Mechanism Study Of Inhibition Effect Of Maize Cellulose With Different Molecular Weight On Starch Digestion And Its Application

Starch,a critical carbohydrate,is vital for energy supply in the human body.However,excessive starch digestion causes a rapid rise in postprandial blood glucose level which seriously endangers human health.In addition,long-term postprandial hyperglycemia is closely related to the occurrence of diabetic complications and macrovascular diseases.It is the first key point to control the rapid fluctuation of postprandial blood glucose by delaying starch digestion.Dietary fiber has effect of inhibiting starch digestion and delaying the rise of blood sugar levels after meal.Cellulose,an important insoluble dietary fiber,widely exists in cereals.Studies have shown that cellulose has the potential to inhibit starch digestion.However,the inhibitory ability of cellulose with different molecular weight on starch digestibility is still unclear.To clarify the effects of cellulose with different molecular weight on starch digestion,provide reference for accurate application of cellulose in starch-based foods base on its mechanism and propose important guidance for rational development of functional cellulose products that meet consumers’ needs.The main contents and results of this study are as follows:1.Cellulose was extracted from corn husks,and three types of cellulose with different molecular weight(named NC,MC,and SC)were prepared by acid hydrolysis.The structures of NC,MC,and SC were characterized by measuring specific surface area,X-ray diffraction(XRD),fourier transform infrared spectrometer(FTIR Spectrometer),scanning electron microscope(SEM),and atomic force microscopy(AFM),and the swelling capacity,binding water capacity and apparent viscosity were compared and analyzed.The results showed that the molecular weights of the three types of cellulose were 422500 Da(NC),27750 Da(MC),and 2202 Da(SC).NC present a long chain distribution and intertwines with each other.The crystallinity of NC was 35.5%,and its swelling capacity and apparent viscosity were significantly higher than those of MC and SC.MC was a small aggregate of multiple fibers,and its crystallinity was 49.5%,while SC was a short rod shape with completely amorphous distribution.2.The gelatinization properties of wheat starch with various concentrations of cellulose with different molecular weight were determined by a novel rapid viscosity analyzer RVA-4800 at 95°C and 140°C,respectively.The effects of cellulose on the physicochemical properties of wheat starch were further analyzed by measuring the rheological,crystalline structure,morphology and texture properties of the gel of the mixture of celluloses and wheat starch.The results showed that at 95℃,the addition of NC,MC,and SC reduced the gelatinization temperature,and increased the peak viscosity,retaining strength,disintegrating viscosity,and final viscosity.The addition of MC and SC decreased the gel hardness of wheat starch.The hardness of the gel decreased with the addition of 1.2% NC.However,when the addition amount was2.1% and 3.0%,the gel hardness of the mixture increased significantly.Under the heating condition of 140°C,the peak viscosity of wheat starch gradually increased with the increase of NC,MC and SC contents.In contrast,the final viscosity showed the opposite trend.The presence of NC,MC,and SC increased the gel hardness in a concentration-dependent manner.Dynamic rheological analysis showed that cellulose-wheat starch gel exhibited typical weak dynamic rheological properties at95°C and 140°C.The addition of NC,MC,and SC enhanced the storage modulus(G’)and loss modulus(G’’)of wheat starch gels,and all samples showed G’>G’’.Moreover,the influence of high molecular weight cellulose on viscoelastic properties is more prominent.3.The Englyst method was used to determine the inhibitory effect of three types of cellulose via in vitro digestibility of wheat starch with different additional amounts.The results showed that SC had a more obvious inhibitory effect on starch digestion when compared with NC and MC.When the supplemental level of NC,MC,and SC reached 2.1%,the proportion of RS in wheat starch digestion increased from 15.0% in the control group to 19.9%,20.4% and 46.4%,respectively.The results of glucose diffusion showed that the diffusion rate of glucose in the solution was the slowest with the presence of low molecular weight cellulose.At 300 min,the glucose dialysis delay index(GDRI)of SC increased from 25.4% to 74.3% while NC and MC only increased from 3.3% and 10.3% to 12.6% and 21.6%,respectively.4.The inhibitory effects of three types cellulose with different molecular weight on the activities of α-amylase and amyloglucosidase were determined.The fluorescence quenching effects of NC,MC,and SC on the activities of α-amylase and amyloglucosidase were analyzed by fluorescence spectrum,synchronous fluorescence spectrum and UV-visible absorption spectrum.The quenching type and binding force between celluloses and amylase were determined by analyzing the fluorescence quenching mechanism and thermodynamics.The results showed that with the decreasing molecular weight of cellulose,the inhibition to both amylase activities increased.When the additional concentration was 3.0%,SC showed the maximum inhibition rate of α-amylase and amyloglucosidase activities,which were 30.8% and5.8%,respectively.The presence of NC,MC and SC changed the conformation of amyloglucosidase,and reduced the hydrophobicity around Tyr and Trp residues.NC,MC,and SC are bound to α-amylase by van der Waals force or hydrogen bonding force,and the binding process is exothermic.For amyloglucosidase,it binds to cellulose by hydrophobic interactions.In addition,the binding affinity of cellulose toα-amylase or amyloglucosidase increased with the decrease of molecular weight,and the fluorescence quenching intensity of amyloglucosidase was higher than that of α-amylase with the smaller molecular weight of cellulose.5.The changes of apparent viscosity and dynamic rheological properties of milk with 0.2 %,0.4 %,0.6 % and 0.8 % cellulose of different molecular weights were measured.The results showed that low molecular weight cellulose had the smallest increase in the apparent viscosity of milk.Under different addition levels,NC and SC made the milk exhibit viscosity characteristics.When the MC concentration reached0.8 %,milk showed solid-like properties.