Effect Of Rice Protein Hydrolysate On Wheat Starch And Dough

In this paper,rice protein(RP),wheat starch and wheat flour were used as the main materials and among the rice protein hydrolysate(RPH)produced using three proteolytic enzymes(alcalase,papain and protamex)to study the effects of RPH on the gelatinization,retrogradation and rheological properties of wheat starch,and further explore effect of RPH on wheat dough properties and gluten structure.The main research results are as follows:(1)The effect of different RPH on retrogradation of wheat starch was investigated among the RPH produced using three proteolytic enzymes(alcalase,papain and protamex).The results indicated that wheat starch incorporated protamex-hydrolyzed rice protein which hydrolyzed for 2 h(PRPH-2)exhibited the lowest gel hardness.Therefore,the rice protein hydrolyzed by protamex at 2 h showed the highest anti-retrogradation activity for wheat starch.(2)Differential scanning calorimetry(DSC),rapid visco-analyzer(RVA)and X-ray diffraction(XRD)were applied to determine the difference of thermal properties,pasting properties,rheological properties,X-ray diffraction and freeze-thaw stability on adding rice protein to wheat starch.The results showed that adding rice protein to wheat starch made the gelatinization temperature increased,and the gelatinization enthalpy decreased.With the increase of rice protein content,the peak viscosity,trough viscosity,breakdown value final viscosity,setback value of wheat starch decreased and the gelatinization temperature increased.Rice protein inhibited the dissolution of crystals in starch.And the addition of rice protein reduced the storage modulus and lost modulus of wheat starch gel,the gel strength was weaker,and the freeze-thaw stability was reduced.(3)The effect of PRPH-2 on retrogradation of wheat starch(WS)was investigated by thermal properties,pasting properties,rheological properties and water migration on adding different ratios of PRPH-2 to wheat starch.The results showed that PRPH-2 addition significantly lowered peak viscosity,breakdown and setback values(P<0.05),whereas it increased pasting temperature of wheat starch.Compared with native wheat starch,the presence of PRPH-2 resulted in a decrease in the storage modulus(G')and an increase in the loss tangent(tan ?),which meant the short-term retrogradation of wheat starch was inhibited.In addition,PRPH-2 significantly decreased the retrogradation enthalpy and the crystallization rate constant(k).Scanning electron microscopy(SEM)analysis results showed that the addition of PRPH-2 made the starch gel network structure more compact.The water distribution results demonstrated that PRPH-2 could promote the mobility of water molecules in WS gel led to retard the long-term retrogradation of wheat starch.(4)The effects of RP and PRPH-2 on the properties of wheat dough were studied by Mixolab mixer and tensile tester.The results showed that with the addition of RP and PRPH-2,the water absorption rate gradually increased,but setback values gradually decreased.Compared with the control,the presence of RP resulted in an increase development time,stability time,and the degree of softness,whereas its decreased adding PRPH-2.Meanwhile,the tensile resistance and the degree of stretching are also reduced.Furthermore,the wet gluten content reduced significantly(P<0.05)and the SH-free and S-S contents increased.