared by the two methods for preparing type IV banana and taro resistant starch as described above is used in health foods and medicines.

[0027] Therefore, the two types of IV banana and taro resistant starches provided by the present invention and their preparation, optimization methods and applications have the following technical effects:

[0028] 1. Two types of IV-type resistant starch, esterified starch and cross-linked starch, were successfully prepared by using the optimized parameter combination of the present invention. The yield of resistant starch was high, the degree of substitution of the prepared esterified starch reached 0.0174, and the content of resistant starch in the cross-linked starch was determined to be 73.1%, which can be used for the preparation of IV-type banana and taro resistant starch;

[0029] 2. The preparation and optimization methods provided by the present invention are simple and easy to operate, with mild conditions, safety and effectiveness, low requirements for instruments and equipment, and are suitable for industrial production; no toxic or harmful raw materials and products are generated, and the prepared resistant starch does not have any safety hazards and can be used in health foods and medicines.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0032] Figure 1 This is the result of single factor investigation on the preparation of OSA esterified starch;

[0033] Figure 2 It is the response surface diagram of the interaction between the esterification reaction factors on DS, where part A is the effect of reaction temperature and reaction time, part B is the effect of reaction temperature and reaction pH, and part C is the effect of reaction time and reaction pH;

[0034] Figure 3 This is the result of single factor investigation on the preparation of cross-linked starch;

[0035] Figure 4 It is the response surface diagram of the interaction between the cross-linking reaction factors on DS, where part A is the effect of reaction temperature and reaction time, part B is the effect of reaction temperature and pH, and part C is the effect of reaction time and pH;

[0036] Figure 5 These are SEM electron microscope photos of banana-taro starch, OSA-esterified starch and cross-linked starch, where Part A is the SEM electron microscope photo of banana-taro starch, Part B is the SEM electron microscope photo of OSA-esterified starch, and Part C is the SEM electron microscope photo of cross-linked starch. The scale bars in the figures are all 10 μm.

[0037] Figure 6 These are the infrared, DSC and XRD observation results of banana and taro starch, OSA esterified starch and cross-linked starch. Part A is the infrared spectra of OSA esterified starch, cross-linked starch and banana and taro starch, Part B is the DSC results of the three, and Part C is the XRD results of the three. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0039] In order to make the purpose, technical scheme and advantages of the present application clearer, more thorough and more complete, the technical scheme of the present invention is clearly and completely described below through the accompanying drawings and examples. The following detailed descriptions are all descriptions of the embodiments, and are intended to provide further detailed descriptions of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs.

[0040] The reagents, instruments and software used in the examples were obtained from commercial sources.

[0041] Embodiment 1

[0042] The degree of substitution of OSA esterified starch is determined as follows:

[0043] The OSA esterified starch pre-experiment was carried out with reference to the preparation methods of other IV-type resistant starches in the prior art. The obtained OSA esterified starch was dried in an oven to a constant weight, 1.0 g of constant weight OSA esterified starch and 50 mL of distilled water were weighed and added to a 250 mL iodine volume flask, stirred into a dispersion, and then a phenolphthalein indicator was added and stirred to mix. Then 25 mL of 0.5 M NaOH solution was added, the stopper of the bottle mouth was removed, the stopper and the bottle wall of the iodine volume flask were rinsed with distilled water, and the excess alkali solution in the sample was titrated for the second time with a 0.5 M hydrochloric acid standard solution. The titration endpoint was when the red color just disappeared, and the volume of hydrochloric acid consumed V1 was recorded.

[0044] The blank titration of unmodified original banana and taro starch was carried out using the above method.

[0045]

[0046]

[0047] M—the percentage of succinyl in the sample (%);

[0048] V0 and V1—volumes of hydrochloric acid consumed by native starch and esterified starch (mL);

[0049] DS—degree of substitution.

[0050] The calculation formula of substitution efficiency (RE) is as follows:

[0051]

[0052] The theoretical degree of substitution is the degree of substitution assuming that all of the octenyl succinic anhydride (OSA) reacts with the starch.

[0053] Embodiment 2

[0054] The single factor investigation of OSA esterified starch is as follows:

[0055] Taking the degree of substitution (DS) as the index, a single factor experiment was carried out by selecting four factors: different OSA addition amounts (2, 3, 4, 5 and 6%), reaction temperatures (25, 30, 35, 40 and 45°C), reaction times (2, 3, 4, 5 and 6h) and reaction pH (7.5, 8.0, 8.5, 9.0 and 9.5).

