Mechanical tensile and fracture test were used in this study for assessing textural properties of five Thai rice noodles having the different levels of substituted tapioca flour (0%, 10%, 20%, 30% and 40% of composite rice flour and tapioca flour). Before testing tensile measurement, all specimens were shaped like dumbbell. The results showed that the maximum force, the extension and the total work significantly decreased from 0.55 to 0.43 N, 82.3 to 59.4 mm, and 0.030 to 0.017 J, respectively, when rice noodles contained tapioca flour 0% up to 40%. For fracture measurement, a single-edge-notched test, the results showed a similar pattern to tensile test. Adding the tapioca flour up to 40% decreased the maximum force, the extension and the total work from 0.8 to 0.6 N, 54.1 to 32.2 mm and 0.042 to 0.025 J, respectively. When correlated with sensory hardness, the maximum tensile force and maximum fracture force, respectively, gave a good correlation of 0.77 (p < 0.05) and 0.90 (p < 0.05). The relationship between maximum force and sensory hardness can be explained by the quadratic polynomial equation having an R2 greater than 0.9.
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