CN112321853A - Crystallinity-controllable starch nanoparticle, preparation method and application - Google Patents

Crystallinity-controllable starch nanoparticle, preparation method and application Download PDF

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CN112321853A
CN112321853A CN202011202006.9A CN202011202006A CN112321853A CN 112321853 A CN112321853 A CN 112321853A CN 202011202006 A CN202011202006 A CN 202011202006A CN 112321853 A CN112321853 A CN 112321853A
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starch
crystallinity
solvent
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nanoparticles
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林日辉
樊艳叶
周丽红
曾艺君
姚先超
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Guangxi University for Nationalities
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08J2303/00—Characterised by the use of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08J2303/02—Starch; Degradation products thereof, e.g. dextrin

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Abstract

The invention belongs to the technical field of starch nanoparticle preparation, and discloses a starch nanoparticle with controllable crystallinity, a preparation method and application thereof. According to the invention, a theoretical basis is provided for the development of a new process for preparing the starch nanoparticles with controllable crystallinity, controllable structural rigidity and good thermal stability by controlling the crystallization formation mechanism in the process of preparing the starch nanoparticles by a nano-sedimentation method; and provides an important idea for the development of nano preparation technology of other bio-based polymers.

Description

Crystallinity-controllable starch nanoparticle, preparation method and application
Technical Field
The invention belongs to the technical field of starch nanoparticle preparation, and particularly relates to a crystallinity-controllable starch nanoparticle, a preparation method and an application thereof.
Background
Starch is one of the most abundant biomass resources in nature, and in order to widen the application field of natural starch, people utilize physical, chemical, enzymatic or composite methods to treat the original starch so as to improve the structural and functional characteristics of the original starch. Among them, the nano modification of starch is an important analysis direction for the deep processing of starch at present. The nano modification of starch is to reduce the grain size of original starch from micron level to nanometer level by chemical, physical or biological methods, and the nano starch obtains physical and chemical properties which are not possessed by conventional starch grains due to the small size effect, surface effect, quantum size effect, macroscopic quantum tunneling effect and the like of nano-scale grains, so that the application performance of starch can be improved.
The nano starch can be used as a bioactive substance carrier and applied to the field of biological medicines. Santander-Ortega et al prepared nanoparticles using propyl starch derivatives tested the encapsulation and release characteristics of flufenamic acid, testosterone and caffeine, respectively, to achieve higher drug encapsulation efficiency, nearly linear release profile of hydrophobic drugs, and significantly enhanced flufenamic acid as a transdermal delivery system. The starch nanoparticles are used as an insulin administration carrier, so that the concentration of plasma insulin (the peak value of 258 mu IU/ml appears in 1 hour of administration) is effectively controlled, and the effect of reducing blood sugar is still remarkable after the blood sugar lasts for 6 hours. The hollow nano starch with the diameter range of 30-300nm is prepared by using the gel starch, the doxorubicin hydrochloride loading efficiency is up to 97.56%, the loading capacity is up to 37.12%, and the hollow nano starch can be used as a drug carrier for treating related cancers. The beta-carotene-loaded starch nanoparticles with the average diameter of less than 900nm are obtained by dropwise adding ethanol containing the beta-carotene into the starch paste, the water dispersity and the stability of the starch nanoparticles are good, and the stability of the beta-carotene against chemical oxidation is enhanced. In addition, the nano-starch can also be used as a carrier of various substances such as enzyme preparations, essences and the like.
The nano starch can be used as a filler for strengthening a polymer matrix and applied to the field of novel materials, and the application performance of natural or synthetic high molecular materials is improved. The natural rubber is used as a matrix, the waxy corn starch nanoparticles are used as a reinforcing filler to prepare the composite material, the elastic modulus is obviously improved, and the relaxation modulus at room temperature is 75 times that of the unfilled matrix. The nano starch/ethylene-vinyl acetate rubber composite material prepared by using the nano starch with the grain diameter of about 130nm improves the physical properties of vulcanized rubber, such as tensile strength, hardness, 300 percent stress at definite elongation and the like. The 500nm acetylated starch nanoparticles are used for preparing the thermoplastic starch film, so that the water vapor permeability and the water absorption of the film can be reduced, and the Young modulus and the thermal stability of the film are improved. The starch nanoparticles are respectively used for preparing binary blends with the lambda-carrageenan and the xanthan gum, so that the viscoelasticity and the stability of the blend are improved. The nano starch can also be used as a matrix for preparing materials. The composite film is prepared by taking corn nano-starch as a matrix, glycerol as a plasticizer and cellulose nano-crystal as a reinforcing agent and adopting a tape-casting film forming method, the formed film is flat and smooth, uniform and stable, the tensile strength of the composite film reaches 20.18MPa, and the composite film has a good application prospect in the field of edible packaging. In addition, the nano-starch can also be applied to the fields of wastewater treatment, papermaking, emulsion stabilizers, food additives and the like. The starch nanocrystal grafted and modified by stearate is used as an adsorbent, the adsorption capacity of the starch nanocrystal on aromatic organic matters in water reaches 150-900 mu mol/g, and a fixed bed device is utilized for multiple adsorption-desorption cycles without loss of adsorption capacity. The corn nano-starch is used as a coating adhesive and applied to low-weight coated paper, and is directly dispersed and proportioned with the pigment in a dry powder form, so that the water retention performance of the coating is improved by 62.6%, and the printing surface strength is improved by 12.9%. The octenyl succinic acid modified corn nano starch is used for preparing the pickering emulsion, the size of the liquid drop is 0.5 to 45 mu m, and the stability of the anti-emulsion is effectively improved. The modified starch-based nano-particles are stable in an oil-in-water (O/W) Pickering emulsion system, and the emulsion is stored for 30 days without phase separation. In conclusion, the nano starch has the characteristic of nano size, and has the advantages of wide sources of starch, reproducibility, good biocompatibility and degradability, safety, no toxicity, no immunogenicity and the like, so that the nano starch has wide application prospects, and particularly has high requirements on safety and degradability in the field. Therefore, nano-starch preparation has become a hotspot of current nanotechnology analysis.