[0056] With the reaction temperature of 35℃, reaction time of 4h, and reaction pH of 8.5-9.0 as the preparation process parameters, the effect of OSA addition (1%~9%) on DS was investigated; with the OSA addition of 3%, reaction time of 4h, and pH8.5-9.0 as the preparation process parameters, the effect of reaction temperature (25℃~45℃) on DS was investigated; with the OSA addition of 3%, reaction temperature of 35℃, and pH 8.5-9.0 as the preparation process parameters, the effect of reaction time (2h~6h) on DS was investigated; with the OSA addition of 3%, reaction temperature of 35℃, and reaction time of 5h as the preparation process parameters of OSTS, the effect of reaction pH (7.5~9.5) on DS was investigated, and the results are shown in Figure 1 .

[0057] Embodiment 3

[0058] OSA esterified starch response surface optimization method is as follows:

[0059] Based on the single factor experimental results obtained in Example 2, the optimal ranges of reaction temperature 30-40°C, reaction time 4-6h and reaction pH 8-93 factors were selected for optimization. The substitution degree determination results were used as indicators to optimize the preparation process parameters using the response surface software Design Expert V8.0.6. The results are shown in Table 1.

[0060] Table 1 Analysis of variance and significance test of regression model for esterified starch

[0061]

[0062]

[0063] From Table 1, it can be seen that the total model equation is significant (P < 0.001), and the lack of fit term (P > 0.05) is not significant. According to the F value, the factor contribution rate is C > A > B. The model correlation coefficient R 2 =0.9562, good fit, determination coefficient Radj 2 =0.8999, which can predict 89.99% of the response values, indicating that the model can be used to predict the actual conditions of each indicator.

[0064] The 3D effect surface diagram of each factor on the degree of substitution of esterified starch was drawn by software. The results are as follows Figure 2 , Figure 2Part A is the effect of reaction temperature and reaction time, Part B is the effect of reaction temperature and reaction pH, and Part C is the effect of reaction time and reaction pH. The steeper the surface, the greater the influence of the factor on the response value, and the flatter the surface, the smaller the influence of the factor on the response value. Among them, the reaction temperature (A) and reaction pH (C) have a greater influence on the degree of substitution of esterified starch, and the 3D effect surface diagram formed is steeper, while the reaction time (B) has a smaller influence, and the 3D effect surface diagram formed is flatter. With the highest degree of substitution of esterified starch as the condition, the optimal preparation process parameters obtained by software fitting are reaction temperature 38℃, reaction time 5.2h, pH 8.6, and the DS theoretical value is 0.0186. According to the feasibility of the operation, the predicted optimal preparation conditions are adjusted, that is, the reaction temperature is 38℃, the reaction time is 5h, and the pH is 8.5. Three verification tests were carried out, and the DS was 0.0174.

[0065] Embodiment 4

[0066] The determination method of resistant starch content in cross-linked starch is as follows:

[0067] A preliminary experiment of cross-linked starch was carried out with reference to other preparation methods of type IV resistant starch in the prior art. The obtained cross-linked starch was dried in an oven to a constant weight, and then the resistant starch content therein was determined using a GOPOD kit.

[0068] Embodiment 5

[0069] The single factor investigation of cross-linked starch is as follows:

[0070] Taking the resistant starch content as the index, a single factor experiment was carried out by selecting three factors: reaction pH (7, 8, 9, 10 and 11), reaction temperature (35, 40, 45, 50 and 55°C), and reaction time (1, 2, 3, 4 and 5h).

[0071] The reaction temperature was 35℃, the reaction time was 3h, and the effect of pH on the content of resistant starch was investigated. The reaction time was 3h and pH was 11 as the preparation process parameters, and the effect of reaction temperature on the content of resistant starch was investigated. The reaction temperature was 35℃, and pH was 11 as the preparation process parameters, and the effect of reaction time on the content of resistant starch was investigated. The results are shown in Figure 3 .

[0072] Embodiment 6

[0073] The response surface optimization of cross-linked starch was carried out as follows:

[0074] Based on the single factor test results obtained in Example 5, the optimal ranges of three factors, namely, reaction temperature 40-50°C, reaction time 2-4h and pH 10.5-11.5, were selected for optimization. Taking the resistant starch content as an indicator, the preparation process parameters of banana and taro cross-linked starch were designed and optimized using the response surface software Design Expert V8.0.6. The results are shown in Table 2.

