Effects Of Rice Protein Hydrolysates On Physicochemical Properties And In Vitro Digestibility Of Wheat Starch

Protein is present in foods rich in starch and is an important component affecting starch digestion.Protein hydrolysates have a greater effect on starch digestibility and glucose response than those of natural proteins,and the effects are different depending on the degree of enzymatic hydrolysis.In recent years,the modification effect of ultra-high pressure(UHP)technology on food functional characteristics has attracted wide attention.Ultra-high pressure treatment can lead to the destruction and formation of non-covalent bonds,conformational changes and phase transitions of biological macromolecules,thus further changing their physical and chemical properties and functional properties.In this study,wheat starch(WS)and rice protein hydrolysates(RPH)were used as research objects.Firstly,the effects of different degrees of hydrolysis and different amount of rice protein hydrolysates on physicochemical properties and in vitro digestibility of wheat starch were studied,and the optimal amount of RPH was determined according to the results of WS/RPH complexes in vitro digestibility.Secondly,the effects of ultra-high pressure treatment on the physicochemical properties and in vitro digestibility of the complex system were studied,and the mechanism was discussed.Finally,RPH was used to replace wheat all-purpose flour with different proportions to prepare low digestibility noodles.The main research contents and conclusions are as follows:1.RPH2 and RPH4 were prepared by alkaline protease and dispase with hydrolysis degrees of 10% and 14%,respectively.The results of sodium dodecyl sulfatepolyacrylamide gel electrophoresis(SDS-PAGE)showed that compared with the tight molecular structure of the original protein,the structure of RPH became loose,and the degree of looseness of RPH4 was greater than that of RPH2.2.RPH limited the hydration expansion of starch,increased the gelatinization temperature and decreased the gelatinization enthalpy.RPH altered the distribution of water in the complexes,resulting in changes in the gel network.Adding RPH could effectively slow down the starch digestion rate.Compared with WS,the contents of slow digestible starch and resistant starch in WS-12%RPH4 complexes increased from 31.4% and 36.1% to 33.3% and 46.7%,respectively.3.After 350 MPa pressure condition and retrogradation treatment,in the complex system,the starch molecule order is increased,the co-crystallization phenomenon is more extensive,the relaxation time is shortened,the water fluidity is weakened,the gelatinization time is delayed,the peak viscosity is significantly reduced,the viscoelasticity is increased,the gel network structure is increased,the cross-section cavity is smaller,and the structure is tighter.Compared with WS-12%RPH4,the contents of slow digestible starch and resistant starch in WS-12%RPH4-350 increased from 12.4% and 45.0% to 14.9% and 51.0%,respectively.4.Noodles were made by replacing 0%,8%,12% and 20% all-purpose wheat flour with RPH4 of corresponding quality.With the increase of substitution degree,the color of mixed noodles became dark,the cooking characteristics became worse,the texture characteristics changed,the sensory evaluation score decreased,and the in vitro digestibility decreased significantly.