Similar to the preparation method of other nano materials, the preparation of the starch nanoparticles can also be divided into two routes of 'top-down' and 'bottom-up'. "top-down" is the preparation of starch nanoparticle materials by physical or chemical means (hydrolysis and mechanical milling, etc.) to reduce the size of the starch particles; the bottom-up method is to prepare the starch nanoparticle material by assembling starch molecules as basic units (such as a nano-sedimentation method, a reverse microemulsion method and the like). Hydrolyzed starches are high polysaccharides formed by the dehydration condensation of glucose molecules, and include amylose having only α -1,4 glucosidic bonds and amylopectin having α -1,6 glucosidic bonds in addition to α -1,4 glucosidic bonds. The straight and branched starch molecules are arranged in radial direction in the starch granule, and a structure of alternating layers of crystalline regions and amorphous regions is generated. Wherein the layered structure of the amylopectin double helix arrangement constitutes the crystalline regions of the starch and the amylose, disordered amylopectin and the branch points of the starch chain together constitute the amorphous regions of the starch. Treating starch granules by using acid, enzyme or enzyme/acid combined hydrolysis method, decomposing and removing amorphous regions of the granules and enabling the size of the amorphous regions to reach the nanometer level, namely starch nanocrystals. The starch nanoparticles prepared by the hydrolysis method have high crystallinity, compact structure, high rigidity and better acid resistance; however, the particles are mostly in a sheet structure and are easy to aggregate to form fine particles. Optimizing the hydrolysis preparation condition of the starch nanocrystal, and reactingThe 5d yield was only 15%. Therefore, the starch nanoparticles prepared by the hydrolysis method are not satisfactory in the aspects of reaction efficiency, product yield, product morphology control and the like. The mechanical method for preparing the starch nanoparticles is mainly used for crushing the starch particles through the actions of homogenizing, extruding, rubbing, shearing and the like so as to reduce the size of the starch particles to a nanometer level. Ethanol is used as a medium, and a grinding method is adopted to prepare the starch nanoparticles with the average particle size of 100 nm. With ZrO2The medium is prepared by a high-energy ball mill to obtain potato starch nanoparticles with the average particle size of 120 nm. The starch granule size is reduced to 10-20nm using high pressure homogenization technique under a pressure of 207 MPa. The starch granules with the average grain diameter of about 160nm are prepared by optimizing the conditions of extrusion temperature, screw rotation speed, torque, starch water content and the like. The mechanical method for preparing the starch nanoparticles reduces the use of chemical reagents, has simple and convenient operation, high yield and small or even disappeared degree of crystallinity of the product, has better adsorption property compared with the original starch, and can be used for biomedical materials. However, the mechanical method has high requirements on equipment, large power consumption, long treatment time, irregular particle shape and wide size distribution, and is limited in industry to a certain extent.
The nano-settling method is a method of dissolving a polymer in a solvent (good solvent) to form a uniform polymer phase, and then transferring the polymer solution into another solvent (non-solvent), or adding the non-solvent into the good solvent in which the polymer is dissolved, so that a high molecular polymer is precipitated to form nano-particles. The morphology and size of the particles prepared by the sedimentation method are not only related to the source of starch, but also related to the dosage of ethanol. The nano-sedimentation method is adopted to prepare the starch nano-particles by taking 7 starches with different sources as raw materials, and the smaller the particles of the raw starch are, the smaller the particle size of the product is. Ethanol is used as a non-solvent to prepare the starch nanoparticles with the size distribution of 50-300 nm. A series of size-controllable acetylated starch nanoparticles are prepared by taking acetone as a non-solvent, and experiments show that the linear relation between the theoretical value of the polarity of a water and acetone mixture and the particle size is realized. The preparation of the starch nanoparticles is analyzed by taking DMSO as a solvent and taking methanol, ethanol, n-propanol, isopropanol, n-butanol and n-pentanol as non-solvents respectively, and the result shows that the stronger the affinity of the solvent and the non-solvent is, the smaller the particle size of the nanoparticles is. The grain size is reduced to 160nm by adjusting the ethanol dosage, reducing the amylose solution concentration, ultrasonic stirring in the precipitation process and other operations. In the preparation of sago starch nanoparticles by a sedimentation method, the size and the morphology of the particles are regulated by adding surfactants with different proportions, but the yield is low. The current analysis shows that in the process of preparing starch nanoparticles by a nano-sedimentation method, the selection and proportion of a solvent and a non-solvent, the concentration of starch milk and the molecular weight of starch all influence the particle size. The method is simple to operate, the size of the obtained nano particles is easy to control, the morphology is regular, but the concentration of the starch solution is low, a large amount of non-solvent is required, and the yield is low. The reverse microemulsion method comprises dispersing starch solution into organic solution incompatible with starch solution under external force (homogenizing, ultrasonic wave, etc.), adding surfactant to make two phases form uniform and stable water-in-oil structure, and crosslinking starch molecule under the action of crosslinking agent to form nanoparticles. Cyclohexane and chloroform are compounded to serve as a continuous phase, starch-N, N' -methylene bisacrylamide is dissolved in water to serve as a dispersed phase, and the starch nano microspheres with uniform size distribution and regular surfaces are prepared under the action of an initiator. After the starch microemulsion is homogenized for 5 times under the high pressure of 60MPa, the particle size is reduced to 123.3 nm. The starch ionic liquid solution is used as a water phase, cyclohexane is used as an oil phase, and epichlorohydrin is used as a cross-linking agent to prepare the starch nano-microsphere with the average grain diameter of 96.9 nm. The reverse microemulsion method for preparing starch nanoparticles has the advantages of simple operation, regular particle morphology, higher requirement on equipment and higher energy consumption, and a large amount of organic reagents are introduced to limit the application of nano products.
The enzymolysis regeneration method firstly utilizes enzyme to degrade gelatinized starch molecules, then processes a sample at low temperature, leads the branches of amylose molecules and amylopectin molecules to tend to be arranged in parallel due to the slow molecular motion at low temperature, and approach each other, and the amylose molecules and the amylopectin molecules are recombined through hydrogen bonds to assemble mixed microcrystalline bundles for precipitation and separation. Waxy corn starch is used as a raw material, pullulanase is used for enzymolysis and debranching to prepare short amylose, and spherical or ellipsoidal nano particles with the particle size of 30-150nm are formed by self-assembly at 4 ℃. By optimizing parameters such as starch concentration, pullulanase dosage, recrystallization time and the like in the enzymolysis regeneration process, the grain size of the starch nanoparticles is reduced to about 60-120nm, and the yield is improved to 85%. Spherical starch nanoparticles of 30-40nm are prepared by self-assembly of short glucan chains at 50 ℃ and the Degree of Polymerization (DP) of the particles is about 12-30. The enzymolysis regeneration method has the advantages of high yield, no corrosion to equipment, environmental friendliness and the like, but needs low-temperature operation and has long preparation time.
The crystallinity of starch is one of the important physicochemical properties of starch. According to X-ray diffraction peaks, the starch crystal forms are mainly classified into A, B, C types; some starches are formed by amylose complexed with other materials and are in the V form. The crystallinity of the starch is in positive correlation with the enthalpy value and the hardness, and has critical influence on the application properties of the starch granules, such as mechanical property, thermal stability, digestibility and dispersibility. The starch nanoparticles prepared by different methods have different factors influencing the crystallinity. In the preparation of the starch nano-particles by a regeneration method, the crystallinity can be improved by reducing the temperature in the regeneration process. The crystallinity of starch nanoparticles prepared by the sedimentation method increases with the amylose content of the original starch. The drying process has an effect on the crystalline structure of the starch nanoparticles. In addition, the starch nanoparticles obtained by ethanol sedimentation are circularly treated at the temperature of 4 ℃ and 40 ℃, so that the crystallinity can be improved. In general, few reports exist on analysis of starch nanoparticle crystallization control, and a crystal formation mechanism for preparing starch nanoparticles by a nano-sedimentation method is rarely reported.
