Preparation, Characterization And Release Kinetics Of ?- And ?-cyclodextrin Inclusion Complexes With Ethyl Propionate And Valeric Acid

Cyclodextrins?CDs?are cyclic oligosaccharides of hydrophobic cavity with hydrophilic outside.They often used as the host to encapsulate drug molecule and small flavor compounds.The inclusion can improve the solubility of the guest and reduce their volatility,so expand their application.Ethyl propionate and valeric acid are small flavor compounds,the high volatility and low solubility limit their application.The inclusion complex of ethyl propionate and valeric acid with ?-and ?-cyclodextrin were prepared by a modified co-precipitation method,the inclusion ratio was used as the reference to select the optimal conditions of preparation of inclusion complexes.Then,the release character and structural characterization of inclusion complexes were measured in different ways.We choose amylopectin and waxy rice starch to prepare the inclusion complexes with ethyl propionate and valeric acid,and then analysed the inclusion ability of ?-and?-cyclodextrin.The main results were as follows:1.Based on on the inclusion ratio of CD complexes,the effect of different host/ guest molar ratio?1/4:1 to 3/2:1?,ultrasonic time?15 min to 75 min?and ultrasonic temperature?40? to 80??were studied by a single factor tests.The results showed: ?-CD-ethyl propionate complex prepared under 1/3:1 molar ratio,45 min and 60? has the best inclusion ratio as 9.53%;?-CD-valeric acid complex prepared under 1/3:1 molar ratio,45 min and 50? has the best inclusion ratio as 41.31%;?-CD-ethyl propionate complex prepared under 1/2:1 molar ratio,60 min and 60? has the best inclusion ratio as 32.11%;?-CD-valeric acid complex prepared under 1:1 molar ratio,30 min and 50? has the best inclusion ratio as 10.34%.2.The optimal inclusion conditions were determined by the orthogonal array design,the results showed that the the inclusion ratio of ethyl propionate-?-cyclodextrin complex could reach 10.25% when ?-cyclodextrin/ethyl propionate molecular ratio was 1/3:1,ultrasound time was 45 min and ultrasound temperature was 60?.The inclusion ratio of valeric acid-?-cyclodextrin complex could reach 43.99% when ?-cyclodextrin/valeric acid molecular ratio was 1/3:1,ultrasound time was 30 min and ultrasound temperature was50?.The results showed that the the inclusion ratio of ethyl propionate-?-cyclodextrin complex could reach 32.15% when ?-cyclodextrin/ethyl propionate molecular ratio was1/3:1,ultrasound time was 50 min and ultrasound temperature was 50?.The inclusion ratio of valeric acid-?-cyclodextrin complex could reach 10.58% when ?-cyclodextrin/valeric acid molecular ratio was 1:1,ultrasound time was 30 min and ultrasound temperature was 40?.3.The results of release properties at different temperetrues and humidities were investigated.The result showed the retention ratio of the complexes decreased rapidly,and the speed became slower,the retention ratio eventually leveled off,as time increasing.The relationship between retention rate of guests and time during release was described by a mathematical model of Avrami equation,the results showed that both high tempreture and high relative humidity also increased the release speed,and the influence of humidity was stronger.The k value of valeric acid-?-CD complex ranged from 1.88×10^-6 to 1.56×10-5,ethyl propionate-?-CD complex ranged from 1.24×10^-6to 2.18×10^-6.This indicated that ethyl propionate-?-CD complex had better storage stability than valeric acid-?-CD complex.4.The structures analysization of the inclusion complexes showed:?1?The Infrared spectrum?FT-IR?showed that compared with the cyclodextrins,the FTIR spectrum of the inclusion complexes appeared C = O double absorption peak at about 1735 cm^-1 and 1712cm^-1,and no other chemical bond was formed;?2?The CP/MAS13 C solid state nuclear magnetic results showed the peaks at 102.01 and 97.23 ppm of atom C1 of ?-CD changed into a single peak.Integrated peaks at about 60 ppm of C6 in ?-CD also turned into a single signal.?3?Differential scanning calorimetry?DSC?analysis indicated that the phase transition temperature of cyclodextrins increased,and the endothermic enthalpy decreased after the inclusion reaction.The enthalpy of the four complexes ranked in increasing order of the thermal stability were ?-CD-valeric acid?64.26 J/g?,?-CD-ethyl propionate?90.58J/g?,?-CD-ethyl propionate?98.92J/g?,?-CD-valeric acid?123.75J/g?;?4?X-ray diffraction?XRD?analysis showed that compared with the control sample,the X-ray diffractograms of the cyclodextrin inclusion complexes showed peak shifting and the diffraction peak decreased,which indicated the crystallinity decreasing of the cylodextrins;?5?Scanning electron microscopy?SEM?results displayed the surface morphology of cyclodextrin changed from irregular state to the smooth surface.5.The inclusion ratio of the amylopectin and glutinous starch showed: amylopectin inclusion complexes with ethyl propionate and valeric acid are 8.03% and 9.62%,glutinous starch inclusion complexes with ethyl propionate and valeric acid are 8.68% and10.76%.The inclusion ratio starch was were smaller than cyclodextrins,although the inclusion ratio of glutinous starch was bigger.6.Characterization starch inclusion complexes.?1?Infrared spectrum?FT-IR?:TheFTIR spectrum of the inclusion complexes appeared C=O double absorption peak at 1735cm^-1 and 1712 cm^-1,and no other chemical bond was formed;?2?Differential scanning calorimetry?DSC?analysis indicated that after the inclusion reaction the phase transition temperature of starch increased,the endothermic enthalpy decreased;?3?Scanning electron microscopy?SEM?results displayed the surface morphology of starch changed from typical starch granules to a paper sheet inclusion complexes with many small holes through them.