FLOW BEHAVIOUR OF TOMATO KETCHUPS

The flow behaviour of 13 tomato ketchups was characterized using a coaxial cylinder viscosimeter. Power law values for the flow behaviour index n averaged 0.35 ± 0.016 which indicated the pseudoplastic nature of ketchups. The consistency coefficient K values for ketchups depended more on temperature, pectin and pulp contents than on total solids. Activation energy (Ea) values for flow of ketchups varied from 1.99 to 4.88 kcal/mole and were significantly related with pectin contents. The Casson's yield values for ketchups showed a significant correlation with pectin contents. Michaels and Bolger model parameters showed that much greater forces were involved in the breaking of network structure and aggregates in ketchups than needed for flow. Multiple regressions of K and apparent viscosity on pectin and pulp contents of ketchups were highly significant.