Migration of electrode components during ohmic heating of foods in retort pouches

Abstract

During space missions, life support technologies must satisfy mission constraints, including maximizing safety and acceptability of food and minimizing crew time, storage volume, power, water usage, and maintenance down-time. Ohmic heating appears to be a feasible potential solution to meet food reheating and waste sterilization requirements; however, it is necessary to verify if electrochemical reactions such as gas generation and electrode corrosion occur. A pulsed ohmic heating system and reusable pouch were tested to ensure the food safety and quality by minimizing the undesired electrochemical reactions. Results of gas generation during ohmic heating show that stainless steel is far superior to aluminum since there were no noticeable gas bubbles even at the temperature of 70 °C. A study of migration of the major key metal ions from stainless steel, such as Fe, Cr, Ni, Mn, and Mo, measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) shows that pulsed ohmic heating produced comparable or lower migration of most targeted metal ions, compared to the conventional retorting when electrodes were present. The intakes of individual metal contaminants evaluated with respect to a typical meal (8 oz) after ohmic treatment were, as a maximum, 13.5% of recently published upper-level daily dietary exposure estimates. Consequently, pouches with stainless steel electrodes powered by a pulsed ohmic heater shows promise as a potential reheating and sterilization technology for space missions. Ohmic heating has been used for many years in different industries and proved to be a promising food processing technology due to its rapid, yet uniform and high energy efficient heating capability. This paper demonstrates the potential of direct ohmic heating for foods in retort pouches at the household level as well as the mass production level, ensuring food safety by suppressing the metal ions migration far less than the dietary exposure estimates.