Preparation method of jack fruit seed resistant starch based on hydro-thermal treatment

Abstract

The invention belongs to the technical field of starch processing, and particularly relates to a preparation method of jack fruit seed resistant starch based on hydro-thermal treatment. Comprising the following steps: uniformly mixing jack fruit seed starch and plasma activated water, then gelatinizing, continuously stirring until the jack fruit seed starch is completely gelatinized, then adding gallic acid, continuously stirring, and after the reaction is finished, cooling, cleaning, drying and sieving to obtain the jack fruit seed resistant starch, wherein the gelatinization is carried out under the condition that the temperature is 80-100 DEG C. According to the method, the characteristic that plasma activated water is acidic is utilized, the jack fruit seed starch is induced to be combined with more polyphenols through hydrothermal treatment, more V-shaped compounds are formed, and the compounds have more resistant starch content, can effectively inhibit the activity of digestive enzymes and remarkably reduce the in-vitro digestibility of the jack fruit seed starch.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of starch processing, and particularly relates to a preparation method of jackfruit seed resistant starch based on hydrothermal treatment. BACKGROUND

[0002] At present, polyphenol-starch complexes are generally prepared by hydrothermal treatment. By adjusting parameters such as water content, temperature and duration during the treatment process, the interaction can be changed. Under the conditions of high temperature and excessive water, starch will be gelatinized, the crystalline region will collapse, and the starch will lose rigidity and obtain flexibility. During the treatment process, starch is gelatinized, the granules are expanded, pores are formed and the pore volume is increased, so that polyphenols enter the interior of the granules and interact with the starch chains. However, the processing efficiency of the common processing technology of hydrothermal treatment is limited. Complete gelatinization will destroy the three-dimensional structure of the starch granules, reduce the binding cavity and the physical embedding capacity, and thus reduce the binding rate of starch and polyphenols. Plasma-activated water (PAW) is an acidic medium, and the acidic condition is more conducive to the combination of polyphenols and starch to form V-shaped complexes with stronger anti-digestive ability. Therefore, the present application uses plasma-activated water and heat modification technology in combination to improve the anti-digestive ability of starch. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a preparation method of jackfruit seed resistant starch based on hydrothermal treatment and the corresponding prepared jackfruit seed resistant starch to solve the problems of the prior art.

[0004] To solve the above technical problems, the technical solutions of the present application are as follows:

[0005] The first aspect of the present application provides a preparation method of jackfruit seed resistant starch based on hydrothermal treatment, comprising the following steps: uniformly mixing jackfruit seed starch and plasma-activated water, gelatinizing, continuously stirring until complete gelatinization, then adding gallic acid, continuing to stir, cooling, washing, drying, and sieving to obtain the jackfruit seed resistant starch.

[0006] The gelatinization is carried out at a temperature of 80-100 DEG C.

[0007] In some embodiments of the present application, the gelatinization is carried out at a temperature of 100 DEG C.

[0008] The mass-volume ratio of the jackfruit seed starch and the plasma-activated water is 1 g:10 mL.

[0009] Specifically, the preparation method of the jackfruit seed starch is as follows: the jackfruit seed is peeled by soaking in 0.1M NaOH for 5 min, pulping, and screening, and then the precipitate is obtained by standing and precipitating overnight. The precipitate is soaked in a 0.5 mol / L Na2S2O3·5H2O solution (1:1) for 36 h, and then centrifuged (5000 r / min, 5 min, 20 ℃) for multiple times, and the supernatant is discharged until there is no brown precipitate on the upper layer of the precipitate. Then, the precipitate is neutralized to neutral by 1.0 mol / L hydrochloric acid, washed by 50% ethanol, centrifuged (5000 r / min, 5 min, 20 ℃), and then dried by a blowing drying oven and screened to obtain the jackfruit seed starch.

[0010] Specifically, the preparation method of the plasma-activated water is as follows: 150 mL of distilled water is poured into a beaker, and then a plasma-activated water jetting probe is inserted into the beaker below the liquid surface, and the plasma-activated water used in the application can be obtained by keeping the power at 750 W for 2 min.

[0011] The stirring is performed at a speed of 200 r / min.

[0012] The addition amount of the gallic acid is 5% to 10% of the mass of the jackfruit seed starch.

[0013] In some embodiments of the application, the addition amount of the gallic acid is 10% of the mass of the jackfruit seed starch.

[0014] The second aspect of the application provides a jackfruit seed resistant starch.

[0015] The jackfruit seed resistant starch is prepared by the preparation method of the jackfruit seed resistant starch based on hydrothermal treatment according to the first aspect of the application.

