Advantages Of Aseptic Processing

Introduction: Retorts, batch kettles, and aseptic processes are a few thermal techniques used within industrial food production. Overall, aseptic processing is a superior method for fluid systems[1]. Aseptic processing offers shorter processing times, higher production rates, and better product quality[1-3]. Within aseptic processing, there are several different forms of heat transfer, including direct, indirect, ohmic, and microwave heat exchange[4]. Microwave thermal technology offers more consistent temperature profiles across fluid systems because of dielectric properties of a fluid[5-11]. Through testing of model fluids, temperature profiles were recorded at different velocities to compare the effects of dielectric properties[5-7].

When thermally processed, fluids exhibit irreversible changes like loss of texture, color, and nutrients in order to reach a desired level of sterility[1]. Added benefits of aseptic processing are shorter processing times, improved product quality, higher production rates, and reduced power requirements[1-3]. There are currently three main forms of heat exchange used in industry, which include direct, indirect, and ohmic[4]. Direct and indirect heat exchanges have added benefit of lower costs and versatility across different fluid systems[4]. Other advantages include: processing of viscous fluids, temperature control, rapid heating, and minimization of fouling[4]. Larger energy input is required because these systems heat through conduction and convection and can cause overheating of fluid products[5]. Microwave technology provides more consistent heating throughout the cross section of a fluid and therefore reduces overheating of

When a high frequency field is applied to an aseptic system, the fluid system is heated by vibrating the chemical bonds within a food product[13,14]. There are two different properties in dielectrics that affect thermal processes: dielectric constant and dielectric loss factor. The dielectric constant is the ability of a material to store electromagnetic energy and dielectric loss factor is a measure of how well a material can convert electromagnetic energy to heat[5-11]. Figure 2 shows how electromagnetic fields are applied across a cross section of a pipe due to the dielectric properties associated with the fluid[7]. Fluids with higher dielectric properties exhibit more consistent cross sectional profiles as shown in Figure 2[7]. In food processing, process equipment must be sterilized before product can be processed. To prevent under heating or overheating, sterilization solutions must have similar dielectric properties to that of the final products of a production line[6]. Figure 3 shows temperature profiles as a microwave system switches from sterilization solution to sweet potato puree product at three different positions in the pipe[6]. The fairly uniform line shown in Figure 3 correlates to an even temperature profile along the cross section during the switch to