Through the above analysis, the problems and defects of the prior art are as follows: (1) the starch nanoparticles prepared by the hydrolysis method are controlled in reaction efficiency, product yield and product appearance. (2) The mechanical method for preparing the starch nanoparticles has higher equipment requirement, large power consumption, long processing time, irregular particle shape and wide size distribution, and is limited in industry to a certain extent. (3) The nano-sedimentation method regulates and controls the size and the shape of particles by adding surfactants with different proportions, and has lower yield. (4) The enzymolysis recovery method needs low-temperature operation and has longer preparation time. The difficulty in solving the above problems and defects is: in the process of preparing the starch nanoparticles by the nano-sedimentation method, the nano-sedimentation and the drying are two different processes, and both processes can influence the crystallinity of the starch particles, and how to obtain the influence mechanism of various factors of the two processes on the crystallinity of the starch particles is a difficult point which cannot be overcome by the prior art.
The significance of solving the problems and the defects is as follows: the method has practical significance for deeply knowing the crystal formation mechanism and the control rule of the particles in the process of preparing the starch nanoparticles by the sedimentation method, and guiding the preparation of the starch nanoparticles with controllable crystallinity, controllable structural rigidity and good thermal stability.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a starch nanoparticle with controllable crystallinity, a preparation method and application thereof.
The invention is realized in such a way that a preparation method of starch nanoparticles with controllable crystallinity comprises the following steps:
the nano-sedimentation process and the drying process are separated, and the influence of test factors on the internal and surface morphology structures of the particles, the interaction of key groups, the composition and content of a solvent, the transfer rate of the solvent and the crystallinity of the particles in the nano-sedimentation process and the drying process is respectively measured, so that an influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles and an influence mechanism of the drying process on the crystallinity of the starch nanoparticles in the formation and control of the crystallization of the starch nanoparticles are obtained.
Further, in the nano-sedimentation process, the change of the solvent and non-solvent-containing starch prepolymer in the mutual replacement rate and crystallinity of the solvent and the non-solvent two-phase solvent is analyzed by changing the action level of the influencing factors; and (3) sorting and analyzing related data and results, and analyzing the correlation and influence rule of influence factors, solvent replacement and crystallinity to obtain an influence mechanism of the nano-sedimentation process on the crystallinity of the starch granules.
Furthermore, in the drying process, the flow, the temperature and the relative humidity of the drying air are taken as drying influence factors, the changes of the starch particles in the aspects of the solvent separation rate and the particle crystallinity are analyzed by changing the action level of the influence factors, the relevant data and results are collated and analyzed, and the influence mechanism of the drying process on the starch nanoparticle crystallinity is obtained by analyzing the influence factors, the solvent separation and the correlation and the influence rule of the crystallinity.
Furthermore, the prepared series of starch nanoparticles with controllable crystallinity are characterized and analyzed in terms of structural characteristics, scale, morphology, crystal structure, mechanical properties, film forming properties and adsorption properties.
Further, the preparation method of the starch nanoparticles with controllable crystallinity further comprises the following steps:
pretreating a cassava starch raw material, namely pretreating a cassava starch solution by adopting a mode of ultrasonic treatment, pullulanase enzymolysis treatment and ultrasonic/enzymolysis combined treatment;
step two, primary screening of factors influencing particle crystallinity in the nanometer sedimentation process;
thirdly, acquiring an influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles by establishing a solvent replacement kinetic and crystallization generation kinetic model of the sedimentation process;
step four, acquiring an influence mechanism of the drying process on the crystallinity of the starch nanoparticles by establishing a solvent release kinetics and a crystallization growth kinetics model of the drying process;
and fifthly, analyzing the structure and the performance of the crystallinity-controllable starch nanoparticles.
Further, in the first step, the molecular weight and the amylose content of the starch are used as control indexes, and the pretreatment method for preparing the starch with the molecular weight and the amylose content indexes meeting the requirements is obtained by analyzing and optimizing the starch solution concentration, the pH, the treatment temperature, the treatment time, the enzyme dosage or the ultrasonic power condition;
in the second step, various factors influencing the crystallinity of the starch granules comprise:
(1) raw material property factors: starch molecular weight, amylose content;
(2) starch solution factors: concentration, pH, ionic strength of the starch solution, addition of crystallization-inducing template molecules, addition of surface active ingredients;
(3) non-solvent factors: polarity, concentration of non-solvent, added surface active ingredient;
(4) the operation factors are as follows: settling temperature, ultrasonic power and time, dropping flow rate, and volume ratio of starch solution to non-solvent. And respectively analyzing the influence of the various factors on the crystallinity of the starch particles in the nano-sedimentation process by adopting a single-factor analysis method and taking the crystallinity of the particles as an analysis index.
Further, the method for obtaining the influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles in the third step comprises the following steps:
after primary screening of factors affecting particle crystallinity in the second nanometer sedimentation process, selecting test factors with obvious influence, and analyzing changes of the starch prepolymer in the particle interior and two-phase interface morphology structure, the solvent composition and content in the prepolymer, the mutual replacement rate of two-phase solvents, sugar chain arrangement and hydrogen bond association and crystallinity by changing the action level of the influence factors: analyzing and sorting related data and results, establishing a solvent replacement dynamics and crystallization generation dynamics model of the sedimentation process, analyzing the correlation and influence law of influence factors, solvent replacement and crystallinity, and obtaining an influence mechanism of the nano sedimentation process on the crystallinity of the starch particles;
the method for obtaining the influence mechanism of the drying process on the crystallinity of the starch nanoparticles comprises the following steps:
the flow, temperature and relative humidity of the drying air are used as drying influence factors, and the changes of the starch granules in the granule, the surface appearance structure, the solvent composition and content, the solvent separation rate, the sugar chain arrangement and hydrogen bond association and the granule crystallinity caused by the change of the action level of the influence factors are analyzed; analyzing and sorting related data and results, establishing a solvent release kinetics and crystallization growth kinetics model of the drying process, and analyzing influence factors, solvent release and crystallization correlation and influence rules to obtain an influence mechanism of the drying process on the crystallization of the starch nanoparticles;
in the fifth step, the method for analyzing the structure and the performance of the crystallinity-controllable starch nanoparticles comprises the following steps:
the morphology, particle size and particle size distribution, functional groups, crystalline structure, particle surface charge and zeta potential of the nanoparticle products with different crystallinities, as well as the thermodynamic properties, mechanical properties, flowability, resistance to digestion, stability, emulsifiability, swelling properties of the nanoparticles were systematically analyzed.
Another object of the present invention is to provide a starch nanoparticle prepared by the method for preparing a starch nanoparticle with controllable crystallinity.
The invention also aims to provide a wastewater treatment adsorbent prepared by using the starch nanoparticles, a coating adhesive and an emulsion stabilizer in papermaking.
The invention also aims to provide a bioactive substance carrier in the field of biomedicine prepared by using the starch nanoparticles, a reinforced polymer matrix filler in the field of novel materials, a thermoplastic starch film for reducing the water vapor permeability and the water absorption rate of the film, and a nano starch/cellulose nanocrystalline composite film in the field of edible packaging.
Another object of the present invention is to provide a drying operation apparatus for performing a drying process in the manufacturing method.
