Effect Of Annealing On Physicochemical Properties Of Rice Starch And Quality Of Rice Noodles

Rice is an important food crop in China.Rice noodles made with rice as raw material has become an indispensable food for breakfast or dinner,and has a good market prospect.With the improvement of living standards,people not only have higher requirements on the color,aroma,taste and nutritional value of rice noodles,but also have higher requirements on the quality of rice noodles,such as viscoelastic,ductile and elastic feeling.How to improve the quality of rice noodles is the long-term goal of food science and technology workers.It has been found that annealing starch(starch treated with excessive water > 65% or equilibrium water 40% ~ 55%,with temperature higher than glass transition temperature and lower than gelatinization initial temperature for a period of time)can significantly change the properties of starch.The dry base content of starch in rice is about 85%.If annealing treatment is adopted,the characteristics of rice starch may be significantly changed,and the quality of rice noodles made from rice may be significantly improved.Using rice as raw material and adopting annealing treatment and modification technology,this paper studied the technological conditions of annealing treatment to improve the quality of rice flour,and investigated the influence of annealing treatment on the physicochemical properties of starch in rice.The correlation between starch and rice flour quality before and after toughening was further studied.The main results are as follows:1.The effect of annealing on the quality of rice noodles and the optimization of technical parameters of annealing treatment.Based on the sensory quality index and tensile strength of rice flour,the effects of single factor(moisture content,time and temperature)of annealing on the quality characteristics of rice noodles were studied.On this basis,the technical parameters of annealing for rice noodles were optimized by response surface regression method.The results of single factor study show that: With the increase of water content,time and temperature,the maximum tensile resistance and sensory score of rice noodles increased first and then decreased.Response surface regression analysis showed that water content,annealing time and temperature all had significant effects on the tensile properties of rice noodles(P<0.01).The main and secondary factors affecting the maximum tensile resistance of rice noodles were annealing time>annealing temperature>water content of rice flour.Temperature and time of annealing had a significant effect on sensory score of rice flour,but water content of annealing had no significant effect on sensory score of rice noodles.The main and secondary factors affecting the sensory score of rice noodles after annealing were: annealing temperature>annealing time>moisture content of rice.The optimum toughening parameters were obtained by response surface test: moisture content 54.88%,time 22.16 h,temperature 56.94 C.Under these conditions,the maximum tensile resistance was 125.42 g,and the sensory score was 84.11.2.Effect of annealing on physicochemical properties of rice starch.On the basis of the previous chapter,in order to further verify the effect of annealing on improving the quality of rice noodles,this chapter selects two varieties of rice,Yuchi and Jinyou,which are quite different in amylose content as raw materials,and studies amylose content,dissolution rate and swelling power,gelatinization property,rheological property,surface microstructure,whiteness and gel properties of rice after annealing.The results are as follows:(1)After annealing,the content of amylose increased,the solubility and the swelling power decreased.(2)After annealing,the peak viscosity,Valley viscosity,attenuation value,minimum viscosity and retrogradation value of rice starch decreased significantly,and gelatinization temperature increased.(3)After annealing,the surface microstructure of starch did not change significantly,and the starch structure remained intact,which was conducive to rice flour processing.(4)The apparent viscosity and shear stress of annealed rice starch were higher than those of untreated starch,which indicated that annealed rice enhanced the network structure of the blending system.At the same frequency,the storage modulus of toughened rice starch is higher than that of untreated rice starch,and the loss modulus is lower than that of untreated rice starch.It shows that annealing enhances the solid elastic properties of starch,reduces the viscous properties,and makes the elastic properties predominate.(5)The whiteness of starch decreased after annealing.(6)The hardness and elasticity of starch gel increased significantly after annealing,but the adhesion and cohesion decreased.3.Analysis of correlation between physicochemical properties of rice starch and quality of rice noodles before and after annealing.Based on the study of physicochemical properties of rice starch from Yuchi and Jinyou varieties after annealing,the product characteristics(texture quality,sensory quality,stretching quality and cooking quality)of rice noodles from Yuchi and Jinyou varieties before and after annealing were further discussed,and the correlation between the properties of rice starch before and after annealing and the quality of rice noodles was analyzed.The results showed that amylose content,dissolution rate,swelling power,gelatinization properties,gel properties and rheological properties of rice starch were significantly related to the quality of rice noodles.Annealing improves amylose content of rice starch,decreases solubility,swelling force,peak viscosity,grain value viscosity,attenuation value,final viscosity and retrogradation value,and enhances the elasticity of colloid,thus improving the quality of rice noodles.It further shows that the physicochemical properties of rice starch determine the quality of rice flour.Annealing is directly effective to improve the quality of rice noodles.