Preparation Of Slow-Digested Starch By Extrusion Combined Enzymatic Method And Its Physicochemical Properties

Slow-digested starch can be completely absorbed by the human body,but it is absorbed slowly and release energy slowly.Due to its unique physiological characteristics,slow-digested starch has received extensive attention.The Preparation of Slow-digested Starch by Extrusion Combined Enzymatic Method has the advantages of simple process,easy operation,no pollution,no post-treatment,and strong controllability.In order to study the optimal conditions for the preparation of slow-digested starch by extrusion and enzymatic method and the formation mechanism,we selected three different linear content of corn starch H?74.2%?,M?51.5%?,L?0.1%?separately,studing the effect of extrusion on the digestibility of different linear content corn starch.On this basis,a four-factor five-level quadratic orthogonal rotation combination test was designed to optimize the optimal preparation conditions and prepare under the optimal preparation conditions.Through the experiments of exploring the blood sugar elevation index of slow-digested starch and studying the formation mechanism of slow-digested starch by molecular structure analysis,the following conclusions are drawn:1.When the screw speed is 70r/min,the sleeve temperature is 60°C,and the moisture content of the feed material is 20%,the slow-digested starch content in the H corn starch extrudate is the highest;when the screw speed is 150r/min,the temperature of sleeve is 80°C and the feed moisture content is 25%,the content of slow-digested starch in M corn starch extrudate is the highest;when the screw speed is 150r/min,the temperature of sleeve is 60°C,and the feed moisture content is 20%,the content of slow-digested starch in L corn starch extrudates was the highest;The content of fast-digested starch decreased and the slow-digested starch increased when starch was squeezed.The content of fast-digested gradually increased gradually as the content of amylose increased.2.The content of slow-digested starch produced is different under the conditions of different enzymatic hydrolysis time,substrate concentration and enzyme addition amount.When the enzymatic hydrolysis time was 8h,the content of slow-digested starch in corn starch with different content of amylose was the highest.With the content of amylose increased,the content of slow-digested starch increased.When the concentration of substrate was 15%,the content of corn starch in different amylose content was the highest.With the increase of amylose content,the slow-digested starch increased.When the amount of pullulanase was 30u/g,the content of slow-digested starch in corn starch with different content of amylose was the highest,and the slow-digested starch in H corn starch was significantly higher than the other two kinds of corn starch;when the temperature was 55°C,the content of slow-digested starch was the highest in different amylose content corn starch,and the content of slow-digested starch decreased with the increase of amylose content.3.Taking substrate concentration,enzyme addition amount and temperature as test factors,and slowly digesting starch content as test index,the optimal process parameters for preparing slow-digested starch using H corn starch were obtained:substrate concentration 19%,enzyme addition amount is 30u/g,temperature is 53°C,the slow-digested starch content is up to 40.81%;M corn starch to prepare slow-digested starch optimal process parameters:substrate concentration is15%,enzyme addition amount is 30u/g,temperature is 50°C,the highest content of slow-digested starch is 39.52%;the optimal process parameters for preparing slow-digested starch from L corn starch:substrate concentration is 11%,enzyme addition amount is 28u/g,temperature is 53°C,the content of slow-digested starch is up to 41.42%.4.Through the analysis of the original starch and product,reached the following conclusions:?1?It is known from the gelatinization property that the rupture strength of L corn starch is large,the peak viscosity of the extrudate is lower than the original corn starch,and the slow-digested starch is not aging easily.?2?SEM shows that the untreated corn starch has a smooth surface and the surface of the extrudate particles is porous.The slow-digested starch granules prepared by enzymatic hydrolysis become smaller,the surface is smooth,and the rib structure is obvious.?3?The results of infrared spectrum showed that there was no new functional group in the corn starch extrudate,but the crystal structure was destroyed.The slow-digested starch produced a new absorption peak at 3730 cm^-1,indicating that hydrogen bonds were generated between molecules and molecules.Recrystallization and cross-linking make the starch slowly digestible.The original corn starch has the strongest crystallinity,and particularly the L-digested starch has the strongest crystallinity.?4?The crystal structure of the corn starch extrudate is destroyed,and the crystal structure of the prepared slow-digested starch is changed from the type A of the original corn starch to the coexistence of type A and type B,and the crystallinity of the slowly digested starch is H>M>L.L corn starch has the highest content of slow-digested starch.The crystal structure of starch,intramolecular and intermolecular hydrogen bonds and chain length affect the digestibility of starch.?5?Untreated corn starch is distributed in a region with a larger molecular size,and the molecules of the extrudate and the slowly digested starch are smaller than the untreated corn starch molecules,and the L is slowly digested compared to the H and M slow-digested starch.Starch is distributed in areas with large molecular sizes.?6?It can be known from DSC that the relationship between the enthalpy change values is the original sample>extrudate>slow-digested starch,the starting temperature of different amylose corn starch is similar,the crystal form is the same,the peak temperature of the original corn starch>extrudate>slow-digesting starch,the heat of gelatinization of slow-digested starch is the least,and the crystal structure of slow-digested starch is poor,so slow-digested starch is slow-digestible.5.The amount of glucose released increased with the increase of hydrolysis time of The three original samples and extrudates.The hydrolysis of slow-digested starch is different from that of the original sample and extrudate.It increases with the increase of hydrolysis time and then increases with the stationary phase.The glucose release of slow-digested starch is the least in unit time,and the starch glycemic index of slow-digested starch which is prepared by extrusion and enzymatic hydrolysis is reduced.6.Pearson correlation analysis showed that the correlation between starch digestibility and amylose content was significant.The higher the amylose content,the higher the content of fast-digested starch and slow-digested starch.The presence of an amorphous structure in starch requires the absorption of more energy to gelatinize the starch.The higher the fast-digested starch content,the higher the glycemic index,and the higher the resistant starch content,the lower the glycemic index.The combination of extrusion and enzymatic preparation of digested starch combines the advantages of extrusion and enzymatic preparation of slow-digested starch,and has more controllability,which provides a theoretical basis for the actual production of slowly digested starch.