Studies On Mechanical Properties And Texture Evaluation Of Vermicelli

Vermicelli is a traditional food in China, it is liked by all the people and has a broad market at home and abroad because of its features of compliant, smooth, refreshing, pleasant and better adsorption to taste. However, at present, the evaluation of vermicelli texture and quality depends mainly on the people’s sensory perception. There was no specific and quantifiable standard for some important indicators of flexibility, toughness and stickiness of vermicelli in a series of standards domestic. Nowadys, the study mostly located in those indexes such as broken rate and cooking loss, the study about rheological properties and texture evaluation of dry vermicelli are less at home and abroad. So to study the rheological properties and texture evaluation of vermicelli is necessary. It can provide a powerful foundation for the vermicelli’s production, processing and quality evaluation, also supply theory evidence for the development of standards.The best condition mechanical properties of dry and cooking vermicelli were optimized; Correlations about the mechanical properties of dry and cooking vermicelli were studied; Tensile, three-point bending and compressive rod post-buckling were adopted to establish the best method of vermicelli elastic modulus determination. The toughness determination by compressive rod post-buckling was established in this study. Main research results are showed as follows:The best conditon of TPA, loding-unloding, tensile, shearing test of dry vermicelli was studied in this paper. The results showed that the optimum test conditions were test speed of 0.5mm/s and 50% compression ratio for TPA test, and the cohesion, hardness and elasticity of vermicelli can be good performanced. By comparison of three methods(tensile, compressive and three-point-bending of loading-unloading method), the optimum test conditions obtained were as follows:test speed was 0.5mm/s both for three methods, tensile deformation was 1.5mm, amount of compression was 1.0mm and the mid-point deflection compression was 2.0mm;the compressive loading-unloading was the best method in the three methods; The optimum speed was 1.0mm/s for shearing test; The optimum speed is 0.5mm/s for tensile test.The toughness determination by compressive rod post-buckling was studied in this paper. The results showed that:The greater end bending angle, the toughness was better.The best conditon of TPA, loding-unloding, shearing, creep, stress relaxation test of cooking vermicelli were studied in this paper. The results showed that:the optimum conditions of TPA were 0.5mm/s of test speed and 50% of compression ratio; the optimum conditions of compression loading-unloading were 0.5mm/s of test speed and 1.6mm of amount of compression; The optimum speed was 0.5mm/s for shearing test; the optimum conditions of creep test were 1.5mm/s of test speed,5N of load and 40 seconds of creep time. Burger’s model was fitted cooking vermicelli creep data with fitting rate to 0.993,0.999 and 0.989 of samples A, B and C, respectively. The optimum conditions of stress relaxation test were 1.0mm/s of test speed,1.0mm of loading force and 20 seconds of relaxation time;Three elements Maxwell model was fitted relaxation curve with fitting rate to 0.946,0.962 and 0.923 of samples A, B and C, respectively.Correlations about the mechanical properties of dry and cooking vermicelli were studied in the paper. The results showed that:The hardness of dry vermicelli was greater, and chewiness was also higher; Cooking vermicelli had the greater adhesiveness when adhesion were stronger;The greater hardness, springiness and chewiness of dry vermicelli, the springiness of cooking vermicelli was higher, while the viscosity was smaller; When the most force of compression, tensile strength and tensile breaking force of dry vermicelli were greater, and the hardness, bite, adhesiveness of cooking vermicelli were also higher.Three methods were adopted to establish the best method of vermicelli elastic modulus determination in this study. The results showed that:the best test condition of tensile test is 0.5mm/s; three-point bending test is 0.5mm/s, span of 60 mm, mid-point deflection compression 1.0mm.;the compressive rod post-buckling test is 0.1mm/s test speed,100mm sample length and 20°rotational angle. Effects of water content of dry vermicelli on its elastic modulus were studied and revealed that the water content was negatively linear proportional to its elastic modulus.Comparison of three methods, the tensile test method is relatively smaller error, the sample is not strictly required.So, tensile test method is optimal. But there is the question gripping both ends of the point of fracture, so when the selected sample is relatively flat and uniform, the compressive rod post-buckling test method is optimal.9 kinds of vermicelli:Potato vermicelli, sweet potato vermicelli, taro silver vermicelli, mung bean vermicelli, vermicelli, tower vermicelli, triple powder vermicelli and sweet potato vermicelli, which elastic modulus deformation values by tensile are 1.419×109N/m2,1.571×109N/m2,1.472×109N/m2,1.449×109N/m2,1.531×109N/m2,2.14 2×109N/m2,1.942×109N/m2,2.267×109N/m2and 1.955×109N/m2 Therefore, the elastic modulus can be used to evaluate the quality of vermicelli.