Compared with the prior art, the invention has the following beneficial effects: by combining all the technical schemes, the invention has the advantages and positive effects that: in the process of preparing the starch nanoparticles by the nano-sedimentation method, the nano-sedimentation and the drying are two different processes which both affect the crystallinity of the starch particles, and the influence of various factors of the two processes on the crystallinity of the starch particles is respectively reduced. In the process of nano-sedimentation, the change of starch prepolymer (containing a certain amount of solvent and non-solvent) in the mutual replacement rate of two-phase solvents, crystallinity and the like is analyzed by changing the action level of influencing factors. And (3) sorting and analyzing related data and results, and analyzing the correlation and influence rule of influence factors, solvent replacement and crystallinity to obtain the influence mechanism of the nano-sedimentation process on the crystallinity of the starch granules. During the drying process, the flow rate, temperature and relative humidity of the drying air are taken as main drying influence factors, and the influence factors are analyzed to cause the change of the starch granules in the aspects of solvent separation rate, granule crystallinity and the like by changing the action level of the influence factors. And (3) sorting and analyzing related data and results, and analyzing the correlation and influence rule of 'influencing factors-solvent separation-crystallinity', so as to obtain the influence mechanism of the drying process on the crystallinity of the starch nanoparticles. By controlling and controlling the crystallization forming mechanism in the process of preparing the starch nanoparticles by a nano sedimentation method, a theoretical basis is provided for the development of a new process for preparing the starch nanoparticles with controllable crystallinity, controllable structural rigidity and good thermal stability; and provides an important idea for the development of nano preparation technology of other bio-based polymers. In addition, the invention prepares the series starch nanoparticles with controllable crystallinity, characterizes and analyzes the structural characteristics and the main performance characteristics (including scale, morphology, crystal structure, mechanical property, film forming property, adsorption property and the like), and provides reference for expanding the application of the starch nanoparticles.
According to the invention, through analyzing the interrelation of 'influencing factor-solvent replacement-crystallinity' in the sedimentation process and the interrelation of 'influencing factor-solvent detachment-crystallinity' in the drying process, the regularity that sugar chains of starch are mutually matched and rearranged on spatial conformation and hydrogen bonds between the sugar chains and water molecules are re-associated is measured in the preparation process of the starch nanoparticles, and scientific understanding on the formation mechanism and control of the crystal is obtained. Providing a theoretical basis for developing a new process for preparing starch nanoparticles with controllable crystallinity and good performance; and provides a thought for the development of the nano preparation technology of other bio-based polymers.
The crystallinity of the starch is one of important physicochemical characteristics of the starch, and has influence on the mechanical properties, thermal stability, digestibility, dispersibility and the like of the starch granules. However, the determination of the crystallization formation mechanism in the process of preparing starch nanoparticles by a sedimentation method is only reported in the literature. The method aims at the determination of a crystallization formation mechanism in the process of preparing the starch nanoparticles by a nano sedimentation method, and has theoretical and application significance and innovation. The method separates the nanometer sedimentation process and the drying process of the preparation of the starch nanoparticles, respectively measures the influence of test factors on the internal and surface morphology structures of the particles, the interaction of key groups, the composition and content of a solvent, the transfer rate of the solvent, the crystallinity of the particles and the like in the two processes, and further analyzes the crystallization formation mechanism of the starch nanoparticles.
Drawings
Fig. 1 is a flow chart of a method for preparing starch nanoparticles with controllable crystallinity according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of an experimental apparatus for drying starch nanoparticles according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a crystallization mechanism and control in a process of preparing starch nanoparticles by a nano-sedimentation method according to an embodiment of the present invention.
FIG. 4 is a graph showing the influence of pretreatment methods such as wet-heat treatment, ultrasonic treatment, microwave treatment, gelatinization and alkali treatment on the structure and reaction performance of tapioca starch.
FIG. 5 is a graph showing the effect of pretreatment on DS value of esterification reaction of tapioca starch according to an embodiment of the present invention.
FIG. 6 is a schematic diagram of a reactor for a laboratory for enzymatic synthesis of starch esters according to an embodiment of the present invention.
FIG. 7 is a response surface optimized synthesis diagram of starch abietate provided by the embodiment of the invention.
Fig. 8 is an SEM image of starch nanoparticles provided by an embodiment of the present invention.
FIG. 9 is an XRD pattern of native starch and starch nanoparticles provided by an embodiment of the present invention.
Fig. 10 is a photomicrograph (1000 x) of a starch nanoparticle stabilized Pickering emulsion provided by an example of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Aiming at the problems in the prior art, the invention provides starch nanoparticles with controllable crystallinity, a preparation method and application thereof, and the invention is described in detail with reference to the accompanying drawings.
As shown in fig. 1, a preparation method of starch nanoparticles with controllable crystallinity provided by the embodiment of the invention includes the following steps:
s101, pretreating a cassava starch raw material, namely pretreating a cassava starch solution by adopting a mode of ultrasonic treatment, pullulanase enzymolysis treatment and ultrasonic/enzymolysis combined treatment.
And S102, primary screening of factors influencing particle crystallinity in the nanometer sedimentation process.
S103, obtaining an influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles by establishing a solvent replacement kinetic and crystallization generation kinetic model of the sedimentation process.
S104, obtaining an influence mechanism of the drying process on the crystallinity of the starch nanoparticles by establishing a solvent separation kinetics and a crystallization growth kinetics model of the drying process.
And S105, carrying out structure and performance analysis on the crystallinity-controllable starch nanoparticles.
And step S101, taking the molecular weight and the amylose content of the starch as control indexes, and analyzing and optimizing the concentration, pH, treatment temperature, treatment time, enzyme dosage or ultrasonic power conditions of the starch solution to obtain the pretreatment method with the prepared molecular weight and amylose content indexes meeting the requirements.
In step S102, various factors affecting the crystallinity of the starch granule include:
(1) raw material property factors: starch molecular weight, amylose content.
(2) Starch solution factors: concentration, pH, ionic strength of the starch solution, addition of crystallization-inducing template molecules, addition of surface-active ingredients.
(3) Non-solvent factors: polarity of non-solvent, concentration, addition of surface active ingredients.
(4) The operation factors are as follows: settling temperature, ultrasonic power and time, dropping flow rate, and volume ratio of starch solution to non-solvent. And respectively analyzing the influence of the various factors on the crystallinity of the starch particles in the nano-sedimentation process by adopting a single-factor analysis method and taking the crystallinity of the particles as an analysis index.