[0075] Table 2 Analysis of variance and significance test of cross-linked starch regression model

[0076]

[0077]

[0078] From Table 2, it can be seen that the total model equation is significant (P < 0.0001), and the lack of fit term (P > 0.05) is not significant. According to the F value, the factor contribution rate is B > C > A. The model correlation coefficient R 2 =0.9873Good fit, determination coefficient Radj 2 =0.9710, which can predict 97.1% of the response values, indicating that the model can be used to predict the actual conditions of each indicator.

[0079] The 3D effect surface diagram of each factor on cross-linked starch and resistant starch was drawn by software. The results are as follows Figure 4 , Figure 4 Part A is the effect of reaction temperature and reaction time, part B is the effect of reaction temperature and pH, and part C is the effect of reaction time and pH. The steeper the surface, the greater the influence of the factor on the response value, and the flatter the surface, the smaller the influence of the factor on the response value. Among them, the reaction temperature (A) and reaction time (B) have a greater influence on the degree of substitution of esterified starch, and the 3D effect surface diagram formed is steeper, while the reaction pH (C) has a smaller influence, and the 3D effect surface diagram formed is flatter. Taking the highest resistant starch content as the condition, the optimal preparation process parameters obtained by software fitting are reaction temperature 48.42℃, reaction time 3.24h, pH 11.5, and the theoretical value of resistant starch content is 76.52%. According to the feasibility of the operation, the predicted optimal preparation conditions are adjusted, that is, the reaction temperature is 48℃, the reaction time is 3h, and the reaction pH is 11.5. Three verification tests were carried out, and the resistant starch content was 73.1%.

[0080] Embodiment 7

[0081] The OSA esterified starch was prepared using the optimal parameters obtained in Example 3, and the method was as follows:

[0082] Weigh 35g of banana and taro starch and disperse it in 100mL of water. Incubate in a water bath at 38℃ for 0.5h. Adjust the pH to 8.5 and then add 1mL of OSA (molecular mass 210.27) within 1h. Stir while adding to stabilize the pH at 8.5 for 5h. Then adjust the pH to 6.5, centrifuge at 4000r for 10min to obtain a precipitate, add 50mL of distilled water, resuspend the precipitate and centrifuge at 4000r for 10min to obtain a precipitate. Repeat the above washing-centrifugation process twice. Dry the obtained precipitate at 40℃ for 24h to obtain OSA esterified starch.

[0083] Embodiment 8

[0084] The cross-linked starch was prepared using the optimal parameters of the cross-linked starch obtained in Example 6, and the method was as follows:

[0085] 5.0 g STMP, 0.05 g STPP and 4.0 g sodium sulfate were added to 100 mL distilled water in sequence, stirred until all components were completely dissolved, 100 mL banana and taro starch dispersion water (35 g banana and taro starch was dispersed in 100 mL distilled water) was added, the mixture was stirred at 48 ° C for 30 min, the pH of the mixture was adjusted to 11.5, the pH of the mixture was adjusted to 6.5 after 3 h of reaction, and the mixture was centrifuged at 4000 r for 10 min to obtain a precipitate, 50 mL of distilled water was added, the precipitate was resuspended and centrifuged at 4000 r for 10 min to obtain a precipitate, the above washing-centrifugation process was repeated twice, and the obtained precipitate was dried at 40 ° C overnight to obtain cross-linked starch.

[0086] Effect verification

[0087] (i) The degree of substitution of the OSA esterified starch obtained in Example 7 was tested in the same manner as in Example 1, and the DS result was 0.0174.

[0088] (ii) The resistant starch content of the cross-linked starch obtained in Example 8 was determined in exactly the same manner as in Example 4. The results are shown in Table 3.

[0089] Table 3 Verification of the optimal preparation process of banana and taro esterified starch and cross-linked starch

[0090] Reaction temperature (℃) Reaction time (h) pH result Esterified starch 38 5 8.5 DS0.0174±0.012 Cross-linked starch 48 3 11.5 Resistant starch content 73.1% ± 0.146

[0091] It can be seen from Table 3 that the verification results are close to the prediction results, indicating that the preparation process has good stability. The above results show that the process is feasible and has strong operability.

[0092] (III) The OSA esterified starch and cross-linked starch obtained in Examples 7 and 8 were observed under a SEM electron microscope, with banana and taro starch as a control. The results are shown in FIG. Figure 5 , Figure 5Part A is the SEM electron microscope photo of banana and taro starch, Part B is the SEM electron microscope photo of OSA esterified starch, and Part C is the SEM electron microscope photo of cross-linked starch. The scale bars in the figures are all 10 μm.