[0016] Beneficial effects:

[0017] The application utilizes the acidic characteristics of the plasma-activated water, and combines the hydrothermal treatment to induce the jackfruit seed starch to combine with more polyphenols to form more V-shaped complexes, the complexes have more resistant starch content, can effectively inhibit the activity of digestive enzymes, and significantly reduce the in-vitro digestion rate of the jackfruit seed starch. BRIEF DESCRIPTION OF DRAWINGS

[0018] The above and / or other aspects of the application will become more apparent by describing in detail the preferred embodiments thereof with reference to the attached drawings.

[0019] Figure 1 The SEM image of the jackfruit seed starch-gallic acid complex under the PAW condition in the embodiments of the application.

[0020] Figure 2XRD pattern of jackfruit seed starch-gallic acid complex under PAW condition in the embodiment of the present application.

[0021] Figure 3 FT-IR pattern of jackfruit seed starch-gallic acid complex under PAW condition in the embodiment of the present application.

[0022] Figure 4 TGA and DTG patterns of jackfruit seed starch-gallic acid complex under PAW condition in the embodiment of the present application.

[0023] Figure 5 In-vitro digestion curve of jackfruit seed starch-gallic acid complex under PAW condition. DETAILED DESCRIPTION

[0024] In the following examples, the experimental methods are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0025] In the following examples, jackfruit seeds (Malaysia No. 1) are purchased from the Internet; α-amylase (50 U / mg) is purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.; Aspergillus niger starch glucosidase (100000 U / g) is purchased from Nanjing Laiye Biological Engineering Co., Ltd.; and the relevant chemical solvents used in the experiment are all of analytical purity.

[0026] Example 1: Preparation of jackfruit seed resistant starch

[0027] Extraction of jackfruit seed starch: jackfruit seeds were soaked in 0.1 M NaOH for 5 min to remove the skin, beaten and sieved, and then allowed to settle overnight. The precipitate was added to a 0.5 mol / L Na2S2O3·5H2O solution (1 g:1 mL) and soaked for 36 h, and then centrifuged multiple times (5000 r / min, 5 min, 20 ℃) to remove the supernatant until there was no brown precipitate on the top of the precipitate. Then, the precipitate was neutralized to neutral with 1.0 mol / L hydrochloric acid, washed with 50% ethanol, centrifuged (5000 r / min, 5 min, 20 ℃), and then dried in a blast drying oven and sieved to obtain jackfruit seed starch.

[0028] Preparation of plasma-activated water (PAW): 150 mL of distilled water was poured into a beaker, and then a PAW jetting probe was inserted into the beaker below the liquid surface, and PAW was obtained by maintaining the power at 750 W for 2 min.

[0029] Preparation of jackfruit seed resistant starch: 5.0 g jackfruit seed starch and 50 mL PAW were put into three marked conical flasks respectively. After mixing evenly, the mixture was gelatinized at 80 ℃ and continuously stirred at a speed of 200 r / min. After the starch solution was completely gelatinized, 0.25 g and 0.5 g of gallic acid (GA) were quickly added to two of the gelatinized starch pastes respectively, and then the stirring was continued at the same speed for about 1.5 h. After cooling to room temperature, the non-complexed GA was washed with ethanol to obtain the complex. Then the complex was freeze-dried, and the dried powder was sieved through a 100 mesh sieve to obtain the jackfruit seed resistant starch hydrothermally treated at 80 ℃, which was labeled as P-80, P-80-5%G and P-80-10%G respectively.

[0030] The gelatinization temperature was changed to 100 ℃, and the resistant starch hydrothermally treated at 100 ℃ was prepared under the same conditions, which was labeled as P-100, P-100-5%G and P-100-10%G respectively.

[0031] Example 2: Analysis of the surface particle structure of jackfruit seed resistant starch

[0032] The jackfruit seed resistant starch prepared in Example 1 was evenly coated on a sample stage with conductive tape, and the sample was gold sprayed and observed for the surface morphology of the starch sample particles using a field emission scanning electron microscope (Thermo, Verios G4 UC).

[0033] Figure 1 The SEM images of the jackfruit seed resistant starch under PAW conditions are shown in the figure, where A is the SEM image at 2500x, and B is the SEM image at 5000x. It can be seen from the figure that Figure 1 It can be seen that under the action of PAW, when the temperature is 80 ℃, the starch particles of sample P-80 are in the form of oval, polygonal or irregular particles, and the surface is sticky and aggregated into a block. When the temperature is 100 ℃, the starch particle morphology of sample P-100 disappears, and there are relatively rough holes, which may be due to the oxidation of PAW and high temperature leading to the fragmentation of starch particles. With the increase of GA addition amount and temperature, the connection of the block material becomes more and more compact. This may be due to the fact that after the structure of the starch particles is destroyed by PAW treatment, the network structure is induced under hydrothermal conditions, thereby promoting the adsorption of GA on the surface of the starch and enhancing the possibility of interaction between GA and the internal starch chains.

