Sensitivity analysis of continuous ohmic heating process for multiphase foods

The process sensitivity analysis of continuous Ohmic heating process for soup products containing large particulates was performed by use of a validated computer modeling package to determine the critical control factors and their acceptable control ranges under given control targets. The major processing variables investigated included electrical conductivities of carrier fluid and particles, particle thermal diffusivity, surface heat transfer coefficient, particle size, particle concentration, flow rate, and initial product temperature. The response variables as the indicators of effects from processing variable deviations were the process temperatures and accumulated lethality values for both carrier fluid and particles at the end of holding tube. The results demonstrated that under giving base processing conditions with a control target process temperature of 133 °C (the carrier fluid temperature at the entrance of the holding tube or the end of heating tube), increasing carrier fluid electrical conductivity from 1.42 to 2.13 S/m at a reference temperature of 70 °C, particle size from 16 to 24 mm, and flow rate from 1600 to 2400 L/h could result in lower particle center temperature at the end of holding tube, while increasing particle electrical conductivity from 0.96 to 1.44 S/m at a reference temperature of 70 °C, thermal diffusivity from 1.16 × 10⁻⁷ to 1.74 × 10⁻⁷ m²/s, surface heat transfer coefficient from 112 to 168 W/°C/m², particle concentration from 52% to78%, and initial product temperature from 56 to 84 °C could generate higher particle center temperature. Within the variable deviation ranges investigated, the importance order of effects of major processing variables were determined with respect to the particle center temperatures, carrier fluid temperatures and accumulated lethality values. The acceptable deviation ranges were built up for six major processing variables under meeting the required target Fo (at the particle center) values. The information and knowledge obtained from this study can be useful for understanding how major processing variables of continuous Ohmic heating processing system affect the required process target variables and the methodology developed in this study can be further used as a protocol for both process establishment and optimization purposes.