[0093] Depend on Figure 5 It can be seen that the OSA-esterified starch granules retain their original structure and size compared to the native taro starch granules. However, the surface of the esterified starch granules appears rough due to alkaline attack, which leads to pitting or groove corrosion, and most of the surface pores are located inside the granules, which can serve as water pipes connecting the outside of the granules and the surface. These non-crystalline water channels are vulnerable to attack by OSA groups, allowing OSA reagents to react with them and penetrate their interiors through these channels.

[0094] The surface of the cross-linked starch granules showed a peel-like appearance, with small molecule granules connecting to form larger granule clusters. This indicates that bridges were formed between starch molecules by reacting with multiple functional groups of the cross-linking agent.

[0095] (IV) The OSA esterified starch and cross-linked starch obtained in Examples VII and VIII were observed by infrared, DSC and XRD, with banana and taro starch as a control. The results are shown in Tables 4 and Figure 6 Part A is the infrared spectra of OSA esterified starch, cross-linked starch and banana starch, Part B is the DSC results of the three, and Part C is the XRD results of the three.

[0096] Table 4 Infrared, DSC and resistant starch content determination results

[0097]

[0098] Depend on Figure 6 As can be seen from the A part, compared with the original banana and taro starch, OSA esterified starch has a higher -1 and 1573cm -1 There is a new characteristic peak at 1573cm -1 The characteristic peak at is due to RCOO - Asymmetric stretching vibration, 1724cm -1 The stretching vibration at the C=O position of the ester carbonyl group indicates that an esterification reaction has occurred between the OSA group and starch.

[0099] Canna starch and cross-linked starch have almost the same chemical bonds, but their absorption peaks are very different. -1 The intramolecular hydrogen bonds that produce the peak at 995-1050cm are stronger in the original starch and weaker in the cross-linked starch. This is because cross-linking increases chemical bonds while reducing intramolecular hydrogen bonds. -1It is the POC stretching vibration absorption band. With the introduction of the phosphate group, it can be observed that the absorption peak intensity of the cross-linked starch increases at this location. This may be because the phosphate group replaces the hydrogen bond on the hydroxyl group of the starch molecule, so the hydroxyl group in the starch molecule is converted into a phosphodiester bond while still maintaining the original characteristic absorption peak.

[0100] Depend on Figure 6 It can be seen from part B that after esterification modification, a large number of OSA groups are introduced into the natural starch molecules, which weakens the hydrogen bonds between the starch molecules, enables the starch granules to absorb water and swell at a relatively low temperature, and reduces the energy required for granule gelatinization, i.e., To and Tp. The Tc and ΔH of OSA-esterified starch are reduced.

[0101] From Table 4 and Figure 6 As can be seen from the C section, cross-linked starch melts in a higher and narrower temperature range than native starch, which is consistent with the well-known fact that cross-linked starch has a higher transition temperature and lower transition enthalpy than parent starch. The higher Tp is caused by preventing the coordinated melting of crystals in starch granules.

[0102] OSA-esterified starch exhibits typical B-type crystal structure characteristics, indicating that the OSA esterification reaction does not change the crystal structure of starch. However, the relative crystallinity of the raw starch is significantly reduced. The study found that the OSA group can penetrate the crystalline region of starch granules and react with starch molecules, causing changes in the ordered structure of starch molecules, thereby affecting the relative crystallinity of starch granules to a certain extent.

[0103] The characteristic diffraction peaks of cross-linked starch decreased at 22.26° and 24.02°, but the structure of cross-linked starch did not change compared with native starch. The results showed that cross-linking with STMP / STPP mainly occurred in the amorphous region and did not change the crystalline region of starch granules.

[0104] The digestibility of esterified starch comes from the hydrophobicity and steric hindrance of the OSA group, which slows down the α-amylase that contacts the starch molecules, so esterification mainly reduces the content of rapidly digestible starch (RSD). As the starch is hydrolyzed, the structure of the starch is destroyed and the digestion rate gradually accelerates.

[0105] The addition of STMP / STPP crosslinkers reduces the swelling power of starch granules, thereby reducing enzymatic hydrolysis. On the other hand, crosslinkers introduce phosphate groups on starch chains, which increases the steric hindrance between starch molecules and hinders the formation of starch-amylase complexes.

