The effect of two different hydrocolloids on rheological properties and sensory
quality of tomato ketchup during storage was studied. The starch was add to
tomato ketchup at level of 0 ,1 ,2 and 3% while pectin was add at level 0.5 and
1%. Tomato ketchup was stored at room temperature for six months.
The rheological behavior of tomato ketchup samples contained different
ratios of hydrocolloids were measured in shear rate range 0.0 to 100 s-1 and
studied at a wide range of temperatures (5 - 75 °C) using a Brookfield Digital
Viscometer. The results indicated that these tomato ketchups behave as non-
Newtonian fluids (pseudoplastic) and have a definite yield stress. Higher
significant correlation was found between the viscosity and temperature. The
viscosity decreased with increasing in the temperature. All hydrocolloids
increased consistency of tomato ketchup. With increasing storage period,
viscosity of tomato ketchup decreased. The water separation as important
sensory attribute decreased with the addition level of hydrocolloid and increased
with increasing storage duration. The effect of temperature on their viscosity
can be described by means of an Arrhenius-type equation. The activation energy
for viscous flow depends on the chemical composition; the activation energy
decreased with increasing hydrocolloids addition. Sensory tests for tomato
ketchups were done during storage and the results indicated that the
hydrocolloid addition improved the quality of tomato ketchup in zero time and
during storage period. |
