Energy consumption in batch thermal processing: model development and validation

Thermal processing is an important method of food preservation in the manufacture of canned foods, retortable pouches, trays and bowls (retortable shelf-stable foods).The aim of this research was to develop a mathematical model to estimate total and transient energy consumption during the heat processing of retortable shelf-stable foods.The transient energy balance for a system defined as the steam and its water condensate in the retort requires no work term. The heat transfer terms include radiation and convection to the cook room environment, and heat transfer to the food in the cans. Mass and energy balance equations for the system were solved simultaneously, and the equation describing heat transfer in the food material was solved numerically using an explicit finite difference technique. Correlations valid in the range of interest (100 °C through 140 °C) were utilized to estimate the thermodynamic properties of steam, condensate, and food product.Depending upon selected conditions, retort insulation will account for a 15–25% energy reduction. In addition, initial temperature could reduce the peak energy demand in the order of 25–35%.These models should be useful in searching for optimum scheduling of retort battery operation in the canning plant, as well as in the optimising process conditions, to minimize energy consumption.