[0106] Therefore, two types of IV-type resistant starch, esterified starch and cross-linked starch, were successfully prepared using the optimized parameter combination of the present invention, the yield of resistant starch was high, the degree of substitution of the prepared esterified starch reached 0.0174, and the resistant starch content in the cross-linked starch was measured to be 73.1%, which can be used for the preparation of IV-type banana and taro resistant starch; the provided preparation and optimization methods are simple and easy to operate, mild conditions, safe and effective, low requirements for instruments and equipment, and suitable for industrial production; no toxic and harmful raw materials and products are generated, the prepared resistant starch does not have safety hazards, and can be applied to health foods and medicines.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. Two types of IV banana and taro resistant starch, characterized by: The two types of IV banana and taro resistant starches are esterified starch prepared from OSA and cross-linked starch prepared from STPP and STMP.

2. The method for preparing two types of IV banana and canola resistant starches as claimed in claim 1, characterized in that: Here are the steps: S1. Preparation of esterified starch Disperse banana and taro starch in water, incubate in a water bath, adjust the pH to 8.5, then slowly add OSA, stirring while adding, stabilize the pH at 8.5-9.0 for 3-6 hours, then adjust the pH to 6.5, centrifuge to obtain the precipitate, wash the precipitate with a large amount of distilled water, and dry it at 40°C for 24 hours; S2. Preparation of cross-linked starch Add banana and cantaloupe starch dispersion water to an aqueous solution containing STMP, STPP and sodium sulfate, stir the mixture at a certain temperature for a certain period of time, adjust the pH to 8.0-12, and adjust the pH to 6.5 after a certain period of reaction. Centrifuge to obtain the precipitate, wash with a large amount of deionized water, and dry at 40°C overnight.

3. The method for preparing two types of IV banana and taro resistant starch according to claim 2, characterized in that: In the step S1, the banana and taro starch in the banana and taro starch dispersion accounts for 35% of the dispersion mass, the water bath incubation temperature is 30-45° C.; the OSA is slowly added within 1 hour, and the added mass of OSA is 3% of the banana and taro dry starch; the centrifugal condition is 4000r, 10min.

4. The method for preparing two types of IV banana-taro resistant starch according to claim 2, characterized in that: In the step S2, the banana-taro starch in the banana-taro starch dispersion accounts for 35% of the dispersion mass; the concentrations of STMP, STPP and sodium sulfate in the aqueous solution containing STMP, STPP and sodium sulfate are 50 g / L, 0.5 g / L and 40 g / L respectively; the stirring temperature is 30-50° C., and the stirring time is 30 min; the reaction is carried out for 3-5 h at pH 11; and the centrifugation conditions are 4000 r for 10 min.

5. The method for preparing two types of IV banana-taro resistant starch according to claim 2, characterized in that: The washing with a large amount of distilled water / deionized water refers to adding 1 volume of distilled water / deionized water to the precipitate, resuspending the precipitate and centrifuging at 4000r for 10min, and repeating the above washing process 2-3 times.

6. The method for optimizing the preparation method of two types IV banana and canola resistant starches according to any one of claims 2 to 5, characterized in that: Here are the steps: 1) Conduct preliminary experiments with reference to the preparation methods of resistant starch from other sources; 2) performing substitution degree determination or resistant starch content determination; 3) Conduct a single factor study For the preparation of esterified starch, four factors including different OSA addition amount, reaction temperature, reaction time and pH were selected for single factor investigation; For the preparation of cross-linked starch, three factors, pH, reaction temperature and reaction time, were selected for single factor investigation; 4) Perform response surface optimization Based on the results of single factor experiments, three factors, namely reaction temperature, reaction time and pH, and the interval around the merit values ​​of the three factors obtained in the single factor experiments were selected for optimization. The preparation process parameters were optimized by response surface design using the substitution degree determination results / resistant starch content as indicators. 5) Data analysis to obtain the optimal parameter combination; 6) Evaluate the optimal parameter combination by determining the degree of substitution or the resistant starch content.

7. The optimization method for preparing two types of IV banana and taro resistant starch according to claim 6, characterized in that: In the single factor investigation of the preparation of esterified starch in the step 3), different OSA addition amounts are 2%, 3%, 4%, 5%, and 6%, different reaction temperatures are 25°C, 30°C, 35°C, 40°C, and 45°C, different reaction times are 2h, 3h, 4h, 5h, and 6h, and different pH values ​​are 7.5, 8.0, 8.5, 9.0, and 9.5; in the single factor investigation of the preparation of cross-linked starch, different pH values ​​are 7, 8, 9, 10, and 11, different reaction temperatures are 35°C, 40°C, 45°C, 50°C, and 55°C, and different reaction times are 1h, 2h, 3h, 4h, and 5h.

8. Use of the resistant starch prepared by the method for preparing two types of IV banana and canola resistant starch according to any one of claims 2 to 5 in health foods and medicines.

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