The method for obtaining the influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles in the step S103 comprises the following steps: after primary screening of factors affecting particle crystallinity in the step S102 nanometer sedimentation process, selecting test factors with obvious influence, and analyzing changes of the starch prepolymer in the particle interior and two-phase interface morphology structure, the prepolymer in-vivo solvent composition and content, the two-phase solvent mutual replacement rate, the sugar chain arrangement and hydrogen bond association and the crystallinity by changing the action level of the influence factors: analyzing and sorting related data and results, establishing a solvent replacement dynamics and crystallization generation dynamics model of the sedimentation process, analyzing the correlation and influence law of influence factors, solvent replacement and crystallinity, and obtaining an influence mechanism of the nano sedimentation process on the crystallinity of the starch particles;
the step S104 of obtaining the influence mechanism of the drying process on the crystallinity of the starch nanoparticles includes:
the flow, temperature and relative humidity of the drying air are used as drying influence factors, and the changes of the starch granules in the granule, the surface appearance structure, the solvent composition and content, the solvent separation rate, the sugar chain arrangement and hydrogen bond association and the granule crystallinity caused by the change of the action level of the influence factors are analyzed; and analyzing and sorting the related data and results, establishing a solvent release kinetics and crystallization growth kinetics model of the drying process, and analyzing the influence factors, the solvent release and the crystallinity correlation and influence rules to obtain an influence mechanism of the drying process on the crystallinity of the starch nanoparticles.
In the step S105, the method for analyzing the structure and the performance of the crystallinity-controllable starch nanoparticle includes:
the morphology, particle size and particle size distribution, functional groups, crystalline structure, particle surface charge and zeta potential of the nanoparticle products with different crystallinities, as well as the thermodynamic properties, mechanical properties, flowability, resistance to digestion, stability, emulsifiability, swelling properties of the nanoparticles were systematically analyzed.
The technical solution of the present invention is further described below with reference to experiments.
1. Method of producing a composite material
1.1 specific example 1, pretreatment of tapioca starch raw material
The invention takes the molecular weight of starch and the content of amylose in the treatment fluid as main analysis indexes. The pretreatment method comprises the steps of pretreating a cassava starch solution by adopting a mode of ultrasonic treatment, pullulanase enzymolysis treatment and ultrasonic/enzymolysis combined treatment, and analyzing and optimizing conditions such as starch solution concentration, pH, treatment temperature, treatment time, enzyme dosage or ultrasonic power in the pretreatment process to efficiently prepare the pretreatment method with the indexes of molecular weight and amylose content meeting the requirements.
1.1.1 molecular weight of starch
Dextran standards of different molecular weights were dissolved in 90% DMSO and the retention times corresponding to the molecular weights of each standard were analyzed using High Performance Liquid Chromatography (HPLC) to plot a standard curve. And (3) carrying out sample injection analysis on the starch sample under the same chromatographic condition, detecting the molecular weight distribution diagram and the molecular weight of the sample, and calculating the polymerization degree of the starch molecules.
HPLC conditions: agilent Polaris 5NH2Column (4.6mm x250 mm, 5 μm) with acetonitrile/water 78:22 (volume ratio), flow rate 1.0mL/min, column temperature 35 ℃.
1.1.2 amylose content
Spectrophotometry (UV-Vis): preparing standard solution of amylose and amylopectin with concentration of 0.0235mg/mL, preparing standard mixed solution of amylose and amylopectin according to proportion, adding iodine solution, and measuring light absorption value at 600 nm. Drawing a calibration curve by taking the content of amylose in the mixed solution as a horizontal coordinate and the absorbance as a vertical coordinate, and solving a linear regression equation; and detecting the light absorption value of the starch sample by the same method, and calculating the amylose content.
1.2 example 2 Primary Screen influencing the conditions of crystallinity of starch granules
The particle crystallinity is taken as a main analysis index, the molecular weight and the amylose content of the starch raw material not only influence the viscosity, the fluidity and the dispersibility of starch liquid, but also influence the orderly arrangement of sugar chains in starch molecules and the regeneration of hydrogen bond association in a sedimentation process, so the molecular weight and the amylose content of the starch also influence the efficiency of a starch nanoparticle preparation process, the particle size and the particle size distribution are wide and narrow, and the crystallinity influence factors of the particles are subjected to systematic analysis and screening, and the test factors with obvious influence are selected for the subsequent mechanism determination. In order to fix the crystallization state of the starch granules obtained in the sedimentation process, all granule samples obtained by sedimentation are quickly frozen by using liquid nitrogen, dried by adopting a freeze-drying method which has small influence on the granule crystallinity, and then subjected to crystallinity analysis.
And (3) starch crystallinity: XRD analysis, XRD analysis using MiniFlex600 model X-ray diffractometer, japan: cu (ka) rays, Ni plate filtering, voltage of 40kV, current of 15mA, scanning range of 4-30 degrees in terms of 2 theta, scanning speed of 8 degrees/min and scanning step length of 0.02 degrees, and analyzing the crystal form of a starch sample and calculating the crystallinity according to the vibration wave number of diffraction peaks and the area of scattering peaks.
1.3 example 3 mechanism of influence of sedimentation on crystallinity of starch nanoparticles
In the experimental process, after the action level of a certain influence factor is set, a proper volume of starch liquid is dripped into a certain volume of non-solvent, and the formed starch prepolymer is sampled at regular time. On one hand, the residual solvent (including water and non-solvent) of the starch prepolymer is quickly extracted, and the composition and the content of the solvent in the starch prepolymer are analyzed by using a Gas Chromatography (GC); calculating the mutual replacement rate of the two-phase solvents according to the sampling time interval by taking the dry weight of the starch in the sample as a reference; the change of hydrogen bond association in the starch prepolymer is obtained by a Raman spectroscopy (Raman) method. On the other hand, the starch prepolymer is rapidly frozen by using liquid nitrogen, the surface morphology structure and the arrangement state of sugar chains in the starch prepolymer are fixed, then freeze-drying treatment is carried out, and the morphology structures in the particles and the two-phase interface are analyzed by using a microscopic characterization technology; the crystallinity of the particles was analyzed by XRD; analyzing the sugar chain arrangement state of the starch on the basis of XRD analysis; the changes in hydrogen bond association in the starch prepolymer were analyzed using fourier transform infrared spectroscopy (FTIR) characterization technique.
1.3.1 morphological Structure of starch
The structure of the two-phase contact interface was analyzed using a SUPRA 55Sapphire field emission Scanning Electron Microscope (SEM), a Digital Instrument DI 3000 Atomic Force Microscope (AFM), Inc. of Calitz, Germany. And analyzing the structure of the two-phase contact interface and the structural change of the interior of the starch prepolymer by using a laser confocal microscope (CLSM).
1.3.2 composition, content and rate of Displacement of the solvent
And extracting residual solvent of the starch prepolymer by using butanone-sec-butyl alcohol mixed solution, performing GC analysis, and calculating the composition, content and replacement rate of the solvent by taking the dry weight of the starch contained in the sample as a reference. GC conditions were as follows: the GDX-104 stationary phase packed column, TCD detector, vaporization temperature 175 deg.C, and column temperature 145 deg.C.
1.3.3 crystallinity of starch
And (4) XRD analysis. XRD analysis was performed using a MiniFlex model 600X-ray diffractometer from japan: cu (ka) rays, Ni plate filtering, voltage of 40kV, current of 15mA, scanning range of 4-30 degrees in terms of 2 theta, scanning speed of 8 degrees/min and scanning step length of 0.02 degrees, and analyzing the crystal form of a starch sample and calculating the crystallinity according to the vibration wave number of diffraction peaks and the area of scattering peaks.
