Preparation,Structure Characterization And Release Study Of Enzymolysis Modified Octenyl Succinate Starch-Menthol Inclusion Complexes

Menthol is one of the most widely used spices in the world,with the advantages of peppermint flavor,antibacterial,anticancer and so on,but it has low water solubility,high volatility and poor stability,which limits its application in food,daily necessities,tobacco and medicine.In recent years,embedding technology is often used to reduce the volatilization of spices and flavors and improve their stability in storage and use.Enzymatic modified octenyl succinate starch（E-OSAS）is a commonly used wall material,which has the advantages of external hydrophilicity and internal hydrophobicity,low viscosity,good entrapment performance and controlled release of flavor substances.In order to reduce the volatilization of menthol,improve the stability of menthol and explore the release law of menthol in the inclusion complex,a series of E-OSAS with different molecular weight were prepared by using octenyl succinate starch（OSAS）prepared from waxy corn starch and octenyl succinic anhydride as raw material and pullulanase as enzymatic hydrolytic agent.Then menthol was embedded in E-OSAS to prepare enzymatic modified octenyl succinate-menthol inclusion complex（E-OSAS-MEN）.Finally,the release of menthol at different p H and temperatures and in simulated saliva was determined by GC-MS,and the release kinetics of menthol in simulated saliva with and withoutα-amylase was studied by Weibull equation.This could provide some theoretical basis for the application of menthol in industry.The main conclusions are as follows:Through the characterization of OSAS and E-OSAS,it was proved that the waxy corn starch was successfully introduced into OSA group and the esterification reaction was carried out successfully.The molecular weight and apparent viscosity of E-OSAS decreased with the increase of enzyme content.The degree of substitution of E-OSAS was higher than that of OSAS,and the degree of substitution of E-OSAS increased with the increase of enzyme content.TGA results showed that waxy corn starch,OSAS and E-OSAS were mainly degraded in two stages.The order of thermal stability of E-OSAS was waxy corn starch>OSAS>E-OSAS,but with the increase of enzyme content,the thermal stability of OSAS increased gradually.XRD results showed that waxy corn starch and OSAS belonged to A-type structure,while E-OSAS belonged to B+V-type structure.TEM showed that the E-OSAS particles were spherical.With the increase of the amount of enzyme,the smaller the particle size and PDI of E-OSAS,the greater the absolute value of Zeta potential.E₄₀-OSAS has the smallest particle size,the best uniformity and the best stability.The FTIR results showed that the hydroxyl group of menthol was embedded in the hydrophobic cavity,while the isopropyl group did not enter the cavity completely.E-OSAS may incorporate menthol in the form of hydrogen bond association.In addition,the XRD results showed that all the inclusion complexes were of B+V type structure.With the increase of the addition of pullulanase,the embedding rate and loading of menthol inclusion complex showed an increasing trend,in which the embedding rate of E₄₀-OSAS-MEN was 64.22%,and the loading was 13.05%,which reached the maximum in all inclusion compounds.E₄₀-OSAS-MEN had the smallest particle size,the best uniformity and the best stability.The TGA results showed that the thermal stability of the inclusion complexes was better than that of the wall material,and the thermal stability of the inclusion complex was improved gradually with the increase of the amount of enzyme,among which E₄₀-OSAS-MEN had the best thermal stability.The release rate of menthol in E-OSAS-MEN was measured by GC-MS,and the results showed that E₄₀-OSAS-MEN retained more than 90%of menthol in buffers at different p H,which could adapt to a variety of p H ranges.With the increase of temperature,the release rate of menthol in the inclusion complex increased from 5%to 25%.In the absence ofα-amylase in simulated saliva,the inclusion complex released only 18%of menthol,while in the presence ofα-amylase,the inclusion complex released about half in the first 50 minutes,and menthol was completely released after 5 h of enzymolysis.The inclusion complex was released faster in simulated saliva containingα-amylase.The Weibull equation was used to fit the release rate and time of menthol in simulated saliva.The results showed that in simulated saliva withα-amylase,the release mechanism of the inclusion complex was close to the diffusion-limited reaction kinetics.In the absence ofα-amylase,the release mechanism of the inclusion complex was close to zero-order release kinetics.