Power-law foods in continuous coiled sterilisers

The heating, holding and cooling section of the high temperature region (T>100°C) of coiled UHT-sterilisers were simulated three-dimensionally to assess the impact of centrifugal and buoyant forces on viscous power-law food products. For a wide range of curvature (De=0–500), heat transfer, lethality development and thiamine concentration were analysed. Curvature and pseudoplasticity substantially increase heat transfer and render the axial velocity profile more uniform. As a result, processing times in heater, holder and cooler can be shorter, thus greatly improving thiamine retention. Significant lethality accumulated in the heating section, but the cooling section contributed very little to product sterility. Buoyant forces were shown to be of minor importance in coiled steriliser flow at the current process conditions.