Effect Of Konjac Glucomannan On Physicochemical And Digestibility Properties Of Corn Starch

Starch is a kind of renewable natural polymer which is widely used in the food industry due to its good gelling and thickening properties.However,natural starch usually has the disadvantages of aging,instability under shear and acid conditions and the higher glycemic index.Hydrocolloids are often used to change the functional properties of starch,make up for the deficiency of natural starch and improve the processing performance due to their thickening and water absorption properties.Moreover,the digestibility of starch could be decreased with the addition of hydrocolloids.In the present study,konjac glucomannan(KGM)with different molecular weight(Mw)was blended with corn starch(CS)to explore the effect of KGM on the physicochemical properties and digestibility of CS.The main contents and conclusions are as follows:1.KGM was degraded by the high pressure homogeneous,and the Mw of the degradation products detected by high performance gel permeation chromatography-multiangle laser light scattering(HPGPC-MALLS)were 1.37x106,9.51x105,8.79x105,7.58x105 and 5.97x105 g/moL respectivly.The water sbsorbtion ability and viscosity of KGM were decreased with the decrease Mw of KGM.2.The addition of KGM increased the gelatinization temperature of CS,reduced the leakage of amylose during gelatinization,and decreased the mobility of water molecules in the starch system,which exhibited a Mw dependence.The results of freeze-thaw stability experiments showed that the syneresis of CS-KGM mixtures decreased compared with the CS alone,indicating that KGM increased the freeze-thaw stability of CS.The results of differential scanning calorimetry(DSC)and X-ray diffraction indicate that KGM can effectively inhibit the aging of CS,and the effect of inhibition was more significant with the increase of KGM Mw.3.The results of static rheological experiment showed that the CS-KGM mixtures are pseudoplastic fluids,and the pseudoplasticity of the system increased with the increase of Mw of KGM.The results of dynamic rheological showed that the CS and CS-KGM mixtures are classified as typical weak gel,and the storage modulus(G’)and loss modulus(G")of the CS increased with the addition of KGM,indicating KGM could improve the viscoelasticity of CS.4.The effects of KGM on the digestibility of corn starch were studied from the aspects of in vitro digestion and amylase.The results showed that the hydrolysis rate and degree of CS were reduced and the glycemic index of CS were decreased with the addition of KGM.And the effect of KGM on the hydrolysis of CS was more significant with the increase of KGM Mw.KGM could also interact with amylase to inhibit amylase activity.