Safety and Quality of Microwave Food Sterilization

Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853

Performing Department
BIOLOGICAL & ENVIRONMENTAL ENGINEERING

Non Technical Summary
Food quality can be potentially increased by sterilizing it rapidly and uniformly, as compared to canning. The project addresses the complexities of such a microwave sterilization process.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
501	5010	2020	100%

Knowledge Area
501 - New and Improved Food Processing Technologies;

Subject Of Investigation
5010 - Food;

Field Of Science
2020 - Engineering;

Goals / Objectives
1. To describe the microwave energy absorption, temperature rise in the food, and its sterilization and cook values by detailed computations. 2. To measure experimental sterilization and cook-values by following the concentration of a marker chemical and compare with computations in step 1 for model validation. 3. To study the effect of change in frequency to 915 MHz ( as opposed to 2450 MHz) on heating uniformity and cold point locations. 4. To optimize the shape, size, and food properties for heating uniformity.

Project Methods
Governing equations for electromagnetics and heat transfer will be coupled and solved numerically to obtain temperature-time histories at various food locations. Sterilization and cook values will be computed from this data. In an indirect experimental measure of sterilization, ribose will be added to food and the concentration of a marker chemical that is formed as a first order reaction from ribose will be measured and related to sterilization. Comparisons of the uniformity of heating between 915 MHz and 2450 MHz frequency will be made. Effect of food geometry and composition on the heating uniformity will be checked for various food shapes and sizes using the model. Validation (for the FDA) of microwave sterilization process will be addressed.

Progress 10/01/99 to 09/30/02

Outputs
Sterilization of solid foods using microwave power was studied using numerical modeling and specialized experimental verification. Maxwell's equations and the heat conduction equation were coupled using two separate finite-element programs and specially written modules to couple the programs. Spatial distributions of thermal-time, representing sterilization, were calculated from time-temperature history and first order kinetics. Experimentally, concentrations of marker compounds formed during heating were measured and taken as indices of thermal-time. Experimental data on marker formation combined with numerical calculations provide an accurate and comprehensive picture of the sterilization process and represent a major step in establishing the efficacy of microwave sterilization processing. Unlike conventional sterilization, heating patterns can change qualitatively with geometry (shape and size) and properties (composition) of the food material, but optimal heating is possible by choosing suitable combinations of these factors. Combined with marker yield measurements, the numerical model can give comprehensive descriptions of the spatial time-temperature history, and thus can be used to verify the sterilization process. Role of the shape of the food and its properties in the optimization of the microwave sterilization process was demonstrated.

Impacts
The concepts developed in this project led to myself becoming a partner in the million dollar industry-university-government consortium that is developing microwave sterilization for commercial food processing. Over half a million dollar in this project is coming from the industry, showing their interest in this sterilization process. Our ideas of how the microwave absorption in the food changes as the product heats up and how modeling can be used to understand and optimize the process is central to this ongoing project.

Publications

Zhang, H. and A. K. Datta. 2001. Heating concentrations of microwaves in spherical and cylindrical foods. I: In Plane Waves. Accepted pending revisions in the Journal of Microwave Power and Electromagnetic Energy.
Zhang, H. and A. K. Datta. 2001. Heating concentrations of microwaves in spherical and cylindrical foods. II: In a cavity. Accepted pending revisions in the Journal of Microwave Power and Electromagnetic Energy.
Zhang, H. and A. K. Datta. 2001. Microwave power absorption in single and multi-component foods. Accepted pending revisions in the Transactions of the Institution of Chemical Engineers.

Progress 01/01/01 to 12/31/01

Outputs
Sterilization of solid foods using microwave power was studied using numerical modeling and specialized experimental verification. Maxwell's equations and the heat conduction equation were coupled using two separate finite-element programs and specially written modules to couple the programs. Spatial distributions of thermal-time, representing sterilization, were calculated from time-temperature history and first order kinetics. Experimentally, concentrations of marker compounds formed during heating were measured and taken as indices of thermal-time. Experimental data on marker formation combined with numerical calculations provide an accurate and comprehensive picture of the sterilization process and represent a major step in establishing the efficacy of microwave sterilization processing. Unlike conventional sterilization, heating patterns can change qualitatively with geometry (shape and size) and properties (composition) of the food material, but optimal heating is possible by choosing suitable combinations of these factors. Combined with marker yield measurements, the numerical model can give comprehensive descriptions of the spatial time-temperature history, and thus can be used to verify the sterilization process.

Impacts
The impact of this felt in the first comprehensive understanding of microwave sterilization processes that include state-of-the are computer modeling and experimentation. Microwave sterilization can provide better processed food quality than conventional sterilization.

Publications

Zhang, H., A. K. Datta, I. A. Taub and C. Doona. 2001. Electromagnetics, heat transfer, and thermokinetics in microwave sterilization. American Institute of Chemical Engineers Journal. 47(9):1957-1968. Datta, A. K. 2001. Integration of tools for computer-aided food process engineering. Invited speaker at the First International Workshop on Mathematical and Computing Technologies for Agro-Food Technologies, Barcelona, Spain, Nov. 26-27. Proceedings of the conference are being published.
Datta, A. K. 2001. Alternative Preservation Processes: Microwave. In Encyclopedia of Agricultural and Food Engineering. Marcel Dekker, Inc., New York.
Datta, A. K. and J. Rattray. 2001. Food process simulation. The Encyclopedia of Life Support Systems, EOLSS Publishers Co., Ltd., UK. Sastry, S. K. and A. K. Datta. 2001. Electrothermal processing. Presented in the Session on Emerging Technologies in Food Processing at the IFT Annual Meeting, New Orleans, Louisiana, June 23-27. Abstract no. 65-2.

Progress 01/01/00 to 12/31/00

Outputs
The amplitude of microwave power absorbed by foods in cavity heating are studied using numerical and experimental methods for single and two compartment arrangements. Maxwell's equations are solved numerically for foods in different shapes, sizes and having different dielectric properties heated a domestic oven. Relationships are developed to characterize the power absorption of foods as affected by their sizes and properties. Interestingly, foods with small loss factor may not absorb less power if the size is sufficiently large, while high loss foods usually absorb more power at small sizes. This is also true for the heating of multiple component materials which is proven both numerically and experimentally in this study.

Impacts
Critical factors for microwave sterilization (that provides improved quality) have been identified. In particular, knowledge of differential power absorption when heating multiple components will help design microwave sterilization processes with less trial and error.

Publications

Datta, A. K. and M. Davidson. 2000. Microwave sterilization: Kinetics, critical process factors and validation issues. Abstract no. 19-3, IFT Annual Meeting at Dallas, Texas, June 10-14.
Datta, A. K. 2000. Computer-aided engineering of microwave sterilization processes. Abstract no. 59-1, IFT Annual Meeting at Dallas, Texas, June 10-14.
Zhang, H. and A. K. Datta. 2000. Power absorption during microwave heating of single and multi-compartment foods. Abstract no. 74-1, IFT Annual Meeting at Dallas, Texas, June 10-14.