1.3.4 sugar chain arrangement State of starch
Calculating the interplanar spacing (d) from the data relating to the diffraction angle (theta) on the basis of XRD analysis; according to the crystal system type of the starch sample, selecting a relational expression of the interplanar spacing (d) and the lattice parameter, calculating the Miller index, analyzing the state of a crystal plane, and analyzing the sugar chain arrangement of the starch.
1.3.5 states of Hydrogen bond Association in starch
FTIR and Raman methods are adopted to analyze the frequency spectrum displacement and intensity change of characteristic groups such as methylene, hydroxyl and the like in the starch prepolymer and the change of hydrogen bond association in the starch prepolymer.
FTIR analysis: scanning resolution was 4cm using a model MAGNA-1R550 Fourier transform infrared spectrometer manufactured by Saimer Feishell science, USA-1The number of scanning times is 32, and the wave number range is 400-4000cm-1。
Raman analysis: the InVia-Reflex laser confocal Raman spectrometer of the Renysha company of England is used, the laser power is 5mW,Wavelength of 532nm and wave number range of 200-4000cm-1Scanning times 10 and exposure time 10 s.
1.4 example 4 mechanism of influence of drying on crystallinity of starch nanoparticles
In order to make the drying action uniformly act on all directions of the starch granules, the invention adopts a fluidized drying mode, uses a small column to fill the starch granules obtained in a proper amount of sedimentation process, and carries out ventilation drying treatment. The experimental set-up for the drying operation is schematically shown in FIG. 2.
In the experimental process, the action level of a certain influence factor is set, the starch granules obtained in the nanometer sedimentation process are treated, and the sampling is carried out at regular time. On one hand, the residual solvent (including water and non-solvent) in the sample is extracted rapidly, and the composition and content of the solvent in the sample are analyzed by GC; and the rate of solvent release was calculated. On the other hand, the samples were snap frozen and lyophilized. Then, the morphological structures on the surface and in the nano-particles are analyzed by using a microscopic characterization technology, the crystallinity of the particles is analyzed by XRD, the arrangement state of sugar chains of the starch is analyzed, and the hydrogen bond association state in the starch is analyzed by FTIR.
1.4.1 topographical structure of starch nanoparticles
The structure of the two-phase contact interface was analyzed by a field emission Scanning Electron Microscope (SEM) of SUPRA 55Sapphire, Calitz, Germany, and an Atomic Force Microscope (AFM) of DI Dimension 3000, Digital Instrument, USA, of the present college. And analyzing the structure of the two-phase contact interface and the structural change of the interior of the starch prepolymer by using a laser confocal microscope (CLSM).
1.4.2 composition, content and Release Rate of the solvent
And extracting residual solvent of the starch prepolymer by using butanone-sec-butyl alcohol mixed solution, performing GC analysis, and calculating the composition, content and replacement rate of the solvent by taking the dry weight of the starch contained in the sample as a reference. GC conditions were as follows: the GDX-104 stationary phase packed column, TCD detector, vaporization temperature 175 deg.C, and column temperature 145 deg.C.
1.4.3 starch crystallinity
And (4) XRD analysis. XRD analysis was performed using a MiniFlex model 600X-ray diffractometer from japan: cu (ka) rays, Ni plate filtering, voltage of 40kV, current of 15mA, scanning range of 4-30 degrees in terms of 2 theta, scanning speed of 8 degrees/min and scanning step length of 0.02 degrees, and analyzing the crystal form of a starch sample and calculating the crystallinity according to the vibration wave number of diffraction peaks and the area of scattering peaks.
1.4.4 sugar chain arrangement State of starch nanoparticles
Calculating the interplanar spacing (d) from the data relating to the diffraction angle (theta) on the basis of XRD analysis; according to the crystal system type of the starch sample, selecting a relational expression of the interplanar spacing (d) and the lattice parameter, calculating the Miller index, analyzing the state of a crystal plane, and analyzing the sugar chain arrangement of the starch.
1.4.5 State of Hydrogen bond Association in starch nanoparticles
FTIR and Raman methods are adopted to analyze the frequency spectrum displacement and the intensity change of characteristic groups such as methylene, hydroxyl and the like in the starch prepolymer and study the change of hydrogen bond association in the starch prepolymer.
And analyzing the frequency spectrum displacement and the intensity change of characteristic groups such as methylene, hydroxyl and the like in the starch prepolymer by adopting an FTIR method to obtain the change of hydrogen bond association in the starch prepolymer. FTIR analysis: scanning resolution was 4cm using a model MAGNA-1R550 Fourier transform infrared spectrometer manufactured by Saimer Feishell science, USA-1The number of scanning times is 32, and the wave number range is 400-4000cm-1。
1.5 example 5 Structure and Properties of crystallinity-controlled starch nanoparticles
The method is characterized in that a powder comprehensive characteristic tester, an XRD (X-ray diffraction), an SEM (scanning Electron microscope), an FTIR (Fourier transform infrared spectrometer) and other instruments and chemical analysis methods are adopted to carry out systematic analysis on the morphology, granularity distribution, functional groups, crystal structures, particle surface charges, zeta potentials, thermodynamic properties, mechanical properties, flowability, digestibility, stability, emulsibility, swelling properties and the like of nano particles with different crystallinities, so that the structural characteristics and the main properties of series of starch nano particles with controllable crystallinities are deeply known, and a reference is provided for expanding the application of the series of starch nano particles.
SEM, XRD, FTIR, etc.; the zeta potential, the particle size and the particle size distribution rule of the series of nano-starch are measured by a ZEN3690 Malvern laser particle size analyzer, Shanghai Cibacco Ji instruments and systems Limited. The thermodynamic property, mechanical property, anti-digestion property, stability, emulsifying property, swelling property and the like of the nano starch particles are analyzed by adopting a conventional mature method.
2 technical route
The technical route of the invention is shown in figure 3:
3 feasibility analysis
3.1 in the process of preparing the starch nanoparticles by the nano-sedimentation method, the nano-sedimentation and the drying are two different processes which can influence the crystallinity of the starch particles, and the invention is reasonable in methodology by respectively obtaining the influence of various factors in the two processes on the crystallinity of the starch particles and then integrating the crystal formation mechanism and the control of the process of preparing the starch nanoparticles by the nano-sedimentation method.
The dissolved starch molecules form crystals again, and the essence is that sugar chains in the starch molecules and sugar chains as well as the sugar chains and water molecules are matched and rearranged in space conformation, so that an ordered stable state of system balance is achieved. On one hand, in the process of nano-sedimentation, when a solution phase with starch with certain concentration is added into a non-solvent, a contact interface of a water phase and the non-solvent is formed, the water and the non-solvent are mutually replaced, and the replacement rate and the shape structure of the two-phase interface have mutual influence; the change of the mutual replacement rate of the solvent can cause the change of the composition and the content of the solvent (containing a certain amount of water and non-solvent) in the starch prepolymer sample, and further influence the interaction between sugar chains in the starch sample and the hydroxyl between the sugar chains and water molecules, thereby influencing the formation of crystals. The invention obtains the influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles by analyzing the correlation of the influence factors, the solvent replacement and the crystallinity, and is correct in theory. On the other hand, in the drying process, drying influence factors influence the volatilization rates of residual solvents among starch granules and in the granules (the volatilization rates of water and a non-solvent are different), so that the composition and the content of the residual solvents among the starch granules and in the granules are changed; the release rate of the solvent also has an influence on the morphological structure of the surface of the starch granule, and causes the change of the composition and the content of the residual solvent in the starch granule, thereby influencing the interaction between sugar chains on starch molecules and the hydroxyl between the sugar chains and water molecules, and further influencing the formation of crystals. By analyzing the correlation of 'influencing factors-solvent separation-crystallinity', the influence mechanism of the drying process on the crystallinity of the starch nanoparticles is correct.
