Synchronous preparation method of cross-linked esterified broken rice porous starch

Abstract

According to the synchronous preparation method of the cross-linked and esterified broken rice porous starch, the cross-linked and esterified broken rice porous starch prepared by a synchronous method is obtained by optimizing a porous starch modification process through a cross-linking and esterifying composite modification method, and the obtained composite modified starch product has relatively good oil absorption rate and stability; and adsorption and embedding of functional substances as a wall material of the microcapsule are facilitated. The method comprises the following steps: selecting broken rice porous starch prepared by a compound enzyme method as a raw material for later use; the preparation method comprises the following steps: uniformly mixing and stirring starch and a NaCl solution according to a weight ratio, adding sodium trimetaphosphate, adjusting the pH value by using an alkaline solution, and then stirring; after the cross-linking reaction is finished, adding an esterifying agent into the solution prepared in the step 1, adjusting the pH value by using an alkaline solution, stirring, adjusting the pH value to be neutral by using an HCl solution, and terminating the reaction; and carrying out suction filtration washing, drying, grinding and sieving on the product after the cross-linking esterification reaction to obtain the cross-linking esterification broken rice porous starch ester.

Description

Technical Field

[0001] The invention relates to a synchronous preparation method of cross-linked esterified broken rice porous starch, and specifically belongs to the technical field of modified starch. Background Art

[0002] The particle structure of broken rice porous starch is destroyed to a certain extent after microporation. Its gelatinization temperature, freeze-thaw stability, shear resistance and particle firmness are lower than those of native starch. To improve these structural characteristics, cross-linking modification and esterification modification can be used to enhance the structural stability and adsorption performance.

[0003] At present, a patent (application number: CN201010286936.7) proposes a preparation method of cross-linked octenyl succinate cassava starch ester, which uses cassava starch as a raw material, sodium trimetaphosphate as a cross-linking agent, and octenyl succinic anhydride as an esterifying agent, and extrude the cassava starch ester through a twin-screw extruder, and then dry, cool, and crush to obtain the cross-linked octenyl succinate cassava starch ester. The method requires a twin-screw extruder, which is costly, and the reaction conditions and product quality of the method are also difficult to control, and is not suitable for industrial production.

[0004] Zhang Jiaqi et al. (Jiangnan University, 2011) proposed to use commercially available rice starch as raw material and adopt a step-by-step method to prepare cross-linked esterified porous starch. The optimal process conditions are: 0.6% mass fraction of phosphorus oxychloride crosslinking agent, 90min crosslinking time, pH 11, crosslinking temperature 35°C, 2% esterification agent addition, esterification temperature 35°C, esterification pH 8.5, and esterification time 2h. This method uses rice porous starch as raw material, which is costly. The crosslinking agent phosphorus oxychloride used is highly corrosive and inconvenient to use, and the pH required for the reaction is also high. In addition, the step-by-step reaction requires the cross-linked starch to be separated first through neutralization, centrifugation, washing and drying, and then the esterification reaction is carried out. The process time is long, resulting in increased production costs and increased energy consumption. Summary of the invention

[0005] The purpose of the present invention is to provide a method for synchronously preparing cross-linked esterified broken rice porous starch, so as to improve the adsorption performance and shear resistance of the porous starch and expand the application of the porous starch in the food field.

[0006] In order to solve the above technical problems, the preparation steps adopted by the present invention include:

[0007] Step 1, selecting broken rice porous starch prepared by a composite enzyme method as a raw material for standby use;

[0008] Step 2, the starch and NaCl solution are mixed and stirred evenly according to the weight ratio, sodium trimetaphosphate is added, the pH value is adjusted with an alkaline solution, and then stirred;

[0009] Step 3: After the cross-linking reaction is completed, an esterifying agent is added to the solution prepared in step 1, the pH value is adjusted with an alkaline solution, the mixture is stirred, and the pH value is adjusted to neutral with an HCl solution to terminate the reaction;

[0010] Step 4, filtering, washing, drying, grinding and sieving the product after the cross-linking esterification reaction to obtain cross-linked esterified broken rice porous starch ester;

[0011] Furthermore, by using japonica rice porous starch as raw material, sodium trimetaphosphate as a cross-linking agent, and octenyl succinic anhydride as an esterifying agent, the cross-linking reaction is first completed in a reactor, and the cross-linked porous starch product is not separated, and the esterification reaction is continued to be completed simultaneously, and the corresponding product is obtained through filtration, washing, drying, grinding and sieving, wherein the role of NaCl is to prevent the decomposition of sodium trimetaphosphate and the swelling of starch.

