| Zein,as a natural macromolecular protein with a wide range of sources and environmental friendliness,has good biocompatibility and unique self-assembly characteristics to be used as a good carrier for loading bioactive substances.The zein and polysaccharide can interact to form a complex.The participation of polysaccharides greatly improves the important functions of protein,such as gelation,emulsification,solubility,and foaming properties.It can also embed and protect the bioactive components.However,the conventional preparation methods still have some shortcomings,such as low embedding efficiency and poor stability.In this paper,multimode frequency ultrasound was used to control the self-assembly of zeinpolysaccharide and embed resveratrol;and the effects of multi-mode frequency ultrasound on the structural characteristics and embedding properties of the zeinpolysaccharide complex were studied.Furthermore,the effects of ultrasonic treatment on the stability,emulsification,and in vitro digestion of the complex were studied,and the internal relationship between the structural and functional properties of the complex was established.The main conclusions are as follows:(1)Using zein,anionic polysaccharide gum Arabic(GA),and cationic polysaccharide chitosan(CS)as raw materials,two kinds of zein-polysaccharide nanocomposites were prepared by ultrasonic induced protein and polysaccharide selfassembly technology,which were used to embed resveratrol.The effects of mass ratio of protein to polysaccharide and ultrasonic parameters(ultrasonic frequency,power,time)on the protein-polysaccharide complex were studied with particle size and Zeta potential as indexes.At the same time,the effect of ultrasonic treatment on the embedding of resveratrol by protein-polysaccharide complex was analyzed with the embedding rate and loading amount as indexes.The results showed that ultrasonic treatment significantly reduced the particle size of the zein-polysaccharide complex.For Zein/GA complex with an optimal mass ratio of 1:1,the particle size decreased by44.69 nm,and the absolute value of Zeta potential increased by 5.16 m V under the conditions of ultrasonic frequency 20/40 k Hz,power 240 W,and time 15 min.For Zein/CS complex with an optimal mass ratio of 5:1,under the conditions of ultrasonic frequency 20/40/60 k Hz,power 300 W,and time 20 min;the particle size of the composite decreased by 31.29 nm,and there was no significant change in Zeta potential.Ultrasonic treatment significantly improved the embedding rate and loading capacity of zein-polysaccharide complex to resveratrol,especially the embedding rate and loading capacity of Zein/CS complex to resveratrol reached 72.13% and 6.01%,respectively.(2)The effects of ultrasonic treatment on the molecular structure and surface morphology of zein-chitosan complex were studied by fluorescence spectroscopy,circular dichroism,Fourier transform infrared spectroscopy,and atomic force microscopy.The results showed that ultrasonic treatment changed the conformation and secondary structure of the protein and the microenvironment of resveratrol chromophore.Compared with the control sample,ultrasonic treatment increased the fluorescence intensity of Zein,exposed more hydrophobic and polar groups,decreased the fluorescence intensity of resveratrol,and the maximum wavelength shifted blue.The ?-helix content of Zein increased by 15.0% and 26.40%,while the ?-fold content decreased by 14.68% and 25.58%,respectively.The results of Fourier transform infrared spectroscopy and X-ray diffraction pattern showed that ultrasonic wave induced the formation of hydrogen bonds between molecules and did not change the crystal structure of the composite.Differential scanning calorimetry(DSC)confirmed that ultrasonic treatment improved the thermal stability of the composites,and the denaturation peak temperatures were 67.7? and 64.6? to 68.6? and 69.4?,respectively.The results of surface microstructure observation(SEM and AFM)showed that ultrasonic treatment reduced the aggregation degree of the composite and made the particle size distribution more uniform.These results indicated that the interaction among protein,polysaccharide,and polyphenol induced by ultrasound was enhanced,and the stability was increased,which was beneficial to improve the loading capacity of the zein-chitosan complex for resveratrol.(3)The effects of ultrasonic treatment on the functional properties of zein-chitosan complex were studied with emulsifying property,physical and chemical stability,and release rate as indexes.The results showed that the retention rate of resveratrol in Zein/CS-Res nanocomposites prepared by ultrasonic wave increased by 29.40% in the light stability test.After heat treatment at 75?,85?,and 95?,the retention rate of resveratrol was increased to 88.32%?94.85%,which provided a good chemical stability for resveratrol.In a wide range of p H(3.0?7.0)and salt ion concentration(0?200 m M),the stability of the composite after ultrasonic treatment was significantly increased compared with that control.In addition,the storage stability of the composite was enhanced under all p H conditions,and the highest resveratrol retention rate was 80.34%when the composite was stored at p H 4.0 for 20 days.Ultrasonic treatment did not significantly change the release characteristics of the compound in the gastrointestinal tract,but the emulsifying activity and emulsifying stability of the complex were increased by 54.79% and 53.75%,respectively. |
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