Evaluation of methods to control oxygen and water vapor within simulated food package environments
Abstract
Meals-ready-to-eat (MRE) packaging is being used by NASA to control oxygen and water vapor permeation for foods sent to space missions. In order to reduce the weight of packaging trash and to withstand the processing techniques applied, NASA is looking for better packaging systems which would meet these requirements and still have the current barrier properties. A proposed solution involves packaging foods in lightweight materials which are insufficient to provide oxygen and moisture barriers, but are over-packed in a material which provides the barrier properties. The objectives of this project were to (a) Control oxygen concentration using certain electrochemical reactions; and (b) Control water vapor concentration using a peltier cooler inside a simulated package environment. Oxygen permeability of various polymer materials was determined by following standard ASTM D3985 procedure, and Clark electrodes made of gold leaf were used to reduce permeated and free oxygen electrochemically to water at 0.8 V. The electrodes were able to reduce the oxygen concentration by approximately 40% in 24–30 hours. Water vapor permeability, measured using standard ASTM E96 procedure, was regulated within a closed chamber using saturated salt solutions and was later removed by peltier coolers. The peltier cooler condensed over 8 g/54 cm2day under 100% RH conditions in a 10 gallon glass fish tank. Mathematical models using MathCAD were also developed to assess the permeation, diffusion and solubility of water and oxygen in different polymers for long term space missions. From the experimental data it was observed that a minimum rate constant of 4.1*10-12sec-1 for oxygen removal must be achieved for meeting the NASA specifications of 0.06 cc/day.m2.atm for oxygen permeation in packaged foods. The rate of oxygen removal in the current experimental setup was 4.14*10 -6 sec-1, which is six-fold more than the minimum required rate constant. This proves that the procedure used for removal of oxygen is an efficient one. The models also confirmed that NASA could select any material for a unit-package provided there is an adequate control of oxygen and moisture at the overwrap level. Therefore, the current project has identified and evaluated the mathematical and analytical approaches to validate the proposed solution.
Degree
M.S.
Advisors
Morgan, Purdue University.
Subject Area
Agronomy|Industrial engineering
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