[0012] The mass of sodium trimetaphosphate added in step 2 is 2% of the dry basis of starch, the mass fraction of NaCl solution is 2%, and the mass fraction of starch milk is 30%;

[0013] The alkaline solution described in step 2 is a NaOH solution, the concentration of the NaOH solution is 4wt%, the pH value is adjusted to 8.5-9.0 with the NaOH solution, and the stirring is carried out at 40°C, and the stirring method is to react for 2h under magnetic stirring;

[0014] The esterifying agent in step 3 is octenyl succinic anhydride, the amount of the esterifying agent added is 3% of the dry basis of starch, and the esterifying agent is added slowly drop by drop;

[0015] The alkaline solution in step 3 is a NaOH solution, the concentration of the NaOH solution is 3wt%, the pH value is controlled within the range of 8.4-8.8 with the NaOH solution, the stirring is carried out at 35°C, the stirring method is to react for 2h under magnetic stirring, and the concentration of the HCl solution is 0.5mol / l;

[0016] The pH value adjustment in step 3 is divided into three stages, and the pH value is adjusted every 0.5h, and the pH value control range is 8.4-8.8;

[0017] The washing in step 4 refers to two ethanol washings and two distilled water washings, wherein the concentration of ethanol is 70%-90%, the drying is carried out at 40°C, and the sieve used for sieving is 100 mesh;

[0018] Furthermore, the effect of preparing cross-linked esterified broken rice porous starch is improved by refining the operating data.

[0019] The beneficial effects of the present invention are:

[0020] 1. Through the cross-linking esterification composite modification method, the production cost is reduced, the reaction time is shortened, the preparation process is simplified, the adsorption performance and shear resistance of porous starch are improved, and the application of porous starch in the food field is expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the SEM spectrum of the cross-linked esterified broken rice porous starch of the present invention;

[0022] Figure 2 It is the TG graph of the raw material and the cross-linked esterified broken rice porous starch of the present invention;

[0023] Figure 3 It is the DTG diagram of the raw material and the cross-linked esterified broken rice porous starch of the present invention;

[0024] Figure 4 It is an infrared spectrum diagram of the raw material and the cross-linked esterified broken rice porous starch prepared by the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the attached Figure 1-4 , clearly and completely describe the technical solutions in the embodiments. Figure 1-4 As shown, the preparation steps include:

[0026] Step 1, selecting broken rice porous starch prepared by a composite enzyme method as a raw material for standby use;

[0027] Step 2, 30% starch milk and 2% NaCl solution are mixed and stirred evenly, 2% sodium trimetaphosphate by weight of dry starch basis is added, the pH is adjusted to 8.5-9.0 with 4wt% NaOH solution, and the reaction is stirred at 40°C for 2h;

[0028] Step 3, after the cross-linking reaction is completed, add octenyl succinic anhydride in an amount of 3% of the starch dry basis to the solution prepared in step 1, the addition rate of octenyl succinic anhydride is slowly added drop by drop, and the pH is controlled within the range of 8.4-8.8 with a solution concentration of 3wt% NaOH solution, the pH value is adjusted in three stages, and the pH value is adjusted every 0.5h, and the pH value is controlled within the range of 8.4-8.8, and the reaction is stirred at 35°C for 2h, and the reaction is terminated by adjusting the solution concentration of 0.5mol / l HCl to neutral;

[0029] Step 4, the product after the cross-linking esterification reaction is filtered and washed twice with ethanol and twice with distilled water (the concentration of ethanol is 70%-90%), dried at 40° C., ground and sieved with a 100-mesh sieve to obtain a cross-linked esterified broken rice porous starch ester;

[0030] Embodiment 1:

[0031] (1) Raw materials: 50 g of broken japonica rice porous starch (prepared by hydrolyzing broken japonica rice starch with a composite enzyme);

[0032] (2) Cross-linking: prepare starch emulsion with porous starch and 2% NaCl solution on a starch dry basis; starch: NaCl = 1:2.33, add 1.0 g of sodium trimetaphosphate, adjust the pH value to 8.5-9.0 using 4% NaOH on a starch dry basis, heat the starch emulsion to 40° C. in a reactor, and stir for 2 h;

[0033] (3) Esterification: After the reaction in step (2) is completed, 1.50 g of octenyl succinic anhydride is diluted three times with anhydrous ethanol and added dropwise to the starch milk. The pH value is controlled within the range of 8.4-8.8 with 3% NaOH based on the dry starch basis. The pH value is adjusted every 0.5 h and the reaction is carried out for 2 h. After the reaction is completed, the pH value is adjusted to neutral with 0.5 mol / L HCl to terminate the reaction;

[0034] (4) Washing: After step (3) is completed, the product is washed twice with distilled water by suction filtration, and then washed twice with 70% ethanol to remove unreacted anhydride and generated salt;

[0035] (5) Drying: The product obtained in step (4) is placed in a 40° C. forced air drying oven and dried for 24 hours to obtain a cross-linked esterified broken rice porous starch ester;

[0036] (6) Grinding: The product obtained in step (5) is ground three times by a grinder and passed through a 100-mesh sieve, and placed in a sealed sample bag.

