Green Preparation Of Starch Nanoparticles And Its Application In Curcumin Encapsulation And Smart Labels

Curcumin is widely used as a food-grade indicator in smart labels due to p H-color responsiveness.But its low water solubility and poor compatibility significantly degrade the mechanical properties and responsiveness of smart labels.A green nano-encapsulation carriers provides a new way to solve the above problems.At present,the main solvents(alkaline solution,organic reagent and oil)of nanocarrier system for curcumin usually involve rapid degradation,organic solvents and limited amounts of surfactants and fats,which are not suitable for food applications.Therefore,this research proposed an eco-friendly method using NADES as the self-assembly medium,formed by natural components to prepare SNP.on this basis,curcumin-starch nanoparticles complex(CSNP)was synthesized by incorporating curcumin into the self-assembly system.Finally,the curcumin-SNP-DES self-assembly system(CSD)was added to the starch film to form a smart label with p H-color responsiveness.The performance of the smart label and its potential application in shrimp freshness monitoring were also investigated.The specific research content and results are as follows:1.A series of SNP with different shapes and sizes were prepared by using DES/water as the self-assembly environment of short-chain amylose.Under 0%,10%,20%,40%,80%,w/w LRDES,glucose and lactic acid induction alone,SNP with average particle sizes of 450.2 nm,406.7 nm,347.7 nm,229.7 nm,104.6 nm,335.8nm and 258.6 nm were prepared.The SNP changed from spherical to rice-like when the concentration of LRDES was increased to 20%.The SNP formed by self-assembly at low concentrations of LRDES(0%,10%,20%)were B+V type crystal structure.As the concentration continues to increase,the peak pattern became more diffuse and the relative crystallinity became lower.The initial gelatinization temperature(T_o)and gelatinization enthalpy(ΔH)of SNP decreased significantly with the increase of LRDES content.Compared with the control group,the initial thermal degradation temperature of SNP formed by LRDES self-assembly increased,but there was no significant difference in the maximum thermal degradation temperature.The effect of LRDES on SNP formation mechanism was explored by FTIR,chain length distribution and self-assembly behavior of SNP.The results showed that the nucleation and growth of starch molecules were delayed through hydrogen bond interaction between LRDES and short-chain amylose,and LRDES promoted the self-assembly of starch molecules with longer chains to form SNP.These results indicate that the self-assembly process of amylose can be effectively regulated by designing the type and concentration of NADES to synthesize SNP with different morphologies and sizes.2.The encapsulation of curcumin in SNP was realized by using choline chlorine-lactic acid deep eutectic solvent(CLDES)as the solvent of curcumin and the self-assembly medium of short-chain amylose.In different concentrations of CLDES(80%,100%,120%,140%w/v),the loading capacity of SNP for curcumin were 7.99 mg/g,7.52 mg/g,6.86 mg/g,6.52 mg/g,respectively.The encapsulation efficiency were56.18%,46.48%,37.30%,31.88%.The increase of CLDES concentration decreased the size and yield of SNP correspondingly,but had little effect on their shape.there were X-diffraction peaks at 15.0°,17.0°and 23.5°in CSNP,corresponding to A-type crystalline pattern.The increase of CLDES content leads to the gradual weakening of CSNP diffraction peak intensity.The results of FTIR,fluorescence spectroscopy and DSC showed that CSNP were non-inclusion complex formed by the interaction of hydrogen bond between curcumin and short-chain amylose.The physical barrier of SNP and the hydrogen bond interaction between curcumin and starch improve the thermal,p H and optical stability of curcumin.The interaction between the physical barrier of SNP and the hydrogen bond of curcumin-starch chain improves the thermal stability,p H stability and photostability of curcumin.These results indicated that CLDES could be used as a vector for SNP loading curcumin,thus improving the stability of curcumin.3.In order to realize the efficient utilization of CSNP,four curcumin-SNP-DES self-assembly systems(CSD-8,CSD-10,CSD-12,CSD-14)self-assembled in different concentrations of CLDES(80%,100%,120%,140%w/v)were directly used to synthesize starch-based curcumin composite smart labels,and curcumin hybrid smart labels as a control group.The tensile strength of hybrid smart labels(CF)and four kinds of composite smart labels(CSDF-8,CSDF-10,CSDF-12,CSDF-14)were 5.41 MPa,12.94 MPa,6.34 MPa,3.54 MPa and 2.13 MPa,respectively.The elongation at break were 58.50%,25.23%,35.87%,87.57%,53.19%,respectively.The results of type and fluorescence microscopy showed that the dispersibility and compatibility of curcumin in CSDF were higher than CF.As a result,CSDF showed a more uniform surface and cross section,lower L*,water contact angle and crystallinity,higher a*,b*,water-vapor permeability,UV barrier properties and sensitivity to volatile amines and shrimp freshness.The results of Morphology and optical properties show that with the increase of CLDES concentration,the roughness of surface and cross section of CSDF increased,and the dispersibility of curcumin,a*and b*first decreased and then increased slightly.The dispersibility,a*and b*were the highest in CSDF-8.The color responsiveness of CSDF to volatile amines also decreased first and then increased,and the color responsiveness was the highest in CSDF-8.The increase of CLDES concentration decreased the tensile strength of CSDF,and increased the hydrophilicity,elongation at break,UV barrier properties and crystallinity of CSDF.The results of freshness monitoring of shrimp showed that the content of total volatile salt-based nitrogen increased from 3.47 mg/100 g to 13.23 mg/100 g during 0 h to 18 h of storage.And CSDF exhibited a transition from yellow to orange-red,monitoring the transition of shrimp from fresh to less fresh.These results indicated that the CSD self-assembly system can be directly used to prepare smart labels,and it performed well in indicating the freshness of shrimp.In summary,this thesis developed a green method based on NADES-mediated short-chain amylose self-assembly to prepare SNP with different morphology and size.On the basis of this method,the encapsulation of curcumin in SNP was achieved by CLDES-mediated short-chain amylose self-assembly.And the application prospect of this self-assembly system in smart labels was discussed.