[0034] Example 3: Analysis of the long-range crystal structure of jackfruit seed resistant starch

[0035] The crystal characteristics of the starch samples prepared in Example 1 were determined by XRD, with a scanning rate of 4° / min and a 2θ range of 5-35°.

[0036] Figure 2 XRD pattern of resistant starch from jackfruit seed under PAW condition, wherein Figure 2 It can be seen that at a temperature of 80 ℃, the curve of the starch sample P-80 shows obvious peaks near 15°, 17°, 18° and 23°, respectively, which is a typical A-type crystalline structure. When the temperature rises to 100 ℃, the diffraction peaks of sample P-100 near 15°, 17°, 18° and 23° disappear, and new absorption peaks appear near 17.05° and 22.30°, and the crystalline structure is changed to B-type. It is possible that the active substances and high temperature under hydrothermal conditions in PAW have a double effect of decomposition and recombination on the crystal structure of starch.

[0037] At 80 ℃, the crystallinity RCof sample P-80 is 79.873%, and after adding GA, the RCof the compound sample P-80-5%G rises to 82.884%, while the RCof sample P-80-10%G drops to 57.808%. At a temperature of 100 ℃, the same trend is observed. The polyphenol and starch stack into organized microcrystals, thereby increasing the relative crystallinity of the starch. A large amount of GA leads to oversaturation of the phenolic acid content in the system, and the covalent bond of GA limits the molecular motion of the starch chain, resulting in an increase in the amorphous state content. Therefore, when the amount of GA added is 10%, the relative crystallinity of the compound decreases sharply.

[0038] Example 4: Analysis of the short-range crystal structure of jackfruit seed resistant starch

[0039] The starch sample prepared in Example 1 was mixed with potassium bromide in a ratio of 1:100 to prepare a thin slice, and then the structure of the starch sample was analyzed by an FT-IR spectrometer under the condition that the scanning range of the wavelength was 4000~400 cm -1 , and the resolution was 4 cm -1 .

[0040] Figure 3 FT-IR pattern of resistant starch from jackfruit seed under PAW condition, wherein Figure 3 It can be seen that under the action of PAW, after being compounded with GA, the peak intensity at wavelengths of 3417 cm −1 and 2931 cm −1 increases, indicating an increase in hydrogen bonds in the system. It is possible that under the action of PAW and hydrothermal conditions, the generated compound has a more stable spatial configuration and more hydrogen bonds. The peak intensity ratio (R) at wavelengths of 1047 and 1022 cm −1 indicates the short-range order in the starch. At a temperature of 80 ℃, R P-80-5%G >R P-80 >R P-80-10%G, which indicates that GA molecules interact with starch molecules to form more ordered short-range ordered structure at appropriate GA concentration.

[0041] Example 5: Analysis of the thermal stability of jackfruit seed resistant starch

[0042] The thermal properties of the starch samples prepared in Example 1 were determined using a thermogravimetric (TGA) analyzer. 5.0 mg of sample was weighed and heated at a rate of 10 °C / min from 30 °C to 600 °C while maintaining a nitrogen flow rate of 20 mL / min. The thermogravimetric analysis curve (TGA curve) and the differential thermogravimetric curve (DTG curve) were obtained.

[0043] Figure 4 TGA and DTG graphs of jackfruit seed resistant starch under PAW condition, wherein A is the TGA graph and B is the DTG graph, from Figure 4 It can be seen that all samples experienced two different mass loss stages during heating. In the first stage (30 °C~160 °C), the mass loss of all samples decreased from more than 90% to about 80%, which was due to the evaporation of water in the sample. The second stage occurred at (200 °C~400 °C), in which starch depolymerization generated glucose and some polyhydroxylated glycosylation products. From Figure 4 It can be seen from B that the degradation temperature of jackfruit seed starch samples was 280~320 ℃, while the degradation temperature of the complex samples was 340~380 ℃. The degradation temperature increased with the increase of GA addition, indicating that the thermal stability of the complex samples was improved.

[0044] Example 6: Determination of the in vitro digestion characteristics of jackfruit seed resistant starch

[0045] 25.0 mg of the starch sample prepared in Example 1 was mixed with 5 mL of sodium acetate buffer and equilibrated in a 37 °C water bath for 15 min. Then, the starch sample solution was mixed with 2 mL of α-amylase and 0.5 mL of Aspergillus niger starch glucosidase, and continuously stirred (180 r / min) in a 37 °C water bath. Then, 0.5 mL of the digestion solution was extracted at 0, 10, 20, 30, 60, 90, 120, and 180 min, respectively. The hydrolysis products at different time intervals were mixed with an equal amount of sodium carbonate to terminate the reaction, and then the mixture was centrifuged at 5000 g for 10 min to obtain the supernatant. The absorbance was measured at 540 nm by DNS method to determine the reducing sugar content. The glucose contents hydrolyzed at 20 min and 120 min were marked as G 20 , G 120 , rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) contents were calculated as follows:

[0046] RDS (%) = (G 20 - F) x 0.9 / T x 100

[0047] SDS (%) = (G 120 - G 20 ) x 0.9 / T x 100

[0048] RS (%) = 100% - (RDS (%) + SDS (%))

[0049] wherein G 20 , G 120 represent the glucose content at 20 and 120 min of hydrolysis, respectively; F represents the free glucose content; and T is the starch mass.

