Preparation,structure,properties And Application Of Wheat Gluten-rice Starch Model Dough

Rice is one of the staple foods of human beings,and its main components are starch and protein.However,due to the lack of gluten,rice flour can not form a viscoelastic network structure,which limits its wide application in food industry.In this thesis,the model dough samples were prepared by mixing wheat gluten with rice starch according to different ratios(0:100,6:94,8:92,10:90,12:88 and 14:86,w/w).The physicochemical and structural properties of the model dough were researched.Moreover,the effects of freeze-thaw cycles,sodium chloride and freezing rate on the water distribution,physicochemical and structural properties of the model dough were investigated.In addition,the quality,physicochemical and retrogradation properties and in vitro digestibility of starch in steamed rice cake made from wheat gluten-rice starch model dough were explored.Firstly,the physicochemical and structural properties of the dough were studied.The results showed that with the increase of gluten content,the water absorption,development time,stability time increased,and the degree of softening decreased.The extensograph,texture profile analysis(TPA)and rheology results showed that gluten significantly enhanced the viscoelasticity and extensibility of the model dough.Moreover,the gluten could increase the swelling power and thermal stability,decrease the water solubility and thermodynamic enthalpy.The results of protein aggregation behavior indicated that the gluten promoted the conversion of free sulfhydryl groups to disulfide bonds,which was beneficial to the formation of the uniform and compact gluten network.Secondly,the effects of freeze-thaw cycles on the water state,rheological and structural properties of the model dough(wheat gluten:rice starch=12:88,w/w)were investigated.The results showed that the repeated freeze-thaw treatment destroyed the model dough structure,so water loss rate,syneresis rate,freezable water content,water activity and mobility of the model dough increased.And the water loss inhibited the gelatinization behavior of rice starch.Meanwhile,with the increase of freeze-thaw cycles,the hardness of the model dough was increased,the viscoelasticity was reduced,the gluten network became uneven and loose,and starch granules would leach from the matrix.After that,the effects of sodium chloride(0,1,2,3%,w/w)and freezing rate(4.05,9.66,15.86 ?/h)on the water state,rheological and structural properties of the model dough(wheat gluten:rice starch=12:88,w/w)were studied.The results showed that the storage modulus(G'),loss modulus(G'),water content and thermal stability of the model dough were significantly improved with the increase of freezing rate.Meanwhile,the addition of NaCl could significantly improve the freezing stability of the model dough.The results of LF-NMR and freezable water content indicated that the high-speed frozen(15.86 ?/h)model dough containing 2% NaCl showed the highest bound water content,the lowest freezable water content and free water content.Moreover,the free sulfhydryl and ?-turn content decreased significantly,and the ?-sheet and ?-helix content increased significantly with the increase of NaCl content(? 2%)and freezing rate,which was conducive to maintain the integrity of the frozen dough network structure.Finally,the model dough samples made by mixing wheat gluten and rice starch(0:100,6:94,8:92,10:90,12:88 and 14:86,w/w)were cooked into steamed rice cakes,and the quality,retrogradation properties,in vitro digestibility of starch were studied.The results showed that as the amount of gluten increased,the hardness and chewiness of the steamed rice cake decreased,the springiness,cohesiveness and resilience increased,and the continuous network structure formed,which could increase the gas retention ability and the specific volume of steamed rice cake.Meanwhile,the gluten not only promoted the formation of a tight gluten network,but also competed with rice starch for the available water,thus limiting the hydrolysis of rice starch and reducing the content of rapidly digestible starch(RDS),increasing the content of slowly digestible starch(SDS)and resistant starch(RS).Moreover,the continuous gluten network limited the migration of water and starch molecules in the steamed rice cake during storage,thus inhibiting the retrogradation of steamed rice cake.In summray,this dissertation showed that the gluten could significantly improve the quality of model dough and steamed rice cake.Adding NaCl and increasing the freezing rate could improve the quality of frozen dough.These results provided a theoretical basis for the improvement of rice products and frozen dough.