Study On The Preparation Of Debranched Glutinous Rice Starch And Its Application Of Encapsulated Lycopene

Debranched starch（DBS）is an enzyme-modified starch that breaks theα-1,6 glycosidic bond of amylopectin and then debranched into amylose.Amylose can form a linear helix structure with hydrophobic inside and hydrophilic outside in aqueous solution to achieve self-assembly with volatile and insoluble molecules and improve its solubility,stability and slow release,thus amylose becomes a good wall material for encapsulation and becomes a hot research topic.In this study,natural glutinous rice starch（GRS）was used as raw material and debranched starch with different branching degree（DB）was obtained by hydrolysis using Pullulanase,and the structural properties,physical and chemical properties of DBS were investigated.The effect of DB value of starch on the loading capacity,stability and controlled release properties of lycopene was also investigated.The main findings of the study are as follows:（1）DBS with different branching degrees were prepared by pullulanase debranching,and the molecular structures and physicochemical properties of GRS and DBS were characterized.Enzymatic digestion significantly reduced the relative molecular mass and DB of starch,and increased the amylose content and water solubility of the system.Powdered debranched starch showed fragmentary crystal stack and the percentage of starch particles with small size increased obviously.1047/1022 cm^-1 and the full width at half peak（FWHM）indicated that the ordered arrangement within the starch molecule gradually shifts to the disordered state arrangement and its short-range molecular conformation is disrupted.The appearance of diffraction peaks around 7.8°,13.8°and 21.3°for debranched starch indicates the presence of V-shaped crystals within the starch.The ¹³C CP/MAS NMR results showed that debranching treatment disrupted the crystalline region of GRS and increased the content of single helix structure.DSC analysis showed that intensity of the heat absorption peaks of DBS was significantly weakened compared with that of GRS,in which the heat absorption peak of DBS-500 disappeared,indicating that internal crystal structure of starch molecules was severely damaged,and the paste transition temperature of DBS was found to increase gradually.Debranched starch with V-shaped structure shows better resistance to digestion and more resistant to enzymatic digestion.（2）The results of lycopene loading by DBS with different branching degrees showed that the complex formed by DBS with 11.42%branching degree had the highest encapsulation rate of 64.81%.SEM,particle size and Zeta-potential results showed that DBS and lycopene formed more stable,spherical crystals with more uniform particle size through electrostatic interactions.FTIR spectroscopy not only confirmed the formation of intermolecular hydrogen bonds in the complexes,but also showed that decreasing the branching degree of starch promoted the formation of a more ordered and dense molecular structure of complexes between DBS and lycopene.DBS/LYC complexes have a typical V-shaped crystal structure,while excessively debranched DBS-500 hinders the crystallization of the complexes to some extent.Existence of helical structures in debranched starch provides a basis for loading lycopene,possibly through the forming complexes by interactions between alkyl chains.TGA results showed that the interaction between DBS and lycopene gradually increased,and the thermal behavior improved when branching degree of starch was reduced.（3）We investigated the stability,antioxidant activity and in vitro simulated release properties of DBS/LYC complexes.These results revealed that retention indices of the complexes during degradation were both significantly higher than those of the physical mixture and free lycopene,and the loading of debranched starch could effectively reduce the deterioration of lycopene and improve the stability.The complexation of DBS also effectively preserves the free radical scavenging power of lycopene.The release of the DBS/LYC complex in simulated gastric fluid was significantly lower than that in simulated intestinal fluid,suggesting improved stability of lycopene in an acidic environment and sustained release to full absorption at a relatively constant rate in the small intestine,improving the bioavailability of lycopene.