Aseptic Processing of a Low-acid Multiphase Food Product using a Continuous Flow Microwave System.

Abstract

Continuous flow microwave heating is an emerging technology in the food industry with a potential to replace the conventional retort process for viscous and pumpable food products. Aseptic processing of a low-acid multiphase food product using continuous flow microwave heating system can combine the advantages of an aseptic process along with those of microwave heating.

The main objective of this research was to develop a systematic approach for biological validation of aseptic processing of salsa con queso products using a continuous flow microwave system operating at 915 MHz. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) and compared with the dielectric properties measured by the conventional approach (under static conditions). The results suggested that, for a multiphase product, dielectric properties measured under continuous flow conditions should be used for designing a continuous flow microwave heating system.

Thermophysical and dielectric properties of salsa con queso and its vegetable ingredients (tomatoes, bell peppers, jalapeno peppers, and onions) were measured at a temperature range of 20 to 130 C. The results were used to fabricate design particles from PP (polypropylene) and PMP (polymethylpentene) using a custom developed CPD (Conservative Particle Design) software. These particles could be used as thermo-sensitive implant carriers for bacterial spores in biological validation of a multiphase aseptic process.

Salsa con queso was processed in a 5 kW microwave unit with a specially designed focused applicator. The temperature profiles at the outlet during processing of salsa con queso in the 5 kW microwave unit showed a narrow temperature distribution between the center and the wall of the tube. Thus, continuous flow microwave heating could overcome the problems (degradation of color, flavor, texture, and nutrients) associated with the wider temperature distribution between the center and the wall in a conventional heating system.

The results from this study will assist processors in designing a safe process for aseptic processing of salsa con queso using a continuous flow microwave system. However, further research is required to biologically validate such a process as the final step in establishing an aseptic process for salsa con queso using a continuous flow microwave system.