3.2 the invention separates the nano-sedimentation process and the drying process of preparing the starch nano-particles by the nano-sedimentation method, and is to avoid the influence of the drying process on the crystallization of the starch particles from interfering the analysis of the crystallization forming mechanism in the nano-sedimentation process. For this purpose, two measures are taken. Firstly, the advantages of Raman spectrum suitable for testing a solution system are utilized, and the characterization analysis of the starch prepolymer is directly carried out without drying. Secondly, in order to fix the crystalline state of the starch prepolymer rapidly and to remove the solvent while maintaining this state. The method adopts liquid nitrogen to freeze rapidly, fixes the morphology structure and the crystallization state, then adopts a freeze-drying method with small influence on the particle structure and the crystallization to carry out drying treatment, and then carries out FTIR and XRD analysis. Through the data of Raman, FTIR and XRD of comprehensive and analytical comparison, the change rule of sugar chain arrangement and hydrogen bond association in the starch prepolymer in the sedimentation process can be comprehensively known.
The analysis methods such as GC, XRD, SEM, FTIR and the like adopted by the invention are mature and reliable.
The present invention will be further described with reference to specific experiments and effects.
The invention has widely analyzed the modification of the cassava starch, and has good results in the aspects of pretreatment of starch raw materials, enzymatic esterification of the cassava starch, controllable decrystallization of starch granules, preparation of starch nanoparticles by a sedimentation method and the like.
1. Pretreatment of tapioca starch
The invention contrasts and analyzes the influence of pretreatment methods such as a wet-heat method, ultrasonic waves, microwaves, gelatinization and alkali treatment on the structure and the reaction performance of the cassava starch. After the alkaline pretreatment, the cassava starch particles change the original shape, the surfaces have broken surfaces and cracks, the crystallization performance of starch crystals is reduced (see figure 4, wherein (a) raw cassava starch, (b) wet heat treatment starch, (c) ultrasonic treatment starch, (d) microwave treatment starch, (e) gelatinization treatment starch, and (f) alkaline treatment starch SEM images), the solubility in cold water is improved, and the transparency and the viscosity are enhanced. The degree of substitution of the activated cassava starch in reaction with abietic acid is remarkably improved, and the degree of substitution can reach 0.088 (see the influence of pretreatment on the DS value of the cassava starch esterification reaction in figure 5).
2. Enzymatic synthesis of esterified starch
The invention designs a fixed bed reactor (shown in figure 6) for synthesizing the starch abietate, and researches on a technical method and reaction kinetics for enzymatically synthesizing the starch abietate are carried out. The results show that: the synthesis reaction of the starch abietate ester is an apparent first-order reaction, the apparent activation energy is 30802J/mol, the apparent activation energy of the ester hydrolysis reaction is 1006J/mol, and the total reaction kinetic equation for enzymatically preparing the starch abietate ester is r ═ k. CA. CAGU. Three factors of reaction temperature, time and enzyme-material ratio in the esterification process and interaction thereof are optimized by applying a response surface analysis method (see figure 7), and optimized reaction conditions are obtained: the reaction time is 4.11h, the reaction temperature is 48.18 ℃, the enzyme dosage is 15.47 percent, and the product substitution degree reaches 0.106.
The invention relates to the analysis of enzymatic synthesis of esterified starch, and provides reference for the design of experimental devices used in the sedimentation process and the drying process of preparing starch nanoparticles by the sedimentation method; various characterization and analysis technical methods for starch can be applied to the invention.
1.3 controlled decrystallization of starch granules
The method takes the cassava starch as a raw material, and systematically analyzes the influence of the conditions such as alkali concentration, treatment temperature, time, material-liquid ratio and the like on the crystallinity and the crystal structure of the cassava starch in the high-temperature alcohol-alkali method treatment process. The results show that the influence of the alkali concentration and the treatment temperature on the crystallinity in the starch decrystallization process is linear negative correlation (the r value of the alkali concentration and the crystallinity is-0.97, and the r value of the treatment temperature and the crystallinity is-0.84), and the crystal form of the tapioca starch can be effectively controlled to be changed from the A type to the amorphous state and the crystallinity is gradually reduced from 23.63% to 0.00% by controlling the alkali concentration (see table 1).
TABLE 1 relative crystallinity of cassava starch samples treated with different alkali concentrations
Figure BDA0002755584560000191
The target directions of the controlled decrystallization analysis of the starch granules and the analysis of the crystallization forming mechanism of the starch nanoparticle preparation process are just opposite, but all the related are ordered stable states and influencing factors, wherein the ordered stable states are matched with each other in the space conformation between sugar chains in the starch granules and between the sugar chains and water molecules.
1.4 preparation of starch nanoparticles by sedimentation
In order to expand the application of the cassava starch, the project group develops the research of preparing the cassava starch nanoparticles by the aid of ultrasonic waves. The size and the polydispersity of the nano-particles are taken as target indexes, the preparation conditions are optimized, and the prepared cassava starch nano-particles are spherical, have good appearance and uniform size distribution (see figure 8). The crystal form of the particles is changed from the A form to the amorphous form, and the relative crystallinity is obviously reduced (see figure 9). The starch nanoparticles can be used as a particle emulsifier, and an O/W emulsion with good stability can be prepared, wherein the volume average particle diameter of emulsion droplets is less than 50 mu m (see figure 10).
According to the invention, the preparation conditions are optimized, the concentration of the raw material starch milk is improved to 5%, and the preparation efficiency, the distribution of the starch nanoparticle particle size and the control of the morphology are improved.
The method is mainly based on the development of a provincial key laboratory of the university of Guangxi nationality, namely Guangxi polysaccharide material and modification key laboratory, and carries out a great deal of analysis work around the preparation and application of the polysaccharide material, so that a series of effects are achieved in the aspects of regulation and control of the process of synthesizing glucan by cane sugar, glucan modification, activation and modification of cassava starch particles, separation, purification and modification of bagasse cellulose, application of the polysaccharide material to the preparation of inorganic nano composite materials, membrane separation process and the like.
