CEIC2001_2019_T1_Exam 1.pdf - Question 1(6 marks The effect...

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1 Question 1 (6 marks) The effect of two fat replacers (xanthan gum and Reihan seed gum) on the rheological properties of low-calorie peanut butter were analyzed using a controlled stress Bohlin CVO rheometer (Bohlin Instruments Inc., UK) equipped with a 15 mm parallel plate measuring system and 1.5 mm gap. The peanut butter samples were loaded onto the rheometer and the rheometer’s plate was slowly moved down to the specified measuring position. Any excess sample was trimmed off with a spatula. The following data was obtained from the analysis. Data for peanut butter modified with Reihan seed gum Shear Rate γ (s -1 ) Shear Stress τ (Pa) 0 41 0.1 47 0.5 55 1 61 5 89 10 112 50 213 100 293 500 651 Data for peanut butter modified with xantham gum Shear Rate γ (s -1 ) Shear Stress τ (Pa) 0 41 0.1 44 0.5 48 1 51 5 63 10 73 50 112 100 141 500 265 (a) What type of flow behavior is exhibited by the two peanut butter samples? Is this an ideal flow behavior for peanut butter? Justify your answers in 100 words or less. (b) Use the logarithmic graph paper approach to determine the dynamic viscosity and apparent viscosity of the more viscous peanut butter sample at shear rate of 1 s -1 .
2 Question 2 (2 marks) The figure below shows a 2 mm diameter tube dipped into a liquid bath. How high would the liquid raise in the tube (i.e. what is the value of H), if the value of the angle θ is 45°, and the surface tension and density of the liquid are 0.073 N m -1 and 998 kgm -3 respectively?

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