TOMATO JUICE-BASED BEVERAGE:
RELAXATION TIME ANALYSIS
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TOMATO JUICE-BASED BEVERAGE: RELAXATION TIME ANALYSIS |
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The rheology of a tomato juice-based beverage was measured for a range of
strains and frequencies in a 1 mm diameter tube at 22°C. Plots of the viscous and elastic
stress vs. strain at 2 Hz show a critical strain = 0.14 and an elastic yield stress of
0.071 Pascal. Based on these values, a microstructure relaxation time can be
calculated[1],
A critical strain well below one indicates that Tm is near the longest relaxation time of the spectrum [1]. The higher critical strain that would mark the short relaxation time is not reached in these data, but since it must be greater than 10, the shortest relaxation time must be less than 0.008 sec. The viscosity and elasticity were measured for a range of frequencies from 0.02 to 6 Hz at a constant shear rate of 0.2/sec. From the shape of the curves it appears that this frequency range covers the major portion of the relaxation spectrum. The Maxwell relaxation time is calculated using,
At 0.5 Hz this gives TM = 0.35 sec. At 6 Hz it gives TM = 0.012 sec. These values are in within the range of relaxation times calculated from the yield strain.
[1] Thurston, G. B., Stress-strain relations for viscoelastic liquids, in Theoretical and Applied Rheology, ed. by P. Moldenaers and R. Keunings (Elsevier Science Publishers B. V. Belgium) 112- 114 (1992). *Ingredients: tomato juice, carrot juice, celery juice, beet juice, parsley juice, lettuce juice, watercress juice, spinach juice, salt, flavoring, potassium chloride, ascorbic acid, alpha tocopheryl acetate, citric acid, spice extract, malic acid, succinic acid.
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