Simulation and evaluation of aseptic particulate processing

David Scott Lineback, Purdue University

Abstract

Two phases of research were conducted in an attempt to solve the problems associated with aseptic particulate processing. The first phase of research focused on developing a thermal processing indicator that can be used to monitor particle lethality in a continuous system. The second phase of research involved experimental and computer simulation studies of a simultaneous steam-microwave particulate processing system. Preliminary studies on horseradish peroxidase were conducted to determine if post-processing regeneration occurred. Horseradish peroxidase samples were processed in an oil bath and in a microwave oven, then stored at 0$\sp\circ$C for 48 hours to monitor for regeneration. During the post-processing storage period 3.2-5.8% regeneration occurred. Horseradish peroxidase was successfully immobilized in an alginate cube. Unprocessed cubes were exposed to continuously flowing water to investigate potential diffusion loss of peroxidase during processing. Diffusion studies indicated that 4-11% of native (unprocessed) peroxidase activity could be lost during a 5 minute exposure to water depending on the cube size and water temperature. Thermal inactivation kinetics of horseradish peroxidase in alginate mix and gelled alginate cubes were also studied. The percent heat stable enzyme and z-value decreased from 68.2% to 5.5% and increased from 29.9 to 40.5$\sp\circ$C, respectively. Gelled alginate cubes containing peroxidase were successfully used to predict thermal processes in which 50-82% of the original peroxidase was inactivated. Evidence of peroxidase diffusion was not observed in the validation studies. A three-dimensional finite difference program accurately modeled steam heating and steam-microwave heating. The program underestimated the center temperature of the potato cube after the microwave power was turned off. This was due to the fact that the program did not account for the internal pressure in the cube. Program simulations revealed interesting trends concerning fundamental heat transfer theory in a steam-microwave process. The final test was to monitor ascorbic acid destruction as a quality indicator for potato cubes processed in a steam-microwave retort and a conventional retort. Ascorbic acid retention was 18.7% greater for the product processed in the steam-microwave process.

Degree

Ph.D.

Advisors

Nelson, Purdue University.

Subject Area

Food science

COinS