[0050] Figure 5 is the in vitro digestion curve of resistant starch of jackfruit seed under PAW condition, and Table 1 is the nutritional component content, RC and R of resistant starch of jackfruit seed under PAW condition. Among them, RDS is the content of rapidly digestible starch; SDS is the content of slowly digestible starch; RS is the content of resistant starch; RC is the relative crystallinity, and R is the ratio of the peak intensity of 1047 and 1022 cm -1 .

[0051] Table 1 Nutritional component content, RC and R of jackfruit seed starch-gallic acid complex under PAW condition

[0052]

[0053] Note: The results are expressed as "mean ± standard deviation" (n = 3); different letters in the same column indicate significant differences (p < 0.05).

[0054] It can be seen from the digestion curve that the digestion rate of sample P-80 (54.014%) is significantly smaller than that of sample P-100 (58.904%) at the digestion termination time (180 min). This is probably because active oxygen and active nitrogen and other substances in PAW cause the breakage of starch molecular chains, and the partial gelatinization of starch granules under hydrothermal conditions, so that the starch is more easily decomposed by enzymes. When the temperature in PAW is 80 ℃, the contents of RDS, SDS and RS of sample P-80 are 27.732%, 1.201% and 71.067% respectively. When the temperature is 100 ℃, the contents of RDS, SDS and RS of sample P-100 are 28.338%, 1.018% and 70.645% respectively. With the increase of temperature and the increase of the amount of GA added, the RDS of the complex shows a decreasing trend, and the RS is on the contrary. Among them, the content of RDS of the complex P-100-10% decreases to the lowest 18.738%, and the content of RS increases to 78.832%. It shows that GA enters the hydrophobic cavity of the starch molecule to form a stronger crystal structure, which is conducive to improving the resistance of starch to digestive enzymes. In addition, it may also be related to the inhibition of GA released during digestion on digestive enzymes.

[0055] In summary, when the PAW cooperates with the hydrothermal temperature of 100 ℃, the effect of adding 10% of gallic acid on the modification of jackfruit seed starch is the most significant. The PAW and GA cooperate to treat the jackfruit seed starch, which can significantly increase the particle size of the jackfruit seed starch, make the surface rough and increase the number of holes. New groups are generated in the complex, and no changes in chemical structure are caused. However, the crystal type of the complex changes from A type to B type, and the relative crystallinity shows a trend of first increasing and then decreasing. In addition, the TGA result analysis shows that the thermal stability of the complex is improved, and the decomposition temperature and degradation temperature are significantly increased. The light transmittance of the complex is improved, and the aging process of the starch is delayed. More importantly, the complex formed by gallic acid and starch can effectively inhibit the activity of digestive enzymes, and significantly reduce the in vitro digestion rate of jackfruit seed starch.

[0056] The present application provides a method for preparing resistant starch of jackfruit seed based on hydrothermal treatment. There are many methods and ways to realize this technical solution, and the above description is only the preferred embodiment of the present application. It should be pointed out that for ordinary technical personnel in this technical field, without departing from the principle of the present application, some improvements and refinements can be made, which should be regarded as the protection scope of the present application. The components not explicitly described in the embodiment can be realized by using existing technology.

Claims

1. A method for preparing resistant starch from jackfruit seeds based on hydrothermal treatment, characterized in that, The process includes the following steps: jackfruit seed starch and plasma-activated water are mixed evenly and then gelatinized. The mixture is stirred continuously until it is completely gelatinized. Gallic acid is then added and the mixture is stirred continuously until the reaction is complete. The mixture is then cooled, washed, dried, and sieved to obtain the jackfruit seed resistant starch. The gelatinization process is carried out at a temperature of 80-100 ℃.

2. The preparation method according to claim 1, characterized in that, The gelatinization is performed under the following conditions: temperature 100 ℃.

3. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the jackfruit seed starch to the plasma-activated water is 1 g: 10 mL.

4. The preparation method according to claim 1, characterized in that, The stirring conditions are: a rotation speed of 200 r / min.

5. The preparation method according to claim 1, characterized in that, The amount of gallic acid added is 5% to 10% of the mass of jackfruit seed starch.

6. The preparation method according to claim 5, characterized in that, The amount of gallic acid added is 10% of the mass of jackfruit seed starch.

7. The resistant starch of jackfruit seeds prepared by the preparation method according to any one of claims 1 to 6.

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