Study On Physicochemical Properties Of Extruded Starch-Protein Complex And Its Effect On Dough

Extrusion is a continuous cooking process under controlled conditions that can alter the physicochemical and rheological properties of starch.At present,there are few studies on the addition of extruded starch-protein complexes to pasta products.Most studies have focused on the effect of extruded starch or whole flour to pasta products.In this paper,yam starch and soy protein isolate were used as raw materials,and the effect of extruded starch-protein complex on dough quality was studied by twin-screw extrusion technology.The changes of texture,rheological properties and microstructure of dough with the addition of extruded starch-protein complex were revealed.The main research content and conclusions included the following aspects:1.The effect of different extrusion temperatures on the physicochemical properties of yam flour and starch.This chapter mainly studies the effect of extrusion treatment on the physicochemical properties and in vitro digestibility of yam flour and starch.The extrusion conditions were selected as follows: the moisture content of the material was 30%,the screw speed was 180 rpm,and the screw temperatures were 90,110,and 130 °C,respectively.The results showed that the yam flour and starch were degraded and severely damaged after extrusion treatment.And the amorphous region of starch was destroyed.The crystallinity of yam flour decreased from 38.9 to 23.0%,and the crystallinity of yam starch decreased by 20.7%.The solubility of yam flour and starch increased,and the swelling power and gelatinization enthalpy decreased.The content of slowly digestible starch was increased and the resistant starch content was decreased.The content of slowly digestible starch yam starch after extrusion treatment was higher than that of yam flour.When the screw temperature was 90 ?,the slowly digestible starch content of the yam flour and starch extruded was the highest,which were 34.86% and34.74%,respectively.2.The effect of different additions of soy protein isolate on the physical and chemical properties of extruded yam starch-soy protein isolate complexSoy protein isolate was mixed with yam starch at addition amount of 0%,5%,10%,15%,and 20% for extrusion treatment.The extruded starch-protein complex was characterized and analyzed.The results showed that the crystal structure of the extruded starch-protein complex was V-shaped with the addition of soy protein isolate.The crystallinity of the complex increased,with a maximum value of 24.8%.The gelatinization enthalpy of the complex decreased with the increase of soy protein isolate content.The low addition amount of soy protein isolate could enhance the viscoelasticity of the complex.It indicated that soy protein isolate had the potential to enhance the gel network structure of the system.The content of resistant starch increased and the content of rapidly digestible starch decreased in the complex.The content of slowly digestible starch and resistant starch in the complex increased and reached the maximum at 20%soy protein isolate.According to the comprehensive consideration of the physicochemical properties and in vitro digestibility of the complex,the extruded starch-protein complex with soy protein isolate content of 10% was selected to be added to the dough preparation.3.The effect of different replacement amounts of extruded yam starch-soy protein isolate complex on dough qualityThe extruded starch-protein complex was mixed with wheat flour at 10% and 20%replacement amount to make dough,and the quality and microstructure of the dough with the addition of extruded flour was studied.The results showed that when the extruded flour partially replaced wheat flour,it was found that the closely bound water content of the dough increased from 12.39% to 14.18%,and the dough fluidity was weakened.The microstructure of the dough all changed significantly,and the continuity of the gluten network structure decreased.Under the condition of the same substitution amount,compared with the addition of extruded yam starch,the dough hardness,elasticity and chewiness of extruded starch-protein composite flour partially substituted for wheat flour increased.