[0037] Embodiment 2:

[0038] (1) Raw materials: 50 g of broken japonica rice porous starch (prepared by hydrolyzing broken japonica rice starch with a composite enzyme);

[0039] (2) Cross-linking: The porous starch and a 2% NaCl solution on a starch dry basis are mixed into a starch emulsion: starch: NaCl = 1:2.33, 1.2 g of sodium trimetaphosphate is added, and the pH value is adjusted to 8.5-9.0 using a 4% NaOH solution on a starch dry basis. The starch emulsion is heated to 40° C. in a reactor and stirred for reaction for 2 h.

[0040] (3) Esterification: After the reaction in step (2) is completed, 1.25 g of octenyl succinic anhydride is diluted three times with anhydrous ethanol and added dropwise to the starch milk. The pH value is controlled within the range of 8.4-8.8 with 3% NaOH based on the dry starch. The pH value is adjusted every 0.5 h and the reaction is carried out for 2 h. After the reaction is completed, 0.5 mol / L HCl is added to neutral to terminate the reaction;

[0041] (4) Washing: After step (3) is completed, the product is washed twice with distilled water by suction filtration, and then washed twice with 70% ethanol to remove unreacted anhydride and generated salt;

[0042] (5) Drying: The product obtained in step (4) is placed in a 40° C. forced air drying oven and dried for 24 hours to obtain a cross-linked esterified broken rice porous starch ester;

[0043] (6) Grinding: The product obtained in step (5) is ground three times by a grinder and passed through a 100-mesh sieve, and placed in a sealed sample bag.

[0044] The cross-linked esterified broken rice porous starch is prepared by a synchronous method. After the preparation of the cross-linked porous starch is completed, the reaction is not terminated, and an esterifying agent is continuously added to complete the reaction to obtain a cross-linked esterified product, which can reduce the reaction time, production cost and energy consumption, and lay a good foundation for the industrial production of cross-linked esterified broken rice porous starch.

[0045] The samples are then subjected to performance tests, including:

[0046] 501. Determination of sedimentation volume;

[0047] The steps of determining the sedimentation volume include: accurately weighing 0.50g of starch sample (dry basis) in a 100mL beaker, adding 25mL of distilled water to prepare a starch milk with a starch dry basis of 2%, heating in a water bath at 82-85°C and stirring continuously, taking out and cooling to room temperature after keeping warm for 2min, taking 10mL of the paste liquid into two graduated centrifuge tubes respectively with a pipette, centrifuging at 4000r / min for 2min, taking out the centrifuge tubes, pouring the upper clear liquid into a 10mL measuring cylinder, reading the number of milliliters, calculating the sedimentation volume, performing two parallel measurements on the same sample, and taking the average value;

[0048] Sedimentation volume (mL) = 10-V (mL) (1)

[0049] In formula (1): V is the volume of the supernatant;

[0050] 502. Determination of degree of substitution (DS);

[0051] The steps for determining the degree of substitution (DS) include: accurately weighing 1.50g of sample into a 100mL beaker, adding 10mL of 95% ethanol and stirring thoroughly, dissolving for 10min, then adding 15mL of 2.5mol / L hydrochloric acid-ethanol solution and stirring evenly, standing for 30min for acidification, filtering, washing with 90% ethanol until there is no Cl- (AgNO3 test), transferring the washed sample into a 250mL conical flask, adding 100mL of distilled water and boiling water bath for 20min, dropping two drops of phenolphthalein, and titrating with 0.1mol / L standard NaOH solution while hot until pink. The formula for calculating the degree of substitution is as follows:

[0052] DS=0.1624A / (1-0.210A) (2)

[0053] A=CV / W (3)

[0054] In formula (2): A is the amount of NaOH standard solution with a concentration of 0.1 mol / L consumed per gram of octenyl succinate starch ester, in mol; 0.1624 is the millimolar mass of dehydrated glucose, in g / mmol; 0.210 is the millimolar mass of octenyl succinic anhydride, in g / mmol;

[0055] In formula (3), C is the molar concentration of the NaOH standard solution, in mol / L; V is the volume of the standard NaOH solution consumed by the sample titration; W is the mass of the sample, in g;

[0056] 503. Determination of oil absorption rate;

[0057] The steps for determining the oil absorption rate include: weighing 0.5g of sample into a 100mL beaker, mixing with excess oil, reacting in a 50℃ constant temperature water bath oscillator for 60min, using a sand core funnel m2 of known mass to filter until no oil drops, and recording the mass of the sand core funnel after filtration as m3.