Basically establishes the separation and purification of polysaccharide, the chemical structure test and partial high-grade structure test of polysaccharide and the polysaccharide saccharification based on membrane separationThe system comprises platforms such as chemistry or biology modification and application, software and hardware based on theoretical calculation and molecular simulation, and corresponding instrument equipment. Has a thickness of about 2000m2The special laboratory and related supporting facilities form a set of relatively perfect management and operation system. The laboratory has analytical instruments for analytical testing according to the invention. Such as MiniFlex 600X-ray diffractometer, DSC-500B differential scanning calorimeter, SUPRA 55Sapphire field emission scanning electron microscope, SHIMADMDZU LC-20 high performance liquid chromatograph, SCANNER-2 thin layer SCANNER, MAGNA-1R550 Fourier transform infrared spectrometer, UV-2450SE ultraviolet spectrophotometer, powder comprehensive characteristic tester, etc. The pharmaceutical equipment comprises a tabletting machine, a disintegration time limit instrument, a drug dissolution instrument, a hardness tester, a viscometer and the like. Most of instruments and equipment required by the support party are owned by the laboratory, and some instruments and equipment which are not owned by the laboratory can be provided by the analysis and test center in Guangxi province.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A method for preparing starch nanoparticles with controllable crystallinity is characterized by comprising the following steps: the nano-sedimentation process and the drying process are separated, and the influence of test factors on the internal and surface morphology structures of the particles, the interaction of key groups, the composition and content of a solvent, the transfer rate of the solvent and the crystallinity of the particles in the nano-sedimentation process and the drying process is respectively measured, so that an influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles and an influence mechanism of the drying process on the crystallinity of the starch nanoparticles in the formation and control of the crystallization of the starch nanoparticles are obtained.
2. The method for preparing starch nanoparticles with controllable crystallinity according to claim 1, wherein the changes in the rate of mutual replacement of solvent and non-solvent two-phase solvent and the crystallinity of the solvent-and non-solvent-containing starch prepolymers during the nano-settling process are analyzed by changing the action level of the influencing factors; and (3) sorting and analyzing related data and results, and analyzing the correlation and influence rule of influence factors, solvent replacement and crystallinity to obtain an influence mechanism of the nano-sedimentation process on the crystallinity of the starch granules.
3. The method for preparing starch nanoparticles with controllable crystallinity according to claim 1, wherein in the drying process, the flow rate, temperature and relative humidity of drying air are used as drying influence factors, the change of starch particles in the aspects of solvent release rate and particle crystallinity is analyzed by changing the action level of the influence factors, the related data and results are collated and analyzed, and the influence mechanism of the drying process on the crystallinity of the starch nanoparticles is obtained by analyzing the influence factors, the solvent release and the crystallinity and the influence rule.
4. The method for preparing starch nanoparticles with controllable crystallinity according to claim 1, wherein the prepared starch nanoparticles with controllable crystallinity are characterized and analyzed in terms of structural characteristics, dimension, morphology, crystal structure, mechanical properties, film forming properties and adsorption properties.
5. The method of preparing crystallinity-controllable starch nanoparticles according to claim 1, further comprising:
pretreating a cassava starch raw material, namely pretreating a cassava starch solution by adopting a mode of ultrasonic treatment, pullulanase enzymolysis treatment and ultrasonic/enzymolysis combined treatment;
step two, primary screening of factors influencing particle crystallinity in the nanometer sedimentation process;
thirdly, acquiring an influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles by establishing a solvent replacement kinetic and crystallization generation kinetic model of the sedimentation process;
step four, acquiring an influence mechanism of the drying process on the crystallinity of the starch nanoparticles by establishing a solvent release kinetics and a crystallization growth kinetics model of the drying process;
and fifthly, analyzing the structure and the performance of the crystallinity-controllable starch nanoparticles.
6. The preparation method of the crystallinity-controllable starch nanoparticles as claimed in claim 5, wherein in the first step, the pretreatment method for preparing the starch nanoparticles with the indexes of molecular weight and amylose content meeting the requirements is obtained by analyzing and optimizing the starch solution concentration, pH, treatment temperature, treatment time, enzyme dosage or ultrasonic power conditions by taking the starch molecular weight and the amylose content as control indexes;
in the second step, various factors influencing the crystallinity of the starch granules comprise:
(1) raw material property factors: starch molecular weight, amylose content;
(2) starch solution factors: concentration, pH, ionic strength of the starch solution, addition of crystallization-inducing template molecules, addition of surface active ingredients;
(3) non-solvent factors: polarity, concentration of non-solvent, added surface active ingredient;
(4) the operation factors are as follows: settling temperature, ultrasonic power and time, dropping flow rate, and volume ratio of starch solution to non-solvent. And respectively analyzing the influence of the various factors on the crystallinity of the starch particles in the nano-sedimentation process by adopting a single-factor analysis method and taking the crystallinity of the particles as an analysis index.
7. The method for preparing the crystallinity-controllable starch nanoparticles according to claim 5, wherein the method for obtaining the influence mechanism of the sedimentation process on the crystallinity of the starch nanoparticles in the third step comprises the following steps: after primary screening of factors affecting particle crystallinity in the second nanometer sedimentation process, selecting test factors with obvious influence, and analyzing changes of the starch prepolymer in the particle interior and two-phase interface morphology structure, the solvent composition and content in the prepolymer, the mutual replacement rate of two-phase solvents, sugar chain arrangement and hydrogen bond association and crystallinity by changing the action level of the influence factors: analyzing and sorting related data and results, establishing a solvent replacement dynamics and crystallization generation dynamics model of the sedimentation process, analyzing the correlation and influence law of influence factors, solvent replacement and crystallinity, and obtaining an influence mechanism of the nano sedimentation process on the crystallinity of the starch particles;
the method for obtaining the influence mechanism of the drying process on the crystallinity of the starch nanoparticles comprises the following steps:
the flow, temperature and relative humidity of the drying air are used as drying influence factors, and the changes of the starch granules in the granule, the surface appearance structure, the solvent composition and content, the solvent separation rate, the sugar chain arrangement and hydrogen bond association and the granule crystallinity caused by the change of the action level of the influence factors are analyzed; analyzing and sorting related data and results, establishing a solvent release kinetics and crystallization growth kinetics model of the drying process, and analyzing influence factors, solvent release and crystallization correlation and influence rules to obtain an influence mechanism of the drying process on the crystallization of the starch nanoparticles;
in the fifth step, the method for analyzing the structure and the performance of the crystallinity-controllable starch nanoparticles comprises the following steps:
the morphology, particle size and particle size distribution, functional groups, crystalline structure, particle surface charge and zeta potential of the nanoparticle products with different crystallinities, as well as the thermodynamic properties, mechanical properties, flowability, resistance to digestion, stability, emulsifiability, swelling properties of the nanoparticles were systematically analyzed.
8. A starch nanoparticle prepared by the method for preparing a crystallinity-controllable starch nanoparticle according to any one of claims 1 to 7.
9. A wastewater treatment adsorbent prepared by using the starch nanoparticles as claimed in claim 8, a coating adhesive and an emulsion stabilizer in papermaking, a bioactive substance carrier in the field of biomedicine, a reinforced polymer matrix filler in the field of novel materials, a thermoplastic starch film for reducing the water vapor permeability and the water absorption of the film, and a nano starch/cellulose nanocrystalline composite film in the field of edible packaging.
10. A drying operation device for realizing the drying process in the preparation method of any one of claims 1 to 7.
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