| Porous Starch has good adsorption performance and is widely used.Because the raw rice starch is relatively low sensitive to enzyme,it is not easy to prepare high adsorption porous starch by enzymolysis,therefore,the sensitivity of starch to enzyme can be improved by pretreatment of starch.In this study,Ningxia Rice was used as raw material,starch was modified by hygrothermal treatment,ultra-high pressure treatment and heat combined with ultra-high pressure treatment,and then the porous starch was prepared by enzymatic hydrolysis with complex enzyme(alpha-amylase and saccharifying enzyme),the specific volume,solubility and swelling rate of different porous starches were determined,and the adsorption properties of different porous starches were determined.The Crystal Structure,particle size and particle shape of different starches were analyzed by fitting the adsorption process with isothermal curve,lycopene was embedded in porous starch to study the stability of lycopene under different storage conditions and to simulate the release of lycopene from gastrointestinal fluid in vitro.The main findings are as follows:(1)Starch pretreatment process and adsorption thermodynamic analysis:the optimum process for wet and hot treatment was moisture content of 30%,treatment temperature of 110℃ and treatment time of 6 h.Under these conditions,the oil absorption rate of porous starch was 98.40%.The optimum conditions for ultra-high pressure treatment were starch emulsion concentration of 30%,pressure of 300 MPa,treatment time of 20 min,starch sensitivity to enzyme of 4.80%,porous starch oil absorption rate of 112.60%.The optimum conditions of heat combined ultra-high pressure treatment were as follows:starch emulsion concentration of 30%,pressure of 250 MPa,treatment time of 10 min,treatment temperature of 50 ℃,starch sensitivity to enzyme was 5.32%,and porous starch oil absorption rate reached 125.6%.The isotherm fitting of different porous starches showed that the isotherm adsorption of methylene blue was more consistent with the monolayer adsorption of Langmuir model for porous starches prepared by enzyme-assisted hygrothermal treatment.The isothermal adsorption of porous starch prepared by compound enzyme method,ultra-high pressure assisted enzyme method and thermal binding ultra-high pressure assisted enzyme method to methylene blue is more consistent with the Freundlich model of multi-layer adsorption.Several kinds of porous starch are preferential adsorption.The maximum adsorption capacity of methylene blue was 58.48 mg/g,which was 32.76%higher than that of porous starch prepared by compound enzyme method.(2)Analysis of different starch structure:X-ray crystal diffraction results showed that the moisture and heat treatment and ultra-high pressure treatment only reduced the crystallinity of starch,but the crystal form of starch did not change significantly.The heat combined with ultra-high pressure treatment made the crystal form of starch transforming from type A to type B,and enzymatic hydrolysis did not change the crystal structure of starch.Fourier transform infrared spectroscopy(FTIR)showed that the chemical structure of starch was not changed by pretreatment and enzymatic hydrolysis.The results of scanning electron microscopy showed that starch particles were seriously aggregated and damaged after wet and hot treatment,and the adhesion was significantly improved after enzymatic hydrolysis.The heat combined with ultra-high pressure treatment assisted the preparation of porous starch had the best pore-forming effect.The results showed that the starch particle size was significantly increased after wet and heat treatment,and the starch particle size decreased and the specific surface area increased after enzymatic hydrolysis.The starch particle size was slightly decreased after ultra-high pressure treatment,and the starch particle size increased and the specific surface area increased after enzymatic hydrolysis.After heat combined with ultra-high pressure treatment,the starch particle size distribution range became larger,the small particles decreased,and the large particles increased.After enzymatic hydrolysis,the starch particle size decreased,and the specific surface area reached 2064m2/kg,which was the maximum.(3)Study on the kinetics of lycopene embedded in porous starch and its simulated release in vitro:under the same light conditions,temperature and storage time,the retention rate of lycopene embedded in porous starch was higher than that of lycopene embedded in unembedded and starch.(FTIR)showed that lycopene was embedded in porous starch.According to the release rules of lycopene microcapsules in simulated stomach and intestinal fluid,it was found that the Korsmeyer-Peppas equation and the first-order equation with the best fitting effect in gastric fluid were Korsmeyer-Peppas equation,which belonged to the non-Feck diffusion mechanism.In the kinetic equation of simulated intestinal fluid,Higuchi equation and Korsmeyer-Peppas equation model fit well and belong to Fick diffusion. |
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