[0058] Oil absorption rate (%) = (m3-m2-m1) / m1 (4)

[0059] In formula (4), m3 is the mass of the sand core funnel, porous starch and oil / water after filtration, m2 is the mass of the sand core funnel, and m1 is the mass of the sample;

[0060] 504. Determination of shear resistance;

[0061] The steps of measuring the anti-shear performance include: preparing a starch emulsion with a starch dry basis of 2% in a 100 mL beaker, stirring and heating the starch emulsion in a boiling water bath for different time periods, cooling to room temperature, and then measuring the viscosity of the starch paste;

[0062] 505. Determination of freeze-thaw stability;

[0063] The freeze-thaw stability determination steps include: preparing starch milk with a starch dry basis of 6%, heating the starch milk in a boiling water bath for 30 minutes, cooling to room temperature, taking a known mass of starch paste in a refrigerated centrifuge tube, freezing it in a refrigerator for 24 hours, taking it out and thawing it, and repeatedly freezing and thawing it until water precipitates or it becomes spongy. Centrifuge the thawed paste at 6000r / min for 20 minutes, discard the supernatant, and weigh the mass of the precipitate.

[0064] Water separation rate (%) = (paste weight - precipitate weight) / paste weight;

[0065] It can be concluded that cross-linked esterified porous starch, as a composite modified starch, has the advantages of both cross-linked starch and esterified starch, and has better shear resistance, freeze-thaw stability, thermal stability and adsorption properties than porous starch.

[0066] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for synchronously preparing cross-linked esterified broken rice porous starch, characterized in that: Specifically include: Step 1, selecting broken rice porous starch prepared by a composite enzyme method as a raw material for standby use; Step 2, the starch and NaCl solution are mixed and stirred evenly according to the weight ratio, sodium trimetaphosphate is added, the pH value is adjusted with an alkaline solution, and then stirred; Step 3: After the cross-linking reaction is completed, an esterifying agent is added to the solution prepared in step 1, the pH value is adjusted with an alkaline solution, the mixture is stirred, and the pH value is adjusted to neutral with an HCl solution to terminate the reaction; Step 4: The product after the cross-linking esterification reaction is filtered, washed, dried, ground and sieved to obtain cross-linked esterified broken rice porous starch ester.

2. The method for synchronously preparing a cross-linked esterified broken rice porous starch according to claim 1, characterized in that: The mass of sodium trimetaphosphate added in step 2 is 2% of the dry basis of starch, the mass fraction of NaCl solution is 2%, and the mass fraction of starch milk is 30%.

3. The method for synchronously preparing a cross-linked esterified broken rice porous starch according to claim 1, characterized in that: The alkaline solution described in step 2 is a NaOH solution, the concentration of the NaOH solution is 4 wt %, the pH value is adjusted to 8.5-9.0 with the NaOH solution, and the stirring is carried out at 40° C. The stirring method is to react for 2 hours under magnetic stirring.

4. The method for synchronously preparing a cross-linked esterified broken rice porous starch according to claim 1, characterized in that: The esterifying agent added in step 3 is octenyl succinic anhydride, the amount of the esterifying agent added is 3% of the dry basis of starch, and the speed of adding the esterifying agent is slow dropwise addition.

5. The method for synchronously preparing a cross-linked esterified broken rice porous starch according to claim 1, characterized in that: The alkaline solution in step 3 is a NaOH solution, the concentration of the NaOH solution is 3wt%, the pH value is controlled within the range of 8.4-8.8 with the NaOH solution, stirring is carried out at 35°C, the stirring method is to react for 2h under magnetic stirring, and the concentration of the HCl solution is 0.5mol / l.

6. The method for synchronously preparing cross-linked esterified broken rice porous starch according to claim 1, characterized in that: The pH value adjustment in step 3 is divided into three stages, and the pH value is adjusted every 0.5h. The pH value control range is 8.4-8.

8.

7. The method for synchronously preparing cross-linked esterified broken rice porous starch according to claim 1, characterized in that: The suction filtration and washing in step 4 refers to two ethanol washings and two distilled water washings, wherein the concentration of ethanol is 70%-90%, the drying is carried out at 40° C., and the screen used for sieving is 100 mesh.

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