Preparation,Structural Characterization And Release Of Small Molecule Flavor Substances Encapsulated By Indica Rice Starch

Indica rice starch,which has abundant source and relative low cost,is famous of its high content of amylose.And it has its specialties,such as having the potential to include low-boiling,volatile,water-insoluble small molecule flavor substances,which contributes to improve the solubility and storage period of flavor substances.This experiment chose indica rice starch to include small flavor substances with different polarity by hot melting method,including linalool,2-heptanol,l（-）-menthol,4-heptanolide,l-（-）-cavrone and menthone.By comparing the inclusion rate and the storage stability under different conditions,the most suitable substance for indica rice starch to form inclusion was determined.And DSC、XRD、FT-IR、¹³C-NMR、SEM were used to analyse the structure characterization of inclusion complexes.The results were as follows:1.To discuss the effect of the host/guest weight ratio,inclusion temperature and extract temperature on inclusion efficiency,single factor tests were conducted.The results showed that the optimal conditions for indica rice starch-linalool inclusion were: host/guest weight ratio 10:0.2g/μL,inclusion temperature 40°C,and extract temperature 50°C,and the optimal inclusion efficiency up to 79.18%;for indica rice starch-2-heptanol inclusion complexes the optimal conditions were: host/guest weight ratio 10:0.2g/μL,inclusion temperature 40°C and extract temperature 60°C,and the optimal inclusion efficiency up to 88.10%;for indica rice starch-l（-）-menthol inclusion complexes the optimal conditions were: host/guest weight ratio 10:0.2g/μL,inclusion temperature 40°C and extract temperature 60°C,and the optimal inclusion efficiency up to 66.58%;for indica rice starch-4-heptanolide inclusion complexes the optimal conditions were: host/guest weight ratio 10:0.6g/μL,inclusion temperature40°C and extract temperature 60°C,and the optimal inclusion efficiency up to50.18%;for indica rice starch-l-（-）-cavrone inclusion complexes the optimal conditions were: host/guest weight ratio10:0.4g/μL,inclusion temperature 50°C and extract temperature 40°C,and the optimal inclusion efficiency up to 60.42%;for indica rice starch-menthone inclusion complexes the optimal host/guest weight ratio, inclusion temperature and extract temperature were 10:0.4g/μL,40°C and 50°C,respectively,and the optimal inclusion efficiency up to 41.63%.2.On the basis of single factor tests,the optimal inclusion parameters of six inclusion complexes were determined by L9（34）orthogonal texts.The results suggested that for indica rice starch-linalool inclusion were: host/guest weight ratio 10:0.2g/μL,inclusion temperature 40°C,and extract temperature 60°C,and the optimal inclusion efficiency up to 59.91%;for indica rice starch-2-heptanol inclusion complexes the optimal conditions were: host/guest weight ratio 10:0.2g/μL,inclusion temperature50°C and extract temperature 50°C,and the optimal inclusion efficiency up to 77.01%;for indica rice starch-l（-）-menthol inclusion complexes the optimal conditions were:host/guest weight ratio 10:0.2g/μL,inclusion temperature 50°C and extract temperature 70°C,and the optimal inclusion efficiency up to 59.25%;for indica rice starch-4-heptanolide inclusion complexes the optimal conditions were: host/guest weight ratio 10:0.5g/μL,inclusion temperature 50°C and extract temperature 70°C,and the optimal inclusion efficiency up to 50.15%;for indica rice starchl-（-）-cavrone inclusion complexes the optimal conditions were: host/guest weight ratio10:0.3g/μL,inclusion temperature 60°C and extract temperature 60°C,and the optimal inclusion efficiency up to 56.46%;for indica rice starch-menthone inclusion complexes the optimal host/guest weight ratio,inclusion temperature and extract temperature were 10:0.3g/μL,50°C and 60°C,respectively,and the optimal inclusion efficiency up to 42.34%.3.The release kinetics of six inclusion complexes was evaluated by Avrima equation.The results revealed that the flavors released rate increased with the increasing of relative humidity at constant temperature,and at constant relative humidity,the flavors released more easily under high temperature.The k value of indica rice starch-linalool,indica rice starch-2-heptanol,indica rice starch-l（-）-menthol,indica rice starch-4-heptanolide,indica rice starch-l-（-）-cavrone and indica rice starch-menthone were ranged from 0.0816 to 0.1418d^-1,0.1084 to 9.0367d^-1,0.1136 to 0.1155d^-1,0.0689 to 0.1663d^-1,0.0262 to 0.0558d^-1 and 0.0743-0.2379d^-1,respectively.This indicated that indica rice starch-2-heptanol has the best storage stability,followed by indica rice starch-menthone,indica rice starch-linalool,indica rice starch-l（-）-menthol,indica rice starch-4-heptanolide and indica rice starchl-（-）-cavrone.4.The results of structure characterization:（1）DSC analysis showed that after inclusion,the phrase transition temperature and enthalpy of inclusion complexes changed,which confirmed the formation of inclusion complexes.And enthalpy showed that the indica rice starch-l-（-）-cavrone（136.61g/J）has the most thermostability,followed by indica rice starch-4-heptanolide（106.10g/J）,indica rice starch-l（-）-menthol（93.95g/J）,indica rice starch-linalool（92.75g/J）,indica rice starch-menthone（64.64g/J）and indica rice starch-2-heptanol（57.18g/J）;（2）XRD analysis showed that all inclusion complexes were typical Vh-type crystal.The position,quantity and strength of diffraction peaks were different from original samples,which indicated the formation of inclusion complexes;（3）FT-IR analysis revealed that C=O functional groups were detected around 1670cm-1 and 1774cm-1 in indica rice starch-non-polar flavors.For indica rice starch-polar flavors,most absorption peaks of flavors were covered by gelatinized indica rice starch.The formation of inclusion complexes were proved by the changes of characteristic peak position and intensity;（4）¹³C-NMR analysis exhibited that signals from 0 to 50 ppm are usually attributed to methyl,methylene,and methine groups of inclusion complexes.The existence of flavors was determined by the chemical shift and changeable intensity of C1-C6 of inclusion complexes.（5）SEM analysis showed that,the spatial structure became more closely after inclusion.The holes formed because of the small molecule flavor substances passing through the surface into the cavity,which indirectly proved the formation of inclusion complexes.