Preparation,Physicochemical Characterization And Release Kinetics Of Ethyl Butyrate,Hexanal And Hexanol Inclusion Complexes With ?- And ?-cyclodextrin

Cyclodextrins?CDs?,as a good inclusion wall material,could encapsulate volatile and unstable compounds into the cavities to form more stable inclusion complexes.It could improve the water solubility and control the release behavior of the guests.In this paper,?-and ?-CD were selected as inclusion hosts,and ethyl butyrate,hexanal and hexanol were taken as guests.CD complexes were prepared by coprecipitation combined with lyophilization method.The inclusion ratio,physicochemical characterization,and release kinetics of the CD complexes under different storage conditions were analyzed.At last,the comparison of inclusion ability between CDs and indica rice starch was investigated.The main results were as follow:1.Through single factor tests,the effect of different host/guest molar ratio?1/4:1 to 3/2:1?,ultrasonic time?15min to 75min?and ultrasonic temperature?40? to 80??on the inclusion ratio of CD complexes were studied.The results showed that ?-CD-ethyl butyrate complex prepared under 1/2:1 molar ratio,45 min and 60? has the optimal inclusion ratio as 40.67%;?-CD-ethyl butyrate complex prepared under 1:1 molar ratio,30 min and 60? has the optimal inclusion ratio as 87.69%;?-CD-hexanal complex prepared under 1/3:1 molar ratio,45 min and 70? has the optimal inclusion ratio as 14.10%;?-CD-hexanal complex prepared under 1/2:1 molar ratio,45 min and 70? has the optimal inclusion ratio as 14.41%;?-CD-hexanol complex prepared under 1:1 molar ratio,30 min and 60? has the optimal inclusion ratio as 37.08%;?-CD-hexanol complex prepared under 1:1 molar ratio,45 min and 60? has the optimal inclusion ratio as 43.97%.2.On the basis of the single factor tests,the optimal inclusion parameters of six CD complexes were determined by orthogonal array design experiments.The results showed that the suitable parameters of ?-CD-ethyl butyrate complex was 1:1 molar ratio,30 min and 50? with inclusion ratio as 46.69%;the suitable parameters of ?-CD-ethyl butyrate complex was 1:1 molar ratio,45 min and 60? with inclusion ratio as 95.59%;the suitable parameters of ?-CD-hexanal complex was 1/3:1 molar ratio,30 min and 70? with inclusion ratio as 15.66%;the appropriate parameters of ?-CD-hexanal complex was 1/2:1 molar ratio,30 min and 70? with inclusion ratio as 16.64%;the appropriate parameters of ?-CD-hexanol complex was 1:1 molar ratio,45 min and 50? with inclusion ratio as 40.19%;the appropriate parameters of ?-CD-hexanol complex was 3/2:1 molar ratio,45 min and 60? with inclusion ratio as 45.11%.3.The guest release curves of six CD complexes were studied through storage experiment.The results showed that the relative humidity?RH?and temperature had influence on the release behavior of CD complexes.The lower the RH or temperature was,the slower the guests released from the CD complexes.The release kinetics of the CD complexes was described by the Avrami equation.The results showed that the rate of guest release was faster with both increasing RH and temperature,and the effect of RH was stronger.The k value of ethyl butyrate,hexanal,and hexanol CD complexes were respectively ranged from 1.2282 to 13.4564s^-1,0.5325 to 6.5634s^-1,and 0.0842 to 1.6738s^-1.This indicated that hexanol CD complexes had the best storage stability,followed by hexanal and ethyl butyrate CD complexes.4.Physicochemical characterization of CD complexes presented:?1?FT-IR analysis showed that,for the CD complexes,most absorption peaks of the guests were covered by the CD skeletons except the characteristic absorption peak of C=O around 1730cm^-1,and no new absorption peaks appeared;?2?the 13C-NMR spectra revealed that the CD complexes possessed the chemical shift peaks of the carbon atoms of the guests,and the chemical shift peaks of the carbon atoms of CD skeletons moved weakly owing to the effect of hydrogen bond;?3?DSC analysis exhibited that after encapsulating with guests,the phrase transition temperature and the enthalpy of the CD complexes changed,and the six CD complexes ranked in descending order of the thermal stability?enthalpy value?were ?-CD-hexanol?132.04J/g?,?-CD-hexanal?129.52J/g?,?-CD-hexanal?124.32J/g?,?-CD-hexanol?107.74J/g?,?-CD-ethyl butyrate?99.58J/g?,and ?-CD-ethyl butyrate?68.33J/g?,respectively;?4?XRD analysis showed that the position of diffraction peaks of the CDs and CD complexes were different,and the CD complexes exhibited fewer and broader diffraction peaks than those of the CDs;?5?SEM analysis showed that after encapsulation,the coarse and loose surfaces with anomalous shapes of the CDs changed into smooth and compact surfaces with rhombic columnar shapes of the CD complexes.The synthesis results indicated that the CDs became the new phases after encapsulating with the guests,and the CD complexes were indeed formed.5.Indica rice starch prepared in laboratory was used to encapsulate the three guest compounds.The results showed that the inclusion ratio of ethyl butyrate,hexanal and hexanol indica rice starch complexes were respectively 16.45%,28.99% and 24.67%;except for henaxal,the inclusion ratio of ethyl butyrate CD complexes and haxanol CD complexes were higher than the corresponding indica rice starch complexes.It indicated that CDs had some advantages as the inclusion materials for this kind of guest compounds.