Effect And Mechanism Of Pea Hull Nanocrystalline Cellulose On Digestion In Vitro Characteristics Of Corn Starch

Starch is an important carbohydrate,and its digestive characteristics are closely related to the level of blood sugar after meal.Controlling postprandial blood glucose by adjusting the digestive properties of starch is one of the effective means to prevent and treat type 2 diabetes.Nanocrystalline cellulose(NCC),a special dietary fiber,has the function of inhibiting starch digestion,but its mechanism of action is not yet clear.Based on this,this study was conducted to isolate and prepare NCC from pea hulls,evaluate the effect of NCC on the digestibility of corn starch,and analyze the molecular mechanism of NCC in regulating the digestibility of starch from the perspective of starch physicochemical properties and α-amylase activity.The main research contents and results were as follows:1.Preparation and characterization of pea hull NCC: The non-cellulose components such as hemicellulose and lignin were effectively removed by alkaline treatment,bleaching,acid hydrolysis and other purification processes.The NCC was rod-like,the length was 344.91 nm,the diameter was 22.20 nm,and the aspect ratio was 18.43.Compared with pea hull powder,the crystallinity(57.11%)of NCC was significantly increased,and the maximum thermal degradation temperature(263.94°C)was significantly decreased.The Zeta potential value of NCC solution was-28.67 m V,and the dispersion stability was good.2.Study on the effect of NCC on the structure and properties of corn starch: NCC increased the viscosity,viscoelasticity,short-range order and crystallinity of gelatinized starch;NCC induced the formation of dense,uniform and ordered network structure of starch gel.Density functional theory calculation demonstrated that NCC interacted with starch molecules by hydrogen bonding through surface hydroxyl groups;0.5～1.5% NCC significantly inhibited the in vitro digestion rate and degree of corn starch,and the inhibition was concentration-dependent.Pearson correlation analysis and principal component analysis showed that the viscosity,viscoelasticity and short-range order of starch were closely related to the degree and rate of digestion.3.Study on the interaction between NCC and α-amylase: By interacting with starch,NCC reduced the surface hydrophobicity of α-amylase,caused the static quenching of the endogenous fluorescence of α-amylase,and promoted the transformation of β-folding intoα-helix and β-angle;Molecular simulations predicted that NCC bond to amino acid residues(Trp 58,Trp 59,and Tyr 62)at the entrance to the active pocket of α-amylase through hydrogen bonding and van der Waals forces,which prevented starch from entering the catalytic site of α-amylase and thus inhibits α-amylase activity.In conclusion,NCC could improve the structure and physicochemical properties of corn starch and inhibit the activity of α-amylase,thereby reducing the digestibility of corn starch.The results of this study provide theoretical reference and technical support for the analysis of the regulatory mechanism of digestibility of starch-based foods and the development of new low GI foods.